[Microfocal prostate cancer: a clinicopathological analysis of 206 cases].

Objective: To investigate the clinical and pathological features and prognosis of patients with microfocal prostate adenocarcinoma. Methods: Clinical and pathological data of the patients diagnosed with microfocal adenocarcinoma on prostate biopsy at the West China Hospital from 2013 to 2019 were collected. Microfocal adenocarcinoma was defined as follows: Gleason score of 3+3=6, total number of the cores ≥10, number of the positive cores ≤2, and proportion of the tumor in each positive core<50%. Clinicopathological parameters, treatment plans and follow-up data were collected. Pathological information of the biopsy and radical resection specimens was used to analyze the correlation between pathological parameters in the biopsy report and adverse pathological features of radical resection specimens, including increased Gleason score, capsule invasion, positive surgical margin and perineural invasion. Results: A total of 206 cases of microfocal adenocarcinoma were diagnosed on prostate biopsies from 2013 to 2019, accounting for 6.7% of all adenocarcinoma cases. There were 139 cases of 1 positive core and 67 cases of 2 positive cores. Patients with microfocal adenocarcinoma were younger than those with non-microfocal adenocarcinoma (69 years versus 71 years, P<0.001). Compared with patients with non-microfocal adenocarcinoma, the pre-biopsy total prostate specific antigen (tPSA) and free prostate specific antigen (fPSA) levels in patients with microfocal adenocarcinoma were both lower (11.2 µg/L2 versus 23.7 µg/L2; 1.4 µg/L2 versus 3.0 µg/L2, P<0.001), the fPSA/tPSA level was higher (12.9% versus 10.7%, P<0.05), the prostate volume was larger (38.9 mL versus 34.3 mL, P<0.05), and the PSA density was lower (0.3 µg/L2 versus 0.8 µg/L2, P<0.001). 130 patients underwent radical prostatectomy, 30 patients chose active monitoring, 31 patients chose endocrine or radiation therapy, and 15 patients were lost to follow-up. Three patients in the active surveillance group underwent radical prostatectomy for disease progression after 21-39 months observation. Biochemical relapses occurred in two patients in the radical prostatectomy group. The remaining patients have no disease progression or recurrence at present. Compared with radical prostatectomy specimens, Gleason score in the biopsy material was increased in 64/115 patients (55.7%). Among resection excision specimens, 14 cases (12.2%) had extraprostatic extension (EPE), 35 cases (30.4%) had perineural invasion, and 16 cases (13.9%) had a positive margin. Univariate and multivariate analyses showed that low fPSA/tPSA ratio and 2 positive cores were independent risk factors for Gleason score increase in the radical prostatectomy specimens. A low fPSA/tPSA ratio was an independent risk factor for perineural invasion. Low fPSA/tPSA ratio and low prostate volume were associated with a positive margin in radical prostatectomy specimens. Conclusions: In this study, patients diagnosed with microfocal adenocarcinoma on prostate biopsy account for a high proportion of the patients with increased Gleason score in the radical prostatectomy specimens, and there is a certain proportion of adverse pathological features in the radical specimens. Therefore, for the patients with only a small amount of low-grade adenocarcinoma found in biopsy, PSA levels and PSA density should be taken into consideration in treatment selection.

Photoemission Spectroscopic Evidence for the Dirac Nodal Line in the Monoclinic Semimetal SrAs_{3}.

Topological nodal-line semimetals with exotic quantum properties are characterized by symmetry-protected line-contact bulk band crossings in the momentum space. However, in most of identified topological nodal-line compounds, these topological nontrivial nodal lines are enclosed by complicated topological trivial states at the Fermi energy (E_{F}), which would perplex their identification and hinder further applications. Utilizing angle-resolved photoemission spectroscopy and first-principles calculations, we provide compelling evidence for the existence of Dirac nodal-line fermions in the monoclinic semimetal SrAs_{3}, which possesses a simple nodal loop in the vicinity of E_{F} without the distraction from complicated trivial Fermi surfaces. Our calculations revealed that two bands with opposite parities were inverted around Y near E_{F}, resulting in the single nodal loop at the Γ-Y-S plane with a negligible spin-orbit coupling effect. The band crossings were tracked experimentally and the complete nodal loop was identified quantitatively, which provide a critical experimental support for the existence of nodal-line fermions in the CaP_{3} family of materials. Hosting simple topological nontrivial bulk electronic states around E_{F} and without complication from the trivial states, SrAs_{3} is expected to be a potential platform for topological quantum state investigation and applications.

