Seung Bae Hwang

Detection of hepatocellular carcinoma: gadoxetic acid-enhanced 3-dimensional magnetic resonance imaging versus multi-detector row computed tomography.

Purpose: The aim of this study was to compare the diagnostic accuracy and sensitivity of gadoxetic acid-enhanced magnetic resonance imaging (MRI) with multi-detector row computed tomography (MDCT) for the detection of hepatocellular carcinomas (HCCs). Materials: Sixty-two patients (81 HCCs) who underwent MDCT and gadoxetic acid-enhanced MRI using a 3-dimensional volumetric interpolated technique with a mean interval of 7 days (range, 3-11 days) were included in this study. Two observers reached a consensus on 2 sets of images: the gadoxetic acid set (unenhanced, early dynamic, 10-minute, and 20-minute hepatocyte phase images) and the 3-phase MDCT. Diagnostic accuracy and sensitivity were evaluated using the alternative-free response receiver operating characteristic method. Results: There was a trend toward increased area under the receiver operating characteristic curve (Az value) for the gadoxetic acid set (0.963) as compared with the MDCT (0.930), but no significant difference was found (P = 0.41). Sensitivity of the gadoxetic acid set (91.4%) was better than that of the MDCT (71.6%; P = 0.0001). There were 12 lesions that showed only arterial hypervascularization on MDCT but showed arterial hypervascularization and delayed hypointensity on the gadoxetic acid set. Conclusions: Gadoxetic acid-enhanced MRI, including hepatocyte phase imaging, is more sensitive than MDCT for the detection of HCCs.

Detection and characterization of liver metastases: 16-slice multidetector computed tomography versus superparamagnetic iron oxide-enhanced magnetic resonance imaging

The aim of our study was to compare the diagnostic performance of 16--slice multidetector computed tomography with that of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging in the detection of small hepatic metastases and in the differentiation of hepatic metastases from cysts. Twenty-three patients with 55 liver metastases and 14 liver cysts underwent SPIO-enhanced MR imaging and multiphasic CT using 16-MDCT. Two observers independently analyzed each image, in random order. Sensitivity and diagnostic accuracy for lesion detection and differentiation as metastases or cysts for MDCT and SPIO-enhanced MR imaging were calculated using receiver operating characteristic analysis. For all observers, the Az values of SPIO-enhanced MR imaging for lesion detection and differentiation of liver metastases from cysts (mean 0.955, 0.999) were higher than those of MDCT (mean 0.925, 0.982), but not statistically significantly so (P>0.05). Sensitivity of SPIO-enhanced MR imaging with regard to the detection of liver metastases (mean 94.5%) was significantly higher than that of MDCT (mean 80.0%) (P<0.05). SPIO-enhanced MR imaging and 16-MDCT showed similar diagnostic accuracies for detection and differentiation of liver metastases from cysts, but sensitivity of SPIO-enhanced imaging in the detection of liver metastases was superior to that of 16-MDCT.

High resolution MR imaging in patients with symptomatic middle cerebral artery stenosis

PURPOSE High resolution magnetic resonance imaging (HRMRI) has been used as an imaging modality to depict the intracranial artery wall. The aim of this study was to compare images of the vessel wall between symptomatic and asymptomatic atherosclerotic plaques of the middle cerebral artery (MCA) using HRMRI. MATERIALS AND METHODS From September 2009 to August 2010 we prospectively screened consecutive patients for MCA stenosis using time-of-flight (TOF) MR angiography. We studied 14 patients with symptomatic MCA stenosis and 16 patients with asymptomatic MCA stenosis. The HRMRI protocol included three different scans: T1-, T2-, and proton density (PD)-weighted black blood MRI. The cross-sectional images of the MCA wall on HRMRI were compared between the two groups based on the degree of stenosis, remodeling ratio, outward or inward remodeling, plaque signal intensity, plaque surface irregularity, and presence of an intact inner wall. RESULTS The degree of MCA stenosis and the ratio of plaque thickening to patent lumen in the symptomatic group were significantly higher than in the asymptomatic group. Outward remodeling of the stenotic area in symptomatic group was significantly higher than that seen in the asymptomatic group, and the reverse was true for inward remodeling of the stenotic area (it was significantly higher in the asymptomatic group compared to the symptomatic group). T2- and PD-weighted high signal foci, eccentric wall thickening, and plaque volume in the stenotic area were all similar between the two groups. CONCLUSIONS HRMRI has the potential to distinguish between atherosclerotic plaques in symptomatic and asymptomatic MCA stenoses.

