U.S. patent application number 13/408370 was filed with the patent office on 2012-06-21 for peripheral brachytherapy of protruding conformable organs.
This patent application is currently assigned to Advanced Radiation Therapy, LLC. Invention is credited to Raymond J. Bricault, Piran Sioshansi.
Application Number | 20120157748 13/408370 |
Document ID | / |
Family ID | 36916985 |
Filed Date | 2012-06-21 |
United States Patent
Application |
20120157748 |
Kind Code |
A1 |
Sioshansi; Piran ; et
al. |
June 21, 2012 |
Peripheral Brachytherapy of Protruding Conformable Organs
Abstract
A system for and method of applying non-invasive brachytherapy
to a targeted volume within a protruding organ of a patient,
employs an applicator constructed so as to be positioned relative
to the organ so that an enhanced dose of divergent radiation is
deliverable from at least two locations at or very near the
periphery of the organ transcutaneously to the targeted volume of
the protruding organ from at least two directions so that a higher
dose is delivered to the targeted volume than to tissue surrounding
the targeted volume. The treatment planning, and image guidance
techniques are also described.
Inventors: |
Sioshansi; Piran; (Lincoln,
MA) ; Bricault; Raymond J.; (West Boylston,
MA) |
Assignee: |
Advanced Radiation Therapy,
LLC
Billerica
MA
|
Family ID: |
36916985 |
Appl. No.: |
13/408370 |
Filed: |
February 29, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11354620 |
Feb 15, 2006 |
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13408370 |
|
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60653191 |
Feb 15, 2005 |
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Current U.S.
Class: |
600/3 |
Current CPC
Class: |
A61N 2005/1098 20130101;
A61N 5/1084 20130101; A61N 2005/1061 20130101; A61N 2005/1097
20130101 |
Class at
Publication: |
600/3 |
International
Class: |
A61M 36/00 20060101
A61M036/00 |
Claims
1. A method of non-invasively delivering brachytherapy to a
designated volume within a protruding organ, comprising: a.
Identifying a designated volume within the organ in need of
radiation treatment, and determining locations at or near the
periphery of the organ from which an enhanced dose of divergent
radiation can be transcutaneously delivered to the designated
volume of the protruding organ so that a higher dose is delivered
to the designated volume than to tissue surrounding the designated
volume; b. Employing image guidance to locate the designated
volume; c. Securing a non-invasive applicator to the organ so that
the applicator can receive and fixedly position at least one
radiation source relative to the designated volume; and d. Exposing
for a predetermined amount of time the designated volume at each of
the determined locations at or near the periphery of the organ so
that a therapeutic dose is delivered to the targeted volume and a
sub-therapeutic dose is delivered to the targeted volume and a
sub-therapeutic dose is delivered to tissue surrounding the
designated volume.
2. A system for non-invasively delivering brachytherapy to a
designated volume within a protruding organ, comprising: a. an
imaging system constructed and arranged so as to (a) Identify a
designated volume within the organ in need of radiation treatment,
(b) aid in the determination of locations at or near the periphery
of the organ from which an enhanced dose of divergent radiation can
be transcutaneously delivered to the designated volume of the
protruding organ so that a higher dose is delivered to the
designated volume than to tissue surrounding the designated volume;
and (c) assist in the employment of image guidance to locate the
designated volume; b. a non-invasive applicator shaped so that the
applicator can be fixed relative to the organ, the applicator being
constructed and arranged so that the applicator can receive and
fixedly position at least one radiation source relative to the
designated volume; expose for a predetermined amount of time the
designated volume at each of the determined locations at or near
the periphery of the organ so that a therapeutic dose is delivered
to the targeted volume and a sub-therapeutic dose is delivered to
the targeted volume and a sub-therapeutic dose is delivered to
tissue surrounding the designated volume.
3. A method of applying brachytherapy to a protruding organ,
comprising: placing a non-invasive applicator on the organ, the
applicator constructed and arranged so as to receive at least one
radiation source and expose a designated volume within the organ
from at least two dwell positions; controlling the dwell position
and the dwell time of the radiation source placed via the
applicator at a close distance to the periphery of the organ such
that the diverging exposure field from each dwell position is
superpositioned on the diverging exposure field from other dwell
positions to deliver a therapeutic dose to a large portion or
substantially the entire volume of the said organ.
4. A system for applying brachytherapy to a protruding organ,
comprising: a non-invasive applicator configured to contact the
organ during treatment, the applicator constructed and arranged so
as to receive at least one radiation source and expose
transcutaneously a designated portion of the organ from at least
two dwell positions; and controlling the dwell time of the
radiation source at each of the dwell positions placed via the
applicator at or near the periphery of the organ such that the
diverging exposure field from each dwell position is
superpositioned on the diverging exposure field from other dwell
positions to deliver a therapeutic dose to a targeted volume within
the organ.
5. The method of applying brachytherapy to a designated volume
within a protruding organ: using image guidance to locate the
designated volume; placing on the organ a non-invasive applicator
with at least one radiation source so that the designated volume
can be exposed transcutaneously for a predetermined dwell time for
each of at least two dwell positions at or near the periphery of
the organ; and controlling the dwell position and the dwell time of
the radiation exposure at each of the dwell positions such that the
diverging exposure field from each dwell position is
superpositioned on the diverging exposure field from other dwell
positions to deliver a therapeutic dose to the designated volume
and a sub-therapeutic dose to other tissue adjacent the designated
volume.
6. The system for applying brachytherapy to a designated volume
within a protruding organ: an imaging system for defining the
designated volume; a non-invasive applicator with at least one
radiation source constructed to be placed on the organ so that the
designated volume can be exposed transcutaneously for a
predetermined dwell time for each of at least two dwell positions
at or near the periphery of the organ; and control the dwell
position and the dwell time of the radiation exposure at each of
the dwell positions such that the diverging exposure field from
each dwell position is superpositioned on the diverging exposure
field from other dwell positions to deliver a therapeutic dose to
the designated volume and a sub-therapeutic dose to other tissue
adjacent the designated volume.
7. A method of applying radiotherapy to a protruding organ,
comprising: A. Compressing the protruding organ between two plates
so as to define the initial treatment plane; B. Imaging the
protruding organ in the initial treatment plane while it is
immobilized to identify the designated volume of tissue in need of
radiotherapy; C. Delivering radiotherapy to the designated volume
while the protruding organ is immobilized from a direction within
an angle of 30 degrees from normal to the initial treatment plane;
D. Removing the compression plates and rotating the compression
plates to a new orientation which is within 60 to 120 degrees of
the initial treatment plane, and re-applying compression to
immobilize the said protruding organ at the new orientation; E.
Identifying the designated volume by imaging, or other means,
within the protruding organ from the new orientation; F. Delivering
radiotherapy to the designated volume while the protruding organ is
immobilized in the new orientation from a direction substantially
normal to the compression plates; G. Repeating steps D to F, as
needed until a therapeutic dose is delivered to the designated
volume within the protruding organ.
8. The method of claim 7, where the protruding organ is the
breast.
9. The method of claim 8, wherein the breast has been subjected to
a lumpectomy procedure and wherein the designated volume is the
lumpectomy cavity margin.
10. The method of claim 7, comprising the means of compression,
imaging and delivering radiation therapy are performed with a
single apparatus.
11. An apparatus for applying radiotherapy to a protruding organ,
comprising: A. a pair of plates constructed and arranged so as to
compress the protruding organ and define an initial treatment
plane, wherein the compression plates are adapted to rotate to at
least a second orientation, and re-applying compression to
immobilize the said protruding organ at the new orientation; B. an
imaging device constructed and arranged so as to image the
protruding organ in the initial treatment plane while the organ is
immobilized and so as to identify the designated volume of tissue
in need of radiotherapy, and identify the designated volume in the
second orientation; C. a radiation delivery system constructed and
arranged so as to deliver radiotherapy to the designated volume
while the protruding organ is immobilized from a direction within
an angle of 30 degrees from normal to the initial treatment
plane.
