Comparison of qualitative and fully automated quantitative tools for classifying severity of white matter hyperintensity.

OBJECTIVE: In this study, we aimed to compare the Fazekas scoring system and quantitative white matter hyperintensity volume in the classification of white matter hyperintensity severity using a fully automated analysis software to investigate the reliability of quantitative evaluation. MATERIALS AND METHODS: Patients with suspected cognitive impairment who underwent medical examinations at our institution between January 2010 and May 2021 were retrospectively examined. White matter hyperintensity volumes were analyzed using fully automated analysis software and Fazekas scoring (scores 0-3). Using one-way analysis of variance, white matter hyperintensity volume differences across Fazekas scores were assessed. We employed post-hoc pairwise comparisons to compare the differences in the mean white matter hyperintensity volume between each Fazekas score. Spearman's rank correlation test was used to investigate the association between Fazekas score and white matter hyperintensity volume. RESULTS: Among the 839 patients included in this study, Fazekas scores 0, 1, 2, and 3 were assigned to 68, 198, 217, and 356 patients, respectively. White matter hyperintensity volumes significantly differed according to Fazekas score (F=623.5, p<0.001). Post-hoc pairwise comparisons revealed significant differences in mean white matter hyperintensity volume between all Fazekas scores (p<0.05). We observed a significantly positive correlation between the Fazekas scores and white matter hyperintensity volume (R=0.823, p<0.01). CONCLUSIONS: Quantitative white matter hyperintensity volume and the Fazekas scores are highly correlated and may be used as indicators of white matter hyperintensity severity. In addition, quantitative analysis may be more effective in classifying advanced white matter hyperintensity lesions than the Fazekas classification.

Auto-evaluation of skull radiograph accuracy using unsupervised anomaly detection.

BACKGROUND: Radiography plays an important role in medical care, and accurate positioning is essential for providing optimal quality images. Radiographs with insufficient diagnostic value are rejected, and retakes are required. However, determining the suitability of retaking radiographs is a qualitative evaluation. OBJECTIVE: To evaluate skull radiograph accuracy automatically using an unsupervised learning-based autoencoder (AE) and a variational autoencoder (VAE). In this study, we eliminated visual qualitative evaluation and used unsupervised learning to identify skull radiography retakes from the quantitative evaluation. METHODS: Five skull phantoms were imaged on radiographs, and 1,680 images were acquired. These images correspond to two categories: normal images captured at appropriate positions and images captured at inappropriate positions. This study verified the discriminatory ability of skull radiographs using anomaly detection methods. RESULTS: The areas under the curves for AE and VAE were 0.7060 and 0.6707, respectively, in receiver operating characteristic analysis. Our proposed method showed a higher discrimination ability than those of previous studies which had an accuracy of 52%. CONCLUSIONS: Our findings suggest that the proposed method has high classification accuracy in determining the suitability of retaking skull radiographs. Automation of optimal image consideration, whether or not to retake radiographs, contributes to improving operational efficiency in busy X-ray imaging operations.

[Creation of Brain Parenchymal Equivalent Phantom for Diffusion Weighted Image Using Microwave Oven: A Different Heating Method].

The acute micro cerebral infarction phantom was created to evaluate the detectability of acute micro cerebral infarction and optimize scan conditions in magnetic resonance imaging (MRI) examinations. The creation of the brain parenchyma phantom requires a hot stirrer that can be heated and stirred simultaneously. However, few hospitals and facilities have hot stirrers. The aim of our study was to use a microwave oven instead of a hot stirrer for the creation of a brain parenchyma phantom. Five phantoms using a hot stirrer and five phantoms using a microwave oven were created. The phantom creation time, T2 value, apparent diffusion coefficient (ADC) value, uniformity, and reproducibility of MR images were compared between the two creation methods. The phantom creation time, when using a microwave oven was 108±8 minutes, which was significantly shorter than that of 213± 48 minutes when using a hot stirrer. T2 values, ADC values, uniformity, and reproducibility were not significantly different. Therefore, it is easier to create an acute micro cerebral infarction phantom using a microwave oven compared to a hot stirrer.

