Isolated bilateral horizontal gaze palsy as first manifestation of multiple sclerosis.

Predilection sites for infratentorial multiple sclerosis lesions are well known and frequently involve the fasciculus longitudinalis medialis leading to classical internuclear ophthalmoplegia. We report a very rare oculomotor disorder due to a demyelinating central nervous system (CNS) lesion in the medial part of the lower pontine tegmentum. A 36-year-old man presented with sudden onset of blurred vision. Clinically there was limited eye adduction and abduction to either side, which corresponds to bilateral horizontal gaze palsy. Brain magnetic resonance imaging (MRI) showed a demyelinating CNS lesion affecting the fasciculus longitudinalis medialis, abducens nuclei or abducens fibres in the medial part of the lower pontine tegmentum. Furthermore there were six further demyelinating white matter lesions fulfilling all Barkhof criteria for multiple sclerosis. Demyelinating CNS lesions causing isolated bilateral horizontal gaze palsy are exceptional and usually associated with further focal neurological deficits, which was not the case in the presenting patient. This is a unique video report of isolated bilateral horizontal gaze palsy as the initial manifestation of demyelinating CNS disease, which lead to definite diagnosis of relapsing remitting multiple sclerosis.

Discrimination and anatomical mapping of PET-positive lesions: comparison of CT attenuation-corrected PET images with coregistered MR and CT images in the abdomen.

PURPOSE: PET/MR has the potential to become a powerful tool in clinical oncological imaging. The purpose of this prospective study was to evaluate the performance of a single T1-weighted (T1w) fat-suppressed unenhanced MR pulse sequence of the abdomen in comparison with unenhanced low-dose CT images to characterize PET-positive lesions. METHODS: A total of 100 oncological patients underwent sequential whole-body (18)F-FDG PET with CT-based attenuation correction (AC), 40 mAs low-dose CT and two-point Dixon-based T1w 3D MRI of the abdomen in a trimodality PET/CT-MR system. PET-positive lesions were assessed by CT and MRI with regard to their anatomical location, conspicuity and additional relevant information for characterization. RESULTS: From among 66 patients with at least one PET-positive lesion, 147 lesions were evaluated. No significant difference between MRI and CT was found regarding anatomical lesion localization. The MR pulse sequence used performed significantly better than CT regarding conspicuity of liver lesions (p < 0.001, Wilcoxon signed ranks test), whereas no difference was noted for extrahepatic lesions. For overall lesion characterization, MRI was considered superior to CT in 40 % of lesions, equal to CT in 49 %, and inferior to CT in 11 %. CONCLUSION: Fast Dixon-based T1w MRI outperformed low-dose CT in terms of conspicuity and characterization of PET-positive liver lesions and performed similarly in extrahepatic tumour manifestations. Hence, under the assumption that the technical issue of MR AC for whole-body PET examinations is solved, in abdominal PET/MR imaging the replacement of low-dose CT by a single Dixon-based MR pulse sequence for anatomical lesion correlation appears to be valid and robust.

PET/MR imaging of bone lesions--implications for PET quantification from imperfect attenuation correction.

PURPOSE: Accurate attenuation correction (AC) is essential for quantitative analysis of PET tracer distribution. In MR, the lack of cortical bone signal makes bone segmentation difficult and may require implementation of special sequences. The purpose of this study was to evaluate the need for accurate bone segmentation in MR-based AC for whole-body PET/MR imaging. METHODS: In 22 patients undergoing sequential PET/CT and 3-T MR imaging, modified CT AC maps were produced by replacing pixels with values of >100 HU, representing mostly bone structures, by pixels with a constant value of 36 HU corresponding to soft tissue, thereby simulating current MR-derived AC maps. A total of 141 FDG-positive osseous lesions and 50 soft-tissue lesions adjacent to bones were evaluated. The mean standardized uptake value (SUVmean) was measured in each lesion in PET images reconstructed once using the standard AC maps and once using the modified AC maps. Subsequently, the errors in lesion tracer uptake for the modified PET images were calculated using the standard PET image as a reference. RESULTS: Substitution of bone by soft tissue values in AC maps resulted in an underestimation of tracer uptake in osseous and soft tissue lesions adjacent to bones of 11.2 ± 5.4% (range 1.5-30.8%) and 3.2 ± 1.7% (range 0.2-4%), respectively. Analysis of the spine and pelvic osseous lesions revealed a substantial dependence of the error on lesion composition. For predominantly sclerotic spine lesions, the mean underestimation was 15.9 ± 3.4% (range 9.9-23.5%) and for osteolytic spine lesions, 7.2 ± 1.7% (range 4.9-9.3%), respectively. CONCLUSION: CT data simulating treating bone as soft tissue as is currently done in MR maps for PET AC leads to a substantial underestimation of tracer uptake in bone lesions and depends on lesion composition, the largest error being seen in sclerotic lesions. Therefore, depiction of cortical bone and other calcified areas in MR AC maps is necessary for accurate quantification of tracer uptake values in PET/MR imaging.