12. The system according to claim 11, wherein the second
orientation is within 60 to 120 degrees of the initial treatment
plane.
13. The system according to claim 11, where the protruding organ is
the breast.
14. The system according to claim 13, wherein the breast has been
subjected to a lumpectomy procedure and wherein the designated
volume is the lumpectomy cavity margin.
15. A system for applying non-invasive brachytherapy to a targeted
volume within a conformable protruding organ of a patient,
comprising: an applicator constructed so as to be positioned
relative to the organ so that an enhanced dose of divergent
radiation is deliverable from at least two locations at or very
near the periphery of the conformable protruding organ
transcutaneously to the targeted volume of the conformable
protruding organ from at least two directions so that a higher dose
is delivered to the targeted volume than to tissue surrounding the
targeted volume; treatment planning program used to guide the use
of the applicator; and an image guidance device constructed and
arranged so as image the targeted volume wherein the treatment
planning program and image guidance device is sued to determine the
optimum treatment plan.
16. A system according to claim 15, wherein the treatment planning
program includes parameter determination subprogram configured and
arranged so as to determine radiation exposure parameters including
isodose center, dose volume and dose uniformity as a function of
the designated dose and dose distribution with the size and shape
of the protruding organ and the location and extent of the targeted
volume, as identified from the image guidance device.
17. A system according to claim 16, wherein the treatment planning
program includes a subprogram configured and arranged so as to
determine the position, intensity, size shape, and energy of one or
more sources for providing the enhanced dose as a function of the
targeted volume, which in turn is determined by the size and shape
of the organ, or the size and shape of the designated volume
identified from the image guidance device.
18. A system according to claim 17, wherein the treatment planning
program includes a subprogram configured and arranged so as to
determine the dwell position, swell patter, and dwell time, of one
or more sources for providing the enhanced dose coincides with the
targeted volume.
19. A system according to claim 15, further including image markers
arranged to align the position of the applicator to coordinates of
the organ to coincide radiation treatment with the targeted
volume.
20. A method of applying non-invasive brachytherapy to a targeted
volume within a conformable protruding organ of a patient,
comprising: positioning an applicator positioned relative to the
organ so that an enhanced dose of divergent radiation is
deliverable from at least two locations at or very near the
periphery of the conformable protruding organ transcutaneously to
the targeted volume of the conformable protruding organ from at
least two directions so that a higher dose is delivered to the
targeted volume than to tissue surrounding the targeted volume;
using a treatment planning program to guide the use of the
applicator; using an image guidance device to image the targeted
volume so as to determine the optimum treatment plan.
21. A method according to claim 20, wherein using the treatment
planning program includes determining radiation exposure parameters
including isodose center, dose volume and dose uniformity as a
function of the designated dose and dose distribution with the size
and shape of the protruding organ and the location and extent of
the targeted volume, as identified from the image guidance
device.
22. A method according to claim 20, wherein using the treatment
planning program includes determining by the size and shape of the
organ, or the size and shape of the designated volume identified
from the image guidance device; and determining the position,
intensity, size shape, and energy of one or more sources for
providing the enhanced dose as a function of the targeted
volume.
23. A method according to claim 20, wherein using the treatment
planning program includes determining the dwell position, swell
patter, and dwell time, of one or more sources for providing the
enhanced dose as it coincides with the targeted volume.
24. A method according to claim 20, further including using image
markers arranged to align the position of the applicator to
coordinates of the organ to coincide radiation treatment with the
targeted volume.
Description
RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 11/354,620, filed Feb. 15, 2006, which is a non-provisional
application of U.S. Provisional Application No. 60/653,191, filed
Feb. 15, 2005. Each of the above-mentioned applications is
incorporated herein by reference in its entirety as though fully
set forth herein.
FIELD OF DISCLOSURE
[0002] The disclosure generally relates to brachytherapy, and more
specifically to non-invasive devices for and methods of providing
peripheral brachytherapy to protruding organs.
BACKGROUND OF THE DISCLOSURE
[0003] Various forms of brachytherapy have been practiced since the
time of discovery of radioactivity by Mme. Curie. Brachytherapy,
from the Greek root meaning "from a short or near distance" is a
term typically used to describe the placement of one or more
radioactive sources within tissue or in a body lumen or body cavity
to deliver a therapeutic dose to a tumor or tumor bed near the
source. Brachytherapy as it is practiced today includes several
varieties of invasive treatment. Interstitial brachytherapy
includes the step of placing the radioactive source or sources
within the tissue (e.g. prostate gland). Intra-luminal
brachytherapy includes introducing the source through an anatomical
lumen (e.g. vascular). Intra-cavitary brachytherapy is performed by
placing the radioactive source inside a naturally occurring cavity
near the cancerous tissue (e.g. cervical cancer, or orbital cavity
for intra-ocular melanoma), or a man-made cavity created during
surgery (e.g. breast lumpectomy or other tumor beds). Various
brachytherapy applicators are known and used in invasive
procedures.
[0004] A surface applicator, including structure for defining a
series of parallel lumens for receiving high dose radiation (HDR)
sources, has been used for treatment of surface lesions, skin
cancer or during open surgeries for tissues which are easily
accessed. (See, for example, the Varian catalog at
www.varian.com/obry/pdf/vbtapplicatorcatalogue.pdf, page 113). This
applicator is not designed to treat a deep seated tumor or tumor
bed, however.
[0005] Cash et al. (U.S. Pat. No. 6,560,312) discloses a technique
of performing radiosurgery on a human body using teletherapy. The
technique includes accumulating non-converging radiation fields to
reach a therapeutic dose. The teletherapy design of Cash et al. is
based upon a predetermined distribution of remote x-ray sources to
create a volume where multiple beams intersect within the human
body. It relies on the ability to align remote sources located on
one platform to treat a lesion within a patient who is positioned
on a separate platform. This approach has major limitations where
relative positioning of the sources must be carefully maintained in
order to provide precise lesion tracking, particularly when patient
motion, such as that associated with breathing, can cause
misalignments during treatment (as for example, when the patient is
being treated for breast cancer).
[0006] Sundqvist (U.S. Pat. No. 4,780,898) and Leskell (U.S. Pat.
Nos. 5,528,651, 5,629,967 and 6,049,587) collectively describe a
teletherapy system sold under the trademark "GammaKnife", and
assigned to Elekta Instrument AB. The system is used to treat
inoperable fine brain tumors by exposing a localized point within
the brain of the patient. Gamma Knife relies on rigidly
immobilizing the head of a patient by attaching a "helmet" directly
to the skull, and simultaneously exposing the brain tissue to
sources of radiation from multiple angles. Each source is
collimated, emitting converging radiation beamlets that target a
single focus point. By careful alignment of each of the source
beamlets or lines of treatment, the Gamma-Knife system is able to
build up the radiation field to therapeutic levels at the location
of the target. The design is useful for treatment of very fine
(point) lesions and requires careful orientation of each beamlet or
line of treatment.