The robustness of T2 value as a trabecular structural index at multiple spatial resolutions of 7 Tesla MRI.

PURPOSE: To evaluate the robustness of MR transverse relaxation times of trabecular bone from spin-echo and gradient-echo acquisitions at multiple spatial resolutions of 7 T. METHODS: The effects of MRI resolutions to T2 and T2* of trabecular bone were numerically evaluated by Monte Carlo simulations. T2 , T2*, and trabecular structural indices from multislice multi-echo and UTE acquisitions were measured in defatted human distal femoral condyles on a 7 T scanner. Reference structural indices were extracted from high-resolution microcomputed tomography images. For bovine knee trabecular samples with intact bone marrow, T2 and T2* were measured by degrading spatial resolutions on a 7 T system. RESULTS: In the defatted trabecular experiment, both T2 and T2* values showed strong ( |r| > 0.80) correlations with trabecular spacing and number, at a high spatial resolution of 125 µm3 . The correlations for MR image-segmentation-derived structural indices were significantly degraded ( |r| < 0.50) at spatial resolutions of 250 and 500 µm3 . The correlations for T2* rapidly dropped ( |r| < 0.50) at a spatial resolution of 500 µm3 , whereas those for T2 remained consistently high ( |r| > 0.85). In the bovine trabecular experiments with intact marrow, low-resolution (approximately 1 mm3 , 2 minutes) T2 values did not shorten ( |r| > 0.95 with respect to approximately 0.4 mm3 , 11 minutes) and maintained consistent correlations ( |r| > 0.70) with respect to trabecular spacing (turbo spin echo, 22.5 minutes). CONCLUSION: T2 measurements of trabeculae at 7 T are robust with degrading spatial resolution and may be preferable in assessing trabecular spacing index with reduced scan time, when high-resolution 3D micro-MRI is difficult to obtain.

OK-432 sclerotherapy of plunging ranula in 21 patients: it can be a substitute for surgery.

BACKGROUND AND PURPOSE: Although first-choice therapy for the ranula is surgery, this choice presents technical difficulties and frequent recurrences because of insufficient surgery. We evaluated the efficacy of OK-432 sclerosis of the plunging ranula as a substitute for surgery. METHODS: Twenty-one patients with plunging ranula were treated with intralesional injection of OK-432. The liquid content of the ranula was aspirated as much as possible, after which OK-432 solution was injected in the same volumes as that drawn out. Patients were followed on sonography or CT. RESULTS: Seven (33.3%) patients with plunging ranulas showed total shrinkage and resolution, and 4 (19%) patients showed near-total shrinkage (more than 90% of the volume). Four (19%) patients revealed marked shrinkage (more than 70% of the volume), and 3 (14.3%) patients showed partial shrinkage (less than 70% of the volume). Three (14.3%) patients showed recurrence after total shrinkage 1 month after injection. The overall recurrence rate after each injection was 47% (16 of 34 injections in 21 patients), but the recurrence rate after the last sclerotherapy was only 14%. There were no serious side effects except for fever lasting 2-3 days (12 patients) and swelling (10 patients) for 3-5 days. Mild odynophagia for 1-2 days was also noted in 7 patients, and there was 1 severe case of odynophagia. CONCLUSION: OK-432 sclerotherapy of plunging ranula is a safe and potentially curative procedure that may be used as a primary treatment for plunging ranula before considering surgery.

Sodium nitroprusside enhances TRAIL-induced apoptosis via a mitochondria-dependent pathway in human colorectal carcinoma CX-1 cells.

The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL, Apo-2L) is a recently characterized member of the family of programmed cell death-inducing ligands that includes TNF-alpha and CD95L (FasL). It is well known that TRAIL binds to the death signaling receptors, DR4 and DR5, and initiates the TRAIL death pathway. Activation of this pathway, mediated through a caspase cascade, causes apoptosis. In this study, we hypothesized that oxidative stress facilitates TRAIL-induced apoptosis by promoting caspase activity through cytochrome c release from mitochondria. Human colorectal carcinoma CX-1 cells were treated with various concentrations of TRAIL (12.5-200 ng/ml) and/or sodium nitroprusside (SNP; 0.03-1 mM) for 12 h. SNP, a nitric oxide donor, which had little toxic effect by itself, enhanced TRAIL-induced cytotoxicity. For example, TRAIL-induced apoptosis (200 ng/ml) was increased by a factor of 2.5-fold in the presence of 1 mM SNP. The combined treatment also caused an increase in cytochrome c release, caspase-3 activity, and PARP cleavage. Overexpression of Bcl-2 completely blocked the SNP-promoting effects, but only moderately inhibited TRAIL-induced apoptosis. Similar results were observed in the presence of hydrogen peroxide or peroxynitrite. Taken together, the present studies suggest that SNP enhances TRAIL-induced cytotoxicity by facilitating the mitochondria-mediated caspase signal transduction pathway.

