Higher b-values improve the correlation between diffusion MRI and the cortical microarchitecture.

PURPOSE: In diffusion MRI (dMRI), it remains unclear to know how much increase of b-value is conveying additional biological meaning. We tested the correlations between cortical microarchitecture and diffusion metrics computed from standard (1000 s/mm2), high (3000 s/mm2), to very high (5000 s/mm2) b-value dMRI. METHODS: Healthy volunteers were scanned with a dMRI pulse sequence that was first optimized together with a T1-WI and T2-WI. Averaged cortical surface map of estimated myelin (T1-WI/T2-WI) was compared with surface maps of mean diffusivity (MD) computed from each b-value (MD1000, MD3000, and MD5000) and to surface map of mean kurtosis (MK computed from the 0-, 1000-, to 3000-s/mm2 shells) in 360 cortical parcels using Spearman correlations, multiple linear regressions, and Akaike information criteria (AIC). RESULTS: Surface map from MD1000 showed variations not related to myelin but the MD3000 and MD5000 maps inversely mirrored estimated myelin map; lower MD values being observed in more myelinated cortical areas. MK mirrored myelinated cortical areas. Quantitatively, Spearman correlations between myelin and MD became more and more negative as long as b-values increased while the correlation was positive between myelin and MK. Multiple regression models confirmed negative associations between myelin and MD that were significantly better from MD1000 to MD3000 and MD5000 (R2 = 0.33, p < 0.001; R2 = 0.43, p < 0.001; and R2 = 0.50, p < 0.001) and positive association between myelin and MK (R2 = 0.53, p < 0.001). Comparisons of the 3 statistical models showed the best performances with MK and MD5000 (AICMK < AICMD5000 < AICMD3000 < AICMD1000). CONCLUSION: Higher b-values are more closely related to subtle cellular variations of the cortical microarchitecture.

Detection of in-stent protrusion (ISP) by intravascular ultrasound during carotid stenting: Usefulness of stent-in-stent placement for ISP.

OBJECTIVES: As in-stent protrusion (ISP) during carotid artery stenting (CAS) may cause postoperative embolism, ISP detection is important. Intravascular ultrasound examination (IVUS) is useful for ISP detection because the blood vessel cross-section can be drawn as a tomogram from the lumen. Our objective was to clarify the occurrence of ISP during CAS using IVUS and relevant factors, and to report the usefulness of stent-in-stent placement when treating ISP. METHODS: In 142 consecutive patients (128 men, average age 71.7 years; 69 symptomatic) who underwent CAS using dual protection and the blood aspiration method, and subsequent IVUS after stent placement were included. The outcome of CAS, and the occurrence rate of ISP and related factors (plaque characteristics, stent design, intraoperative debris capture rate and postoperative diffusion-weighted imaging (DWI) positive rate) were examined. RESULTS: All CAS procedures were successful and no major adverse events (MAEs) were observed at 30 days. ISP was found in 12% (17/142), and stent-in-stent placement was performed in all cases. Vulnerable plaques were observed in 12 of 17 ISP cases (71%). A closed stent was used in 13 of 17 ISP cases (71%). The intraoperative debris capture rate was 100%, and no neurological symptoms were observed in any patients. A significant increase in ISP susceptibility was related to vulnerable plaques and the intraoperative debris capture rate. CONCLUSIONS: Vulnerable plaques and debris capture were significantly correlated with ISP occurrence. In all ISP cases, stent-in-stent placement was performed and good results were obtained. KEY POINTS: • ISP detection during CAS using IVUS is important. • ISP-positive patients were correlated with NASCET ≥ 80%, vulnerable plaques and stent length. • Adequate additional treatment of stent in stenting under reliable protection against ISP-positive patients achieved low perioperative complications.

Impact of an infectious disease specialist on antifungal use: an interrupted time-series analysis in a tertiary hospital in Tokyo.