GENERAL DESCRIPTION OF THE DRAWINGS
[0007] In the drawings:
[0008] FIG. 1 is a perspective view of one embodiment of an
applicator used for brachytherapy treatment of the breast in
accordance with the principles described herein;
[0009] FIG. 2 is a cross section taken through the cup of the
applicator shown in FIG. 1 and supporting the breast under
treatment;
[0010] FIG. 3 is a perspective view of another embodiment of an
applicator used for brachytherapy treatment of the breast in
accordance with the principles described herein;
[0011] FIG. 4 is a cross section taken through the cup of the
applicator shown in FIG. 3 for supporting the breast under
treatment;
[0012] FIG. 5 is a cross section of a portion of an applicator
including attenuators having embedded sources to facilitate
directional delivery of radiation from each of the sources;
[0013] FIGS. 6A-6D illustrate an embodiment of a sequence of steps
for providing brachytherapy to the breast using a parallel plate
applicator and a dedicated imaging mammography system;
[0014] FIG. 7 is a cross-section of an example of a dose map
overlaid onto a CT image from a prototype bra-style applicator
mounted on a phantom to show the isodose distribution to the breast
using a "lampshade" style HDR catheter pattern;
[0015] FIGS. 8A-8B illustrates an example of finite element
analysis (FEA) of the field distribution from a single field
shaping cell of an applicator, and a series of field shaping cells
placed within the top and bottom plates of a typical parallel plate
applicator, respectively;
[0016] FIGS. 9A and B represents a typical program flowchart
indicating primary calculations to be performed, major inputs (both
static and dynamic) and major decision making paths in a typical
treatment sequence;
[0017] FIG. 10 is an illustration of multiple field shaping cells
used to control the relative dose of radiation to the skin vs. dose
to the center of the target volume;
[0018] FIGS. 11A and B illustrate two examples of the orientation
of the field shaping cells used to control the exposure of tissues
to radiation;
[0019] FIG. 12 is a perspective schematic view of an example of a
continuous field shaping cell;
[0020] FIG. 13 is a perspective schematic view of an example of a
single conical field shaping structure/cell;
[0021] FIG. 14 is a perspective schematic illustration of an
example of an applicator using a robotic arm; and
[0022] FIGS. 15A-C are cross-sectional views showing the effects of
positioning a source within a field shaping structure on the
divergent shape of the radiation pattern emitted from the field
shaping structure.
DETAILED DESCRIPTION OF THE DRAWINGS
[0023] The devices and methods described in this disclosure are
particularly suitable for treatment of a large, designated or
targeted volume (on the order of a few to tens of cubic cm, or
greater) within a protruding organ, such as a breast, testicle, or
penis. In one embodiment the devices and methods require one or
more divergent beams or patterns of therapeutic radiation from one
or more radiation sources placed within an applicator supported
relative to the surface of a protruding organ. It should be
understood that as used herein, reference to a "source" or
"sources", in each instance, can mean either a single source
adapted to be configured and/or moved so as to radiate in more than
one direction toward the targeted volume, or a distribution of two
or more sources similarly adapted to be configured so as to radiate
in more than one direction, so as to concentrate more of the total
exposable radiation in the targeted volume, than in the surrounding
tissue. The applicator is affixed relative to the organ for each
exposure by the source or sources, and provides a stable platform
for receiving the radiation source and delivering the dose to the
designated volume independent of target movement (e.g., due to
breathing cycle). The definition of a designated volume as well as
the relative positioning of the source or sources in the applicator
can be correctly identified by imaging guidance techniques for
proper alignment and monitoring of the delivered dose. In one
application, the source(s) must be positioned within a narrow range
of distances from the skin. Placing the source(s) too close to the
skin (e.g., less than about 3 mm) can cause excessive skin
exposure; while placement farther than a few cm (e.g., 5 cm) away
from the skin can result in the intensity of the dose falling off
and the brachytherapy becoming inefficient, and therefore
insufficient and ineffective. By proper source placement(s)
relative to the targeted volume during treatment, multiple
divergent beams can be directed to overlap or intersect solely in
the targeted volume. This, in turn, results in the exposure fields
being superpositioned within and thus provide the therapeutic dose
to the targeted volume, while the portion of the volume that is not
exposed to the intersection of the divergent beams receives a
sub-therapeutic dose.
[0024] The disclosure also describes the design and utilization of
a non-invasive brachytherapy technique where a distributed
radiation source pattern is created by using one or more sources.
The source or sources can include, but not limited to, one or more
isotopes, one or more discrete sources, and/or one or more
generators of ionizing radiation. During treatment, the portions of
a single source or the multiple sources that provide the
therapeutic dose are preferably distributed in or sequentially
moved to predetermined fixed positions at a close predetermined
distance to the skin around a protruding organ, and moved and/or
arranged so that a prescribed therapeutic dose is delivered to the
targeted tumor or tumor bed within the organ. Imaging guidance is
preferably, but not necessarily, used to locate and define the
designated target volume within the organ to which the radiation
will be delivered. The prescribed dose delivered to the designated
volume can be determined, for example, by calculating the total
cumulative or sum of the superpositioned lower doses respectively
delivered to the designated volume from the distributed positions
arranged around the targeted tissue. Alternatively, computer
simulation techniques can be employed to determine the
superpositioned or superimposed (cumulative) dose delivered to the
desired volume taking into account the shape, size, volume of the
designated targeted tissue and its location and distance from the
skin.
[0025] A protruding deformable organ, such as the breast, offers a
unique geometry for radiation therapy from the periphery. It allows
a non-invasive applicator to be designed (and accordingly
facilitate a procedure for treatment) such that the applicator may,
in the case of a breast, for example, modify the shape of the
breast, and allow a source or sources of radiation to surround, or
be positioned at two or more locations at the periphery of the
organ, so as to allow for a pattern of overlapping, intersecting
beams of diverging radiation from two or more directions/angles to
increase the cumulative dose to the inner targeted tissue, or
designated volume, within the organ, and fix the distance of the
source(s) at each of the locations from which each beam of
diverging radiation is directed. This overlap within the designated
volume allows the source, or each of the plurality of sources, to
deliver lower average doses to the intervening tissue from each of
a plurality of positions, while delivering a higher dose to the
targeted tissue than otherwise provided when only a single source
of radiation is used. Thus, the approach disclosed herein, which in
the case of the treatment of breast cancer we term the Peripheral
Brachytherapy of the Breast (PBB) concept, has the benefit of
limiting the dose to untargeted, otherwise healthy, tissue facing
each radiation source location. This is not possible with
teletherapy sources or beams of radiation available from
conventional radiotherapy. The limited penetration from the
radiation source(s) advocated in this disclosure along with the
geometry of and the relative proximity of the applicator combine to
limit the doses to the underlying, adjacent, otherwise healthy
tissues surrounding the targeted tissue, while delivering a
therapeutic dose to the targeted volume within that organ. The
higher dose can be created by various means, all of which involve
effectively surrounding (or at least positioning at select
locations around the periphery of) the deformable protruding organ.
The source(s) are preferably positioned in three-dimensional space
so that the source at each position is a predetermined, relatively
fixed position from the targeted volume, and the fields generated
at each source location constructively add within the targeted
volume, thus, collectively producing the therapeutic dose levels at
that location. A source may be placed at each of several of the
locations at the same time and/or a source may be moved to each of
several positions over time during treatment. This disclosure
contemplates that the source or sources of radiation provide point
sources (substantially one dimensional), line (not necessarily
straight) sources (two dimensional) and/or broad planar (not
necessarily flat, but extending in three dimensions) sources so as
to create the overlapping radiation pattern that provides
accumulated dose at the targeted volume. The radiation source(s)
can include, but are not limited to, radioisotopes or generators of
ionizing radiation (x-ray or electron sources).
[0026] The embodiments of the method and system disclosed herein
are particularly useful for brachytherapy of a breast carcinoma
following a lumpectomy where the cancerous breast tissue has been
surgically excised, although it should be appreciated that other
applications can be provided without undue experimentation.
