J. Fritz

The Role of Dynamic Contrast-Enhanced MRI in the Differential Diagnosis of Psoriatic and Rheumatoid Arthritis

OBJECTIVEnThe purpose of this study was to investigate the role of dynamic contrast-enhanced MRI in the differential diagnosis of psoriatic and rheumatoid arthritis in the hand and wrist.nnnSUBJECTS AND METHODSnForty-five consecutive patients (31 patients with rheumatoid arthritis and 14 patients with psoriatic arthritis) were examined in a 3-T whole-body MR unit. After contrast injection, a 3D encoded spoiled gradient-echo sequence was used for measurement of the time course of contrast-medium uptake in the synovial tissue. On the basis of the gained uptake curves, the rate of early enhancement was calculated after 35 and 52 seconds, and the relative enhancement rate was calculated after 35 seconds, 52 seconds, 3 minutes, and 15 minutes (late enhancement). Dynamic contrast-enhanced MRI rates of patients with rheumatoid arthritis and psoriatic arthritis were compared and correlated with laboratory and clinical data.nnnRESULTSnA statistically significant difference between the two groups was found regarding the relative enhancement rate after 15 minutes (p < 0.01). In contrast, no difference in relative enhancement rate was found 35 seconds, 52 seconds, or 3 minutes after contrast injection (p = 0.695, p = 0.573, and p = 0.278, respectively). Regarding the rate of early enhancement at 35 and 52 seconds, no significant difference between patients with rheumatoid arthritis and those with psoriatic arthritis was found. Significant correlations were found between inflammatory parameters and dynamic contrast-enhanced parameters in patients with rheumatoid arthritis but not in those with psoriatic arthritis.nnnCONCLUSIONnFifteen minutes after contrast injection, a statistically significant difference between rheumatoid arthritis and psoriatic arthritis was found in synovial enhancement that might play an important role in differentiating the two diseases.

Bipolar radiofrequency ablation using internally cooled electrodes in ex vivo bovine liver: prediction of coagulation volume from applied energy.

Objective: We sought to evaluate the relationship between parameters of bipolar radiofrequency (RF) ablation using internally cooled electrodes. Materials and Methods: Bipolar RF ablations (n = 24) were performed in ex vivo bovine liver using an internally cooled applicator with 2 electrodes located on the same shaft. The power-output was systematically varied (20–75 W). On the basis of our experimental data, mathematical functions were fitted and the goodness-of-fit was assessed by the parameter R2. Results: The duration to induce an increase of tissue resistance and the amount of applied energy increased with a decreased power-output. The maximum short-axis was 4.5 cm (20 W) and required an application of 64 kilojoules (kJ). The volume of coagulation can be determined as a function of the duration of energy application (R2 = 0.954) and the amount of applied energy (R2 = 0.945). Conclusion: The amount of applied energy and the duration of energy application can predict the volume of induced coagulation and may be useful to control internally cooled bipolar RF ablation.

Contrast enhanced MR-guided biopsy of hepatocellular carcinoma.

Magnetic resonance (MR)–guided liver biopsy was performed in three patients with hepatocellular carcinoma. The tumor was considered (n = 2) or proven (n = 1) inaccessible with ultrasound or computed tomographic guidance. Because all lesions were poorly delineated on nonenhanced MR imaging, contrast agents (Gd-BOPTA, n = 1; ferucarbotran, n = 2) were applied to facilitate biopsy in an open low-field scanner. Postcontrast tumor conspicuity was fair in the patient receiving Gd-BOPTA and excellent in both patients receiving ferucarbotran, and biopsy was successful in all cases.

Magnetic resonance-guided transcortical biopsy of bone marrow lesions using a magnetic resonance imaging-compatible piezoelectric power drill: preliminary experience.

König CW, Trübenbach J, Böhm P, et al. Magnetic resonance-guided transcortical biopsy of bone marrow lesions using a magnetic resonance imaging-compatible piezoelectric power drill: Preliminary experience. Invest Radiol 2003;38:159–163. Rationale and Objectives. To test utility and specific properties of a commercially available MRI compatible power drill for MR guided transcortical bone biopsy. Methods. In 17 patients MR-guided bone biopsy was performed in an open low-field scanner (0.2 T), using a piezoelectrically powered drilling machine. Target lesions were osteoblastic in four and nonsclerosed intramedullary in 13 cases. Titanium drills sized 3 to 4 mm and an outer cannula were coaxially used for power assisted cortical trephination. For intramedullary lesion sampling, spring loaded biopsy guns and sharpened cannulas were additionally applied in seven and fluid aspiration in two patients, respectively. Results. The piezoelectric device proved to be fully MR compatible. Trephination and subsequent biopsy was successful in all patients without major complications. The drilling procedure could entirely be performed inside the magnet in case of a lateral approach (n = 11). The net drilling time averaged 7.8 minutes for trephination of nonimpaired diaphyseal bone, but was up to 50 minutes in case of thickened femoral bone. Procedures were complicated by frequent drill loosening, drill obstruction by cortical bone (n = 4) and impaired periosteal grip (n = 5) with damage to the outer cannula (n = 3). Conclusions. The piezoelectric power drill can be applied safely in a low-field MRI environment and is a valuable tool to facilitate transcortical bone biopsy.

