Unenhanced T1-weighted Images Research Articles

Magnetic resonance imaging-detected inner ear hemorrhage as a potential cause of sudden sensorineural hearing loss

PurposeThe aim of this study is to assess the value of magnetic resonance imaging in identifying the etiology of sudden sensorineural hearing loss, and to correlate the high signals in the labyrinth with clinical features to identify if inner ear hemorrhage could be implicated. Materials and methodsIn this retrospective study, inner ear magnetic resonance imaging was given to 112 patients with sudden sensorineural hearing loss in the First Affiliated Hospital of Sun Yat-sen University from 2011 to 2012. The clinical features of patients with high signals in the labyrinth on magnetic resonance imaging were analyzed. ResultsAbnormal magnetic resonance images were identified in 13 (11.6%) patients. Retrocochlear pathology was found in six patients, including two cases of lacunar infarction, one case of multiple ischemias in the brainstem and bilateral centrum semiovale, two cases of acoustic neuroma, and one case of inner ear hemangioma. There were seven cases showing high signals in the labyrinth on unenhanced T1-weighted and fluid-attenuated inversion recovery images. Clinical features of these seven patients were characterized by irreversible profound hearing impairment and vestibular dysfunction. These findings were consistent with the hypothesis that their symptoms were caused by an inner ear hemorrhage. ConclusionThe results indicate the importance of magnetic resonance imaging in sudden sensorineural hearing loss in patients. Moreover, patients with vestibular dysfunction and sudden profound hearing loss may have an inner ear hemorrhage evident by interpreting clinical and magnetic resonance imaging results.

Vascular Remodeling and Plaque Vulnerability in a Rabbit Model of Atherosclerosis: Comparison of Delayed-Enhancement MR Imaging with an Elastin-specific Contrast Agent and Unenhanced Black-Blood MR Imaging

To compare delayed-enhancement (DE) magnetic resonance (MR) imaging with an elastin-specific contrast agent and unenhanced black-blood (BB) MR imaging with regard to vessel wall delineation and assessment of vascular remodeling and to test the prospective value for predicting plaque disruption in a rabbit model of atherosclerosis. All procedures were approved by the animal ethics committee. Atherosclerosis was induced in 14 New Zealand White rabbits by means of a 1% cholesterol diet and endothelial denudation. Plaque disruption was triggered with Russell's viper venom and histamine. Animals with atherosclerosis were imaged before triggering to identify plaques and vascular remodeling and after triggering to identify thrombus. Plaques were classified as nondisrupted (stable) or disrupted (vulnerable). Control rabbits fed a regular diet were imaged twice. Unenhanced T1-weighted BB MR imaging, DE MR imaging with an elastin-specific contrast agent, and T1 mapping were used to assess vascular remodeling and calculate the plaque area and vessel wall relaxation rate (R1 = 1/T1). Elastin was quantified by using elastica-van Gieson stain. Group comparisons were analyzed with the Mann-Whitney or paired t test. Agreement between methods was performed with Bland-Altman analysis. Unenhanced T1-weighted BB MR imaging and DE MR imaging showed that, compared with nondisrupted plaques, disrupted plaques had larger plaque area (T1-weighted BB MR imaging: 5.1 mm(2) vs 5.7 mm(2); DE MR imaging: 6.0 mm(2) vs 7.9 mm(2); P < .001) and vessel area (T1-weighted BB MR imaging: 11.8 mm(2) vs 14.3 mm(2); DE MR imaging: 10.8 mm(2) vs 13.9 mm(2); P < .001) and underwent positive remodeling. Assessment of positive remodeling with DE MR imaging enabled better prediction of plaque disruption compared to that with unenhanced T1-weighted BB imaging (sensitivity: 83.7% vs 58.1%). DE MR imaging showed a stronger agreement with histologic findings, whereas the vessel area was overestimated with unenhanced T1-weighted BB imaging. Compared with unenhanced T1-weighted BB MR imaging, DE MR imaging with an elastin-specific contrast agent enables more accurate assessment of vascular remodeling in the prediction of vulnerable plaque.

High Signal Intensity in the Dentate Nucleus and Globus Pallidus on Unenhanced T1-weighted MR Images: Relationship with Increasing Cumulative Dose of a Gadolinium-based Contrast Material

