Diffusion weighted imaging combining respiratory triggering and navigator echo tracking in the upper abdomen.

OBJECTIVES: To evaluate a new motion correction method, named RT + NV Track, for upper abdominal DWI that combines the respiratory triggering (RT) method using a respiration sensor and the Navigator Track (NV Track) method using navigator echoes. MATERIALS AND METHODS: To evaluate image quality acquired upper abdominal DWI and ADC images with RT, NV, and RT + NV Track in 10 healthy volunteers and 35 patients, signal-to-noise efficiency (SNRefficiency) and the coefficient of variation (CV) of ADC values were measured. Five radiologists independently performed qualitative image-analysis assessments. RESULTS: RT + NV Track showed significantly higher SNRefficiency than RT and NV (14.01 ± 4.86 vs 12.05 ± 4.65, 10.05 ± 3.18; p < 0.001, p < 0.001). RT + NV Track was superior to RT and equal or better quality than NV in CV and visual evaluation of ADC values (0.033 ± 0.018 vs 0.080 ± 0.042, 0.057 ± 0.034; p < 0.001, p < 0.001). RT + NV Track tends to acquire only expiratory data rather than NV, even in patients with relatively rapid breathing, and can correct for respiratory depth variations, a weakness of RT, thus minimizing image quality degradation. CONCLUSION: The RT + NV Track method is an efficient imaging method that combines the advantages of both RT and NV methods in upper abdominal DWI, providing stably good images in a short scan time.

Assessment of cerebral perfusion in moyamoya disease with dynamic pseudo-continuous arterial spin labeling using a variable repetition time scheme with optimized background suppression.

PURPOSE: Accurate assessment of cerebral perfusion in moyamoya disease is necessary to determine the indication for treatment. We aimed to investigate the usefulness of dynamic PCASL using a variable TR scheme with optimized background suppression in the evaluation of cerebral perfusion in moyamoya disease. METHODS: We retrospectively analyzed the images of 24 patients (6 men and 18 women, mean age 31.4 ± 18.2 years) with moyamoya disease; each of whom was imaged with both dynamic PCASL using the variable-TR scheme and 123IMP SPECT with acetazolamide challenge. ASL dynamic data at 10 phases are acquired by changing the LD and PLD. The background suppression timing was optimized for each phase. CBF and ATT were measured with ASL, and CBF and CVR to an acetazolamide challenge were measured with SPECT. RESULTS: A significant moderate correlation was found between the CBF measured by dynamic PCASL and that by SPECT (r = 0.53, P < 0.001). The CBF measured by dynamic PCASL (52.5 ± 13.3 ml/100 mg/min) was significantly higher than that measured by SPECT (43.0 ± 12.6 ml/100 mg/min, P < 0.001). The ATT measured by dynamic PCASL showed a significant correlation with the CVR measured by SPECT (r = 0.44, P < 0.001). ATT was significantly longer in areas where the CVR was impaired (CVR < 18.4%, ATT = 1812 ± 353 ms) than in areas where it was preserved (CVR > 18.4%, ATT = 1301 ± 437 ms, P < 0.001). The ROC analysis showed a moderate accuracy (AUC = 0.807, sensitivity = 87.7%, specificity = 70.4%) when the cutoff value of ATT was set at 1518 ms. CONCLUSION: Dynamic PCASL using this scheme was found to be useful for assessing cerebral perfusion in moyamoya disease.

Three-dimensional multicontrast blood imaging with a single acquisition: Simultaneous non-contrast-enhanced MRA and vessel wall imaging in the thoracic aorta.

