[Physical Properties of Small Focal Spot Imaging with Deep Learning Reconstruction in Chest-abdominal Plain CT].

PURPOSE: The aim of this study was to compare the physical properties of small focal spot imaging with deep learning reconstruction (DLR) and small or large focal spot imaging with hybrid iterative reconstruction (IR) in chest-abdominal plain computed tomography. METHOD: In small focal spot imaging using DLR and hybrid IR, tube currents were set at 350 mA. For the large focal spot imaging using hybrid IR, the tube current was set at 360, 400, 450, and 500 mA. The spatial frequencies with 50% task transfer function (TTF) for delrin and acrylic were calculated to compare spatial resolution properties for lung and soft tissue in the chest. Additionally, the low-contrast object-specific contrast-to-noise ratio (CNRLO) was measured as noise property was measured for a 7-mm module with a CT value contrast of 10 HU in the abdomen. RESULT: Spatial frequencies with 50% TTF for delrin and acrylic were found to be greater in small focal spot imaging using DLR compared to those in small and large focal spot imaging using hybrid IR. Moreover, the CNRLO obtained from small focal spot imaging with DLR was also nearly equivalent to that of large focal spot imaging with hybrid IR at tube currents of 450 and 500 mA. CONCLUSION: In chest-abdominal plain computed tomography, small focal spot imaging with DLR has been demonstrated to exhibit greater spatial resolution properties compared to small and large focal spot imaging with hybrid IR, with equivalent or better noise performance.

[Contrast-enhancement Effects of Dual-peak Contrast Medium Injection Method Using Bolus-tracking Technique in Coronary and Aorta CT Angiography].

OBJECTIVE: We compared the contrast-enhancement effects of the coronary arterial phase and the aortic phase in coronary and aorta computed tomography angiography (CA-CTA) using the bolus-tracking technique-based single-peak contrast medium injection (BT-SPI) method and the bolus-tracking technique-based dual-peak contrast medium injection (BT-DPI) method. METHOD: CA-CTA images were acquired from 30 patients, using BT-SPI and BT-DPI. Regions of interest were selected in the right ventricle and ascending aorta during the coronary arterial phase, and in the aorta during the aortic phase to obtain mean CT values. The mean CT values were used to compare the contrast-enhancement effects of BT-SPI and BT-DPI. RESULTS: The mean CT value of the right ventricle during the coronary arterial phase obtained using BT-SPI (320 Hounsfield unit [HU]) and BT-DPI (83 HU) was significantly different (p<0.05). Using BT-SPI and BT-DPI, the mean CT values of the ascending aorta during the coronary arterial phase were 361 HU and 379 HU, respectively, and those of the aorta during the aortic phase were 436 HU and 437 HU, respectively. The difference in the mean CT values for the aorta between BT-SPI and BT-DPI during the coronary arterial and aortic phases was insignificant. CONCLUSION: The retention of the contrast medium in the right ventricle during the coronary arterial phase using BT-DPI was lower than that using BT-SPI. BT-DPI showed substantial contrast-enhancement effects in both the coronary arterial and aortic phases.

Optimizing radiation dose by varying age at pediatric temporal bone CT.

We performed retrospective (first-step) and prospective (second-step) studies to evaluate the body information and noise on temporal bone computed tomography (CT) images in efforts to identify the optimized tube current yielding the greatest reduction in the radiation exposure of pediatric patients undergoing temporal bone CT studies. Our first-step study included 90 patients subjected to temporal bone CT. We recorded displayed volume CT dose index (CTDIvol), displayed dose-length product (DLP), image noise, and the patient age and sex. We then calculated the optimized tube current value with and without IR corresponding to the children's age based on the ratio of the noise on images from individuals older than 18 years. In our second-step study, we enrolled 23 pediatric patients and obtained CT scans using our optimized protocol. In both studies we applied identical analysis techniques. The diagnostic image quality was confirmed reading reports and a neuroradiologist. Our first-step study indicated that the mean image noise in children assigned to five ascending age groups from 2 to 12 years ranged from 167.59 to 211.44 Hounsfield units (HU). In the second-step study, the mean image noise in each age group was almost the same as the expected noise value and the diagnostic image quality was acceptable. The dose reduction was ranged from 57.5% to 37.5%. Optimization of the tube current-time product allows a radiation reduction without a loss in image quality in pediatric patients undergoing temporal bone CT.

Patient-specific tube-voltage selection at coronary CT angiography based on the combination of X-ray attenuation on scout views and body mass index: how can appropriate radiation dose be achieved?

BACKGROUND: Body weight, body mass index (BMI), and scout X-ray radiographic attenuation can be used to predict image noise on computed tomographic coronary angiography (CTCA) images. PURPOSE: To use a formula to predict patient-specific image noise and then select an appropriate CTCA patient-specific tube voltage for better radiation control. MATERIAL AND METHODS: Forty-eight patients who underwent CTCA imaging at 120 kVp were reviewed, and their patient information and scouting X-ray radiographic attenuations were recorded to identify the best correlations between patient data and image noise and to develop a predicted image noise formula. Subsequently, 54 patients subjected to scanning at 100 or 120 kVp, depending on the noise predicted by our formula, were prospectively studied. Two radiologists visually assessed the image quality of the right coronary artery (RCA), left anterior descending artery (LAD), and left circumflex artery (LCX) by consensus readings. RESULTS: The predicted image noise = 0.939 BMI + 0.025 scouting attenuation + 20.16. The median value of the overall image noise was 30.55 HU at 120 kVp and 29.85 HU at 100 kVp. The mean visual evaluation scores at 100 and 120 kVp were 3.25 and 3.24 for the proximal RCA, 3.40 and 3.26 for the proximal LAD, and 3.30 and 3.15 for the proximal LCX, respectively. CONCLUSION: The BMI and scouting X-ray radiographic attenuation can be combined to predict the CTCA image noise. Our prediction formula is useful for deciding when to switch from the 120- to the 100-kVp technique.