To explore any correlation between the number of previous gadolinium-based contrast material administrations and high signal intensity (SI) in the dentate nucleus and globus pallidus on unenhanced T1-weighted magnetic resonance (MR) images. The institutional review board approved this study, waiving the requirement to obtain written informed consent. A group of 381 consecutive patients who had undergone brain MR imaging was identified for cross-sectional analysis. For longitudinal analysis, 19 patients who had undergone at least six contrast-enhanced examinations were compared with 16 patients who had undergone at least six unenhanced examinations. The mean SIs of the dentate nucleus, pons, globus pallidus, and thalamus were measured on unenhanced T1-weighted images. The dentate nucleus-to-pons SI ratio was calculated by dividing the SI in the dentate nucleus by that in the pons, and the globus pallidus-to-thalamus SI ratio was calculated by dividing the SI in the globus pallidus by that in the thalamus. Stepwise regression analysis was undertaken in the consecutive patient group to detect any relationship between the dentate nucleus-to-pons or globus pallidus-to-thalamus SI ratio and previous gadolinium-based contrast material administration or other factors. A random coefficient model was used to evaluate for longitudinal analysis. The dentate nucleus-to-pons SI ratio showed a significant correlation with the number of previous gadolinium-based contrast material administrations (P < .001; regression coefficient, 0.010; 95% confidence interval [CI]: 0.009, 0.011; standardized regression coefficient, 0.695). The globus pallidus-to-thalamus SI ratio showed a significant correlation with the number of previous gadolinium-based contrast material administrations (P < .001; regression coefficient, 0.004; 95% CI: 0.002, 0.006; standardized regression coefficient, 0.288), radiation therapy (P = .009; regression coefficient, -0.014; 95% CI: -0.025, -0.004; standardized regression coefficient, -0.151), and liver function (P = .031; regression coefficient, 0.023; 95% CI: 0.002, 0.044; standardized regression coefficient, 0.107). The dentate nucleus-to-pons and globus pallidus-to-thalamus SI ratios in patients who had undergone contrast-enhanced examinations were significantly greater than those of patients who had undergone unenhanced examinations (P < .001 for both). High SI in the dentate nucleus and globus pallidus on unenhanced T1-weighted images may be a consequence of the number of previous gadolinium-based contrast material administrations.

Ectopic pancreas in upper gastrointestinal tract: MRI findings with emphasis on differentiation from submucosal tumor

Ectopic pancreas can frequently be mistaken for other submucosal masses. Ectopic pancreas may follow the signal intensity of mother pancreas on various magnetic resonance (MR) sequences, which might be helpful for differentiation between ectopic pancreas and other submucosal tumors in upper gastrointestinal (UGI) tract. To evaluate the value of MR imaging (MRI) in differentiating ectopic pancreases from submucosal tumors in UGI tract. Fifteen patients with ectopic pancreas and 26 patients with UGI submucosal tumors were included. All patients underwent abdominal MRI with diffusion-weighted imaging (DWI) and gadoxetic acid-enhanced MRI. Qualitative (location, contour, growth pattern, lesion border, and presence of intralesional cystic portion and duct-like structure) and quantitative (long diameter [LD], short diameter [SD], LD/SD ratio, signal intensities and apparent diffusion coefficients [ADC], and signal intensity - and ADC ratios of UGI submucosal lesions to pancreas) parameters were compared between ectopic pancreases and UGI submucosal tumors using Fisher's exact test, the Mann-Whitney U test, and receiver-operating characteristic (ROC) analysis. Duodenum was the most common location for ectopic pancreas (12/15, 79.9%), and the gastric body for UGI submucosal tumors (15/26, 57.7%) (P = 0.005). Round shape was an imaging feature more common in UGI submucosal tumors (12/26, 46.2%) than in ectopic pancreas (1/15, 6.7%; P = 0.021). On all of the various pulse sequences of MR images, ectopic pancreas showed isointensity comparable to that of pancreas more frequently than did sequences of UGI submucosal tumors (P < 0.01).The means (0.95 ± 0.09, 0.99 ± 0.06, 1.07 ± 0.08) of the signal intensity ratio of ectopic pancreas to pancreas on fat-suppressed unenhanced T1-weighted, arterial, and portal phase images were significantly higher than those (0.60 ± 0.09, 0.62 ± 0.28, 0.86 ± 0.27) of UGI submucosal tumors (P < 0.05). In contrast, the means (1.05 ± 0.12, 0.93 ± 0.18) of the signal intensity ratios of ectopic pancreas on T2-weighted images and DW images (b = 800 s/mm(2)) were significantly lower than those (1.82 ± 0.39, 2.35 ± 0.94) of UGI submucosal tumors (P < 0.001). On ROC analysis, if absolute value of difference between 1.0 and signal intensity ratio of submucosal lesions to the pancreas on T1-weighted images is <0.21, the sensitivity and specificity reach 100.0% for diagnosis ectopic pancreas from submucosal tumors. Abdominal MRI with DWI can be a valuable tool for differentiating ectopic pancreases from UGI submucosal tumors.