FDG uptake in vaginal tampons is caused by urinary contamination and related to tampon position.

PURPOSE: The aim of the study was to determine the aetiology of FDG uptake in vaginal tampons (VT), a known artefact in premenopausal women evaluated by PET/CT. METHODS: This Institutional Review Board approved study consisted of retrospective and prospective parts. The retrospective analysis included 685 women examined between January 2008 and December 2009 regarding VT presence. PET/CT images were analysed to determine the localization and the standardized uptake value (SUV) of VTs. We prospectively recruited 24 women (20-48 years old) referred for staging or follow-up in an oncology setting between February and April 2010, who were provided a commercial VT to be used during the entire examination after obtaining written informed consent. After image acquisition, VTs were individually analysed for creatinine concentration and blood traces. Statistical significance was tested with the Mann-Whitney U test. RESULTS: In the retrospective part, 38 of 685 women were found to have a VT of which 17 (45%) were FDG positive. A statistically significant correlation was found between FDG activity and VT position below the pubococcygeal line (PCL) (13 ± 11.2 mm). In the prospective study, 7 of 24 (29%) women had increased FDG activity in their VTs (SUV 18.8 ± 11 g/ml) but were not menstruating. FDG-positive VTs were significantly lower in position (14.6 ± 11.4 mm,below the PCL) than FDG-negative VTs (p = 0.039). The creatinine concentration was significantly increased in all seven positive VTs (931 ± 615 µmol/l). CONCLUSION: FDG uptake in VTs is caused by urine contamination, which is likely related to localization below the PCL resulting in contact with urine during voiding.

Peripheral neuropathies of the median, radial, and ulnar nerves: MR imaging features.

The median, radial, and ulnar nerves of the upper limbs may be affected by various peripheral neuropathies, each of which may be categorized according to its cause, as either an entrapment or a nonentrapment neuropathy. Entrapment neuropathies, also referred to as nerve compression syndromes, include the supracondylar process syndrome, pronator syndrome, anterior interosseous nerve syndrome, carpal tunnel syndrome, posterior interosseous nerve syndrome, cubital tunnel syndrome, and Guyon canal syndrome. Nonentrapment neuropathies include traumatic nerve injuries, infectious and inflammatory conditions, polyneuropathies, and mass lesions at anatomic locations where entrapment syndromes typically do not occur. Although clinical examination and electrophysiologic testing are the cornerstone of the diagnostic work-up, in certain cases magnetic resonance (MR) imaging may provide key information about the exact anatomic location of a lesion or may help narrow the differential diagnosis. In patients with a diagnosis of peripheral neuropathy, MR imaging may help establish the cause of the condition and provide information crucial for conservative management or surgical planning. In addition, knowledge of the normal anatomy and of the possible causes, typical clinical findings, and MR imaging features of peripheral neuropathies that affect the median, radial, and ulnar nerves allows greater confidence in the diagnosis.

MR imaging of the knee: position related changes of the menisci in asymptomatic volunteers.