High-resolution Magnetic Resonance Imaging of Symptomatic Middle Cerebral Artery Dissection

Dissection of the middle cerebral artery (MCA) is less frequent compared with dissection of vessels in the vertebrobasilar system or dissection of the carotid artery. High-resolution cross-sectional magnetic resonance imaging (HRMRI) has emerged as a potential technique for atherosclerotic plaque imaging in MCA. We enrolled 3 patients with MCA dissection on whom HRMRI was performed for evaluation of MCA stenosis. Two patients had an embolic infarction in the MCA territory and focal dissection. One patient had a massive infarction in the MCA territory and long-segment dissection of the MCA. On HRMRI, our objectives had an intimal flap with patency of the lumen and 1 had extensive hemorrhaging in the false lumen.

Effectiveness of MR imaging for diagnosing the mild forms of acute pancreatitis: Comparison with MDCT

To assess the usefulness of MRI and determine which MR sequence is most effective for diagnosing the mild forms of acute pancreatitis.

Detection of intracranial aneurysms using three-dimensional multidetector-row CT angiography: is bone subtraction necessary?

PURPOSE The aim of this study was to evaluate the usefulness of three-dimensional CT angiography (3D CTA) with bone subtraction in a comparison with 3D CTA without bone subtraction for the detection of intracranial aneurysms. MATERIALS AND METHODS Among 337 consecutive patients who had intracranial aneurysms detected on 3D CTA, 170 patients who underwent digital subtraction angiography (DSA) were included in the study. CTA was performed with a 16-slice multidetector-row CT (MDCT) scanner. We created the 3D reconstruction images with and without bone subtraction by using the volume rendering technique. Three neuroradiologists in a blinded fashion interpreted both 3D CTA images with and without bone subtraction. The diagnostic accuracy of both techniques was evaluated using the alternative free-response receiver operating characteristic (ROC) analysis. The sensitivity and positive predictive value were also evaluated. RESULTS A total of 200 aneurysms (size: 2-23 mm) were detected in 170 patients. The area under the receiver operating characteristic curve (Az) for 3D CTA with bone subtraction (mean, Az=0.933) was significantly higher than that for 3D CTA without bone subtraction (mean, Az=0.879) for all observers (P<0.05). The sensitivity of 3D CTA with bone subtraction for three observers was 90.0, 92.0 and 92.5%, respectively, while the sensitivity of 3D CTA without bone subtraction was 83.5, 83.5 and 87.5%, respectively. No significant difference in positive predictive value was observed between the two modalities. CONCLUSIONS 3D CTA with bone subtraction showed significantly higher diagnostic accuracy for the detection of intracranial aneurysms as compared to 3D CTA without bone subtraction.

Association of Intraplaque Hemorrhage and Acute Infarction in Patients With Basilar Artery Plaque

Background and Purpose— High-resolution magnetic resonance imaging (HRMRI) is ideal for serial examination of diseased arterial walls because it is noninvasive and has superior capability of discriminating tissue characteristics. The aim of this study is to evaluate the prevalence and clinical relevance of intraplaque hemorrhage (IPH) in patients with basilar artery (BA) atherosclerosis using HRMRI. Methods— We analyzed HRMRI and clinical data from 74 patients (45 symptomatic and 29 asymptomatic), all of whom had >50% BA stenosis. High-signal intensity within a BA plaque on magnetization-prepared rapid acquisition with gradient-echo was defined as an area with an intensity that was >150% of the signal from the adjacent muscle. The relationship between IPH within a BA plaque region and clinical presentation was analyzed. Results— Thirty patients were positive for IPH on HRMRI (42.3%, 24 symptomatic and 6 asymptomatic). Symptomatic lesions in the MR-positive IPH group were significantly more prevalent than in the MR-negative group (80.0% versus 48.8%; P<0.01). Also, MR-predicted IPH was significantly more prevalent in the high-grade stenosis group (P<0.001) than in the low-grade group. The relative risk of an acute focal stroke event among patients who were magnetization-prepared rapid acquisition with gradient-echo–positive for IPH compared with patients who were magnetization-prepared rapid acquisition with gradient-echo–negative was 1.64. Conclusions–– IPH within a BA plaque region on HRMRI is highly prevalent and is associated with acute stroke.

