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AIM: The aim of this study is to commission and validate Dolphin-Compass dosimetry as a patient-specific Quality Assurance (QA) device. BACKGROUND: The advancement of radiation therapy in terms of highly conformal delivery techniques demands a novel method of patient-specific QA. Dolphin-Compass system is a dosimetry solution capable of doing different QA in radiation therapy. MATERIALS AND METHODS: Dolphin, air-vented ionization detector array mounted on Versa-HD Linear Accelerator (LINAC) was used for measurements. The Compass is a dose computation algorithm which requires modelling of LINAC head similar to other Treatment Planning Systems (TPS). The dosimetry system was commissioned after measuring the required beam data. The validation was performed by comparison of treatment plans generated in Monaco TPS against the measurement data. Different types of simple, complex, static and dynamic radiation fields and highly conformal treatment plans of patients were used in this study. RESULTS: For all field sizes, point doses obtained from Dolphin-Compass dosimetry were in good agreement with the corresponding TPS calculated values in most of the regions, except the penumbra, outside field and at build-up depth. The results of gamma passing rates of measurements by using different Multi-leaf Collimator patterns and Intensity Modulated Radiation Therapy fluence were also found to be in good correlation with the corresponding TPS values. CONCLUSIONS: The commissioning and validation of dosimetry was performed with the help of various fields, MLC patterns and complex treatment plans. The present study also evaluated the efficiency of the 3D dosimetry system for the QA of complex treatment plans.
RESUMEN
BACKGROUND AND AIM: Cardiac toxicity is a major concern for left breast tangential field irradiation. The left ventricle and left anterior descending (LAD) artery are suggested to be radiosensitive and radiation to these structures leads to late lethal cardiotoxicity. Moderate deep inspiration breath hold (mDIBH) during radiation treatment delivery helps in reducing the cardiac dose. This study compares dosimetric parameters of heart with and without active breath coordinator (ABC) mDIBH during tangential field breast cancer radiation. STUDY TYPE: This is a dosimetric comparative study. MATERIALS AND METHODS: Forty-five consecutive patients with left-sided breast cancer who underwent breast-conserving surgery and adjuvant tangential field and radiotherapy with ABC mDIBH between November 2013 and September 2015 in our center were analyzed in this study. The ABC device was used for respiratory control and patients who could hold their breath for 20-30 s were considered for radiation with ABC mDIBH. Simulation scans of both free breathing (FB) and ABC mDIBH were done. Tangent field treatment plans with a dose prescription of 40 Gy/15 Fr were generated for each patient, in both scans. Target coverage, dose to the heart, LAD, and the left lung were documented with dose-volume histograms. RESULTS: Statistical Package for the Social Sciences, version 20 software, was used for analysis and the level of significance was set at P < 0.05. Mean heart dose was 308.5cGy with FB and 159cGy with ABC (P < 0.0001). Mean dose to the LAD was reduced by 53.81% (1320.64 cGy vs. 606.56 cGy, P < 0.001). Target coverage was equal in both the plans. CONCLUSION: We report that the use of ABC mDIBH technique resulted in a significant reduction in cardiac dose and hence can be considered as a promising tool for cardiac sparing.