Performance of Spin-Echo and Gradient-Echo T1-Weighted Sequences for Evaluation of Dural Venous Sinus Thrombosis and Stenosis

Dural venous sinus abnormalities are clinically important but can potentially be overlooked using various MRI techniques. This study evaluates the diagnostic accuracy of spin-echo (SE) T1-weighted imaging, 3D gradient-recalled echo (GRE) T1-weighted imaging, and contrast-enhanced MR venography (MRV) for the detection of dural venous sinus thrombosis and transverse sinus (TS) stenosis. Seventy-three patients underwent MRI evaluation with unenhanced and contrast-enhanced axial SE T1-weighted imaging, contrast-enhanced sagittal 3D GRE T1-weighted imaging, and contrast-enhanced MRV sequences. Three neuroradiologists each evaluated these 219 total datasets in a randomized blinded fashion for the presence or absence of TS stenosis and for dural venous sinus thrombosis in each of 10 venous sinus segments (730 total segments). Diagnostic performance characteristics and kappa statistics were calculated for each technique. Thirteen patients (37 segments) had suspected dural venous sinus thrombosis by one or more readers; of those 13 patients, nine (23 segments) were thought to have definite thrombosis on contrast-enhanced MRV. Compared with contrast-enhanced MRV, the positive predictive value (PPV) and negative predictive value (NPV) for thrombosis were 60% and 97%, respectively, for both unenhanced and contrast-enhanced SE T1-weighted imaging and 100% and 98% for 3D GRE T1-weighted imaging. Kappa values calculated per venous segment were as follows: 0.41 for SE T1-weighted imaging, 0.72 for 3D GRE T1-weighted imaging, and 0.95 for contrast-enhanced MRV. Thirty patients (58 segments) had TS stenosis suspected by one or more readers; of those 30 patients, TS stenosis was deemed to be definite on contrast-enhanced MRV in 25 patients (50 segments). Compared with contrast-enhanced MRV, the PPV and NPV were 75% and 80%, respectively, for SE T1-weighted imaging and 91% and 92% for 3D GRE T1-weighted imaging for the detection of stenosis. Kappa values calculated per patient were -0.038 for SE T1-weighted imaging, 0.58 for 3D GRE T1-weighted imaging, and 0.98 for contrast-enhanced MRV. Contrast-enhanced 3D GRE T1-weighted imaging is superior to SE T1-weighted imaging for the detection of dural venous sinus thrombosis and TS stenosis but does not substitute for dedicated MRV. Hyperintensity on unenhanced SE T1-weighted imaging is unreliable for the detection of dural venous sinus thrombosis.

Rectal gastrointestinal stromal tumors: Imaging features with clinical and pathological correlation

To investigate computed tomography (CT) and magnetic resonance imaging (MRI) manifestations of rectal gastrointestinal stromal tumors (GISTs) in order to enhance the recognition of these rare tumors. Fourteen patients with pathologically proven rectal GISTs were retrospectively reviewed. Patient histories were retrospectively reviewed for patient age, gender, presenting symptoms, endoscopic investigations, operation notes and pathologic slides. All tumors were evaluated for CD117, CD34 expression, and the tumors were stratified according to current criteria of the National Institutes of Health (NIH). In all cases the first pre-operation imaging findings (CT and MRI, n = 3; MRI only, n = 8; CT only, n = 3) were analyzed by two experienced radiologists by consensus, which include: tumor size, shape, CT density (hypodense, isodense and hyperdense), MRI signal intensity (hypointense, isointense and hyperintense), epicenter (intraluminal or extraluminal), margin (well-defined or ill-defined), internal component (presence of calcifications, necrosis, hemorrhage or ulceration), pattern and degree of enhancement, invasion into adjacent structures. After review of the radiologic studies, clinical and pathological findings were correlated with radiological findings. The patients, 13 men and 1 woman, were aged 31-62 years (mean = 51.5 ± 10.7 years). The most common initial presentation was hematochezia (n = 6). The mean tumor diameter was 5.68 ± 2.64 cm (range 1.5-11.2 cm). Eight lesions were round or oval, and 6 lesions were irregular. Eleven lesions were well-defined and 3 had ill-defined margins. Ten tumors were extraluminal and 4 were intraluminal. The density and MR signal intensity of the solid component of the lesions were similar to that of muscle on unenhanced CT (n = 6) and T1-weighted images (n = 11), and hyperintense on T2-weighted MR images. Calcification was detected in 2 tumors. Following intravenous injection of contrast media, 3 lesions had mild enhancement and 11 lesions had moderate enhancement. Enhancement was homogenous in 3 lesions and heterogeneous in 11. In 1 of 11 patients who underwent both CT and MRI, the tumor was homogenous on CT scan and heterogeneous on MRI. Eight patients were classified as high risk according to the modified recurrent risk classification system of NIH. Rectal GISTs usually manifest as large, well-circumscribed, exophytic masses with moderate and heterogeneous enhancement on CT and MRI. The invasion of adjacent organs, bowel obstruction and local adenopathy are uncommon.