BACKGROUND: Antimicrobial stewardship programmes are considered essential for optimizing antimicrobial use in order to improve patient outcomes, reduce the number of adverse sequelae, prevent resistance, and ensure cost-effective therapy. AIM: To assess the efficacy and the limitations of antifungal antimicrobial stewardship programmes. METHODS: A bundle to manage infectious diseases was implemented in our hospital in October 2010. Data regarding antimicrobial use density (AUD) from April 2006 to May 2016 were collected. Trends in AUD were assessed using an interrupted time-series model for three separate periods: the pre-bundle, the bundle implementation, and the long-term follow-up periods. The primary and secondary outcomes were AUD (defined daily dose (DDD) per 1000 patient-days) of intravenous antifungals and expenditure on antifungals per fiscal year, respectively. FINDINGS: The AUD for all intravenous antifungals decreased from 26.1 in 2006 to 9.9 in 2015. Whereas the change in the trend during the pre-bundle period was not significant (slope: 0.062; 95% confidence interval (CI): -0.180 to 0.305), a significant decrease was observed in the bundle implementation period (slope: -0.535; 95% CI: -0.907 to -0.164). The trend slowed during the long-term follow-up period (slope: -0.040; 95% CI: -0.218 to 0.138). Total expenditure on antifungals decreased by 73%, from ¥52,354,411 in fiscal year 2006 to ¥14,073,099 in fiscal year 2015. CONCLUSION: The bundle significantly reduced the use of antifungals and decreased costs over time, but this effect was limited in that it had stabilized within three years.

Vascular Wall Imaging of Unruptured Cerebral Aneurysms with a Hybrid of Opposite-Contrast MR Angiography.

BACKGROUND AND PURPOSE: Inflammation and degeneration of the intracranial saccular aneurysm wall play a major role in aneurysm formation, development and subsequent rupture. The aim of this study was to characterize the walls of unruptured intracranial aneurysms by using a hybrid of opposite-contrast MRA at 3T. MATERIALS AND METHODS: Fourteen consecutive patients with 17 unruptured intracranial aneurysms who initially underwent clipping surgery were prospectively evaluated. All aneurysms were scanned preoperatively by using a hybrid of opposite-contrast MRA in 3T high-resolution MR imaging. We classified intraoperative findings of atherosclerotic plaques in the aneurysms into 3 grades: grade A (major plaques), grade B (minor plaques), and grade C (no plaques). The contrast ratio of the high-intensity area was also measured relative to the background low-intensity area inside the carotid artery. RESULTS: Findings from preoperative plaque imaging of the aneurysm corresponded to the intraoperative findings in 15 of 16 aneurysms (excluding 1 that was impossible to visualize in its entirety due to anatomic reasons). Overall sensitivity and specificity of the hybrid of opposite-contrast MRA were 88.9% and 100%, respectively. During the operation, 4 aneurysms were classified as grade A; 5, as grade B; and 7, as grade C. The means of the contrast ratio for grades A, B, and C were 0.72 ± 0.03, 0.34 ± 0.30, and -0.02 ± 0.09, respectively. CONCLUSIONS: The hybrid of opposite-contrast MRA can detect visible atherosclerotic plaques in the unruptured aneurysm wall, and the contrast ratio in intracranial aneurysms correlated with their presence and extent. A study including a larger series is needed to validate the diagnostic potential of this imaging technique.

Reconstruction of transcription-translation dynamics with a model of gene networks.

A transcription-translation model of gene networks and a method to reconstruct it from gene expression data are proposed. The model is a hybrid system based on the Glass network with continuous-time dynamics and logical interactions. Transcription-translation dynamics is introduced into the Glass network. The reconstruction of gene networks is reduced to the problem of estimating logical functions from binary representations of quantities of mRNAs and proteins. The reconstruction method is applied to the gene expression data of circadian rhythms. The response characteristics of the reconstructed gene network to periodic stimuli are analyzed. The results suggest the existence of a receiver gene that responds to an external signal, consistently with biological knowledge.

Endovascular treatment for dural arteriovenous fistula of the anterior condylar confluence involving the anterior condylar vein. A report of two cases.

SUMMARY: Anterior condylar confluence (ACC) dural arteriovenous fistula (AVF) is a rare anomaly. We describe two cases of ACC dural AVF involving the anterior condylar vein that were successfully treated with selective transvenous coil embolization. The first patient presented with headache and right pulse-synchronous tinnitus, and demonstrated abnormal flow medial to the jugular bulb within the right hypoglossal canal on source image of magnetic resonance angiography (MRA). Arterioangiography disclosed a dural AVF in this area, supplied mainly by the meningeal branches of the bilateral ascending pharyngeal artery. We diagnosed ACC dural AVF involving the anterior condylar vein and transvenous embolization was successfully performed. The second patient presented with right pulse-synchronous tinnitus. Views of source image of MRA and arterioangiography were similar to the first case and, again, transvenous embolization was successfully performed. ACC dural AVF is a rare condition and knowledge of the anatomy of the venous system around the craniocervical junction is required for successful treatment.