PURPOSE: To evaluate MRA and vessel wall imaging (VWI) image quality in the thoracic aorta using a novel method named BRIDGE (bright and dark blood images with multishot gradient-echo EPI). METHODS: The BRIDGE method consists of 3D multishot gradient-echo EPI acquisition using pulse gating, navigator gating, and magnetization preparation with a T2 -preparation pulse and a nonselective inversion-recovery pulse. The BRIDGE and conventional methods (noncontrast MRA based on 3D turbo-field-echo [TFE] and VWI based on 3D turbo spin echo with variable refocusing flip angle [VRFA-TSE]) were performed in 10 healthy volunteers and 10 patients. The SNR, contrast-to-noise ratio (CNR), and sharpness in the thoracic aorta were compared for MRA evaluation. The values of SNRlumen , SNRwall , CNRwall-lumen , contrast ratio (CR)lumen-muscle , coefficient of variation, sharpness, lumen area, and wall area in the thoracic aorta were compared for VWI evaluation. Two radiologists independently performed qualitative image-analysis assessments. RESULTS: When MRA and VWI were acquired, the acquisition time was 26.6% to 27.8% shorter with BRIDGE than the conventional method. In the MRA evaluation, BRIDGE and TFE methods were comparable. In the VWI evaluation, BRIDGE was superior to the VRFA-TSE method in blood suppression and evaluation of the ascending aorta. Because the blood signal suppression of BRIDGE is based on the T1 value of blood, the blood signal can be suppressed more uniformly than with the VRFA-TSE method, regardless of age, blood flow velocity, or vascular anatomy. CONCLUSION: The BRIDGE method can provide both MRA, to assess vascular anatomy and luminal changes, and VWI, to assess the vessel wall and detect vulnerable plaques, in a single scan.

Flow independent black blood imaging with a large FOV from the neck to the aortic arch: A feasibility study at 3 tesla.

PURPOSE: To investigate the feasibility of obtaining black-blood imaging with a large FOV from the neck to the aortic arch at 3 T using a newly modified Relaxation-Enhanced Angiography without Contrast and Triggering for Black-Blood Imaging (REACT-BB). MATERIALS AND METHODS: REACT-BB provides black-blood images by adjusting the inversion time (TI) in REACT to the null point of blood. The optimal TI for REACT-BB was investigated in 10 healthy volunteers with TI varied from 200 ms to 1400 ms. Contrast ratios were calculated between muscle and three branch arteries of the aortic arch. Additionally, a comparison between REACT-BB and MPRAGE involved evaluating the depiction of high-intensity plaques in 222 patients with stroke or transient ischemic attack. Measurements included plaque-to-muscle signal intensity ratios (PMR), plaque volumes, and carotid artery stenosis rates in 60 patients with high-intensity plaques in carotid arteries. RESULTS: REACT-BB with TI = 850 ms produced the black-blood image with the best contrast between blood and background tissues. REACT-BB outperformed MPRAGE in depicting high-intensity plaques in the aortic arch (55.4% vs 45.5%) and exhibited superior overall image quality in visual assessment (3.31 ± 0.70 vs 2.89 ± 0.73; p < 0.05). Although the PMR of REACT-BB was significantly lower than MPRAGE (2.227 ± 0.601 vs 2.285 ± 0.662; P < 0.05), a strong positive correlation existed between REACT-BB and MPRAGE (ρ = 0.935; P < 0.05), and all high-intensity plaques that MPRAGE detected were clearly detected by REACT-BB. CONCLUSION: REACT-BB provides black-blood images with uniformly suppressed fat and blood signals over a large FOV from the neck to the aortic arch with comparable or better high-signal plaque depiction than MPRAGE.

Relationship between mesoscale dynamics and shear relaxation of ionic liquids with long alkyl chain.

The shear relaxation spectra of three imidazolium-based ionic liquids, 1-methyl-3-octylimidazolium chloride ([C(8)mim][Cl]), 1-methyl-3-octylimidazolium hexafluorophosphate ([C(8)mim][PF(6)]), and 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C(12)mim][TFSA]) were measured and compared with the intermediate scattering functions determined with neutron spin echo (NSE) spectroscopy. The shear relaxation is slower than that predicted from the relaxation of the main peak of the structure factor that is common to other molecular liquids, whereas it is faster than that from the relaxation of the pre-peak, that corresponds to the correlation length of about 10 nm specific to ionic liquids with an intermediately long alkyl chain. The role of the pre-peak structure in the mechanism of shear viscosity of ionic liquids is discussed based on the comparison between NSE and shear relaxations.

Improved selective visualization of internal and external carotid artery in 4D-MR angiography based on super-selective pseudo-continuous arterial spin labeling combined with CENTRA-keyhole and view-sharing (4D-S-PACK).