Suggestive MR features of Whartin’s tumor with correlation between diffusion-weighted imaging and pathology

A 54-year-old man without medical history presented with a right-sided tumor of the parotid gland. The consistency of the mass was soft. The patient was asymptomatic except for the self-palpation of the process. He had unremarkable clinical examination including neck nodal areas. The ‘conventional’ MRI examination gave significant clues for the diagnosis (Fig. A). The neoplasm displayed elevated signal intensity on unenhanced T1-weighted images (A) suggesting a colloid content and enhanced only slightly after paramagnetic contrast agent (CA) perfusion (B), which is a valuable criterion to distinguish it from other common benign (pleiomorphic adenoma) and malignant (carcinomas) neoplasms of the parotid gland which usually exhibit strong heterogeneous enhancement. Low contrast-enhancement was confirmed by subtracting pre- and post-contrast T1-weighted images (C).

Biliary Complications after Liver Transplantation: Addition of T1-weighted Images to MR Cholangiopancreatography Facilitates Detection of Cast in Biliary Cast Syndrome

To evaluate the diagnostic performance of T2-weighted magnetic resonance (MR) cholangiopancreatography pulse sequences in comparison with MR cholangiopancreatography sequences combined with nonenhanced T1-weighted images in the detection of biliary cast syndrome in liver transplant recipients. This retrospective study was conducted in accordance with the declaration of Helsinki. Institutional review board approval was obtained. MR images in 95 patients who were examined after liver transplantation and who presented with symptoms of biliary obstruction were examined. Two separate sets of images, MR cholangiopancreatograms and MR cholangiopancreatograms plus T1-weighted images, were evaluated independently by three readers. Sensitivities, specificities, and positive and negative predictive values for biliary cast syndrome were calculated, and receiver operating characteristic curves were generated. The results of endoscopic retrograde cholangiopancreatography served as the reference standard. To determine interobserver agreement, κ values were calculated. Cast appeared hyperintense on nonenhanced T1-weighted images. Sensitivities for T2-weighted MR cholangiopancreatography data alone were 0.65, 0.70, and 0.55 for the three readers. Adding unenhanced T1-weighted images resulted in sensitivities of 0.95, 0.90, and 0.90, respectively. Specificities for MR cholangiopancreatography alone and for MR cholangiopancreatography plus T1-weighted images were high on average (0.98, 0.97, and 0.97 vs 1.0 for all readers, respectively). Interobserver agreement was good for T2-weighted MR cholangiopancreatography (κ for readers 1 and 2 = 0.589, κ for readers 2 and 3 = 0.593, κ for readers 1 and 3 = 0.734) and was excellent for MR cholangiopancreatography plus T1-weighted images (κ for readers 1 and 2 = 0.806, κ for readers 2 and 3 = 0.881, κ for readers 1 and 3 = 0.848). The combination of T2-weighted MR cholangiopancreatography and T1-weighted imaging yields higher diagnostic performance than MR cholangiopancreatography alone. Therefore, readers evaluating liver MR images with regard to biliary complications after liver transplantation should also look at the bile ducts on unenhanced T1-weighted images, as biliary cast might be more easily depicted on these images.

Is Gadoxetate Disodium–Enhanced MRI Useful for Detecting Local Recurrence of Hepatocellular Carcinoma After Radiofrequency Ablation Therapy?

The purpose of our study was to determine whether gadoxetate disodium-enhanced MRI improves the detection of locally recurrent hepatocellular carcinoma (HCC) after radiofrequency ablation therapy. Forty-two consecutive patients (26 men and 16 women; mean age, 70.9 years) who had undergone radiofrequency ablation therapy for HCC were examined by gadoxetate disodium-enhanced MRI. Three independent radiologists reviewed two sets of MR images separately. Set 1 contained unenhanced T1-weighted, T2-weighted, and contrast-enhanced extracellular phase images, and set 2 contained unenhanced T1-weighted, T2-weighted, and contrast-enhanced extracellular and hepatocyte phase images. Diagnostic accuracies were determined by receiver operating characteristic (ROC) curve analysis. Of the 61 ablated lesions included, 10 developed local recurrence and 51 did not. Sensitivity (60-80% and 70-80% for sets 1 and 2, respectively), specificity (90-98% and 92-100%), and accuracy (87-95% and 89-97%) were not improved by adding hepatocyte phase images. Rather, mean area under the ROC curve (AUC) significantly decreased from 0.94 for set 1 to 0.82 for set 2 (p = 0.046), and the AUC of the radiologist with the least experience significantly decreased from 0.91 to 0.75 (p = 0.037). For gadoxetate disodium-enhanced MRI, the detection of local recurrence of HCC after radiofrequency ablation therapy was not found to be improved by including hepatocyte phase images. Furthermore, detection may be further impaired when a less-experienced radiologist interprets the images.

