Keita Sakurai

Mechanisms of hydrogen peroxide-induced relaxation in rabbit mesenteric small artery.

The effects of hydrogen peroxide were studied on isolated rabbit mesenteric small artery; rabbit superior mesenteric artery and mouse aorta were also studied as reference tissues. For mesenteric small artery, hydrogen peroxide (1 to 100 microM) relaxed a norepinephrine-stimulated artery in a concentration-dependent manner. The relaxation was not significantly affected by removal of the endothelium and was less pronounced in arteries contracted with high-KCl solution plus norepinephrine than in those contracted with norepinephrine alone. The relaxation response to hydrogen peroxide was increased by isobutylmethylxanthine and zaprinast, inhibited by diclofenac, methylene blue and dithiothreitol and unaffected by atropine, tetraethylammonium, superoxide dismutase, deferoxamine, dimethyl sulfoxide or the Rp stereoisomer of adenosine cyclic monophosphothioate. Hydrogen peroxide shifted concentration-contractile response curves for norepinephrine to the right and downwards. Norepinephrine and caffeine elicited a transient, phasic contraction of the mesenteric small artery exposed for 0.5, 1 and 2 min to a Ca2+-free solution. Hydrogen peroxide inhibited the norepinephrine-induced contraction, and to a lesser extent the caffeine-induced contraction, and verapamil did not alter the contraction to norepinephrine. These pharmacological properties of hydrogen peroxide were similar to those of 8-bromo cGMP; 8-bromo cGMP inhibited more potently the norepinephrine-induced than the KCl-induced contraction and the contraction elicited by norepinephrine in Ca2+-free solution. The present results suggest that hydrogen peroxide induces endothelium-independent relaxation of the rabbit mesenteric small artery precontracted with norepinephrine. The effects of hydrogen peroxide may be at least in part mediated by cGMP and cyclooxygenase products in the vascular smooth muscles now used.

Evaluation of luminal and vessel wall abnormalities in subacute and other stages of intracranial vertebrobasilar artery dissections using the volume isotropic turbo-spin-echo acquisition (VISTA) sequence: a preliminary study.

OBJECTIVE To evaluate the utility of 3D variable refocusing flip-angle volume isotropic turbo-spin-echo acquisition (VISTA) imaging, using a 1.5-T MRI unit, which can minimize flow artifacts, due to its sequence-endogenous flow-void capability, in the diagnosis of intracranial vertebrobasilar artery dissection (VAD). MATERIAL AND METHODS The presence of intimal flaps, intramural hematomas, vessel dilatations and abnormal vessel enhancements were evaluated on T1-weighted VISTA images from 18 VAD patients with 20 dissected arteries (15 subacute and five at other stages). Additional gadolinium-enhanced T1VISTA images were available for 13 patients. The frequency of flow artifacts on T1VISTA imaging in 70 non-dissected arteries in VAD patients and 12 control subjects was also evaluated. Furthermore, in 13 and eight patients, contrast-enhanced three-dimensional (CE3D) imaging with spoiled gradient-recalled (SPGR) acquisition in steady state and electrocardiographically gated black-blood (BB) T1-weighted imaging (T1WI) were evaluated to compare visualization of false lumens. RESULTS Intimal flaps, intramural hematomas and dilatations were identified on T1VISTA images in 65% (13/20), 55% (11/20) and 90% (18/20) of VADs, respectively. Abnormal vessel enhancement was recognized in 100% (15/15) of VADs on contrast-enhanced T1VISTA images. Only four normal arteries showed small, thin, linear artifacts. Compared with CE3D-SPGR imaging, T1VISTA imaging depicted false lumens more conspicuously in seven VADs (P=0.02). T1VISTA also revealed intimal flaps and hematomas as did BB T1WI. CONCLUSION T1VISTA imaging may be useful for diagnosing VAD at subacute stages, as it can reveal vessel wall and lumen abnormalities with a minimum of flow artifacts.

Thoracic hemangiomas: imaging via CT, MR, and PET along with pathologic correlation.

