Comparison of apparent diffusion coefficient (ADC) values obtained by echo planar imaging diffusion-weighted imaging (DWI) and radial acquisition regime DWI in low field MRI systems: A phantom study.

INTRODUCTION: Diffusion-weighted imaging (DWI) with radial acquisition regime (RADAR; RADAR-DWI) is a fast spin echo (FSE)-based DWI imaging technique that is known to be robust to magnetic susceptibility artifacts and distortions as compared with echo planar imaging DWI (EPI-DWI). Several reports have suggested that the apparent diffusion coefficient (ADC) values obtained with FSE-based DWI are different from those obtained with EPI-DWI. The purpose of this study was to create phantoms that mimic the T2 and ADC values of various tissues and to demonstrate the ADC values obtained with RADAR-DWI and EPI-DWI in low-field magnetic resonance imaging (MRI) systems. METHODS: Several phantoms were created using sucrose and manganese (II) chloride tetrahydrate mimicking various tissues. RADAR-DWI and EPI-DWI were used to scan the phantoms, and the obtained ADC values were compared. RESULTS: The ADC values obtained with RADAR-DWI were significantly higher than those obtained with EPI-DWI for all phantoms (P < 0.05). The ADC values obtained by RADAR-DWI ranged from 0.70 ± 0.01 to 1.21 ± 0.02 ( × 10-3mm2s-1). Meanwhile, the ADC values obtained with EPI-DWI ranged from 0.59 ± 0.01 to 1.08 ± 0.05 ( × 10-3mm2s-1). CONCLUSIONS: We created phantoms mimicking T2 and ADC values of various tissues and demonstrated the differences in ADC values obtained with RADAR-DWI and EPI-DWI using low-field MRI systems. IMPLICATIONS FOR PRACTICE: ADC values obtained by RADAR-DWI are significantly higher than those obtained by EPI-DWI, with different cutoff values for various tumor malignancies between them.

Technical Note: Novel imaging method to obtain gray matter-attenuated inversion recovery image using low-field magnetic resonance imaging systems.

INTRODUCTION: The double inversion recovery (DIR) technique suppresses two types of tissue signals with different T1 values by applying two inversion recovery (IR) pulses with different inversion times (TI). In contrast, the double tissue suppression with multi-echo acquisition and single TI combining HIRE (DOMUST-HIRE) method, is a technique enabling the white-matter-attenuated inversion recovery (WAIR) images by setting one inversion time (TI) in a sequence based on the multi-echo method and subtracting the second echo image from the first echo image. Here, we propose a new sequence that can provide the gray-matter-attenuated inversion recovery image based on the DOMUST-HIRE method. METHODS: In this small clinical study, we performed determination of optimal TI and physical evaluation by imaging a subject's head with T1WI and our proposed method for GAIR images. RESULTS: Our proposed method could increase the contrast ratio and the contrast-to-noise ratio between white matter (WM) and gray matter (GM), whereas the signal-to-noise ratio WM and GM decreased than with T1WI method. CONCLUSIONS: Our proposed method can be used to suppress GM and CSF signals. IMPLICATIONS FOR PRACTICE: The use of our proposed method in low-field MRI systems could provide GAIR image.

Feasibility of salt pads to improve fat suppression in low-field MRI systems.

INTRODUCTION: Fat-suppressed images are essential in clinical practice but are often affected by magnetic field inhomogeneity, resulting in poor image quality. We hypothesized that salt (99% sodium chloride [NaCl]) could be used as a magnetic field uniformity assist pad and verified whether salt pads improve magnetic field uniformity and the fat suppression effect in low-field magnetic resonance imaging (MRI) systems. METHODS: We conducted a small clinical study where coronal 2D fast spin-echo T2-weighted MRI with fat suppression was performed. The subjects were 10 healthy volunteers (six men and four women) with no surgical history, with a mean age of 20.5 years (range, 20-30 years). In the clinical study, we performed physical and visual evaluation by imaging a subject's knee with and without salt pads. RESULTS: The results of the clinical study indicated that the use of salt pads improved the magnetic field uniformity, thus increasing the fat suppression effect. CONCLUSIONS: Salt pads improved the homogeneity of the magnetic field and the fat suppression effect in low-field MRI systems. IMPLICATIONS FOR PRACTICE: The use of salt pads in low-field MRI systems could provide more accurate fat suppression images.