PURPOSE: Four-dimensional magnetic resonance angiography (4D-MRA) based on super-selective pseudo-continuous arterial spin labeling, combined with Keyhole and View-sharing (4D-S-PACK) was introduced for scan-accelerated vessel-selective 4D-MRA. Label selectivity and visualization effectiveness were assessed. METHODS: Nine healthy volunteers were included in the study. The label selectivity for the imaging of internal carotid artery (ICA) and external carotid artery (ECA) circulation was assessed qualitatively. The contrast-to-noise ratio (CNR) in 4D-S-PACK was measured in four middle cerebral artery (MCA) and superficial temporal artery (STA) segments and compared with that in contrast-inherent inflow-enhanced multi-phase angiography combined with the vessel-selective arterial spin labeling technique (CINEMA-select). Vessel-selective arterial visualization in 4D-S-PACK was assessed qualitatively in a patient with dural arteriovenous fistula and compared with digital subtraction angiography (DSA) and non-vessel selective 4D-PACK. RESULTS: 4D-S-PACK vessel selectivity was judged to be at a clinically acceptable level in all cases except one ECA-targeted label. The CNR was significantly higher using 4D-S-PACK compared with CINEMA-select in MCA and STA peripheral segments (p < 0.001). In patient examination, territorial flow visualization in feeding artery and draining vein circulation on 4D-S-PACK were comparable with that on DSA and the identification of such responsible vessels was easier on 4D-S-PACK than on 4D-PACK. CONCLUSION: 4D-S-PACK showed high vessel-selectivity and higher visualization effectiveness compared with CINEMA-select. One clinical case was performed and ICA and ECA territorial flow was successfully visualized separately, suggesting clinical usefulness.

The Power of Traditional Design Techniques: The Effects of Viewing a Japanese Garden on Individuals With Cognitive Impairment.

PURPOSE: This study is to examine how viewing a Japanese garden affects Japanese patients with dementia. BACKGROUND: In a previous study, authors explored the effect on individuals with Alzheimer's disease of viewing an indoor Japanese garden at a nursing home in the United States and reported that viewing the garden significantly reduced the heart rate, evoked short-term and long-term memories, and improved behavioral symptoms. However, it was unclear whether these effects were caused by the design of Japanese garden or unfamiliarity of the design to Caucasians. METHODS: We constructed a Japanese garden on the rooftop of a hospital in Japan and assessed with a total of 25 subjects on the following categories: (1) eye movement, (2) heart rate, and (3) behavior under four different conditions: (a) open view of the site before construction of the Japanese garden (the control space), (b) open view of the Japanese garden, (c) view of the Japanese garden through closed door, and (d) view of Japanese garden through closed door with the chrysanthemum scent. Findings/Results: Viewers' eyes scanned larger area while viewing the Japanese garden, and viewing the Japanese garden significantly reduced heart rate and improved behavioral symptoms than the control space. We also found that the effect of viewing the same Japanese garden differed across three conditions: the view through an open door, a closed door, and a closed door with added scent.

Structural heterogeneity and unique distorted hydrogen bonding in primary ammonium nitrate ionic liquids studied by high-energy X-ray diffraction experiments and MD simulations.

Liquid structure and the closest ion-ion interactions in a series of primary alkylammonium nitrate ionic liquids [C(n)Am(+)][NO(3)(-)] (n = 2, 3, and 4) were studied by means of high-energy X-ray diffraction (HEXRD) experiments with the aid of molecular dynamics (MD) simulations. Experimental density and X-ray structure factors are in good accordance with those evaluated with MD simulations. With regard to liquid structure, characteristic peaks appeared in the low Q (Q: a scattering vector) region of X-ray structure factors S(Q)'s for all ionic liquids studied here, and they increased in intensity with a peak position shift toward the lower Q side by increasing the alkyl chain length. Experimentally evaluated S(Q(peak))(r(max)) functions, which represent the S(Q) intensity at a peak position of maximum intensity Q(peak) as a function of distance (actually a integration range r(max)), revealed that characteristic peaks in the low Q region are related to the intermolecular anion-anion correlation decrease in the r range of 10-12 Å. Appearance of the peak in the low Q region is probably related to the exclusion of the correlations among ions of the same sign in this r range by the alkyl chain aggregation. From MD simulations, we found unique and rather distorted NH···O hydrogen bonding between C(n)Am(+) (n = 2, 3, and 4) and NO(3)(-) in these ionic liquids regardless of the alkyl chain length. Subsequent ab initio calculations for both a molecular complex C(2)H(5)NH(2)···HONO(2) and an ion pair C(2)H(5)NH(3)(+)···ONO(2)(-) revealed that such distorted hydrogen bonding is specific in a liquid state of this family of ionic liquids, though the linear orientation is preferred for both the N···HO hydrogen bonding in a molecular complex and the NH···O one in an ion pair. Finally, we propose our interpretation of structural heterogeneity in PILs and also in APILs.

