Faculty Bibliography

BACKGROUND:Susceptibility weighted imaging (SWI) combines phase with magnitude information to better image sub-voxel veins. Recently, it has been extended to image very small sub-voxel arteries and veins by injecting intravenously the ultra-small superparamagnetic iron oxide, Ferumoxytol. OBJECTIVE:To determine practical experimental imaging parameters for sub-voxel cerebral vessels at 7 T. METHODS:(30 min) were used. Both SWI and quantitative susceptibility mapping (QSM) data were analyzed. Contrast-to-noise ratio (CNR) was measured and used to determine the optimal practical imaging parameters for detection of small cortical penetrating arteries. RESULTS:For a given spatial resolution with an aspect ratio (frequency: phase: slice) of 2:4:8 relative to the vessel size, we found the TE-dose index (TE x dose) must be at least 40 ms·mg/kg for both SWI and QSM to reveal the most vessels. The higher the TE-dose index, the better the image quality for both SWI and QSM up to 60 ms·mg/kg. CONCLUSIONS:There is an optimal TE-dose index for improved visualization of sub-voxel vessels. Choosing the smallest TE and the largest allowed dose made it possible to run the sequence efficiently. In practice, the aspect ratio of 2:4:8 and the TE-dose index ranging from 40 to 60 ms·mg/kg provided the optimal and most practical solution.

H MRI maps brain anatomy and pathology non-invasively through contrasts generated by exploiting inhomogeneities in tissue micro-environments. Inferring histopathological information from MRI findings, however, remains challenging due to the absence of direct links between MRI signals and specific tissue compartments. Here, we show that convolutional neural networks, developed using co-registered multi-contrast MRI and histological data of the mouse brain, can generate virtual histology from MRI results. Our networks provide maps that mirror histological stains for axons and myelin with enhanced specificity compared to existing MRI markers. Furthermore, by introducing random perturbations to the inputs, the relative contribution of each MRI contrast within the networks can be estimated and guide the optimization of MRI acquisition. We anticipate our method to be a starting point for translation of MRI results into easy-to-understand virtual histology for neurobiologists and provide resources for developing novel MRI contrasts

Objective: To establish a microbial limit test method for compound miconazole nitrate ointment.
Method(s): According to the Pharmacopoeia of the People's Republic of China and considering the physical and chemical characteristics of the ointment,the test product was treated by isopropyl tetradecanoate and bacteria free sodium chloride (pH 7. 0)-peptone buffer which contained 10% poly sorbitate 80, and the membrane filtration method was applied in microbial count test. At the same time,the control bacteria of Pseudomonasaeruginosa was detected by routine method, and the control bacteria of Staphylococcus aureus was tested by the culture medium dilution method combined with membrane filtration method.
Result(s):In the microbial counting part, each test bacterium was 0. 5-2. At the same time,the control bacteria of Pseudomonas aeruginosa could be detected by routine method and the control bacteria of Staphylococcus aureus could be tested by the culture medium dilution method combined with the membrane filtration method.
Conclusion(s): Appropriate pretreatment methods for test products might thoroughly remove the antibacterial properties of ointment and solve the problem of difficult filtering of samples. This method is reliable for microbial limit test.
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Background and Purpose: Susceptibility-weighted imaging (SWI) has emerged as a useful clinical tool in many neurological diseases including multiple sclerosis (MS). This study aims to investigate the relationship between SWI signal changes due to iron deposition in MS lesions and tissue blood perfusion and microstructural abnormalities to better understand their underlying histopathologies. Methods: Forty-six patients with relapsing remitting MS were recruited for this study. Conventional FLAIR, pre- and post-contrast T1-weighted imaging, SWI, diffusion tensor imaging (DTI), and dynamic susceptibility contrast (DSC) perfusion MRI were performed in these patients at 3T. The SWI was processed using both magnitude and phase information with one slice minimal intensity projection (mIP) and phase multiplication factor of 4. MS lesions were classified into 3 types based on their lesional signal appearance on SWI mIP relative to perilesional normal appearing white matter (peri-NAWM): Type-1: hypointense, Type-2: isointense, and Type-3: hyperintense lesions. The DTI and DSC MRI data were processed offline to generate DTI-derived mean diffusivity (MD) and fractional anisotropy (FA) maps, as well as DSC-derived cerebral blood flow (CBF) and cerebral blood volume (CBV) maps. Comparisons of diffusion and perfusion measurements between lesions and peri-NAWM, as well between different types of lesions, were performed. Results: A total of 137 lesions were identified on FLAIR in these patients that include 40 Type-1, 46 Type-2, and 51 Type-3 lesions according to their SWI intensity relative to peri-NAWM. All lesion types showed significant higher MD and lower FA compared to their peri-NAWM (P < 0.0001). Compared to Type-1 lesions (likely represent iron deposition), Type-2 lesions had significantly higher MD and lower FA (P < 0.001) as well as lower perfusion measurements (P < 0.05), while Type 3 lesions had significantly higher perfusion (P < 0.001) and lower FA (P < 0.05). Compared to Type-2, Type-3 lesions had higher perfusion (P < 0.0001) and marginally higher MD and lower FA (P < 0.05). Conclusion: The significant differences in diffusion and perfusion MRI metrics associated with MS lesions, that appear with different signal appearance on SWI, may help to identify the underlying destructive pathways of myelin and axons and their evolution related to inflammatory activities.