High Sensitivity Monitoring Device for Onboard Measurement of Dimethyl Sulfide and Dimethylsulfoniopropionate in Seawater and an Oceanic Atmosphere.

An automated device has been developed to measure aqueous dimethyl sulfide (DMSaq), its precursor dimethylsulfoniopropionate (DMSP), and atmospheric gaseous dimethyl sulfide (DMSg). In addition to having a role in the oceanic atmosphere, DMS and DMSP have recently gained substantial interest within the biosciences and are suspected as chemoattractants for predators searching for prey. To provide the spatial resolution relevant for biogeochemical functions, fast and on-site analysis of these compounds is an important technique. The system described measures the dimethyl sulfur compounds by sequential vaporization of DMSaq and DMSP to their gas phase, which is then analyzed by chemiluminescence detection (SVG-CL). The device has five analysis modes (full, DMS, water, gas, and DMSP mode) that can be selected by the user depending on the required analyte or desired sampling rate. Seawater analyses were performed by the developed SVG-CL system and, simultaneously, by an ion molecule reaction-mass spectrometer and a gas chromatograph-flame photometric detector to verify quantitative analysis results. Results obtained by the new method/device agreed well with those by the other methods. Detection limits of the SVG-CL system are 0.02 ppbv and 0.04 nM for DMSg and DMSaq/DMSP, respectively, which are much better than those of the mass spectrometer. The SVG-CL system can be easily installed and operated on a boat. Spatial variability in DMS and DMSP off the coast of Japan were obtained, showing significant changes in the concentrations of the components at the brackish/saline water interface and at the channel between the closed and open seas.

Incidence and risk factors of hepatocellular carcinoma change over time in patients with hepatitis C virus infection who achieved sustained virologic response.

AIM: In patients with chronic hepatitis C, hepatocellular carcinoma (HCC) occurs at a certain frequency, even if a sustained virologic response (SVR) is achieved by antiviral treatment. Old age, liver fibrosis, and high post-treatment α-fetoprotein (AFP) level are typical risk factors of post-SVR HCC. We examined whether the frequencies and factors of HCC in patients with an SVR achieved from interferon treatment changed. Methods Among patients prospectively registered for pegylated interferon and ribavirin treatment, 2021 with an SVR without HCC development during the treatment period were followed up. The mean observation period was 49.5 ± 26.2 months. RESULTS: The multivariable Cox regression analysis showed that older age, diabetes mellitus, advanced liver disease, and higher post-treatment AFP level were the independent risk factors throughout the observation period. The annual occurrence rate of HCC was 0.74% in the third year, 0.54% in the fourth year, and 0.40% in the fifth year; it gradually decreased from the third year. Because the time course hazards for HCC changed at 48 months, we separately analyzed its risk factors before and after this change point. The multivariable Cox regression analysis showed that the four above-mentioned factors were significantly related to HCC development within 4 years. Conversely, the univariable Cox regression analysis only identified diabetes mellitus as a significant factor for HCC development after 4 years. CONCLUSION: The frequency of HCC in hepatitis C patients who achieved an SVR from interferon treatment decreased during the observation period, and its risk factors changed between the early and late periods.

Sonographic sequential change of the anteroinferior labrum following arthroscopic Bankart repair: quantitative and qualitative assessment.

