Objective—To assess the impact of cycles of freezing and thawing on magnetic resonance (MR) images (obtained by use of a 3-T magnet) of equine feet examined ex vivo. Sample—9 forelimbs from 9 horse cadavers. Procedures—9 forefeet underwent MR imaging first at ambient temperature within 12 hours after the horses' death and then after each freezing-thawing cycle. Three digits underwent freezing and thawing (at 4°C for 36 hours) 2 times, 3 digits underwent freezing and thawing (at 4°C for 36 hours) once and rescanning after 24 hours at ambient temperature, and 3 digits underwent freezing and thawing at ambient temperature for 24 hours once. Images of the digits obtained prior to freezing were subjectively compared with images obtained after freezing and thawing. Changes in the signal-to-noise ratio between examinations were assessed. Results—Overall image quality was considered unchanged except for the hoof capsule. Quantitative analysis revealed signal-to-noise ratio changes in bone marrow, soft tissues, and hoof capsule induced with both thawing processes. The signal-to-noise ratio in the sy-novial recess of the distal interphalangeal joint significantly increased as a result of thawing at4°C. Conclusions and Clinical Relevance—Although overall image quality was considered unchanged except for the hoof capsule, results suggested that changes induced in cadaver limbs following freezing and thawing, which are probably attributable both to modified and inhomogeneous temperature distribution and direct tissue damage, may alter the reliability of signal intensity in ex vivo MR examinations.

The aim of this study was to evaluate and compare the effects of single doses of butorphanol, morphine, and tramadol on gastrointestinal motility in rabbits (Oryctolagus cuniculus) using non-invasive imaging methods, such as radiographic barium follow through and ultrasonographic contraction counts. Time-lapse radiographic and ultrasound examinations were performed before and after a single intramuscular dose of 5 mg kg⁻¹ butorphanol, 10 mg kg⁻¹ morphine, or 10 mg kg⁻¹ tramadol. Pyloric and duodenal contraction counts by ultrasonography and radiographic repletion scores for the stomach and caecum were analysed using a mixed linear model. No significant effect was noted on ultrasound examinations of pyloric and duodenal contractions after administration of an opioid treatment. Morphine had a significant effect on the stomach and the caecum repletion scores, whereas butorphanol had a significant effect only on the caecum repletion score. Tramadol had no significant effect on the stomach or caecum repletion scores. The present findings suggest that a single dose of 5 mg kg⁻¹ butorphanol or 10 mg kg⁻¹ morphine temporarily slows gastrointestinal transit in healthy rabbits, preventing physiological progression of the alimentary bolus without the induction of ileus. In contrast, a single dose of 10 mg kg⁻¹ tramadol has no such effects.