Prostascint Fusion Imaging
The image shows a colored Prostascint overlaid on a black and white MRI image utilizing sophisticated image fusion software to precisely match the two images. The image clearly shows that the cancer has pushed through the covering of the gland on one side. This means that the treatment plan will have to expand the radiation margin on the side of the extracapsular extension. This intraoperative planning modification would not be possible with the old preplan technique.
Prostascint is an antibody to prostate specific membrane antigen (PSMA). The antibody is attached to an Indium-111 atom that can be detected by a gamma camera (similar to a PET scan). The antibody binds to PSMA anywhere in the body and the Indium-111 disintegration products are then detected by the camera.
Dr. Doggett is one of the first physicians in the world to use Prostascint image fusion to improve prostate brachytherapy planning accuracy. Preoperative Prostascint evaluation is indicated in some patients to rule in or rule out the presence of metastatic deposits outside the prostate and in the pelvic and/or para-aortic lymph nodes. If this test is, in fact, positive, then further therapies would be added to the seed implant therapy, such as hormone therapy and/or external beam radiotherapy. Elimination of external beam radiation therapy in this setting may reduce the chance of rectal complications.
An equally important reason for Prostascint evaluation is preparation for image guided brachytherapy. Fusing the Prostascint image onto preoperative MR/CT images utilizing specific image fusion software will create an anatomic map of the prostate with the malignant deposits delineated. This map can be transposed into the real time ultrasound image in the operating room with the resultant ability to increase radiation seed dose to the areas of antibody uptake and a decrease of dose to the areas free of antibody uptake. The use of intraoperative treatment planning as Dr. Doggett is currently doing facilitates the planning in the operating room, increasing dose to malignant structures and decreasing dose to nonmalignant structures, such as the rectum, urethra, bladder and neurovascular bundles.