Following a lumpectomy, to prevent local recurrence, there is a
need to expose the tumor bed to radiation to "sterilize" the field
and destroy pre-cancerous micro-inclusions that may still exist
near the original site that would otherwise result in a local
failure. Typical brachytherapy doses delivered to the breast
following lumpectomy have ranged from about 10Gy to about 50Gy. The
specific dose depends on the dose rate, fractionation schedule and
the duration of therapy, nature of the original growth, mono versus
boost therapy, as well as host of other factors which will be
evident to one skilled in the art. A typical target for partial
breast brachytherapy is a volume extending from about 2 cm beyond
the lumpectomy (excision cavity) margin. Using the presently
disclosed Peripheral Brachytherapy of the Breast (PBB) concept, one
can deliver a sub-therapeutic dose to substantially the entire
breast and a therapeutic dose to the target volume within the
breast. The prescribed therapeutic dose to the typical designated
volume of the breast is usually in the range from about 15Gy to
about 40Gy. The therapeutic dose depends, among other factors, on
the duration of radiotherapy, where the shorter the duration of
radiotherapy the lower the dose. The primary alternative (the
current "standard of care") is total breast irradiation by an
external beam that is typically delivered in 5 to 7 weeks with
daily doses of about 1.8Gy, for a total dose of about 45Gy.
[0027] Generally accepted practice is that radiation therapy for
breast cancer is expected to be completed within 60 days, which is
the maximum expected duration for the PBB approach, although the
period could vary beyond 60 days. More typically, using the PBB
approach, the treatment is expected to be delivered from about 2
days to about 10 days.
[0028] In accordance with the disclosed system and technique,
peripheral breast brachytherapy can be performed with the patient
in any one of many different positions. The patient may be treated,
for example, while lying in a supine or prone position. In the
prone position, special tables may be used. The tables can each
include, for example, a properly positioned hole or aperture for
receiving the breast, so the breast can hang freely by the force of
gravity. Alternatively, the patient may be treated while standing
up or sitting down. The organ, especially when treating the breast,
may be conformed, or fitted within a confined space so as to ensure
a fixed relationship between the position of the target volume and
the position(s) of the source(s) during treatment. Varying the
patient's orientation or movement of the target volume during
treatment, relative to the source(s) relative to the treatment and
imaging system, or movement of the target volume relative to the
source(s), will impact the ability to target and treat certain
predetermined volumes within the breast, as well as increase stray
doses to other organs and tissue. Thus, the positioning and
orientation of the patient, and whether the breast is confined
during treatment may actually depend in part on the location of the
targeted volume.
[0029] For treatment of a conformable protruding organ like the
breast, the source(s) of radiation can be placed in a special
applicator. The applicator, when supported relative to a
conformable organ, will preferably fix the shape of the organ
relative to the source(s) during treatment, and provide a stable
platform that delivers a constant radiation field independent of
the body motion generally, or organ motion specifically, due, for
example, to the breathing cycle. The applicators can be designed to
either conform to the shape of, or surround, the protruding organ
thus allowing for the secure placement of the source(s) at the
periphery of the organ in close proximity to its surface.
Alternately, the applicators may include a cavity for receiving the
organ, and may be made of a rigid material and rigid geometry such
that the protruding organ is forced to take the shape of and thus
conform to the shape of the cavity within the rigid applicator. The
applicators further preferably include cells, pockets, recesses,
and/or lumens for the insertion and movement and/or attachment of
each source of radiation at the prescribed positions of
treatment.
[0030] Compression plates are commonly used in mammography
procedures. The compressed breast presents a flat uniform tissue
mass and is easier to radiographically image for identification of
calcification or cancerous lesions. Similarly, compressed breast
tissue presents a more uniform target for radiotherapy. The present
disclosure includes a method of compressing the breast between two
plates to present a uniform mass for imaging and radiotherapy. In
particular the orientation of the compression can be altered to
image and irradiate tissue from different angles. The compression
of the breast tissue , due to its deformable nature, causes the
organ to spread laterally and thus can reduce the amount of normal
tissue between the treatment plates and the designated volume. This
can cause the dose to the normal tissue of the breast to be
substantially reduced. Two orthogonal compression plate
orientations or a plurality of compression plate orientation angles
can be used to perform imaging and radiotherapy. In the process of
using different compression plate orientations for radiotherapy,
the dose to the designated volume is accumulated while the skin
dose is divided between different points of entry, thus controlling
the skin toxicity. A preferred angle for both radiographic imaging
and radiotherapy is the direction perpendicular to the compression
plate. Imaging at each compression plate orientation allows for
targeting the radiation field to match the designated site.
[0031] An embodiment of the present disclosure is to irradiate the
margins of a lumpectomy cavity. Two compressions of the breast from
two orthogonal planes allow radiotherapy from 2 orthogonal planes
and enables the accumulation of dose to the designated target
without exceeding the toxicity limit of the skin. The apparatus
that can provide compression, image registration and radiotherapy
is part of the disclosure.
[0032] Thus the applicator may take the form of a set of applicator
plates, either of which, or both may include the structure for
housing a source or sources of radiation near the surface of the
protruding organ. These plates are preferably disposed parallel to
one another and may be used to compress the protruding organ. The
plates may also be curved such that they are designed to conform to
the general shape of the organ so as to reduce any discomfort for
the patient, yet still be able to press against the organ so as to
compress the organ into a desired shape, and fix the targeted
volume relative to the source(s) positions during treatment.
Further, the applicators can include an elastic, flexible or
pliable structure for conforming to the organ and keeping the
applicator in intimate contact with the organ to deliver a constant
and consistent dose from prescribed directions and distances to the
targeted volume. An additional function of the applicator may
include lifting and separating the protruding organ from the
neighboring parts of the body so as to minimize stray radiation
doses into those neighboring parts. The applicator is preferably
placed in contact with, or communication to, the surface
(periphery) of the protruding organ which is being treated so as to
fix the source(s) relative to the target volume at each treatment
position. As a result, unlike conventional teletherapy approaches,
the delivery of radiation to the organ is unaffected by the motion
of the patient, such as motion associated with breathing.
[0033] To minimize stray radiation doses (doses to any other
untargeted tissue, organ or person), the applicator may
additionally include an attenuating or shielding outer layer.
Typical attenuating and shielding layers are made of high atomic
number, dense materials, but the specific selection of the
attenuating material will depend upon the particular organ,
radiation source and treatment plan. The applicator may include an
inner layer designed for direct contact with the skin which can
control the distance of the radiation source from the skin. The
thickness of such an inner layer should reduce the intensity of the
skin dose for that portion of the organ facing the radiation
source. The inner layer may also include high water content, and
may include a water filled sponge and/or gel media or
water-equivalent materials.
[0034] Additional attenuating materials, apertures and structures
may be incorporated into the applicator such that they provide
structure for controlling and thus determining the direction(s) of
the exposure field. These field-shaping structures may include, for
example, masks, bands and/or sheaths of attenuating material, or
grooves within an attenuating material into which the sources are
placed. The structures can also be made of field shaping cells for
receiving radiation source material. The field shaping cells may be
designed in such a way as to limit the side exposure while
providing the full exposure of, and thus define the shape of the
beam of radiation that is used to expose the tissues directly in
front of the cell or set of cells. The design of these cells
(including the height, aspect ratio, attenuator material,
attenuator thickness) thus can be used to selectively shape the
radiation exposure field. Where HDR applicators are used, the
field-shaping cells may be included and preferably placed along the
path of the HDR lumen(s) so as to coincide with the dwell positions
of the sources.