Identification of large variation in the photosynthetic induction response among 37 soybean [Glycine max (L.) Merr.] genotypes that is not correlated with steady-state photosynthetic capacity.

Irradiance continuously fluctuates during the day in the field. The speed of the induction response of photosynthesis in high light affects the cumulative carbon gain of the plant and could impact growth and yield. The photosynthetic induction response and its relationship with the photosynthetic capacity under steady-state conditions (P max) were evaluated in 37 diverse soybean [Glycine max (L.) Merr.] genotypes. The induction response of leaf photosynthesis showed large variation among the soybean genotypes. After 5 min illumination with strong light, genotype NAM23 had the highest leaf photosynthetic rate of 33.8 µmol CO2 m-2 s-1, while genotype NAM12 showed the lowest rate at 4.7 µmol CO2 m-2 s-1. Cumulative CO2 fixation (CCF) during the first 5 min of high light exposure ranged from 5.5 mmol CO2 m-2 for NAM23 to 0.81 mmol CO2 m-2 for NAM12. The difference in the induction response among genotypes was consistent throughout the growth season. However, there was no significant correlation between CCF and P max among genotypes suggesting that different mechanisms regulate P max and the induction response. The observed variation in the induction response was mainly attributed to ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activation, but soybean lines differing in the induction response did not differ in the leaf content of Rubisco activase α- and ß-proteins. Future studies will be focused on identifying molecular determinants of the photosynthetic induction response and determining whether this trait could be an important breeding target to achieve improved growth of soybeans in the field.

Fiber-optic magnetometry with randomly oriented spins.

We demonstrate fiber-optic magnetometry using a random ensemble of nitrogen-vacancy (NV) centers in nanodiamond coupled to a tapered optical fiber, which provides a waveguide delivery of optical fields for the initialization, polarization, and readout of the electron spin in NV centers.

Nuclear magnetization in gallium arsenide quantum dots at zero magnetic field.

Optical and electrical control of the nuclear spin system allows enhancing the sensitivity of NMR applications and spin-based information storage and processing. Dynamic nuclear polarization in semiconductors is commonly achieved in the presence of a stabilizing external magnetic field. Here we report efficient optical pumping of nuclear spins at zero magnetic field in strain-free GaAs quantum dots. The strong interaction of a single, optically injected electron spin with the nuclear spins acts as a stabilizing, effective magnetic field (Knight field) on the nuclei. We optically tune the Knight field amplitude and direction. In combination with a small transverse magnetic field, we are able to control the longitudinal and transverse components of the nuclear spin polarization in the absence of lattice strain--that is, in dots with strongly reduced static nuclear quadrupole effects, as reproduced by our model calculations.

Dark-bright mixing of interband transitions in symmetric semiconductor quantum dots.

In photoluminescence spectra of symmetric [111] grown GaAs/AlGaAs quantum dots in longitudinal magnetic fields applied along the growth axis, we observe in addition to the expected bright states also nominally dark transitions for both charged and neutral excitons. We uncover a strongly nonmonotonic, sign-changing field dependence of the bright neutral exciton splitting resulting from the interplay between exchange and Zeeman effects. Our theory shows quantitatively that these surprising experimental results are due to magnetic-field-induced ±3/2 heavy-hole mixing, an inherent property of systems with C(3v) point-group symmetry.

Lasing in ultra-narrow emission from GaAs quantum dots coupled with a two-dimensional layer.

We report electrically injected lasing in GaAs quantum dots (QDs) grown on GaAs(001) by droplet epitaxy. High-quality GaAs QDs with superior uniformity are formed using improved growth techniques involving the insertion of a two-dimensional layer, control of the As flux for GaAs crystallization, and thin AlGaAs layer capping with high-temperature annealing. The QDs show ultra-narrow luminescence with a linewidth of 20 meV. Ground-state lasing from a laser diode containing fivefold-stacked QD layers is observed at low temperature under pulsed operation.

Ultra-narrow emission from single GaAs self-assembled quantum dots grown by droplet epitaxy.

We realized ultra-narrow excitonic emission from single GaAs/AlGaAs quantum dots (QDs) grown by a refined droplet epitaxy technique. We found that uncapped quantum dots can be annealed at 400 degrees C without major changes in their morphology, thus enabling an AlGaAs capping layer to be grown at that temperature. Consequently, we demonstrate a fourfold reduction of the linewidth of the emission together with an increased recombination lifetime, compared to the conventional droplet epitaxial QDs. The averaged linewidth of neutral excitons measured by micro-photoluminescence on single quantum dots was around 35 microeV.

