Bildgebende Diagnostik von Nervenkompressionssyndromen

Zusammenfassung: Kompressionsbedingte Schädigungen peripherer Nerven können die Ursache hartnäckiger Schmerzen im Bereich des Sprunggelenks und Fußes sein. Eine frühzeitige Diagnose ist entscheidend, um den Patienten der richtigen Therapie zuzuführen und potenzielle Schädigungen zu vermeiden oder zu verringern. Obschon die klinische Untersuchung und die elektrophysiologische Abklärungen die wichtigsten Elemente der Diagnostik peripherer Nervenkompressionssyndrome sind, kann die Bildgebung entscheidend sein, wenn es darum geht, die Höhe des Nervenschadens festzulegen oder die Differenzialdiagnose einzugrenzen. In gewissen Fällen kann durch Bildgebung sogar die Ursache der Nervenkompression gefunden werden. In anderen Fällen ist die Bildgebung wichtig bei der Therapieplanung, insbesondere dann, wenn die Läsion chirurgisch angegangen wird. Magnetresonanztomographie (MRT) und Sonographie ermöglichen eine direkte Visualisierung der Nerven und ihrer umgebenden Strukturen. Knöcherne Läsionen, die zu einem Nervenkompressionssyndrom führen können, werden am besten mittels konventionellem Röntgenbild und/oder Computertomographie (CT) dargestellt. Die Kenntnis der anatomischen Gegebenheiten, Ursachen und klinischen Befunde sowie der Bildbefunde ist für die richtige Diagnose entscheiden

CT and MR imaging of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common tumor in the world and the incidence is expected to increase in the future due to hepatitis viral infections and increasing cirrhosis incidence. The diagnosis of HCC is no longer based on biopsy especially in cases when curative treatment is possible. The imaging criteria are usually based on the vascular findings of HCC (e.g. early arterial uptake followed by washout in the portovenous and equilibrium phase). However, there are several limitations of the assessment of HCC by using only the vascular criteria. The use of tissue-specific contrast agents, including superparamagnetic iron oxides and hepatobiliary contrast agents, improves lesion detection and characterization. Therefore, an accurate diagnosis of HCC implies, at this moment, a combination of vascular and cellular information. This review focuses on the most important findings provided by the unenhanced and dynamic-enhanced CT and MR images regarding HCC evaluation. We also discuss the various imaging characteristics of HCC at MR imaging after the administration of tissue specific contrast agents

Diffusion tensor imaging and fiber tractography of the median nerve at 1.5T: optimization of b value

Objective: The objective of this study was to systematically assess the optimal b value for diffusion tensor imaging and fiber tractography of the median nerve at 1.5T. Materials and methods: This is a prospective study which was carried out with institutional review board approval and written informed consent from the study subjects. Fifteen healthy volunteers (seven men, eight women; mean age, 31.2years) underwent diffusion tensor imaging of the wrist. A single-shot spin-echo-based echo-planar imaging sequence (TR/TE, 7000/103ms) was performed in each subject at eight different b values ranging from 325 to 1,550s/mm2. Number and length of reconstructed fiber tracts, fiber density index (FDi), fractional anisotropy (FA), and apparent diffusion coefficient (ADC) were calculated for the median nerve. Signal-to-noise ratio (SNR) was also calculated for each acquisition. The overall image quality was assessed by two readers in consensus by ranking representative fiber tract images for each subject using a scale range from 1 to 8 (1 = best to 8 = worst image quality). Results: Longest fibers were observed for b values between 675 and 1,025s/mm2. Maximum FDi was found at b values of 1,025s/mm2. FA was between 0.5 and 0.6 for all b values. ADC gradually decreased from 1.44 × 10−3 to 0.92 × 10−3mm2/s with increasing b values. Maximum SNR ± standard deviation (175.4 ± 72.6) was observed at the lowest b value and decreased with increasing b values. SNR at b values of 1,025s/mm2 was 48.5% of the maximum SNR. Optimal fiber tract image quality was found for b values of 1,025s/mm2. Conclusions: The optimal b value for diffusion tensor imaging and fiber tractography of the median nerve at 1.5T was 1,025s/mm