Free liposomes enhance the transfection activity of DNA/lipid complexes in vivo by intravenous administration.

Factors that regulate the transfection efficiency of cationic lipid-based carriers are still largely unknown. We have shown in a previous report [F. Liu, H.W. Qi, L. Huang, D. Liu, Factors controlling the efficiency of cationic lipid-mediated transfection in vivo via intravenous administration, Gene Ther., 4 (1997) 517-523. ] that the transfection efficiency, to the lung, of a lipid formulation composed of N-[1-(2,3-dioleoyloxy)propyl-N,N, N-trimethylammonium chloride (DOTMA) and Tween 80 is directly proportional to the ratio of DOTMA to DNA. In this study, we investigated the mechanism underlying the high cationic lipid to DNA ratio dependent transfection activity. Specifically, we have examined the role of free cationic liposomes in affecting the transfection efficiency of the DNA/lipid complexes in vivo by intravenous administration. The data show that greater transfection activity of DNA/lipid complexes in the lung at a higher cationic lipid to DNA ratio is due to the function of free liposomes present in the DNA/lipid mixture. Free liposomes enhance the transfection activity of DNA/lipid complexes by increasing the retention time of DNA and decreasing transgene degradation in different organs. In addition to DOTMA liposomes, liposomes composed of 1,2-dioleoyl-3-trimethylammonium propane chloride (DOTAP) and 3beta[N-(N', N'-dimethylaminoethane) carbamoyl] cholesterol (DC-Chol) also enhance the level of gene expression in animals transfected by DNA/DOTMA complexes. These results suggest that inclusion of free liposomes into the DNA/lipid complexes may be important in achieving an optimal transfection activity in vivo.

Liposome clearance from blood: different animal species have different mechanisms.

The kinetics of blood clearance and the mechanisms of liposome uptake by the reticuloendothelial system (RES) were compared in two animal species (mice and rats). By employing an in situ liver perfusion technique with selected liposome compositions (PC/Chol, PC/Cho/PS, PC/Chol/GM1 and PC/Chol/PEG5000-PE), we demonstrated that liposomes with same lipid composition exhibited different blood circulation half-lives in different animal species. Although liver is the major organ responsible for the clearance of liposomes from blood in both animal species, the specific mechanisms differ. In mice, liposome uptake by the liver did not involve specific serum opsonins. In contrast, liposome uptake by the rat liver was strongly dependent on serum opsonins. Further, the activity of serum opsonins for a given liposome composition differed among animal species. Human serum exhibited higher opsonin activities for PC/Chol and PC/Chol/GM1 liposomes than bovine sera, while rat serum displayed a high opsonizing activity for GM1 liposomes and none for liposomes composed of PC and Chol. The opsonin activity of human serum could be removed or decreased by treatment with EGTA/Mg2+, EDTA or cobra venom factor, suggesting that the activity is likely due to complement components. It is likely that C3 of the human complement system plays an important role in mediating the uptake of liposomes by the liver.

Recognition and clearance of liposomes containing phosphatidylserine are mediated by serum opsonin.

Liver uptake of liposomes containing phosphatidylserine was studied in a single pass liver perfusion system and found to be serum dependent. The effectiveness of serum in mediating liposome uptake by the liver depends on liposomes size. Large liposomes appeared to be opsonized more efficiently and, therefore, taken up more by the liver than the smaller ones. The effects of liposomes size on liver uptake did not occur in the absence of serum. Treatment of serum at 56 degrees C for 30 min abolished the serum activity, suggesting the involvement of complement components. Inhibition of the hemolytic activity of complement through the alternative pathway by PS-containing liposomes suggests that components in this pathway are responsible for liposome opsonization. Liposomes containing phosphatidic acid, phosphatidylglycerol, and dicetyl phosphate compete in different degrees for serum components which mediate the liver uptake of PS-containing liposomes. These results suggest that the opsonization of liposomes by serum opsonins are the determining factors for the recognition and clearance of liposomes by the RES. Complement components are most likely involved in this process. The results presented here are relevant to the use of liposomes as drug delivery vehicle in vivo and to the PS-mediated clearance of red blood cells from the blood circulation.

