Transition From Whole Brain Radiation (wbr) To Highly-focused Radiation Delivery Systems Designed To
The ability of all radiation to effectively control the growth of cancer anywhere in the body is based on the tolerance of the normal tissue within which the cancer is embedded to sustain exposure to therapeutic doses of radiotherapy without suffering significant damage. The treatment dose is therefore limited by the need to protect and preserve the surrounding healthy tissue while delivering a lethal dose to the cancer.
This is the great challenge to all radiation protocols. Numerous creative approaches have emerged over the decades since WBR was introduced in the early 1950s to circumvent this limitation. Recognizing that all normal tissue has a daily radiation dose it can tolerate with a margin of safety. Based on this, the total therapeutic prescription can be divided by his factor and then delivered in small fractions over the days it takes to reach the desired dose. This technique of fractionation has been the mainstay of radiation oncology since its introduction.
Cancerous growths could be much more effectively eradicated if this limitation was not an issue. Radiation has progressed over the years by creating innovative approaches to deliver higher doses while protecting he host tissue. With the advent of CT and MRI which now allow exquisite visualization of the target to be treated and the exact margin between normal and disease, as well as more and more sophisticated radiation delivery systems that are designed to be more exact in putting the dose in the target, treatment has become safer and more effective.
The linear accelerator, which is the workhorse of radiation oncology devices is now built with on line CT and/or MRI scans which allow real time imaging to allow the most.