[The Effect of Scan Parameters on the Synthetic MRI].

Synthetic MRI can provide proton density (PD), T1 value, T2 value for each pixel by only one data acquisition and can create various contrast-weighted images. The aim of this study is to evaluate the effect on the calculation of the T1·T2 value when changing the scan parameters for synthetic MRI. In the phantom study, when changing 1st TE/2nd TE/TR/TSE factor, the effect on the T1·T2 value calculated by synthetic MRI was examined. In the volunteer study, the brain was imaged and compared with known T1·T2 value. In phantom study, the effect on the T2 value by the 1st TE/2nd TE/TSE factor was shown. In volunteer study, there was no problem in the calculated value of brain parenchyma. However, the T2 value of cerebrospinal fluid had the error of known value. The results show that it is necessary to set appropriate scan parameters on synthetic MRI.

Turbo spin-echo-based enhanced acceleration-selective arterial spin labeling without electrocardiography or peripheral pulse unit triggering and contrast enhancement for lower extremity MRA.

PURPOSE: Lower extremity magnetic resonance angiography (MRA) without electrocardiography (ECG) or peripheral pulse unit (PPU) triggering and contrast enhancement is beneficial for diagnosing peripheral arterial disease (PAD) while avoiding synchronization failure and nephrogenic systemic fibrosis. This study aimed to compare the diagnostic performance of turbo spin-echo-based enhanced acceleration-selective arterial spin labeling (eAccASL) (TSE-Acc) of the lower extremities with that of turbo field-echo-based eAccASL (TFE-Acc) and triggered angiography non-contrast enhanced (TRANCE). METHODS: Nine healthy volunteers and a patient with PAD were examined on a 3.0 Tesla magnetic resonance imaging (MRI) system. The artery-to-muscle signal intensity ratio (SIR) and contrast-to-noise ratio (CNR) were calculated. The arterial visibility (1: poor, 4: excellent) and artifact contamination (1: severe, 4: no) were independently assessed by two radiologists. Phase-contrast MRI and digital subtraction angiography were referenced in a patient with PAD. Friedman's test and a post-hoc test according to the Bonferroni-adjusted Wilcoxon signed-rank test were used for the SIR, CNR, and visual assessment. p < 0.05 was considered statistically significant. RESULTS: No significant differences in nearly all the SIRs were observed among the three MRA methods. Higher CNRs were observed with TSE-Acc than those with TFE-Acc (anterior tibial artery, p = 0.014; peroneal artery, p = 0.029; and posterior tibial artery, p = 0.014) in distal arterial segments; however, no significant differences were observed upon comparison with TRANCE (all p > 0.05). The arterial visibility scores exhibited similar trends as the CNRs. The artifact contamination scores with TSE-Acc were significantly lower (but within an acceptable level) compared to those with TFE-Acc. In the patient with PAD, the sluggish peripheral arteries were better visualized using TSE-Acc than those using TFE-Acc, and the collateral and stenosis arteries were better visualized using TSE-Acc than those using TRANCE. CONCLUSION: Peripheral arterial visualization was better with TSE-Acc than that with TFE-Acc in lower extremity MRA without ECG or PPU triggering and contrast enhancement, which was comparable with TRANCE as the reference standard. Furthermore, TSE-Acc may propose satisfactory diagnostic performance for diagnosing PAD in patients with arrhythmia and chronic kidney disease.

Utility of Echo-planar Imaging with Compressed Sensitivity Encoding (EPICS) in the Evaluation of Small Breast Cancers Using Diffusion-weighted Imaging with Background Suppression (DWIBS).

