U.S. patent application number 10/296010 was filed with the patent office on 2004-04-22 for combined impedance imaging and mammography.
Invention is credited to Malonek, Dov, Nachaliel, Ehud, Steinberg, Sebastian, Wimisner, Yoav.
Application Number | 20040077944 10/296010 |
Document ID | / |
Family ID | 11042976 |
Filed Date | 2004-04-22 |
United States Patent
Application |
20040077944 |
Kind Code |
A1 |
Steinberg, Sebastian ; et
al. |
April 22, 2004 |
Combined impedance imaging and mammography
Abstract
A probe for impedance imaging comprising: a plurality of
conductive elements adapted to contact tissue of a subject; a
plurality of conductive wires connecting the conductive elements to
an external connector, and one or more non-conductive materials,
wherein the x-ray absorbance of the non-conductive materials, in at
least some of the surface areas of the probe, is a function of the
x-ray absorbance of the conductive wires and elements in the same
surface area, such that the probe has substantially the same x-ray
absorbance over most of the surface area of the probe.
Inventors: |
Steinberg, Sebastian;
(Kiryat-Bialik, IL) ; Wimisner, Yoav;
(Zichron-Yaakov, IL) ; Nachaliel, Ehud;
(Lower-Galilee, IL) ; Malonek, Dov; (Kiryat-Tivon,
IL) |
Correspondence
Address: |
William H Dippert
Reed Smith
29th Floor
599 Lexington Avenue
New York
NY
10022-7650
US
|
Family ID: |
11042976 |
Appl. No.: |
10/296010 |
Filed: |
May 15, 2003 |
PCT Filed: |
April 18, 2001 |
PCT NO: |
PCT/IL01/00359 |
Current U.S.
Class: |
600/436 ;
600/547 |
Current CPC
Class: |
A61B 2562/17 20170801;
A61B 6/0414 20130101; A61B 6/5235 20130101; A61K 51/00 20130101;
A61B 2562/0215 20170801; A61B 6/4423 20130101; A61B 5/0035
20130101; A61K 49/0433 20130101; A61B 5/0536 20130101; A61B 6/4258
20130101; A61B 6/5247 20130101; A61B 6/037 20130101; A61B 6/502
20130101; A61B 2562/046 20130101 |
Class at
Publication: |
600/436 ;
600/547 |
International
Class: |
A61B 006/00; A61B
005/05 |
Foreign Application Data
Date |
Code |
Application Number |
May 21, 2000 |
WO |
PCT/IL00/00287 |
Dec 14, 2000 |
WO |
PCT/IL00/00839 |
Claims
1. A probe for impedance imaging comprising: a plurality of
conductive elements adapted to contact tissue of a subject; a
plurality of conductive wires connecting the conductive elements to
an external connector; and one or more non-conductive materials,
wherein the x-ray absorbance of the non-conductive materials, in at
least some of the surface areas of the probe, is a function of the
x-ray absorbance of the conductive wires and elements in the same
surface area, such that the probe has substantially the same x-ray
absorbance over most of the surface area of the probe.
2. A probe according to claim 1, wherein the one or more
non-conductive materials comprise a substrate layer having
different thickness at different surface areas of the probe.
3. A probe according to claim 2, wherein the substrate layer is
thinner in surface areas of the probe which include conductive
wires.
4. A probe according to claim 1, wherein the one or more
non-conductive materials comprise at least one isolating material
which has an x-ray absorbency substantially equal to the x-ray
absorbency of the conductive elements or of the conductive
wires.
5. A probe according to claim 4, wherein the plurality of
conductive elements comprise an aluminum-based deposit and the at
least one isolating material comprises alumina.
6. A probe according to claim 1, wherein the one or more
non-conductive materials comprise at least one isolating material
which is deposited between at least some of the conductive
elements.
7. A probe according to claim 1, wherein the x-ray absorption level
of at least some of the surface areas including the conductive
elements is substantially equal to the absorption level of at least
some of the surface areas not including the conductive
elements.
8. A probe according to any of the preceding claims, wherein the
plurality of lead wires are included in a single layer which has a
substantially equal x-ray absorption level over substantially its
entire surface area.
9. A probe according to any of the preceding claims, wherein the
probe does not include conductive portions which are not included
in an electrical path between one of the conductive elements and
the external connector.
10. A probe according to any of the preceding claims, wherein the
probe has an x-ray absorption level of less than 6%.
11. A probe for impedance imaging comprising: a tissue contact
layer which includes a plurality of conductive elements adapted to
contact tissue of a subject; one or more wire layers which include
a plurality of conductive wires connecting the conductive elements
to at least one external connector; and a substrate layer, wherein
at least one of the tissue contact layer or the wire layers has
less than 2% variations in its x-ray absorbance over a surface area
including a plurality of the conductive elements.
12. A probe according to claim 11, wherein at least one of the
tissue contact layer or the wire layers has less than 2% variations
in its x-ray absorbance over most of the surface area of the
probe.
13. A probe according to claim 11, wherein at least one of the
tissue contact layer or the wire layers has less than 0.25%
variations in its x-ray absorbance over a surface area including a
plurality of the conductive elements.
14. A probe according to any of claims 11-13, wherein the layer
with less than 2% variations in its x-ray absorbance comprises the
tissue contact layer.
15. A probe according to claim 14, wherein the tissue contact layer
comprises an isolation material between at least some of the
conductive elements.
16. A probe according to claim 15, wherein the isolation material
in the tissue contact layer has substantially the same thickness as
the conductive elements.
17. A probe according to claim 15 or claim 16, wherein the
isolation material has substantially the same x-ray absorbancy as a
material forming the conductive elements.
18. A probe according to claim 17, wherein the isolation material
comprises alumina and the material forming the conductive elements
comprises aluminum.
19. A probe according to claim 17, wherein the isolation material
comprises carbon and the material forming the conductive elements
comprises a carbon based plastic.
20. A probe according to claim 15, wherein the isolation material
in the tissue contact layer has a different thickness than the
conductive elements.
21. A probe according to claim 15 or claim 20, wherein the
isolation material has a different x-ray absorbancy than a material
forming the conductive elements.
22. A probe according to any of claims 11-21, wherein the layer
with less than 2% variations in its x-ray absorbance comprises the
wire layer.
23. A probe according to claim 22, wherein the wires in the wire
layer are separated by an isolation material having substantially
the same x-ray absorbancy as a material forming the wires.
24. A breast impedance imaging apparatus, comprising: a first
multi-element impedance imaging probe, adapted for placing on a
first side of a breast; and a second multi-element impedance
imaging probe, having a different structure than the first
impedance imaging probe, adapted for placing on a second side of
the breast.
25. Apparatus according to claim 24, comprising a mammogram
including an x-ray source and an image receptor adapted for taking
images of the breast.
26. Apparatus according to claim 25, wherein the mammogram is
adapted to generate images based on x-ray signals which pass
through at least one of the first and second probes.
27. Apparatus according to any of claims 24-26, wherein the first
and second probes have different numbers of elements.
28. Apparatus according to any of claims 24-27, wherein the first
and second probes have elements of different sizes.
29. Apparatus according to any of claims 24-26, wherein the first
and second probes have the same number of elements.
30. Apparatus according to claim 29, wherein the first and second
probes have the same arrangement of elements.
31. Apparatus according to any of claims 24-30, wherein the first
and second probes have different average x-ray absorption
levels.
32. Apparatus according to any of claims 24-31, wherein the first
and second probes have different maximal differences between x-ray
absorption levels of different areas of the probe.
33. Apparatus according to any of claims 24-32, wherein the first
and second probes comprise different materials.
34. Apparatus according to any of claims 24-33, wherein the first
probe comprises a single piece and the second probe comprises a
plurality of detachable pieces.
35. A breast impedance imaging apparatus, comprising: a mammogram
including an x-ray source and an image receptor adapted for taking
images of a breast; a first, multi-element, impedance imaging
probe, adapted for placing on a first side of a breast; and a
second impedance imaging probe, having a different structure than
the first impedance imaging probe, adapted for placing on a second
side of the breast.
36. Apparatus according to claim 35, wherein the second probe
comprises a single element probe.
37. Apparatus according to claim 36 wherein the impedance imaging
apparatus comprises a structure according to any of claims
24-34.
