Computerized Intraoperative Treatment Planning
This website details the advantages of permanent seed brachytherapy enhanced by advanced computerized technologies pioneered by Dr. Stephen Doggett and colleagues.
The procedure employs three key technologies:
- Intraoperative treatment planning
- Prostascint/MRI image fusion
- Nerve sparing brachytherapy
Combined, these cutting edge technologies are designed to:
- Increase the accuracy of seed position
- Increase the directed dose to malignant structures
- Decrease the dose to non-malignant structures like the rectum, urethra, bladder, and neurovascular bundles for sexual function
Dr. Stephen Doggett is a radiation oncologist with expertise in brachytherapy, computerized treatment planning and interpretation of fusion images.
What is Treatment Planning?
Treatment planning is the determination of where each of the 100 or so seeds used should be implanted in the prostate for maximum cure rates, minimum complication rates, and conformal dose distribution. Most treatment planning is done one or two weeks before the implant with an older and inaccurate technique called "pre-planning". Modern high speed computers now allow the plan to be created in the operating room in one or two minutes at the time of the implant with a technique called "computerized intraoperative treatment planning".
Why Computerized Intraoperative Treatment Planning Is Better
The old pre-plan method involves the collection of the ultrasound pictures one week prior to implant. These images are used to create a treatment plan by a physicist. This plan is brought to the operating room and used to treat the patient. Unfortunately, the ultrasound probe position and patient position cannot be exactly duplicated due to normal, daily anatomical shifts. Additionally, the prostate volume can increase up to 40% under anesthesia which makes the old pre-plan method inaccurate. The inaccuracies found in the pre-plan method can lead to hot and/or cold spots in the gland and incorrect prostate volume estimates which can result in radiation damage complications or recurrence of the cancer.
Additionally the old pre-plan method does not permit the use of advanced techniques such as Prostascint /MRI image fusion, dynamic dosimetry or nerve sparing brachytherapy since the pre-plan cannot be altered or modified. In distinction, intraoperative treatment planning allows complete customization of the plan at the time of anesthesia so the prostate and patient position do not change in the few minutes that elapses between the plan creation and the start of the implant.
Dr. Doggett's research has shown that intraoperative treatment planning decreases the rectal dose by 33% and decreases the urethral dose by 12% compared to the old pre-plan method. Equally important, the radiation coverage of the prostate is increased 11% by the use of intraoperative treatment planning. (CLICK HERE FOR DR DOGGETT'S INTERNATIONAL PRESENTATION). The American Brachytherapy Society has published a report co-authored by Dr. Doggett that concluded "Intraoperative treatment planning addresses many of the limitations of current permanent prostate brachytherapy and has some advantages over the pre-planned technique". (CLICK HERE FOR DR DOGGETT'S CO-AUTHORED PAPER)
Comparison of Pre-plan and Intraoperative Dosimetry Accuracy
The following slide illustrates how inaccurate the old pre-plan method can be. The image on the left shows what it looks like when the radiation cloud from the pre-plan is superimposed on the actual anatomy of the prostate in the operating room. There is a significant mismatch which would result in parts of the prostate not receiving enough radiation and some parts of the prostate getting too much radiation (hot spots and cold spots). This image illustrates the inherent inaccuracy of the old pre-plan method.
The image on the right shows what it looks like when the radiation cloud from the intraoperative plan is superimposed on the actual anatomy of the prostate in the operating room. The radiation cloud fits perfectly over the prostate anatomy. This means that the chance of getting a cold or hot spot is minimized and accuracy of dose distribution is maximized.
History of Image Registered Intraoperative Treatment Planning
Clinical development for emerging image registered intraoperative treatment planning technology began Spring 1998. Dr. Doggett was asked to act as a clinical developer for this advanced technology. The technology is a combined effort of CMS/ Burdette Medical Systems and the Joint Center for Radiation Therapy, Harvard Medical School. Dr. Doggett was the first physician outside of Harvard Medical School to use the CMS/Burdette Interplant intraoperative treatment planning system and has incorporated it into is treatment planning since 1999.
Why Is Image Registration Important in Intraoperative Treatment Planning?
Image registration is an essential technology for intraoperative treatment planning. The position of the ultrasound images are "registered" or measured by the computer in 3D during the implant procedure. The computer is then able to position the radiation plan onto the prostate anatomy to ensure an exact match and thus minimize cold and hot spots.
Optical spatial sensors in the ultrasound probe holder localize the template/probe in real time enabling precise three dimensional image registration to template/probe position. Image registration is the essential platform technology for intraoperative treatment planning, nerve sparing brachytherapy, image fusion and robotics.
How Is the Intraoperative Plan Created?
Cross section prostate ultrasound images are collected every 5 millimeters in the operating room. These images are imported into the planning system.
A light pen is used to outline the contour of the prostate, urethra and rectum on each cross sectional prostate ultrasound image.
The computer creates a 3D model of the prostate, urethra and rectum that can be viewed at any angle for increased precision.
The computer specifies where in 3D each needle and each seed within those needles should be placed. The chance for human error is therefore greatly diminished.
The computer has performed 3 million calculations in a few seconds, producing a precise plan determining where each needle and seed should be implanted. Minor adjustments can be made in a few seconds to fine tune the plan prior to needle placement if needed.
What is Dynamic Dosimetry?
Dynamic dosimetry is an advanced software and hardware dependent proprietary technique that allows the determination of the seed position in 3D immediately after it has been placed in the prostate. After a seed is placed, itsí position as seen on a sideways (sagittal) ultrasound image is recorded in 3D by the computer. The computer automatically changes the isodose curves to reflect any deviation of seed position. As the implant proceeds, dynamic dosimetry allows the detection of hot spots and cold spots as they are forming, and re-calculates how the next row of seeds should be placed in order to minimize these hot and cold spots. Dynamic dosimetry enables the final implanted seed positions to be optimized and quantifies seed position deviation so corrections can be made intraoperatively. Dynamic dosimetry is not possible with the old pre-plan method.
Dynamic Dosimetry Illustrated
In the next slide, an ultrasound side view of the prostate is seen. The implanted needles are clearly visible. The implanted seeds are seen inside the magenta colored boxes. The seeds are in their appropriate computer designated places which has been confirmed and determined by the computer greatly reducing any human error.