RATIONALE AND OBJECTIVES: To evaluate position related changes of the menisci in asymptomatic volunteers based on MR imaging of the knee in different positions. METHODS: Twenty-two knees from 22 asymptomatic volunteers with no history of knee injury and no evidence of meniscal tears were examined with a 0.5-T open-configuration MR system. Sagittal and coronal images were obtained with the knee supine in neutral, supine in 90-degree flexion with external and internal rotation, as well as in upright weight-bearing positions. The position of the menisci from the outer inferior edge of the meniscus to the outermost edge of the articular cartilage of the tibial plateau was measured, and meniscal movement was calculated. The Wilcoxon signed-rank test was used for statistical analysis. RESULTS: Meniscal movement in the sagittal plane was greatest in the anterior horn of the medial meniscus upon position change from supine neutral to supine in 90-degree flexion with external rotation (mean, 10.5 millimeters). The least meniscal movement was observed in the anterior horn of the lateral meniscus when changing from the supine neutral to the upright knee position (mean, 0.6 millimeters). Meniscal protrusion (ie, protrusion of any part of the meniscus beyond the tibial plateau) was noted most frequently for the anterior horn of the medial meniscus (14/22 instances; 63.6%) in the sagittal plane with the knee in neutral position (mean, 2.6 millimeters, range, 1.8-2.8 millimeters). In the coronal plane, medial meniscal protrusion was most frequently present in the upright weight-bearing position (11/22 instances (50%; mean, 2 millimeters; range, 1.2-2.6 millimeters). CONCLUSIONS: : Meniscal movement is most prominent in the anterior horn of the medial meniscus with the knee in the supine position in 90-degree flexion with external rotation. Meniscal protrusion is more frequently present in the medial meniscus and averaged less than 3 millimeters in normal volunteers in either the sagittal or coronal MR imaging plane.

Assessment of dynamic contrast enhancement of the small bowel in active Crohn's disease using 3D MR enterography.

PURPOSE: To retrospectively compare the dynamic contrast enhancement of the small bowel segments with and without active Crohn's disease at 3D MR enterography (MRE). MATERIALS AND METHODS: Thirteen patients (five men, eight women; mean age 41.2 years; range 29-56) were imaged on a 1.5-T MR scanner (Sonata, Siemens Medical) with standard MR sequences after having ingested 1000 ml of a 3% mannitol solution. Subsequently, high resolution 3D gradient-echo (volumetric interpolated breath-hold examination=VIBE) data sets were obtained pre-contrast and 20-40s, 60-80s, and 120-140 s after i.v. Gd-DOTA administration (0.2 mmol/kg). Signal enhancement was measured on single slices both in normal and histologically confirmed (12/13) inflamed small bowel wall segments as well as in the aorta, the psoas muscle, and the background to calculate signal-to-noise (SNR) and contrast-to-noise ratios (CNR). RESULTS: Small bowel wall enhancement was significantly higher (p<0.05) in inflamed compared to normal segments at 20-40s (SNR inflamed: 58.7+/-33.8 vs normal: 36.0+/-19.8; p=0.048; CNR inflamed: 34.8+/-23.4 vs normal: 16.3+/-11.2; p=0.017) and at 60-80s (SNR: 60.3+/-25.1 vs 41.9+/-20.0; p=0.049; CNR: 34.9+/-15.1 vs 19.3+/-13.2; p=0.01) after i.v. contrast administration, respectively. Even at 120-140 s CNR was still increased in inflamed segments (33.7+/-16.0 vs 18.1+/-13.2; p=0.04), while differences in SNR did not attain statistical significance (63.0+/-26.2 vs 45.3+/-23.3; p=0.15). CONCLUSION: In active Crohn's disease, histologically confirmed inflamed small bowel wall segments demonstrate a significantly increased early uptake of gadolinium on 3D VIBE sequences compared to normal small bowel segments.

Comparison of magnetic resonance enterography and video capsule endoscopy in evaluating small bowel disease.

PURPOSE: The goal of this study was to compare magnetic resonance enterography (MRE) and video capsule endoscopy (VCE) in suspected small bowel disease. MATERIALS AND METHODS: Nineteen patients with suspected small bowel disease participated in a prospective clinical comparison of MRE versus VCE. Both methods were evaluated separately and in conjunction with respect to a combined diagnostic endpoint based on clinical, laboratory, surgical, and histopathological findings. The Fisher's exact and j tests were used in comparing MRE and VCE. RESULTS: Small bowel pathologies were found in 15 out of 19 patients: Crohn's disease (n= 5), lymphoma (n= 4), lymphangioma (n= 1), adenocarcinoma (n= 1), postradiation enteropathy (n= 1), NSAID-induced enteropathy (n =1), angiodysplasia (n= 1), and small bowel adhesions (n= 1). VCE and MRE separately and in conjunction showed sensitivities of 92.9, 71.4, and 100% and specificities of 80, 60, and 80% (kappa= 0.73 vs. kappa = 0.29; P= 0.31/kappa = 0.85), respectively. In four patients, VCE depicted mucosal pathologies missed by MRE. MRE revealed 19 extraenteric findings in 11 patients as well as small bowel adhesions not detected on VCE (n= 1). CONCLUSION: VCE can readily depict and characterize subtle mucosal lesions missed at MRE, whereas MRE yields additional mural, perienteric, and extraenteric information. Thus, VCE and MRE appear to be complementary methods which, when used in conjunction, may better characterize suspected small bowel disease.