Detection of mutual determinism between a pair of spike trains.

A method for detecting mutual deterministic dependence between a pair of spike trains is proposed. When it is assumed that a cell assembly, which is a subgroup of neurons processing a common task, is constituted as a dynamical system, then the mutual determinism between constituent neurons may be directly reflected in functional connectivity in the assembly. The deterministic dependence between two spike trains can be measured with statistical significance using a method of nonlinear prediction. Some examples of simulations are demonstrated in both deterministic and stochastic cases.

Contrast-enhanced MR angiography of the carotid artery using 3D time-resolved imaging of contrast kinetics: comparison with real-time fluoroscopic triggered 3D-elliptical centric view ordering.

PURPOSE: To evaluate contrast-enhanced MR angiography using the 3D time-resolved imaging of contrast kinetics technique (3D-TRICKS) by direct comparison with the fluoroscopic triggered 3D-elliptical centric view ordering (3D-ELLIP) technique. METHODS: 3D-TRICKS and 3D-ELLIP were directly compared on a 1.5-Tesla MR unit using the same spatial resolution and matrix. In 3D-TRICKS, the central part of the k-space is updated more frequently than the peripheral part of the k-space, which is divided in the slice-encoding direction. The carotid arteries were imaged using 3D-TRICKS and 3D-ELLIP sequentially in 14 patients. Temporal resolution was 12 sec for 3D-ELLIP and 6 sec for 3D-TRICKS. The signal-to-noise ratio (S/N) of the common carotid artery was measured, and the quality of MIP images was then scored in terms of venous overlap and blurring of vessel contours. RESULTS: No significant difference in mean S/N was seen between the two methods. Significant venous overlap was not seen in any of the patients examined. Moderate blurring of vessel contours was noted on 3D-TRICKS in five patients and on 3D-ELLIP in four patients. Blurring in the slice-encoding direction was slightly more pronounced in 3D-TRICKS. However, qualitative analysis scores showed no significant differences. CONCLUSION: When the spatial resolution of the two methods was identical, the performance of 3D-TRICKS was found to be comparable in static visualization of the carotid arteries with 3D-ELLIP, although blurring in the slice-encoding direction was slightly more pronounced in 3D-TRICKS. 3D-TRICKS is a more robust technique than 3D-ELLIP, because 3D-ELLIP requires operator-dependent fluoroscopic triggering. Furthermore, 3D-TRICKS can achieve higher temporal resolution. For the spatial resolution employed in this study, 3D-TRICKS may be the method of choice.

Calcium level-responsive in-vitro zinc release from zinc containing tricalcium phosphate (ZnTCP).

The in vitro Zn release from tricalcium phosphate containing Zn (ZnTCP; 0.63, 6.17, and 12.05 Zn w/w%) was investigated. The rates of release from ZnTCP powders were measured in 25 mL of simulated body fluid (SBF) containing 10 mg/100mL Ca (SBF/H), 5 mg/100mL Ca (SBF/L), or no Ca (SBF/-) at pH 7.25, 37.0+/-0.1 degrees C. The release from 6 and 12% ZnTCP was initially very fast. The rate of release from ZnTCP decreased as the concentration of Ca in the dissolution media increased, but increased as concentration of Zn in TCP increased. The dissolution kinetics of ZnTCP followed the Hixon-Crowell equation at the initial stage of dissolution, and the initial dissolution rate constant (IDR) was calculated by the least-squares method. The effect of Ca concentration on percent IDR of ZnTCP suggested that Zn release from 0.6% ZnTCP was significantly high compared to that from 6 or 12% ZnTCP. The relationship between the amount of Ca precipitated and Zn release of various ZnTCP samples suggested that the release from 0.6% ZnTCP was significantly different compared to that from 6 and 12% ZnTCP, consistent with the data for percent Zn IDR. X-ray diffraction data suggested that 0.6% ZnTCP contained 5% hydroxyapatite, a low solubility material, which acted as seed crystal during the dissolution test.