MRI of fat necrosis of the breast: The “black hole” sign at short tau inversion recovery

To describe MRI features of fat necrosis of the breast. Twenty-five lesions in 16 patients were retrospectively analyzed. MRI was performed due to equivocal findings at conventional imaging after surgical treatment of cancer (n=14) or during anticoagulant therapy (n=1), after focal mastitis treated with ductal resection (n=1). In the 15 patients with previous surgery MRI was performed after a median interval of 24 months, using short tau inversion recovery (STIR) and contrast-enhanced dynamic T1-weighted sequences. Signal-to-noise ratio (SNR) inside the lesion and surrounding healthy fat was calculated on both STIR and unenhanced T1-weighted images. Maximal lesion diameter was measured on STIR images. All lesions had final clinical and imaging assessment in favor of fat necrosis and negative clinical and imaging follow-up (21-40 months; median 24 months). At STIR sequence, fat necrosis appeared as a "black hole", being markedly hypointense (median SNR=29) compared with surrounding fat (median SNR=95) (P<0.001), while no significant difference was found at unenhanced T1-weighted sequence. No significant correlation with time from treatment was found. Of 25 lesions, 15 showed ring enhancement, with continuous increase (n=10), plateau (n=2), or wash-out curve (n=3). The 11 enhancing lesions in the 8 patients with previous radiation therapy showed an initial enhancement higher than that of the 4 enhancing lesions in the 2 patients who did not, although the difference was not significant (P=0.104). Fat necrosis of the breast exhibits a "black hole" sign on STIR images, allowing for an easier diagnosis in clinical practice.

MR imaging in diffuse-type hepatocellular carcinoma with synchronous portal vein thrombi

Diffuse or continuous multifocal tumors with accompanying portal vein thrombosis yield considerable changes in the magnetic resonance imaging findings of hepatocellular carcinoma. The overlapped imaging findings of these two co-existing pathologies may be confusing. We aimed to evaluate the magnetic resonance imaging findings of widespread hepatocellular carcinoma lesions complicated with portal vein thrombosis. Twenty-two patients (20 male, 2 female; mean age: 57 years) with portal vein thrombosis and diffuse-type hepatocellular carcinoma who underwent contrast-enhanced hepatic magnetic resonance imaging in our department between August 2001 and November 2008 were evaluated retrospectively. The unenhanced axial T1-weighted, T2-weighted, and post-contrast early- and late-phase images were reviewed in each patient. On T2-weighted magnetic resonance images, tumors were seen mildly hyperintense in 11 patients and heterogeneously hyperintense in 11 patients. Unenhanced T1-weighted images demonstrated homogeneous hypointensity in 15 patients and heterogeneous hypointensity in 7 patients. Post-contrast early-phase magnetic resonance images showed patchy enhancement in 12 patients, moth-eaten enhancement in 6 patients, strong enhancement in 1 patient, and minimal enhancement in 3 patients. Post-contrast late-phase magnetic resonance images demonstrated heterogeneous washout in all patients. Portal vein thrombosis was present in all patients. The mean diameter of main portal vein thrombi was 27 mm (range: 25-30 mm). Serum alpha-fetoprotein levels were elevated in all patients. In patients with chronic parenchymal liver disease, when portal vein thrombosis and high serum alpha-fetoprotein values co-exist, careful attention must be paid to the hepatic parenchymal changes, especially on contrast-enhanced images, in order to not overlook diffuse-type hepatocellular carcinoma.

Characterization of hyperintense nodules on T1-weighted liver magnetic resonance imaging: Comparison of Ferucarbotran-enhanced MRI with accumulation-phase FS-T1WI and gadolinium-enhanced MRI

Background T1-weighted (T1W) hyperintense nodules against a background of cirrhosis are diagnostically challenging in daily practice. All regenerative nodules, dysplastic nodules and hepatocellular carcinoma (HCC) might present hyperintense on T1W imaging (T1WI), so T1W hyperintense nodules cannot be definitively characterized as dysplastic nodules or HCC before biopsy, resection or transplantation. The purpose of our study was to evaluate Ferucarbotran-enhanced Magnetic Resonance Imaging (MRI) with accumulation-phase fat suppression T1-weighted imaging (FS-T1WI) in comparison with gadolinium-enhanced MRI for characterization of hyperintense nodules on unenhanced T1WI within cirrhotic liver. Methods Two separate groups of patients with histologically-proven T1W hyperintense nodule on MRI were retrospectively identified. The Ferucarbotran group consisted of 17 T1W hyperintense nodules in 12 patients. The gadolinium group consisted of 22 T1W hyperintense nodules in 21 patients. All of the patients had liver cirrhosis. Finally, 11 HCC nodules, and six benign nodules were included in the Ferucarbotran group; 15 HCC nodules and seven benign nodules were included in the gadolinium group. Results With the conventional criteria, in the gadolinium-enhanced group, the sensitivity, specificity, and accuracy were 53%, 100%, and 73%, respectively. Using the conventional criteria in the Ferucarbotran group, the sensitivity, specificity, and accuracy were 73%, 100%, 82%, respectively. Using the conventional criteria plus hyperintense on the accumulation-phase FS-T1WI in the Ferucarbotran group for characterization of the T1W hyperintense nodules, the sensitivity, specificity, and accuracy were 100%, 83%, 94%, respectively. The sensitivity of Ferucarbotran-enhanced MR with accumulation-phase FS-T1WI was better than that of gadolinium-enhanced MRI ( p = 0.01). Conclusion Ferucarbotran-enhanced MRI with accumulation-phase FS-T1WI is superior to gadolinium-enhanced MRI in characterization of T1W hyperintense nodules within cirrhotic liver. T1W hyperintense nodule within cirrhotic liver depicting hyperintense on Ferucarbotran-enhanced accumulation-phase FS-T1WI should be investigated aggressively.