Purpose To characterize the imaging features of thoracic hemangioma, including findings on computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) using 18F-fluoro-2-deoxy-D-glucose (FDG). Methods Six patients with thoracic wall hemangioma and 2 patients with mediastinal hemangioma were included in this study. Preoperative evaluation was performed using CT (n=7), MRI (n=8), and FDG-PET (n=2). Five cases were pathologically confirmed by surgery and the remaining 3 cases were diagnosed clinically. Results On CT, characteristic finding of phleboliths were depicted in 5 of 7 cases (71%). Fat component was demonstrated in 3 of 7 cases with CT (3/7—43%) and 5 of 8 cases with MRI (5/8—63%). On MRI, characteristic finding of high intensity on T2-weighted images was demonstrated in all 8 cases and the high signal intensity was emphasized in all 4 cases on fat-suppression T2-weighted images. Both of two PET scans showed mildly elevated accumulation of FDG. Conclusions Phleboliths, fat component, and high intensity on T2-weighted and fat-suppression T2-weighted image were thought to be characteristic findings reflecting the histologic findings. It might be useful to recognize these findings for differentiating hemangiomas from other soft tissue tumors, particularly malignant neoplasms.

Usefulness of 3D-PRESTO imaging in evaluating putaminal abnormality in parkinsonian variant of multiple system atrophy.

IntroductionPrinciples of echo shifting with a train of observations (PRESTO) sequence has long echo time which emphasizes the effect of T2* relaxation time and contribute to its high sensitivity to the susceptibility change. The aim of our study was to evaluate the ability of 3D-PRESTO sequence in detecting putaminal hypointensity in patients with parkinsonian variant of multiple system atrophy (MSA-P) and in discriminating between MSA-P and Parkinsons disease (PD).MethodsThe signal intensity of the putamen and localization of abnormality were evaluated on 3D-PRESTO, T2*-weighted (T2*W), and T2-weighted (T2W) sequences in ten patients with MSA-P, 14 with PD, and ten controls. The putaminal signal intensity was assessed in all sequences and graded relative to the palladium. Atrophy of the putamen and posterolateral hyperintensity rim on T2W sequence were also evaluated in MSA-P patients.ResultsPutaminal hypointensity was more often seen in MSA-P than PD and controls on 3D-PRESTO sequence (p = 0.002) as well as on T2*W sequence (p = 0.003). 3D-PRESTO sequence could reveal lower intensity better than T2*W sequence in four of ten MSA-P cases. Hemi- or bilateral putaminal hypointensity, atrophy, and posterolateral hyperintensity rim were recognized in 90%, 70%, and 70% of ten MSA-P cases, respectively. Three cases revealed hypointensity on 3D-PRESTO sequence without posterolateral hyperintensity rim. Putaminal signal changes occurred in the posterolateral part with a striking lateral to medial gradient in all nine cases with putaminal hypointensity (nine out of nine, 100%).Conclusions3D-PRESTO sequence appears to be useful for depicting putaminal hypointensity in MSA-P patients and in differentiating MSA-P from PD.

Wernicke’s Encephalopathy with Cortical Abnormalities: Clinicoradiological Features: Report of 3 New Cases and Review of the Literature

Objective: To investigate clinical and magnetic resonance imaging (MRI) features of Wernicke’s encephalopathy with cortical abnormalities (WEc). Methods: We retrospectively evaluated the clinical features and MRI findings in 3 cases of WEc in comparison with those of 7 previously reported cases. Results: Besides the classical triad of ocular abnormalities, ataxia and global confusion, muscular weakness of all extremities was frequently recognized (5 of 6 evaluable cases; 83%). During the clinical courses, 2 patients (20%) died and 1 fell into a vegetative state. The cortical abnormalities were distributed in the frontal and parietal lobes, especially around the bilateral central sulcus, in all cases. In 1 case, the cortical abnormality was irreversible, and the abnormal lesion, similar to that seen in laminar necrosis, persisted. Conclusions: Bilateral frontal cortical abnormalities around the central sulcus and muscular weakness of all extremities might be the characteristic features of WEc.