[0035] Patient positioning and image guidance are important to
precisely target radiation to a designated volume within a
protruding organ. In the case of a breast, various imaging methods
including, for example, x-rays (such as mammography or CT
scanning), ultrasound, fluoroscopy, MRI, and portal imaging, may be
used for imaging the tumor or tumor bed and determining the
radiation targets. Similarly, different radiographic or ultrasonic
fiducials, such as implantable markers, skin tattoos and contrast
media are commonly used to mark the tumor bed (the margins of a
lumpectomy cavity). Image guidance is usually of vital importance
for radiotherapy of the breast as the breathing cycle presents a
moving target. The present disclosure describes an embodiment
designed so as to (a) facilitate the positioning of radiation
source(s) in an applicator that is/are mounted to the breast and
(b) deliver constant radiation to the designated volume within the
breast independent of the breast tissue movement during the
breathing cycle.
[0036] The applicators may include one or more markers to
facilitate alignment of the applicator with either the protruding
organ or the imaging system. The applicator markers are preferably
designed so as to be visible by any one or several common imaging
technologies (depending on the one used in a specific application).
Further, the markers may be tracked by dose planning software to
act as an aid to the precise targeting of the radiation field.
[0037] In one embodiment the applicator bra may include channels,
lumens or enclosures for receiving larger source(s). For example,
as shown in FIGS. 1 and 2 a bra 20 including support straps 22, the
bra 20 includes one or more compartments 24 formed between an inner
layer 26 and outer layer 28, and constructed to receive one or more
radiation sources 30. The sources can be planar, line or point (or
similar structures) sources, as previously mentioned. The
configuration of each compartment 24 may vary according to the size
of the breast and the size, shape and distance below the skin of
the target tissue. In this embodiment the source can be
incorporated into a plate, foil, fabric, sheet, wire or point (or
other structure) source (a foil being shown in FIG. 2), suitably
treated so as to provide the necessary radiation pattern. The outer
layer 28 should be constructed to attenuate X-rays, while the inner
layer, contacting the skin should be transparent to X-rays.
Alternatively an X-ray absorbent plate, sheet, foil or similar
structure can be included within each compartment between the
source and the outer layer 28.
[0038] In the case of the breast, the applicator may be in the form
of a brassier, cup or a pouch. In one embodiment of the current
disclosure the applicator may be constructed to receive source(s)
(such as the bra or brassiere 40 as shown in FIGS. 3 and 4). The
bra 40 facilitates treatment of a breast compatible with an HDR
afterloader. The bra includes a pair of cups 42 for supporting the
breasts and supporting straps 44 so that the bra can be comfortably
worn by the patient when in use. The cup 42a used to support the
breast under treatment also includes separate internal lumen(s) or
compartment(s) 46 for receiving source(s) 48. In the embodiment of
the applicator shown, the lumen is adapted to receive a carrier
supporting one or more sources. The carrier is preferably, although
not necessarily a catheter 50 onto or into which at least one
source is attached or inserted. As best seen in FIG. 4, the cup 42a
includes at least one outer layer 52 and at least one inner layer
54, defining the lumen(s) or compartment(s) 56 there between. The
lumen or compartment shown in FIGS. 3 and 4 has a spiral
configuration. It should be understood that the configuration of
the lumen(s) or compartment(s) can assume other configurations and
geometric shapes to accommodate the source(s). The patterns of the
channels, lumens and enclosures may vary according to the size of
the breast and the size, shape and distance below the skin of the
target tissue. Typical patterns for the lumens would include, for
example, substantially straight or curved channels extending in
predetermined directions, such as form the base toward the tip of
the cup, spiral(s), multiple concentric circles of increasing
diameter or a series of lumens which outline a cone or a truncated
cone (i.e., frusta-conical shape) of tissue contained within.
Clearly, the specific configuration of the cup and the sources can
be designed depending upon the particular application and
treatment. In this configuration, the patterns of the lumens as
well as the dwell times for the source will be determined according
to the size of the breast, the size and shape of the designated
tissue within the organ and the position of the target with respect
to the surface of the organ. The outer layer 52 is preferably made
of a shielding material (for example, a fabric containing lead) to
absorb, and therefore reduce or prevent radiation emitting
outwardly from the cup, while the inner layer 54 is preferably made
of a material, such as a fabric that is substantially transparent
to the X-rays so as to allow the X-rays to be propagated through
the inner layer into the targeted volume of the treated patient's
breast. Alternatively, a shielding (X-ray absorbent) plate, sheet,
fabric or material (not shown) made be provided between the outer
layer 52 and the compartment or lumen. In this latter instance the
outer layer need not include an X-ray absorbent material. A
suitable opening or openings are provided for receiving the
source(s) of radiation into the lumen or compartment.
[0039] HDR after loaders useful for inserting the sources, with the
aid of a carrier such for as, for example, a catheter, include
those that have been designed for use with interstitial,
intra-cavitary or intra-luminal brachytherapy. The HDR after loader
system (not shown) typically includes a) a shielded container to
house an intense radioisotope source when not in use, b) a delivery
system to advance the sources from the shielded container through
one or more compartments, channels or lumens, with the aid of the
carrier, e.g., catheters or like structures, in place with respect
to the patient in the desired area of treatment and c) a control
system which monitors and controls the dwell position and time of
the sources within the treatment carrier to assure that the dose
delivered matches the dose prescribed. In the brassier applicator
of the type shown in FIGS. 3 and 4, using the lumens for source
placement, the dose to the underlying tissues is controlled by
adjusting the dwell position and dwell time. Further, in this
embodiment, one or more field shaping cells prepositioned in the
lumen can be used or positioned in relationship to the source(s) so
that they coincide with the dwell positions of the sources.
Alternatively, a continuous aperture along the lumen may be
employed for controlling the dose to a designated volume to reduce
the relative dose to the skin or healthy tissues such as the heart,
lungs or contralateral breast.
[0040] In the case of the present disclosure, it is further
contemplated that there be the option of a control system,
preferably including a computer program arranged so as to control
the dwell position of the source(s) within the lumen(s) of the
applicator.
[0041] The control system preferably will require parametric
inputs, both static and dynamic, which can include geometrical
factors (source size, shape, applicator size and shape and others),
dose prescription factors (dose, dose rate, target tissue and
others), biological factors (target tissue, margins, sensitive
tissue locations and others), source factors (size, shape,
activity, activity distribution) and dynamic factors (patient and
operator readiness, proper mechanical positioning and operation
verification, position telemetry and others) to provide
process/procedure control. The control system may also include
options for user intervention, overrides, monitoring, and
reporting.
[0042] A computer program may be used in the treatment planning
process. This program will offer the option of (a) defining the
dose distribution to the protruding organ, or to a designated
targeted volume within the organ, and (b) determining an
appropriate distribution of source(s), field shaping cells and/or
dwell times along the periphery of the organ. The computer program
could also allow the user to define the source(s) and/or field
shaping cells and their locations, and calculate the dose
distribution within the organ. In any case, the program may accept
one or more of the following parametric inputs: the number, type,
species, intensity, shape, activity distribution, size, etc. in
determining the required placement of, or resulting dose
distribution from the sources. Further, the number, type and
characteristics of field shaping cells, if used, may be included in
the determination. The treatment planning software program may
include the option of enabling the alignment of the coordinate
systems of the treatment planning software with that of the
protruding organ, applicator or imaging system. The use of the
markers on/within the applicator along with either reference
anatomical landmarks or applied imagable markers on or within
either the protruding organ or the applicator may be used by the
program to facilitate the overlay of the coordinate systems of the
software program and one or more of the following: the organ, the
applicator and the imaging system. Alternately, the position of the
target tissue may be determined by an imaging modality that is
directly incorporated into, or in communication with, the treatment
system that provides input data to the computer program.
Multidimensional images of the organ and associated structures may
be imported by the software program to facilitate this alignment.
Options to calculate the placement of sources based on a
combination of dose to the designated volume and a dose limitation
to neighboring organs or tissues may be included. The software
program may also include the option of real-time feedback on dose
delivered to the targeted tissue where the future source positions
and dwell times are recalculated as often as desired based on the
historical dose delivery feedback.