MR imaging of the enlarged endolymphatic duct and sac syndrome by use of a 3D fast asymmetric spin-echo sequence: volume and signal-intensity measurement of the endolymphatic duct and sac and area measurement of the cochlear modiolus.

BACKGROUND AND PURPOSE: In enlarged endolymphatic duct (EED) and sac (EES) syndrome, deformity of the EED and EES is congenital; however, hearing loss is acquired. To investigate the pathophysiology of progressive sensorineural hearing loss in EED and EES syndrome, we measured the volume of the EED and EES, the diameter of the EED and EES, the area of the cochlear modiolus, and the signal intensity of the EES and compared our findings against degree of hearing loss. METHODS: Thin-section MR images of 33 ears in 17 patients with EED and EES syndrome were studied. All studies were obtained on a 1.5-T MR unit using a quadrature surface phased-array coil. Heavily T2-weighted 3D fast asymmetric spin-echo images were obtained with a voxel size of 0.3 x 0.3 x 0.8 mm without zero-fill interpolation. Two radiologists traced the areas of the EED and EES manually, and the volume was calculated. The area of the cochlear modiolus, diameter of the EED and EES, and signal intensity of the EES were also measured by drawing regions of interest manually. The signal intensity ratio of EES/CSF was calculated. These measured values were compared against audiographic data, and the degree of linear correlation was determined. RESULTS: The volume of the EED and EES, the area of the modiolus, the diameter of the EED and EES, and the signal intensity of the EES did not show significant correlation with degree of hearing loss. CONCLUSION: These findings suggest that there is a microscopic area of damage or fragility in the inner ear not visible even with thin-section heavily T2-weighted MR imaging.

Preparation, solubility, and cytocompatibility of zinc-releasing calcium phosphate ceramics.

Zinc is an essential trace element with stimulatory effects on bone formation. Therefore, zinc was doped into beta-tricalcium phosphate to develop zinc-releasing biomaterials to promote bone formation. The zinc-doped beta-tricalcium phosphate, beta-tricalcium phosphate, and hydroxyapatite powders were mixed at a (Ca+Zn)/P molar ratio of 1.60, followed by sintering into a dense body at 1100 degrees C for 1 h. The sintered body was a composite ceramic consisting of zinc-doped beta-tricalcium phosphate and hydroxyapatite phases. The composite ceramic contained zinc oxide when the zinc content was higher than 1.20 wt %. The composite ceramic released zinc under pseudophysiological conditions. However, the release of calcium and phosphate decreased with an increase in zinc content in a range higher than 0.12 wt % owing to a decrease in solubility of the zinc-doped beta-tricalcium phosphate phase. Proliferation of osteoblastic MC3T3-E1 cells was significantly increased on the composite ceramic with a zinc content from 0.6 to 1.20 wt %, compared with those without zinc. When the zinc content was higher than 1.20 wt %, release of zinc from the zinc oxide caused cytotoxicity. Therefore, the zinc content of the composite ceramic must be <1.20 wt %.

Stimulatory effect of zinc-releasing calcium phosphate implant on bone formation in rabbit femora.

Although hydroxyapatite (HAP) and tricalcium phosphate (TCP) are currently used as bone graft substitutes or coatings on metallic prostheses because of their excellent biocompatibility and osteoconductivity, they do not stimulate bone formation or inhibit bone resorption. Zinc, an essential trace element in many animals, has a direct specific proliferative effect on osteoblastic cells and has a potent and selective inhibitory effect on osteoclastic bone resorption in vitro. Therefore, zinc-containing beta-tricalcium phosphate (ZnTCP) ceramics and composite ceramics of ZnTCP and HAP (ZnTCP/HAP) were implanted in the femora of New Zealand White rabbits for 4 weeks to promote bone formation. The implants were sintered ceramics with zinc contents of 0 (control), 0.063, 0.316 and 0.633 wt %. Histological and histomorphometrical investigation of the undecalcified sections revealed an increase by 51% (p =.0509) in the area of newly formed bone around the ZnTCP/HAP implants of 0. 316 Zn wt % compared with the control. Plasma zinc concentration was unchanged. An increased bone resorption on the endosteal surface was observed when ZnTCP and ZnTCP/HAP of 0.633 Zn wt % were implanted. To promote bone formation, the optimum zinc content of the calcium phosphate ceramics was therefore 0.316 wt %.

