Effect of source positional discrepancy on dose and dose distributions in cobalt-60 stereotactic radiosurgery units

Nihon Hoshasen Gijutsu Gakkai zasshi
Hisato Nakazawa, Yukio Uchiyama

Abstract

We assessed the impact of source positional discrepancy on dose and dose distributions in Gamma Knife (GK) Perfexion (PFX) stereotactic radiosurgery. A spherical phantom dedicated in GK machine was used and irradiated by 2 Gy in each position moved at an interval of 0.1 mm from its original position using three types of collimators (4, 8, 16 mm) to evaluate the changes of dose. In addition, to obtain the dose distributions, radiochromic film was inserted in the phantom and irradiated by 6 Gy in each position moved at an interval of 1 mm from its original position using three types of collimators. A distance-to-agreement analysis (DTA) was performed to compare isodose lines from 10% to 90% of dose distributions between the original and deviated position. As a result, when the source moved toward the discrepancy from the center of the collimator, the dose and dose distributions discrepancies increased according to the degree of discrepancy. Especially in 4-mm collimator, 0.5 mm discrepancy caused dose reduction of 5%. On the other hand, 0.5 mm discrepancy showed merely dose differences less than 0.5% in 8 mm and 16 mm collimators. Regarding dose distributions, 1 mm discrepancy in all collimators showed little changes in DTA withi...Continue Reading

References

Oct 3, 2007·Neurosurgery·Christer Lindquist, Ian Paddick
Jan 13, 2009·International Journal of Radiation Oncology, Biology, Physics·Yoshinori HiguchiNaokatsu Saeki
May 9, 2012·International Journal of Radiation Oncology, Biology, Physics·Mark RuschinDavid Jaffray
Apr 9, 2014·Journal of Applied Clinical Medical Physics·Hisato NakazawaTatsuya Kobayashi

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