38. A method of imaging a body portion of a subject, comprising:
acquiring an x-ray image of the body portion; determining at least
one impedance imaging parameter responsive to the acquired x-ray
image; and acquiring an impedance image of the body portion using
the determined at least one imaging parameter.
39. A method according to claim 38, wherein determining the at
least one parameter comprises determining at least one parameter of
an applied stimulation signal.
40. A method according to claim 38 or claim 39, wherein determining
the at least one parameter comprises determining an area to be
imaged.
41. A method according to any of claims 38-40, wherein determining
the at least one parameter comprises determining a position of a
suspected anomaly.
42. A method of imaging a body portion of a subject, comprising:
acquiring impedance image information of the body portion;
acquiring x-ray image information of the body portion; and
analyzing a first one of the impedance image information and x-ray
image information; and displaying at least one image based on
information selected, from a second one of the impedance image
information and x-ray image information, responsive to the
analyzing.
43. A method according to claim 42, wherein analyzing the first one
of the impedance image information and x-ray image information
comprises analyzing the x-ray information.
44. A method according to claim 42 or claim 43, wherein analyzing
the information comprises determining a location of an anomaly.
45. A method according to any of claims 42-44, wherein analyzing
the information comprises determining an impedance measure to be
displayed.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to medical imaging
techniques. In particular the present invention relates to
performing impedance imaging in conjunction with mammography.
BACKGROUND OF THE INVENTION
[0002] Early detection of cancerous tumors increases the chances of
success in curing breast cancer. Several methods are known to
screen the breast in order detect suspicious tumors. Two of these
methods are X-ray mammography and impedance imaging, described, for
example, in U.S. Pat. No. 4,291,708 to Frei and in U.S. Pat. No.
5,810,742 to Pearlman, the disclosures of which are incorporated
herein by reference. In impedance imaging, a multi-element
impedance probe is placed on a breast of a patient and one or more
electrodes apply electrical signals to the subject. Each of the
elements of the probe senses electrical signals from the breast and
accordingly an image of the breast is generated. The multi-element
probe comprises a plurality of conductive elements.
[0003] U.S. Pat. No. 6,157,697, the disclosure of which is
incorporated herein by reference, describes the use of an appartus
for examining a breast by means of X-rays and by electric impedance
measurement. The apparatus can be used to generate both X-ray and
impedance images of the breast. A fusion image may be formed from a
combination of the images. In order to allow easy comparison and
fusion of the images, the images are taken during a single session
while the breast is in the same position, and from substantially
the same direction. That is, the X-ray images are taken while
electrodes used for generating an impedance image are positioned on
the breast.
[0004] The '697 patent suggests using an impedance imaging probe
which is formed of three layers. A first layer comprises a
plurality of electrodes and lead wires, which electrodes are used
in the impedance imaging. Although the electrodes are suggested as
comprising a material which attenuates X-ray poorly, the difference
between the X-ray intensity passing through the electrodes and the
intensity passing through areas between the electrodes may cause
artifacts on the x-ray images taken while the impedance probe is in
place. Therefore, the '697 patent suggests using a second layer,
separated from the electrodes by an insulation (third) layer, which
comprises the electrode materials in a mirror image to the first
layer. The additional layer is not used in any way for the
impedance imaging and is provided in order to prevent formation of
shadow artifacts on the x-ray images.
SUMMARY OF THE INVENTION
[0005] An aspect of some embodiments of the present invention
relates to a multi-element impedance probe which includes
conductive materials in one or more layers. At least one of the
layers includes an isolating material, which has an x-ray
absorption level substantially equal to that of the conductive
materials, between the conductive materials of the layer. The
isolating material is optionally included throughout an imaging
region of the probe. In some embodiments of the invention, the
isolating material has substantially the same x-ray absorbency as
the conductive material of the same layer. Alternatively, the
isolating material of a layer has a different thickness than the
conductive material of the layer, such that the x-ray absorption of
the conductive and isolating materials of the layer is
substantially equal. Further alternatively, the isolating material
comprises a mixture of materials which has substantially the same
x-ray absorption as the conductive material.
[0006] In some embodiments of the invention, the impedance probe
includes a plurality of layers including, for example, a body
contact layer, one or more wire leading layers, a substrate layer
and one or more isolating layers. It is noted that the wire leading
layers and body contact layer include both conductive materials and
the isolating materials between them. In some embodiments of the
invention, the conductive and non-conductive materials of a single
layer have substantially the same height. In other embodiments of
the invention, the substantive conductive and non-conductive
materials of a single layer have different heights. The difference
in the heights may be left empty (e.g., in the body contact layer),
or may be filled in with low x-ray absorbent materials (e.g., low
x-ray absorbency plastics) for example of an adjacent isolating
layer. Optionally, each of the layers has substantially the same
x-ray absorption over its entire surface area within the imaging
region. Having each of the layers of the multi-element probe have
equal absorption levels over the surface area included in the
imaging region prevents formation of artifacts in images taken in
an angle relative to the impedance probe. In addition, using an
isolating material for equalizing the x-ray absorption level of the
layers, allows simple use of a plurality of conductive layers in a
single probe.
[0007] An aspect of some embodiments of the invention relates to a
multi-element impedance probe in which the x-ray absorption level
of the non-conductive layers of surface regions of the probe are a
function of the x-ray absorption level of the conductive layers of
the surface regions. In some embodiments of the invention,
different surface regions of the probe have substantially different
x-ray absorption levels of their non-conductive layers. Optionally,
the probe has a substantially equal x-ray absorption level,
substantially over its entire imaging region. Optionally, the probe
does not include non-functional conductive portions.
[0008] In some embodiments of the invention, the conductive
elements of the impedance probe and the insulation separating the
elements are formed of materials which have similar x-ray
absorbency. Optionally, the materials are substantially x-ray
transparent materials, which have a very low X-ray absorbency. In
an exemplary embodiment of the invention, the conductive elements
comprise aluminum and the insulation comprises Alumina (i.e.,
Al.sub.2O.sub.3) and/or silicone.
[0009] Alternatively or additionally, the thickness of the probe at
different areas is varied according to the X-ray attenuation of the
materials in each specific surface area. Optionally, the conductive
elements are held by a substrate which has a variable thickness
according to the size and shape of the conductive elements.
[0010] An aspect of some embodiments of the invention relates to an
impedance imaging probe which has conductive portions with
dimensions substantially smaller than the resolution of x-rays
passing through the probe. The x-ray absorbence of conductive
portions which cover less than the resolution limit of the x-ray
detector reduces with the percentage of the area of the pixel
covered by the conductive portions.
[0011] In some embodiments of the invention, an impedance probe
comprises a conductive element layer and a lead wire layer. Lead
wires from the lead wire layer are optionally connected to
respective conductive elements with vias having a cross-section
substantially smaller than the resolution of x-ray imaging
techniques.
[0012] An aspect of some embodiments of the invention relates to a
combined X-ray mammography and impedance system in which the
compression and support plates comprise respective multi-element
impedance probes. Optionally, the probes have the same
two-dimensional arrangement of elements but have different physical
structures.
[0013] In some embodiments of the invention, one of the probes
comprises a two piece structure including a disposable contact
layer and a reusable connector unit, while the other probe
comprises a single integral unit. Alternatively or additionally,
one of the probes comprises thinner leads, to the conductive
elements, than the other.
[0014] Optionally, the probe associated with the support plate,
i.e., closer to the x-ray detectors of the mammograph, is less
X-ray absorbent than the probe of the upper compression plate, as
X-ray energy absorbed by the support plate already passed through
the breast. Alternatively or additionally, the probe associated
with the lower support plate is more uniform in its x-ray
absorption over its surface. Generally, differences in the x-ray
absorption of the probe associated with the upper compression plate
cause less severe artifacts in the x-ray images because the x-rays
from the upper compression plate pass through the breast where they
are anyhow scattered.
[0015] An aspect of some embodiments of the invention relates to an
impedance imaging system including a pair of multi-element probes,
each having a plurality of separate conductive elements, which have
different numbers and/or sizes of conductive elements. The probes
are optionally adapted for placement on opposite sides of an
organ.
[0016] An aspect of some embodiments of the invention relates to a
multiple modality examination procedure, including impedance and
x-ray imaging, in which results from one modality are used in
setting one or more parameters of another modality.
