Technological Advances of Permanent Seed Brachytherapy Page 6

Permanent Seed Brachytherapy

Stephen W. Doggett MD
14642 Newport Ave #470
Tustin California, USA 92780
714 573 9500 Fax 714 573 9505
www.nocancer.com

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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 and minimum complication rates.
Most treatment planning is done one or two weeks before the implant with an older and inaccurate technique called “preplanning”.
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 “intraoperative treatment planning”

The old preplan 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 then brought to the operating room and used to treat the patient. Unfortunately, the ultrasound probe position and the patient position cannot be exactly duplicated. Additionally, the prostate volume can increase up to 40% under anesthesia which makes the old pre plan method inaccurate. This inaccuracy of the old pre plan method can lead to hot spots and cold spots in the gland, which can result in radiation damage complications or recurrence of the cancer. The old preplan method does not permit the use of advanced techniques such as Prostascint /MRI image fusion, dynamic dosimetry or nerve sparing brachytherapy since the preplan cannot be altered. 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 preplanned technique.(CLICK HERE FOR DR DOGGETT'S CO-AUTHORED PAPER )

The following slide shows 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. 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. This image illustrates how accurate the intraoperative planning method is.

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 treated his first patient with it in 1999.

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.

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. This fine tuning is not possible with the old pre plan method.

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, its’ 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.(CLICK HERE FOR LINK TO CMS IMAGE FUSION SOFTWARE SITE)
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 correct these hot and cold spots.
Dynamic dosimetry enables the final implanted seed positions to closely match the planned seed positions, and quantifies seed position deviation so corrections can be made intraoperatively. Dynamic dosimetry is not possible with the old pre plan method.

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, except for the seed farthest to the right, which is a bit too far down and to the right.

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