U.S. patent application number 11/182853 was filed with the patent office on 2005-11-10 for method for exploring and displaying tissues fo human or animal origin from a high frequency ultrasound probe.
This patent application is currently assigned to Centre National de la Recherche Scientifique. Invention is credited to Berger, Genevieve, Laugier, Pascal, Puech, Michel, Saied, Amena.
Application Number | 20050251043 11/182853 |
Document ID | / |
Family ID | 9521666 |
Filed Date | 2005-11-10 |
United States Patent
Application |
20050251043 |
Kind Code |
A1 |
Saied, Amena ; et
al. |
November 10, 2005 |
Method for exploring and displaying tissues fo human or animal
origin from a high frequency ultrasound probe
Abstract
A method for displaying scanned ultrasound images of tissue
employs an apparatus including an ultrasound probe mounted to a
mechanical head. A three-dimensional positioning system mounts the
head for positioning the probe in proximate orthogonal relation to
the tissue. A computer controls the three-dimensional positioning
system thereby moving the probe during a scan. The probe transmits
high frequency ultrasound waves whose nominal frequency is included
within the range from 30 to 100 MHz and with a large pass band,
adapted to frequencies reflected by the tissue. The beams of
ultrasound transmission are focused in a given zone of the tissue
over a vertical penetration distance of between 20 and 30 mm.
Reflected signals are acquired and processed for display.
Inventors: |
Saied, Amena; (Paris,
FR) ; Berger, Genevieve; (Bourg-La-Reine, FR)
; Laugier, Pascal; (Paris, FR) ; Puech,
Michel; (Paris, FR) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ LLP
SUITE 800
1990 M STREET NW
WASHINGTON
DC
20036-3425
US
|
Assignee: |
Centre National de la Recherche
Scientifique
Paris
FR
|
Family ID: |
9521666 |
Appl. No.: |
11/182853 |
Filed: |
July 18, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11182853 |
Jul 18, 2005 |
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09600073 |
Feb 5, 2001 |
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6949071 |
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09600073 |
Feb 5, 2001 |
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PCT/FR99/00040 |
Jan 12, 1999 |
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Current U.S.
Class: |
600/443 ;
600/437 |
Current CPC
Class: |
A61B 8/10 20130101; A61B
8/4483 20130101 |
Class at
Publication: |
600/443 ;
600/437 |
International
Class: |
A61B 008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 12, 1998 |
FR |
98 00209 |
Claims
1. A method for the investigation and display of tissues of human
or animal origin in 2 or 3D, comprising the use of a probe with a
fixed focusing area or a dynamic focusing area capable of
generating beams of ultrasound, convergent waves in a nominal broad
bandwidth, adapted to the frequencies reflected by the tissue
investigated.
2. The method of claim 1, wherein said probe is a multi-element
with circular symmetry, made up of several concentric annular
transducers evenly spaced over a plane surface or with spherical
concavity, said transducers being independent of each other and
being controlled individually in transmission and in reception by
pulses which are offset in time.
3. The method of claim 1, wherein the focal distance is modified by
an electronic control process.
4. The method of claim 1, wherein the focal distance is modified by
a numerical process.
5. The method according to claim 1, wherein the focal distance is
adjusted to 20 to 30 mm to investigate the posterior segment.
6. The method according to claim 1, applicable in gynecology and
obstetrics, in gastroenterology, in the field of cardiovascular
examinations and examinations by coelioscopy, or in dermatology.
Description
CROSS REFERENCE INFORMATION
[0001] This application is a Continuation of co-pending Application
Ser. No. 09/600,073, filed on Feb. 5, 2001, which is the national
phase of PCT International Application No. PCT/FR99/00040 filed on
Jan. 12, 1999, which designated the United States, and on which
priority is claimed under 35 U.S.C. .sctn. 120; and this
application claims priority of Application No. 98-00209 filed in
France on Jan. 12, 1998 under 35 U.S.C. .sctn. 119. The entire
contents of all are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a process for the
investigation and display, using ultrasound echography techniques,
of tissue structures of human or animal origin such as in
particular the ocular globes and more particularly of the posterior
segment (the vitreous cavity, the posterior wall of the globe lined
by the choroid and the retina, the macula), tissue structures of
the anterior segment (the cornea, the anterior chamber, the iris
and the crystalline lens). The invention also relates to a device
and an ultrasound probe which allow this investigation and this
display to be achieved in 2D or 3D.