[0017] In some embodiments of the invention, the results of a first
modality and/or combined results of a plurality of modalities are
used to determine whether an anomaly is existent within the breast
and/or the location of the anomaly. According to the location of
the anomaly, one or more parameters of an examination procedure of
a second modality are adjusted, in order to determine the type of
the anomaly, i.e., whether the anomaly is malignant. Optionally,
the second modality comprises impedance imaging. In some
embodiments of the invention, the one or more adjusted parameters
comprise the specific locations from which electrification signals
are applied to the subject, and/or the amplitudes, frequencies
and/or phases of the electrification signals. Alternatively or
additionally, the one or more adjusted parameters comprise
constants of a calculation procedure used to generate the
images.
[0018] In some embodiments of the invention, the parameter
adjustment is performed by a human operator. Alternatively or
additionally, the parameter adjustment is performed automatically,
e.g., by a control processor.
[0019] Alternatively or additionally, the results of a first
modality and/or combined results of a plurality of modalities are
used to determine whether an anomaly is existent within the breast
and/or the two-dimensional location of the anomaly, while the
second modality is used to determine the depth of the anomaly
beneath the probe.
[0020] In some embodiments of the invention, the second modality
comprises X-ray imaging and the one or more parameters comprise the
volt peak (KVP), X-ray voltage, x-ray current and/or mAs product of
the X-ray source.
[0021] An aspect of some embodiments of the invention relates to a
multiple modality examination procedure, including impedance and
x-ray imaging, in which the analysis and/or display of results from
one modality depends on the results from another modality.
[0022] In some embodiments of the invention, the type of the
parameter of the impedance imaging which is displayed (e.g.,
critical frequency, phase, capacitance, conductivity) is selected
responsive to results from the imaging of another modality.
Alternatively or additionally, during the impedance imaging, data
is collected for a plurality of stimulation signals and the data
displayed is chosen responsive to the imaging results from another
modality.
[0023] There is thus provided, in accordance with an exemplary
embodiment of the invention a probe for impedance imaging
comprising:
[0024] a plurality of conductive elements adapted to contact tissue
of a subject;
[0025] a plurality of conductive wires connecting the conductive
elements to an external connector; and
[0026] one or more non-conductive materials,
[0027] wherein the x-ray absorbance of the non-conductive
materials, in at least some of the surface areas of the probe, is a
function of the x-ray absorbance of the conductive wires and
elements in the same surface area, such that the probe has
substantially the same x-ray absorbance over most of the surface
area of the probe.
[0028] In an embodiment of the invention, the one or more
non-conductive materials comprise a substrate layer having
different thickness at different surface areas of the probe.
Optionally, the substrate layer is thinner in surface areas of the
probe which include conductive wires.
[0029] In an embodiment of the invention, the one or more
non-conductive materials comprise at least one isolating material
which has an x-ray absorbency substantially equal to the x-ray
absorbency of the conductive elements or of the conductive wires.
Optionally, the plurality of conductive elements comprise an
aluminum-based deposit and the at least one isolating material
comprises alumina.
[0030] In an embodiment of the invention, the one or more
non-conductive materials comprise at least one isolating material
which is deposited between at least some of the conductive
elements.
[0031] In an embodiment of the invention, the x-ray absorption
level of at least some of the surface areas including the
conductive elements is substantially equal to the absorption level
of at least some of the surface areas not including the conductive
elements.
[0032] Optionally, the plurality of lead wires are included in a
single layer which has a substantially equal x-ray absorption level
over substantially its entire surface area.
[0033] Optionally, the probe does not include conductive portions
which are not included in an electrical path between one of the
conductive elements and the external connector.
[0034] Optionally, the probe has an x-ray absorption level of less
than 6%.
[0035] There is further provided in accordance with an embodiment
of the invention, a probe for impedance imaging comprising:
[0036] a tissue contact layer which includes a plurality of
conductive elements adapted to contact tissue of a subject;
[0037] one or more wire layers which include a plurality of
conductive wires connecting the conductive elements to at least one
external connector; and
[0038] a substrate layer,
[0039] wherein at least one of the tissue contact layer or the wire
layers has less than 2% variations in its x-ray absorbance over a
surface area including a plurality of the conductive elements.
[0040] Optionally, at least one of the tissue contact layer or the
wire layers has less than 2% variations in its x-ray absorbance
over most of the surface area of the probe.
[0041] Optionally, at least one of the tissue contact layer or the
wire layers has less than 0.25% variations in its x-ray absorbance
over a surface area including a plurality of the conductive
elements.
[0042] Optionally, the layer with less than 2% variations in its
x-ray absorbance comprises the tissue contact layer. Optionally,
the tissue contact layer comprises an isolation material between at
least some of the conductive elements. Optionally, the isolation
material in the tissue contact layer has substantially the same
thickness as the conductive elements. Optionally, the isolation
material has substantially the same x-ray absorbancy as a material
forming the conductive elements. Optionally, the isolation material
comprises alumina and the material forming the conductive elements
comprises aluminum. Optionally, the isolation material comprises
carbon and the material forming the conductive elements comprises a
carbon based plastic.
[0043] In an embodiment of the invention, the isolation material in
the tissue contact layer has a different thickness than the
conductive elements.
[0044] In an embodiment of the invention, the isolation material
has a different x-ray absorbancy than a material forming the
conductive elements.
[0045] Optionally, the layer with less than 2% variations in its
x-ray absorbance comprises the wire layer. Optionally, the wires in
the wire layer are separated by an isolation material having
substantially the same x-ray absorbancy as a material forming the
wires.
[0046] there is further provided, in accordance with an embodiment
of the invention, a breast impedance imaging apparatus,
comprising:
[0047] a first multi-element impedance imaging probe, adapted for
placing on a first side of a breast; and
[0048] a second multi-element impedance imaging probe, having a
different structure than the first impedance imaging probe, adapted
for placing on a second side of the breast.
[0049] Optionally, the apparatus includes a mammogram including an
x-ray source and an image receptor adapted for taking images of the
breast. Optionally, the mammogram is adapted to generate images
based on x-ray signals which pass through at least one of the first
and second probes. Optionally, the first and second probes have
different numbers of elements. Optionally, the first and second
probes have elements of different sizes. Optionally, the first and
second probes have the same number of elements. Optionally, the
first and second probes have the same arrangement of elements.
Optionally, the first and second probes have different average
x-ray absorption levels. Optionally, the first and second probes
have different maximal differences between x-ray absorption levels
of different areas of the probe. Optionally, the first and second
probes comprise different materials. Optionally, the first probe
comprises a single piece and the second probe comprises a plurality
of detachable pieces.
[0050] There is further provided, in accordance with an embodiment
of the invention, a breast impedance imaging apparatus,
comprising:
[0051] a mammogram including an x-ray source and an image receptor
adapted for taking images of a breast;
[0052] a first, multi-element, impedance imaging probe, adapted for
placing on a first side of a breast; and
[0053] a second impedance imaging probe, having a different
structure than the first impedance imaging probe, adapted
for-placing on a second side of the breast.
[0054] Optionally, the second probe comprises a single element
probe. Alternatively, the impedance imaging apparatus comprises a
structure according to an embodiment of the invention.
[0055] There is further provided, in accordance with an embodiment
of the invention, a method of imaging a body portion of a subject,
comprising:
[0056] acquiring an x-ray image of the body portion;
[0057] determining at least one impedance imaging parameter
responsive to the acquired x-ray image; and
[0058] acquiring an impedance image of the body portion using the
determined at least one imaging parameter.
[0059] In an embodiment of the invention, determining the at least
one parameter comprises determining at least one parameter of an
applied stimulation signal.
[0060] Optionally, determining the at least one parameter comprises
determining an area to be imaged. Alternatively or additionally,
determining the at least one parameter optionally comprises
determining a position of a suspected anomaly.
[0061] There is further provided, in accordance with an embodiment
of the invention, a method of imaging a body portion of a subject,
comprising:
[0062] acquiring impedance image information of the body
portion;
[0063] acquiring x-ray image information of the body portion;
and
[0064] analyzing a first one of the impedance image information and
x-ray image information; and
[0065] displaying at least one image based on information selected,
from a second one of the impedance image information and x-ray
image information, responsive to the analyzing.
