Journal Article

Retrospective study of random and systematic errors in Head and Neck cancer Patients with Image guided Helical Intensity Modulated Radiation Therapy

Kaur, Navneet, Devi, Rama, Sharma, Ishu, Kumar, Munish, Anand, Mridul, Passi, Kamlesh, Kanda, Naveen, Basandrai, Deepak, Singh, Vikram

2022

Overview

The Precision of radiotherapy is checked based on the matching of pre-treatment 2D portal imaging/CBCT to the reference image. The objective of this study is to find inter-fractional systematic and random setup errors (mm) for head and Neck cancer patients and also find setup margin for Planning Target Volume (PTV) at Mohan Dai Oswal Cancer Hospital Ludhiana Punjab. Inter-fractional motion errors were quantified for 10 Head and neck cancer patients who underwent image guided helical intensity modulated radiation therapy with Radixact X9 machine. One hundred fan beam computed tomography scans of 2mm slice thickness, 3.5 MV average energy and flattening filter free beam has been used to collect the data for the calculation of systematic and random errors. After patient immobilization, patient accuracy is checked with registration of pre-treatment image with reference planning image with the help of Accuray Precision image guidance protocol. For every patient 10 fan beam computed tomography images has been taken. Translational errors have been calculated in X, Y and Z direction to find systematic error (∑) and random error (σ). The final PTV margin is calculated by van Herk’s equation (2.5∑ + 0.7σ). The results of this study shows that mean translational errors varies from -2.3 mm to 3.3 mm in lateral direction (X), -3.6 mm to 1.7 mm in longitudinal direction (Y), -2.7 mm to 1.5 mm in vertical direction (Z). The mean and standard deviation (SD) for systematic errors are 1.467, 0.8, 0.923 and random error 0.0595, 0.02266, 0.03824 in X, Y and Z direction has been calculated. The Total Margin for CTV to PTV which include setup margin (mm) in X, Y and Z direction are 3.7 mm, 2.02 mm and 2.33 mm. In addition to that, a PTV margin of 5.00 mm is the appropriate margin for Mohan Dai Oswal Cancer Hospital’s patients. This work conclude that CTV to PTV margin of 5.00 mm is suitable for image guided helical intensity modulated radiation therapy for Head and neck patients to ensure the minimum 95% coverage of dose to target

• Publisher: IOP Publishing
• Subject: Cancer / Cancer therapies / Computed tomography / Head & neck cancer / IMRT / Mathematical analysis / Mean / Medical imaging / Patients / Physics / Pretreatment / Radiation therapy / random error / Random errors / Systematic error / Systematic errors / Tomography