Evaluation of capillary blood volume in the lower limb muscles after exercise by intravoxel incoherent motion.

PURPOSE: The purpose of this study was to evaluate the change in capillary blood volume in the muscles of the lower limbs, before and after exercise, using intravoxel incoherent motion (IVIM). MATERIALS AND METHODS: Diffusion-weighted images were obtained (with 16 b values) from the thigh and leg muscles of 11 subjects. The imaging was obtained before and immediately exercise; additionally, imaging was performed at 3 h, 6 h, and 24 h after exercise, and an IVIM index was calculated. The exercise involved walking up and down a flight of stairs (140 steps) ten times. The IVIM of each time course-before and after the exercise-was compared. In addition, we examined the correlation of IVIM measurements with the degree of the muscle ache that occurred at 24 h following the exercise. RESULTS: The IVIM index significantly increased after exercise compared with that before exercise (P < 0.01). IVIM decreased at 3 h following exercise, but increased again at 24 h. A correlation was found between the IVIM index at 24 h after exercise and the degree of the muscle ache (r = 0.80) CONCLUSIONS: The capillary blood volume significantly increased after exercise when compared to before exercise. The capillary blood volume decreased after exercise at 3 h and 6 h following exercise, but it increased again at 24 h. There was a correlation between the degree of muscle ache and the amount of capillary blood volume measured from the femoral muscle at 24 h after exercise.

[Setting Method of the Optimal Slab of Brain MRA for Detective Unruptured Cerebral Aneurysm].

Generally, the imaging range of the brain magnetic resonance angiography (MRA) is determined in the subjectivity by the operator used by the plan image that a blood vessel is not depicted. However, a necessary blood vessel may not be often depicted by an error of the setting of the imaging area. Therefore, optimal slab angle, thickness, distance, and image contrast for depiction of the unruptured cerebral aneurysm were examined. The brain MRA of 14 subjects was imaged in a wide area parallel to an orbitomeatal line (OM) line. The line which linked the arteria vertebral (the first cervical vertebrae curved section) to anterior cerebral artery (A3) was determined with an optimal slab base line, and the angle with the OM line was evaluated. Moreover, slavic range including the unruptured aneurysm was calculated. In addition, the distance from the inferior margin of pons to the slavic bottom end was measured. Furthermore, the cerebrovascular contrast by the slave angle was compared. As a result, the slave setting of the range was recommended in brain-MRA as an angle was 34.3 degrees, and the thickness was 56.4 mm, and, as the distance from the inferior margin of pons was 27.6 mm. The cerebrovascular contrast of the optimal slab base line angle did not have a significant difference for an OM line.

[Verification of "IEC 62464-12007": The Evaluation Method of Spatial Resolution in MRI].

Recently, many methods are suggested to evaluate spatial resolution in MRI. However, those techniques are not simple and easy. The International Electrotechnical Commission (IEC) recommends a method to evaluate spatial resolution using a periodic pattern image as IEC 62464-1. IEC 62464-1 prescribes specifications and placement of phantom, and a method of analysis, but these details grounds are not clear. A purpose of this study is to examine the effect in each factor of IEC 62464-1 method and define the characteristics of this method. Nine phantoms with different plate thickness were made including prescribed specifications of IEC 62464-1. Imaging was conducted with changing the placement angle of these phantoms. Also, analysis was carried out in region of interest (ROI) of three different size. As a result, the placement angle of the phantom, measurement error was <1% on a condition prescribed by a method of IEC 62464-1. There was not the effect if the transverse diameter for the longitudinal diameter exceeded 100% fort the size of ROI. In specifications of the phantom, there was not the dependence for the thickness of the plate of the phantom in IEC 62464-1 prescribes.

[Improvement of Fat Suppressing Effect for Finger and Neck MRI by Using Small Glass Beads].

The defectiveness of the fat suppression becomes the factor of the decrease of the quality of the diagnosis of magnetic resonance imaging. It is reported that the use of magnetic field uniformity adjuvant pad is effective for reduce poor fat suppression. The ball bullets, polystyrene balls, and polished rice are used for pad packing material, in recently, it was reported that fat suppression effect was good by the use of the small glass beads. Therefore, we tested the utility of small glass beads pad in the neck and fingers in this study. Neck and the fingers of subjects were imaged with T1-weighted image with fat suppression and T1-high resolution isotropic volume excitation image. The fat suppression effect of each image was compared with the polished rice and glass beads as material of pad used by physical, observation, and contact evaluation. In the result, satisfactory results were obtained by using glass beads, and it is suggested that fat suppression effect is improved by using glass beads as a filling material of pad in clinical study as a conclusion.

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.

[Comparison of Organ Dose Calculation Using Monte Carlo Simulation and In-phantom Dosimetry in CT Examination].

