The aim of this study was to inspect the usefulness of relative artifact index (AI_r), which divided artifact index (AI) by standard deviation of the noise image for noise-independent evaluation of the streak artifact in computed tomography images. A water phantom without/with a cylindrical phantom filled with diluted contrast medium was scanned with different tube voltages (100/120/140 kV) and radiation doses (5/10/20 mGy), then images were reconstructed with different kernels (B10/30/50f). AI, location parameter in Gumbel method and AI_r were measured in each condition and compared. The higher tube voltage or radiation dose or lower spatial resolution kernel, the lower quantitative values were presented by both AI and Gumbel method. AI_r showed quantitative values independent of radiation dose and kernel, and substantial artifact amounts affected only by tube voltage. Our results showed AI_r can evaluate quantitative artifact amount independent of image noise.

Medical staffs like radiological technologists, doctors, and nurses are at an increased risk of exposure to radiation while assisting the patient in a position or monitor contrast medium injection during computed tomography (CT). However, methods to protect medical staff from radiation exposure and protocols for using radiological protection equipment have not been standardized and differ among hospitals. In this study, the distribution of scattered X-rays in a CT room was measured by placing electronic personal dosimeters in locations where medical staff stands beside the CT scanner gantry while assisting the patient and the exposure dose was measured. Moreover, we evaluated non-uniform exposure and revealed effective techniques to reduce the exposure dose to medical staff during CT. The dose of the scattered X-rays was the lowest at the gantry and at the examination table during both head and abdominal CT. The dose was the highest at the trunk of the upper body of the operator corresponding to a height of 130 cm during head CT and at the head corresponding to a height of 150 cm during abdominal CT. The maximum dose to the crystalline lens was approximately 600 μSv during head CT. We found that the use of volumetric CT scanning and X-ray protective goggles, and face direction toward the gantry reduced the exposure dose, particularly to the crystalline lens, for which lower equivalent dose during CT scan has been recently recommended in the International Commission on Radiological Protection Publication 118.

Diffusion tensor imaging (DTI) of skeletal muscles has been reported as capable to characterize physiological properties, tissue microstructure and architectural organization. However, the DTI indices may vary with the contractile state of the muscles, and in the rotator cuff muscles, a change in forearm position can result in variation of the DTI indices. The purpose of this study was to examine the influence of forearm position on the major DTI indices of the rotator cuff muscles. The DTI of right rotator cuff was acquired under the neutral position and external and internal rotation of the forearm in nine healthy volunteers. Fractional anisotropy (FA) and mean diffusivity (MD) of each muscle were calculated and compared among the three forearm positions. FA and MD were significantly different between external and internal rotation in infraspinatus, teres minor and subscapularis (p<0.05). We considered that this difference was due to the change in cross-sectional area of muscle fibers based on their contractile state. That is, when the muscle is contracted, its cross-sectional area is increased and the muscle fiber density in the short axis direction becomes less. This causes a change in FA and MD due to increase in λ₂ and λ₃ through increased diffusion of intercellular water in the short axis direction. In conclusion, the DTI indices of the rotator cuff muscles are affected by the forearm position.

We aimed to develop a computerized method for the detection of radiopaque markers, such as R and L in chest and abdomen radiography by using the generalized Hough transform and the template matching. To develop the computerized method, we used 200 chest and abdomen images in our institution as training cases. First, two template images for R and L markers were created with the same exposure condition as a chest X-ray. Following various image processing, such as edge detection, thinning and Hough transformed, a look-up table that consisted of distance and direction pairs was built for the generalized Hough transform. All training images were preprocessed with median filter, edge detection, binarization, thinning, back ground removal and labeling. For candidates of markers that were detected as true positive or false positive, their vote and cross-correlation were calculated with the generalized Hough transform. To evaluate this proposed method, a validation test was performed with another database that consisted of 800 chest and abdomen images by use of Mahalanobis distance based on vote and cross-correlation in statistics. The precision of detecting the radiopaque markers for 800 test images was 99.9%. In addition, this method worked out well for some specific images in which markers were overlapped with a human body.

