Purpose: There are various analysis methods for CT perfusion (CTP). Although the advantages of Bayesian estimation algorithms have been newly suggested, comparisons with other analysis methods on clinical data are still limited. In this study, we compared the Bayesian estimation method with the singular value decomposition (SVD) method in the evaluation of patients with acute cerebral infarction and examined its usefulness. Methods: CTP data from 13 patients with acute stroke were analyzed using the SVD and Bayesian estimation methods implemented in Vitrea. Evaluation of visual clarity of the ischemic area and quantitative values of the healthy side–affected side ratio using the mean values of the left and right region of interest (ROI) on the images were compared using the SVD and Bayesian estimation methods. Results: In visual evaluation, there were significant differences in CBV in four cases, and in CBF, MTT, and TTP in many cases. The healthy side–affected side ratio of the SVD and Bayesian estimation methods were as follows: CBF 1.19, 1.84; CBV 1.09, 1.02; MTT 1.12, 1.79; and TTP 1.48, 1.19. For CBF and MTT, the Bayesian estimation method had a larger ratio of the healthy side to the affected side, and for TTP, the SVD method had a larger ratio of the test side to the affected side. Conclusion: We suggest that the Bayesian estimation method is more useful than the SVD method for assessing CBF and MTT in CTP analysis of patients with acute stroke.

Introduction: X-ray penumbral width depends on the size of the detector in the off-axis ratio of medical linear accelerators. The use of detectors with appropriate sizes according to the irradiation field is recommended. However, when measuring dose distributions, the shape of the off-axis ratio differs depending on detectors even if the dose distribution remains unchanged. This study aims to calculate the penumbral width using multiple detectors and obtain the independent penumbral width according to irradiation size. Materials and Methods: Using the X-ray output from a medical linear accelerator, off-axis ratios in water were measured using nine types of detectors. Penumbral width was calculated from each measured off-axis ratio by linear approximation and determining the intercept for analysis. The experimental irradiation fields were square areas (1×1 cm² to 10×10 cm²). Penumbral widths were obtained from three types of detectors with different sensitive region widths of at least 1.2 mm. Results: The values estimated from the nine detectors were 2.51–4.07 and 2.93–4.70 mm for 6 and 10 MV X-rays, respectively. The penumbral width and variation due to detector size increased with the irradiation field. The results estimated from the three selected detectors varied within ±0.5 mm compared with those from the nine detectors and were generally consistent. The reliability of the results was evaluated by comparing with the results from past studies and Monte Carlo simulations. Conclusion: Calculation of the penumbral width can be done regardless of size for various detectors. Thus, dose distributions can be compared for the linear accelerator at different facilities.

Portable imaging in the NICU requires the assistance of a nurse, and the nurse is in close proximity to the X-ray tube, In all, 64 percent of our nurses thought that additional protective equipment was needed. Therefore, a radiation protection device was created and its usefulness was verified. A protective equipment of 0.13 mmPb with a width of 38 cm and a length of 70 cm was made and hung from the mono-tank X-ray unit of the mobile X-ray unit. The position of the nurse was set at 30 cm outward from the center of the irradiation field, and the protective effect was measured at three points: (a) the patient’s height, (b) 30 cm above the patient, and (c) 60 cm above the patient. For the imaging conditions, a 2-liter plastic bottle filled with water was placed in the incubator, and measurements were taken with an SID of 100 cm, irradiated field of 20.3 cm×25.4 cm, tube voltage of 58 kV, and tube current-time product of 10 mAs, which was converted to the actual imaging condition of 1 mAs. Based on the results obtained, a questionnaire survey was conducted on nurses’ thoughts for the protective equipment created for them. Only 3% reduction in height of (a) where no protective equipment is reached but (b) 50% and (c) 92%, respectively. In all, 82 percent of the nurses had a favorable impression of the new protective equipment. It is expected that the protective equipment designed to control lens dose and reduce anxiety of nurses will be useful.