Reperfusion Rates of Pulmonary Arteriovenous Malformations after Coil Embolization: Evaluation with Time-Resolved MR Angiography or Pulmonary Angiography

PURPOSE To assess reperfusion rates after coil embolization for pulmonary arteriovenous malformations (PAVMs) using time-resolved magnetic resonance (MR) angiography or pulmonary angiography. MATERIALS AND METHODS Patients with PAVMs who underwent embolization and met the following inclusion criteria were included: (a) embolization was performed using bare or fibered platinum microcoils or both, (b) the complete cessation of flow was confirmed by digital subtraction angiography, and (c) follow-up examinations were conducted with time-resolved MR angiography or pulmonary angiography. Coil embolization was performed in 16 patients with 24 untreated or reperfused PAVMs. Sac embolization was performed for 12 untreated PAVMs. Feeding artery embolization was performed as primary embolization in each of the 12 reperfused PAVMs. Five PAVMs were treated 2 to 4 times because of reperfusion. The study included 32 coil embolizations. Follow-up images were reviewed, and reperfusion rates were assessed. The relationships between reperfusion and the location of PAVM, size of PAVM (feeding artery and venous sac), coils (number and total length), timing of embolization (primary or repeat embolization), and types of coils used (with or without fibered coils) were examined. RESULTS Reperfusion rates at 3, 6, 12, and 24 months were 8%, 27%, 36%, and 49%, respectively, for the 12 untreated PAVMs (primary embolization) and 50%, 50%, 92%, and 100%, respectively, for the 12 reperfused PAVMs (repeat embolization) (P = .0062). No significant differences were observed in the other parameters measured. CONCLUSIONS When evaluated with time-resolved MR angiography or pulmonary angiography, reperfusion rates after coil embolization for PAVM were considerably high, particularly with repeat embolization.

Postpuncture CSF leakage A potential pitfall of radionuclide cisternography

Objective: We sought to evaluate radioisotope cisternography (RICG)–related postpuncture CSF leakage by MRI. Methods: We conducted a prospective 3-day imaging study. Ten patients with orthostatic headache and other symptoms underwent pre-RICG brain and spinal MRI, magnetic resonance myelography (MRM), RICG, and post-RICG spinal MRI and MRM. For RICG, we used a 25-gauge pencil point spinal needle at the L3/4 or L4/5 level after which subjects took bed rest for 2.5 hours. Results: On pre-RICG MRI and MRM, none of the 10 patients showed CSF leakage. However, 5 subjects (50%) showed epidural abnormalities suggesting CSF leakage on MRI after lumbar puncture for RICG. On RICG and subsequent MRM, 4 of the subjects showed definite findings of CSF leakage and 1 showed minimal leakage. Conclusions: RICG carries a risk of iatrogenic CSF leakage even with careful puncturing using a fine needle. This leakage produces abnormal RICG and MRM findings at the lumbosacral level. Therefore, abnormal RICG findings restricted to the lumbosacral level should be carefully interpreted when diagnosing SIH.

Diagnostic Accuracy of 18F-2-deoxy-fluoro-D-glucose Positron Emission Tomography for pN1 Lymph Nodes in Patients with Lung Cancer

