¹⁸Fluorine‐fluorodeoxyglucose positron emission tomography for assessment of deep digital flexor tendinopathy: An exploratory study in eight horses with comparison to CT and MRI

Abstract

Lesions of the deep digital flexor tendon (DDFT) are a cause for foot lameness in horses.Positron emission tomography (PET) could provide valuable information regarding the metabolic activity of these lesions. The aims of this exploratory, prospective, methods comparison study were to assess the ability of 18 fluorine-fluorodeoxyglucose ( 18 F-FDG) PET to detect DDFT lesions and to compare the PET findings with CT and MRI findings. Eight horses with lameness due to pain localized to the front feet were included. Both front limbs of all horses were imaged with 18 F-FDG PET, noncontrast CT, and arterial contrast-enhanced CT; 11 limbs were also assessed using MRI. Two observers graded independently 18 F-FDG PET, noncontrast CT, arterial contrast CT, T1-weighted (T1-w) MRI, and T2-weighted (T2-w)/STIR MRI. Maximal standardized uptake values were measured. Lesions were found in seven of 16 DDFT on PET, 12 of 16 DDFT on noncontrast CT, six of 15 DDFT on arterial contrast CT, eight of 11 DDFT on T1-w MRI, and six of 11 DDFT on T2-w/STIR MRI. Positron emission tomography was in better agreement with arterial contrast CT (Kappa-weighted 0.40) and T2-w/STIR MRI (0.35) than with noncontrast CT (0.28) and T1-w MRI (0.20). Maximal standardized uptake values of lesions ranged from 1.9 to 4.6 with a median of 3.1.Chronic lesions with scar tissues identified on noncontrast CT or T1-w MRI did not have increased 18 F-FDG uptake. These results demonstrated that 18 F-FDG PET agreed more closely with modalities previously used to detect active tendon lesions, i.e. arterial contrast CT and T2-w/STIR MRI. 18 Fluorine-fluorodeoxyglucose PET can be used to identify metabolically active DDFT lesions in horses.

Validation of a dedicated positron emission tomography scanner for imaging of the distal limb of standing horses

“…As shorter scan times are more convenient with standing horses, in order to reduce the risk of scan abortion due to motion, the scanning strategy with standing horses is different from anesthetized horses. In previous studies scanning horses under general anesthesia, the full available axial field of view (22 cm) was most commonly used to maximize anatomical coverage 1,11,13,14 . With standing scans, a smaller field of view focused on the area of interest is advisable.…”

“…In previous studies scanning horses under general anesthesia, the full available axial field of view (22 cm) was most commonly used to maximize anatomical coverage. 1,11,13,14 With standing scans, a smaller field of view focused on the area of interest is advisable. As all scans of optimal quality were obtained with an axial FOV/scan duration ratio lower than 4 cm/minute, this represents a convenient guideline to determine scan duration.…”

“…13 18 F-Fluorodeoxyglucose (FDG) has been reported for assessment of deep digital flexor tendinopathy. 14 The main limitation of equine PET was the requirement for general anesthesia, which limited the availability of the technique as a screening tool or for follow-up scans. A proof-of-concept study demonstrated that it was possible to obtain PET images in standing horses: two horses were imaged using a ring of PET detectors set flat on the ground.…”

“…18 F‐NaF PET is also useful in the assessment of lameness localized to the equine foot, as illustrated by the ability to recognize chondrosesamoidean ligament enthesopathy 13 . 18 F‐Fluorodeoxyglucose (FDG) has been reported for assessment of deep digital flexor tendinopathy 14 . The main limitation of equine PET was the requirement for general anesthesia, which limited the availability of the technique as a screening tool or for follow‐up scans.…”

Standardized uptake values and attenuation correction in 18F‐sodium fluoride PET of the equine foot and fetlock

“…Previously published equine 18 F‐NaF PET studies relied on NAC PET data 1,3 . Recently, dedicated software (Galatea, BrainBiosciences Inc.) has become available, allowing the production of CTAC via coregistration of PET data with CT data acquired on a separate scanner 13 …”