Magnetic resonance spin-labeling perfusion imaging of synovitis in inflammatory arthritis at 3.0 T

ObjectiveThe aim of this study was to test the feasibility of arterial spin labeling (ASL) perfusion imaging of synovitis in inflammatory joint diseases on a clinical 3.0xa0T whole-body scanner.Materials and methodsFifteen patients (geometric mean 47xa0years, range 8–69xa0years) with different types of inflammatory arthritis of the finger or wrist joints participated in the study. In addition to conventional spin-echo and dynamic contrast-enhanced FLASH3D sequences, a novel spin-labeling technique (FAIR-TrueFISP) for quantitative assessment of tissue perfusion was applied. Perfusion maps were calculated pixel-wise by means of the extended Bloch equations.ResultsPerfusion maps showed good image quality with clear visualization of hyperaemia in synovitis. The computed perfusion maps corresponded best to subtraction images of the dynamic series from 30 to 60xa0s after contrast-medium injection. The quantitative perfusion values of synovitis showed a good correlation with the disease activity. Perfusion values for inflamed synovium in phase of high activity were up to 230xa0ml/100xa0g tissue/min.ConclusionThe proposed modality allows for the assessment of disease activity in arthritis without the application of contrast-medium offering a new tool for therapy monitoring. As the technique provides quantitative information on hyperaemia, it potentially offers new insights in the pathophysiology of arthritic diseases.

La Résonance Magnétique Interventionnelle en pathologie ostéoarticulaire

Magnetic resonance (MR) imaging is well established for the diagnosis of musculoskeletal diseases. The excellent tissue contrast and the multiplanar imaging capability have both contributed to the improvement of this technique. The development of fast acquisition techniques, sufficient patient access obtained with open magnet configurations and advances in the technology of MR compatible instruments allow a new approach to interventional radiology. These recently commercially available open-bored high-field magnets allow standard interventions such as biopsies or intra-articular infiltrations. Moreover, new interventions e.g. preoperative marking of soft tissue or bone marrow tumors are now possible with the better tissue contrast of MR imaging.

Chronische Arthritis im Kindesalter: Radiologische Charakteristika und Spektrum der Entitäten der ILAR-Klassifikation für die juvenile idiopathische Arthritis (JIA)

Die chronische Arthritis ist eine der haufigsten rheumatischen Erkrankungen bei Kindern. Sie ist ebenfalls eine der haufigeren chronischen Erkrankungen im Kindesalter und ein wichtiger Grund fur Langzeitbehinderungen. Die chronische Arthritis fasst eine Gruppe von ahnlichen rheumatischen Erkrankungen zusammen. Die verschiedenen Entitaten manifestieren sich generell als Arthritis des appendikularen Skeletts. Klinisch und radiologisch zeigen sich jedoch unterscheidbare Formen. Basierend auf einem oligo- oder polyarthritischen Bild oder einer systemischen Manifestationsform unterscheidet die ILAR-Klassifiktion der JIA sieben Enitaten- und Untergruppen. Weitere Grosen sind der Rheumafaktor, HLA-B27 und die Psoriasis. Die ILAR-Klassifiktion der JIA unterscheidet folgende Entitaten: Oligoarthritis, Polyarthritis (Rheumafaktor positiv und negativ), systemische Arthritis, Psoriasis-Arthritis, Enthesitis-assoziierte Arthritis und die undifferenzierte Arthritis. Die Rolle der radiologischen Diagnostik besteht aus der initialen Diagnose und Klassifikation der JIA, der differenzialdiagnostischen Abklarung, der Beurteilung des Krankheitsverlaufs und Therapiemonitoring sowie der Detektion von Komplikationen. Lernziele: Korrespondierender Autor: Fritz J Eberhard-Karls-Universitat Tubingen, Radiologische Diagnostik, Hoppe-Seyler-Strasse 3, 72076 Tubingen E-Mail: jan.fritz@gmx.net

Clinical applications of interventional magnetic resonance imaging in pain therapy of the spine

Objectifs The purpose of this presentation is to show the spectrum of interventional MR imaging procedures in spinal pain therapy and to demonstrate the application of MR-Fluoroscopy. Materiels et methodes The introduction of new MR-Scanners with a larger bore and a shorter magnet (Magnetom ESPREE, Siemens, Erlangen, Germany) and the development of MR-compatible instruments lead to new therapeutic possibilities for interventional radiologists. Resultats General concepts are illustrated in reference to procedures including lumbar sympatholysis, facet joint blockade, sacroiliac joint infiltration and periradicular infiltration. The ability of pre-and procedural MR imaging provides the physicist with exclusive information for evaluation of the region of interest and for planning of the procedure. The development of ultra-fast acquisition techniques and display of MR images enables near real-time imaging (MR-Fluoroscopy or step-by-step) for continuous action control even in low-field MR-Scanners. Conclusion Pain therapy in an interventional MR-unit is a safe and feasible procedure without irradiation. Multiplanar imaging for exact positioning of the instrument and the use of fluoroscopy to save time are the main advantages of the MR guidance. Performing the diagnosis and the therapy in the same session is another potential advantage.