BACKGROUND OF THE INVENTION
[0003] In ultrasound imaging and more particularly in medical
echography, the choice of frequency is dictated by the compromise
between resolution and penetration depth. Specifically, because of
the increase in attenuation of ultrasound waves with frequency, the
penetration depth of ultrasound increases with decreasing
frequency. However, the image resolution decreases with decreasing
frequency.
[0004] In addition, a process for the investigation and display of
human tissues is known, through document U.S. Pat. No. 5,178,148,
for determining the volume of a tumour or of a gland using signals
coming from a probe steered by the process.
[0005] Processes are known, in particular through patent FR
2,620,327, for the investigation of ocular structures, by
echography, using probes operating at low frequencies of the order
of 10 MHz, and focused to a depth roughly equal to the size of an
ocular globe (about 23 to 25 mm). These processes mean, on one
hand, that images in section of the posterior segment of the eye
can be achieved with spatial resolutions of the order of a
millimetre and, on the other hand, that a very rough examination of
the entire anterior segment of the eye can be carried out.
[0006] The major drawback of low-frequency echography is mainly the
low resolution (600 to 700 .mu.m) provided by these low
frequencies, which do not allow detailed analysis of the retina and
the other layers of the posterior wall of the eye (choroid and
sclera) and more particularly in the macular region.
[0007] In order to increase both the lateral and axial resolution,
investigation and display processes using ultrasound probes at high
frequency, of the order of 50 to 100 MHz (cf. U.S. Pat. No.
5,551,432 and C. J. PAVLIN, M. D. SHERAR, F. S. FOSTER: "Subsurface
ultrasound microscopic imaging of the intact eye", Ophthalmology
97: 244, 1990), with a short focal length (of about 4 to 8 mm),
have enabled the use, with a resolution of 50 .mu.m, of structures
of the anterior segment of the eye, to depths of the order of 5 mm,
or of structures of the peripheral retina which are very close to
the anterior segment.
[0008] In conclusion, it is therefore accepted that the use of high
frequencies seems to be limited to investigation of the anterior
segment and the peripheral retina, whereas investigation of the
deep structures (posterior segment) requires the use of much lower
frequencies, while only providing very low spatial resolutions, of
a few hundred microns.
BRIEF DESCRIPTION OF THE INVENTION
[0009] The present invention aims to alleviate the drawbacks of the
known processes of the prior art, by proposing an investigation and
display process using a high-frequency ultrasound probe which
combines both very high spatial resolution and a field of
investigation covering the anterior and posterior segments of the
ocular globe.
[0010] To this end, the process for the investigation and display
of tissues of human or animal origin is characterized in that:
[0011] an ultrasound probe is positioned, said probe being carried
by a head steered by means of a three-dimensional positioning
system, in particular a system controlled by a computer at right
angles to said tissue structure,
[0012] the probe is controlled such that it generates beams of
convergent high-frequency ultrasound waves whose nominal frequency
is included within the range from 30 to 100 MHz with a broad
bandwidth, adapted to the frequencies reflected by the structure
investigated, these waves being focused on a given area of tissue
structure,
[0013] the tissue structure is scanned by the positioning system
steered by the computer, while said computer carries out, in
parallel, the acquisition of the signals reflected by the tissue
structure,
[0014] various signal processing operations are carried out on the
data coming from the scanning, to improve the reproduction of the
information and to facilitate the interpretation thereof by the
practitioner.
[0015] According to another advantageous characteristic of the
invention, the probe is excited such that it generates wave beams
whose nominal frequency is included within the range from 30 to 100
MHz with a broad bandwidth, adapted to the frequencies reflected by
the structure investigated.
[0016] According to yet another advantageous characteristic of the
invention, the wave beams are focused over a vertical penetration
distance of between 20 and 30 mm.