PURPOSE: High b-value acquisition and diffusion-weighted imaging with background suppression (DWIBS) are desirable in high-specificity breast cancer diagnosis on non-contrast-enhanced magnetic resonance imaging; however, this inherently results in a lower signal-to-noise ratio (SNR). Compressed sensitivity encoding (C-SENSE), which combines SENSE with compressed sensing, improves the SNR by reducing noise. Recent technological improvements allow us to incorporate this acceleration technique into echo-planar imaging, called echo-planar imaging with C-SENSE (EPICS). This study aimed to compare image quality and reliability of the apparent diffusion coefficient (ADC) between DWIBS obtained using SENSE and EPICS in patients with small breast cancers. METHODS: Thirty-seven patients with pathologically confirmed breast cancer underwent DWIBS, and images were reconstructed using both conventional SENSE (SENSE-DWIBS) and EPICS (EPICS-DWIBS). Two board-certified radiologists independently evaluated lesion conspicuity (LC) and noise using a 5-point grading scale. The same 2 radiologists independently measured SNR, contrast-to-noise ratio (CNR), and the mean cancer ADC. The Pearson coefficient and Bland-Altman plot were applied to assess the accuracy of ADCs. RESULTS: LC scores were higher with EPICS than with SENSE, reaching significance for one reviewer but not the other reviewer. Noise ratings on visual evaluation were significantly lower with EPICS than with SENSE (P < 0.001 for both reviewers). SNR was significantly higher with EPICS than with SENSE (P < 0.005 for both reviewers). CNR was significantly higher with EPICS than with SENSE (P < 0.001 for both reviewers). Bland-Altman plots of cancer ADCs using EPICS-DWIBS and SENSE-DWIBS showed excellent concordance, with a bias of 0.026 × 10-3 mm2/s and limits of agreement ranging 0.054 × 10-3 mm2/s; the Pearson's correlation coefficient was 0.997 (P < 0.0001). CONCLUSION: EPICS enhances breast DWIBS image quality, with improved SNR and CNR and reduced noise levels. The ADCs of breast cancers obtained using EPICS were almost perfectly correlated with those obtained using conventional SENSE.

[Problem of spectral attenuated with inversion recovery fat suppression method with respiratory-gated].

The purpose of this study was to investigate the effect of fat suppression when we use respiratory-gated spectral attenuated with inversion recovery (SPAIR) method with respiratory-gated. We experimented on phantom and in-vivo study using simulated wave of respiratory-gated SPAIR at 1.5 tesla and 3.0 tesla. As a result, the effect of fat suppression becomes wrong with longer intervals of inspiration and expiration by wave of respiratory-gated. The signal intensity also varies with each slice. This result had the same trend on phantom and in-vivo study. The longitudinal magnetization of fat becomes a stable state when SPAIR pulse is shot more than once. However, the SPAIR method with respiratory-gated collect signal before the longitudinal magnetization of fat to be stable state, and fat suppression effect becomes bad, because the inversion time does not match the null point of the fat. Therefore, when we use SPAIR method with respiratory-gated it always causes bad fat suppression.

[Visualization of Cerebrospinal Fluid Dynamics by Respiratory Motion Using Phase Dispersion: Optimization of Spatial and Temporal Resolutions].

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.

Temperature measurement of intracranial cerebrospinal fluid using diffusion tensor imaging after revascularization surgery in Moyamoya disease.