[0043] The radioisotope(s) may be transmuted within the source
carrier (e.g. by direct nuclear activation) or may be dispersed
into, or applied to, the surface of carriers by any number of
chemical or physical methods, simple adhesion or encapsulation.
Examples of some of the more common methods include the processes
of plating, painting, sputtering, reaction bonding, encasement of
radioisotope dispersion within a polymer and the like. Other
methods may also be employed.
[0044] The radionuclide(s) of the source(s) could be chosen from
the list of commonly recognized and/or available radionuclides. The
ideal isotope has the right combination of half-life, gamma ray
energies and ease of production and purification. The half-life has
an impact on the shelf life of the product. The x-ray or gamma ray
(photon) energies control the depth of the field for dose delivery
and may be optimized such that it matches the volume and location
of the tumor bed. Higher energy photons are better for more deeply
seated targets. Finally, the radionuclide must be chosen among
available or easily producible species. The primary current options
for radioisotopes capable of meeting these requirements include,
but are not limited to Co-56, Co-57, Co-58, Co-60, Zn-65, Pd-103,
Cd-109, 1-125, Cs-131, Cs-137, Sm-145, Gd-153, Yb-169, W-187,
Ir-192, and Au-198, though other sources can, and in the future
may, meet these criteria. To treat organs of the general size as
defined in this application, the energy of the primary photon
emissions should be limited to the range of between about 20 KeV
and about 1500 keV. For the breast, the energy of the primary
emissions of preferred sources are preferably generally between
about 50 keV and about 1300 keV.
[0045] The radioactive source(s) contemplated in this disclosure
can be generators of ionizing radiation, delivering a diverging
exposure field, such as x-ray sources or electron sources that can
be placed peripheral to the protruding organ. An example of the
radiation source is an orthovoltage x-ray source. The dwell
position of the generators and the intensity of the emissions can
be controlled to deliver the desired therapeutic dose to a target
volume within a protruding organ as a result of the superposition
of the fields from the individual source dwell positions. Field
shaping structures, as described earlier, can be added to the
generators to shape the exposure field.
[0046] The current brachytherapy applicator is different from
previous applicators as it is suitable for treatment of a large
designated volume within a protruding organ. It requires at least
one divergent beam from at least one radiation source placed within
an applicator mounted on the surface of a protruding organ. The
applicator is affixed to the organ and provides a stable platform
for receiving the radiation source(s) and delivering the dose to
the designated volume independent of the target movement (e.g., due
to the breathing cycle). The designated volume as well as the
applicator are initially identified by imaging guidance for proper
alignment and monitoring of the dose. The source must be within a
narrow range of distance from the skin. Placing the source too
close to the skin (less than about 3 mm) results in excessive skin
exposure; while placing the source farther than about a few cm
(e.g., 5 cm) away from the skin results in the intensity falling
off, the range of allowable frontal exposure angles being
restricted and the brachytherapy becomes inefficient. The overlap
of the divergent beams where the exposure fields are
superpositioned provides the therapeutic dose while the portion of
volume that is not exposed to the intersection of the divergent
beams receives a sub-therapeutic dose.
[0047] It should be appreciated that the distributive effect can be
achieved by a single extended or multiple segmented sources and
single or multiple field shaping cells. In the case of a single
extended source, the single source is configured to extend over an
area so as to radiate from different directions or angles toward
the targeted tissue or designated volume such that the radiation
field from one portion of the source is superpositioned upon the
field generated from other portions of the same source so as to
constructively overlap and provide the desired dose to the targeted
tissue or designated volume. By creating a proper radiation
pattern, the method and product allow for a higher concentration of
radiation to be delivered non-invasively to the targeted tissue or
designated volume than a source which delivers radiation from a
single point source or from a source where radiation is emitted at
one position (a planar or a line source), while reducing the
exposure of surrounding tissue to incidental radiation.
[0048] FIG. 5 shows an example of embedded field shaping structure
(with one or more apertures) within an applicator to facilitate
directional delivery of radiation, and achieve the desired overlap,
or superposition, of radiation patterns in predetermined volume of
interest. As seen in the drawing, the illustrated embodiment
includes attenuating material that is preferably a part of the
applicator. The attenuating material 70 is preferably provided with
a plurality of channels 72 within the attenuator. The source(s) 74
are preferably embedded in the respective channels so as to form
directional diverging beam patterns 76. The source(s) 74 are
positioned relative to the target area 78 so that the patterns 76
overlap each other in the target area 78 so that so that a higher
dose of radiation is delivered to the target area 78 than the
surrounding areas.
[0049] FIGS. 6A-6D show the elements of a non-invasive peripheral
breast treatment using a parallel plate applicator approach. FIG.
6A shows the initial imaging of the breast using a standard
mammographic technique. In FIG. 6B, the location, size and shape of
the lesion 80 are converted to a treatment plan involving treatment
from two substantially orthogonal directions 82 and 84, any where
from 60 to 120 degrees from the original orientation. Each plate
can define a plurality of individual source locations (as
illustrated for example in FIG. 8B). In FIG. 6C the first treatment
is delivered by a series of HDR source dwell positions within each
of the treatment applicators the direction 84. In FIG. 6D, the next
treatment fraction is provided at a 90 degree angle with respect to
the first treatment fraction in the direction 82. Additional
treatment fractions would be performed until the entire therapeutic
dose to the target tissue is achieved. In one embodiment, the
follow steps are followed in order to apply radiotherapy to a
breast. The method of application comprises: [0050] A. Compressing
the breast between two plates so as to define the initial treatment
plane; [0051] B. Imaging the breast in the initial treatment plane
while it is immobilized to identify the designated volume of tissue
in need of radiotherapy; [0052] C. Delivering radiotherapy
divergent radiation to the designated volume while the breast is
immobilized from a direction within an angle of 30 degrees from
normal to the initial treatment plane; [0053] D. Removing the
compression plates and rotating the compression plates to a new
orientation which is within 60 to 120 degrees of the initial
treatment plane, and re-applying compression to immobilize the said
protruding organ at the new orientation; [0054] E. Identifying the
designated volume by imaging, or other means, within the protruding
organ from the new orientation; [0055] F. Delivering radiotherapy
to the designated volume while the protruding organ is immobilized
in the new orientation from a direction substantially normal to the
compression plates; and [0056] G. Repeating steps D to F, as needed
until a therapeutic dose is delivered to the designated volume
within the protruding organ.
[0057] It should be apparent that while the embodiment described in
connection with FIGS. 6A-6D employ two orientations of the
compression plates, the technique could employ more than two
orientations, depending on the application and/or desired
treatment.
[0058] FIG. 7 illustrates an example of a cross-sectional isodose
map overlaid onto a CT image from a prototype brassier-style
applicator mounted on a phantom 121 to show the isodose
distribution generated by an HDR source pattern. That portion of
the source dwell positions along the periphery of the breast which
fall in this plane are highlighted as points 120. The isodose
contours 122 indicate a typical uniformity pattern that can be
generated from this source distribution structure.
[0059] FIGS. 8A and 8B illustrate an example of using finite
element analysis (FEA) of the field distribution from a single
field shaping cell in FIG. 8A, and a series of field shaping cells
placed within the top and bottom plates of a parallel plate
applicator in FIG. 8B. In FIG. 8A the 2-dimension field
distribution can be determined by finite element analysis for a
field shaping cell. In the example shown the cell has an included
angle of 90 degrees and a lead attenuator thickness of 9 mm. The
angle and thickness can clearly vary depending on the particular
circumstances of treatment. This structure creates an unattenuated
frontal radiation exposure field 130 and a substantially attenuated
side exposure field or zone 132. In FIG. 8B, an example of the
impact of this field shaping structure on the 2-dimensional field
uniformity between the plates of a parallel plate applicator is
shown. In this depiction, thirteen HDR catheter lumens 134 are
placed in parallel and spaced 1 cm apart along the top plate 136
and bottom plate 138. The resultant field uniformity is
plotted.