[0066] In an embodiment of the invention, analyzing the first one
of the impedance image information and x-ray image information
comprises analyzing the x-ray information. Alternatively or
additionally, analyzing the information optionally comprises
determining a location of an anomaly. Alternatively or
additionally, analyzing the information optionally comprises
determining an impedance measure to be displayed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0067] Exemplary non-limiting embodiments of the invention will be
described with reference to the following description of
embodiments in conjunction with the figures. Identical structures,
elements or parts which appear in more than one figure are
preferably labeled with a same or similar number in all the figures
in which they appear, in which:
[0068] FIG. 1 is a schematic illustration of a dual-purpose
apparatus for mammography and impedance-imaging, in accordance with
an embodiment of the present invention;
[0069] FIG. 2 is a schematic illustration of an impedance probe and
a probe housing, in accordance with an embodiment of the present
invention;
[0070] FIGS. 3A and 3B are schematic views of the impedance probe
of FIG. 2, in accordance with an embodiment of the present
invention;
[0071] FIG. 4 is a schematic cross-section view of a portion of an
impedance probe, in accordance with an embodiment of the present
invention; and
[0072] FIG. 5 is a flowchart of the acts performed in a dual
modality imaging procedure, in accordance with an embodiment of the
present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0073] FIG. 1 is a schematic illustration of a dual-purpose
apparatus 30 for mammography and impedance-imaging, in accordance
with an embodiment of the present invention. Dual-purpose apparatus
30 comprises an x-ray mammogram of any type known in the art, of
which FIG. 1 shows an x-ray tube 14, an image receptor 18 (which
may be analog or digital), filters 16, a collimator 12 and an
anti-scattering grid 19. In addition, FIG. 1 shows a compression
plate 20 and a support plate 22 which are adapted to receive an
examined breast 33. For example, the mammogram may comprise a
LORAD.RTM. M-IV mammogram (manufactured by LORAD, a subsidiary of
Trex Medical Corporation, Danbury, Conn.) which includes a cellular
grid system for contrast and visual enhancement. Alternatively or
additionally, the mammogram may have stereoscopic capability for
obtaining x-ray images from at least two viewing angles. The
mammogram may be upright for use with sitting or standing patients.
Optionally, the mammogram can be rotated along the horizontal axis
so as to obtain x-ray measurements at any angle. Alternatively, the
mammogram may have fewer degrees of freedom. Further alternatively,
the mammogram is horizontal for use with prone patients. It should
be noted that in general, any mammogram may be fitted in accordance
with the present invention, including mammograms designed and/or
manufactured without intention to be used in accordance with the
present invention.
[0074] One or more multi-element impedance probes (in FIG. 1,
probes 40 and 42) for sensing impedance signals, and/or for
applying signals, are placed on breast 33. An electrode 56 for
applying electrical stimulation signals is positioned on a surface
of the subject whose breast 33 is examined. Optionally, electrode
56 is placed remote from the breast or otherwise not in the path of
the x-ray beams from x-ray tube 14. Alternatively, electrode 56 is
placed on the breast, for example on the nipple. Optionally,
electrode 56 comprises x-ray translucent materials, for example, a
single thin aluminum electrode. Alternatively, electrode 56
comprises a multi-element probe, for example having a similar
structure and/or according to the principles described above with
relation to probe 40.
[0075] Optionally, a computer 24 receives the sensed signals from
probe 40, from probe 42 and/or from image receptor 18 (when a
digital x-ray detector is used, for example), and provides an
indication of the state of breast 33. For example, computer 24 may
display an image of breast 33 on a monitor 26.
[0076] In some embodiments of the invention, apparatus 30 comprises
an electrical impedance scanning device 58 which controls the
sensing of the impedance signals and the applying of
electrification signals to the patient. Scanning device 58 may be
substantially any suitable electrical impedance scanning device
known in the art, for example, a T-Scan.TM. 2000 Impedance Scanner
of TransScan, Israel, or as described in U.S. Pat. Nos. 5,810,742,
4,458,694, PCT application PCT/IL00/00127, filed Mar. 1, 2000, PCT
application PCT/IL00/00839, filed Dec. 14, 2000 and/or U.S. patent
application Ser. No. 09/460,699, filed Dec. 14, 1999, the
disclosures of which documents are incorporated herein by
reference. Alternatively or additionally, some or all of the tasks
of scanning device 58 are performed by computer 24.
[0077] In some embodiments of the invention, each of the elements
of probes 40 and/or 42 is controlled separately such that at any
single moment some of the elements may sense signals, others may
provide excitation (optionally at different phases, frequencies or
amplitudes), and still others may be passive. Alternatively or
additionally, the elements of one or more of probes 40 and 42 are
controlled in groups, for example in lines or circles including a
plurality of elements. Further alternatively or additionally, the
control of the elements of probes 40 and 42 is as described in any
of the above referenced patent documents.
[0078] In some embodiments of the invention, apparatus 30 comprises
only a single probe (e.g., 40), which is attached to compression
plate 20. By placing probe 40 within the path of x-rays used in
x-ray imaging of the breast, the images generated by probe 40 cover
substantially the same area as the images acquired by receptor 18.
When impedance probe 40 is located between X-ray tube 14 and breast
33, X-rays absorbed by probe 40 which therefore do not participate
in generating an X-ray image by receptor 18, do not impinge on
breast 33. Thus, probe 40 may have a certain degree of uniform
x-ray absorption without adversely affecting the x-ray image or the
amount of x-rays absorbed by breast 33. The x-ray intensity of the
beams generated by head 14 may be adjusted responsive to the x-ray
absorption of probe 40.
[0079] In other embodiments of the invention, apparatus 30
comprises a pair of probes 40 and 42 attached, respectively, to
compression plate 20 and support plate 22. As described, for
example, in the above mentioned U.S. Pat. No. 5,810,742 and/or in
PCT/IL00/00839, a pair of impedance probes 40 and 42 can be used in
a multitude of impedance imaging procedures which provide
additional information on anomalies within breast 33, such as its
location (e.g., depth) and/or type. Alternatively, apparatus 30
comprises only probe 42, which is attached to support plate 22.
[0080] In some embodiments of the invention, probes 40 and/or 42
are permanently affixed to compression plate 20 and/or support
plate 22. Alternatively or additionally, impedance probe 40 serves
as compression plate 20 and/or probe 42 serves as support plate 22.
Optionally in this alternative, impedance probes 40 and/or 42 are
strengthened with a stiff plastic board, or another, preferably
radiolucent, stiff material.
[0081] Alternatively or additionally, impedance probes 40 and/or 42
are detachably attached to a breast side of compression plate 20
and/or of support plate 22. Having probes 40 and/or 42 detachably
connected to plates 20 and/or 22, respectively, allows performing
imaging sessions with only x-rays or with only a single impedance
probe 40 or 42. For example, in some cases, in order to reduce
x-ray exposure, only impedance probe 40 or 42 is used. In other
cases, when a high precision level is required, both impedance
probes 40 and 42 are used. In addition, having probes 40 and/or 42
detachably connected to plates 20 and/or 22, respectively, allows
replacement of probes 40 and/or 42 for each patient.
[0082] Impedance probes 40 and/or 42 may be affixed to their
respective plates using any suitable method, such as
tongue-in-grove, male-female snaps, screws, nuts and bolts,
adhesives or Velcro fasteners, and/or any of the methods described
in PCT/IL00/00287, the disclosure of which is incorporated herein
by reference. It is noted that probes 40 and/or 42 may have the
same size as the plates to which they are connected or may have
different sizes than the plates.
[0083] FIG. 2 is a schematic illustration of an impedance probe 40
and a probe housing 200, in accordance with an embodiment of the
present invention. Probe housing 200 receives probe 40, providing
mechanical support and/or electrical connection. Optionally, probe
40 is disposable, while housing 200 is used for many patients.
Probe housing 200 may be connected to support plate 20 using any of
the above described methods.
[0084] In some embodiments of the invention, impedance probe 40 and
compression plate 20 are aligned in a precise and repeatable
alignment which allows simple registration of images acquired by
probe 40 with images acquired by receptor 18. In those embodiments
in which impedance probe 40 is removable, the precise and
repeatable alignment is optionally defined by a groove designed to
receive the probe, e.g., probe housing 200, and/or the positions of
the attachment devices. Alternatively or additionally, human
identifiable markings, for example felt-tip markings, instructing
an operator how to align compression plate 20 and probe 40 are
marked on the plate and/or probe.