OBJECTIVE: Although arthroscopic Bankart repair is widely performed, little is known concerning the healing process of the Bankart lesion. This study aimed to describe the sonographic sequential change of the anteroinferior labrum following arthroscopic Bankart repair, both quantitatively and qualitatively. MATERIALS AND METHODS: Twenty-five subjects who had undergone arthroscopic Bankart repair were investigated using a sonographic diagnostic device equipped with shear-wave elastographic technology. In addition to measuring the elasticity of the anteroinferior labrum, the B-mode echogram of the anteroinferior labrum was classified into three grades based on the relative echogenicity. Assessment was performed in the affected shoulder 1, 2, 3, 4, 5, 6, and 12 months postoperatively and in the contralateral shoulder 1 month postoperatively for the control. RESULTS: The mean elasticity of the anteroinferior labrum in the affected shoulder 1 and 2 months postoperatively was significantly lower than in the contralateral shoulder (p < 0.001 for both). However, no significant difference was found after 3 months postoperatively. B-mode echograms of the anteroinferior labrum in the contralateral shoulder were classified as grade 0 in all subjects (100%), whereas the percentage of grade 0s in the affected shoulder was 0, 4, 96, and 100% at 1, 2, 3, and 4 months postoperatively. CONCLUSION: Both quantitative and qualitative assessment of repaired anteroinferior labrum using ultrasound became comparable with the contralateral shoulder 3-4 months postoperatively. Ultrasound is a useful decision-supporting tool to prescribe postoperative rehabilitation protocol following arthroscopic Bankart repair, although functional recovery should also be evaluated on an individual basis.

Effectiveness of an e-Learning Platform for Image Interpretation Education of Medical Staff and Students.

Medical staff must be able to perform accurate initial interpretations of radiography to prevent diagnostic errors. Education in medical image interpretation is an ongoing need that is addressed by text-based and e-learning platforms. The effectiveness of these methods has been previously reported. Here, we describe the effectiveness of an e-learning platform used for medical image interpretation education. Ten third-year medical students without previous experience in chest radiography interpretation were provided with e-learning instructions. Accuracy of diagnosis using chest radiography was provided before and after e-learning education. We measured detection accuracy for two image groups: nodular shadow and ground-glass shadow. We also distributed the e-learning system to the two groups and analyzed the effectiveness of education for both types of image shadow. The mean correct answer rate after the 2-week e-learning period increased from 34.5 to 72.7%. Diagnosis of the ground glass shadow improved significantly more than that of the mass shadow. Education using the e-leaning platform is effective for interpretation of chest radiography results. E-learning is particularly effective for the interpretation of chest radiography images containing ground glass shadow.

Comparison of medical image classification accuracy among three machine learning methods.

BACKGROUND: Low-quality medical images may influence the accuracy of the machine learning process. OBJECTIVE: This study was undertaken to compare accuracy of medical image classification among machine learning methods, as classification is a basic aspect of clinical image inspection. METHODS: Three types of machine learning methods were used, which include Support Vector Machine (SVM), Artificial Neural Network (ANN), and Convolution Neural Network (CNN). To investigate changes in accuracy related to image quality, we constructed a single dataset using two different file formats of DICOM (Digital Imaging and Communications in Medicine) and JPEG (Joint Photographic Experts Group). RESULTS: The JPEG format contains less color information and data capacity than the DICOM format. CNN classification was accurate for both datasets, whereas SVM and ANN accuracy decreased with the loss of data from DICOM to JPEG formats. CONCLUSIONS: CNN is more accurate than conventional machine learning methods that utilize the manual feature extraction.

[The Novel Evaluation Method of Geometric Distortion for 3D-MRI].

Recently, many imaging methods are developed in magnetic resonance imaging and in particular, the release of the 3D acquisition method is remarkable. The image distortion often becomes the problem by the gradient echo method and the echo planar imaging (EPI) -based method, but the image distortion of the 3D acquisition is not established. A purpose of this study is to examine the utility of the novel evaluation method of the image distortion for the 3D acquisition image. The spin echo image was used as a criteria image, and EPI was used as a target image for 3D acquisition imaging. Image J was used for the image processing. The value that divided the volume of the different shape of criteria image and the target image by the volume of the criteria image was defined as a distortion rate. Hence, we refer this method to the volume method. It is reported that the distortion rate of the EPI is proportional to a rectangle rate of rectangular field of view (RFOV). The distortion rate of the volume method for 50-100% of rectangle ratio was compared with the theoretical value. In addition, the dependence by the threshold of the binarization was considered. Furthermore, the comparison with the NEMA (National Electrical Manufacturers Association) method was carried out. As a result, the distortion rate decreased according to a rectangular rate of RFOV by the volume method, and the numerical value was equal with a theoretical value. In addition, the distortion rate did not have the effect by the thresholding of binarizing. The volume method had less error of measurement than the NEMA method.