MR Imaging Features of Small Solid Pseudopapillary Tumors: Retrospective Differentiation From Other Small Solid Pancreatic Tumors

The purpose of this study was to describe the MRI features of small solid pseudopapillary tumors useful for differentiating these tumors from other small solid pancreatic tumors. Forty-five patients (18 men, 27 women; mean age, 59 ± 11.7 years) with 45 solid pancreatic tumors smaller than 3 cm in diameter registered from 2000 to 2009 were included. Twenty-two of the tumors were adenocarcinomas, 12 were endocrine tumors, and 11 were solid pseudopapillary tumors. Two radiologists analyzed the MR images for morphologic features, signal intensity of the lesion on unenhanced images, and dynamic enhancement pattern. The contrast-to-noise ratio between the lesion and the pancreas was calculated on T1- and T2-weighted images and on dynamic images. Solid pseudopapillary tumors commonly had the following features: completely well-defined margin (82%), pure solid consistency (82%), low signal intensity on unenhanced T1-weighted images (100%), high signal intensity on T2-weighted images (100%), a strong predominance among women (91%), and early heterogeneous and slowly progressive enhancement (100%). The solid pseudopapillary tumors rarely had a capsule or hemorrhage. A characteristic qualitative feature of solid pseudopapillary tumors that was significantly different from the other two tumor types was very high signal intensity on T2-weighted images (p < 0.01). Quantitative analysis showed that the solid pseudopapillary tumors had a lower contrast-to-noise ratio (-16.82 ± 5.84) on T1-weighted images and a higher contrast-to-noise ratio (37.35 ± 33.59) on T2-weighted images than did the other two tumor types (p < 0.01). Small solid pseudopapillary tumors were predominantly seen as completely well-demarcated pure solid tumors in middle-aged women. They had lower signal intensity on T1-weighted images and higher signal intensity on T2-weighted images than did the other two tumor types and had early heterogeneous and progressive enhancement.

Hyperintense Dentate Nucleus on Unenhanced T1-weighted MR Images Is Associated with a History of Brain Irradiation

To assess the frequency of hyperintensity in the dentate nucleus on T1-weighted magnetic resonance (MR) images and to establish correlations between such hyperintensity and clinical factors, including a history of brain irradiation. This study was approved by the institutional review board, and each patient provided written informed consent. Three hundred sixty-two patients (164 men, 198 women; mean age, 62 years) were evaluated. Unenhanced T1-weighted MR images were obtained by using a spin-echo sequence at 3.0 T. Two neuroradiologists, who were blinded to clinical data, independently evaluated the signal intensity of the dentate nucleus compared with the signal intensity of the central white matter of the cerebellum by using a four-point graded response scale (grade 4 indicated prominent hyperintensity; grade 3, faint hyperintensity; grade 2, isointensity; and grade 1, hypointensity). Backward stepwise regression analysis was used to evaluate the relationship between signal intensity grades and the following clinical factors: sex, age, the interaction between age and sex, hypertension, dyslipidemia, diabetes mellitus, liver dysfunction, brain infarction, brain tumor, spinocerebellar degeneration, multiple sclerosis, a history of chemotherapy, and a history of brain irradiation. T1-hyperintense dentate nuclei were present in 41 (11%) of the 362 patients. Of these 41 patients, 31 (76%) had a history of brain irradiation. Signal intensity grade of the dentate nucleus on T1-weighted MR images correlated significantly with a history of brain irradiation (P < .001) but no other clinical factor. A hyperintense dentate nucleus may be seen on unenhanced T1-weighted MR images in some patients and may be associated with a history of brain irradiation.

