PET Final Research Report

Assessment of a new imaging technique to detect active lesions in the horse foot

FINAL REPORT CEH 15-01

a.  Project Title in lay terms:

Assessment of a new imaging technique to detect active lesions in the horse foot

b.  Investigators:
Mathieu Spriet, DVM, MS, DACVR, DECVDI

Larry Galuppo, DVM, DACVS

c.  Brief Background of the Problem:

Imaging of the horse foot has markedly improved over the past 15 years with the development of computed tomography (CT) and magnetic resonance imaging (MRI). We are now able to detect lesions that were unrecognized in the past. The current challenge is to distinguish between active lesions and chronic inactive lesions. This is important both for treatment of specific cases and for assessment of therapies in research projects.

d.  Hypothesis Statement:

An imaging technique never previously used in the horse, positron emission tomography (PET), will provide additional information for both soft tissue and osseous lesions, when compared with other available imaging modalities.

e.  Specific Objective(s) of the Study:

- Demonstrate the feasibility of PET imaging in the horse 

- Assess the information provided by PET for both soft tissue and osseous lesions 

- Compare PET results with findings from other imaging modalities

f.  Overview of Experimental Approach:

A compact portable PET scanner recently designed for imaging of human head will be used to image the equine distal limb. Image acquisition will be performed with horses under general anesthesia after injection of a radioactive tracer designed for PET imaging. CT and MRI will also be performed to correlate with the PET findings.

g. Results:

- 6 horses were imaged with the PET scanner (Figure 1), high quality images of the feet and fetlock were obtained on all of them.

- The imaging procedures were safe for horse and staff

-  A wide range of lesions were identified with PET, including:

- Tendon lesions with various level of activity (Figure 2)

- Abnormal activity in the hoof of a horse with laminitis (Figure 2)

- Lesions at the attachment of tendons and ligaments not identified with other imaging modalities (Figure 3)

- Lesions of bone and joint not identified with other imaging modalities (Figure 3)

h. Benefits to the Equine Industry:

In comparison with other imaging modalities currently available in the horse, PET brings functional information. This provides additional information for soft tissue lesions and allows the identification or bone or joint lesions not appreciated with other imaging modalities. PET will become an invaluable research tool in particular for tendon and laminitis research. PET also has direct clinical applications for the early identification of bone and joint lesions. 

Figure 1: The photo on the left shows the portable PET scanner. On the right, the left foot of a horse is imaged with the PET scanner.

Figure 2: PET images (left column), fused PET and CT images (central column) and CT images (right column). On the foot imaged in the top row, the arrows shows an active tendon lesion, most conspicuous on the PET images. The bottom row, shows a lack of radioactive uptake in the lamina of a horse with laminitis (arrowheads).

Figure 3: PET (left), CT (center) and fused PET/CT (right) images of the foot of a horse. The PET image on the top row shows marked increased uptake that is associated with an active fragment from the distal border of the navicular bone. On the bottom row, PET identified an active area of resorption at the axial aspect of the medial palmar process of the distal phalanx at a site of ligament attachment. This lesion was not identified on the CT.