OBJECTIVE: Brain temperature monitoring using a catheter thermometer has been reported to be a useful technique to predict prognosis in neurosurgery. To investigate the possibility of measuring intracranial cerebrospinal fluid temperature for postoperative monitoring in patients with Moyamoya disease (MMD) after bypass surgery. MATERIALS AND METHODS: This study evaluated fifteen patients with MMD who were indicated for bypass surgery. Diffusion tensor imaging for brain thermometry were performed on a 1.5-T MR scanner. Intracranial cerebrospinal fluid temperature with/without considering the fractional anisotropy component, body temperature, C-reactive protein levels, white blood cell count, and cerebral blood flow measured by 123I-IMP single-photon emission computed tomography were obtained before surgery and 1-3 days after surgery. Pixel values considered to be signal outliers in fractional anisotropy processing were defined as cerebrospinal fluid noise index and calculated. Wilcoxon signed-rank test and effect size were performed to compare the changes before and after revascularization. Spearman's rho correlation coefficient was used to analyze the correlations between each parameter. Statistical significance was defined as p < 0.05. RESULTS: All parameter values became significantly higher compared to those measured before revascularization (p < 0.01 in all cases). The effect sizes were largest for the cerebrospinal fluid temperature with fractional anisotropy processing and for C-reactive protein levels (Rank-biserial correlation = 1.0). The cerebrospinal fluid noise index and cerebrospinal fluid temperatures with fractional anisotropy processing (r = 0.84, p < 0.0001) or without fractional anisotropy processing (r = 0.95, p < 0.0001) showed highly significant positive correlations. Although no significant correlation was observed, cerebrospinal fluid temperatures with fractional anisotropy had small or moderately positive correlations with cerebral blood flow, body temperature, C-reactive protein levels, and white blood cell count (r = 0.37, 0.42, 0.41, and 0.44, respectively; p > 0.05). CONCLUSION: Our findings suggest the possibility of postoperative monitoring for MMD patients by measuring intracranial cerebrospinal fluid temperature with fractional anisotropy processing. Intracranial cerebrospinal fluid temperature might be considered as combined response since cerebrospinal fluid, body temperature, and inflammation are equally correlated.

Automatic detection of punctate white matter lesions in infants using deep learning of composite images from two cases.

Punctate white matter lesions (PWMLs) in infants may be related to neurodevelopmental outcomes based on the location or number of lesions. This study aimed to assess the automatic detectability of PWMLs in infants on deep learning using composite images created from several cases. To create the initial composite images, magnetic resonance (MR) images of two infants with the most PWMLs were used; their PWMLs were extracted and pasted onto MR images of infants without abnormality, creating many composite PWML images. Deep learning models based on a convolutional neural network, You Only Look Once v3 (YOLOv3), were constructed using the training set of 600, 1200, 2400, and 3600 composite images. As a result, a threshold of detection probability of 20% and 30% for all deep learning model sets yielded a relatively high sensitivity for automatic PWML detection (0.908-0.957). Although relatively high false-positive detections occurred with the lower threshold of detection probability, primarily, in the partial volume of the cerebral cortex (≥ 85.8%), those can be easily distinguished from the white matter lesions. Relatively highly sensitive automatic detection of PWMLs was achieved by creating composite images from two cases using deep learning.

Evaluation of Cardiac- and Respiratory-driven Cerebrospinal Fluid Motions by Applying the S-transform to Steady-state Free Precession Phase Contrast Imaging.

PURPOSE: To extract the status of hydrocephalus and other cerebrospinal fluid (CSF)-related diseases, a technique to characterize the cardiac- and respiratory-driven CSF motions separately under free breathing was developed. This technique is based on steady-state free precession phase contrast (SSFP-PC) imaging in combination with a Stockwell transform (S-transform). METHODS: 2D SSFP-PC at 3 T was applied to measure the CSF velocity in the caudal-cranial direction within a sagittal slice at the midline (N = 3) under 6-, 10-, and 16-s respiratory cycles and free breathing. The frequency-dependent window width of the S-transform was controlled by a particular scaling factor, which then converted the CSF velocity waveform into a spectrogram. Based on the frequency bands of the cardiac pulsation and respiration, as determined by the electrocardiogram (ECG) and respirator pressure sensors, Gaussian bandpass filters were applied to the CSF spectrogram to extract the time-domain cardiac- and respiratory-driven waveforms. RESULTS: The cardiac-driven CSF velocity component appeared in the spectrogram clearly under all respiratory conditions. The respiratory-driven velocity under the controlled respiratory cycles was observed as constant frequency signals, compared to a time-varying frequency signal under free breathing. When the widow width was optimized using the scale factor, the temporal change in the respiratory-driven CSF component was even more apparent under free breathing. CONCLUSION: Velocity amplitude variations and transient frequency changes of both cardiac- and respiratory-driven components were successfully characterized. These findings indicated that the proposed technique is useful for evaluating CSF motions driven by different cyclic forces.

