Radiosurgery - Medical Uses

Medical Uses

Radiosurgery has been especially helpful for the localized, highly precise treatment of brain tumors. Due to the steep fall off of the irradiation fields (isodoses) from the center of the target to be ablated, normal structures such as the brain, and other vascular and neural structures around it, are relatively spared. This is achieved through the high mechanical precision of the radiation source, and the assured reproducibility of the target. The precision in the positioning of the patient, in the calculation of dosages, and in the safety of the patient, are all extremely high.

Radiosurgery is indicated primarily for the therapy of tumors, vascular lesions and functional disorders. Significant clinical judgment must be used with this technique and considerations must include lesion type, pathology if available, size, location and age and general health of the patient. General contraindications to radiosurgery include excessively large size of the target lesion or lesions too numerous for practical treatment.

The non-interference with the quality of life of the patient in the post-operatory period competes with the inconvenience of the latency of months until the result of the radiosurgery is accomplished.

Outcome may not be evident for months after the treatment. Since radiosurgery does not remove the tumor, but results in a biological inactivation of the tumor, lack of growth of the lesion is normally considered to be treatment success. General indications for radiosurgery include many kinds of brain tumors, such as acoustic neuromas, germinomas, meningiomas, metastases, trigeminal neuralgia, arteriovenous malformations and skull base tumors, among others. Expansion of stereotactic radiotherapy to extracranial lesions is increasing, and includes metastases, liver cancer, lung cancer, pancreatic cancer, etc. It has been demonstrated by the thousands of successfully treated cases, that radiosurgery can be a very safe and efficient method for the management of many difficult brain lesions, while it avoids the loss in quality of life associated to other more invasive methods.

The selection of the proper kind of radiation and device depends on many factors including lesion type, size and location in relation to critical structures. Data suggests that similar clinical outcomes are possible with all of these methods. More important than the device used are issues regarding indications for treatment, total dose delivered, fractionation schedule and conformity of the treatment plan.

In order to perform optimal radiosurgery, the radiation oncologist chooses the best type of radiation to be used and how it will be delivered. In order to plan the radiation incidence and dosage, the physicists calculate a map portraying the lines of equal absorbed dose of radiation upon the patient's head (this is called an isodose map). Information about the tumor's location is obtained from a series of computerized tomograms, which are then fed to special planning computer software.