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Purpose: Dynamic chest radiography (DCR) is a novel imaging technique used to noninvasively evaluate pulmonary perfusion. However, the standard DCR protocol, which is roughly adapted to the patient's body size, occasionally causes over‐ or underexposure, which could influence clinical evaluation. Therefore, we proposed a refined protocol by increasing the number of patient body mass index (BMI) categories from three to seven groups and verified its usefulness by comparing the image sensitivity indicators (S‐values) and entrance surface doses (ESDs) of the conventional protocol with those of our refined protocol. Methods: This retrospective observational study included 388 datasets (standing position, 224; supine position, 164) for the conventional protocol (December 2019–April 2021) and 336 datasets (standing position, 233; supine position, 103) for the refined protocol (June–November 2021). The conventional protocol (BMI‐3 protocol) divided the patients into three BMI groups (BMI < 17, 17≤BMI < 25, and BMI ≥ 25 kg/m2), whereas the refined protocol (BMI‐7 protocol) divided the patients into seven BMI groups (BMI < 17, 17 ≤ BMI < 20, 20 ≤ BMI < 23, 23 ≤ BMI < 26, 26 ≤ BMI < 29, 29 ≤ BMI < 32, and BMI ≥ 32 kg/m2). The coefficients of variation (CVs) for the S‐values and ESDs acquired using the two protocols were compared. Results: The CVs of the S‐values in the BMI‐7 protocol group were significantly lower than those in the BMI‐3 protocol group for the standing (28.8% vs. 16.7%; p < 0.01) and supine (24.5% vs. 17.7%; p < 0.01) positions. The ESDs of patients scanned using the BMI‐7 protocol were significantly lower than those scanned using the BMI‐3 protocol in the standing (1.3 vs. 1.1 mGy; p < 0.01) and supine positions (2.5 vs. 1.6 mGy; p < 0.01), although the mean BMI of the two groups were similar. Conclusion: We introduced the BMI‐7 protocol and demonstrated its standardized image quality and reduced radiation exposure in patients undergoing DCR. [ABSTRACT FROM AUTHOR]

Objectives: This study conducted a receiver operating characteristic (ROC) analysis by applying improved cluster signal-to-noise (CSN) analysis to digital intraoral radiographs and develop an observer-free method of analyzing image quality related to the observer performance in the detection task. Methods: Two aluminum step phantoms with a thickness interval of 1.0 mm were used for this study. One phantom had holes of increasing depth (from 0.05 to 0.35 mm) and the other had no holes. Phantom images were obtained under various exposure dose and image capture modes using a dental X-ray unit, a photostimulable phosphor imaging plate, and scanner system. These phantom images were analyzed using the FindFoci plugin in ImageJ software. Subsequently, true positive rates (TPRs) and false positive rates (FPRs) were calculated by analyzing phantom images with and without holes. We constructed ROC curves by plotting the TPRs against the FPRs and calculated the area under the ROC curve (AUC). Using the same phantom images with holes, eight observers assessed the number of detectable holes. Correlations between observer detection performance and AUC values were evaluated. Results: AUC values increased as the exposure dose increased and showed different tendencies depending on the image capture mode. The AUC values showed a high correlation with observer detection performance (r = 0.76). Conclusions: AUC values obtained from CSN analysis reflect image quality and replace the observer detection performance test of image quality. [ABSTRACT FROM AUTHOR]

This study aimed to develop an energy-based H p (3) measurement method using a solid-state detector (SSD). Incident and entrance surface air kerma were measured using an ionization chamber placed free-in-air and in front of an anthropomorphic or slab phantom. Subsequently, three SSDs were placed free-in-air, and half-value layer and readings were obtained. After measurements, an X-ray beam quality correction factor |$\left ({{k}}_{{Q},{{Q}}_{\mathbf{0}}}^{{SSD}}\right)$|⁠ , backscatter factor (BSF) and conversion factor from incident air kerma to H p (3) (C3) were determined. Then, the incident air kerma by SSD |$\left ({{K}}_{{a},{i}}^{{SSD}}\right)$|⁠ , H p (3) and H p (3)/ |${{K}}_{{a},{i}}^{{SSD}}$| were calculated. The |${{k}}_{{Q},{{Q}}_{\mathbf{0}}}^{{SSD}}$| was almost consistent for all SSDs. The C3 and BSF were found to increase as tube potential increased. The H p (3)/ |${{K}}_{{a},{i}}^{{SSD}}$| calculated with the anthropomorphic and slab phantoms were consistent within 2.1% and 2.6% for all SSDs, respectively. This method improves the energy dependence of H p (3) measurement and can estimate the H p (3) measurement error for dedicated H p (3) dosemeters. [ABSTRACT FROM AUTHOR]

Objectives: To quantify and validate the effect of pixel size on a digital intraoral radiographic system according to International Electrotechnical Commission standards through physical and visual evaluations., Methods: The digital intraoral radiographic system used was the photostimulable phosphor imaging plate and scanner system. The system had three image capture modes: high-speed (HS), high-resolution (HR), and super high-resolution (SHR) with different pixels. The physical characteristics of the system were evaluated using presampled modulation transfer function (MTF) and the normalized noise power spectrum (NNPS). An aluminum (Al) step phantom with different depths of holes was used to acquire images under various exposure conditions. The average number of perceptible holes from all steps was plotted against each exposure dose. The results were compared to analyze the effects of pixel size on image quality of intraoral radiographs., Results: The MTF was slightly higher with SHR than with HR and HS. The NNPS with SHR showed about a 40% decrease in magnitude compared to HS. The total number of perceptible holes in the Al step phantom was higher with SHR than with HS and HR in all exposure conditions., Conclusions: The MTF and NNPS obtained with different pixel size could be quantified by physical evaluation, and the differences were visually validated with Al step phantom. The SHR mode has the potential to decrease the radiation dose without compromising the image quality.

Because of the more advanced and more complex procedures in interventional radiology, longer treatment times have become necessary. Therefore, it is important to determine the exposure doses received by operators and patients. The aim of our study was to evaluate an experimental production wireless dose monitoring system for pulse radiation in diagnostic X-ray. The energy, dose rate, and pulse fluoroscopy dependence were evaluated as the basic characteristics of this system for diagnostic X-ray using a fully digital fluoroscopy system. The error of 1 cm dose equivalent rate was less than 15% from 35.1 keV to 43.2 keV with energy correction using metal filter. It was possible to accurately measure the dose rate dependence of this system, which was highly linear until 100 μSv/h. This system showed a constant response to the pulse fluoroscopy. This system will become useful wireless dosimeter for the individual exposure management by improving the high dose rate and the energy characteristics.