Ultra-deep sequencing analysis of resistance-associated variants during retreatment with simeprevir-based triple therapy after failure of telaprevir-based triple therapy in patients with genotype 1 hepatitis C virus infection.

AIM: Simeprevir (SMV)-based triple therapy is an effective retreatment option following failure of telaprevir (TVR)-based triple therapy. However, it is unclear whether the persistence of resistance-associated variants (RAVs) induced by TVR-based therapy may reduce the treatment effect of SMV-based therapy. METHODS: The factors associated with the treatment effect, including RAVs in the NS3 region, were examined in 21 patients with genotype 1b HCV infection who were treated with SMV-based therapy after failure of TVR-based therapy. Ultra-deep sequencing was carried out to detect RAVs. RESULTS: With the exception of one patient who discontinued treatment owing to adverse events, the sustained virologic response (SVR) rate was 50% (10/20). Ultra-deep sequencing at the start of SMV-based therapy revealed that TVR-resistant variants were detected in six patients (29%), and no variants were observed at position 168. Cross-resistance between TVR and SMV with low frequency was detected in only one patient, and this patient achieved SVR. Higher SVRs for SMV-based therapy were attained in patients who discontinued treatment owing to the adverse effects of prior TVR-based therapy (discontinuation 100% vs. non-discontinuation 29%, P = 0.005), and patients who relapsed following prior pegylated interferon plus ribavirin therapy (relapse 100% vs. non-response 20%, P = 0.007). CONCLUSIONS: In this study, ultra-deep sequencing analysis revealed that TVR and/or SMV-resistant variants may have no influence on the effect of SMV-based therapy after failure of TVR-based therapy. Patients who discontinued treatment owing to adverse effects of TVR-based therapy and relapsers to previous pegylated interferon/ribavirin therapy would be good candidates for retreatment with SMV-based therapy.

Optimization method of MRI scan parameters of a double inversion recovery sequence using a T1 map and a developed analysis algorithm.

BACKGROUND: Optimizing scan parameters for double inversion recovery (DIR) sequences remains difficult. OBJECTIVE: To evaluate a new method for optimizing DIR sequence scan parameters using T1 mapping and a newly developed analysis algorithm. METHODS: Twelve healthy volunteers underwent T1 mapping and DIR magnetic resonance imaging. The following steps were used for image optimization including: 1) measurement of gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) T1 values to create a T1 map; 2) calculation of optimized scan parameters by using a developed analysis algorithm; 3) performance assessment of DIR magnetic resonance imaging by using the calculated optimized imaging parameters. Additionally, we used scan parameters from previous studies to obtain DIR images in order to evaluate our new method. The contrast between GM and suppressed tissues was compared between these images and those obtained using the optimized parameters. RESULTS: Using our optimization method, WM and CSF regions were suppressed uniformly for all scan conditions. The contrast was significantly higher in images obtained using this optimization method compared to those obtained using previously published parameters (p < 0.01). CONCLUSIONS: It is possible to obtain superior DIR images by using an optimization method that involves T1 mapping and a newly developed analysis algorithm.

Relationship between Blurring and Refocus Flip Angle in 3D-double Inversion Recovery MRI.