Light propagation from a fluorescent particle embedded in a photonic cluster of micrometer-sized dielectric spheres.

In self-assembled multilayer arrays of micrometer-sized spheres that include small amounts of fluorescent particles, unique six-dot-triangular and seven-dot-hexagonal patterns have been known to appear in the fluorescence microscopic images. Although it has been suggested that these two types of patterns correspond to local domain structures, i.e., face centered cubic (fcc) or hexagonal closed packed (hcp), no conclusive evidence has been provided to support this claim. In this study, we systematically investigated the relationship between the propagation patterns and the arrangement of the particles. Through a cross-check between an experiment using well-defined clusters fabricated by a micromanipulation technique and a rigorous calculation based on the expansion of vector spherical harmonics, we confirmed that the six-dot-triangular and seven-dot-hexagonal patterns correspond to the fcc and hcp domains, respectively. Further, we also found that the propagation patterns depend on the size of the clusters. As a result of a quantitative discussion on the light propagation in clusters with various sizes, it was clarified that a sufficient domain size is necessary for the appearance of clear triangular or hexagonal patterns.

Simvastatin decreases IL-6 and IL-8 production in epithelial cells.

Many cardiovascular studies have suggested that 3-hydroxy-3-methylglutaryl co-enzyme A reductase inhibitors (statins) have anti-inflammatory effects independent of cholesterol lowering. As a chronic inflammatory disease, periodontitis shares some mechanisms with atherosclerosis. Since oral epithelial cells participate importantly in periodontal inflammation, we measured simvastatin effects on interleukin-6 and interleukin-8 production by cultured human epithelial cell line (KB cells) in response to interleukin-1alpha. Simvastatin decreased production, an effect reversed by adding mevalonate or geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate. Simvastatin was found to reduce NF-kappaB and AP-1 promoter activity in KB cells. Dominant-negative Rac1 severely inhibited interleukin-1alpha-induced NF-kappaB and AP-1 promoter activity. Our results may indicate an anti-inflammatory effect of simvastatin on human oral epithelial cells, apparently involving Rac1 GTPase inhibition.

Novel protein kinase C-beta isoform selective inhibitor JTT-010 ameliorates both hyper- and hypoalgesia in streptozotocin- induced diabetic rats.

AIM: Activation of protein kinase C (PKC) is thought to play an important role in the pathogenesis of diabetic microvascular complications. PKC-beta is elevated in hyperglycaemic conditions, both in vivo and in vitro. In this study, pharmacological effects of a novel PKC-beta isoform selective inhibitor, JTT-010 ((2R)-3-(2-aminomethyl-2,3-dihydro-1H-3a-azacyclopenta(a)inden-8-yl)-4-phenylaminopyrrole-2,5-dione monomethanesulphonate), on diabetic neuropathy were examined. METHODS: PKC inhibitory activity of JTT-010 was evaluated with an enzyme assay. For the in vivo study, streptozotocin (STZ)-induced diabetic rats were treated with JTT-010 for 12 weeks and tail/sciatic nerve conduction velocity (NCV) evaluated. Hyper/hypoalgesia was evaluated using tail-flick and formalin tests. RESULTS: JTT-010 inhibited PKC-betaI and -betaII with IC50 values of 4.0 and 2.3 nm respectively. For other PKC isoforms, IC50 values were 54 nm or greater. In STZ-induced diabetic rats showing a reduction in tail/sciatic nerve conduction velocities, JTT-010 (0.3-3 mg/kg) ameliorated the reduction of these velocities. In a formalin test, STZ-induced diabetic rats had hyperalgesia in the first phase. JTT-010 reduced nociceptive response at doses of 0.1 mg/kg or higher. Furthermore, STZ-induced diabetic rats showed hypoalgesia in the second phase of the formalin test and tail-flick test. JTT-010 also ameliorates these symptoms at doses of 0.1 mg/kg or higher. CONCLUSIONS: These observations suggest that PKC-beta contributes not only to diabetic hyperalgesia, but also to hypoalgesia and also contributes to defects in NCV. PKC-beta inhibitor, JTT-010, may be beneficial in suppressing the development of diabetic nerve dysfunction, including hyperalgesia and hypoalgesia.

