3D Conformal Therapy
Mention the phrase, "3D," and many of us are transported back to childhood, when we sat with expectation in a dimmed movie house, wearing funky paper glasses that made everything jump from the screen. At the time, we thought this was the height of special effects.

In its infancy, the use of 3D changed the way we looked at the world. Today, with the use of computer-generated 3D images, it is changing the way we treat cancer.

The advent of 3D conformal therapy has expanded the precision in which radiation may be administered. By using advanced computer graphics, CT scans and algorithms to precisely generate a visual, three-dimensional image of an organ, the radiation oncologist is able to determine the best means of delivering radiation within the confines of a tumor. This minimizes the damage to surrounding healthy tissue, maximizes the dosage given, and reduces the degree of side effects.

The process begins with a volumetric CT scan of the tumor area. Before scanning, an immobilization device of foam or plastic may be molded to the patient. This will be used for precise positioning of the patient during treatment. Then, the targeted treatment area is filmed in slices of 2-5mm intervals.

When computerized, these "slices" will be compiled to display the contours of the tumor three-dimensionally on the monitor. With this 3D image, which allows the radiation oncologist to "see" the tumor from all angles, the best radiation beam arrangements are determined. The goal is to maximize treatment to the tumor, while minimizing exposure to normal tissue.

Once the beam arrangement is selected, the dosimetrist uses a specialized computer program to shape the field of treatment, in order to conform the distribution of radiation dose to the volume of the tumor. Usually the dose is conformed slightly beyond the tumor itself to allow for patient movement from breathing, as well as slight variations in the daily positioning of the patient, variances in the position of organs, (i.e. the prostate's position can vary slightly due to how full the bladder or bowel is), and the microscopic spread of the cancer.

Treatment is given five days per week, over the course of 6-8 weeks. The overall plan of treatment is broken down in fractions. These fractionated treatments permit healthy tissue to heal in between treatments. Unhealthy cancerous cells are less efficient at repairing between treatments, and will succumb to the cumulative course of radiation.