Respiratory-driven Cyclic Cerebrospinal Fluid Motion in the Intracranial Cavity on Magnetic Resonance Imaging: Insights into the Pathophysiology of Neurofluid Dysfunction.

Neurofluids, a recently developed term that refers to interstitial fluids in the parenchyma and cerebrospinal fluid (CSF) in the ventricle and subarachnoid space, play a role in draining waste products from the brain. Neurofluids have been implicated in pathological conditions such as Alzheimer's disease and normal pressure hydrocephalus. Given that CSF moves faster in the CSF cavity than in the brain parenchyma, CSF motion can be detected by magnetic resonance imaging. CSF motion is synchronized to the heartbeat and respiratory cycle, but respiratory cycle-induced CSF motion has yet to be investigated in detail. Therefore, we analyzed CSF motion using dynamic improved motion-sensitized driven-equilibrium steady-state free precession-based analysis. We analyzed CSF motion linked to the respiratory cycle in four women and six men volunteers aged 23 to 38 years. We identified differences between free respiration and tasked respiratory cycle-associated CSF motion in the ventricles and subarachnoid space. Our results indicate that semi-quantitative analysis can be performed using the cranial site at which CSF motion is most prominent as a standard. Our findings may serve as a reference for elucidating the pathophysiology of diseases caused by abnormalities in neurofluids.

Gymkhana and pylon slalom driving training effects on the cerebellum structure.

To develop a suitable automobile design as per each driver's characteristics and state, it is important to understand the brain function in acquiring driving skills. Reportedly, the brain structures of professionals, such as athletes and musicians, and those who have received training in special skills, undergo changes with training. However, the development process of the brain in terms of acquiring driving skills has not yet been clarified. In this study, we evaluated the effects of driving training on the brain and observed an increase in the volume of the right cerebellum after short-term training (3 days). The right cerebellum is responsible for controlling the right hand and right foot, which are important for driving. Drivers train to control a vehicle smoothly at high speeds at gymkhana and pylon slalom courses, which are often used in motor sports. The brain structure was analyzed before and after training using magnetic resonance imaging. Voxel-based morphometry was used to assess possible structural changes. First, the lap times after training were clearly shortened and vehicle dynamics were more stable, indicating that the drivers' skill level clearly improved. Second, brain structural analysis revealed a volumetric increase in the right cerebellum. The cerebellum is involved in the process of learning sensory motor skills, such as smooth steering and pedal operations, driving course shape, and vehicle size perception. These results suggest a new inner model for driving operation and support the hypothesis that motor learning affects the cerebellum during vehicle driving training.

Visualization of Cerebrospinal Fluid Motion in the Whole Brain Using Three-dimensional Dynamic Improved Motion-sensitized Driven-equilibrium Steady-state Free Precession.

The feasibility of the 3D dynamic improved motion-sensitized driven-equilibrium steady-state free precession (3D dynamic iMSDE SSFP) was evaluated for visualizing CSF motion and the appropriate parameters were determined. Both flow phantom and volunteer studies revealed that linear ordering and the shortest acquisition duration time were optimal. 3D dynamic iMSDE SSFP provides good quality imaging of CSF motion in the whole brain and enables visualization of flow in arbitrary planes from a single 3D volume scan.

Characterization of Cardiac- and Respiratory-driven Cerebrospinal Fluid Motions Using a Correlation Mapping Technique Based on Asynchronous Two-dimensional Phase Contrast MR Imaging.

