M-A. Bazioglou 1,2 , K. Theodorou 2 , C. Kappas 2 , J. Kalef-Ezra 1
1. Medical Physics Laboratory,
Medical School, University of Ioannina, Ioannina, Greece (Hellas)
2. Medical Physics Department,
Medical School, University of Thessalia, Larisa, Greece (Hellas)
Manuscript received: October
10, 2000; revised: May 14, 2001 and March 19, 2002
Accepted for publication: June
14, 2002
Abstract
A bullet shaped head phantom was designed for the verification of the localization and the treatment delivery of stereotactic radiotherapy procedure. The phantom allows the accommodation of TLDs, films, and test objects. It can be easily constructed and it can be used in any linac-based stereotactic unit for both routine and commissioning performance testings. Its use at the stereotactic unit of the University Hospital of Patras indicated a mean error in the localization procedure of (1.0 ± 0.5) mm and a mean spatial uncertainty in treatment delivery of (1.7 ± 0.6) mm. In addition, the deviation of the isocenter dose determined using TLDs from the calculated one was less than 1.5%, when corrected for the density difference between water and PMMA. The dose distributions obtained with radiochromic films were in good agreement with the calculated. However, thermoluminescent dosimetry indicated sharper dose distributions (1-2 mm).
KEYWORDS: Phantom, dosimetry, localization errors, stereotactic radiotherapy.