Ikuko Uwano

Background: Computed tomography angiography (CTA) tends to overestimate restenosis after cervical carotid stenting because of the substantial blooming artifacts from metallic stent materials. Hence, we propose a new measurement method to address this issue and assess the accuracy and reliability of evaluating the degree of in‐stent stenosis (ISS) compared with digital subtraction angiography (DSA) as a post‐hoc analysis of the CAS‐CARE (Carotid Artery Stenting with the Cilostazol Addition for Restenosis) trial. Methods: Among the image data registered for the trial, 197 paired data sets of poststenting images obtained using both CTA and DSA were used. We measured the ISS degree according to the NASCET (North American Symptomatic Carotid Endarterectomy Trial) criteria with the conventional and new methods using the inner edge and midportion of the stent materials as a boundary to the lumen and compared the stenotic severities with those obtained from DSA. Results: The ISS degrees measured using CTA with the conventional method were remarkably higher than those measured using CTA with the new method and DSA (median, 49.5% versus 11.3% and 9.8%; P P P = 0.034) in the conventional method, although correlations with DSA were comparable between the 2 methods (r = 0.68 [95% CI, 0.59–0.75] and 0.65 [95% CI, 0.56–0.72], respectively). Conclusion: Measurement using CTA with the midportion of the stent materials significantly improved the accuracy of the ISS degree, which was comparable to that using DSA.

BACKGROUND AND PURPOSE: Post-carotid endarterectomy (CEA) cerebral hyperperfusion (CH) can cause intracerebral hemorrhage and cognitive decline. Alterations in susceptibility in response to acetazolamide (ACZ) on 7T MRI quantitative susceptibility mapping (QSM) detects elevated CBV occurring due to impaired cerebrovascular autoregulation. We explored preoperative relative susceptibility changes on 7T MRI QSM in response to ACZ and their ability to predict CH following CEA. MATERIALS AND METHODS: Sixty-three patients with uni-or bilateral cervical ICA stenosis ≥70% underwent 7T MRI at baseline and at 5, 10, 15, and 20 min after ACZ administration before surgery. The difference between the susceptibility of venous structures and surrounding brain parenchyma at each time point after ACZ administration relative to the difference at baseline (relative susceptibility difference; RSD) on QSM images was calculated in the cerebral hemisphere ipsilateral to surgery. Brain perfusion SPECT was conducted preoperatively and immediately following CEA to detect postoperative CH (≥ 100% rise in CBF postoperatively). RESULTS: In nine patients with postoperative CH, RSD was significantly increased at 5 or 10 min following ACZ administration (p < 0.05) but reduced at 15 and 20 min (p < 0.05). In 54 patients without postoperative CH, RSD at all four time points after ACZ administration was significantly lower than the baseline value (p < 0.05). The area under the receiver operating characteristic curve to predict postoperative CH was significantly greater in RSD₅ (0.981; 95% CI, 0.910–0.999) than in RSD₁₅ (0.872; 95% CI, 0.764–0.943) (p < 0.05) or RSD₂₀ (0.780; 95% CI, 0.658–0.874) (p < 0.01). Sensitivity, specificity, and positive and negative predictive values for RSD₅ at a cutoff near the left upper corner of the curve were 100%, 89%, 60%, and 100%, respectively. Logistic regression analysis revealed that only RSD₅ significantly predicted postoperative CH (95% CI, 455.9–4043.6; p < 0.05). CONCLUSIONS: Changes in susceptibility on preoperative 7T MRI QSM following ACZ administration predict CH following CEA. Patients with increased RSD₅ on pre-CEA 7T MRI QSM following ACZ administration should undergo brain perfusion imaging immediately after surgery. Detection of CH on postoperative brain perfusion imaging warrants intensive blood pressure control. ABBREVIATIONS: CEA= carotid endarterectomy; CH= cerebral hyperperfusion; OEF= oxygen extraction fraction; ACZ= acetazolamide; QSM =quantitative susceptibility mapping; 3D =three-dimensional; RSD=relative susceptibility difference; SD= standard deviation; ROC =receiver operating characteristic.