Double-contrast magnetic resonance imaging of hepatocellular carcinoma after transarterial chemoembolization

Background: The purpose of this study was to assess the accuracy of double-contrast magnetic resonance (MR) imaging for the treatment response evaluation of hepatocellular carcinoma (HCC) in cirrhotic liver after transarterial chemoembolization (TACE). Methods: Twenty-two patients with 30 HCC nodules treated by TACE underwent double-contrast MR imaging 1month after treatment. MR images were obtained before and after the sequential administration of superparamagnetic iron oxide (SPIO) and gadopentetate dimeglumine contrast agent within the same imaging session. Two observers retrospectively assessed all treated nodules for evidence of residual viable tumor after TACE. The diagnostic performance of gadolinium-enhanced, SPIO-enhanced, and double-contrast enhanced images was calculated. Histopathological and angiographical findings served as standard of reference. Receiver operating characteristic curves and areas under the curves (A z) were calculated. Results: Double-contrast technique (A z=0.95) was significantly (p=0.036) more accurate than SPIO-enhanced technique (A z=0.92) and gadolinium-enhanced technique (p=0.005) (A z=0.81) in viable tumor detection after TACE. Double-contrast technique was significantly more sensitive (92%) than SPIO-enhanced technique (80%) and gadolinium-enhanced technique (68%). Kappa values for interobserver agreement ranged from 0.67 to 0.87 and were significantly different from zero (all p<0.001). Conclusions: Compared to gadolinium-enhanced and SPIO-enhanced techniques, double-contrast technique significantly improves the detection of viable tumor in HCC after TAC

Upper extremity peripheral neuropathies: role and impact of MR imaging on patient management

To investigate the role of MR imaging (MRI) in the evaluation of peripheral nerve lesions of the upper extremities and to assess its impact on the patient management. Fifty-one patients with clinical evidence of radial, median, and/or ulnar nerve lesions and unclear or ambiguous clinical findings had MRI of the upper extremity at 1.5T. MR images and clinical data were reviewed by two blinded radiologists and a group of three clinical experts, respectively, with regard to radial, median, and/or ulnar nerve, as well as muscle abnormalities. MRI and clinical findings were correlated using Spearman's (p) rank correlation test. The impact of MRI on patient management was assessed by the group of experts and ranked as "major,” "moderate,” or "no” impact. The correlation of MRI and clinical findings was moderate for the assessment of the median/radial nerve and muscles (p = 0.51/0.51/0.63, respectively) and weak for the ulnar nerve (p = 0.40). The impact of MRI on patient management was assessed as "major” in 24/51 (47%), "moderate” in 19/51 (37%), and "no” in 8/51 (16%) patients. MRI in patients with upper extremity peripheral neuropathies and unclear or ambiguous clinical findings substantially influences the patient managemen

Magnetic resonance imaging and magnetic resonance arthrography of the shoulder: dependence on the level of training of the performing radiologist for diagnostic accuracy

Purpose: Discrepancies were identified between magnetic resonance (MR) imaging and clinical findings in patients who had MR imaging examinations evaluated by community-based general radiologists. The purpose of this study was to evaluate the diagnostic performance of MR imaging examinations of the shoulder with regard to the training level of the performing radiologist. Methods: A review of patient charts identified 238 patients (male/female, 175/63; mean age, 40.4years) in whom 250 arthroscopies were performed and who underwent MR imaging or direct MR arthrography in either a community-based or hospital-based institution prior to surgery. All MR imaging and surgical reports were reviewed and the diagnostic performance for the detection of labral, rotator cuff, biceps, and Hill-Sachs lesions was determined. Kappa and Student's t test analyses were performed in a subset of cases in which initial community-based MR images were re-evaluated by hospital-based musculoskeletal radiologists, to determine the interobserver agreement and any differences in image interpretation. Results: The diagnostic performance of community-based general radiologists was lower than that of hospital-based sub-specialized musculoskeletal radiologists. A sub-analysis of re-evaluated cases showed that musculoskeletal radiologists performed better. κ values were 0.208, 0.396, 0.376, and 0.788 for labral, rotator cuff, biceps, and Hill-Sachs lesions (t test statistics: p = <0.001, 0.004, 0.019, and 0.235). Conclusions: Our results indicate that the diagnostic performance of MR imaging and MR arthrography of the shoulder depends on the training level of the performing radiologist, with sub-specialized musculoskeletal radiologists having a better diagnostic performance than general radiologist