PURPOSE: The cardiac- and respiratory-driven components of cerebrospinal fluid (CSF) motion characteristics and bulk flow are not yet completely understood. Therefore, the present study aimed to characterize cardiac- and respiratory-driven CSF motions in the intracranial space using delay time, CSF velocity waveform correlation, and displacement. METHODS: Asynchronous two-dimensional phase-contrast at 3T was applied to measure the CSF velocity in the inferior-superior direction in a sagittal slice at the midline (N = 12) and an axial slice at the foramen magnum (N = 8). Volunteers were instructed to engage in six-second respiratory cycles. The calculated delay time and correlation coefficients of the cardiac- and respiratory-driven velocity waveforms, separated in the frequency domain, were applied to evaluate the propagation of the CSF motion. The cardiac- and respiratory-driven components of the CSF displacement and motion volume were calculated during diastole and systole, and during inhalation and exhalation, respectively. The cardiac- and respiratory-driven components of the velocity, correlation, displacement, and motion volume were compared using an independent two-sample t-test. RESULTS: The ratio of the cardiac-driven CSF velocity to the sum of the cardiac- and respiratory-driven CSF velocities was higher than the equivalent respiratory-driven ratio for all cases (P < 0.01). Delay time and correlation maps demonstrated that the cardiac-driven CSF motion propagated more extensively than the respiratory-driven CSF motion. The correlation coefficient of the cardiac-driven motion was significantly higher in the prepontine (P < 0.01), the aqueduct, and the fourth ventricle (P < 0.05). The respiratory-driven displacement and motion volume were significantly greater than the cardiac-driven equivalents for all observations (P < 0.01). CONCLUSION: The correlation mapping technique characterized the cardiac- and respiratory-driven CSF velocities and their propagation properties in the intracranial space. Based on these findings, cardiac-driven CSF velocity is greater than respiratory-induced velocity, but the respiratory-driven velocity might displace farther.

Simple Identification of Cerebrospinal Fluid Turbulent Motion Using a Dynamic Improved Motion-sensitized Driven-equilibrium Steady-state Free Precession Method Applied to Various Types of Cerebrospinal Fluid Motion Disturbance.

The motion of cerebrospinal fluid (CSF) within the subarachnoid space and ventricles is greatly modulated when propagating synchronously with the cardiac pulse and respiratory cycle and path through the nerves, blood vessels, and arachnoid trabeculae. Water molecule movement that propagates between two spaces via a stoma, foramen, or duct presents increased acceleration when passing through a narrow area and can exhibit "turbulence." Recently, neurosurgeons have started to perform fenestration procedures using neuroendoscopy to treat hydrocephalus and cystic lesions. As part of the postoperative evaluation, a noninvasive diagnostic technique to visualize the water molecules at the fenestrated site is necessary. Because turbulence is observed at this fenestrated site, an imaging technique appropriate for observing this turbulence is essential. We therefore investigated the usefulness of a dynamic improved motion-sensitized driven-equilibrium steady-state free precession (Dynamic iMSDE SSFP) sequence of magnetic resonance imaging that is superior for ascertaining turbulent motions in healthy volunteers and patients. Images of Dynamic iMSDE SSFP from volunteers revealed that CSF motion at the ventral surface of the brainstem and the third ventricle is augmented and turbulent. Moreover, our findings confirmed that this technique is useful for evaluating treatments that utilize neuroendoscopy. As a result, Dynamic iMSDE SSFP, a simple sequence for visualizing CSF motion, entails a short imaging time, can extensively visualize CSF motion, does not require additional processes such as labeling or trigger setting, and is anticipated to have wide-ranging clinical applications in the future.

A Combination of Magnetic Resonance Imaging Techniques to Localize the Dural Defect in a Case of Superficial Siderosis-A Case Report.