[0017] Other characteristics and advantages of the present
invention will emerge from the description given hereinbelow, with
reference to the appended drawings which illustrate an entirely
non-limiting embodiment of the invention. In the figures:
BRIEF DESCRIPTION OF THE FIGURES
[0018] FIG. 1 is a synoptic view of a device enabling the process
forming the subject of the invention to be implemented;
[0019] FIG. 2 is a view illustrating a use of the process forming
the subject of the invention for the investigation of the posterior
segment of an ocular globe;
[0020] FIG. 3 is a view illustrating a use of the process forming
the subject of the invention for the investigation of the anterior
segment of an ocular globe;
[0021] FIGS. 4a and 4b illustrate, on one hand, a front view of one
embodiment of the ultrasound probe consisting of an annular array
whose focus point can be modified electronically and, on the other
hand, a side view of this same probe into which a phase difference
has been introduced at transmission or at reception between the
various rings making up the array;
[0022] FIG. 5 is a view illustrating a use of the process forming
the subject of the invention for the investigation of the anterior
segment of an ocular globe, using a dynamic focusing probe;
[0023] FIG. 6 is a view illustrating a use of the process forming
the subject of the invention for the investigation of the posterior
segment of an ocular globe, using a dynamic focusing probe;
[0024] FIG. 7 shows a comparison between a macular section of a
human globe in vitro, obtained by macroscopic histological imaging
(right side) and an image arising from the process forming the
subject of the invention (left side) where P represents the retinal
folds, R the retina, S the sclera and V the vitreous humour;
[0025] FIG. 8 is the image obtained from an anterior segment of a
rabbit's eye, by the process forming the subject of the invention,
where C represents the cornea, I the iris, S the sclera and Cr the
anterior surface of the lens.
DETAILED DESCRIPTION OF THE INVENTION
[0026] According to a preferred embodiment of the process forming
the subject of the invention, of which one system enabling its
implementation is shown schematically in FIG. 1, the process
consists in positioning an ultrasound probe 1 mounted within a head
articulated in three dimensions X, Y, Z, at least one direction of
which can be fixed, this head being steered by a servo-controlled
positioning system 2, controlled by a computer 3, in particular in
a direction perpendicular to the medium to be investigated.
[0027] This ultrasound probe 1 consists mainly of a transducer, in
particular one made of PVDF (polyvinylidene difluoride), controlled
by a transmitter/receiver 4, in order to generate beams of
convergent, broadband, ultrasonic waves, these waves being able to
adopt a spherical or linear profile.
[0028] Next, FIG. 2 shows an investigation of the posterior segment
of an ocular globe 5, previously inserted into a coupling medium 6
which does not impair the propagation of the waves, especially in
the retina region. A probe 1 positioned on the pars plana 7 is used
to avoid absorption of the ultrasound beam by the lens 8 (this lens
also marking the boundary between the posterior segment 9 and the
anterior segment 10 of an ocular globe 5). This probe 1 transmits
beams of ultrasound waves set within a nominal broadband frequency
range varying from 30 to 100 MHz, involving wavelengths going from
50 to 15 .mu.m, focused at a focal length of between 20 and 30 mm
and preferably 25 mm, corresponding in fact to a focus at an
average depth of an ocular globe.
[0029] For example, for a probe with a nominal frequency of 50 MHz,
lateral and axial resolutions of 220 and 70 .mu.m respectively are
obtained at the focal length.
[0030] The receiving system will have a bandwidth adapted to the
frequencies reflected by the structure, these frequencies being
lower than the transmitted frequencies because of the attenuation
by the medium which is crossed.
[0031] In order to investigate the anterior segment (cf. FIG. 3),
this same probe 1 is used under the same control conditions as
previously, in a position offset on the vertical axis (Z axis) at a
distance corresponding in fact to the previous focal length.
[0032] According to another embodiment, the focal length,
especially on the vertical penetration axis, is not modified by a
mechanical servocontrol 2 in the position, but by an electronic or
digital device steering the probe and able to modify, by careful
command, the focusing area of the probe, in order thus to obtain
simultaneously a high resolution image of the anterior segment and
of the posterior segment of the eye. This probe, with dynamic
focusing carried out by an electronic or digital control process,
consists of a multi-element probe, with circular symmetry, made up
of several concentric annular transducers evenly spaced over a
plane surface or with spherical concavity (refer to FIG. 4a). These
transducers are independent of each other and are controlled
individually in transmission and in reception by pulses which are
offset in time (refer to FIG. 4b which shows dynamic focusing
obtained by introducing a phase difference--time delay--into the
transmission between the various rings).
[0033] In transmission, the generated wavefront is convergent and
its curvature is modified according to the distance between the
structure investigated and the probe. The peripheral rings transmit
first and the excitation of the central ring is the most retarded.
Thus the focal length along the axis of the probe can be varied and
is therefore determined by the phase difference or the time delay
introduced between the various transducers. The same principle of
dynamic focusing is used in reception: the electronic delay is
adjusted to the depth of the echoes which arrive at that moment at
the probe. In this way the depth of field is increased without in
any way degrading the lateral resolution.