Manual aspiration thrombectomy using the Penumbra catheter in patients with acute M1 occlusion: A single-center study.

Purpose The efficacy and safety of aspiration thrombectomy using Penumbra in acute occlusion of intracranial artery have been proved in many previous studies. Our study aimed to retrospectively assess the efficacy and safety of a manual aspiration thrombectomy using Penumbra in patients with M1 occlusion. Materials and methods We conducted a retrospective review of 70 patients who underwent manual aspiration thrombectomy using Penumbra catheters for treatment of M1 occlusion between January 2012 and December 2014. We evaluated immediate angiographic results and clinical outcomes through review of patient electronic medical records. Results Male was the dominant sex in this study (M:F = 38:32) and median age was 72 (age range, 36–91). The rate of successful recanalization (TICI grade ≥2 b) was 91.4% (64/70). The successful recanalization rate by single Penumbra was 82.9% (58/70). Six patients were treated in combination with Solitaire stent. Median NIHSS score was 11 (range, 4–20) at admission and was 3 (range 0–23) at discharge. Favorable clinical outcomes (mRS score at three months ≤2) were seen in 42 patients (60%). Two patients were observed to have subarachnoid hemorrhage after the procedure. Another two patients died related to massive symptomatic hemorrhage, brain edema and herniation in the hospital. Conclusion Manual aspiration thrombectomy appears to be safe and is capable of achieving a high rate of successful recanalization and favorable clinical outcomes in patients with M1 occlusion.

Intra-Individual, Inter-Vendor Comparison of Diffusion-Weighted MR Imaging of Upper Abdominal Organs at 3.0 Tesla with an Emphasis on the Value of Normalization with the Spleen

Objective To compare the apparent diffusion coefficient (ADC) values of upper abdominal organs with 2 different 3.0 tesla MR systems and to investigate the usefulness of normalization using the spleen. Materials and Methods Forty-one patients were enrolled in this prospective study, of which, 35 patients (M:F, 27:8; mean age ± standard deviation, 62.3 ± 12.3 years) were finally analyzed. In addition to the routine liver MR protocol, single-shot spin-echo echo-planar diffusion-weighted imaging using b values of 0, 50, 400, and 800 s/mm2 in 2 different MR systems was performed. ADC values of the liver, spleen, pancreas, kidney and liver lesion (if present) were measured and analyzed. ADC values of the spleen were used for normalization. The Pearson correlation, Spearman correlation, paired sample t test, Wilcoxon signed rank test and Bland-Altman method were used for statistical analysis. Results For all anatomical regions and liver lesions, both non-normalized and normalized ADC values from 2 different MR systems showed significant correlations (r = 0.5196–0.8488). Non-normalized ADC values of both MR systems differed significantly in all anatomical regions and liver lesions (p < 0.001). However, the normalized ADC of all anatomical regions and liver lesions did not differ significantly (p = 0.065–0.661), with significantly lower coefficient of variance than that of non-normalized ADC (p < 0.009). Conclusion Normalization of the abdominal ADC values using the spleen as a reference organ reduces differences between different MR systems, and could facilitate consistent use of ADC as an imaging biomarker for multi-center or longitudinal studies.

Retropharyngeal spindle cell/pleomorphic lipoma.

Spindle cell/pleomorphic lipoma is an uncommon benign adipose tissue tumor most frequently arising from the subcutaneous tissue of the back, shoulder, head and neck, and extremities. The deep cervical spaces are the rarely affected locations. Herein we report on the imaging findings of spindle cell/pleomorphic lipoma involving the retropharyngeal space in an elderly woman.