Effects of SCN- and NO3- on organic anion transport in rabbit kidney cortical slices.

1. The effects of replacement of Cl- by either SCN- or NO3- on the accumulation of p-aminohippurate, the efflux of pre-accumulated p-amino-hippurate and kinetics of p-aminohippurate uptake were investigated in the rabbit kidney cortical slice. 2. The total replacement of Cl- in the incubation medium with SCN- decreased the 60-min slice-to-medium concentration ratio (S/M) of p-amino-hippurate by 75% and that with NO3- by 40%. 3. The decrease in p-aminohippurate accumulation by the inorganic ions was found to be specific for organic anion transport since the uptake of the organic cation, tetraethylammonium, was not influenced by inorganic ions. 4. The influence of NO3- on p-aminohippurate uptake was fully reversible: however, the effect of SCN- could only be partially reversed. 5. Both SCN- and NO3- significantly increased the Km value but had no significant effect on the V value of the p-aminohippurate uptake process. 6. These findings suggest that both SCN- and NO3- are competitive inhibitors of p-aminohippurate transport and, also, that SCN- appears to bind to a membrane component involved in the transport of p-aminohippurate.

Characterization of cationic liposome-mediated gene transfer in vivo by intravenous administration.

Physicochemical properties of the cationic liposomes, including structure of the cationic lipid-to-DNA ratio, liposome particle size, and inclusion of the helper lipids, were studied for their effect on the level, site, and duration time of gene expression in vivo by intravenous administration. Using a cytomegalovirus (CMV)-driven gene expression system containing either the luciferase or green fluorescence protein gene as a reporter and two cationic lipids [N-(2,3-dioleoyloxy)propyl-N,N,N-trimethylammonium chloride (DOTMA) and 1,2-dioleoyloxy-3-trimethylammonium propane (DOTAP)], we demonstrated in vivo by a single intravenous injection of DNA/liposome complexes into mice, that cationic liposomes are capable of transfecting cells in organs such as the lung, heart, liver, spleen, and kidney. Transfection efficiency is determined mainly by the structure of the cationic lipid and the ratio of cationic lipid to DNA. Although the presence of cholesterol in DOTAP liposomes did not affect transfection activity, inclusion of dioleoylphosphatidylethanolamine (DOPE) into either DOTAP or DOTMA liposomes significantly decreases liposome transfection activity in vivo. Results form time course show that gene expression in different organs is transient, with a peak level between 4 and 24 hr, dropping to less than 1% of the peak level by day 4. Experiments with repeated injections showed that the peak level of gene expression could be regained by subsequent injection.

Synthesis and characterization of aromatic ring-based cationic lipids for gene delivery in vitro and in vivo.

A new series of cationic lipids has been synthesized for gene delivery using 3,5-dihydroxybenzyl alcohol as the backbone and starting material. Using CMV driven expression system and luciferase gene as a reporter, we demonstrated that the transfection activity of these new lipids when formulated with Tween 80 as co-lipid is comparable to that of DOTAP, one of the most commonly used cationic lipids for transfection. Among the four different cell lines tested including murine melanoma BL-6 cells, human embryonic kidney 293 cells, HepG2 and HeLa cells, the highest transgene expression was seen in 293 cells. Results from in vivo experiments using mice as an animal model show that these cationic lipids preferentially transfect the cells in the lung upon tail vein administration. The cationic lipid, N,N,N-trimethyl-N-[3,5-bis(tetradecyloxy)benzyl] ammonium bromide 4c(di-C14:0) with two 14-hydrocarbon chains exhibits the best transfection activity. These results suggest that these new aromatic ring-based cationic lipids are useful transfection reagents for both in vitro and in vivo gene transfer studies.

Lower gastrointestinal bleeding due to cytomegalovirus ileal ulcers in an immunocompetent man.

