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1 2008

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Evaluation of set-up verification with the analysis of systematic and random errors in radiotherapy - a study of the Great Poland Cancer Centre

Szczurek Ł., Skrobała A., Piotrowski T., Jodda A.

Nukleonika

2008

Vol. 53, No. 4

167-171

The aim of this study was the examination of influence of location tumors and methods of immobilizing on values of geometrical errors during treatment, and the analysis of set-up errors in reference to the method of irradiation in three groups of patients before and after corrections. This study included three groups of patients with prostate cancer (59 patients, 277 portal images), head and neck (60 patients, 285 portal images) and brain tumor (45 patients, 175 portal images). Ratios of IMRT vs. 3D-CRT were respectively: in I group 76% vs. 24%, in II group 95% vs. 5% and III group 83% vs. 17%. Set-up errors were compared in reference to the technique of irradiation and stage of treatment. The displacements were significantly higher in the first group compared with head, neck and brain tumors; 5.66, 4.05, 3.93 mm, respectively. The values of the vector lengths were significantly dependent on the type of irradiation technique (3D-CRT vs. IMRT) only in the first group (p < 0.001). The average of vector length in I, II and III group were significantly reduced from; 5.67, 4.02, 3.91 mm to 5.13, 3.63, 3.57 mm after correction, respectively. The Spearman test is indicating a low negative correlation between set-up errors and the following fractions. The applied methods of patients positioning with prostate cancer produce a worse repeatability than the ones used for patients with head, neck and brain cancers. Portal verification reduces values of set-up errors. Significant differences in the magnitude of displacements before and after correction were observed. No significant differences between value of displacement and number of fraction were revealed.