Setup Uncertainties of Head and Neck Cancer Patients Treated by Intensity Modulated Radiotherapy (IMRT) in Surin Hospital
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Abstract
Background: Setup uncertainties can impact the precision of intensity-modulated radiotherapy (IMRT).
Objective: This study aimed to analyze setup uncertainties in head and neck cancer patients undergoing IMRT and utilized the data to establish appropriate planning target volume (PTV) margins.
Methods: Setup uncertainties were assessed using KV-images and cone-beam CT (CBCT) scans of head and neck cancer patients treated with the Elekta Harmony Pro LINAC from July 1st, 2022, to June 30th, 2023. Displacements in vertical, longitudinal, and lateral directions were recorded. Systematic errors, random errors, and PTV margins were calculated and subjected to statistical analysis.
Results: A total of 2,410 images (666 CBCT images, 1,744 KV-images) from 74 patients were analyzed. Systematic errors in lateral, longitudinal, and vertical directions were 0.071 cm, 0.061 cm, and 0.059 cm, respectively. Random errors were 0.11 cm, 0.10 cm, and 0.10 cm in the same directions. Calculated PTV margins using the van Herk formula in lateral, longitudinal, and vertical directions were 0.26 cm, 0.22 cm, and 0.21 cm, respectively.
Conclusions: PTV margins were found to be less than 0.5 cm, ensuring adequate coverage for all patients. However, a 0.3 cm margin may be advisable to minimize radiotherapy-related side effects.
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