Quantitative susceptibility mapping (QSM) has been proposed to assess intraplaque hemorrhage (IPH) in the carotid artery. The purpose of this study was to compare the diagnostic accuracy of preoperative QSM with that of the conventional T1-weighed (T1W) three-dimensional (3D)-FSE sequence for detecting IPH in cervical ICA stenosis in patients undergoing carotid endarterectomy (CEA) using histology as the reference standard. Carotid T1W 3D-FSE and QSM images were obtained from 16 patients with cervical ICA stenosis before CEA. Relative signal intensity (RSI) and susceptibility of the ICA were measured on three axial images including the location of most severe stenosis on T1W 3D-FSE and QSM images, respectively. Three transverse sections of carotid plaques excised by CEA, which corresponded with images on MRI, were stained with H&E, antibody against glycophorin A and Prussian blue, and the relative area (RA) of histologic IPH was calculated. The correlation coefficient was significantly greater between susceptibility and RA-histologic IPH (ρ = 0.691) than between RSI and RA-histologic IPH (ρ = 0.413; P = .0259). The areas under the receiver operating characteristic curves for detecting histologic sections consisting primarily of IPH (RA-histologic IPH > 40.7%) tended to be greater for susceptibility (0.964) than for T1WI FSE-RSI (0.811). Marginal homogeneity was observed between susceptibility and histologic sections consisting primarily of IPH (P = .0412) but not between T1W FSE-RSI and histologic sections consisting primarily of IPH (P = .1824). Pre-CEA QSM detects histologic IPH in cervical ICA stenosis more accurately than preoperative T1W 3D-FSE imaging. QSM = quantitative susceptibility mapping; IPH = intraplaque hemorrhage; T1W = T1-weighed; 3D = three-dimensional; CEA = carotid endarterectomy; RSI = relative signal intensity; RA = relative area.

The assessment of cerebral perfusion and metabolism is crucial in evaluating the indications for bypass surgery and other revascularization procedures in patients with chronic hemodynamic cerebral ischemia. In particular, it is necessary to detect misery perfusion(Powers' stage II), which is defined as an increased oxygen extraction fraction and increased cerebral blood volume or impaired cerebrovascular reactivity, with a constant cerebral metabolic rate of oxygen. Among the imaging techniques available for this purpose, ¹⁵O-positron emission tomography(PET)and acetazolamide-challenge single-photon emission computed tomography(SPECT)remain the de facto standards; however, these have substantial limitations such as invasiveness and the risk of severe adverse effects. Recently, several less invasive, easy-to-use techniques, such as perfusion computed tomography and magnetic resonance(MR)imaging, arterial spin labeling, quantitative susceptibility mapping, intravoxel incoherent motion, MR spectroscopy, and single-slab MR angiography, have also been introduced. These techniques may serve as alternatives to PET or SPECT if validation studies are successful and standardization among vendors is achieved.

Quantitative susceptibility mapping (QSM) is an advanced MRI technique for evaluating the distribution of magnetic susceptibility related to substances such as iron, hemosiderin, and deoxyhemoglobi... Quantitative susceptibility mapping (QSM), one of the advanced MRI techniques for evaluating magnetic susceptibility, offers precise quantitative measurements of spatial distributions of magnetic s...

We investigated the spatial and temporal variations of flip-angle (FA) distributions in the human brain from multiple scans, using an eight-channel parallel transmission (pTx) system at 7T. Nine healthy volunteers were scanned in five sessions using three radiofrequency excitation techniques each time: circular polarization (CP), static pTx, and dynamic pTx. We calculated the coefficients of variation of the FA values within the brain area to evaluate the variations, and the maximum intersession differences in the FA values (D_max), comparing them between the three methods. The coefficients of variation decreased in the following order: CP, static pTx, and dynamic pTx (median: 20.1%, 13.6%, and 5.7%, respectively; p < 0.001). The average D_max values were significantly higher for the static pTx (5.4°) than for the dynamic pTx (2.8°) and CP (1.7°) methods (p = 0.004 and 0.001, respectively). Compared to the CP method, the dynamic pTx method at 7T can efficiently minimize spatial variations in the FA distribution with a mild increase in temporal variations. The static pTx method exhibited a remarkably wide temporal variation.

Several basic experimental studies have demonstrated that statins have beneficial effects for intracranial aneurysm (IA). Clinical studies on unruptured IAs, however, remain limited to four retrospective studies that have reached different conclusions. This study was the first open-label, multicenter, randomized controlled trial to assess the preventive effects of atorvastatin. Patients with unruptured small saccular IAs were randomly assigned to statin and control groups. The primary endpoint was a composite of aneurysm growth of ≥0.5 mm, new bleb formation confirmed from magnetic resonance (MR) angiography, and rupture. Enrollment was prematurely terminated due to unexpectedly slow enrollment. Of 231 patients (275 target IAs), 110 patients (128 IAs) were randomly assigned to the statin group and 121 patients (147 IAs) to the control group. After excluding 22 dropout patients, 107 IAs in the 93 statin group patients and 140 IAs in the 116 control group patients were finally analyzed. No significant differences of basic characteristics were evident between groups, except for significantly higher systolic pressure in the statin group (P = 0.03). The primary endpoint occurred in 28 IAs (20.0%) in the control group and in 17 IAs (15.9%) in the statin group. No aneurysm rupture was confirmed in either group. Significant beneficial effects of statin for IAs were not demonstrated for the primary endpoint (log-rank P = 0.359). This randomized trial did not establish any preventive effects of atorvastatin for unruptured small IAs. Further studies of larger cohorts are required to clarify the efficacy of statins for patients with unruptured IAs.Clinical trial registration: UMIN000005135