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The use of small field of view 3T MRI for identification of articular cartilage defects in the canine stifle: An ex vivo cadaveric study

Noninvasive identification of canine articular cartilage injuries is challenging. The objective of this prospective, cadaveric, diagnostic accuracy study was to determine if small field-of-view, three tesla magnetic resonance imaging (MRI) was an accurate method for identifying experimentally induced cartilage defects in canine stifle joints. Forty-two canine cadaveric stifles (n = 6/group) were treated with sham control, 0.5, 1.0, or 3.0 mm deep defects in the medial or lateral femoral condyle. Proton density-weighted, T1-weighted, fast-low angle shot, and T2 maps were generated in dorsal and sagittal planes. Defect location and size were independently determined by two evaluators and compared to histologic measurements. Accuracy of MRI was determined using concordance correlation coefficients. Defects were identified correctly in 98.8% (Evaluator 1) and 98.2% (Evaluator 2) of joints. Concordance correlation coefficients between MRI and histopathology were greater for defect depth (Evaluator 1: 0.68-0.84; Evaluator 2: 0.76-0.83) compared to width (Evaluator 1: 0.30-0.54; Evaluator 2: 0.48-0.68). However, MRI overestimated defect depth (histopathology: 1.65 ± 0.94 mm; Evaluator 1, range of means: 2.07-2.38 mm; Evaluator 2, range of means: 2-2.2 mm) and width (histopathology: 6.98 ± 1.32 mm; Evaluator 1, range of means: 8.33-8.8 mm; Evaluator 2, range of means: 6.64-7.16 mm). Using the paired t-test, the mean T2 relaxation time of cartilage defects was significantly greater than the mean T2 relaxation time of adjacent normal cartilage for both evaluators (P < 0.0001). Findings indicated that MRI is an accurate method for identifying cartilage defects in the cadaveric canine stifle. Additional studies are needed to determine the in vivo accuracy of this method.

Listeria Brainstem Encephalitis in Small Ruminants: Correlation of Magnetic Resonance Imaging and Histopathology.

Listeria Brainstem Encephalitis in Small Ruminants: Correlation of Magnetic Resonance Imaging and Histopathology Christina Stahl1, Anna Oevermann2, Daniela Gorgas1 1Clinical Radiology, Department of Clinical Veterinary Medicine, Vetsuisse-Faculty, University of Bern, Switzerland 2Neurocenter, Department of Clinical Research and Veterinary Public Health, Vetsuisse-Faculty, University of Bern, Switzerland Abstract Brainstem encephalitis is an intriguing form of Listeria monocytogenes central nervous system (CNS) infection in humans and ruminants and has a high fatality rate. However, intra vitam diagnosis remains difficult in both species (1, 2). We performed MRI of affected small ruminants, in which Listeria brainstem encephalitis is a common CNS disease, and correlated MRI features with histopathology in order to define MRI criteria for the diagnosis of listeria brainstem encephalitis. Fifteen small ruminants (nine sheep, six goats) with listeriosis underwent MRI examination of the brain using a 0.3 T system (five animals) and 1.0 T system (ten animals) including T2w, FLAIR and T1w sequences pre and post Gadolinium administration. Listeria brainstem encephalitis was confirmed by histopathology, and histopathological changes were correlated to MRI features. On MRI, lesions were best visualized in T2-weighted sequences. In all animals they were characterized by asymmetric increased signal intensity in the rhombencephalon in T2w and FLAIR sequences. The lesions showed a variable pattern and distribution, ranging from patchy with ill defined borders to diffusely affecting the entire cross-sectional area of the brainstem. Few animals had lesions in the diencephalon (three animals), whilst histopathologically detectable lesions commonly extended to the diencephalon and involved cranial nerve roots (twelve animals). The lesions were iso- to mildly hypointens in T1w sequence. Mild to moderate patchy or ring-like contrast uptake was observed in the rhombencephalon of five animals (one sheep, four goats), which showed vascular damage and perivascular fibrin accumulation on light microscopy. In the brainstem, the asymmetric T2-hyperintense lesions observed by MRI correlated well with the inflammatory infiltrates observed in histopathology (3). However, lesions in the diencephalon, cranial nerves and meninges of rostral brain areas were rarely detected by MRI, indicating that MRI underestimates involvement of the rostral brain and brain associated structures. Contrary to reported human cases of neurolisteriosis (4), contrast uptake was an inconsistent finding occurring in the rhombencephalon of only five animals.