[0085] Alternatively or additionally, registration of the images
produced by impedance probe 40 with the X-ray images, is performed
each time probe 40 and plate 20 are connected and/or for each
imaging procedure. In some embodiments of the invention, probe 40
comprises x-ray absorbing markings, which appear in x-ray images
acquired by x-ray receptor 18, deposited thereon at predetermined
positions. Optionally, the x-ray absorbing markings are not located
above sensing elements of probe 40 and/or are outside the region of
interest of most images. Alternatively, the absorbing markings are
located on probe housing 200 or on any other device having a
predetermined spatial relation with probe 40. Further
alternatively, the x-ray absorbing markings are removably attached
to impedance probe 40. When alignment is required they are put in
place and when x-ray images are acquired they are removed.
Alternatively or additionally, the imprints of the x-ray absorbing
markings are removed from impedance images by image processing
methods. Optionally, the absorbing markings identify the
orientation of impedance probe 40, for example using a "right"
and/or "left" marking.
[0086] Optionally, the absorbing markings comprise a material that
is sufficiently absorbing to show on the x-ray image, but not so
absorbing that it can cause serious artifacts, for example a thick
layer of aluminum or a thin layer of platinum or gold. In some
embodiments of the invention, the absorbing markings comprise at
least two perpendicular lines which define at least one junction,
optionally two junctions. In some embodiments of the invention, the
absorbing markings are visible to humans. Alternatively or
additionally, the location of the absorbing markings on impedance
probe 40 are known by computer 24, and registration is performed
accordingly.
[0087] It is noted that any of the above described attachment
methods of probe 40 and compression plate 20, may be used to attach
probe 42 and support plate 22.
[0088] FIG. 3A is a schematic top view of impedance probe 40 shown
in FIG. 2, in accordance with an embodiment of the present
invention. FIG. 3A also shows lead wires 504 beneath one row of
pads 500. The remaining lead wires are not shown, so as not to
clutter FIG. 3A. FIG. 3B is a side cross-sectional view of the
impedance probe 40 of FIG. 3A. Probe 40 comprises a plurality of
electrode pads 500, for example arranged in a two dimensional
array. As shown, probe 40 comprises an 8.times.8 array of pads 500.
It is noted, however, that the present invention may be implemented
with substantially any number of pads 500, in substantially any
useful arrangement. In an exemplary embodiment of the invention,
probe 40 comprises 45.times.60 pads 500, each pad having a square
area of about 4.times.4 mm.
[0089] In some embodiments of the invention, electrode pads 500 are
isolated from each other by isolating strips 502. Optionally,
isolating strips 502 are as narrow as possible, such that most of
the area of the top surface of probe 40 is uniform and does not
cause artifacts in x-ray images acquired by receptor 18.
Alternatively or additionally, isolating strips 502 have a width
selected as a compromise between the desire to minimize artifacts
on the x-ray images, and the need to minimize cross talk between
the electrical signals of pads 500. In an exemplary embodiment of
the invention, the width of insulation strips 502 is about 0.2 mm.
A layer including pads 500 and isolating strips 502 is referred to
herein as a contact layer 516.
[0090] Beneath electrode pads 500, probe 40 comprises, for each pad
500, a lead wire 504 which connects the pad to an external
connector 506 which leads signals from pads 500 to scanning device
58 (FIG. 1). In some embodiments of the invention, external
connector 506 is included in probe housing 200 (FIG. 2). An
isolating layer 508 separates pads 500 from lead wires 504. In some
embodiments of the invention, isolating strips 520 separate between
lead wires 504. Respective vias 510 within isolating layer 508
connect each of pads 500 to its respective lead wire 504.
Optionally, a substrate layer 512 beneath lead wires 504 provides
probe 40 with durability and/or isolates lead wires 504 from the
surroundings.
[0091] In some embodiments of the invention, electrode pads 500 and
isolating strips 502 comprise materials which have substantially
the same substance X-ray absorbency. Generally, the substance x-ray
absorbency is a function of the atomic number Z of the material.
Thus, shadows are not formed on X-ray images acquired by receptor
18, due to a difference between the X-ray absorption of different
areas of probe 40.
[0092] In an exemplary embodiment of the invention, electrode pads
500 comprise aluminum (for example 0.1-0.2 .mu.m) and isolating
strips 502 comprise alumina and/or silicone. Optionally, electrode
pads 500 have a very thin carbon layer (e.g., 0.1 .mu.m) on the
surface which contacts the breast. In some embodiments of the
invention, isolating strips 502 include, in addition to the
alumina, a respective thin layer of a plastic with similar x-ray
absorbency to that of the carbon so as to compensate for the
carbon. Alternatively, isolating strips 502 include only alumina,
as the carbon layer is very thin. Alternatively to electrode pads
500 including aluminum, electrode pads 500 comprise a carbon, e.g.,
amorphous carbon, and isolating strips 502 comprise a plastic
material with similar x-ray absorbency, e.g., polyester. In an
exemplary embodiment of the invention, pads 500 comprise thin
carbon layers of between about 0.1-20 .mu.m.
[0093] Alternatively to having the same x-ray absorbency, isolating
strips 502 have a thickness which compensates for the different
x-ray absorbencies, such that electrode pads 500 and isolating
strips 502 have the same absorption level.
[0094] Alternatively, the gaps between electrode pads 500 are not
filled in, and other methods, such as described below, are used to
minimize artifact generation.
[0095] In some embodiments of the invention, lead wires 504 and the
isolating strips 520 therebetween are similarly formed of materials
with substantially the same X-ray absorption levels. Alternatively
or additionally, strips 520 are formed of the same material as
isolating layer 508. Similarly, in some embodiments of the
invention, vias 510 and isolating layer 508 comprise materials with
substantially the same X-ray absorption levels. Alternatively or
additionally, vias 510 have a width and/or length (e.g., 10 .mu.m)
substantially smaller than the resolution of the X-ray imaging
apparatus, such that the x-ray absorption of the material of vias
510 is very small relative to the amount of x-ray energy
influencing a smallest resolution area on receptor 18.
[0096] In some embodiments of the invention, the x-ray absorption
differences over contact layer 516 and/or over the layers including
wires 504 are less than 10%, 5%, 2%, 0.5% or even 0.1%.
[0097] Substrate 512, and/or isolating layer 508 optionally
comprise a radiolucent, nonconductive material such as a low x-ray
absorbency plastic (for example, Mylar.RTM., polyamide, polyimide,
polyurethane, polycarbonate, or Tyvec.RTM.) or paper.
[0098] In some embodiments of the invention, electrode pads 500,
lead wires 504 and/or vias 510 are formed of materials which have a
relatively high ratio of their conductivity to their x-ray
absorbency. Such materials may have a high conductivity and
comparatively high x-ray absorbency relative to other low
absorbency materials, e.g., aluminum, or may have a relatively low
conductivity with a low x-ray absorbency, e.g., graphite based
deposits and/or carbon layers. Alternatively, any other material
with a comparative ratio between electrical conductivity and x-ray
absorbency, such as amorphous carbon or a carbon slightly doped
with a conductive material such as silver, may be used.
[0099] Optionally, the thickness of pads 500 and/or the cross
section of lead wires 504 and/or vias 510, are chosen as a
trade-off between their x-ray absorbency and their conductance.
Vias 510, as they are very short, optionally have a very small
cross-section, as described above. Lead wires 504 optionally have a
conductance of up to about 100 Ohm in order to minimize voltage
drop of the signals sensed by pads 500 as they are provided by
connector 506. For low conductance materials, e.g., carbon, such
conductance requires a cross section of between about 1000-3000
.mu.m.sup.2, while for high conductance materials, e.g., aluminum,
such conductance requires a cross section of between about 20-80
.mu.m.sup.2.
[0100] In some embodiments of the invention, lead wires 504 have a
circular and/or rectangular cross sectional shape, with a similar
width and length. Thus, the dimensions of lead wires 504 are very
small, optionally smaller than the resolution of receptor 18, thus
decreasing the effect of the wires on the acquired x-ray
images.
