Magnetic resonance imaging (MRI) was performed on seven patients with aseptic osteonecrosis (n = 4) and osteochondritis dissecans (OCD; n = 3) of the elbow. Precontrast MRI was superior to plain radiographs, which did not show any abnormality in three cases of osteonecrosis. On gadopentetate-dimeglumine-enhanced T1-weighted images, which were obtained in three patients with osteonecrosis and three patients with OCD, all cases of osteonecrosis demonstrated homogeneous enhancement of the lesions. All cases of OCD were diagnosed on plain radiographs. On MRI one showed significant enhancement of the loose body. In another case an incompletely enhancing loose body was surrounded by a diffusely enhancing region. In the third patient only a small marginal enhancement of the defect was observed. Our results suggest that MRI can improve the accuracy in diagnosis of aseptic osteonecrosis of the elbow. The use of gadopentetate dimeglumine allows the viability of the lesions or the loose bodies to be demonstrated and reparative tissue to be detected.

The results of our study demonstrate the usefulness of fractal texture analysis for classification of lung tumors on chest radiographs.

20 patients with osteochondritis dissecans were studied by MRI over a period of 3-34 months in order to observe healing and determine the viability of the loose fragment. After intravenous contrast, there was increased signal intensity at the junction between the fragment and the epiphyseal bed on T2-weighted sequences; this was interpreted as fibrous granulation tissue surrounding the fragment. The fragments themselves also showed increased signal intensity after gadolinium-DTPA. Intravenous gadolinium allows accurate evaluation of the junctional zone between the fragment and the epiphyseal bed by demonstrating fibrous, vascularised granulation tissue. This can be distinguished from synovial fluid, and it also demonstrates viability of the fragment.

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Zusammenfassung In einer klinischen Studie konnten mit der Magnetresonanztomographie (MRT) bei 17 Pferden Erkrankungen der Backenzähne nachgewie-sen und differenziert werden. Die Veränderungen wurden mit Befunden verglichen, die bei 47 Pferden ohne Zahnerkrankungen erhoben wurden. Von allen Pferden wurde der Zahnstatus erhoben und es lagen Röntgenuntersuchungen vor. Abweichende und normale Befunde wurden beschrieben und zugeordnet. Zähne und umgebende Strukturen können mit der MRT gut beurteilt werden. Obwohl Zahnhart-substanzen und Alveolarknochen signallos erscheinen, sind sie eingeschränkt beurteilbar. Folgende Strukturen werden beschrieben: Zähne und ihre Umgebung, Angesichtsdeformationen mit und ohne Fistelbildung, Wurzelspitzengranulome, überzählige Zähne, Zahnkeime sowie Veränderungen des Canalis infraorbitalis. Dabei wird das physiologische und pathologische Bild gegenüber gestellt. Die Beurteilung der Zähne ist trotz der eingeschränkten Hartsubstanzdifferenzierung durch die MRT möglich. Über Pulpen, den Zahnhalteapparat, den umge-benden Knochen oder die Zahnanlagen können wertvolle Zusatzinformationen gewonnen werden. Schlüsselwörter: MRT / Pferd / Kopf / Backenzähne / Zahnerkrankungen Diagnostic of equine cheek tooth diseases with magnetic resonance imaging Equine cheek tooth diseases diagnosed by magnetic resonance imaging (MRI) could be detected and differentiated in a clinical study with 17 diseased horses. These changes were compared with the results which were found in 47 horses without any dental disease. In addition to MRI images, radiographs from all horses were available for evaluation. Normal findings and changes were described and assigned. Judgement of teeth and surrounding tissues was based on MRI images was very good. Although dental hard tooth substance and alveo-lar bone do not appear with a signal they could be judged with restriction.