The First Stereotactic Linear-based Radiosurgery in Iran

BACKGROUND:
Stereotactic radiosurgery/radiotherapy is a modern therapeutic technique for surgically-inaccessible intracranial lesions.
For the first time in Iran, all necessary hardwares for the stereotactic linear-based radiosurgery technique have been developed .


METHODS:
Stereotactic treatment includes eight steps: making dental mold and thermoplastic mask for each patient and attaching his/her head to the head support device; mounting localizer on the head support device and then taking CT scanning slices of patient’s head with localizer; treatment planning; attaching head docking device on the linac’s couch and collimators on linac’s head; putting patient on the couch and attaching his/her head to head docking device and translating patient’s head in three axis by head docking device to put intra cranial target on the linac’s isocenter; treatment.

FINDINGS:
Quality assurance tests performed on constructed system showed a total uncertainty of 4.45 mm which is within acceptable ranges.
Using isocentric treatment method with available collimators, we can treat a 17 mm width target; though for treating greater targets, we should use multi isocentric methods.


CONCLUSION:
Stereotactic treatment gets its own importance in view of two parameter: a) precision: as intracranial targets dose not exceed of 40 mm in diameter so localization must be performed with a high precision; b) high dose: as doses in range of 10 to 40 Gy is delivered to target in one fraction, any error may yield a irreparable damage to radiosensitive critical organs in brain. Possibility of designing and constructing any modern radiotherapy modality in our country was a direct deduction of this project.

KEY WORDS:
Stereotactic radiosurgery, linear accelerator, Iran, inoperable lesions