Poster: "ECR 2012 / C-0840 / Meta-analysis: Accuracy of contrast-enhanced magnetic resonance angiography for assessing steno-occlusions in peripheral arterial disease" by: "J. Menke, J. Larsen; Goettingen/DE"

Meta-analysis: Accuracy of Contrast-Enhanced Magnetic Resonance Angiography for Assessing Steno-occlusions in Peripheral Arterial Disease

The goal of this study was to assess the reliability of measurements of the physical characteristics of spiculated masses on mammography The images used in this study were obtained from the Digital Database for Screening Mammography Two experienced radiologists measured the properties of 21 images of spiculated masses The length and width of all spicules and the major axis of the mass were measured In addition, the observers counted the total number of spicules Interobserver and intraobserver variability were evaluated using a hypothesis test for equivalence, the intraclass correlation coefficient (ICC) and Bland-Altman statistics For an equivalence level of 30% of the mean of the senior radiologist's measurement, equivalence was achieved for the measurements of average spicule length (p,001), average spicule width (p5003), the length of the major axis (p,001) and for the count of the number of spicules (p,001) Similarly, with the ICC analysis technique ''excellent'' inter-rater agreement was observed for the measurements of average spicule length (ICC50770), the length of the major axis (ICC50801) and for the count of the number of spicules (ICC50780) ''Fair to good'' agreement was observed for the average spicule width (ICC50561) Equivalence was also demonstrated for intraobserver measurements Physical properties of spiculated masses can be measured reliably on mammography The interobserver and intraobserver variability for this task is comparable with that reported for other measurements made on medical images

The reliability of measuring physical characteristics of spiculated masses on mammography

Objectives:The aim of the current study was to test the reproducibility of different quantitative magnetic resonance imaging (MRI) methods to assess the morphologic and functional peripheral vascular status and vascular adaptations over time in patients with peripheral arterial disease (PAD)Materia

Magnetic resonance imaging in peripheral arterial disease: reproducibility of the assessment of morphological and functional vascular status

Purpose: We sought to evaluate and compare the image quality and vessel delineation of the carotid arteries with high spatial-resolution contrast-enhanced MRA (CE-MRA) at 3.0 T using integrated parallel acquisition (iPAT) with acceleration factors of 2 and 4. Materials and Methods: Using an 8-channel neurovascular array coil, we performed prospective high-spatial resolution CE-MRA at 3.0 T of the head and neck on 24 patients (11 men, 13 women, ages 37-89) with suspected arterio-occlusive disease who were assigned randomly to 2 groups. Twelve patients (group A) were examined with a 3D-GRE sequence using iPAT with acceleration factor of 2. For the next 12 patients (group B) a near-identical sequence with an acceleration factor of 4 was applied. Higher iPAT factors were used to increase the spatial-resolution while keeping scan time unchanged. Two volunteers were scanned by both protocols. Phantom measurements were performed to assess the signal-to-noise ratio (SNR). The presence of artifact, noise, image quality of the arterial segments, and the presence and degree of arterial stenosis were evaluated independently by 2 radiologists. Statistical analysis of data was performed by using Wilcoxon rank sum test and 2-sample Student t test (P < 0.05 was indicative a statistically significant difference). The interobserver variability was tested by kappa coefficient. Results: SNR values were significantly lower when iPAT with acceleration factor of 4 was used (P < 0.001). There was no significant difference between 2 groups in regards to image noise (P = 0.67) and artifact (P = 0.8). Both readers visualized the majority of carotid circulation with good image quality in both groups. For smaller intracranial arteries, such as the second-division of anterior and middle cerebral artery, anterior communicating artery, and superior cerebellar artery, the image quality and vessel delineation was significantly better at an iPAT factor of 4 (P < 0.01). The overall interobserver agreement for both the vessel depiction, and detection of arterial stenoses was higher in group B compared with group A. Conclusion: Use of parallel acquisition techniques with a high acceleration factor (iPAT-4) results in superior depiction of small intracranial arterial segments. Imaging at higher magnetic field strength, in addition to the use of an optimized 8-channel array coil, provides sufficient SNR to support faster parallel acquisition protocols, leading to improved spatial-resolution. More extensive clinical studies are warranted to establish the range of applications and confirm the accuracy of the technique.