Direct measurement of each patient organ dose from computed tomography (CT) is not possible. Most methods to estimate patient organ dose is using Monte Carlo simulation with dedicated software. However, the method and the relative differences between organ dose simulation and measurement is unclear. The purpose of this study was to compare organ doses evaluated by Monte Carlo simulation with doses evaluated by in-phantom dosimetry. The simulation software Radimetrics (Bayer) was used for the calculation of organ dose. Measurement was performed with radio-photoluminescence glass dosimeter (RPLD) set at various organ positions within RANDO phantom. To evaluate difference of CT scanner, two different CT scanners were used in this study. Angular dependence of RPLD and measurement of effective energy were performed for each scanner. The comparison of simulation and measurement was evaluated by relative differences. In the results, angular dependence of RPLD at two scanners was 31.6±0.45 mGy for SOMATOM Definition Flash and 29.2±0.18 mGy for LightSpeed VCT. The organ dose was 42.2 mGy (range, 29.9-52.7 mGy) by measurements and 37.7 mGy (range, 27.9-48.1 mGy) by simulations. The relative differences of organ dose between measurement and simulation were 13%, excluding of breast's 42%. We found that organ dose by simulation was lower than by measurement. In conclusion, the results of relative differences will be useful for evaluating organ doses for individual patients by simulation software Radimetrics.

[Evaluation of Organ Dose Estimation from Indices of CT Dose Using Dose Index Registry].

Direct measurement of each patient organ dose from computed tomography (CT) is not possible. Most methods to estimate patient organ dose is using Monte Carlo simulation with dedicated software. However, dedicated software is too expensive for small scale hospitals. Not every hospital can estimate organ dose with dedicated software. The purpose of this study was to evaluate the simple method of organ dose estimation using some common indices of CT dose. The Monte Carlo simulation software Radimetrics (Bayer) was used for calculating organ dose and analysis relationship between indices of CT dose and organ dose. Multidetector CT scanners were compared with those from two manufactures (LightSpeed VCT, GE Healthcare; SOMATOM Definition Flash, Siemens Healthcare). Using stored patient data from Radimetrics, the relationships between indices of CT dose and organ dose were indicated as each formula for estimating organ dose. The accuracy of estimation method of organ dose was compared with the results of Monte Carlo simulation using the Bland-Altman plots. In the results, SSDE was the feasible index for estimation organ dose in almost organs because it reflected each patient size. The differences of organ dose between estimation and simulation were within 23%. In conclusion, our estimation method of organ dose using indices of CT dose is convenient for clinical with accuracy.

[Capillary Blood Flow of Muscle Before and After the Exercise Used by Intravoxel Incoherent Motion].

Capillaries are the most basic and important blood vessel of the circulatory systems. The evaluation of the blood flow may contribute to many studies in future. We evaluated the capillary blood flow change of lower limb muscle over time before and after the exercise used by magnetic resonance imaging-intravoxel incoherent motion (MRI-IVIM) obtained perfusion information. Furthermore, we examined an association between the muscle pain after the exercise and the diffusion weighted image (DWI) indexes. DWI was imaged using multi-b values for a thigh and calf muscles. MRI was performed just after an exercise test, 3, 6, and 24 hours later, and the IVIM index and diffusion index were calculated. Furthermore, we interviewed the degree of the muscle ache 24 hours later. As a result, pseudo diffusion coefficient (D*) and f value as IVIM index increased after-exercise as compared with pre-exercise and decreased in 3 hours later. A similar tendency was found in the apparent diffusion coefficient and the diffusion coefficient as diffusion index. Furthermore, all indexes increased in after exercise from before exercise and decreased with time passed and increased again 24 hours later. In conclusion, IVIM could obtain capillary blood flow information, and it was suggested to contribute for sports medicine in future.

[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.

[Effect of Slice Thickness for Apparent Diffusion Coefficient Measurement of Mass].

Apparent diffusion coefficient (ADC) values calculated from diffusion-weighted magnetic resonance imaging (DW-MRI) can be used for differentiation of tumors. Clinically, ADC values are used for monitoring treatment response after chemotherapy or radiation. However, it is reported that the threshold of the ADC value differs among institutions. In addition, there are reports regarding the change factor of the ADC value. Slice thickness may induce error in the ADC value by the influence of the partial volume effect in thicker objects, and by the influence of signal-to-noise ratio (SNR) in thinner objects. Therefore, in this study, the effect of slice thickness was examined. The signal body of spherical high-diffusion coefficients of 6, 7.9, and 9.3 mm in diameter was fixed in the low-circumference material of the diffusion coefficient. These phantoms were imaged using DW imaging (DWI) of 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 15, and 20 mm slice thickness using the multi-b values. In addition, different SNR were imaged by changing field-of-view and the number of additions. ADC was calculated by DWI of the different b values. As a result, slice thickness showed a peak at 50-65% of the diameter of the signal body. Furthermore, ADC values fluctuated in the slice thickness in front of the peak with a change in SNR. In conclusion, the ADC value was most accurate at a setting of 50-65% of slice thickness for the object diameter.