C-arm flat-panel CT arthrography of the wrist and elbow: first experiences in human cadavers

Objective: To determine the optimal intra-articular iodine concentration for C-arm flat-panel computed tomography (FPCT) arthrography using advanced joint phantoms and to evaluate its application in human cadaveric wrists and elbows. Multi-detector (MD) CT served as the standard of reference. Materials and methods: Joint phantoms and 10 human cadaveric wrist and elbow joints were scanned with C-arm FPCT (5-s, 8-s, and 20-s runs) and standard MDCT using different and optimal concentrations of iodinated contrast material. CT numbers of contrast material, tissue, and noise were measured and contrast-to-noise ratios (CNR) calculated for quantitative analysis. Image and depiction of cartilage, bone, and soft tissues were rated. Radiation doses were compared. Results: In FPCT, iodine concentrations positively correlated with CT numbers and noise of contrast material and with radiation dose (r = 0.713-0.996, p < 0.05 each). At an iodine concentration of 45mg/ml, CNR of cartilage and soft tissues were highest for all FPCT acquisitions and higher than in MDCT. The 20-s FPCT run performed best for image quality and depiction of anatomical structures and was rated overall equal to MDCT (p = 0.857). Conclusion: The optimal iodine concentration for C-arm FPCT arthrography in this study is 45mg/ml, leading to superior CNR and image quality for an optimal FPCT protocol compared with standard MDCT arthrography in human cadaveric joint

MRI-based Surgical Planning for Lumbar Spinal Stenosis

The most common reason for spinal surgery in elderly patients is lumbar spinal stenosis(LSS). For LSS, treatment decisions based on clinical and radiological information as well as personal experience of the surgeon shows large variance. Thus a standardized support system is of high value for a more objective and reproducible decision. In this work, we develop an automated algorithm to localize the stenosis causing the symptoms of the patient in magnetic resonance imaging (MRI). With 22 MRI features of each of five spinal levels of 321 patients, we show it is possible to predict the location of lesion triggering the symptoms. To support this hypothesis, we conduct an automated analysis of labeled and unlabeled MRI scans extracted from 788 patients. We confirm quantitatively the importance of radiological information and provide an algorithmic pipeline for working with raw MRI scans

Diffusion tensor imaging of the median nerve: intra-, inter-reader agreement, and agreement between two software packages

Objective: To assess intra-, inter-reader agreement, and the agreement between two software packages for magnetic resonance diffusion tensor imaging (DTI) measurements of the median nerve. Materials and methods: Fifteen healthy volunteers (seven men, eight women; mean age, 31.2years) underwent DTI of both wrists at 1.5T. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) of the median nerve were measured by three readers using two commonly used software packages. Measurements were repeated by two readers after 6weeks. Intraclass correlation coefficients (ICC) and Bland-Altman analysis were used for statistical analysis. Results: ICCs for intra-reader agreement ranged from 0.87 to 0.99, for inter-reader agreement from 0.62 to 0.83, and between the two software packages from 0.63 to 0.82. Bland-Altman analysis showed no differences for intra- and inter-reader agreement and agreement between software packages. Conclusion: The intra-, inter-reader, and agreement between software packages for DTI measurements of the median nerve were moderate to substantial suggesting that user- and software-dependent factors contribute little to variance in DTI measurement