Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-09-09
2001-03-27
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S439000
Reexamination Certificate
active
06208883
ABSTRACT:
The present invention is concerned generally with a method and apparatus for performing therapeutic treatments of prostate cancer. More particularly, the invention is concerned with a method and apparatus for accurately determining the location of the prostate for carrying out precision radiation therapy treatment of the prostate. The method and apparatus involve a pre-therapy, or planning, phase in which the prostate position is determined by a transrectal ultrasound image, relative to proximate anatomical structures defined by diagnostic X-ray images. The resulting prostate coordinates are then transformed to the coordinate system of the radiation therapy field for use during the treatment phase.
Adenocarcinoma of the prostate is the most commonly diagnosed noncutaneous cancer in the male population of the United States. It is estimated currently that 200,000 new cases of prostate cancer will be diagnosed each year. Approximately 16% of these newly diagnosed cases will be locally advanced non-metastatic cancers or, more specifically, AJCC stage III-T3N0M0. Treatment of patients in this stage is problematic. Significantly low rates of local control of the disease have been reported using conventional doses of radiation delivered with external beam radiation therapy for clinically locally advanced disease. In addition a smaller but significant proportion of patients with earlier staged disease develop recurrence after radiotherapy. Treatment of prostate cancer is difficult because of the extreme proximal position of radiation sensitive tissues, such as the bladder and rectum, and is further complicated by prostate motion relative to the radiation field on a daily basis. To improve the treatment outcome, more aggressive radiation techniques utilizing highly conformal fields and higher doses is being investigated. However, such dose escalated, conformal treatments cannot effectively be delivered without significant toxicity to normal tissues unless the exact position of the prostate can be determined and its spatial repositioning is dramatically reduced.
In general performing treatment of prostate cancer using radiation therapy involves the patient undergoing a conventional computerized tomography (“CT”) scan of the pelvis to determine the approximate size, shape and location of the prostate gland. The position of the prostate is important since it is the intended target of the radiation. The patient then undergoes a treatment simulation in which planar, diagnostic X-ray films are taken in the plane of each of the proposed radiation fields. These X-ray films define where the prostate (or target volume) and radiation sensitive structures, such as the rectum and bladder, lie with respect to the radiation output portal. The goal of therapy is to treat the prostate with the prescribed dose, while minimizing the dose to the radiation sensitive structures. However, the prostate gland does not appear on these diagnostic X-ray (simulator) films. Therefore, the position of the prostate must be inferred from the previously acquired CT images and the relative position of the bladder, rectum and bony landmarks taken with the patient positioned differently than when the simulation films are taken. Since the position of the prostate is partially inferred from the position of the bladder and rectum, it is extremely important to accurately delineate these structures on the simulator films. This is normally achieved by inserting a catheter and injecting an X-ray contrast agent. Once the approximate position of the bladder, rectum and bony structures have been determined, the approximate shape and position of the prostate is hand drawn on the simulator films, aided by the information available from the CT images. The position of the bladder and rectum is determined from images taken at the time of simulation. The shape and position of the prostate is however obtained from CT images taken at a different time and patient position, and consequently a margin of dimensional safety must be drawn around the prostate volume to account for the variation of patient setup, target motion, and the spatial approximations inherent in localizing the prostate from the CT images to the simulator images. This margin is intended to insure that the prostate gland is receiving the intended dose. In the effort to insure that the prostate is receiving the proper dose, portions of the nearby rectum and bladder will also receive high doses. The close presence of these healthy structures limit the dose to the prostate. These proximal structures will then dictate what dose the prostate will receive, instead of the biology of the cancer. As a consequence of this uncertainty in prostate location, it has been postulated that currently accepted prescription doses for the prostate are in fact not optimal doses for the control of the disease. Local recurrence rates for prostate cancer using standard radiation therapy are high, approximately 50%, for larger tumors.
In an attempt to minimize the dose to normal tissues, in another conventional methodology radiation fields which geometrically correspond to the target volume can be used. Such therapies are called conformal therapies. There have been reports on the use of conformal techniques in an attempt to escalate the dose to the prostate with external beam radiation, although these methods are not in general use. Careful dose escalation studies are underway at several institutions to determine the acute and late toxicities of increased dose, albeit reduced volume of rectum and bladder. It has been reported that in a multivariate analysis fewer grade II toxicity's were observed in patients treated with conformal therapy. Low rates of chronic rectal morbidity have also been reported with similar conformal approaches. Conformal therapy does however require exact delineation of the target volume. This can be accomplished if the prostate tumor volume is accurately visualized and if one gains precise control or knowledge of those variables which determine the margin around the tumor volume. Microscopic disease, dose limiting structures such as the anterior rectal wall and prostate motion are important variables for determining the target volume. In spite of the promise of conformal therapy, this methodology is still plagued by the problems of prostate motion and inaccurate spatial localization.
It is therefore an object of the invention to provide an improved method and apparatus for radiation therapy treatment for prostate disease.
It is another object of the invention to provide a novel method and apparatus for accurately identifying the prostate position in preparation for prostate radiation therapy.
It is a further object of the invention to provide an improved method and apparatus for establishing an ultrasound image of the prostate and correlating that image to radiation therapy simulator images.
It is also an object of the invention to provide a novel method and apparatus for real time superposition of an ultrasound image of the prostate onto another image, such as a simulator or radiation therapy image.
It is yet another object of the invention to provide an improved method and apparatus for establishing at least two landmark points characteristic of patient anatomy for accurately positioning the prostate relative to radiation therapy fields.
It is an additional object of the invention to provide a novel method and apparatus for establishing landmark points on ultrasound and X-ray images to allow precise localization of the prostate relative to a radiation therapy field.
It is still a further object of the invention to provide an improved method and apparatus for accurately positioning the prostate (or patient) for radiation therapy using a couch mount for a transrectal probe having ultrasound transducer elements.
It is yet another object of the invention to provide a novel method and apparatus employing an ultrasound probe to form a geometry specific scan field with the transducer arc end points establishing landmark end points on an image enabling a mapping transformatio
Burdette Everette C.
Holupka Edward I.
Kaplan Irving D.
Associates of the Joint Center for Radiation Therapy, Inc.
Foley & Lardner
Jaworski Francis J.
Rechtin Michael D.
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