To establish an optimized sequence design for fast acceleration of arterial spin labeling (ASL)-based time-resolved magnetic resonance angiography (MRA) by acquisition of control and labeled images ...in the same shot (fast ACTRESS) and a scan time of <1min, for the evaluation of intracranial vessels.
Ten healthy volunteers with no unilateral symptomatic arterial stenosis, who underwent 3-tesla MRI, were investigated. Imaging parameters for the fast ACTRESS sequence were set with an acquisition time of 45s. During post-processing, the first phase in the multi-phase readout, which was defined as the control image, was subtracted from each of the other phases. Thus, four-dimensional (4D)-MRA images of each phase were obtained. The maximum intensity projection was used for the reconstruction of 4D-MRA images and time-to-signal intensity curves (TIC) obtained for each vessel. The area under the curve (AUC), peak time, and maximum signal intensity were obtained from TIC. The different labeling types were broadly divided into six groups: L1, L2, L3, L4, L5, and L6 according to the actual number of labeling pulse.
A total of 5040 regions of interest were evaluated. The peak SI of L3, except for those in the A2 segment of the anterior cerebral artery, was significantly higher than that of L5. However, there were no significant differences between L4 and L5. Although the AUCs of L3 and L4 for anterior circulation were relatively higher than that of the other subgroups, the AUC of L3 was significantly higher than that of L4.
The fast ACTRESS was optimized and indicated that the labeling type of L3 was the most appropriate for the well visualization of intracranial arteries. The fast ACTRESS sequence was useful to acquire well-delineated images of intracranial vessels in ˂1min.
•The fast ACTRESS sequence is useful to acquire the 4D-MRA images within 1min for depicting intracranial vessels.•This acquisition technique can reduce the scan time compared to the conventional ASL-based 4D-MRA scanning.•We optimized the 4D-MRA parameter by modifying the number of IR acquisitions.
Whether diurnal variation exists in quantitative MRI indices such as the T1rho relaxation time (T1ρ) of the intervertebral disc (IVD) is yet to be explored. This prospective study aimed to evaluate ...the diurnal variation in T1ρ, apparent diffusion coefficient (ADC), and electrical conductivity (σ) of lumbar IVD and its relationship with other MRI or clinical indices. Lumbar spine MRI, including T1ρ imaging, diffusion-weighted imaging (DWI), and electric properties tomography (EPT), was conducted on 17 sedentary workers twice (morning and evening) on the same day. The T1ρ, ADC, and σ of IVD were compared between the time points. Their diurnal variation, if any, was tested for correlation with age, body mass index (BMI), IVD level, Pfirrmann grade, scan interval, and diurnal variation in IVD height index. The results showed a significant decrease in T1ρ and ADC and a significant increase in the σ of IVD in the evening. T1ρ variation had a weak correlation with age and scan interval, and ADC variation with scan interval. Diurnal variation exists for the T1ρ, ADC, and σ of lumbar IVD, which should be accounted for in image interpretation. This variation is thought to be due to diurnal variations in intradiscal water, proteoglycan, and sodium ion concentration.
Abstract Purpose Arterial spin labeling (ASL) methods have been widely used for evaluation of cerebral blood flow (CBF) by magnetic resonance imaging. However, ASL methods require setting of the post ...labeling delay (PLD) time for obtaining images. As the hemodynamic status cannot be estimated in each patient, the resultant quantitative values of blood flow may not be accurate. The multi-phase pseudo continuous arterial spin labeling (pCASL) method can be used to obtain images at various time-points. The purpose of this study was to create the transit-time maps for correcting the delayed blood flow and evaluate CBF using the transit-time maps obtained by the multi-phase pCASL method. Materials and Methods Twelve patients who underwent both 3.0-tesla magnetic resonance imaging (MRI) and single photon emission computed tomography with iodine-123-N-isopropyl-p-iodoamphetamine (123I-IMP) were investigated. This study was approved by the institutional review board of our institution. MRI acquisitions included PLD time-fixed (1525 ms) and multi-phase pCASL sequences. The transit-time maps were calculated from multi-phase pCASL images by software. The transit-time maps were applied to PLD-fixed pCASL images pixel by pixel, for calculating the CBF value corrected for peak blood transit time. Regions of interest were drawn on the brain. IMP-CBF, ASL-CBF (default and corrected) and transit time were measured for each segment. Results Twelve patients and 264 segments were investigated. The mean IMP-CBF, ASL-CBF (default, corrected) and transit time were 28.4, 23.0, 29.6, ml/min/100 g and 1977.5 ms, respectively. There were no significant differences between IMP-CBF and ASL-CBF (corrected). Conclusion CBF values can be corrected by using the transit-time maps obtained using the multi-phase pCASL method.
Cognitive training-induced neuroplastic brain changes have been reported. This prospective study evaluated whether microscopic fractional anisotropy (μFA) derived from double diffusion encoding (DDE) ...MRI could detect brain changes following a 4 week cognitive training. Twenty-nine healthy volunteers were recruited and randomly assigned into the training (
= 21) and control (
= 8) groups. Both groups underwent brain MRI including DDE MRI and 3D-T1-weighted imaging twice at an interval of 4-6 weeks, during which the former underwent the training. The training consisted of hour-long dual N-back and attention network tasks conducted five days per week. Training and time-related changes of DDE MRI indices (μFA, fractional anisotropy (FA), and mean diffusivity (MD)) and the gray and white matter volume were evaluated using mixed-design analysis of variance. In addition, any significant imaging indices were tested for correlation with cognitive training-induced task performance changes, using partial correlation analyses. μFA in the left middle frontal gyrus decreased upon the training (53 voxels, uncorrected
< 0.001), which correlated moderately with response time changes in the orienting component of attention (r = -0.521, uncorrected
= 0.032). No significant training and time-related changes were observed for other imaging indices. Thus, μFA can become a sensitive index to detect cognitive training-induced neuroplastic changes.
