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Objective To evaluate the diagnostic benefits of 5-mm maximum intensity projection of improved motion-sensitized driven-equilibrium prepared contrast-enhanced 3D T1-weighted turbo-spin echo imaging (MIP iMSDE-TSE) in the detection of brain metastases. The imaging technique was compared with 1-mm images of iMSDE-TSE (non-MIP iMSDE-TSE), 1-mm contrast-enhanced 3D T1-weighted gradient-echo imaging (non-MIP 3D-GRE), and 5-mm MIP 3D-GRE. Materials and Methods From October 2014 to July 2015, 30 patients with 460 enhancing brain metastases (size > 3 mm, n = 150; size ≤ 3 mm, n = 310) were scanned with non-MIP iMSDE-TSE and non-MIP 3D-GRE. We then performed 5-mm MIP reconstruction of these images. Two independent neuroradiologists reviewed these four sequences. Their diagnostic performance was compared using the following parameters: sensitivity, reading time, and figure of merit (FOM) derived by jackknife alternative free-response receiver operating characteristic analysis. Interobserver agreement was also tested. Results The mean FOM (all lesions, 0.984; lesions ≤ 3 mm, 0.980) and sensitivity ([reader 1: all lesions, 97.3%; lesions ≤ 3 mm, 96.2%], [reader 2: all lesions, 97.0%; lesions ≤ 3 mm, 95.8%]) of MIP iMSDE-TSE was comparable to the mean FOM (0.985, 0.977) and sensitivity ([reader 1: 96.7, 99.0%], [reader 2: 97, 95.3%]) of non-MIP iMSDE-TSE, but they were superior to those of non-MIP and MIP 3D-GREs (all, p < 0.001). The reading time of MIP iMSDE-TSE (reader 1: 47.7 ± 35.9 seconds; reader 2: 44.7 ± 23.6 seconds) was significantly shorter than that of non-MIP iMSDE-TSE (reader 1: 78.8 ± 43.7 seconds, p = 0.01; reader 2: 82.9 ± 39.9 seconds, p < 0.001). Interobserver agreement was excellent (κ > 0.75) for all lesions in both sequences. Conclusion MIP iMSDE-TSE showed high detectability of brain metastases. Its detectability was comparable to that of non-MIP iMSDE-TSE, but it was superior to the detectability of non-MIP/MIP 3D-GREs. With a shorter reading time, the false-positive results of MIP iMSDE-TSE were greater. We suggest that MIP iMSDE-TSE can provide high diagnostic performance and low false-positive rates when combined with 1-mm sequences.

Objective To evaluate the utility of high-resolution vessel wall imaging (HR-VWI) of middle cerebral artery (MCA), and to compare HR-VWI findings between striatocapsular infarction (SC-I) and lenticulostriate infarction (LS-I). Materials and methods This retrospective study was approved by the Institutional Review Board, and informed consent was waived. From July 2009 to February 2012, 145 consecutive patients with deep subcortical infarctions (SC-I, n = 81; LS-I, n = 64) who underwent HR-VWI were included in this study. The degree of MCA stenosis and the characteristics of MCA plaque (presence, eccentricity, location, extent, T2-high signal intensity [T2-HSI], and plaque enhancement) were analyzed, and compared between SC-I and LS-I, using Fisher's exact test. Results Stenosis was more severe in SC-I than in LS-I (p = 0.040). MCA plaque was more frequent in SC-I than in LS-I (p = 0.028), having larger plaque extent (p = 0.001), more T2-HSI (p = 0.001), and more plaque enhancement (p = 0.002). The eccentricity and location of the plaque showed no significant difference between the two groups. Conclusion Both SC-I and LS-I have similar HR-VWI findings of the MCA plaque, but SC-I had more frequent, larger plaques with greater T2-HSI and enhancement. This suggests that HR-VWI may have a promising role in assisting the differentiation of underlying pathophysiological mechanism between SC-I and LS-I.

Objective To simulate the B1-inhomogeneity-induced variation of pharmacokinetic parameters on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Materials and methods B1-inhomogeneity-induced flip angle (FA) variation was estimated in a phantom study. Monte Carlo simulation was performed to assess the FA-deviation-induced measurement error of the pre-contrast R1, contrast-enhancement ratio, Gd-concentration, and two-compartment pharmacokinetic parameters (Ktrans, ve, and vp). Results B1-inhomogeneity resulted in -23-5% fluctuations (95% confidence interval [CI] of % error) of FA. The 95% CIs of FA-dependent % errors in the gray matter and blood were as follows: -16.7-61.8% and -16.7-61.8% for the pre-contrast R1, -1.0-0.3% and -5.2-1.3% for the contrast-enhancement ratio, and -14.2-58.1% and -14.1-57.8% for the Gd-concentration, respectively. These resulted in -43.1-48.4% error for Ktrans, -32.3-48.6% error for the ve, and -43.2-48.6% error for vp. The pre-contrast R1 was more vulnerable to FA error than the contrast-enhancement ratio, and was therefore a significant cause of the Gd-concentration error. For example, a -10% FA error led to a 23.6% deviation in the pre-contrast R1, -0.4% in the contrast-enhancement ratio, and 23.6% in the Gd-concentration. In a simulated condition with a 3% FA error in a target lesion and a -10% FA error in a feeding vessel, the % errors of the pharmacokinetic parameters were -23.7% for Ktrans, -23.7% for ve, and -23.7% for vp. Conclusion Even a small degree of B1-inhomogeneity can cause a significant error in the measurement of pharmacokinetic parameters on DCE-MRI, while the vulnerability of the pre-contrast R1 calculations to FA deviations is a significant cause of the miscalculation.

