External Stereotactic Irradiation by Linear Accelerator

Abstract

Stereotactic radiotherapy has two advantages: (a) the possibility of giving high radiation doses to small but spatially well-defined target volumes and (b) the presence of a stepped dose gradient between the target volume and the surrounding healthy tissues. To utilize these advantages, the authors built a new stereotactic head frame by which the intracranial target is fixed to the rotational isocenter of a 4-MV linear accelerator. The collimator openings are selected according to the volume and the three-dimensional configuration of the target, and the radiation dose is based on the radiosensitivity of the lesion. After the patient is fixed to the frame, the radiation source and the patient are rotated so that the target is irradiated through infinite portals distributed over the convexity of the skull. It is thereby possible to obtain very high radiation doses centered into the target with a stepped dose gradient. The preliminary radiodosimetric tests and the operative technique are described. The advantages of this technique compared to interstitial radiotherapy and Leksell's radiosurgery are emphasized. This noninvasive procedure has been used to treat a series of intracranial tumors.

Plastic scintillation dosimetry and its application to radiotherapy

“…Stereotactic radiosurgery techniques are performed on intracranial lesions using a combination of multiple isocentric arc irradiations with small fields centered on the tumor target volume (Colombo et al, 1985). High-radiation doses are delivered in a single treatment, necessitating a narrow dose distribution that spares the surrounding normal tissue.…”

Quantifying isocenter measurements to establish clinically meaningful thresholds

“…This results in an ablative dose of radiation at the target with a steep dose gradient to minimize damage to tissues outside of the target 9 , 10 , 11 , 12 . SRS treatments are generally associated with small intracranial targets, and recently the term stereotactic body radiosurgery (SBRT) was developed to describe stereotactic‐guided radiotherapy to extracranial sites 13 , 14 , 15 , 16 , 17 …”

Dynamic stereotactic radiosurgery in the palliative treatment of cerebral metastatic tumors

“…Recently it has been shown that isocentric linacs can be modified to achieve standards required for radiosurgery under stereotactic conditions [5,[10][11][12][13][14], thus providing a new therapeutic approach to treat metastatic brain tumors. The initial experience in 12 patients with deep seated radio-resistant lesions was published by Sturm et al [15] using the multiple converging arc radiosurgical technique.…”