Background: Superficial siderosis is a progressively disabling disease caused by recurrent subarachnoid hemorrhage with accumulation of hemosiderin in the surface of the central nervous system. Although a wide variety of conditions may cause superficial siderosis, approximately half of the cases are reported to be associated with a defect in the ventral spinal dura mater, in which case treatment entails surgical repair of the defect. Here, we report a case of superficial siderosis and report on our method to pinpoint the dural defect using a combination of magnetic resonance imaging (MRI) techniques. Methods and Results: A 74-year-old female presented suffering from hearing loss and progressive ataxia over a duration of seven years. A T2-weighted MRI study revealed hypointensity in the superficial areas of the central nervous system, leading to the diagnosis of superficial siderosis, and the presence of a fluid-filled collection in the anterior spinal canal of C7 to T10 suggested that a dural defect was the cause of the repeated hemorrhage. A balanced turbo field echo (BTFE) MRI sequence revealed possible dural defects at T1-T2 and T5-T6, and a dynamic improved motion-sensitized driven-equilibrium steady-state free precession (dynamic iMSDE SSFP) sequence revealed an irregular flow of cerebrospinal fluid through the dura at the T5-T6 level. The dural defect was confirmed and sutured through a minimal T5-T6 laminectomy without neurological consequences, and the patient reported mild improvement in gait one year after surgery. Conclusions: A combination of MRI sequences provided the necessary information to confidently perform minimal surgery to repair the dural defect. We recommend coupling a balanced steady-state free precession (SSFP) sequence to provide high resolution, high contrast images of anatomical structures and a dynamic iMSDE SSFP sequence to confirm cerebrospinal fluid motion through the defect.

Diagnostic performance of diffusion-weighted magnetic resonance imaging in esophageal cancer.

The purpose of this study was to assess the value of diffusion-weighted magnetic resonance imaging (DWI) in detecting esophageal cancer and assessing lymph-node status, compared with histopathological results. DWI was prospectively performed in 24 consecutive patients with esophageal cancer, using the diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) sequence. DWIBS images were fused with T2-weighted images, and independently and blindly evaluated by three board-certified radiologists, regarding primary tumor detectability and lymph-node status. Apparent diffusion coefficients (ADCs) of the primary tumor and lymph nodes were also measured. Average primary tumor detection rate was 49.4%, average patient-based sensitivity and specificity for the detection of lymph-node metastasis were 77.8 and 55.6%, and average lymph-node group-based sensitivity and specificity were 39.4 and 92.6%. There were no interobserver differences among the three readers (P < 0.0001). Mean ADC of detected primary tumors was 1.26 +/- 0.29x10(-3) mm(2)/s. Mean ADC of metastatic lymph nodes (1.46 +/- 0.35x10(-3) mm(2)/s) was significantly higher (P < 0.0001) than that of nonmetastatic lymph nodes (1.15 +/- 0.24 mm(2)/s), but ADCs of both groups overlapped. In conclusion, this study suggests that DWI only has a limited role in detecting esophageal cancer and nodal staging.

[Study of aliasing ERROR with SENSE in body diffusion image using single-shot EPI at 3T].

Magnetic field inhomogeneity causes artifacts in MRI. For example, in single-shot echo-planar imaging (EPI), they often appear as severe geometric distortions along the phase-encoding direction. Sensitivity encoding (SENSE) is useful in reducing the distortion in EPI since it only acquires partial k-space data using multiple receiver channels. In SENSE, a reference scan usually needs to be performed to create a sensitivity profile of each receiver channel. Gradient echo (GRE) sequences are often used in the reference scan. In diffusion-weighted imaging (DWI) using single-shot EPI with SENSE, non-negligible aliasing artifacts often remain in the reconstructed images. We suppose that these artifacts result from misregistration between the reference images acquired using GRE sequences and the DWI acquired using EPI. In this study, we used two types of acquisition methods to create sensitivity profiles, GRE sequences and EPI, and have compared the residual artifacts in the reconstructed images. The sensitivity profiles were created from the data acquired using the GRE and EPI sequences. Artifacts were reduced when EPI sensitivity profiles were used. This resulted from the fact that off-resonance effects, e.g., magnetic field inhomogeneity, susceptibility, and chemical shift, often cause severe image distortion in EPI, and, therefore, there is misregistration between images reconstructed from the data acquired using GRE and EPI sequences. Our study suggests that EPI sensitivity profiles be used when imaging data are acquired using a single-shot EPI with SENSE, although GRE sensitivity profiles have often been used in practice.

