Superior scanner a step ahead in revealing hidden injuries in horses

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The photo on the left shows the portable PET scanner used for equine PET imaging. On the right, the left foot of a horse is being imaged with the system.
The photo on the left shows the portable PET scanner used for equine PET imaging. On the right, the left foot of a horse is being imaged with the system.

The advantages of PET (positron emission tomography) scanning in horses has been proven in a test run of a new scanner by UC Davis in California.

UC Davis is the first equine hospital to offer PET scans, and in August and September six horses were scanned to test the scanner and validate a clinical protocol. The horses were also scanned by computed tomography (CT) at the same time, as well as MRI and scintigraphy.

Sagittal (A), dorsal (B) and transverse (C, D) fused PET/CT images of the right carpus of a 2-year-old Thoroughbred racehorse. There is marked increased radiopharmaceutical uptake at the distal medial aspect of the radial carpal bone and proximal medial aspect of the third carpal bone.
Sagittal (A), dorsal (B) and transverse (C, D) fused PET/CT images of the right carpus of a 2-year-old Thoroughbred racehorse. There is marked increased radiopharmaceutical uptake at the distal medial aspect of the radial carpal bone and proximal medial aspect of the third carpal bone.

Stress remodeling lesions were documented, in particular in the fetlock and the carpus (right). Several of these lesions were not apparent on scintigraphy, CT or MRI, confirming the advantages of PET imaging. The pattern of uptake observed on the PET images matches areas of known occurrence of lesions. PET appears to be the most sensitive technique to detect these lesions. Further research is planned on the Thoroughbred fetlock, as UC Davis veterinarians believe that PET has the potential to help prevent catastrophic injuries in racehorses.

For the tests, scans were performed under the same anesthetic procedure, instead of two separate anesthesias as with the initial cases last year tested on a prototype of the scanner. The anesthesia time remained under three hours with about 90 minutes for the PET scan and 30 minutes for the CT scan. During this time, up to six different areas were able to be imaged, for example both front feet, both front fetlocks and both carpi.

The six horses enrolled were all racehorses recently retired from the track or currently training on a treadmill at the California Animal Health and Food Safety Laboratory.

In early October, a clinical trial was started in client-owned animals funded by the Grayson-Jockey Club Research Foundation and UC Davis’ Center for Equine Health. The trial enrolls horses with lameness, already imaged with either scintigraphy or MRI, but requiring additional information for diagnosis or treatment planning. Currently, four Warmblood horses have been imaged.

The lesions identified included subchondral bone remodeling in the fetlock and in the tarsus, remodeling of the navicular bone, focal active resorption of the coffin bone, osseous remodeling at the insertion of the suspensory ligament (right) and remodeling of the canon bone.

 Transverse PET (A), fused PET/CT (B) and CT (C) images through the right front proximal metacarpus of an 8-year-old Warmblood gelding. Local analgesia had identified pain in this area. The PET images demonstrate marked focal increased uptake at the palmar aspect of the third metacarpal bone at the lateral aspect of the origin of the suspensory ligament. The CT did not demonstrate significant abnormality in this area.
Transverse PET (A), fused PET/CT (B) and CT (C) images through the right front proximal metacarpus of an 8-year-old Warmblood gelding. Local analgesia had identified pain in this area. The PET images demonstrate marked focal increased uptake at the palmar aspect of the third metacarpal bone at the lateral aspect of the origin of the suspensory ligament. The CT did not demonstrate significant abnormality in this area.

The first manuscript regarding use of PET in the horse was recently published in the November/December issue of Veterinary Radiology and Ultrasound. A keynote lecture on equine PET was presented in October by Dr. Mathieu Spriet at the Annual Conference of the American College of Veterinary Radiology in Orlando, Florida.

An abstract was also presented in August at the Annual European Veterinary Diagnostic Imaging Meeting in Poland and received the best poster award. Future presentations are planned for the American Association of Equine Practitioners Annual Convention in December and at the Lake Tahoe Equine Conference in January.

UC Davis’s new scanner weighs only 50 pounds, and was specifically designed for animal imaging.

UC Davis' new portable PET scanner is the first of its kind to be used to image horses.
UC Davis’ new portable PET scanner is the first of its kind to be used to image horses.

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