Mean Glandular Dose Measurement in Three Mammography Centers in Kashan: An approach to Provide a Local DRL

Purpose: Mammography is the most important diagnostic modality for early detection of breast cancer, however, concerns related to the side effects induced by ionizing radiation are still present. In the current study, the Mean Glandular Dose (MGD) values for mammography examinations as well as a local Diagnostic Reference Level (DRL) were obtained for mammography centers in Kashan, Iran. Materials and Methods: Three mammography devices from three radiology centers were selected to obtain the MGD values of mammography examinations. To assess the MGD values, the technical parameters for patients’ imaging at these three radiology centers were extracted. Then, the incident air kerma (in mGy) value received by each patient was measured by a UNIDOS E electrometer (PTW, Germany) along with a SFD mammography ionization chamber (PTW, Germany). Finally, the incident air kerma values were converted to the MGD values by specific conversion factors. Based on the obtained MGD values, a local DRL was also established for mammography examinations. Results: Mean MGD values per exposure were obtained 2.39 ± 1.46 mGy for Right Craniocaudal (RCC), 2.64 ± 1.67 mGy for Left Craniocaudal (LCC), 2.82 ± 1.89 mGy for Right Mediolateral Oblique (RMLO), and 3.09 ± 1.90 mGy for left mediolateral oblique views. Moreover, a local DRL obtained from mammography examinations, which was established as the overall median of MGD value, was 1.72 mGy (1.91 mGy for digital and 1.32 mGy for analog mammography). Conclusion: The MGD values for different views obtained in this study are in the range of previously reported values. Considering the European guidelines for quality assurance in breast cancer screening and diagnosis, it can be mentioned that the obtained DRL was less than the recommended dose level (2.0 mGy).

A Simple and Novel Approach to Study Kinetics and Estimate Radiation doses from Internally Administered Radiopharmaceuticals using An External dose Measurement System

Various methods have been reported to study radiotracer kinetics and make internal dosimetry feasible in the routine clinical nuclear medicine practice. The aim of the present study was to quantify cumulative activity and organ doses using an indigenously designed and fabricated external dose measurement system. The measurement was demonstrated on patients undergoing whole-body (WB) 18F-FDG (Fluorine-18-fluorodeoxyglucose) direct positron emission tomography/computed tomography investigations. An external dose measurement system comprising of an ionisation chamber-survey meter and the movable focussing collimator was used to quantify the uptake of 18F-FDG in liver and brain. Cumulative activity and normalised cumulative activity in these organs were calculated. The results were validated by performing measurements on a phantom uniformly filled with known activity of 18F-FDG.The difference in the absorbed dose estimated with and without collimator was statistically significant (p < 0.05). The external dose measurement technique is relatively novel, convenient and reliable for the assessment of internal absorbed dose of organs.

Skin dose measurement and estimating the dosimetric effect of applicator misplacement in gynecological brachytherapy: A patient and phantom study

OBJECTIVES: To evaluate skin dose differences between TPS (treatment planning system) calculations and TLD (thermo-luminescent dosimeters) measurements along with the dosimetric effect of applicator misplacement for patients diagnosed with gynecological (GYN) cancers undergoing brachytherapy. METHODS: The skin doses were measured using TLDs attached in different locations on patients’ skin in pelvic regions (anterior, left, and right) for 20 patients, as well as on a phantom. In addition, the applicator surface dose was calculated with TLDs attached to the applicator. The measured doses were compared with TPS calculations to find TPS accuracy. For the phantom, different applicator shifts were applied to find the effect of applicator misplacement on the surface dose. RESULTS: The mean absolute dose differences between the TPS and TLDs results for anterior, left, and right points were 3.14±1.03, 6.25±1.88, and 6.20±1.97 %, respectively. The mean difference on the applicator surface was obtained 1.92±0.46 %. Applicator misplacements of 0.5, 2, and 4 cm (average of three locations) resulted in 9, 36, and 61%, dose errors respectively. CONCLUSIONS: The surface/skin differences between the calculations and measurements are higher in the left and right regions, which relate to the higher uncertainty of TPS dose calculation in these regions. Furthermore, applicator misplacements can result in high skin dose variations, therefore it can be an appropriate quality assurance method for future research.