Prediction of breast dose in chest CT examinations using adaptive neuro-fuzzy inference system (ANFIS).

In chest computed tomography (CT), the breasts located within the scan range receive a substantial radiation dose. Due to the risk of breast-related carcinogenesis, analyzing the breast dose for justification of CT examinations seems necessary. The main goal of this study is to overcome the limitations of conventional dosimetry methods, such as thermoluminescent dosimeters (TLDs) by introducing the adaptive neuro-fuzzy inference system (ANFIS) approach. In this study, the breast dose of 50 adult female patients who underwent chest CT examinations was measured directly by TLDs. Then, the ANFIS model was developed with four inputs including dose length product (DLP), volumetric CT dose index (CTDIvol), total mAs, and size-specific dose estimate (SSDE), and one output (TLD dose). Additionally, multiple linear regression (MLR) as a traditional prediction model was used for linear modeling and its results were compared with the ANFIS. The TLD reader results showed that the breast dose value was 12.37 ± 2.46 mGy. Performance indices of the ANFIS model, including root mean square error (RMSE) and correlation coefficient (R), were calculated at 0.172 and 0.93 for the testing dataset, respectively. Also, the ANFIS model had superior performance in predicting the breast dose than the MLR model (R = 0.805). This study demonstrates that the proposed ANFIS model is efficient for patient dose prediction in CT scans. Therefore, intelligence models such as ANFIS are suggested to estimate and optimize patient dose in CT examinations.

COMPARISON OF CBCT AND CT IN TERMS OF DOSE VALUE OF ORGANS AT RISK IN PARANASAL SINUS IMAGING.

Irradiated dose to the organs at risk surrounding the paranasal sinuses was compared in cone beam computed tomography (CBCT) and multi spiral computed tomography with respect to the organs' relative positions to the imaging field. A head and neck Alderson-Rando phantom equipped with thermoluminescence dosemeters pellets was irradiated according to three routine CBCT protocols and one protocol in multi spiral computed tomography. Dose value of organs outside the imaging field as well as those measured dose of organs inside the field were assessed. The highest measured doses were obtained from CT scan for most of the organs investigated in this study, whereas the lowest one was associated with the low-resolution mode of CBCT. Also, statistical analysis showed no significant differences between the dose values of out-of-field organs in all CBCT modes, whereas significant differences were observed between the radiation doses of CT and CBCT modes for all organs at risk inside and outside of the imaging field. CBCT is recommended on the basis of having a lower dose; however, the image qualities were the same in the two employed modalities, so the approach of lower dose can be made.

Monte Carlo calculation of buildup factors for 50 keV-15 MeV photons in tungsten up to 15 mean free paths.

Exposure buildup factor values of tungsten for a point isotropic source in energy range 0.05-15 MeV up to 15 mfp are computed using Monte Carlo N-Particle code. Buildup factors of this study and ANSI/ANS-6.4.3 at some selected energies and penetration depths are compared. Highest discrepancies are observed for high-energy and/or high penetration depths. Highest error occurs at 15 MeV, amounting to 32%. In the energy range 2-6 MeV, our results show smaller values for all penetration depths and vice versa at higher energies.

UNCERTAINTY EVALUATION IN MEASUREMENT OF THE PERSONAL DOSE EQUIVALENT AT NINE INDIVIDUAL MONITORING SERVICES IN ASIA AND THE PACIFIC REGION.

This paper presents the results of the evaluation of the uncertainty in measurement of the personal dose equivalent, Hp(10), at nine individual monitoring services (IMSs) in Asia and the Pacific region. Different types of passive dosemeters were type-tested according to the International Electrotechnical Commission 62387 requirements. The uncertainty in measurement was calculated using the Guide to the Expression of Uncertainty in Measurement approach. Expanded uncertainties ranged between 24 and 86% (average = 38%) for Hp(10) values around 1 mSv and between 14 and 40% (average = 27%) for doses around the annual dose limit, Hp(10) = 20 mSv. The expanded uncertainties were lower than the 1.5 factor in either direction proposed by the International Commission on Radiological Protection for doses near the relevant dose limits. This indicates an acceptable level of uncertainty for all participating IMSs. Uncertainty evaluation will help the IMSs to acknowledge the accuracy of their measurements.

