A comparative evaluation of patient-specific quality assurance techniques for head and neck cancer: Portal dosimetry versus ArcCheck

The current study employs portal dosimetry and ArcCheck to investigate the consistency of patient-specific quality assurance by implementing different gamma criteria’s for evaluating dose fluence in Head and Neck cancer patients. A total of 50 Head and Neck cases were taken retrospectively which were planned with 5 to 7 fields IMRT technique. All treatment plans were generated using Eclipse planning system V.15.6 with no normalization point mode. Gamma Index (GI) & Dose difference variations of portal dosimetry and ArcCheck were compared. Portal dosimetry is done by using DMI of Halcyon V.2.0. From the dosimetry analysis, an average value of IMRT plans with gamma evaluation criteria (3%/3mm) using portal dosimetry & ArcCheck were found to be 99.50 ±0.038% & 99.88 ±0.047% with CoV of 0.038 and 0.047 respectively. Means of maximum and average absolute dose differences (cGy) for ArcCheck were found to be 0.214±0.09 & 0.023±0.00 respectively. Similarly, for portal dosimetry these values were found to be 0.323±0.19 & 0.216±0.01 respectively. Mean of gamma average for portal dosimetry was found to be 0.2154. Result obtained from our data showed that a lower gamma index values discrepancy between the measured and estimated TPS dosages, which signifies a very high level of accuracy of our IMRT delivery. Since passing criteria using gamma index method is 3%/3mm, which is globally acceptable. Our result shows a very good agreement between dose measured by DMI of HalcyonTMV.2.0 and SNC ArcCheck dosimetry system.