[0034] A measurement system, of which each of the components
(digitizer 11, computer 3, control electronics 2,
transmitter/receiver 4, etc.) forming it has a bandwidth compatible
with the processing and analysis of the signals originating from
the anterior segment and/or of the signals coming from the
posterior segment of the eye, enables processing of the signals
backscattered by the structure investigated. Thus, the
backscattered ultrasound signal is amplified then digitized using
the digitizer 11, at a given sampling frequency (in particular of
the order of 400 MHz over 8 bits).
[0035] This same computer controls the stepper on DC motors in
order to move the probe and scan the ultrasound beams over the
sample in a defined step along X and along Y in order to allow
another measurement point or in an R,.OMEGA. step using a probe
support head which allows an arciform scan.
[0036] For in vivo measurements and investigations, it is
necessary, in order to get round the problem of parasitic movements
of the eye in its orbit, to process the signal in real time and to
have available an extremely fast and accurate probe movement
system.
[0037] According to another characteristic, the computer is fitted
with a module for processing the image and the radiofrequency
signal. This module has programmed software which enables the two
quantitative approaches, of 2D and/or 3D biometry and of tissue
characterization, to be carried out.
[0038] The echographic signal can be shown in real time in the form
of a A-scan line or in the form of a 2D image of the B-scan type.
The B-scan images can display sections in the various planes
parallel to the direction of propagation of the ultrasound (cf.
FIGS. 7 and 8). A 2D image of the C-scan type can also be
calculated in order to display sections in the plane perpendicular
to the direction of propagation of the ultrasound. The C-scan is
able to show sections located at different depths of the whole
ocular globe.
[0039] The calculation and the reconstruction of the 3D image can
be carried out using programmed mathematical functions specific to
the ultrasound data to be processed.
[0040] Thus, provided the propagation speed of the ultrasound in
the structures investigated is known, it is possible to determine
morphological characteristics of these structures, especially their
thickness and/or their volume.
[0041] The processing software of the radiofrequency signal enables
a frequency analysis of the digitized and recorded backscattered
signals to be made in order to calculate quantitative ultrasound
parameters for the purpose of tissue characterization. These
parameters are in particular the attenuation coefficient in
dB/cm.MHz (decibels/cm.megahertz), the overall attenuation
coefficient in dB/cm, the backscatter coefficient in dB/cm.MHz and
the overall backscatter coefficient in dB/cm.
[0042] These parameters can be estimated locally and their values
can be shown in the form of images (parametric images).
[0043] It is of course possible to add other algorithms for
processing the radiofrequency signal and the image, algorithms
which could produce quantitative morphological and/or tissue
information capable of characterizing the structures of the
eye.
[0044] The images obtained by this investigation process, both for
an ocular globe and the region of the anterior segment and the
posterior segment, have a resolution which is improved by a factor
of at least two to three compared with that obtained with
conventional echographs and are not limited by the transparency of
the media investigated as in particular with conventional optical
investigation means (biomicroscopy, angiography) whose quality can
be affected by the presence of cataracts and haemorrhages.
[0045] By way of example, FIG. 7 illustrates the similarities
between a histological image and an echographic image of the macula
of a human eye (in vitro), and FIG. 8 illustrates an image of an
anterior segment of a rabbit's eye.
[0046] The process and the device which enables its implementation,
such as those described previously, are not limited to applications
in ophthalmology, but they can also find applications in
gynaecology and obstetrics, in gastro-enterology and in the field
of cardio-vascular examinations and examinations by coelioscopy, or
in dermatology and more generally in any medium which reflects a
usable signal.
[0047] In particular, in the field of dermatology, it is possible,
using the investigation and display process forming the subject of
the invention, to investigate the various thicknesses of tissue
forming the skin. Thus, it is possible for example, by processing
the signal, to assess the degree of skin hydration, to evaluate
healing of a tissue, to localize and investigate a tumour, and
finally, more generally, to to open the way to examining a large
number of pathologies currently encountered in dermatology.
[0048] The focus point or focusing area of the wave beam will be
adjusted within a range going from a few tenths of a millimetre to
several millimetres and the waveband used will be between 30 and
100 MHz.
[0049] It is of course understood that the present invention is not
limited to the embodiments described and shown hereinbefore, but
that it encompasses all the variants thereof.
* * * * *