Radiation therapy serves as a cornerstone of cancer treatment for roughly half of the patients who are challenged by this disease. The delicate balance between delivering enough radiation to destroy cancer cells while minimizing the negative impact on surrounding normal tissues is the distinctive role managed through radiotherapy simulation and planning.

Accurate imaging is the vital first step to planning in all forms of radiotherapy, but never more important than in the delivery of intensity modulated radiation therapy (IMRT). Conforming the dose to closely follow the contours of the target is essential to sparing the critical structures nearby.

Medical imaging is critical to accurate radiotherapy planning
Terri Wimms, director of oncology/CT marketing for Philips Medical Systems North America (Bothell, Wash.) emphasizes the importance of imaging the target in three dimensions. Their large bore CT scanner, is specifically designed for radiation oncology planning activities.

Featuring an aperture of 85 centimeters, rather than the traditional CT standard of 70 cm, is particularly advantageous for specific populations of patients with cancer. Philips introduced the ACQSIM CT scanner with the larger bore in October 2000, and have sold more than 100 of these units to date.

“The difference is that the larger opening allows for the unique positioning needs that radiation therapy simulation demands,” explains Wimms. “For patients with breast cancer, you have to modify the patient’s position to get them into a traditional scanner, and when you do that, you’re not truly simulating them in the position they will be treated.” The same is true for patients with lymphoma where the standard treatment position requires both arms out to the side flexed at the elbow, like placing hands on the hips.

In many instances, obese patients were ineligible for CT planning prior to development of this device. And pediatric patients who require anesthesia for planning are more easily scanned through the larger passage because although the patient is smaller, the anesthesia apparatus requires additional space.

Please refer to the October 2002 issue for the complete story. For information on article reprints, contact Martin St. Denis