[0060] FIG. 9 is a typical program flowchart indicating primary
calculations, major inputs (both static and dynamic) and major
decision-making paths. As shown in FIG. 9, various user or operator
inputs include dose prescription factors 150, including dose,
duration, dose rate, target volume, and fractionation; geometry
factors 152, including shape of the target volume, size of the
target volume, form of applicator, source locations within the
applicator, source path within the applicator; biological factors
154, including target tissue, margin definition, tissues sensitive
to dose (i.e., any "no" treatment areas); and source factors 156,
including source shape, source activity distribution, source
activity, and source flexibility. The various operator inputs are
provided to the program input of the program path, indicated at
step 160. Step 160 includes calculating the dose per fraction,
dwell times, dwell positions, lumen selection and current dose
rates. The results are then presented to the operator as indicated
at step 162 for confirmation. The operator can override and revise
the calculated dose levels based upon empirical determinations.
Once the dose levels are set, the treatment can commence, as
indicated at step 164. Dynamic inputs relating to the source,
equipment and patient status are then considered (indicated at step
166). These dynamic inputs include patient condition, source
position feedback verification, source movement mechanism, operator
condition, and program error detection algorithm. These dynamic
inputs are provided at step 168 where the source is advanced
(placed) in the starting position, and such positioning is
confirmed. At step 170, the decision is made whether the treatment
at each position is proceeding correctly. This is accomplished by
accessing the state of the target tumor(s) in light of the
treatment carried out so far. If the starting position of the
source cannot be confirmed at step 168, or the treatment is
proceeding incorrectly, the step proceeds to step 172 to an error
handling module which assesses the problem in light of the dynamic
inputs 166. If on the other hand the decision at step 170 is yes, a
determination at step 174 is made whether the prescribed dose has
been attained. If no, step 170 is repeated. If yes, a determination
is made at step 176 as to whether the treatment is in the final
position. If yes, at step 178 the source is removed and a
determination is made as to as to whether the source is safe. If
no, at step 180 treatment is advanced to the next position, and in
turn step 170, and subsequent steps following step 170 are repeated
for the next position.
[0061] Referring again to step 172, once the error handling module
determines the error in treatment, a determination is made at step
182 whether the error can be corrected. If yes, a correction or
repair plan is determined and the treatment parameters revised at
step 184. A determination is made at step 186 as to whether
approval for the revised treatment parameters is needed. If not,
step 180 and the subsequent steps are repeated. If yes and approval
is obtained, at step 188, step 180 and the subsequent steps are
repeated. If no, step 178 and the subsequent steps are repeated.
Finally, at step 178 the source(s) are removed and the source(s)
are verified as safe, reports are produced, as indicated at step
190, and the treatment is ended, as indicated at step 192. It
should be appreciated that many of the procedural steps of the flow
chart described in connection with FIG. 9 can be implemented by
software and stored in suitable memory, such as a CD or ROM of a
computer, and operated by the operator on a desktop, laptop,
workstation or other similar system.
[0062] FIG. 10 is a demonstration of the use of field shaping cells
in combination in a HDR procedure. As the example shown, an HDR
catheter lumen 200 includes one or more field shaping cells 202,
including a HDR source of radiation 204, fixedly attached to or
movable within the catheter lumen 200. As shown, the cell 202 and
source 204 provide a diverging beam of radiation toward the
targeted volume 206. As seen, the field shaping cells can be
prepositioned in the prescribed locations for the desired
treatment. In this instance a single HDR source 204 can be first
advanced so as to move the source 204 through successive cells so
that the source 204 is allowed to dwell for a predetermined time at
a position within the field shaping cell 202 to deliver a
predetermined partial dose from each cell. The process is repeated
by advancing the HDR source 204 to each successive position 210 for
the prescribed time of exposure. The number of positions and
locations is dependent on the particular treatment. Use of field
shaping cells limits the side exposure of the dose to the
surrounding, superficial tissue (adjacent to the skin) while at the
same time allowing accumulation of a larger dose to the
predetermined target volume within that organ.
[0063] FIG. 11 demonstrates how the orientation of the field
shaping cells 216 can be used to control the exposure of tissues to
radiation. In FIG. 11A the field shaping cells 216 are oriented
perpendicular to the chest wall, treating the breast uniformly, but
allowing exposure to positions below the chest wall 217. In FIG.
11B, the field shaping cells 216 are oriented away form the chest
wall and thus minimize the dose to positions below the chest wall
217 so as to create a chest wall sparing orientation.
[0064] The same results are achieved by using a continuous aperture
along the path of the radiation source as show in FIG. 12.
Referring to FIG. 12, an embodiment of a continuous field shaping
structure is shown as including an unimpeded frontal open angle
220, a longitudinal axis 222 the aperture 224, a radiation
attenuator structure 226, such as a catheter containing a radiation
absorption material, the lumen 228 for the radiation source, such
as either the HDR source or the X-ray generator, the surface 230 of
the extended applicator, the surface of the breast 232, the space
234 for the intermediate skin contacting layer between the
applicator and the breast surface and the direction of the
unimpeded frontal exposure 225.
[0065] FIG. 13 shows the elements of an embodiment of a single
radiation field shaping structure 250 for creating a diverging beam
defined radiation exposure field. Structure 250 includes the
radiation absorption material defining an opening 252, preferably
but not necessarily conical in shape, defining a frontal open angle
254 (and defining a half angle 256) and aperture 258, the source
260 positioned relative to the aperture 258 by the height or
set-back distance 262, and an attenuator 264. The beam of radiation
emanating from the source 260 through the aperture 258 is defined
by a centerline or beam axis 266, and thus defines the divergent
frontal exposure field 268 and the side exposure direction/zone
270. Through variation of open angle 254, half angle 256, aperture
258, distance 262, the divergent exposure field emitted from the
field shaping structure 250 can be limited and facilitate the
proper overlap of multiple divergent exposure fields with the size,
shape and location of the lesion within the protruding organ.
[0066] FIG. 14 shows an alternate embodiment of an applicator,
utilizing a robotic based applicator. The radiation source 270 is
mounted on an arm 272, which in turn is mounted in a support 274
and adapted to rotate about a rotation axis 276. In this
arrangement the breast 278 is suitably positioned relative to the
application, as for example, allowed to hang by force of gravity
through an aperture 280 formed in a patient support 282. Shown are
the rotational angle 284, the azimuthal angle 286, source tilt
angle 288, source distance variation 290, height variation 292 and
lateral displacement 294 of the support 274 relative to the breast
278. The rotational angle 284, azimuthal angle 286, source tilt
angle 288, source distance variation 290, height variation 292 and
lateral displacement 294 define the six degrees of freedom, and
operate in concert to allow the PBB technique to properly align the
source(I)(or alternately source and field shaping structure) and
source direction at any point along the periphery of, but at a
close distance to (within the dimensions previously mentioned) or
in direct contact with the breast so as to allow proper tracking or
alignment of the divergent exposure field from the radiation source
with the designated volume 296 within the breast.
[0067] Referring to FIGS. 15A-C, the relationship is demonstrated
between the placement of the source or generator of radiation
within a field shaping structure and the resultant radiation field.
FIG. 15A shows a field shaping structure 298 with a radiation
source 300 placed centered and near the aperture generating a
broadly divergent radiation field 302. FIG. 15B shows a field
shaping structure 298 with the radiation source 300 centered and
near the aperture generating a broadly divergent radiation field
pattern 302. Finally, FIG. 15C shows a field shaping structure 298
with radiation source 300 placed "off-center" and away from the
aperture in the field shaping structure generating a narrowed and
asymmetric divergent radiation field 306.
