Isocenter Verification Using Linac-Gram Films Taken with Angiolocalizer : Improved Quality Assurance of Fractionated Stereotactic Radiation Therapy(FSRT)

With the advances in radiation therapy technology and equipment, the need for more accurate and safer radiation delivery to the target region has been continuously growing. Stereotactic Radiosurgery(SRS) is a good example of 'accuracy' but has a substantial risk of causing severe late neurological damages. Fractionated Stereotactic Radiation Therapy(FSRT) is a modification of SRS enabling conventional fractionation with maintaining accuracy using noninvasive and relocatable frame. Verification of mechanical accuracy in FSRT has been done according to the manufacture's recommendations using RLPP, LTLF, and Depth-helmet. In order to reinforce this, we have developed additional novel verification procedure using Linac-grams with the Angiolocalizer attached on the GTC frame, which are then digitized into the planning software(X-Knife) to generate the three dimensional coordinates for comparison. This method has been successful in such ways that the anatomical landmarks are identifiable on the Linac-gram films and that the serial comparisons of the stereotactic coordinates of the isocenter are possible with more certainty a along the FSRT course than before.