High spatial-resolution CE-MRA of the carotid circulation with parallel imaging: comparison of image quality between 2 different acceleration factors at 3.0 Tesla.

Introduction Recent developments in hard- and software help to significantly increase image quality of magnetic resonance angiography (MRA). Parallel acquisition techniques (PAT) help to increase spatial resolution and to decrease acquisition time but also suffer from a decrease in signal-to-noise ratio (SNR). The movement to higher field strength and the use of dedicated angiography coils can further increase spatial resolution while decreasing acquisition times at the same SNR as it is known from contemporary exams. The goal of our study was to compare the image quality of MRA datasets acquired with a standard matrix coil in comparison to MRA datasets acquired with a dedicated peripheral angio matrix coil and higher factors of parallel imaging. Materials and methods Before the first volunteer examination, unaccelerated phantom measurements were performed with the different coils. After institutional review board approval, 15 healthy volunteers underwent MRA of the lower extremity on a 32 channel 3.0 Tesla MR System. In 5 of them MRA of the calves was performed with a PAT acceleration factor of 2 and a standard body-matrix surface coil placed at the legs. Ten volunteers underwent MRA of the calves with a dedicated 36-element angiography matrix coil: 5 with a PAT acceleration of 3 and 5 with a PAT acceleration factor of 4, respectively. The acquired volume and acquisition time was approximately the same in all examinations, only the spatial resolution was increased with the acceleration factor. The acquisition time per voxel was calculated. Image quality was rated independently by 2 readers in terms of vessel conspicuity, venous overlay, and occurrence of artifacts. The inter-reader agreement was calculated by the kappa-statistics. SNR and contrast-to-noise ratios from the different examinations were evaluated. Results All 15 volunteers completed the examination, no adverse events occurred. None of the examinations showed venous overlay; 70% of the examinations showed an excellent vessel conspicuity, whereas in 50% of the examinations artifacts occurred. All of these artifacts were judged as none disturbing. Inter-reader agreement was good with kappa values ranging between 0.65 and 0.74. SNR and contrast-to-noise ratios did not show significant differences. Conclusion Implementation of a dedicated coil for peripheral MRA at 3.0 Tesla helps to increase spatial resolution and to decrease acquisition time while the image quality could be kept equal. Venous overlay can be effectively avoided despite the use of high-resolution scans.

High-resolution magnetic resonance angiography of the lower extremities with a dedicated 36-element matrix coil at 3 Tesla.

OBJECTIVES We sought to compare reproducibility and accuracy of semiautomated stenosis detection and quantification in 3D contrast-enhanced magnetic resonance angiography (CE-MRA) images with conventional evaluation of 3D CE-MRA in patients with peripheral arterial disease (PAD) by using intra-arterial digital subtraction angiography (IA-DSA) as standard of reference. METHODS Twenty-five patients with PAD underwent CE-MRA and IA-DSA. Three blinded observers independently evaluated CE-MRA datasets for stenoses in the aortoiliac region using semiautomated computer analysis. Semiautomated measurements were compared with conventional measurements of stenosis on CE-MRA datasets, as measured by 3 other independent observers blinded to all other measurements. Interobserver agreement was quantified using kappa (kappa) and intraclass correlation coefficients (ICCs). Sensitivity and specificity were determined for both semiautomated and conventional measurements. RESULTS Semiautomated measurements were successful in 124 of the 125 arterial segments. The sensitivity of semiautomated measurements was 89% for all observers; specificity varied between 87% and 89%. For conventional measurements of CE-MRA, sensitivity varied between 79% and 86%; specificity was between 86% and 96%. There was good interobserver agreement between all readers for semiautomated measurements (combined kappa for all 3 observers together = 0.78; ICC = 0.82), as well as for conventional measurements (combined kappa = 0.70; and ICC = 0.83). Differences between ICCs, combined kappa values, and accuracy of both measurements were not significant (all P > 0.05). CONCLUSION Semiautomated analysis of aortoiliac 3D CE-MRA has the same high accuracy for detection and quantification of stenoses as conventional readings of CE-MRA.

Accuracy of Semiautomated Analysis of 3D Contrast-Enhanced Magnetic Resonance Angiography for Detection and Quantification of Aortoiliac Stenoses

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Accuracy of Semiautomated Analysis of 3D Contrast-Enhanced Magnetic Resonance Angiography for Detection and Quantification of Aortoiliac Stenoses