Liquid structure of and Li+ ion solvation in bis(trifluoromethanesulfonyl)amide based ionic liquids composed of 1-ethyl-3-methylimidazolium and N-methyl-N-propylpyrrolidinium cations.

Liquid structures of the bis(trifluoromethanesulfonyl)amide based ionic liquids composed of 1-ethyl-3-methylimidazolium and N-methyl-N-propylpyrrolidinium ([C(2)mIm(+)][TFSA(-)] and [C(3)mPyrro(+)][TFSA(-)], respectively) and Li(+) ion solvation structure in their lithium salt solutions were studied by means of high-energy X-ray diffraction (HEXRD) technique with the aid of MD simulations. With regard to neat ionic liquids, a small but significant difference was found at around 3.5 Å in the intermolecular radial distribution functions G(inter)(r)s for these two ionic liquids; i.e., G(inter)(r) for [C(2)mIm(+)][TFSA(-)] was positioned at a slightly shorter region relative to that for [C(3)mPyrro(+)][TFSA(-)], which suggests that the nearest neighboring cation-anion interaction in the imidazolium ionic liquid is slightly greater than that in the other. With regard to Li(+) ion solvation structure, G(inter)(r)s for [C(2)mIm(+)][TFSA(-)] dissolving Li(+) ion exhibited additional small peak of about 1.9 Å attributable to the Li(+)-O (TFSA(-)) atom-atom correlation, though the corresponding peak was unclear in [C(3)mPyrro(+)][TFSA(-)] due to overlapping with the intramolecular atom-atom correlations in [C(3)mPyrro(+)]. In addition, the long-range density fluctuation observed in the neat ionic liquids diminished with the increase of Li(+) ion concentration for both ionic liquid solutions. These observations indicate that the large scale Li(+) ion solvated clusters are formed in the TFSA based ionic liquids, and well support the formation of [Li(TFSA)(2)](+) cluster clarified by previous Raman spectroscopic studies. MD simulations qualitatively agree with the experimental facts, by which the decrease in the long-range oscillation amplitude of r(2){G(r) - 1} for the Li(+) containing ionic liquids can be ascribed to the variation in the long-range anion-anion correlations caused by the formation of the Li(+) ion solvated clusters.

Dependence of the conformational isomerism in 1-n-butyl-3-methylimidazolium ionic liquids on the nature of the halide anion.

The conformational isomerism of the 1-n-butyl-3-methylimidazolium cation, [C(4)mim](+), in halide-based ionic liquids--[C(4)mim]Cl, [C(4)mim]Br, and [C(4)mim]I--was explored by Raman spectroscopy. The [C(4)mim](+) cation exhibits trans-gauche conformational isomerism with respect to the N1-C7-C8-C9 dihedral angle of its butyl chain. The thermodynamics of trans-gauche conversion were analyzed through the successful evaluation of the corresponding Gibbs free energy, Δ(iso)G°, enthalpy, Δ(iso)H°, and entropy, Δ(iso)S°, of conformational isomerization. The values of Δ(iso)G° obtained are small (a few units of kJ/mol) and show a slight negative variation with the decrease of the size of the halide anion. On the other hand, Δ(iso)H° and Δ(iso)S° values are positive for [C(4)mim]I and decrease with the anion size to yield negative values for [C(4)mim]Cl and [C(4)mim]Br. This suggests that the negative electrostatic field around the halide anions stabilizes the gauche isomer from an enthalpic point of view. In order to study the structure and ion-ion interactions in this type of ionic liquids, high-energy X-ray diffraction experiments were performed for [C(4)mim]Cl at different temperatures and for supercooled [C(4)mim][Br] at ambient temperature. Molecular dynamics (MD) simulations for these systems were also carried out at several temperatures. Δ(iso)G° and Δ(iso)H° values derived from the simulations qualitatively agree with the experimental ones. Experimental X-ray structure factors are also well reproduced by the simulations. The MD results also allowed the calculation of different spatial distribution functions (SDFs) for the three ionic liquids. Although all SDFs exhibit similar trends, [C(4)mim]I shows a reduced anion density facing the C(2)-H atoms of the cation and enhanced anion densities above and below the imidazolium ring plane. This indicates that anions localized near the C(2)-H atoms of the cation can stabilize their gauche conformer, an effect that is stronger with smaller anions. This conclusion is also supported by ab initio calculations at the CCSD(T) level for isolated ion pairs.