Functional and quantitative magnetic resonance myelography of symptomatic stenoses of the lumbar spine.

INTRODUCTION: The objective of this study was to demonstrate that functional, quantitative magnetic resonance myelography (MRM) allows standardized diagnosis of symptomatic lumbar spinal stenoses which show at least equal detectability compared to functional myelography and postmyelographic CT (pmCT) based on intra- and postoperative findings. METHODS: We investigated 43 volunteers and 47 patients with symptomatic lumbar spinal stenoses using MRM in normal position as well as in flexion and extension in a standard whole-body MR scanner. Twenty volunteers were additionally examined under axial loading. All patients were investigated by functional myelography and pmCT and 10 patients had a functional lumbar MRM postoperatively. Range of motion and cerebrospinal fluid (CSF) volumes in normal position, flexion, extension, and under axial loading (volunteers) were assessed for each segment. Detectability was determined by using intraoperative findings, and postoperative freedom of symptoms was correlated with CSF volume changes in MRM. RESULTS: The ranges of motion in a standard whole-body MR scanner provide adequate scope for investigations into function (flexion and extension) in both volunteers and patients. Axial loading was associated with a mechanism of extension, albeit to a far smaller extent. Detectability of lumbar stenoses was 100% for MRM, 58% for conventional myelography, and 68% for pmCT. Postoperative changes in CSF volume of levels with stenoses in MRM strongly correlated with freedom of symptoms (R = 0.772). CONCLUSION: This MRM method allows for exact diagnosis and reproducible quantification of stenoses, motion-related changes, and spondylolistheses of the lumbar spine. It may be useful for early detection of alterations in order to avoid neuronal compression.

Improved magnetic resonance myelography of the cervical spine using image fusion and volumetry.

BACKGROUND AND AIMS: Discrepancies between symptoms and imaging findings may be significant in spinal diseases. The relative advantages and disadvantages of postmyelographic CT (pmCT) and magnetic resonance myelography (MRM) in measuring cervical cerebrospinal fluid dimensions and volumes are poorly understood. This study investigated the usefulness of an improved MRM approach and compared its findings of dural areas and volumes of normal and pathologic cervical spine levels with those obtained by pmCT. MATERIALS AND METHOD: Sixty patients with suspected cervical spinal stenosis underwent myelography, pmCT, and an improved MRM approach using a dedicated heavily T2-weighted magnetic resonance (MR) sequence in combination with image fusion. Cross-sectional areas and volumes of the dural sac from C2-3 to C7-T1 were compared for significance of differences between mean values. Pearson correlations between pmCT and MRM values were analyzed. Then 99% confidence intervals for normal levels and levels with obvious stenosis were calculated. RESULTS: For normal cervical levels we found no significant differences for both dural areas and volumes between pmCT and MRM. For cervical spine levels C3-4 to C6-7 with pathologic alterations, we found significant larger areas and volumes on MRM when compared with pmCT but not for the levels C2-3 and C7-T1. Both dural area and volume of normal and pathologic levels showed strong correlation between pmCT and MRM. We found no overlap between 99% confidence intervals for normal levels and stenotic levels. CONCLUSIONS: The optimized MRM approach (i.e., a dedicated MRM sequence in combination with image fusion) and pmCT demonstrated excellent quantitative volumetric agreement. Image fusion with conventional T2 may be used to aid in diagnosis.

Improved magnetic resonance myelography of the lumbar spine using image fusion and volumetry.

OBJECT: The goal of this study was to investigate the usefulness and diagnostic potential of an improved MR myelography approach using a dedicated, heavily T2-weighted, 3D MRI sequence in combination with image fusion. A further aim was to compare dural areas and volumes of normal and pathological altered lumbar spine levels, and accuracy in the assessment of the stenoses, with those obtained by postmyelographic CT. METHODS: Fifty patients underwent myelography, postmyelographic CT, and the improved MR myelography approach using a dedicated, heavily T2-weighted, 3D MRI sequence and image fusion. Dural cross-sectional areas and volumes for normal lumbar levels and levels with stenosis were calculated for postmyelographic CT and MR myelography data. The significant differences and Pearson correlations between dural cross-sectional areas and volumes from L1-2 to L5-S1 of postmyelographic CT and MR myelography were analyzed. The 99% CIs for normal and stenotic levels in patients with claudication distances less than 100 meters were calculated. RESULTS: For both dural areas and volumes in normal lumbar levels, the authors found no significant differences and strong correlations between postmyelographic CT and MR myelography. For the lower lumbar levels (L4-5 and L5-S1) they found significantly larger dural areas on MR myelography compared with postmyelographic CT, but not for the upper levels (L2-3 and L3-4). Dural volume analysis revealed significantly larger volumes for MR myelography at all 4 lumbar levels with stenoses in the cohort (L2-3 to L5-S1). Complete separation with no overlap was found between the 99% CIs for normal levels and stenotic levels. CONCLUSIONS: Differences in dural areas and volumes in this study may have been caused by the fact that in the case of a severely compressed thecal sac, the viscosity of the intrathecally applied contrast agent is too high in the framework of myelography. The gravitationally dependent component is thus too low to achieve sufficient fluid contrast. An optimized MR myelography approach-a dedicated 3D MR myelography sequence with high spatial resolution in combination with image fusion-is required to achieve a more reliable diagnosis of lumbar spine stenoses, especially with severe compression, compared with postmyelographic CT. This MR myelography approach may be helpful in preventing overestimation of lumbar spine stenoses. The upper limits of 99% CIs for stenotic levels can be interpreted as an indication for surgical treatment. However, further studies that include postoperative outcomes are required.