It is important to optimize imaging parameters in 3D-double inversion recovery (DIR) magnetic resonance imaging (MRI) for detecting cortical micro lesions. However, inadequate parameters markedly raise blurring in 3DDIR MRI. The purpose of this study was to evaluate the relationship between the blurring and refocus flip angle (RFA) in 3D-DIR MRI. White matter attenuated inversion recovery (WAIR) images as a test sample were obtained by 1.5T MRI with various RFA settings (30°, 40°, 60°, 100°, 140°, 180°, and variable refocus flip angle (VRFA)). Optimal RFA was evaluated using Scheffé's method (Nakaya changing method) by five observers. The results of average preferences indicated that RFA settings of under the 60° of RFA or VRFA suppressed the blurring in 3DDIR MRI. The yard sticks of RFAs of 30° and 40° were significantly higher than the yard sticks of other RFAs (p<0.01). For detecting cortical microlesions, it is very important to obtain WAIR images with no blurring. Using low RFA or VRFA didn't cause significant differences of signal intensity between high-frequency region and low-frequency region in k-space of 3D-DIR MRI. Therefore, it is recommended to set lower RFA (under 60° or VRFA) for suppressing blur in 3D-DIR MRI.

[Estimate of the Approximation Function of Spectral Hounsfield Unit Curves in Dual Energy CT Imaging].

The purpose of this study was to reveal the optimal function for regression of spectral Hounsfield Unit (HU) curves. The optimization procedure consists of the following steps: 1) obtaining dual energy CT (DECT) images of the RMI 467 phantom, 2) obtaining virtual monochromatic images from DECT images, 3) mapping each region of interest (ROI) to a phantom rod on virtual monochromatic images, 4) obtaining spectral HU curves for all rods, 5) regression of spectral HU curves using various functions, including linear, quadratic polynomial, cubic polynomial, quartic polynomial, quintic polynomial, sextic polynomial, septic polynomial, exponential, corrected exponential, bi-exponential, and logarithm, and 6) calculating the coefficients and the Akaike Information Criterion (AIC) of the functions listed above. Results indicated that the quintic polynomial function is suitable for analyzing the regression of spectral HU curves. The coefficients generated by the quartic or higher order polynomial functions were significantly higher than those generated by other functions (p<0.05). The median AIC of the quintic polynomial was the lowest among all functions. Therefore, we conclude that the quintic polynomial is the best function to use for the regression of spectral HU curves.

Aldehyde dehydrogenase 2 (ALDH2) and alcohol dehydrogenase 1B (ADH1B) polymorphisms exacerbate bladder cancer risk associated with alcohol drinking: gene-environment interaction.

Although a range of chemical exposures (cigarette smoking and occupational exposure) are recognized risk factors for the development of bladder cancer (BCa), many epidemiological studies have demonstrated that alcohol drinking is not associated with BCa risk. Aldehyde dehydrogenase 2 (ALDH2; rs671, Glu504Lys) and alcohol dehydrogenase 1B (ADH1B; rs1229984, His47Arg) polymorphisms impact the accumulation of acetaldehyde, resulting in an increased risk of various cancers. To date, however, no studies evaluating the association between BCa risk and alcohol drinking have considered these polymorphisms. Here, we conducted a matched case-control study to investigate whether ALDH2 and ADH1B polymorphisms influence BCa risk associated with alcohol drinking. Cases were 74 BCa patients and controls were 740 first-visit outpatients without cancer at Aichi Cancer Center Hospital between January 2001 and December 2005. Odds ratio (OR), 95% confidence interval (CI) and gene-environment interaction were assessed by conditional logistic regression analysis with adjustment for potential confounders. Results showed that ALDH2 Glu/Lys was associated with a significantly increased risk of BCa compared with Glu/Glu (OR 2.03, 95% CI 1.14-3.62, P = 0.017). In contrast, ALDH2 Glu/Lys showed no increase in risk among the stratum of never drinkers compared with Glu/Glu, indicating a gene-environment interaction. ADH1B His/Arg had an OR of 1.98 (1.20-3.24, P = 0.007) compared with His/His. ADH1B Arg+ showed a similar OR and 95% CI. Individuals with ALDH2 Glu/Lys and ADH1B Arg+ had the highest risk of BCa compared with ALDH2 Glu/Glu and ADH1B His/His [OR 4.00 (1.81-8.87), P = 0.001].

Impact of ribavirin dosage in chronic hepatitis C patients treated with simeprevir, pegylated interferon plus ribavirin combination therapy.