[0101] Alternatively or additionally, some or all of lead wires 504
comprise a very thin film with a relatively wide width. The very
thin film has a very low x-ray absorption level and therefore does
not substantially cause artifacts on images generated by receptor
18. The use of wide lead wires 504 spreads artifacts caused by the
lead wires over a large area and therefore the artifacts are
different from anomaly imprints on x-ray images. Thus, the
artifacts do not substantially interfere with identifying anomaly
imprints on the x-ray image. In some embodiments of the invention,
lead wires 504 are included on a plurality of layers so as to allow
room for wide lead wires. Further alternatively or additionally,
some or all of lead wires 504 comprise very narrow, optionally
relatively thick, wires which cover a very small area of probe
40.
[0102] In some embodiments of the invention, all the materials
included in probe 40 are bio-compatible and bio-stable.
Alternatively, the materials of contact layer 516 are
bio-compatible and bio-stable while the materials of probe base 514
have lower bio-compatibility. Thus, the materials of probe base 514
may be less x-ray absorbent, lighter, and/or more conductive or
isolating (as appropriate). Optionally, some or all of the
materials are hypoallergenic.
[0103] In some embodiments of the invention, during manufacture, a
substrate 512 is carved into shape. Thereafter, lead wires 504 are
placed on substrate 512 using any available production method, such
as methods, e.g., photo-resist and/or etching, used in production
of semi-conductors, printed circuit boards (PCBs) and/or flex
circuits. The placement of the amorphous carbon may be performed
using any method known in the art, such as laser deposition and/or
chemical vapor deposition. Strips 520 between lead wires 504 are
then optionally filled in with an isolating material, as described
above. Alternatively or additionally, lead wires 504 are covered
with a uniform thickness layer of the isolating material of strips
520. In this covering, strips 520 are filled in. Lead wires 504 and
strips 520 are then optionally covered by isolating layer 508.
[0104] At the points at which pads 500 are to be placed, holes are
optionally drilled in isolating layer 508, in order to receive vias
510. Optionally, the holes of vias 510 are slanted to allow
covering of the walls of the holes with a conductive material
without filling the holes entirely. Optionally, a conductive
material is placed on the walls of the holes, forming vias 510,
while the remaining volume of the holes is filled with a low x-ray
absorbency material 518, which is optionally non-conductive or a
poorer conductor. Alternatively, the holes are filled entirely with
a conductive material.
[0105] Pads 500 are then placed on isolating layer 508. Thereafter,
a filling material forming isolating strips 502 is filled in the
area between pads 500. Alternatively, a layer of the material of
isolating strips 502 is placed substantially on the entire surface
area of probe 40, and cavities are formed therein for pads 500.
Contact layer 516 is optionally firmly attached to isolating layer
508. Alternatively, contact layer 516 is manufactured separately,
as a disposable contact interface which is connected to a probe
base 514 which includes the remaining layers of probe 40. Thus, the
advantages of using a disposable contact interface for contacting
breast 33, are achieved, while, for example, using expensive
materials and/or structures, which do not interfere with x-ray
imaging, for lead wires 504. Optionally, pads 500 comprise suitable
receptacles which fit on vias 510 of base 514. Alternatively or
additionally, any other attachment method is used to connect
contact layer 516 to probe base 514.
[0106] It is noted that the above manufacture method is presented
by way of example and substantially any other suitable manufacture
method may be used to produce probes in accordance with the present
invention.
[0107] FIG. 4 is a schematic cross-section view of a portion of
probe 40, in accordance with an embodiment of the present
invention. FIG. 4 shows a portion of probe 40 which includes a
single pad 500. In order to equalize the X-ray absorption of probe
40 over substantially its entire area which is in the path of x-ray
imaging of apparatus 32, substrate 512 has different thickness at
different areas, according to the absorption of the remaining
elements of the probe above substrate 512. For example, probe 40
may have three different types of areas, namely, beneath pads 500,
beneath vias 510 and pads 500, and not beneath pads 500. In such a
probe 40, substrate 512 optionally has three respective thickness
areas. Beneath via 510, substrate 512 optionally has a first
thickness 610, defining a hole 620. Beneath pad 500, but not under
via 510, substrate 512 optionally has a second thickness 612,
defining a second hole 622, and in all other areas substrate 512
has a third thickness 614. In some embodiments of the invention,
substrate 512 comprises a different material than the filling 518
of via 510 and/or pad 500. Therefore, the depth of holes 620 and/or
622 is not necessarily equal to the thickness of pad 500.
[0108] Although in some embodiments of the invention, as shown in
FIG. 4, the walls of holes 620 and 622 are shown as straight lines,
in other embodiments of the invention, the walls of one or more of
the holes are slanted and/or rounded. The use of slanted and/or
rounded holes smoothes out any artifacts which may be caused by a
difference in x-ray absorption between the opposite sides of the
walls of the hole.
[0109] In some embodiments of the invention, impedance probe 42 has
any of the structures described above with reference to impedance
probe 40. Optionally, probes 40 and 42 of an apparatus 30 have the
same structure. Alternatively, probes 40 and 42 have different
structures.
[0110] In some embodiments of the invention, probes 40 and 42
comprise different materials, have different layouts of lead wires
504 and/or are formed of different numbers of pieces. Optionally,
probes 40 and/or 42 are marked (e.g., "upper", "lower") so that an
operator can differentiate between probes 40 and 42.
[0111] In some embodiments of the invention, impedance probe 40 has
a higher x-ray absorption level than probe 42. In an exemplary
embodiment of the invention, the x-ray absorption level of probe 42
is allowed to be up to about 1%, while the absorption level of
probe 40 is allowed to be up to about 15%. X-ray energy absorbed by
either of probes 40 and 42 does not participate in formation of an
image by receptor 18. On the other hand, x-ray energy absorbed by
probe 40 does not impinge on breast 33, while x-ray energy absorbed
by probe 42 does impinge on breast 33. Therefore, it is usually
more important to minimize the x-ray absorption of probe 42 than of
probe 40.
[0112] In some embodiments of the invention, impedance probe 42 has
a more uniform x-ray absorption level over its surface, than probe
40. In an exemplary embodiment of the invention, the x-ray
absorption differences over the area of probe 42 are less than
about 0.1%, while the x-ray absorption differences over the area of
probe 40 may go up to about 0.5%. This is because the scattering of
x-rays within breast 33 alleviates the artifacts caused by probe
40. For example, in some embodiments of the invention, the
production process of probe 42 is more accurate than of probe 40.
For example, in laying alumina isolating strips 502, the allowed
difference in thickness between pads 500 and strips 502 is lower
than a first, low, threshold (e.g., 0.1-0.2 .mu.m) in probe 42 and
lower than a second, higher, threshold in probe 40.
[0113] In some embodiments of the invention, probe 40 comprises a
single disposable piece formed of inexpensive materials which have
a moderate x-ray absorbency. Probe 42, however, comprises two
pieces as described above, such that probe base 514 (FIG. 3B) may
comprise expensive materials which have a very low x-ray
absorbency.
[0114] Alternatively or additionally, probe 40 comprises lead wires
504 with a higher conductance and higher x-ray absorbency than the
lead wires 504 of probe 42. For example, the lead wires of probe 40
may have a greater cross-section area or may comprise a more
conductive material. Further alternatively or additionally, the
pads 500 and/or the isolating materials of strips 502 and 520,
layer 508 and/or substrate 512 of probe 42 are less x-ray absorbent
than the respective materials of probe 40. Further alternatively or
additionally, layer 508 and/or substrate 512 are thinner in probe
42 than in probe 40.
[0115] Alternatively or additionally, probe 42 comprises a
structure in accordance with any of the above described
embodiments, while probe 40 has a structure known in the art, such
as described in above mentioned U.S. Pat. Nos. 5,810,742, or
6,157,697.
[0116] In some embodiments of the invention, probes 40 and 42 have
the same pad arrangements. The use of the same pad arrangements for
both of probes 40 and 42 allows generating impedance images of
substantially the same quality by both of probes 40 and 42 and
allows more freedom in planning impedance imaging sessions.