Assessment of Scaphoid Viability With MRI: A Reassessment of Findings on Unenhanced MR Images

The purpose of this article is to evaluate the accuracy of unenhanced T1-weighted MR images in predicting the vascular status of the proximal pole of the scaphoid in patients with chronic scaphoid fracture nonunions. A database search identified 29 patients with chronic scaphoid nonunions who underwent a preoperative MRI examination and intraoperative assessment of scaphoid viability from 2004 to 2009. T1-weighted MR images were evaluated by two musculoskeletal radiologists. If the proximal pole demonstrated diffusely decreased T1-weighted signal (less than or equal to that of skeletal muscle), the patient was placed in a moderate-to-high risk for avascular necrosis (AVN) category. Otherwise, the patient was placed in a viable-to-low risk for AVN category. Scaphoid viability or necrosis was diagnosed intraoperatively depending on whether punctate bleeding was present. After the patients were classified according to the T1-weighted appearance, the appearance on STIR images was recorded. There were 29 patients (25 male) with a mean age of 21 years. When we compared the MRI results, using only the T1-weighted images, with the surgical findings, unenhanced MRI had a sensitivity, specificity, and accuracy of 55%, 94%, and 79%, respectively, for diagnosing AVN. Increased proximal pole STIR signal was noted with similar frequencies in patients with and without AVN. T1-weighted unenhanced MRI is an acceptable alternative to delayed contrast-enhanced MRI in the preoperative assessment of the vascular status of the proximal pole of the scaphoid in patients with chronic fracture nonunions. STIR images were not beneficial in determining proximal pole viability.

Preoperative detection of prostate cancer: A comparison with 11C‐choline PET, 18F‐fluorodeoxyglucose PET and MR imaging

To compare (11)C-choline positron emission tomography (C-PET), (18)F-fluorodeoxyglucose PET (FDG-PET), and MR imaging in the preoperative detection of prostate cancer. C-PET, FDG-PET, and MR images were obtained in 43 consecutive patients with suspected prostate cancer, and prostate cancers were histopathologically confirmed in 26 patients. Unenhanced T1-weighted, T2-weighted, and gadolinium-enhanced MR images were obtained. C-PET and FDG-PET were conducted 1.5 and 60 minutes after injection of 5.5 and 5.0 MBq/kg tracers, respectively. A nuclear and a genitourinary radiologist retrospectively reviewed PET and MR images at random, respectively, and assigned a confidence level for the presence of prostate cancer using a four-point scale. Diagnostic performance was tested using the McNemar test and receiver operating characteristic curve analysis. The sensitivity was greater (P < 0.05) with MR (88%) and C-PET (73%) images than with FDG-PET images (31%). The accuracy was greater (P < 0.05) with MR images (88%) than with C-PET (67%) and FDG-PET (53%) images. The area-under-curve value with MR (0.90) was greater than those with C-PET (0.53) and FDG-PET (0.54) images (P < 0.01). MR imaging should be primarily performed in the preoperative detection of prostate cancer. C-PET and FDG-PET did not improve the detection.

T2-Weighted Magnetic Resonance Imaging of the Liver

To evaluate the effect of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) on T2-weighted magnetic resonance imaging of liver parenchyma. Forty-six patients with suspected hepatic tumors (group 1) underwent breath-hold T2-weighted fast spin echo imaging before and after 4 minutes of Gd-EOB-DTPA enhancement. Visual assessment and signal intensity (SI) measurements were performed to evaluate the effects of Gd-EOB-DTPA on the T2-weighted images of the liver. Thirteen healthy volunteers (Group 2) who underwent magnetic resonance imaging before and after 35 minutes of Gd-EOB-DTPA enhancement were also evaluated. In the qualitative analysis, visual SI of hepatic vessels after enhancement was significantly higher than that before enhancement (P < 0.001) in group 1, although there was no significant difference in the visual SI of liver parenchyma between before and after enhancement. In the quantitative analysis, SI ratio of liver parenchyma on enhanced images was significantly higher than that on unenhanced images (P < 0.001) in group 1. Conversely, the SI ratio (P < 0.001) and the visual SI (P = 0.008) in group 2 were significantly lower on the enhanced images than on the unenhanced images. The T2-weighted images obtained during the early phase after enhancement will appear similar to those of the unenhanced T2-weighted images, whereas later images will show a reduced signal of the liver parenchyma.