Post-mortem pathological examination of two patients after intraaneurysmal embolization using guglielmi detachable coils.

SUMMARY: We report the histological findings in two patients treated using Guglielmi detachable coils with almost complete occlusion of the aneurysms.Autopsies of these patients were performed one week and one year after GDC embolization respectively. In one aneurysm that was obtained at autopsy one week after embolization, the histological findings revealed coils and an unorganized thrombus-filled aneurysm sac; an incomplete cell-lining on the luminal side of fibrin thrombi in the region of the neck of the aneurysm was recognized. In the other aneurysm in which autopsy was performed one year after embolization, an organized fibrous tissue at the margin of the aneurysmal wall and vascular granulation tissue at the center of the aneurysm were observed. There is a single layer of endothelium covering fibrous tissue in the neck of the aneurysm. We discuss the healing process after GDC treatment.

Mazindol administration improved hyperphagia after surgery for craniopharyngioma--case report.

A 54-year-old man presented with visual disturbance and polydipsia. Magnetic resonance imaging disclosed a cystic mass which extended from the intrasellar to the suprasellar region. Bifrontal craniotomy was performed and the tumor was totally removed. Histological findings confirmed the diagnosis of craniopharyngioma. Postoperatively, the patient suffered from transient disorientation. About one month after the operation the patient manifested hyperphagia and he gained 15 kg in one month. Mazindol, a non-amphetaminergic anorectic agent, was administered for 3 weeks. His appetite normalized and his weight fell and stabilized even after mazindol administration was ceased.

Quality factor for localized defect modes in a photonic crystal slab upon a low-index dielectric substrate.

Localized defect modes in a two-dimensional photonic crystal slab upon a SiO(2) substrate have been analyzed by a numerical simulation of dipole radiation based on the finite-difference time-domain method. A degenerate pair of the defect mode of E(1) spatial symmetry was found in a pseudogap in the spectrum of dipole radiation. We achieved a quality factor as large as 800 by optimizing the sample geometry.

Intraaneurysmal Embolization for Wide-necked Aneurysms. Remodeling Technique, Combined Neck-Clipping and Coiling Therapy, Scaffolding Technique.

SUMMARY: We reported the results of the endovascular treatment using Guglielmi detachable coil (GDC) for wide-necked aneurysms. Fourteen aneurysms were treated with remodeling technique. One aneurysm was performed endovascular treatment followed by partial neck clipping. The other was treated with scaffolding technique. All aneurysms could not be performed by conventional GDC treatment initially because of coil protrusion into the parent artery due to wide neck of these aneurysms. These aneurysms sited at anterior circulation system in 10 cases, and at posterior circulation system in 6 cases. Immediately after the procedure, the obliteration rate could be obtained complete occlusion in 3 cases, > 95% occlusion in 7 cases, > 90% occlusion in 3 cases and < 90% occlusion in 3 cases. In 14 patients followup angiography or magnetic resonance image (MRI) was carried out. The angiographic follow-up period is range from 2 to 19 months (mean: 10 months). The results of angiographical follow-up indicated increasing obliteration rate with all aneurysms except for 2 cases. In these 2 cases, the reembolization was needed for recanalization of the aneurysm. The clinical follow-up period is range form one to 26 months (mean: 15 months). There is no evidence of aneurysmal rupture and all cases have been survival without any permanent neurological deficits. The GDC treatment with additional technique (remodeling technique, combined neck-clipping and coiling therapy, scaffolding technique) provides safety and effectiveness, even if there are wide-necked aneurysms.

Coil embolization of a large, wide-necked aneurysm using a double coil-delivered microcatheter technique in combination with a balloon-assisted technique.

The present paper describes a double coil-delivered microcatheter technique used in combination with a balloon-assisted technique to treat a patient with a large, wide-necked basilar tip aneurysm with detachable coil treatment. The aneurysm was completely occluded using this technique. There was no recanalization or any neurological deterioration within 12 months of embolization.

Gene expression of gastric type mucin (MUC5AC) in pancreatic tumors: its relationship with the biological behavior of the tumor.

