Impact of successive freezing-thawing cycles on 3-T magnetic resonance images of the digits of isolated equine limbs

Abstract

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. 9 forelimbs from 9 horse cadavers. 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. 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 synovial recess of the distal interphalangeal joint significantly increased as a result of thawing at 4°C. 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.