Cytomegalovirus (CMV) infections are commonly reported in severely immunocompromised hosts and ulcers of the alimentary tract are frequently observed in systemic CMV infections. However, invasive and ulcerative disease of the gastrointestinal (GI) tract caused by CMV has also been reported in healthy adults. Many reports show that a CMV infection can produce localized ulcerations in the esophagus, stomach, small intestine, and colon in nonimmunocompromised individuals. The most common site of involvement by CMV infection in the GI tract is the colon followed by the upper GI tract and the least common site is the small intestine. Although GI bleeding is one of the major presenting symptoms of patients with CMV infections of the GI tract, lower GI bleeding due to CMV ileal ulcers in immunocompetent patients, to our knowledge, has not been reported in the English literature. Recently, we experienced a case of lower GI bleeding due to CMV ileal ulcers in a 57-year-old man who had no evidence of immunocompromise. This case suggests that small intestinal ulcers due to CMV infection should be included in the differential diagnosis of lower GI bleeding even in immunocompetent hosts.

Comparison of incidence of gastroesophageal reflux and regurgitation associated with timing of removal of the laryngeal mask airway: on appearance of signs of rejection versus after recovery of consciousness.

STUDY OBJECTIVES: To compare the incidence of gastroesophageal reflux and regurgitation associated with laryngeal mask airway (LMA) removal when signs of rejecting the LMA, such as swallowing, struggling, and restlessness, were observed and when the patient could open his or her mouth on command. DESIGN: Randomized clinical trial. SETTING: Operating room and recovery room of a tertiary care referral hospital. PATIENTS: 63 ASA physical status I and II adult patients scheduled for elective orthopedic surgery. INTERVENTIONS: Using a standardized general anesthetic technique, patients were allocated randomly to Group A (n = 34; LMA removed when signs of rejection, such as swallowing, struggling, and restlessness, were observed) or Group B (n = 29; LMA removed when the patient could open his or her mouth on command). MEASUREMENTS AND MAIN RESULTS: To detect gastroesophageal reflux throughout anesthesia, a pH monitoring probe was positioned in the lower esophagus on the day before surgery. To assess regurgitation during emergence, a gelatin capsule of methylene blue (50 mg) was swallowed prior to induction. At the end of anesthesia, episodes of reflux and regurgitation of gastric contents were analyzed/determined by pH below 4 and bluish staining of the pharynx and/or LMA, respectively. Physical events such as bucking, straining, and coughing during the arousal phase were recorded in both groups by an independent observer. The incidence of reflux (pH < 4) from the time of the appearance of rejection signs to LMA removal and the total incidence of reflux in Group B were significantly higher than in Group A (p < 0.05). Staining of the LMA and the pharynx by methylene blue was not observed in patients from either experimental group. The number of physical events in Group B during the arousal phase was significantly increased compared to Group A (p < 0.05). Considering all patients in Group A and Group B, physical events were associated with the occurrence of reflux (p < 0.05). Desaturation (SpO2 < 95%) and clinical evidence of aspiration of gastric contents did not occur in either group. CONCLUSION: Maintenance of the LMA until the patient can open his or her mouth on command increases the incidence of gastroesophageal reflux.

Antibody mediated lung targeting of long-circulating emulsions.

Monoclonal antibody 34A, which specifically binds to a surface glycoprotein (thrombomodulin) of the pulmonary endothelial cell surface in mice, has been conjugated to the surface of long-circulating emulsions composed of Castor oil, phosphatidylcholine and polyethylene glycol coupled to distearoylphosphatidyl-ethanolamine. These antibody-containing emulsions were found capable of binding to the lung when injected into mice through the tail vein. The level of lung accumulation of these emulsions depends on the amount of antibodies conjugated to the surface of the emulsions. With an input antibody to lipid ratio of 2:1 (w/w), 30% injected emulsions were found in the lung 30 minutes after administration. Such high level accumulation can be blocked by co-administration of free 34A antibody, indicating that the binding is specific and 34A antibody mediated. Kinetic studies showed that emulsion targeting to the lung was very rapid. Five minutes after tail vein injection, the total amount of emulsion found in the lung was the highest among the time points examined, indicating the completion of lung binding. However, about 50% of the initially bound emulsions remained bound for more than 4 hours. These results indicate that the targeted drug delivery using oil-in-water emulsions could be very useful to enhance the therapeutic efficacy of lipophilic drugs.

[Experimental study of pathogenic effects of dusts of vanad-titan-magnetite on rats lungs].

