8th Baltic Congress of Radiology

Urogenital Radiology

oral abstract

In this study, prostate cancer patients were treated with radiotherapy. The influence of patient positioning error on the PTV margin size and dose in radiotherapy was discussed.

Several scientific studies were compared. In first study- thirty prostate cancer patients were treated with radiotherapy; on second study- only five prostate cancer patients were treated with radiotherapy. In both scientific studies, prostate cancer patients were placed in the supine position and had a kilovoltage cone beam computed tomography (KVCBCT) scans before treatment. The positioning errors were obtained in three linear directions which were X ( left to right), Y (superior to inferior) and Z (anterior to posterior) axes. After KVCBCT scanning, scans were compered between the planning CT images.

Before correcting errors in X, Y, Z axes on first study, it was observed that after the KVCBCT scan, higher positioning errors were obtained, than those after the manual correction. Study shows that before correction, PTV margins in the X, Y , Z directions were 0.61, 0.78, 0,41 cm after correction, these were 0.17, 0.12 and 0.17 cm. (Gang Wang, Wen-Ling Wang, Yi-Qun Liu, Hong-Min Dong, and Yin-Xiang Hu, 2018) A second study shows that the inaccuracies of 0.6 and 0.8 cm had the greatest influence on dose deviations for all the patients. The dose for PTV decreased with all the inaccuracies. (Donata Griciūtė, 2019)

Summarizing all the information from studies, it shows that after correction, the PTV margins decreased by 72%, 85%, and 56% in three linear directions of X, Y, Z . Comparing the data, 0.4 and -0.4 cm inaccuracies have the most influence on the deviation of the dose. Therefore, patient positioning error has an influence on the PTV margin size and dose in radiotherapy.

The influence of patient positioning error on the PTV margin size and dose in radiotherapy was discussed. Several scientific studies were compared and it shows that patient positioning error has an influence on the PTV margin size and dose in radiotherapy.

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