INTRACRANIAL STEREOTACTIC RADIOSURGERY

NASIF A PB.Sc MRT InternMALABAR CANCER CENTREINTRACRANIAL STEREOTACTIC RADIOSURGERY

IntroductionSRS refers to the precise and focused delivery of a single high dose of radiation in a single session and has been used to treat various intracranial lesions and skull base lesions.SRS combines stereotactic localization with multiple cross fired beams from a highly collimated high energy radiation source.This method of non invasive ablation has proven to be an effective alternative to the conventional neurosurgery.

HistoryGamma knife was invented By professor Lars Leksell in stockholm,sweden.

Different modalities

LINACGAMMA KNIFECYBER KNIFE

TYPESFrame based Frameless

Intracranial SRSIndications*Arteriovenous malformations*Meningiomas*Pituitary adenomas*Acoustic neuroma*Pineal tumor*Acoustic tumours*Craniopharyngioma*Brain metastasesContraindications*Tumours 4cm or larger in diameter.

*Tumours adjacent to eloquent structures such as brain stem&optic chiasma.

*Pediatric cranial lesions.

Step IAttaching the frame

A lightweight frame is placed on the head.Local anesthesia of the pin sites is performed for head frame placement.

Step IIImaging

A co-ordinate box is used during imaging,for precisely define location,size and shape of the target area.Imaging may be MRI,CT or Angiography.

Step IIITreatment planning

The positioning of the head frame relative to the Gamma Knife for each shot is documented by the x-, y- and z-coordinates and the Gamma angle and is determined by treatment planning parameters required to satisfy the therapeutic goals, namely, target coverage and sparing of critical structures.

Step IVTreatment

The head frame is attached to the collimator of the Gamma knife system.The patient is positioned according to the approved treatment plan.The patient must be kept awake during the treatment.

AdvantagesReduce the hazards of open surgery.Destroy any deep brain structure without risk of bleeding and infection.Precise localisation of the target.Ensures high mechanical accuracy by means of collimator helmet.Anaesthesia is not required unless the patient is restless.Shorter recovery periods.Late toxicities are low.High rate of local tumour.

ReferencesLars Leksell,Stereotactic radiosurgery,Journal of Neurology,Neurosurgery and Psychiatry.William R Hendee,Stereotactic radiosurgery and stereotactic body radiation therapy.L Dade Lunsford,Jason Sheehan,Intracranial stereotactic radiosurgery.