Purpose: We aimed to evaluate the utility of two types of MR cisternography [fast spin echo sequence and steady-state coherent gradient echo (GRE) sequence] in addition to phase contrast-cine imaging (PC-cine), for assessing patency at the aqueduct and third ventriculostomy site. Materials and Methods: 43 patients (35 patients with suspected aqueductal stenosis and 8 patients with third ventriculostomy) were retrospectively analyzed. PCcine, 3 dimensional sagittal fast spin echo sequence [driven-equilibrium imaging (DRIVE) or volumetric isotrophic T2-weighted acquisition (T2 VISTA)] and steadystate coherent fast GRE sequence (balanced turbo field echo; bTFE) imaging were performed in all patients. The patency of the aqueduct or third ventriculostomy site was scored. Some pitfalls of each sequence were also analyzed in individual cases. Results: 93% of all cases showed consistent scores in PC-cine, DRIVE/T2 VISTA, and bTFE imaging. DRIVE/T2 VISTA imaging provided functional information of cerebrospinal fluid flow with flow-related artifacts, while bTFE imaging allowed direct visualization of the aqueduct or ventriculostomy site. However, evaluation of anatomical structures was difficult in three cases with strong flow-related artifacts on DRIVE/T2 VISTA and in 2 cases with susceptibility artifacts on bTFE. Conclusion: Both DRIVE/T2 VISTA and bTFE imaging have complementary roles in evaluating the patency of the aqueduct and 3rd ventriculostomy site. Index terms Aqueductal Stenosis Third Ventriculostomy Volumetric Isotrophic T2-Weighted Acquisition Driven-Equilibrium Imaging Balanced Turbo Field Echo

Purpose: We wanted to determine whether or not the “susceptibility asymmetry index” (SAI) of acute stroke on the T2*-weighted image is related with successful recanalization using multimodal intra-arterial thrombolysis (IAT). Materials and Methods: The 81 patients who underwent multimodal IAT for middle cerebral artery (MCA) territory acute stroke were included in this retrospective study. The multimodal IAT included intra-arterial urokinase infusion, clot disruption by a microwire, microcatheter and balloon manipulation, and balloon angioplasty and/or stenting for the flow-limiting stenosis. The diameter of the susceptibility vessel sign was measured on the T2*-weighted gradient echo imaging (GRE), and the diameter of the contralateral normal MCA at the corresponding level was measured on magnetic resonance angiography (MRA); the ratio between these two diameters was defined as the susceptibility asymmetry index. The relation between the TICI (Thrombolysis In Cerebral Infarction) score of 2-3 after multimodal IAT and the SAI was assessed. The receiver operating characteristic (ROC) curve analysis was performed on the SAI to predict a TICI score of 2-3 after multimodal IAT. Results: The mean SAI of 81 patients was 1.66 ± 0.66. Seventy nine percent of the patients had a TICI of 2-3 after multimodal IAT. According to the ROC curve analysis, an SAI less than 1.3 was optimal for predicting the presence of stenotic lesion after recanalization (area under the curve: 0.821, sensitivity: 88.2%, specificity: 69.8%, p=0.0001), and the SAI ≤1.61 (area under the curve: 0.652, sensitivity: 60.9%, specificity: 70.6%, p=0.0226) could predict a TICI score of 2-3. The TICI score of 2-3 after multimodal IAT was achieved in 88.6% of the cases with a SAI ≤ 1.61 and in 67.6% of the cases with a SAI >1.61 (p=0.028). Conclusion: The lower SAI on T2*-GRE could predict stenotic lesion and successful recanalization after performing IAT.

Objective To evaluate our early experience using self-expanding stents to treat atherosclerotic vertebral artery ostial stenosis (VAOS), with respect to technical feasibility and clinical and imaging follow-up results. Materials and Methods A total of 20 lesions in 20 patients underwent stenting of the VAOS using a self-expanding stent (Precise RX; Cordis Neurovascular, Miami Lakes, FL). Two patients were asymptomatic. We analyzed the technical success rate, causes of technical failure, occurrence of any vascular or neurological event, and the occurrence of any neurological abnormality or in-stent restenosis (ISR) seen on follow-up. The imaging follow-up was performed with Doppler ultrasound (DUS) as a primary screening modality. Results One instance of technical failure was caused by failure of the guidewire passage. The stent diameter was 5 mm, and post-stenting balloon dilatations were necessary in all cases. Stent misplacement requiring placement of an additional stent occurred in four cases. Following a 14.8 month average clinical follow-up time, two patients showed anterior circulation ischemia, which was not attributed to the VAOS we treated. Following a 13.7 month average DUS follow-up, five patients showed a mild degree of diffuse or focal intimal thickening in the stent lumen; however, none of the stenosis showed luminal loss of more than 50% and no stent fracture was noted. Conclusion The use of self-expanding stents for treating VAOS was technically feasible and helped to improve artery patency during our limited follow-up interval.

