Radiation exposure in cone beam CT measured using a MOSFET and RPLGD dosimeter and Monte Carlo simulation in phantom.

BACKGROUND: Due to the wide application of the cone beam computed tomography (CBCT) in clinical practice, it is important to assess radiation dose of CBCT more accurately and efficiently in different clinical applications. OBJECTIVE: This study aims to calculate effective and absorbed doses in CBCT measured in an anthropomorphic phantom using computer-based Monte Carlo (PCXMC) software, and to conduct comparative evaluations of MOSFET (metal- oxide- semiconductor field-effect transistor) and radiophotoluminescence glass dosimeters (RPLGD). METHODS: Effective and absorbed organ doses are compared with those obtained using MOSFET and RPLGD dosimetry in an anthropomorphic phantom given the same exposure settings. Effective and absorbed organ doses from CBCT during scout and main projections are calculated using PCXMC and PCXMCRotation software, respectively. RESULTS: The mean effective dose from CBCT calculated using PCXMC software is 233.8µSv, while the doses calculated using dosimetry (MOSFET and RPLGD) are 266.67µSv and 268.78µSv, respectively. The X-ray source variation is 0.79%. The prescription limits based on the Friedman test for MOSFET and RPLGD pre-points (i.e., in an analytical analysis of diagnostic names in CBCT) are not statistically significant. The calculated correlation coefficient between MOSFET- and RPLGD-derived absorbed dose values with respect to a field of view CBCT parameter of 17×13.5 mm is r = 0.8623. CONCLUSIONS: The study demonstrates that the PCXMC software may be used as an alternative to MOSFET and RPLGD dosimetry for effective and absorbed organ dose estimation in CBCT conducted with a large FOV in an anthropomorphic phantom.

Evaluation of image quality and radiation dose by adaptive statistical iterative reconstruction technique level for chest CT examination.

The purpose of this research is to determine the adaptive statistical iterative reconstruction (ASIR) level that enables optimal image quality and dose reduction in the chest computed tomography (CT) protocol with ASIR. A chest phantom with 0-50 % ASIR levels was scanned and then noise power spectrum (NPS), signal and noise and the degree of distortion of peak signal-to-noise ratio (PSNR) and the root-mean-square error (RMSE) were measured. In addition, the objectivity of the experiment was measured using the American College of Radiology (ACR) phantom. Moreover, on a qualitative basis, five lesions' resolution, latitude and distortion degree of chest phantom and their compiled statistics were evaluated. The NPS value decreased as the frequency increased. The lowest noise and deviation were at the 20 % ASIR level, mean 126.15 ± 22.21. As a result of the degree of distortion, signal-to-noise ratio and PSNR at 20 % ASIR level were at the highest value as 31.0 and 41.52. However, maximum absolute error and RMSE showed the lowest deviation value as 11.2 and 16. In the ACR phantom study, all ASIR levels were within acceptable allowance of guidelines. The 20 % ASIR level performed best in qualitative evaluation at five lesions of chest phantom as resolution score 4.3, latitude 3.47 and the degree of distortion 4.25. The 20 % ASIR level was proved to be the best in all experiments, noise, distortion evaluation using ImageJ and qualitative evaluation of five lesions of a chest phantom. Therefore, optimal images as well as reduce radiation dose would be acquired when 20 % ASIR level in thoracic CT is applied.

Inter-comparison of 18F-FDG PET/CT standardized uptake values in Korea.

The number of PET/CT tests for diagnosing and treating tumors are increasing every year, and thus it is considered necessary to compare PET/CT images among medical institutions or among different PET/CT systems within the same medical institution. We present to get the variation of standardized uptake values (SUV) among PET/CT systems, to derive an SUV calibration table that enables quantitative comparison of PET/CT systems, and to test the usefulness of the calibration table through comparing patient's SUV with the SUV calibration table. The correlation coefficients that inter-compared the calibration constants of normal patients and the calibration constants of the mean standardized uptake value with the calibration constants of the standardized uptake value of phantom are 0.88938 (P<0.0001).