[Basic examination of CEMRA with 4D time-resolved angiography using keyhole (4D-TRAK) in 3T pelvic region].

Time-resolved MRA has recently been reported, and high-resolution MRA that does not miss timing is possible. In this examination, CEMRA that used 4D time-resolved angiography using keyhole (4D-TRAK) at 3T for the pelvic region was studied. 4D-TRAK is a method of using keyhole imaging together with sensitivity encoding (SENSE) and contrast-enhanced timing robust angio (CENTRA). The method changed flip angle (FA) and examined relative signal intensity, TR, TE, dynamic keyhole scan duration (DKSD) of the dilution contrast media, and keyhole% (KP). Image quality was examined with a blood vessel phantom. The presence of the partial echo method (PE) was examined in all cases. Relative signal intensity rose when FA increased. It has decreased in the PE method. TR did not show a difference by the PE method in FA15 degrees or more. DKSD was extended by the PE method. In the blood vessel Phantom, the PE method made the ringing artifacts remarkable. The artifacts that originated in keyhole imaging were observed. Shortening TR is difficult because of peculiar SAR to 3T. The PE method is not effective and becomes useless. It is necessary to note a point different from the parameter setting by 1.5T.

[Trial of artifact reduction in body diffusion weighted imaging development and basic examination of "TRacking Only Navigator"(TRON method)].

In recent years, the utility of body diffusion weighted imaging as represented by diffusion weighted whole body imaging with background body signal suppression (DWIBS), the DWIBS method, is very high. However, there was a problem in the DWIBS method involving the artifact corresponding to the distance of the diaphragm. To provide a solution, the respiratory trigger (RT) method and the navigator echo method were used together. A problem was that scan time extended to the compensation and did not predict the extension rate, although both artifacts were reduced. If we used only navigator real time slice tracking (NRST) from the findings obtained by the DWIBS method, we presumed the artifacts would be ameliorable without the extension of scan time. Thus, the TRacking Only Navigator (TRON) method was developed, and a basic examination was carried out for the liver. An important feature of the TRON method is the lack of the navigator gating window (NGW) and addition of the method of linear interpolation prior to NRST. The method required the passing speed and the distance from the volunteer's diaphragm. The estimated error from the 2D-selective RF pulse (2DSRP) of the TRON method to slice excitation was calculated. The condition of 2D SRP, which did not influence the accuracy of NRST, was required by the movement phantom. The volunteer was scanned, and the evaluation and actual scan time of the image quality were compared with the RT and DWIBS methods. Diaphragm displacement speed and the quantity of displacement were determined in the head and foot directions, and the result was 9 mm/sec, and 15 mm. The estimated error was within 2.5 mm in b-factor 1000 sec/mm(2). The FA of 2DSRP was 15 degrees, and the navigator echo length was 120 mm, which was excellent. In the TRON method, the accuracy of NRST was steady because of line interpolation. The TRON method obtained image quality equal to that of the RT method with the b-factor in the volunteer scanning at short actual scan time. The TRON method can obtain image quality equal to that of the RT method in body diffusion weighted imaging within a short time. Moreover, because scan time during planning becomes actual scan time, inspection can be efficiently executed.

Time-spatial Labeling Inversion Pulse (Time-SLIP) with Pencil Beam Pulse: A Selective Labeling Technique for Observing Cerebrospinal Fluid Flow Dynamics.

We assessed labeling region selectivity on time-spatial labeling inversion pulse (Time-SLIP) with pencil beam pulse (PB Time-SLIP) for the use of visualizing cerebrospinal fluid (CSF) flow dynamics. We compared the selectivity of labeling to the third and fourth ventricles between PB Time-SLIP and conventional Time-SLIP (cTime-SLIP) in eight volunteers and one patient using a 1.5T MRI. PB Time-SLIP provided more selective labeling in CSF than cTime-SLIP, particularly in complex anatomical regions.