IMRT: The New Gold Standard in Radiation Therapy
The IMRT system is a state-of-the-art medical device that enables physicians to treat life-threatening conditions such as brain tumors and arterial venous malformations without making a single surgical incision. Multiple brain tumors can be treated in a single pass. In addition, it is able to treat malignancies stereotactically in other parts of the body including the prostate, liver, pancreas, and certain colon lesions. Some tumors of the head and neck can be treated while sparing the parotid glands. Now, lesions near the spinal cord can be treated safely as well. The hallmark of IMRT is its accurate dosage delivery for both single and multiple faction treatments using an average of 10,000 individual converging beams of photons (x-rays) per session. Its pinpoint precision ensures that the therapeutic dose of radiation conforms to the shape of the lesion while sparing the surrounding healthy tissues.
What Is Intensity-Modulated Radiation Therapy?
State-of-the-art radiation therapy that varies the dose of radiation within the tissue such that one or multiple targets receiving the same or different doses can be treated accurately. The PEACOCK is an integrated system involving the patient, treatment software, and electromechanical devices a MIMiC (multivane intensity modulation compensator) which delivers a non-uniform radiation beam on a slice-by slice basis to create a uniform dose distribution at the target site; at the same time a much lower dose goes to the adjacent tissues. The MIMiC is attached to the linear accelerator head; it modifies the fluence of the radiation beam as the head of the linear accelerator rotates around the patient. For every 5° rotation, the 40 individually controlled beams, covering an area of 2.0 centimeter by 20.0 centimeters, are constantly updated according to the computer prescription. Each update selects among 1020 possibilities. The 40 beams can be individually controlled during the 270° rotation. Compressed air drives the vanes according to the treatment plan as the accelerator is rotating around the patient. Position sensors that monitor the accelerator position and vane movement keep track of the dose, the intensity, and the number of treatment, so that only what has been prescribed can be delivered.
Unlike other systems in which the clinician and physicist make the best educated guess on how to treat the patient, we now have the technology to deliver an optimum treatment plan. The computer selects among 5,000 different possible scenarios in order to best fulfill the therapy prescription.
A Team Approach
This therapy is provided by a well-trained team of clinicians from Neurosurgery, Radiation Oncology and Medical Physics. The physician and physicist at Beverly Oncology previously introduced the first frameless stereotactic radiosurgery system in California in 1993 (p-Reference System). After performing over 12,000 procedures, the team continues to maintain a leadership role in this field by having installed the first PEACOCK system in Los Angeles County; the fourth in the state. We since have upgraded our software to CORVUS 4.
Special Advantages of the CORVUS 4 System
Intensity-Modulated Radiation Therapy brings radiation therapy to new heights. Up to three brain lesions can be treated in one pass. With the gamma knife or photon knife systems, only one lesion can be treated at a time. In addition, certain head and neck tumors can be treated in such a way that the salivary glands are spared. This can prevent xerostomia, which is a bothersome side effect of radiation therapy. In addition, prostate tumors can be treated non-invasively in very high doses, with only a 3% incidence of rectal complications, far superior to standard forms of radiation therapy.
What is a Typical Patient Procedure?
Patients who are eligible for Intensity-Modulation Radiation Therapy are fitted with a non-invasive stereotactic frame that is attached to their head. The frame locates specific points in the brain. A series of CAT scans are taken to assist in outlining the normal structures as well as the tumor. This information is then placed in the computer, which reconfigures the data in three dimensions. The physician and the physicist then inform the computer as to the desired doses to the target as well as the adjacent tissues. The CORVUS 4 computers (five Pentiums in series) then calculate the best radiation delivery program for the desired result. The computer calculates 5,000 repeat iterations of 1020 possibilities for each 5° of rotation. This finds the best fit for the problem. Once a solution is arrived at, the program is then produced for the review of the physician and the physicist. The patient is called in for treatment, which varies from one to 40 treatments. The actual treatment session typically takes less than 30 minutes. The invisible radiation is not felt at all. When the therapy is completed the frame is removed, and the patient is free to return to their home. The entire procedure is done on an outpatient basis.