CONSTRUCTION AND VALIDATION OF IN VITRO DOSE-RESPONSE CALIBRATION CURVE USING DICENTRIC CHROMOSOME ABERRATION.

Cytogenetic biodosimetry is a well-known method for quantifying the absorbed dose based on measuring biological radiation effects. To correlate the induced chromosomal abberrations with the absorbed dose of the individuals, a reliable dose-response calibration curve should be established. This study aimed to use frequencies and distributions of radiation-induced dicentric chromosome aberrations to develop a standard dose-response calibration curve. Peripheral blood samples taken from six male donors irradiated by an X-ray generator up to 4 Gy were studied. Three different blood samples were irradiated by known doses, then scored blindly for verification of the proposed calibration curve. Dose estimation was also carried out for three real overexposed cases. The results showed good accordance with the other published curves. The constructed dose-response curve provides a reliable tool for biological dosimetry in accidental or occupational radiation exposures.

RESULTS OF THE JOINT IAEA/ARPANSA INTERCOMPARISON EXERCISE ON WHOLE BODY DOSEMETERS FOR PHOTONS IN ASIA AND THE PACIFIC REGION.

An intercomparison exercise (IC) on whole body dosemeters to determine the quantity personal dose equivalent Hp (10) in photon radiation fields was jointly organised and conducted by the International Atomic Energy Agency (IAEA) and the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) for individual monitoring services (IMS) in Asia and the Pacific region. This was arranged to help the IMS in the region to achieve a more accurate dosimetry service and to improve their performance. Twenty-four IMS participated in this IC. Four sets of dosemeters were irradiated using X-ray and gamma radiation qualities at 0° and 20° angle of incidence, respectively. All the IMS provided results that were within the acceptable limits defined by the IAEA. However, only a minority of participants reported confidence intervals that included the reference dose, for each exposure scenario. For few systems, the overall performance could be significantly improved by reviewing calibration procedures.

Prediction of lung cells oncogenic transformation for induced radon progeny alpha particles using sugarscape cellular automata.

BACKGROUND: Alpha particle irradiation from radon progeny is one of the major natural sources of effective dose in the public population. Oncogenic transformation is a biological effectiveness of radon progeny alpha particle hits. The biological effects which has caused by exposure to radon, were the main result of a complex series of physical, chemical, biological and physiological interactions. The cellular and molecular mechanisms for radon-induced carcinogenesis have not been clear yet. METHODS: Various biological models, including cultured cells and animals, have been found useful for studying the carcinogenesis effects of radon progeny alpha particles. In this paper, sugars cape cellular automata have been presented for computational study of complex biological effect of radon progeny alpha particles in lung bronchial airways. The model has included mechanism of DNA damage, which has been induced alpha particles hits, and then formation of transformation in the lung cells. Biomarkers were an objective measure or evaluation of normal or abnormal biological processes. In the model, the metabolism rate of infected cell has been induced alpha particles traversals, as a biomarker, has been followed to reach oncogenic transformation. RESULTS: The model results have successfully validated in comparison with "in vitro oncogenic transformation data" for C3H 10T1/2 cells. This model has provided an opportunity to study the cellular and molecular changes, at the various stages in radiation carcinogenesis, involving human cells. CONCLUSION: It has become well known that simulation could be used to investigate complex biomedical systems, in situations where traditional methodologies were difficult or too costly to employ.

Estimation of gamma- and X-ray photons buildup factor in soft tissue with Monte Carlo method.

Buildup factor of gamma- and X-ray photons in the energy range 0.2-2MeV in water and soft tissue is computed using Monte Carlo method. The results are compared with the existing buildup factor data of pure water. The difference between soft tissue and water buildup factor is studied. Soft tissue is assumed to have a composition as H(63)C(6)O(28)N. The importance of such work arises from the fact that in medical applications of X- and gamma-ray, soft tissue is usually approximated by water. It is shown that the difference between water and soft tissue buildup factor is usually more than 10%. On the other hand, buildup factor in water resulted from Monte Carlo method is compared with the experimental data appearing in references. It seems there is around 10% error in the reference data as well.