[0117] Alternatively, probes 40 and 42 have different pad
arrangements. For example, probe 42 may have a different element
structure, which has a lower x-ray absorption level and/or lower
x-ray absorption difference over its surface, than probe 40. In
some embodiments of the invention, probe 42 has fewer pads 500
(e.g., an 8.times.8 array) than probe 40 (e.g., a 45.times.60
array) and hence requires fewer lead wires 504. Thus, thinner wires
may be used for the same impedance levels on a single layer of the
probe. Thus, probe 42 has less x-ray absorption differences over
its area and/or less x-ray absorption. Alternatively or
additionally, probe 42 is smaller than probe 40 and/or has narrower
or wider isolating strips 502 between its pads 500. In some
embodiments of the invention, images are normally generated based
on signals sensed by probe 40. One or more images with lower
resolution (due to the fewer pads 500 included in probe 42) may be
provided based on signals from probe 42.
[0118] In other embodiments of the invention, one of probes 40 and
42 is used for electrification and the other is used for imaging.
Using one of the probes only for electrification allows planning
that probe to better suite the electrification task and/or to be
less x-ray absorbent or otherwise x-ray interfering. Optionally,
probe 42 comprises the electrification probe and has elongated
strips of conductors arranged in parallel rows. Such elongated rows
may be electrically connected from a side of probe 42 outside of
the imaging region, and therefore are much less x-ray interfering.
Alternatively, probe 42 comprises elements organized in circles or
comprises a single planar conductive electrode.
[0119] In some embodiments of the invention, additional probes on
sides of breast 33 are used in impedance imaging, in addition to
probes 40 and 42. For example, two electrification probes on sides
of breast 33 may be used in addition to probes 40 and 42 used for
imaging on the top and bottom of breast 33. The electrification
probes optionally apply electrification voltage and/or current
signals from opposite sides while probes 40 and 42 sense voltage
signals.
[0120] In some embodiments of the invention, one or both of probes
40 and 42 have one or more holes for inserting a needle (e.g., a
biopsy needle) and/or for passing fingers of a surgeon. The probe
40 and/or 42 having the hole or holes is optionally selected as the
one which will cause fewer or less troublesome artifacts on the
x-ray images due to the hole. Alternatively or additionally, the
holes are located on the probe which allows easier access to a
physician. In some embodiments of the invention, a probe serving
mainly and/or only as an electrification probe includes the holes.
Thus, the area of the holes does not interfere with creation of the
images.
[0121] It is noted that a wide range of impedance imaging sessions
may be used with the apparatus of the present invention. Impedance
imaging sessions are described, for example, in U.S. Pat. No.
5,810,742, and/or PCT/IL00/00839. Electrification signals may be
applied from electrode 56, probe 40, probe 42, from other
electrodes and/or from any combination of electrodes and probes. As
described above, the images may be acquired by one or both of
probes 40 and 42 in a single stage or in a plurality of stages.
[0122] For example, during an imaging session, some of the images
are acquired by probe 42 based on electrification from probe 40 and
some of the images are acquired by probe 40 based on
electrification from probe 42. Alternatively or additionally,
electrification signals are applied from specific elements of one
or both of probes 40 and 42 and the images are acquired by the
remaining elements of one or both of the probes. In an exemplary
embodiment of the invention, signals are applied from one or more
specific elements of probe 40 and from one or more specific
elements of probe 42, while the remaining elements of probes 40 and
42 are used to generate two images from opposite sides. Optionally,
the values for the pixels of the images corresponding to the
elements used for electrification are calculated using a suitable
interpolation method.
[0123] In some embodiments of the invention, a symbiotic
relationship between the imaging modalities takes place. Since each
technique relies on different properties of the lesion, impedance
imaging enhances the understanding of x-ray imaging and vice versa.
In general, coincident detection of features is expected. When
anomalies are seen only on one modality, settings and methods may
be somewhat altered in the other modality in order to arrive at
coincident detection. Optionally, the knowledge of the improved
settings and methods may be used in future imaging. An example of
an imaging procedure with such a symbiotic process is now described
with reference to FIG. 5.
[0124] FIG. 5 is a flowchart of the acts performed in a dual
modality imaging procedure, in accordance with an embodiment of the
present invention. Breast 33 is placed (800) between support plate
22 and compression plate 20. Optionally, a conductive gel layer is
placed (802) between breast 33 and probe 40 and/or 42. Compression
plate 22 is then closed (804) on breast 33 and one or more images
are acquired (806) by x-ray tube 14 and receptor 18. Optionally,
one or more impedance images are acquired (808) using impedance
probes 40 and/or 42. The acquired images are analyzed (810) to
detect possible anomalies in breast 33 and/or find unclear regions
which require additional imaging. Responsive to the analysis, one
or more additional impedance imaging sessions are performed (812)
with one or more parameters selected responsive to the detected
possible anomalies. The results of the additional impedance session
are analyzed to determine (814) the existence, location and/or type
(e.g., cancerous or non-cancerous) of the possible anomaly.
Optionally, one or more additional x-ray images are acquired (816)
with one or more parameters adjusted responsive to the above
determination (814). The one or more adjusted parameters, may
comprise for example, the angle from which the images are taken
and/or the intensity of the x-rays used in the imaging, for example
for unclear regions.
[0125] Referring in more detail to placing (802) the conducting gel
layer, the gel may be placed by smearing the gel on the breast 33
or on probe 40, as is known in the art. Alternatively or
additionally, the gel may be pre-placed on a disposable probe 40 or
surface contact piece thereof, for example inside wells surrounding
the pads thereof, as described for example in U.S. Pat. No.
5,810,742. Further alternatively or additionally, the gel is placed
in the form of an interface sheet, such as described in PCT
application PCT/IL00/00287, filed May 21, 2000, and/or in PCT
application PCT/IL00/00127. The use of an interface sheet isolates
breast 33 from probe 40, such that a reusable probe 40 may be
employed without endangering the patient. Optionally, the gel layer
comprises a material with a low x-ray absorbency. Using an
interface sheet also allows the use of non-bio-compatible materials
for pads 500 and isolating strips 502 and therefore allows using
less x-ray absorbent and/or more conductive materials. In some
embodiments of the invention, the gel comprises some adhesive
properties which connect probe 40 and/or 42 to the breast.
[0126] Referring in more detail to analyzing (810) the x-ray images
and optionally impedance images, in some embodiments of the
invention, the analysis is performed automatically by a processor,
e.g., computer 24. Alternatively or additionally, the analysis is
performed by a human operator. For example, the images may be
displayed on monitor 26 for examination by the operator. In some
embodiments, both the x-ray apparatus and the impedance probe
produce digital images that are displayed on monitor 26. The images
may be displayed one after the other, one next to the other and/or
overlaid one on top of the other. Alternatively, film images of the
two modalities are produced and superimposed on a light box.
Alternatively, the impedance image is printed on a transparency for
viewing with a film image, on a light box. Alternatively still, a
film image is scanned in order to produce a digital image, and the
digital images are overlaid and viewed on a computer monitor.
[0127] In some embodiments of the invention, digital images that
are overlaid and viewed on the computer monitor can undergo image
processing by the computer. Image processing may comprise changing
the dimensions of one image, in order to match the dimensions of
the other image; zooming in on an area, removing noise of any kind
and other image-enhancement processing as known in the art.
[0128] Optionally, x-ray images acquired while probes 40 and/or 42
are in place, are processed by a signal processing program, running
for example on computer 24, which removes the anticipated pattern
of multi-element impedance probe 40. Optionally, computer 24
identifies the artifacts on the acquired x-ray images and removes
them accordingly. Alternatively or additionally, computer 24
removes shadowing artifacts expected for the layout of probes 40
and/or 42. Optionally, computer 24 stores one or more known probe
layouts and uses for post processing the stored layout which
belongs to the probes 40 and/or 42 currently used. Alternatively or
additionally, before an imaging session, a blank image is taken
with probes 40 and/or 42 in place but without breast 33, and the
blank image is analyzed to determine the artifacts caused by the
probes.
[0129] In some embodiments of the invention, the results of the
analysis (810) determine the depth of a suspected anomaly and the
additional analysis (814) is used to determine the type of the
anomaly, e.g., whether the anomaly has the characteristics of a
malignant region. The depth may be determined by acquiring x-ray
images from two different angles, as is known in the art.
