DOSIMETRY IN DIGITAL BREAST TOMOSYNTHESIS: COST-EFFICIENT APPROACH FOR THE SOUTH AMERICAN PERSPECTIVES.

The measurement of air kerma in air (Kair) to estimate average glandular dose (AGD) received during digital breast tomosynthesis (DBT) studies is sometimes a difficult task. In this work, a novel methodology was implemented to measure Kair and half-value layer while the X-ray tube is rotating. A low economic cost support (LCS) was built to place aluminium sheets and a calibrated dosemeter. Three Fujifilm Innovality equipment were used and two dosemeters calibrated on W-Al energies. Validation of the new methodology was made against standard scheme and it was applied to estimate AGD for 300 patients and 7 phantoms. Validation analysis was satisfactory. The difference in the AGD calculated with the LCS and DICOM Header was lower than ±10%. AGD values ranged from 0.77 to 2.11 mGy and 0.85 to 2.15 mGy for phantoms and patients, respectively. The novel methodology has a potential use for DBT equipment without stationary mode.

Testing the methodology for dosimetry audit of heterogeneity corrections and small MLC-shaped fields: Results of IAEA multi-center studies.

UNLABELLED: The International Atomic Energy Agency (IAEA) has a long tradition of supporting development of methodologies for national networks providing quality audits in radiotherapy. A series of co-ordinated research projects (CRPs) has been conducted by the IAEA since 1995 assisting national external audit groups developing national audit programs. The CRP 'Development of Quality Audits for Radiotherapy Dosimetry for Complex Treatment Techniques' was conducted in 2009-2012 as an extension of previously developed audit programs. MATERIAL AND METHODS: The CRP work described in this paper focused on developing and testing two steps of dosimetry audit: verification of heterogeneity corrections, and treatment planning system (TPS) modeling of small MLC fields, which are important for the initial stages of complex radiation treatments, such as IMRT. The project involved development of a new solid slab phantom with heterogeneities containing special measurement inserts for thermoluminescent dosimeters (TLD) and radiochromic films. The phantom and the audit methodology has been developed at the IAEA and tested in multi-center studies involving the CRP participants. RESULTS: The results of multi-center testing of methodology for two steps of dosimetry audit show that the design of audit procedures is adequate and the methodology is feasible for meeting the audit objectives. A total of 97% TLD results in heterogeneity situations obtained in the study were within 3% and all results within 5% agreement with the TPS predicted doses. In contrast, only 64% small beam profiles were within 3 mm agreement between the TPS calculated and film measured doses. Film dosimetry results have highlighted some limitations in TPS modeling of small beam profiles in the direction of MLC leave movements. DISCUSSION: Through multi-center testing, any challenges or difficulties in the proposed audit methodology were identified, and the methodology improved. Using the experience of these studies, the participants could incorporate the auditing procedures in their national programs.