Magnetic resonance fiber density mapping of age-related white matter changes.

OBJECTIVES: To introduce fiber density mapping (FDM) for investigation of age-related white matter (WM) changes and to compare its capabilities with conventional diffusion tensor imaging (DTI) post-processing. METHODS: DTI data with 1.9 mm(3) isotropic voxels were acquired from 44 healthy volunteers (18-88 years) at 3T. FDM is a 3-step approach which includes diagonalization of the diffusion tensor, fiber reconstruction for the whole brain, and calculation of fiber density (FD) values. Maps of fractional anisotropy (FA) and mean diffusivity (MD) were additionally calculated. Voxel-based analyses were performed to determine volume clusters of significant correlation with age. Bivariate linear regression models and Hotelling-Williams tests were used to detect significant differences between correlations. RESULTS: FDM detected a larger WM volume affected by age-related changes concomitant with fewer significant clusters compared to FA and MD. This indicates that WM alterations due to normal aging occur rather globally than locally. FD values showed a significant stronger correlation with age in frontal lobes (prefrontal and precentral gyrus), limbic lobes (cingulate and parahippocampal gyrus), the corpus callosum (genu) and temporal lobes. CONCLUSIONS: FDM shows higher sensitivity for detection of age-related WM changes because it includes all surrounding fiber structures into the evaluation of each DTI data voxel.

MR imaging of the knee: Improvement of signal and contrast efficiency of T1-weighted turbo spin echo sequences by applying a driven equilibrium (DRIVE) pulse.

The purpose of this study was to assess the effect of a driven equilibrium (DRIVE) pulse incorporated in a standard T1-weighted turbo spin echo (TSE) sequence as used in our routine MRI protocol for examination of pathologies of the knee. Sixteen consecutive patients with knee disorders were examined using the routine MRI protocol, including T1-weighted TSE-sequences with and without a DRIVE pulse. Signal-to-noise ratios (SNRs) and contrast-to-noise ratio (CNR) of anatomical structures and pathologies were calculated and compared for both sequences. The differences in diagnostic value of the T1-weighted images with and without DRIVE pulse were assessed. SNR was significantly higher on images acquired with DRIVE pulse for fluid, effusion, cartilage and bone. Differences in the SNR of meniscus and muscle between the two sequences were not statistically significant. CNR was significantly increased between muscle and effusion, fluid and cartilage, fluid and meniscus, cartilage and meniscus, bone and cartilage on images acquired using the DRIVE pulse. Diagnostic value of the T1-weighted images was found to be improved for delineation of anatomic structures and for diagnosing a variety of pathologies when a DRIVE pulse is incorporated in the sequence. Incorporation of a DRIVE pulse into a standard T1-weighted TSE-sequence leads to significant increase of SNR and CNR of both, anatomical structures and pathologies, and consequently to an increase in diagnostic value within the same acquisition time.

Intracranial aneurysms and dolichoectasia in autosomal dominant polycystic kidney disease.

BACKGROUND: Intracranial saccular aneurysms (ICA) are a known extrarenal manifestation of autosomal dominant polycystic kidney disease (ADPKD). In order to facilitate the definition of subgroups who are at risk for ICA and to determine the prevalence of ICA in these subgroups we studied ADPKD patients with a positive family history for a cerebral event, including cerebral stroke (group I) and intracranial bleeding or known ICA (group II). METHODS: Within an enrolment period of 21 months, 43 ADPKD patients from our outpatient clinic and hospital were examined with cerebral magnetic resonance angiography (MRA). RESULTS: ICA were detected in six patients (14%). Three out of 32 patients (9.4%) in group I and three out of 11 patients (27.3%) in group II had an ICA. A dolichoectasia of intracerebral vessels was found in two out of 43 patients (4.7%). CONCLUSIONS: Using MRA a high prevalence of ICA was shown only in patients with a family history of cerebral bleeding or ICA. A family history for cerebral stroke does not imply an elevated risk for ICA. However, dolichoectasia, rare in the normal population, was detected in two patients. We recommend screening for ICA in patients with a positive family history for cerebral bleeding or ICA. Because of potential complications, examiners should direct their attention to dolichoectasia in ADPKD patients.