Background: The accuracy of 18F-2-deoxy-fluoro-D-glucose positron emission tomography (FDG-PET) for diagnosing nodal status in patients with lung cancer was initially reported as excellent, but, with increasing experience, the problem of false-positive and false-negative assessments has been observed. Purpose: To evaluate the accuracy of FDG-PET for diagnosing nodal status in lung cancer patients with pathologically proven N2 lymph nodes and compare it with that of computed tomography (CT). Material and Methods: Nineteen pN2 patients (13 males and six females) with primary lung cancer undergoing preoperative CT and FDG-PET were investigated. Lymph nodes were considered to be positive when uptake higher than the surrounding mediastinal level was visually observed. Slight symmetrical mediastinal uptake was considered to be negative, representing benign physiological accumulation. Radiological and pathological correlation was investigated, and the association between FDG accumulation and the size of metastatic lymph nodes and metastatic lesions was evaluated. Results: Of the 19 patients, nodal stage determined by using FDG-PET was cN0 in four (21%) cases, cN1 in three (16%), cN2 in nine (47%), and cN3 in three (16%). On CT, nodal stage was cN0 in three (16%) cases, cN1 in seven (37%), cN2 in eight (42%), and cN3 in one (5%). Thus, FDG-PET provided correct N-staging in 47%, under-staging in 37%, and overstaging in 16%. CT staging was correct in 42%, underestimated in 53%, and overestimated in 5%. The maximum area of metastatic foci was 15.8 ±21.3 mm2 (mean ± SD) in false-negative nodes and 75.0±56.3 mm2 in true-positive nodes (P<0.0001). Conclusion: Diagnostic accuracy of FDG-PET (47%) was low and similar to that of CT (42%). The possibility of false-negative as well as false-positive findings should be recognized in interpreting PET images. Micrometastasis appeared to be the greatest cause of false-negative findings.

Clinical usefulness of the triaxial system in super-selective transcatheter arterial chemoembolization for hepatocellular carcinoma

Background Transcatheter arterial chemoembolization (TACE) has been widely performed for inoperable hepatocellular carcinoma (HCC). Super-selective TACE is preferable to non-selective therapy and it is important to advance the catheter tip as close to the tumor as possible in the feeding artery. A new microcatheter with a 1.9-Fr non-tapered tip has recently become available and this new microcatheter can be inserted into a 2.7-Fr. microcatheter. It is called the triple co-axial (triaxial) system. Purpose To evaluate the clinical usefulness of super-selective TACE for HCC using the triaxial system. Material and Methods We evaluated 63 HCCs that underwent super-selective TACE. Requirements for inclusion in this study were: (a) HCCs 3 cm or less in diameter; (b) TACE performed by a single operator; and (c) no additional treatment in the absence of local progression. All patients were followed for more than 1 year after TACE. The median follow-up period for surviving patients was 20 months (range, 17–31 months). The conventional system was used in 35 HCCs (control group), and the triaxial system was used in 28 (triaxial group). We reviewed angiographies at TACE and follow-up CT, and then evaluated local tumor status in the two groups. Results Local tumor control rates at 3, 6, and 18 months were 64%, 36%, and 29%, respectively, in the triaxial group, and 40%, 14%, and 8.6%, respectively, in the control group (P = 0.0086). There were no major complications in either group. Conclusion The triaxial system appears to be useful for super-selective TACE and may contribute to achieving higher local control rates for HCC.

Plaque Vulnerability in Internal Carotid Arteries with Positive Remodeling

Background: This study aimed to evaluate the efficacy of assessing positive remodeling for predicting future stroke events in the internal carotid artery. We therefore assessed narrowing of the carotid artery lumen using multidetector-row computer tomography (MDCT) angiography and carotid plaque characteristics using black-blood (BB) magnetic resonance (MR). Methods: We retrospectively selected 17 symptomatic and 11 asymptomatic lesions with luminal narrowing >50%. We compared remodeling parameters of luminal stenosis (remodeling ratio, RR/remodeling index, RI) using MDCT and MR intensities of atherosclerotic plaque contents using the BB technique (relative signal intensity, rSI). We also confirmed the validity of the relationship between MR intensity and atherosclerotic plaque contents by histology. The levels of biological markers related to vessel atherosclerosis were measured. Results: Plaque lesions with positive remodeling in carotid arteries were associated with a significantly higher prevalence of stroke compared with plaques with negative remodeling (p < 0.05). Radiologic and histologic analyses determined that plaques with positive remodeling had higher signal intensities (with respect to their lipid-rich content or to hemorrhage) compared with negative remodeling (correlation coefficients: RI and rSI, r = 0.41, p < 0.05; RR and rSI, r = 0.50, p < 0.05). Levels of biological markers, including high-sensitivity C-reactive protein, hemoglobin A1C, total cholesterol, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol, were not useful for predicting stroke events. Conclusions: The results of this study suggest that the combined analysis of RR, RI and rSI could potentially help to predict future stroke events.