Thermoablative Treatments for Malignant Liver Lesions: 10-Year Experience of MRI Appearances of Treatment Response

The objective of our study was to describe our 10-year experience using MRI to evaluate response to local thermoablative interventions in the treatment of malignant liver lesions. This retrospective study was conducted from 1998 to 2008. MRI studies were performed at 1.5 and 3 T and were acquired < 4, 4-9, and > 9 months after radiofrequency ablation (RFA), cryoablation, and microwave ablation. MR features were evaluated on the basis of signal intensity on unenhanced T1-weighted images and the presence of ill-defined perilesional enhancement, well-defined lesional enhancement, or washout on contrast-enhanced images. Imaging features were evaluated with all interventional modalities together and separately. The study population was composed of 135 men and 36 women (203 ablated lesions) with a mean age of 65 years (range, 39-78 years). When the data for all treatment methods were combined, well-defined lesional enhancement and washout were significant findings among the resolved and unresolved outcome groups regardless of follow-up time category. After RFA, ablated areas had a tendency to show high signal intensity on T1 images, whereas low signal was seen after cryoablation and a hyperintense rim was seen after microwave ablation. Washout was only depicted 9 months after cryoablation but was seen in 12% of lesions < 4 months after RFA. No difference was appreciated on ill-defined perilesional enhancement with all methods combined or separately. MRI findings after ablation are dependent on the treatment modality and the length of time between the procedure and follow-up examination.

Atherosclerotic Plaque Progression in Carotid Arteries: Monitoring with High-Spatial-Resolution MR Imaging—Multicenter Trial

To estimate the annualized rate of progression of vessel-wall volume in the carotid arteries in 160 patients by using magnetic resonance (MR) imaging and to establish the fraction of studies that have acceptable image quality. The study procedures and consent forms were reviewed and approved by each site's institutional review board. All U.S. study sites conducted all phases of this study in compliance with HIPAA requirements. Written consent was obtained from each participant. One hundred sixty patients with greater than 50% narrowing of the diameter of the carotid artery were recruited at six centers for prospective imaging of the carotid arteries at baseline and 1 year later by using high-spatial-resolution, 1.5-T MR imaging. Studies with unacceptable image quality were excluded. Quantitative changes in atheroma volume were measured on unenhanced T1-weighted images. A multiple linear regression analysis was used to correlate progression with several clinical factors, including statin therapy. All 160 patients completed both baseline and follow-up studies. Of these studies, 67.5% were deemed to have image quality that was acceptable for quantitative analysis. The causes of rejection were motion (46%), deep location of the carotid artery (22%), low bifurcation of the carotid artery (13%), and "other" (19%). The mean annual change in vessel-wall volume was 2.31% +/- 10.88 (standard deviation) (P = .014). At 1-year follow-up, vessel-wall volumes in patients not receiving statin therapy had increased faster compared with those in patients receiving statin therapy: 7.87% +/- 13.58% vs 1.14% +/- 9.9%, respectively (P = .029). Evaluation of results of a multicenter study indicates that quantitative evaluation of the progression of volume of extracranial carotid vessel walls is feasible with 1.5-T MR imaging despite limitations due to patient motion or habitus. In patients who had preexisting carotid disease, the rate of increase in vessel-wall volume was slower in patients receiving statin therapy.

Preoperative T Staging of Urinary Bladder Cancer: Does Diffusion-Weighted MRI Have Supplementary Value?

The objective of our study was to evaluate whether diffusion-weighted MRI has supplementary value in the preoperative T staging of urinary bladder cancer. Nineteen consecutive patients (18 men and one woman; age range, 55-83 years; mean, 71 years) known to have or suspected of having urinary bladder cancer underwent MRI at our institution. Urinary bladder cancer was pathologically proven in 18 patients. The pathologic stages were T1 in 14 patients, T2 in two, T3 in one, and T4 in one. Three separate MR image sets were retrospectively reviewed by two independent radiologists: unenhanced T1-weighted images (TR/TE, 607/10) and T2-weighted images (TR(eff)/TE(eff), 4,415/100); unenhanced T1-weighted, T2-weighted, and gadolinium-enhanced images (TR/TE, 10/4.2); and unenhanced T1-weighted, T2-weighted, and diffusion-weighted images (TR(eff)/TE(eff), 2,191/69; b factor, 1,000 s/mm(2)). The radiologists, who were blinded to the pathology findings, assigned T stages and confidence levels for tumors of stage T2 or greater. We used pathologic stages documented in the official pathologic reports as the standard of reference. Observer performance was tested using Spearman's rank correlation, the McNemar test, and receiver operating characteristic (ROC) curve analysis. The correlation between the radiologic and pathologic stages was greater with the diffusion sequence (rho = 0.66) than with the unenhanced (0.62) or gadolinium-enhanced (0.62) sequence (p = 0.34). The sensitivity, specificity, accuracy, and area under the ROC curve for tumors of stage T2 or greater were 80%, 79%, 79%, and 0.71 for the unenhanced sequence; 80%, 79%, 79%, and 0.77 for the gadolinium sequence; and 40%, 93%, 79%, and 0.56 for the diffusion-weighted sequence, respectively (p > 0.05). Our results suggest that diffusion-weighted MRI might have high specificity for the detection of invasive urinary bladder tumors. Patients with suspected urinary bladder carcinomas may well be evaluated by MRI including diffusion-weighted imaging for better preoperative T staging.