[0068] Various additional aspects of the disclosed system and
method:
[0069] The applicator can custom designed for single patient use.
For treatment of the breast, the radiation distribution pattern can
be designed so that the dose to the nipple and/or the dose to the
excision site is controlled (reduced or increased) as desired. The
applicator can include radiation monitor(s) to track/measure the
superficial (skin) dose. In those embodiments where the applicator
has an inner skin contacting layer, the space between the surface
of the breast and the applicator provides a controlled separation
distance between the source and the skin. In addition, the inner
skin contacting layer of the applicator can be separable from the
applicator. In one alternative arrangement, the applicator can
include an intermediate layer comprising a high water content or
water equivalent material including, but not limited to a water
filled sponge, balloon or gel media.
[0070] It is envisioned that the primary radioisotope should
include a dominant gamma-ray energy somewhere between about 20 and
about 1500 keV, and preferably dominant energy somewhere between
about 50 and 1300 keV. The radioisotope is preferably selected from
a group including; Co-56, Co-57, Co-58, Co-60, Zn-65, Pd-103,
Cd-109, 1-125, Cs-131, Cs-137, Sm-145, Gd-153, Yb-169, W-187,
Ir-192, and Au-198. In one embodiment the radiation source is an
orthovoltage x-ray source. The dose can be delivered either
continuously or intermittently (by fractions) over a period ranging
from between about 10 minutes to about 60 days. It is also
envisioned that the radiation dose in each fraction is between
about 1 and about 10 Gy and the accumulated dose is in the range of
between about 10 to about 100 Gy. The dose to the designated volume
during each fraction is preferably between about 3.0 and about 4.0
Gy, and a total dose of between about 30 to about 40 Gy delivered
in 8 to 10 sessions over a period of 4-5 days. The non-invasive
brachytherapy can be applied intermittently until the prescribed
fractionated dose is delivered in each session. The non-invasive
brachytherapy described herein can be performed as a boost to other
radiotherapy procedures. For example, the non-invasive
brachytherapy technique can be combined with hyperthermia,
radiation sensitizers or other means of enhancing the effectiveness
of the radiation treatment. It should be evident that the dose and
treatment can vary. Where the accumulated therapeutic radiation
dose delivered is in the range of between about 15 to about 45 Gy,
it is preferred that the average subtherapeutic dose delivered to
surrounding tissue is at least 20% lower than the therapeutic dose.
As previously stated, the source can be applied while the patient
is in a prone position, or in a supine position. Alternatively, the
source can be applied while the patient is sitting or standing. the
applicator contains field shaping structures to allow substantially
unimpeded divergent frontal exposure to the breast tissue while
limiting the side exposure of the superficial breast tissue to
decrease the skin dose.
[0071] The applicator preferably includes field shaping structure
used to create a divergent exposure field. The field shaping
structure, made of a radiation absorptive material, such as lead,
preferably comprises an aperture with an opening angle extending at
least about 20 degrees (half-angle from normal incidence of 10
degrees) but not more than about 150 degrees (half angle from
normal incidence of 75 degrees) reducing the side radiation
exposure (on the average) by at least 30%. In the case of treatment
of the breast, the radioactive source(s) is (are) placed within
side exposure limiting structures of the applicator, such as
suitably shaped apertures so that the axis of the divergent frontal
exposure field is oriented away from the chest wall as to reduce
the stray dose to the heart and lungs. In such an application, the
open angle of the unimpeded frontal exposure is less than about 150
degrees in at least one plane. In the embodiment where a HDR source
is used with the applicator for treatment of the breast, an
extended axial aperture structure is used around the HDR source
axial path to allow the free passage of the divergent radiation in
the frontal direction while limiting side exposure thus reducing
the relative dose to the skin as compared to the designated breast
tissue dose. The depth of an extended axial aperture channel such
as the shown in FIG. 12, can allow the passage of a HDR source and
allow the distance of the HDR source from the aperture channel to
be varied so that the distance will determine the divergence of the
exposure field. Field shaping structures include apertures, masks,
shutters, field shaping cells, bands, grooves, or attenuating
sheaths and spacers of fixed or variable geometries.
[0072] When treatment planning software, such as that described in
connection with FIGS. 9A and 9B, the radiation exposure parameters
such as isodose center, dose volume and dose uniformity are based
on the size and shape of the breast or the size, shape and volume
of the tumor, tumor bed. or a designated volume within the breast.
Preferably, the radiation exposure parameters such as isodose
center, dose volume and dose uniformity are designed to match the
designated dose and dose distribution with the size and shape of
the breast or the location and extent of the tumor or tumor bed
within the breast, as identified from image guidance. The dose is
preferably referenced to dose reference points within the breast
identified from appropriate image guidance. The position,
intensity, size, shape, energy of the source or sources are
preferably chosen such that the radiation treatment volume
coincides with the size and shape of the breast or the size, shape
and location of the tumor, tumor bed or other designated volume
within the breast based on image guidance. The dwell position,
dwell pattern, and dwell time, of the HDR source is chosen such
that the radiation treatment volume coincides with the size and
shape of the breast or the size, shape and location of the tumor or
tumor bed as identified by image guidance. For purposes of
treatment, imagable markers within the applicators are used for
alignment of the position of the applicator to the breast
coordinates to coincide the radiation treatment volume to tumor or
tumor bed volume. The treatment planning software preferably allows
the dose to the treatment volume to be monitored in real-time so as
to control the dwell position(s) and dwell time(s) of the
source(s). The radioactive sources are encapsulated in a carrier
which takes the shape of a point source, wire, tube, or foil, or
may be loaded or embedded into a carrier by means of painting,
plating, mixing into a dispersion, and chemical or physical bonding
within or on the surface of a carrier. The sources can be small
pellets or extended sources in the form of a line
(one-dimensional). The sources can be filtered (shielded) or
extended sources in the form of a flat plane (two-dimensional). The
sources can be extended sources in the form of a curved plane
(three dimensional). In one embodiment, the source(s) can traverse
along a spiral trajectory along the periphery of the breast and
extending from the chest wall to the nipple such as shown in FIGS.
3 and 4. In one alternative embodiment, the source(s) traverse
multiple, co-axial circular trajectories, all of which are largely
parallel to the chest wall and are located along the periphery of
the breast. In yet another embodiment, the source(s) traverse along
curved radial lines extending from nipple to the chest wall and are
located along the periphery of the breast. The sources may be small
pellets or extended sources in the form of a line
(one-dimensional). The sources may be filtered (shielded) or
extended sources in the form of a flat plane (two-dimensional). Or
filtered (shielded) or extended sources in the form of a curved
plane (three dimensional).
[0073] While certain embodiments have been described of an
apparatus and method that provide brachytherapy, it is to be
understood that the concepts implicit in these embodiments may be
used in other embodiments as well. The protection of this
application is limited solely to the claims that now follow.
[0074] In these claims, reference to an element in the singular is
not intended to mean "one and only one" unless specifically so
stated, but rather "one or more." All structural and functional
equivalents to the elements of the various embodiments described
throughout this disclosure that are known or later come to be known
to those of ordinary skill in the art are expressly incorporated
herein by reference, and are intended to be encompassed by the
claims. Moreover, nothing disclosed herein is intended to be
dedicated to the public, regardless of whether such disclosure is
explicitly recited in the claims. No claim element is to be
construed under the provisions of 35 U.S.C. .sctn.112, sixth
paragraph, unless the element is expressly recited using the phrase
"means for" or, in the case of a method claim, the element is
recited using the phrase "step for".
* * * * *
References