New frontiers in radiosurgery for the brain and body

Abstract

Radiosurgery is defined as the use of highly focused beams of radiation to ablate a pathologic target, thus achieving a surgical objective by noninvasive means. Recent advances have allowed a wide variety of intracranial lesions to be effectively treated with radiosurgery, and radiosurgical treatment has been accepted as a standard part of the neurosurgical armamentarium. The advent of frameless radiosurgery now permits radiosurgical treatment to all parts of the body and is being actively explored by many centers. This article reviews some of the modern tools for radiosurgical treatment and discusses the current clinical practice of radiosurgery.

Figure 1

Schematic showing the central idea of radiosurgery. The target (shown in red) receives a dose from each beam of radiation, whereas any other site receives a dose from only a single beam.

Figure 2

The Gamma Knife. The inset shows the collimator with 201 holes allowing 201 beams of radiation. During treatment, the Gamma Knife doors (arrow) open and the couch moves into the unit to position the head under the cobalt sources. Main photo courtesy of Elekta.

Figure 3

(a) Gamma Knife plans showing coverage of tumor with a 40% isodose line (shown in yellow) obtained by superimposing different spheres. (b) The Gamma Knife system includes collimators allowing creation of spheres of 4, 8, 14, and 18 mm.

Figure 4

An MR image of a 57-year-old woman with non–small cell lung cancer, described in case example 1. (a) The right frontal lobe lesion at the time of Gamma Knife treatment. (b) The same region 3 months after treatment.

Figure 5

The CyberKnife. Arrow indicates the modified linear accelerator. Photo courtesy of Accuray.

Figure 6

The patient described in case example 2. (a) A computed tomography scan of the chest at the time of CyberKnife treatment showing a large tumor (left) and pleural effusion (right). (b) The same regions 6 weeks after treatment. The tumor is significantly smaller, and pleural effusion has resolved. Arrows indicate tumor and effusion.

Figure 7

The patient described in case example 3. (a) An MR image of the head showing three lesions (arrows) due to metastatic ovarian cancer. (b) The same regions 6 years after treatment. Two of the lesions have resolved and one is smaller (arrow).

Figure 8

An MR scan of a 17-year-old male with a pilocytic astrocytoma treated with resection followed by external beam radiotherapy. (a) The tumor outlined by a 30% isodose line on the day of Gamma Knife treatment. (b) The same region 3 months later showing a significant decrease in tumor size. The dose was 13.5 Gy to the 30% isodose line.

Figure 9

The patient described in case example 4. (a) An angiogram showing a thalamic arteriovenous malformation on the day of Gamma Knife treatment. (b) An angiogram 3 years after treatment showing resolution of the malformation.

Figure 10

Schematic of the setup for CyberKnife treatment of infants. D indicates the x-ray detector of the CyberKnife system. Reprinted with permission from reference 48.

Figure 11

An MR image showing the trigeminal nerve. The inset shows targeting used in Gamma Knife radiosurgery for trigeminal neuralgia (the green line is the 20% isodose line and the yellow line is the 50% isodose line).