Alternatively or additionally, the analysis (810) is used to
determine a two dimensional location of an anomaly and the
additional analysis (814) is used to determine the depth of the
anomaly. Further alternatively or additionally, the results of the
analysis (810) indicate an unclear area and the additional analysis
(814) is used to carefully scan the unclear area.
[0130] Further alternatively or additionally, the results of the
analysis (810) are used in normalizing the results of the impedance
imaging. Optionally, the analysis of the x-ray image and/or the
combined image determine an area with a suspected area and a clear
area most distinctly without anomalies. The results of the
impedance imaging (812) of the clear area are used to normalize the
results of the imaging of the suspected area, thus providing a
better view of the suspected anomaly and/or more accurate data on
the anomaly.
[0131] In an exemplary embodiment of the invention, one of probes
40 and 42 is used for sensing signals used in forming an image,
while the other probe is used to provide electrification signals to
breast 33. Optionally, the additional impedance imaging session is
performed with specific electrification patterns and/or sensing
patterns suitable for examining the suspected anomaly. For example,
the electrification signals may be applied to two parallel lines of
pads on opposite sides of the suspected anomaly, as described in
PCT application PCT/IL00/00839. In some embodiments of the
invention, the distance between parallel lines and a point above
the suspected anomaly is substantially equal to the depth of the
anomaly. Optionally, the electrification signals to the parallel
lines have different phases, optionally opposite phases.
[0132] Alternatively or additionally, any other impedance imaging
methods, such as described, for example, in PCT/IL00/00839 and/or
in U.S. Pat. No. 5,810,742, are used. Any of the parameters of such
imaging methods may be adjusted responsive to the analysis (810).
In some embodiments of the invention, the adjusted parameters
comprise the amplitude and/or frequency of the electrification
signals. For example, deeper anomalies may require electrification
signals with a higher amplitude and/or a different frequency than
used for shallow anomalies. Alternatively or additionally, the
adjusted parameters comprise a determination of which pads of the
electrification probe are used in the electrification, e.g., how
many of the pads and/or in which configuration. Further
alternatively or additionally, the adjusted parameters comprise a
determination of which elements (on one probe or two probes) are
used for electrification and which elements are used for sensing.
Further alternatively or additionally, the adjusted parameters
comprise a determination of whether a remote electrode is to be
used.
[0133] In some embodiments of the invention, in which the applied
signals have different phases as described in PCT/IL00/00839, the
adjusted parameter comprises the phase difference between the
applied signals.
[0134] In some embodiments of the invention, after determining the
location and/or type of the anomaly, a biopsy needle is directed to
the anomaly in order to receive additional information on the
anomaly. The guidance of the needle toward the anomaly may be
performed using impedance imaging methods, such as described in
PCT/IL00/00839 and/or U.S. Pat. No. 5,810,742. Optionally, an
electrical signal is applied to the biopsy needle so that its
advance is easily detected by probe 40 and/or 42. It is noted that
the guidance using impedance imaging is possible even for anomalies
which are only detected based on x-ray images, based on the
registration of the impedance images and the x-ray images. An
additional x-ray image may be taken when the biopsy needle reaches
the designated point as an additional verification that the needle
is at the correct point.
[0135] Referring in more detail to acquiring (816) the additional
x-ray images, the additional images are acquired from different
angles and/or with different x-ray beam intensities. The different
angles and/or intensities are optionally selected responsive to an
analysis of previously acquired images. For example, additional
x-ray images may be acquired from an angle in which probes 40
and/or 42 cause fewer artifacts in a specific area of interest.
[0136] It is noted that the entire imaging process may be repeated
for a different angular view of breast 33, for example, a lateral
view, in which the apparatus is rotated, and the breast is
compressed from the side.
[0137] In some embodiments, the symbiotic relationship is further
extended to the understanding of what features and types of lesions
are better visualized by x-ray, and what features and what types of
lesions are better detected by impedance. As such, specificity and
sensitivity of each technique to certain features and types of
lesions may be studied and compared. Since different sensitivities
exist, the use of both modalities together allows for more thorough
diagnosis.
[0138] Alternatively or additionally to adjusting the acquisition
of data of one modality responsive to imaging results from another
modality, the display of the data acquired for one of the
modalities is adjusted responsive to results from another
modality.
[0139] In some embodiments of the invention, the type of the
parameter of the impedance imaging which is displayed (e.g.,
critical frequency, phase, capacitance, conductivity) is selected
responsive to results from the imaging of another modality.
Alternatively or additionally, during the impedance imaging, data
is collected for a plurality of stimulation signals and the data
displayed is chosen responsive to the imaging results from another
modality. For example, data may be acquired with applied
stimulation signals at a plurality of locations, layouts, phase
differences, frequencies and/or amplitudes. The displayed image is
optionally chosen responsive to data from images of another
modality, e.g., the location of a suspected anomaly in acquired
x-ray images. For example, for a suspected anomaly at a depth x
beneath probe 40, data may be displayed from imaging performed with
stimulation signals applied from opposite sides, optionally at
distance x, from the surface area above the suspected anomaly.
[0140] In some embodiments of the invention, combined mammography
and impedance imaging procedures are performed for a plurality of
patients one after the other using the same apparatus. For safety
purposes, before the breast of each patient is placed in the
mammogram, a disposable contact surface is placed on compression
plate 20 and/or on support plate 22. The contact surface may
comprise, as described above, a gel sheet a probe 40 and/or 42 and
or a contact layer of a probe, for example including pads 500
without leading wires 502. Changing the contact surface between
patients eliminates the need for sterilization and/or cleaning of
the apparatus between imaging procedures.
[0141] Alternatively or additionally to the method of FIG. 5, any
other combined impedance imaging and x-ray imaging method may be
used. Particularly, the x-ray images and impedance images may be
obtained in any order and/or simultaneously.
[0142] The method of FIG. 5 and/or other imaging methods in which
the parameters of one modality are adjusted responsive to results
of imaging using another modality, are not limited to the above
described apparatus, but rather may be used with substantially any
x-ray apparatus known in the art, including apparatus for imaging
tissue other than the breast.
[0143] In some embodiments of the invention, instead of having all
of probe 42 in place during the acquisition of the x-ray image,
only a body contact portion of probe 42 is in place. After the
x-ray image is acquired, the remaining parts of probe 42 are put in
place, optionally after removing receptor 18. Optionally, the body
contact portion comprises a thick non-conductive substrate of a
very low x-ray absorbance, which can serve as a support plate. The
contact portion includes a surface facing the breast, pads 500 as
described above. Thin conductive vias lead, through the substrate,
from pads 500 to an opposite side of the substrate. A second part
of probe 42 includes leading wires 504 and ports which connect the
vias from the body contact portion to the leading wires.
[0144] The principles of the present invention are not limited to
dual modality apparatus. In some embodiments of the invention, an
additional modality, beyond impedance and X-ray, is used in
examining breast 33. The third modality may be substantially any
suitable imaging method known in the art, such as gamma imaging.
For example, a gamma camera may fit onto impedance probe 40 of
compression plate 20.
[0145] It will be appreciated that the above described methods may
be varied in many ways, including, changing the order of steps,
and/or performing a plurality of steps concurrently. For example,
the steps described above of manufacturing probe 40 may be
performed in a different order. It should also be appreciated that
the above described description of methods and apparatus are to be
interpreted as including apparatus for carrying out the methods,
and methods of using the apparatus. The present invention has been
described using non-limiting detailed descriptions of embodiments
thereof that are provided by way of example and are not intended to
limit the scope of the invention. It should be understood that
features and/or steps described with respect to one embodiment may
be used with other embodiments and that not all embodiments of the
invention have all of the features and/or steps shown in a
particular figure or described with respect to one of the
embodiments. Variations of embodiments described will occur to
persons of the art. Furthermore, the terms "comprise," "include,"
"have" and their conjugates, shall mean, when used in the claims,
"including but not necessarily limited to."
[0146] It is noted that some of the above described embodiments may
describe the best mode contemplated by the inventors and therefore
may include structure, acts or details of structures and acts that
may not be essential to the invention and which are described as
examples. Structure and acts described herein are replaceable by
equivalents which perform the same function, even if the structure
or acts are different, as known in the art. Therefore, the scope of
the invention is limited only by the elements and limitations as
used in the claims.
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