The factors associated with sustained virologic response (SVR) in chronic hepatitis C (CH-C) genotype 1 patients treated with simeprevir (SMV), pegylated interferon (Peg-IFN) plus ribavirin (RBV) triple therapy have not been fully investigated. Two hundred and twenty-nine treatment-naïve CH-C patients treated with SMV triple therapy were enrolled in this study. The overall SVR rate was 87% in per-protocol analysis. In multivariate analysis, the interleukin (IL) 28B genotype (rs8099917, TT vs. non-TT, odds ratio [OR]: 0.044, P = 0.001) and RBV dose (< 10/10-12/ ≥ 12 mg/kg/day, OR: 4.513, P = 0.041) were significant factors associated with SVR. In patients with the IL28B non-TT genotype, RBV dose affected SVR dose-dependently in stratified analysis of RBV dose (P = 0.015); it was 44% (8/18) for patients administered <10 mg/kg/day of RBV, 78% (14/18) for those administered 10-12 mg/kg/day of RBV, and 100% (3/3) for those administered ≥12 mg/kg/day of RBV, whereas in patients with the IL28B TT genotype, a significant correlation between SVR and RBV dose was not observed (P = 0.229). Regarding RBV dose reduction of less than 10 mg/kg/day, the inosine triphosphate pyrophosphatase (ITPA) genotype (rs1127354, CC vs. non-CC, OR: 0.239, P = 0.003) and age (by 1 y.o., OR: 1.084, P = 0.002) were significant independent factors. RBV dosage affected SVR dose-dependently in patients with the IL28B non-TT genotype treated with SMV triple therapy. Special attention to anemia progression and RBV dosage should be paid to aged patients with the ITPA CC genotype. J. Med. Virol. 88:1776-1784, 2016. © 2016 Wiley Periodicals, Inc.

Optimal b Values for Generation of Computed High-b-Value DW Images.

OBJECTIVE: The purpose of this study was to investigate the optimal b values required for the generation of computed high-b-value DW images. SUBJECTS AND METHODS: Brain DWI was performed for eight subjects using 16 b values, ranging from 0 s/mm(2) to 5000 s/mm(2). The fractional value as the turning point between the fast and slow components was determined using a diffusion decay curve. Image contrast in the white matter, gray matter, thalamus, putamen, and lateral ventricle was compared between the acquired high-b-value images and the computed high-b-value images derived from various b value images. In addition, the signal-to-noise ratio of each computed image and acquired image was measured and compared. RESULTS: The fractional values obtained from the diffusion decay curve were between 1200 and 1800 s/mm(2). Image contrast in all regions was nearly equivalent between the acquired and computed high-b-value images when b values higher than the fractional value were used, whereas image contrast was significantly different between the two sets of images when b values lower than the fractional value were used (p < 0.05). The computed images derived from low-b-value images showed a higher signal-to-noise ratio, compared with the acquired images. CONCLUSION: Optimal b values should be considered when acquiring images for the derivation of computed DW images.

Impact of branched-chain amino acid supplementation on survival in patients with advanced hepatocellular carcinoma treated with sorafenib: A multicenter retrospective cohort study.

AIM: The therapeutic efficacy of branched-chain amino acid (BCAA) when added to sorafenib has not been fully assessed in patients with advanced hepatocellular carcinoma (HCC). This multicenter study investigated whether BCAA supplementation improves prognosis in patients with advanced HCC who underwent sorafenib treatment. METHODS: This retrospective analysis included 256 patients with advanced HCC treated with sorafenib, including 55 who did and 201 who did not receive BCAA supplementation. Clinical characteristics and outcomes in relation to Child-Pugh classification were compared in the two groups. Statistical analyses of univariate, multivariate and propensity score-based procedures were used for this study. RESULTS: Assessment of 216 Child-Pugh A patients showed that median overall survival was significantly longer in patients with BCAA supplementation than in those without it (440 vs 299 days, P = 0.023). Multivariate analysis showed that BCAA supplementation (P = 0.023), low α-fetoprotein (<100 ng/mL) (P < 0.001), less progressive Barcelona Clinic Liver Cancer stage (A and B) (P = 0.007) and male sex (P = 0.018) were significant independent contributors to better overall survival. The significantly longer overall survival by BCAA supplementation was verified in the analysis using the propensity score in combination with the inverse probability of treatment weighted adjustment (P = 0.026). Assessment of the 40 Child-Pugh B patients showed no significant differences in overall survival between patients with and without BCAA supplementation. CONCLUSION: BCAA supplementation may be a valuable adjunctive therapy for improving prognosis in sorafenib-treated Child-Pugh A patients with advanced HCC.

