Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-07-22
2002-10-15
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S001000, C600S002000, C600S410000, C600S414000, C600S425000, C600S426000, C600S427000, C382S128000
Reexamination Certificate
active
06466813
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the art of radiation therapy planning and, more particularly, to a method and apparatus for performing soft tissue tumor localization, virtual simulation, and dosimetric planning using volumetric frameless 3-dimensional magnetic resonance (MR) imaging data exclusively.
MR imaging data is used as the primary data set. Data acquired by other modalities such as CT, nuclear medicine, ultrasound, and others can be used as a secondary data set in conjunction with the primary MR imaging data. In that case, the secondary data is used for visualization assistance and the primary MR data is used for localization, virtual simulation and dosimetric planning.
In the past, computed tomography (CT) imaging has been used in connection with radiation therapy planning. The CT imaging data is the only data set used. In prior CT simulation systems, however, soft tissue tumors cannot be clearly identified in the acquired image. Accordingly, for those cancers, oncologists and radiation therapy planning (RTP) specialists must guess at the target location and size of the tumor based on experience. Bony structures provide only reference landmarks within the image. Therefore, the usual practice during planning is to “overstate” the area within the patient for subsequent dosimetric treatment. In that way, the radiation beam is sure to hit the intended target. However, one disadvantage to the above is that otherwise healthy tissue is also thereby unnecessarily irradiated.
An improvement over the CT simulation systems is provided by the so-called “CT with registered MR” process or simply “registration process.” That process uses the CT imaging data as the primary data set for localization, virtual simulation, and dosimetric planning. The MR imaging data set is used as a secondary data set for visualization assistance.
A simplified form of registration process currently performed in connection with radiation therapy planning is shown in
FIGS. 1 and 2
. With reference now to those figures, the CT/MR registration process
10
usually begins with a pair of patient imaging steps. A CT imaging step
12
is performed on the patient using a suitable CT imaging apparatus. An MR imaging step
14
is also performed on the patient using a suitable MR imaging device, typically located in the hospital radiology department. One disadvantage to the CT with registered MR process is that oftentimes, the CT imaging apparatus is spaced a considerable distance from the MR imaging system. The need to move the patient from one site to another takes time and causes equipment and staff scheduling difficulties. The CT imaging device capital and usage costs add additional expense to patient treatment planning.
At step
16
, the CT data set is registered with the acquired MR data set so that substantially identical CT and MR slice views of the patient can be displayed as a composite overlaid image or on respective CT and MR display devices
32
and
34
such as shown in FIG.
2
. Preferably, to aid in visualization, the CT and MR displays
32
,
34
are presented in a side-by-side relationship such as on an integrated display unit
30
. The prior art registration process
10
includes means for simultaneously displaying the registered CT and MR images on adjacent screens or on a single screen in an image overlay at step
18
.
Next in the current registration process, the soft tissue tumor is localized in the CT image by use of the MR image at step
20
. The tissue localization step uses the CT data set as the primary data set and the MR data as the secondary data set. Localization in the 2-D CT images is greatly enhanced when the 2-D MR slice is displayed together with the 2-D CT slice on a single display monitor in an overlaid fashion. In prior art systems that use a side-by-side image display methodology such as shown in the drawing figure, the operator relies on soft tissue visualization in the MR image for localization in the primary (CT) data set. Typically, as shown in
FIG. 2
, this localization step includes a selection/definition and visual display of a target boundary
36
that can be adjusted in size, shape, and position manually by an operator using suitable operator interface controls such as a mouse, or the like. As further shown in
FIG. 2
, the target boundary
36
is traced over the outer edges of a soft tissue tumor
38
shown clearly in the MR display
34
. As part of the registration step
16
and the simultaneous display step
18
, a CT target boundary
36
′ is established in the CT display
32
. The manual/operator movement of the MR target boundary
36
as well as changes in size and shape of the MR target boundary are “shadowed” by the CT target boundary display
36
′. In that way, localization of the anatomical soft tissue tumor
38
in the MR display
34
causes a corresponding localization or “segmentation” of the CT target boundary
36
′ in the CT display
32
even though the soft tissue tumor
38
is not visible in the CT display
32
. The MR image data set is discarded at step
22
.
Next, in step
24
, virtual simulation of the target boundary
36
′ is performed in the CT display
32
. The treatment boundaries and beam modifiers are derived during virtual simulation using the tumor boundaries
36
′ in the CT display
32
.
Dosimetric planning is executed in step
26
using the CT data set with the visualization and localization parameters derived from the CT image data.
One major disadvantage with the prior art CT with registered MR process for radiation therapy planning is the wasted time and expense attributable to the need for obtaining CT image data. As noted above, essentially, the MR image data is discarded early in the process.
To further exacerbate the problem, as shown in
FIG. 2
, soft tissue tumors cannot be clearly identified in the acquired CT image. Although an improvement over prior systems where CT image data forms the only data set, the CT with registered MR process continues to use the CT acquired image and display as the cornerstone of radiation therapy planning. The CT data set is used as the primary data set. As shown in
FIG. 2
, however, the essential data for localization and virtual simulation of soft tissue tumors is contained in the MR acquired image and display.
Lastly, as noted above, movement of the patient between the CT imaging device and the MR imaging device often causes problems in the registration step
16
.
There is a need, therefore, for a method and apparatus for enabling soft tumor tissue localization, virtual simulation, and subsequent dosimetric planning using the MR acquired image exclusively. An improvement over the CT with registered MR process would be to skip the steps of acquiring the CT image data altogether and to use the MR image data exclusively to generate volume images, including divergent volume images for localization, virtual simulation, and dosimetric RTP.
The present invention contemplates a new and improved method and apparatus which overcomes the above-referenced problems and others.
A primary object of the invention is to enable soft tissue tumor localization, virtual simulation, and dosimetric planning using magnetic resonance image data exclusively.
It is a further object of the invention to use magnetic resonance image data as the primary data set for soft tissue tumor localization, virtual simulation, and dosimetric planning.
It is another object of the invention to generate volume images from the acquired MR image data for soft tissue tumor localization, virtual simulation, and dosimetric planning.
A further object of the invention is to generate at least one divergent image of a volume of a patient from the acquired MR image data for soft tissue tumor localization, virtual simulation, and dosimetric planning.
Yet another object of the invention is to generate at least one of a digitally reconstructed “radiographic” image and a digitally composited “radiographic” image of a volume of a patient from the acquired MR image data for soft tissue tumor
Gadepalli Krishna K.
Shukla Himanshu P.
Fay Sharpe Fagan Minnich & McKee LLP
Lateef Marvin M.
Lin Jeoyuh
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