High-resolution MR images of inner ear internal anatomy using a local gradient coil at 1.5 Tesla: correlation with histological specimen.

PURPOSE: To obtain high-resolution MR images of the inner ear at 1.5 Tesla with a local gradient coil and to correlate these images with the histological specimen. MATERIALS AND METHODS: All studies were performed on a 1.5 Tesla MR unit with a local gradient coil (23 mT/m, slew rate of 107 mT/m/ms). The cranio-facial region of a cadaver was examined using 3D-fast spin echo (FSE) imaging with the voxel size of 0.27 mm x 0.27 mm x 0.5 mm in 9 h 37 min. Two normal volunteers were examined with the same system using 3D-FSE imaging with the voxel size of 0.20 mm x 0.26 mm x 1.0 mm in 57 min. These images were correlated with the cadaver images and histological specimens. RESULTS: On cadaver images, internal structures such as the macula utriculi, macula sacculi, crista ampullaris, lamina spiralis ossea, ligamentum spirale cochleae, modiolus, scala tympani, scala vestibuli, and cochlear aqueduct were visualized. On the images of both volunteers, the same structures were visualized as on the cadaver images. CONCLUSIONS: This study confirmed that high-resolution MR images obtained at 1.5 Tesla can visualize inner ear internal anatomy. Knowledge obtained in this study may be of significant value for the diagnosis of pathology in the area of the inner ear.

MR imaging of the cochlear modiolus: area measurement in healthy subjects and in patients with a large endolymphatic duct and sac.

PURPOSE: To evaluate the cochlear modiolus with thin-section magnetic resonance (MR) imaging in healthy subjects and patients with a large endolymphatic duct and sac, and to assess whether the cochlea is normal or abnormal in patients with a large endolymphatic duct and sac. MATERIALS AND METHODS: MR images were obtained in 10 ears in five volunteers (group 1), 40 ears in 20 patients with bilateral sensory hearing loss (group 2), three ears in two patients with Mondini malformation (group 3), and 12 ears in seven patients with a large endolymphatic duct and sac (group 4). RESULTS: In groups 1 and 2, all modiolar areas were larger than 4.0 mm2. In group 3, each modiolus was smaller than 2.0 mm2. In group 4, modiolar areas were smaller than 2.0 mm2 in eight ears and were larger than 4.0 mm2 in four ears. CONCLUSION: Findings in this study confirm that a large endolymphatic duct and sac is frequently associated with modiolar deficiency, but the modiolar area is normal in some cases. This result does not support the recently proposed hypothesis that hearing loss with a large endolymphatic duct and sac is caused by the transmission of subarachnoid pressure forces into the labyrinth through a deficient modiolus.

Magnitude subtraction vs. complex subtraction in dynamic contrast-enhanced 3D-MR angiography: basic experiments and clinical evaluation.

Magnitude subtraction and complex subtraction in dynamic contrast-enhanced three-dimensional magnetic resonance (3D-MR) angiography were compared using a phantom and 23 human subjects. In phantom studies, complex subtraction showed far better performance than magnitude subtraction, especially for longer echo times, with thicker slices, and without fat suppression. With complex subtraction, non-fat-suppressed studies showed contrast-to-noise ratios comparable to those in fat-suppressed studies. In human subjects, complex subtraction was superior to magnitude subtraction in 9 subjects, but comparable to magnitude subtraction in 14 subjects. There were no cases in which magnitude subtraction was superior to complex subtraction. Although the differences observed in human studies when complex subtraction was applied with thinner slices, shorter echo times, and the fat-suppression technique were not as pronounced as those seen in phantom studies, complex subtraction should be performed in dynamic contrast-enhanced 3D-MR angiography because there are no drawbacks in complex subtraction. Further research is necessary to assess the feasibility of dynamic contrast-enhanced 3D-MR angiography without fat suppression in human subjects using complex subtraction, as suggested by the results of phantom studies. If it is found to be feasible, dynamic contrast-enhanced 3D-MR angiography without fat suppression using complex subtraction may prove to be a robust technique that eliminates the need for shimming and can reduce the acquisition time. J. Magn. Reson. Imaging 1999;10:813-820.

High-resolution MR cisternography of the cerebellopontine angle: 2D versus 3D fast spin-echo sequences.