[Development of Digital Subtraction Angiography Method for Pediatric Cardiac Angiography Using Subtraction Technique with Heart Rate].

Digital subtraction angiography (DSA) has been used in head and abdomen. However, in recent years, the use of cardiac DSA has been reported. In this report, we discuss the development of a DSA method with heart rate to clearly visualize blood vessels of pediatric patients. The patients included five children who underwent pulmonary artery angioplasty. We used a process to resize the original images and performed two kinds of subtraction methods as well as visually evaluated the images and performed comparisons between pairs of images using the Scheffe's method. Subtraction techniques were used to eliminate motion artifacts of the heart, thoracic vertebra, ribs, and diaphragm. Visualization of the image of blood vessels of pulmonary arteries using the subtraction technique with heart rate was superior to the visualization of the conventional DSA images of peripheral blood vessels of the lung and pulmonary arteries. Use of subtraction technique with heart rate makes it possible to obtain more detailed information on pediatric cardiac angiography images noninvasively.

MTF Measurement of MR Blurring in Liver Dynamic MRI with Gd-EOB-DTPA.

During the arterial phase acquisition of Gd-EOB-DTPA examinations, use of a small volume of the Gd-EOB-DTPA may make it difficult the encoding center of the k-space, and produce blurring. The previous studies revealed the encoding technique of the k-space was one of the most important reasons. However, there is no report to discuss the reasons with quantitative evaluations. The purpose of this study was to quantitatively evaluate the characteristics of the artifacts using different k-space encoding techniques (centric-view ordering (CVO) and sequential-view ordering (SVO)) for liver dynamic MRI in computer simulation study. This simulation study consists of the following steps. First of all, the creation of a time intensity curve, and original simulation images at certain points among the one phase dynamic scanning. Secondly, creation-simulated MR echo data from the created original images using FFT, and encoding simulated k-space using the simulated MR echo data. Finally, a reconstruction of simulated dynamic MR images from the simulated k-space, and to evaluate each simulated MR images, we measured modulation transfer functions (MTFs) from the bar patterns of the reconstructed images. The results of the CVO simulation indicated that the bar patterns were blurring compared to the images encoded by the SVO. The results of the SVO simulation indicated that the bar patterns were not enhanced at late scan timings. In addition, the results of MTFs indicated that there was no edge enhancement at all scan timings and both encoding techniques. In conclusion, it is possible to quantitatively evaluate the characteristics of artifacts using MTF, which was measured by the bar patterns, in liver dynamic MRI.

The Safety of MR Conditional Cochlear Implant at 1.5 Tesla Magnetic Resonance Imaging System.

In magnetic resonance imaging (MRI) examination of the patients with the cochlear implant, only limited data have a mention for safety information in the instruction manual supplied by the manufacturers. Therefore, imaging operators require more detailed safety information for implant device. We conducted detailed examination about displacement force, torque, and demagnetizing of the cochlear implant magnet based on American Society for Testing and Materials (ASTM) standard using the PULSAR and CONCERTO (MED-EL) with 1.5 tesla MRI system. As a result, the displacement force and the torque of the implant magnet were less than the numerical values descried in the manual. Therefore, these have almost no effect on the body under the condition described in a manual. In addition, the demagnetizing factor of the cochlear implant magnet occurred by a change magnetic field. The demagnetization depended on the direction of a line of magnetic force of the static magnetic field and the implant magnet. In conclusion, the operator must warn the position of the patients on inducing in the magnet room.