The present study is concerned with the pulmonary pathological changes in the rats following intra-tracheal administration of sintering dust and vanadium slag separately. The results indicated that both the volume of lungs and the quantity of pulmonary collagen protein in the treated groups were higher than those in the control groups. The histopathological observations revealed foci of dust cells and fibers in the pulmonary alveoli, bronchi and around the blood vessels, a small amount of reticular fibers and collagenous fibers were also seen. At the same time bronchitis, pulmonary emphysema and atelectasis can also be seen. The pathological changes in the vanadium slag groups were more distinct than those in the sintering dust groups. The paper briefly discussed these pathological changes from the standpoint of the chemical composition of the dusts, dose-response relation, etc.

Ultrafast 3D spin-echo acquisition improves Gadolinium-enhanced MRI signal contrast enhancement.

Long scan times of 3D volumetric MR acquisitions usually necessitate ultrafast in vivo gradient-echo acquisitions, which are intrinsically susceptible to magnetic field inhomogeneities. This is especially problematic for contrast-enhanced (CE)-MRI applications, where non-negligible T2* effect of contrast agent deteriorates the positive signal contrast and limits the available range of MR acquisition parameters and injection doses. To overcome these shortcomings without degrading temporal resolution, ultrafast spin-echo acquisitions were implemented. Specifically, a multiplicative acceleration factor from multiple spin echoes (×32) and compressed sensing (CS) sampling (×8) allowed highly-accelerated 3D Multiple-Modulation-Multiple-Echo (MMME) acquisition. At the same time, the CE-MRI of kidney with Gd-DOTA showed significantly improved signal enhancement for CS-MMME acquisitions (×7) over that of corresponding FLASH acquisitions (×2). Increased positive contrast enhancement and highly accelerated acquisition of extended volume with reduced RF irradiations will be beneficial for oncological and nephrological applications, in which the accurate in vivo 3D quantification of contrast agent concentration is necessary with high temporal resolution.

Relative bioavailability of two 5-mg montelukast sodium chewable tablets: a single dose, randomized, open-label, 2-period crossover comparison in healthy korean adult male volunteers.

Montelukast sodium, cysteinyl leukotriene receptor 1 specific antagonist, has been marketed in Korea for the treatment of bronchial asthma and allergic rhinitis. The aim of this study was to compare the pharmacokinetics and relative bioavailability of a test and reference formulation of montelukast 5-mg chewable tablets in healthy Korean male volunteers to meet KFDA regulatory criteria for marketing of the new generic formulation. This study was designed as a single-dose, 2-treatment, and 2-period crossover trial with 32 healthy volunteers. Each subject was randomly assigned to receive the test (Dong-Kook Montelukast Sodium Chewable Tablet 5 mg®) or reference (Singulair Chewable Tablet 5 mg®) formulation. The tablet was chewed 20 times, and then swallowed with 240 mL of water. Plasma concentrations of montelukast up to 24 h after the dose were determined using a validated UPLC-MS/MS method, and the bioequivalence between the 2 formulations was assessed by statistical analysis of mean ratios of log-transformed AUC0-24 h and Cmax. No period or sequence effects were detected. The AUC0-24 h was 1 835 ng·h/mL for the test formulation, and 1 930 ng·h/mL for the reference formulation. The respective values of AUC0-∞ were 1 917 and 2 015 ng·h/mL. The Cmax of the test and reference products (247 and 283 ng/mL, respectively) reached at 2.25 and 2.72 h, respectively. Then, they gradually decreased with the mean terminal t1/2 of 5.25 and 5.30 h for the test and reference products, respectively. The 90% CIs for the ratio of log-transformed AUC0-24 h and Cmax for the test and reference formulations were 0.92-0.99 and 0.83-0.91, respectively. No adverse events were reported in this study. This single dose study found that the test and reference products met the regulatory criteria for bioequivalence in these fasting healthy Korean male volunteers.

Magnetic field anisotropy based MR tractography.

Non-invasive measurements of structural orientation provide unique information regarding the connectivity and functionality of fiber materials. In the present study, we use a capillary model to demonstrate that the direction of fiber structure can be obtained from susceptibility-induced magnetic field anisotropy. The interference pattern between internal and external magnetic field gradients carries the signature of the underlying anisotropic structure and can be measured by MRI-based water diffusion measurements. Through both numerical simulation and experiments, we found that this technique can determine the capillary orientation within 3°. Therefore, susceptibility-induced magnetic field anisotropy may be useful for an alternative tractography method when diffusion anisotropy is small at higher magnetic field strength without the need to rotate the subject inside the scanner.