BACKGROUND AND PURPOSE: The clinical usefulness of MR cisternography of the cerebellopontine angle, applying 2D or 3D fast spin-echo sequences, has been reported recently. Our purpose was to investigate the cause of signal loss in CSF in the prepontine or cerebellopontine angle cistern on 2D FSE MR images and to compare the cisternographic effects of 2D and 3D FSE sequences. METHODS: Preliminary experiments were performed in four volunteers to assess the causes of signal loss. Initially, using a 2D cardiac-gated cine phase-contrast method with a velocity encoding value of 6 cm/s, we measured the velocity and flow pattern of CSF. Comparisons were made to assess the effects of intravoxel dephasing, amplitude of the section-selecting gradient, echo time (TE), and section thickness. Four healthy subjects and 13 patients with ear symptoms were examined, and multisection 3-mm-thick 2D images and 30-mm-slab, 1-mm-section 3D images were compared qualitatively and quantitatively. Then, 3D MR cisternography was performed in 400 patients with ear symptoms, and qualitative evaluation was performed. RESULTS: In volunteers, the average peak velocity of CSF was 1.2 cm/s. With TE = 250, CSF may move an average of 3 mm, and can be washed out of a 3-mm-thick 2D section volume. The CSF signal relative to that of a water phantom decreased gradually as TE increased on single-section 3-mm-thick 2D images. The CSF signal relative to that of the water phantom increased gradually as section thickness increased. No significant differences were noted in intravoxel dephasing and amplitude of the section-selecting gradient. The contrast-to-noise ratio (CNR) between CSF and the cerebellar peduncle, and the visibility of the cranial nerves and vertebrobasilar artery were significantly improved on 3D images in 17 subjects. In images from 400 patients, no significant signal loss in the cistern was observed using 3D FSE. CONCLUSION: CSF signal loss in thin-section 2D MR cisternography is mainly attributable to the wash-out phenomenon. 3D acquisition can reduce this phenomenon and provide thinner sections. The scan time for 3D acquisition is not excessive when a long echo train length and half-Fourier imaging are used. MR cisternography should be performed using a 3D acquisition.

MR imaging of the inner ear: comparison of a three-dimensional fast spin-echo sequence with use of a dedicated quadrature-surface coil with a gadolinium-enhanced spoiled gradient-recalled sequence.

PURPOSE: To prospectively evaluate the sensitivity and specificity of magnetic resonance (MR) imaging in the inner ear with a long echo train, three-dimensional (3D), asymmetric Fourier-transform, fast spin-echo (SE) sequence with use of a dedicated quadrature-surface phased-array coil to detect vestibular schwannoma in the cerebellopontine angle and the internal auditory canal. MATERIALS AND METHODS: In 205 patients (410 ears) with ear symptoms, 1.5-T MR imaging was performed with unenhanced 3D asymmetric fast SE and gadolinium-enhanced 3D gradient-recalled (SPGR) sequences with use of a quadrature surface phased-array coil. The 3D asymmetric fast SE images were reviewed by two radiologists, with the gadolinium-enhanced 3D SPGR images used as the standard of reference. RESULTS: Nineteen lesions were detected in the 410 ears (diameter range, 2-30 mm; mean, 10.5 mm +/- 6.4 [standard deviation]; five lesions were smaller than 5 mm). With 3D asymmetric fast SE, sensitivity, specificity, and accuracy, respectively, were 100%, 99.5%, and 99.5% for observer 1 and 100%, 99.7%, and 99.8% for observer 2. CONCLUSION: The unenhanced 3D asymmetric fast SE sequence with a quadrature-surface phased-array coli allows the reliable detection of vestibular schwannoma in the cerebellopontine angle and internal auditory canal.

A novel MR angiography technique: SPEED acquisition using half-Fourier RARE.

A novel MR angiography (MRA) method, swap phase encode extended data (SPEED), was developed. Two one-shot images with the phase-encode directions swapped were collected within a single breath-hold period and processed with a maximum intensity projection (MIP) to obtain an image. In this study, a long echo train two-dimensional rapid acquisition with relaxation enhancement (RARE) sequence with half-Fourier (half-RARE) was used to obtain the pulmonary MRA images. The MIP image obtained using the SPEED technique presented promising results for pulmonary vessels.