Previously it has been found that the MUC2 gene for intestinal type secretory mucin is highly expressed in intraductal papillary mucinous tumors (IPMT), which are characterized by non-invasive growth and a favorable outcome. In contrast, MUC2 mRNA is rarely expressed in invasive ductal carcinomas (IDC), which have poor outcomes. The gastric type secretory mucin, MUC5AC, is strongly expressed in the surface mucous cells of gastric mucosa. As both MUC2 and MUC5AC mucins share the characteristics of forming highly viscous gels, it is expected that not only MUC2 mucin expression but also MUC5AC mucin expression may be associated with a favorable prognosis in patients with pancreatic tumors. MUC5AC mucin gene expression was examined in 24 cases of IPMT and 38 cases of IDC by in situ hybridization using a digoxigenin-labeled oligonucleotide. The results were compared with MUC2 mucin gene expression. Neither MUC5AC mRNA nor MUC2 mRNA was detected in normal pancreatic tissues. MUC5AC mRNA was expressed in 20 of 24 cases of IPMT (83%) and in five of 38 cases of IDC (13%). In contrast, MUC2 mRNA was expressed in 14 of 24 cases of IPMT (58%) and in none of the 38 cases of IDC (0%). The expression rates of MUC5AC mRNA and MUC2 mRNA in IPMT were significantly higher than those in IDC (P< 0.001, respectively). Intraductal papillary mucinous tumors are characterized by three histological types: (i) villous dark cell type; (ii) papillary clear cell type; and (iii) compact cell type. The villous dark cell type generally expressed both MUC5AC+ and MUC2+ genes. Alternatively, the papillary clear cell type and the compact cell type usually showed MUC5AC+ and MUC2- expression. Patients with MUC5AC mRNA expression had a significantly better survival prognosis than those with no MUC5AC mRNA expression (P< 0.005). In conclusion, MUC5AC gene expression occurs in a majority of IPMT cases, even in those with no MUC2 production. MUC5AC expression can be

Treatment of a vertebral dissecting aneurysm with a balloon-expandable stent and guglielmi detachable coils.

SUMMARY: A 43-year-old man with dissecting vertebral artery aneurysm presented with subarachnoid haemorrhage. The vertebral angiography showed a fusiform dilatation at the right intracranial vertebral artery between the origin of posterior inferior cerebellar artery and the vertebral union. After failing conservative therapy, a balloon-expandable stent was placed at intracranial vertebral artery, in a manner such that the entire dissecting aneurysm was covered. On follow-up angiogram, we recognized regrowth of theresidual aneurysm and stent deformation. The parent artery was occluded completely with several Guglielmi detachable coils. Brainstem dysfunction or rebleeding of the aneurysm were not encountered. Recently stenting therapy was deployed for a patient with dissecting aneurysm of the extracranial carotid or vertebral artery who was not a candidate for surgical treatment. We discuss the feasibilities and limitations of stent therapy.

Stenting therapy for extra-cranial carotid stenosis.

We report our initial results of stent placement for extra-cranial carotid stenosis. Fifteen patients aged 54 to 83 years (10 men) with > 60% extra-cranial carotid stenosis were treated with percutaneous stent implantation. Four patients were asymptomatic. The rate of stenosis ranged from 60% to 93% (mean: 74%). Balloon-expandable stents (Palmaz stent: 11, Cordis stent: 1, GFX stent: 2) were placed for fourteen patients and for one patient a self-expandable stent was used (Memotherm biliary stent). The proximal protective balloon technique was used in the most possible cases during predilatation or stent placement. Angiography or ultrasonography was performed as the evaluation of restenosis after stent placement. The definition of restenosis was > 50% stenosis. The mean period of follow-up was 8.5 months (from 1 to 20 months). In all patients, carotid stents were successfully placed. The mean rate of stenosis immediately after the procedure decreased to 0%. The protective balloon technique could be used in ten patients during pre-dilatation, in six during stent placement. One patient suffered a transient ischemic attack immediately after predilatation. The symptoms disappeared completely 15 minutes after onset. There was no patient with relapse or deterioration of neurological deficits after the procedure. There was no restenosis and stent deformation in the follow-up period. In our small series, stent placement for extra-cranial carotid stenosis was performed with a low rate of morbidity and mortality. However, it is necessary to develop more flexible, more controllable stents with increased mesh densities for exclusive neurointervention. In addition, the development of a more reliable protective balloon technique to decrease procedurerelated complications is needed.