PURPOSE/OBJECTIVE:Many brain diseases are associated with an alteration in blood-brain barrier (BBB) and its permeability. Current methods using contrast agent are primarily sensitive to major leakage of BBB to macromolecules, but may not detect subtle changes in BBB permeability. The present study aims to develop a novel non-contrast MRI technique for the assessment of BBB permeability to water. METHODS:The central principle is that by measuring arterially labeled blood spins that are drained into cerebral veins, water extraction fraction (E) and permeability-surface-area product (PS) of BBB can be determined. Four studies were performed. We first demonstrated the proof-of-principle using conventional ASL with very long post-labeling delays (PLD). Next, a new sequence, dubbed water-extraction-with-phase-contrast-arterial-spin-tagging (WEPCAST), and its Look-Locker (LL) version were developed. Finally, we demonstrated that the sensitivity of the technique can be significantly enhanced by acquiring the data under mild hypercapnia. RESULTS:By combining a strong background suppression with long PLDs (2500-4500 ms), ASL spins were reliably detected in the superior sagittal sinus (SSS), demonstrating the feasibility of measuring this signal. The WEPCAST sequence eliminated partial voluming effects of tissue perfusion and allowed quantitative estimation of E = 95.5 ± 1.1% and PS = 188.9 ± 13.4 mL/100 g/min, which were in good agreement with literature reports. LL-WEPCAST sequence shortened the scan time from 19 min to 5 min while providing results consistent with multiple single-PLD acquisitions. Mild hypercapnia increased SNR by 78 ± 25% without causing a discomfort in participants. CONCLUSION/CONCLUSIONS:A new non-contrast technique for the assessment of global BBB permeability was developed, which may have important clinical applications.

PURPOSE/OBJECTIVE:To investigate the feasibility of measuring the subtle disruption of blood-brain barrier (BBB) using DCE-MRI with a scan duration shorter than 10 min. METHODS:) in the estimation of vascular permeability-surface area product (PS). Numerical simulation studies were carried out to investigate how the reduction in scan time affects the accuracy in estimating contrast kinetic parameters. DCE-MRI studies of the rat brain were conducted with Fisher rats to confirm the results from the simulation. Intracranial F98 glioblastoma models were used to assess areas with different levels of permeability. In the normal brain tissues, the Patlak model (PM) and EPM were compared, whereas the 2-compartment-exchange-model (TCM) and EPM were assessed in the peri-tumor and the tumor regions. RESULTS:was high as in the gray matter, the bias in PM-PS (>900%) were larger than that in EPM-PS (<42%). The animal study also showed similar results, where the PM parameters were more sensitive to the scan duration than the EPM parameters. It was also demonstrated that, in the peri-tumor region, the EPM parameters showed less change by scan duration than the TCM parameters. CONCLUSION/CONCLUSIONS:The results of this study suggest that EPM can be used to measure PS with a scan duration of 10 min or less.

PURPOSE: To demonstrate the potential of imaging cerebral arteries and veins with ferumoxytol using susceptibility weighted imaging (SWI) and quantitative susceptibility mapping (QSM). MATERIALS AND METHODS: The relationships between ferumoxytol concentration and the apparent susceptibility at 1.5T, 3T, and 7T were determined using phantom data; the ability of visualizing subvoxel vessels was evaluated using simulations; and the feasibility of using ferumoxytol to enhance the visibility of small vessels was confirmed in three healthy volunteers at 7T(with doses 1 mg/kg to 4 mg/kg). The visualization of the lenticulostriate arteries and the medullary veins was assessed by two raters and the contrast-to-noise ratios (CNRs) of these vessels were measured. RESULTS: The relationship between ferumoxytol concentration and susceptibility was linear with a slope 13.3 +/- 0.2 ppm.mg-1 .mL at 7T. Simulations showed that SWI data with an increased dose of ferumoxytol, higher echo time (TE), and higher imaging resolution improved the detection of smaller vessels. With 4 mg/kg ferumoxytol, voxel aspect ratio = 1:8, TE = 10 ms, the diameter of the smallest detectable artery was approximately 50mum. The rating score for arteries was improved from 1.5 +/- 0.5 (precontrast) to 3.0 +/- 0.0 (post-4 mg/kg) in the in vivo data and the apparent susceptibilities of the arteries (0.65 +/- 0.02 ppm at 4 mg/kg) agreed well with the expected susceptibility (0.71 +/- 0.05 ppm). CONCLUSION: The CNR for cerebral vessels with ferumoxytol can be enhanced using SWI, and the apparent susceptibilities of the arteries can be reliably quantified using QSM. This approach improves the imaging of the entire vascular system outside the capillaries and may be valuable for a variety of neurodegenerative diseases which involve the microvasculature. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017.