MRI of the intrinsic muscles of the hand: spectrum of imaging findings and clinical correlation.

OBJECTIVE: The purpose of our study was to describe the spectrum of intrinsic hand muscle abnormalities on MRI in patients with clinically evident abnormalities of the intrinsic hand muscles and to correlate clinical and radiologic findings. MATERIALS AND METHODS: MRI of 21 hands was performed in 19 patients with clinically evident or suspected intrinsic hand muscle abnormalities. All MRI was performed on a 1.5-T scanner using transaxial T1-weighted, T2-weighted, or STIR as well as contrast-enhanced T1-weighted sequences. Two observers reviewed all MR images retrospectively in a blinded fashion with regard to the exact anatomic location of the muscle abnormality, signal abnormalities, muscle atrophy, and the cause. Kappa statistics were used to calculate interobserver variability. MRI findings were compared with clinical findings using Spearman's rank test. A panel of experts assessed the impact of MRI on the diagnostic workup. RESULTS: On the basis of MRI findings, abnormalities (either MR signal abnormality or atrophy) of both the lumbrical and interosseus muscles were noted in 10 (48%) of 21 hands, of the thenar muscles in eight (38%) of 21 hands, and of the hypothenar muscles in 12 (57%) of 21 hands. The correlation between clinical and MRI findings was moderate to strong for the interosseus, thenar, and hypothenar muscles (0.43-0.84). MRI was judged to be useful for establishing the final diagnosis in 17 (81%) of 21 hands. CONCLUSION: MRI of the hands is useful and correlates well with clinical findings in patients with intrinsic hand muscle abnormalities.

Thin-section CT of the lung: does electrocardiographic triggering influence diagnosis?

PURPOSE: To determine the impact of prospective electrocardiographic (ECG) triggering on image quality and diagnostic outcome of thin-section computed tomography (CT) of the lung. MATERIALS AND METHODS: Forty-five consecutive patients referred for thin-section CT of the lung were examined with prospectively ECG-triggered and nontriggered thin-section CT of the lung with a multi-detector row helical CT scanner. Subjective image quality criteria (image noise, motion artifacts, and diagnostic accessibility) were rated by three radiologists in consensus for the upper lobe, middle lobe and/or lingula, and lower lobe. Pathologic changes were assessed for the various lobes, and a diagnosis was assigned. The diagnoses were compared by two radiologists in consensus to determine the effects of CT technique on diagnostic outcome. Quantitative measurements were performed, including determination of image noise and signal-to-noise ratios in different anatomic regions. The Wilcoxon signed rank test and paired sign test (both with Bonferroni correction) were used for statistical analysis. RESULTS: Subjective assessment showed significant differences in motion artifact reduction in the middle lobe, lingula, and left lower lobe. The diagnostic assessibility of triggered CT was rated significantly higher only for the left lower lobe compared with nontriggered data acquisition. No differences in diagnostic outcome were determined between triggered and nontriggered techniques. Mean image noise in tracheal air was 68.2 +/- 17 (SD) for triggered CT versus 37.4 +/- 9 for nontriggered CT (P <.05). Mean signal-to-noise ratio in the upper versus lower lobes was 22.5 +/- 8 versus 25.4 +/- 10 for triggered and 35.6 +/- 9 versus 39.2 +/- 10 for nontriggered techniques (P <.05). CONCLUSION: Given the lack of improvement in diagnostic accuracy and the need for additional resources, ECG-triggered thin-section CT of the lung is not recommended for routine clinical practice.