Purpose: The purpose of this study was to investigate the optimal spatial resolution and temporal resolution of dynamic improved motion-sensitized driven-equilibrium steady-state free precession for visualization of respiratory-driven cerebrospinal fluid (CSF) dynamics. Methods: We investigated the differences in the visualization using the midsagittal cross-sections of nine healthy volunteers by three imaging conditions. (A: spatial resolution 0.49×0.49×5 mm, temporal resolution 1000 ms; B: 0.49×0.49×5 mm, 430 ms; and C: 0.78×0.78×5 mm, 200 ms). First, we calculated the CSF of the third and fourth ventricles and the signal-to-noise ratio (SNR) of the pons. Next, we calculated the signal intensity ratio (SIR) of the CSF flowing at 10 cm/s or more and the CSF flowing at 10 cm/s or less due to respiration. We also calculated the difference between the inspiration and expiration SIR. Furthermore, 1) the presence of flow in the third and fourth ventricles centered on the cerebral aqueduct and 2) the change in flow due to respiration was investigated by a three-point scale visual assessment by seven radiological technologists. Results: The SNR was the highest in A, the next highest in B, and the lowest in C in all cases. There were significant differences between A and B, and A and C in CSF of the third and fourth ventricles. However, there was no significant difference between B and C. The CSF signal intensity changed with respiration. The SIR of the third ventricle was higher on inspiration and lower on expiration. Conversely, the SIR of the fourth ventricle was lower on inspiration and higher on expiration. There was a significant difference between A and C and B and C in each SIR (p<0.05). The difference between inspiration and expiration SIR was the highest in B, the next highest in A, and the lowest in C in both the third and fourth ventricles. Significant differences were found between A and C, and between B and C (p<0.05). There was no significant difference in the presence of flow in the third and fourth ventricles centered on the cerebral aqueduct (p=0.264). On the other hand, there was a significant difference between the imaging conditions in the change in flow due to respiration, with B having a higher value than the others (p<0.001). Conclusion: The optimal spatial and temporal resolutions were 0.49×0.49×5 mm and 430 ms, respectively. The results also suggest that it is important to carefully set the imaging conditions for the spatial and temporal resolutions because of the use of phase dispersion in this method.

Since International Commission on Radiological Protection’s 2011 statement on tissue reaction was released, our hospital recommends wearing radioprotection glasses for radiation workers. The introduction of the lens dosimeter is examined in order to grasp the equivalent dose of the lens; however, the lens dosimeter was guessed to have influence on the equivalent dose management of the lens based on the characteristics and the attaching position. In this study, the validity of the lens dosimeter was verified by examining the characteristics and simulating the attaching position. In the simulation of rotating the human equivalent phantom, the indicated value of the lens was 0.18 mGy in condition as the human equivalent phantom confronted the radiation field, and the indicated value of the lens dosimeter at the corner of the eye was 0.17 mGy. By rotation, the indicated value of the lens proximal to the radiation field became higher compared to the distal value. The values indicated at the distal corner of the eye were below the indicated value of proximal lens, except for 180° rotation. The indicated value of the lens proximal to the radiation field became higher compared to the distal value, except for 180° rotation, and the maximal difference was 2.97 times at 150 degrees to the left. These results suggest the necessity of management of the lens proximal to the radiation field and attaching the lens dosimeter to the proximal corner of eye, since overestimation ensures safety at radiation management.

Purpose: Dual-energy computed tomography (DECT) system can generate virtual non-contrast (VNC) images. Although several reconstruction algorithms are defined, there are not many researches using deep learning image reconstruction (DLIR) algorithm. In this study, we evaluated the accuracy of the VNC image reconstruction under various conditions using DLIR algorithm. Methods: At first, each iodine insert with variable concentrations (2.0, 5.0, 10.0, 15.0 mg/ml) or diameters (2.0, 5.0, 10.0, 28.5 mm), or mixed insert including blood-mimicking material with iodine (iodine concentrations: 2.0, 4.0 mg/ml) was put in the center of the multi-energy CT phantom (Gammex, USA). This phantom was placed in the isocenter of DECT, and it scanned and reconstructed the VNC images. In addition, the VNC images were reconstructed with various display field of view (DFOV) sizes (240, 350 mm) or reconstruction algorithms (filtered back projection, advanced statistical iterative reconstruction, deep learning image reconstruction) for each iodine diameter. Attenuation values of these images (CT_VNC) were measured and assessed by placing a circular region of interest (ROI) on each insert. Results: CT_VNC form iodine inserts increased with iodine concentration became lower, whereas CT_VNC form blood plus iodine inserts were stable regardless of low iodine concentration. As iodine diameter became smaller, CT_VNC increased remarkably. CT_VNC remained steady even though reconstruction parameters were varied. Conclusion: In our study, the VNC image reconstruction using DLIR algorithm was affected by various conditions such as iodine concentration and size. In particular, its accuracy was reduced by the size of target.