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.

The Optimal Pad Material for Fat Suppression of Breast MRI.

Although fat suppression technique is used in breast MRI, artifacts often appear owing to susceptibility and defective fat suppression effect after breast surgery. This is due to the abundance of adipose tissue in the breast as well as the region of air around the circumference of the excision site. Therefore, we have evaluated the optimal pad material for achieving fat suppression in breast MRI to reduce image artifacts and patient discomfort while maintaining breast shape. Oil of the solidity was used as the breast phantom material after segmental resection surgery. Five pad materials, including rice, ball bullets, glass beads, acrylic beads, and bath salts were used to fill the defects. Fat-suppressed, T1-weighted, three-dimensional imaging was performed using a breast array coil. Images with and without the five pad materials, were evaluated physically, visually, and by contact. Physical evaluation consisted of measuring the maximum signal and standard deviation in the regions of interest (ROIs). Discomfort and the amount of perceived resistance were evaluated during contact evaluation by inserting a finger into each pad material. In results, glass beads and bath salts produced a significantly larger fat suppression effect in the ROIs. Visual and contact evaluation also highlighted the benefits of glass beads, the latter demonstrating a significant decrease in discomfort and perceived resistance. In conclusion, we consider glass beads as the optimal pad material for fat suppression in breast MRI after surgery.

[Factors for Degaussing of a Cochlear Implant Magnet in the MR Scanner].

This study examined the conditions influencing degauss of the magnet using magnetic resonance imaging (MRI). Poly methyl methacrylate (PMMA) was used to fix the measurement magnets to the MRI bed at angles from 0° to 180° for the magnetic flux vector of static magnetic field. The PMMA was moved in the MRI magnetic field. Magnetic flux density was measured before and after bed movement, and the rate of degauss was calculated. The contents examined are as follows: (1) the angle of the magnetic flux vector of the measurement magnets for the magnetic flux vector of the static magnetic field, (2) the number of movements, (3) moving velocity, and (4) the movement on the spatial gradient of magnetic field. Mann-Whitney U test was used for statistical analysis of the data. In conclusion, the effect of the angle of the magnetic flux vector of the implant magnet was high under the conditions of degauss in this study. Therefore, during the MRI examination of a patient with a cochlear implant magnet, the operators identified the directions of the magnetic flux vector and static magnetic field of the implant magnet.

Survey of Careers and Achievements on Delegates in JSRT International Delegation Projects.

Japanese society of radiological technology (JSRT) categorizes three international delegation projects; short-term studying abroad program (STSAP), international academic society visit program (overseas) (IASVP), and international internship visit program (Stanford University) (IIVP) for driving globalization of JSRT. In this survey, we conducted a questionnaire evaluating effectiveness of the international delegations. The survey covered 50 delegates of STSAP, 180 delegates of IASVP, and 100 delegates of IIVP. This survey includes detailed histories of career, current position, academic articles, and presentations as a first presenter before and on, and after each program. We categorized into six groups (change career, promoted in a position in hospital, kept a current position in hospital, promoted in a position in university, kept a current position in university, and others) in three programs. The response rate is approximately 58% (191/330 delegators). In all programs, almost all the delegates were radiological technologists in the hospital. They had reported a lot of academic articles and made a lot of presentations, and promoted in the hospital and/or university. STSAP, IASVP and IIVP were descending order of the average number of the articles as a first author and presentations as a first presenter. They published more the academic articles in Japanese than in English compared to JJRT and RPT. Therefore, research achievements and human resource conducted by this project provide great technologists and technique, and education. For further JRST globalization, it is desirable that we can continue these international delegations and verify the effectiveness.

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.

Importance of Fractional b Value for Calculating Apparent Diffusion Coefficient in DWI.

OBJECTIVE: The purpose of this study is to examine how the fractional b value affects the calculation of apparent diffusion coefficient (ADC) using DWI. The fractional b value is the point of intersection between the fast and slow components of biexponential decay in DWI. SUBJECTS AND METHODS: Human brains were imaged using multiple b values on echo-planar DWI. The ADCs of white matter, gray matter, and thalamus were calculated using the combination of b values by two-point and multipoint methods, and the characteristics of each ADC value were compared. RESULTS: When the two selected points for calculation were smaller than the fractional b value (b = 1700 s/mm2), the ADC value was 0.0007-0.0008 mm2/s, but when the two points used for calculation were greater than the fractional b value, the ADC value was 0.0003-0.0004 mm2/s. When a range of b values was included in the fast and slow components by use of the multipoint method, the ADC value showed a statistically significant increase as the number of multiple b values increased. CONCLUSION: The ADC value fluctuated when the b values used for calculation were higher than the fractional b value. Therefore, it is important to determine the fractional b value of the target tissue.

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.

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.