We have investigated the relationship between heterogeneity and anisotropy in the inner core. Heterogeneity was examined using PKP(DF) and PKP(BC) phases traveling in the east‐west direction (E‐W ...paths). The geographical pattern of the PKP differential travel time (BC‐DF) residuals was found to be a manifestation of degree one heterogeneity in the outermost 100 to 500 km of the inner core. Spherical harmonics analysis showed that the P velocities in the inner core are fast in the region from 43°E to 177°E (the quasi‐eastern hemisphere) with a peak value of +0.29±0.15% and slow in the region from 183°W to 43°E (the quasi‐western hemisphere) with a peak value of −0.66±0.20%. Regional variation of anisotropy in the inner core was examined using PKP phases traveling nearly parallel to the Earth's spin axis (polar paths). The averages of BC–DF time residuals were 2.4±0.8 s in the quasi‐western hemisphere and 0.5±0.4 s in the quasi‐eastern hemisphere. We found that the inner core anisotropy predominates only in the quasi‐western hemisphere in which the 0.66% slow P velocity is observed for the E‐W paths. Geophysical implications of the degree one pattern in the inner core were briefly discussed. We propose that the hemispherical structure of the inner core reflects ancient core dynamics immediately after core formation.
The development of three-dimensional printers has facilitated the creation of patient-specific hollow vessel models. Preoperative simulations using these types of models have improved our ability to ...select appropriate devices and embolic materials before performing complex endovascular procedures. This report describes 2 cases of high-flow renal arteriovenous fistulas (r-AVFs) that were successfully treated via short-segment embolization using the preloading coil-in-plug (p-CIP) technique. To our knowledge, this is the first report of r-AVF being treated using the p-CIP technique. Our findings demonstrate that preoperative simulation has the potential to improve the safety and reliability of complex vascular embolization procedures.
Background/Aims Secondary hemophagocytic syndrome (hemophagocytic lymphohistiocytosis, HLH) follows viral infection, malignant disorders, and autoimmune disease. Criteria for HLH diagnosis, which ...were proposed in 2004, include hypertriglyceridemia. However, some studies reported the absence of hypertriglyceridemia in patients with secondary HLH, differing from those with primary HLH. Subjects and Methods In this study, we investigated the presence or absence of hypertriglyceridemia in 28 patients who were diagnosed with secondary HLH between 1997 and 2007 retrospectively. There were no patients undergoing treatment for those with a history of hyperlipidemia. Results The subjects consisted of 14 patients with lymphoma-associated HLH, 11 with virus-associated HLH, 2 with autoimmune disease-associated HLH, and 1 with post transplantation HLH. In 19 patients (68%), hypertriglyceridemia was noted on diagnosis or during the disease period (mean: 242 mg/dL). Furthermore, the triglyceride (TG) level decreased with the treatment-related amelioration of HLH (mean level before and after treatment: 297 and 136 mg/dL, respectively, p=0.0001). Conclusion These results suggest that the TG level is useful for diagnosing HLH and evaluating the treatment response. TG measurement is simple and inexpensive; therefore, this parameter can be determined several times to evaluate the treatment response.
We compared peak circumferential strain (Ecc) values with spatial modulation of magnetization (SPAMM) and strain-encoded (SENC) magnetic resonance (MR) imaging at 3 tesla. Correlation coefficients of ...the averaged peak Ecc values of the 2 methods were statistically significant. However, the average peak Ecc value was significantly lower with SPAMM (−13.5%±3.3%) than with SENC (−21.6%±3.4%) (P<0.0001). The SENC method showed higher circumferential strain than the SPAMM method at 3T.
The 1998–1999 volcanic unrest of Iwate volcano, northeastern Japan, was marked by 350 deep low-frequency earthquakes (DLFs) and 120 intermediate-depth low-frequency earthquakes (ILFs), as well as an ...intense swarm of shallow volcanic earthquakes that began during 1998 April. The rate of occurrence of the DLFs increased approximately 5 d before that of the shallow volcanic earthquakes increased, and the number of ILFs gradually increased from the middle of 1998. To investigate the relationship between the shallow volcanic activity and the activities of the DLFs and ILFs, we determined their precise hypocentres and source mechanisms by analysing waveform data recorded by a dense seismic network of 47 three-component seismometers located on and around the volcano. The hypocentres of DLFs are concentrated within three regions: the first region is at depths from 31 to 34 km, approximately 10 km south of the summit, the second is at depths from 32 to 36 km approximately 10 km northeast of the summit and the third is at a 37 km depth, approximately 7 km northeast of the summit. In contrast, ILFs are located within a vertical pipe-like region just beneath the summit and sometimes show a vertical migration of the focal depth. Our moment tensor inversion using spectral ratios of body waves indicates that the source mechanisms of the DLFs and ILFs have a significant double couple and a compensated linear-vector dipole component. It is also found that a significant volumetric change is included in the source mechanisms for some DLFs. Such source mechanisms of DLFs and ILFs can be explained by the motion of a tensile crack coupled either with a shear crack or with an oblate spheroid magma chamber. However, the orientations and polarities of the crack motions are not the same in each region of DLFs and ILFs. These results suggest that a complex magma system is present at the source regions of the DLFs and ILFs.
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