Objective Although three-dimensional time-of-flight magnetic resonance angiography (3D TOF-MRA) is used frequently as a follow-up tool to assess the response of arteriovenous malformations (AVMs) after radiosurgery, the diagnostic accuracy of 3D TOF-MRA is not well known. We evaluated the diagnostic accuracy of contrast-enhanced 3D TOF-MRA at 3.0 Tesla for the detection of residual AVMs. Materials and methods This study included 32 AVMs from 32 patients who had been treated with radiosurgery (males/females: 21/11; average patient age, 33.1 years). The time interval between radiosurgery and MRA was an average of 35.3 months (range, 12-88 months). Three-dimensional TOF-MRA was obtained at a magnetic field strength of 3.0 Tesla after infusion of contrast media, with a measured voxel size of 0.40 x 0.80 x 1.4 (0.45) mm(3) and a reconstructed voxel size of 0.27 x 0.27 x 0.70 (0.05) mm(3) after zero-filling. X-ray angiography was performed as the reference of standard within six months after MRA (an average of two months). To determine the presence of a residual AVM, the source images of 3D TOF-MRA were independently reviewed, focusing on the presence of abnormally hyperintense fine tangled or tubular structures with continuity as seen on consecutive slices by two observers blinded to the X-ray angiography results. Results A residual AVM was identified in 10 patients (10 of 32, 31%) on X-ray angiography. The inter-observer agreement for MRA was excellent (kappa= 0.813). For the detection of a residual AVM after radiosurgery as determined by observer 1 and observer 2, the source images of MRA had an overall sensitivity of 100%/90% (10 of 10, 9 of 10), specificity of 68%/68% (15 of 22, 15 of 22), positive predictive value of 59%/56% (10 of 17, 9 of 16), negative predictive value of 100%/94% (15 of 15, 15 of 16) and diagnostic accuracy of 78%/75% (25 of 32, 24 of 32), respectively. Conclusion The sensitivity of contrast-enhanced 3D TOF-MRA at 3.0 Tesla is high but the specificity is not sufficient for the detection of a residual AVM after radiosurgery.

Purpose: To investigate the clinical significance of mesenteric lymph nodes (MLNs) detected on postoperative CT images after a total pharyngolaryngectomy and reconstruction using a jejunal free flap (TPL-JFF) in patients with advanced carcinoma of the laryngo-hypopharynx. Materials and Methods: We recruited 17 patients with available postoperative CT images following a TPL-JFF. The postoperative CT findings of the MLNs for the JFF were evaluated, including the number of MLNs, maximum-axial-diameter, shape, and presence of central necrosis or cortical enhancement, which were compared between the two groups and divided according to the presence or absence of local recurrence. Results: In 16 of 17 patients except for one patient without MSN, an initial postoperative CT image demonstrated the presence of MLNs (mean number, 2; range 1-4) which had a maximal diameter of 18 mm. New or an increased number of MLNs detected on a subsequent follow-up CT examination was found in only two patients with recurrence. However, MLNs in nine patients without recurrence remained unchanged or decreased. Cortical enhancement was found more frequently in all five MLNs of the two patients with recurrence as compared to cortical enhancement in the MLNs (four among 12 MLNs: 33%) of patients without recurrence. The other findings remained the same. Conclusion: MLNs on postoperative CT images are very common in patients after a TPL-JFF. Although most MLNs are reactive, a new or increased number of MLNs on a subsequent follow-up CT examination should suggest the presence of a local recurrence.

Objective To compare the usefulness of magnetic resonance cholangiopancreatography (MRCP) and MR angiography (MRA) in differentiating malignant from benign intraductal papillary mucinous tumors of the pancreas (IPMTs), and to determine the findings which suggest malignancy. Materials and Methods During a 6-year period, 46 patients with IPMT underwent MRCP. Morphologically, tumor type was classified as main duct, branch duct, or combined. The diameter of the main pancreatic duct (MPD), the extent of the dilated MPD, and the location and size of the cystic lesion, septum, and communicating channel were assessed. For all types of IPMTs, enhanced mural nodules and portal vein narrowing were evaluated at MRA. Results Combined-type IPMTs were more frequently malignant (78%) than benign (42%) (p < 0.05). Compared with benign lesions, malignant lesions were larger, and the caliber of the communicating channel was also larger (p < 0.05). Their dilated MPD was more extensive and of greater diameter (p < 0.05), and the presence of mural nodules was more frequent (p < 0.001). Conclusion Combined MRCP and MRA might be useful for the differential diagnosis of malignant and benign IPMTs of the pancreas.