Purpose: Hybrid inverse treatment planning optimization (HIPO) is a new optimization tool for brachytherapy. We verified its utility using treatment plans for combined intracavitary and interstitial brachytherapy in cervical cancer. Materials & Methods: We compared the manually optimized plan and the plan optimized using HIPO. The plan using HIPO was optimized with three different methods: needle only, tandem and needle, and all applicators. The dose volume histogram (DVH) parameters such as D₉₀ of high risk clinical target volume (HR-CTV) and D_2cc of OAR (rectum, sigmoid colon and bladder) were used to evaluate each treatment plan. Results: The D₉₀ of HR-CTV in most plans was received more than 600 cGy. In addition, the D_2cc of OAR also was less than the tolerance dose on the average of all plans. However, the D_2cc of the rectum and bladder treatment plans optimized only with needles was significantly higher than other plans. Conclusions: The treatment plans used in clinical practice and obtained by HIPO have similar dose distributions and DVH parameters. Moreover, the time needed to create treatment plan was reducing by HIPO. We suggest that HIPO will be an effective tool in treatment planning.

The simulation study was conducted for the new venous catheter with side holes of contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) to evaluate the infusion pressure on four contrast media and several injection speeds. All infusion pressure of the new venous catheter with side holes were less than 15 kg/cm² as limitation of extension tube and also reduced the infusion pressure by 15% at the maximum compared to the catheter with single hole. The results suggest that the new venous catheter with side holes can reduce the infusion pressure by power injection of contrast-enhanced CT and MRI.

The purpose of this study was to compare the time-intensity curve (TIC) on multiphase contrast-enhanced breast magnetic resonance imaging (MRI) between Gadobenatedimeglumine (Gd-DTPA) and Gadobutrol. We assessed the images of 53 cases obtained from MRI that had malignant findings by pathology from October 2015 to October 2016 in our institute. Gd-DTPA and Gadobutrol were administrated in 16 and 37 cases, respectively. The TIC of the lesion was classified according to the Kuhl’s method (type I: persistent pattern, type II: plateau pattern and type III: washout pattern). Type III was the most common TIC pattern in both the groups (Gd-DTPA, 12 cases; Gadobutrol, 18 cases). Type II was the second common TIC pattern in Gadobutrol group (12 cases). As a result, there was no significant difference in TIC analysis between Gd-DTPA and gadobutrol. In conclusion, the contrast between Gd-DTPA and Gadobutrol contrast media did not differ in TIC pattern of multiphasic contrast-enhanced breast MRI.

The purpose of this study was to evaluate the effect of a hybrid-type iterative reconstruction method on Z-score mapping of hyperacute stroke in unenhanced computed tomography (CT) images. We used a hybrid-type iterative reconstruction [adaptive statistical iterative reconstruction (ASiR)] implemented in a CT system (Optima CT660 Pro advance, GE Healthcare). With 15 normal brain cases, we reconstructed CT images with a filtered back projection (FBP) and ASiR with a blending factor of 100% (ASiR100%). Two standardized normal brain data were created from normal databases of FBP images (FBP-NDB) and ASiR100% images (ASiR-NDB), and standard deviation (SD) values in basal ganglia were measured. The Z-score mapping was performed for 12 hyperacute stroke cases by using FBP-NDB and ASiR-NDB, and compared Z-score value on hyperacute stroke area and normal area between FBP-NDB and ASiR-NDB. By using ASiR-NDB, the SD value of standardized brain was decreased by 16%. The Z-score value of ASiR-NDB on hyperacute stroke area was significantly higher than FBP-NDB (p<0.05). Therefore, the use of images reconstructed with ASiR100% for Z-score mapping had potential to improve the accuracy of Z-score mapping.