Maximal standardized uptake values (SUVmax) are commonly used for the interpretation of PET studies. Limited information regarding the SUVmax of 18F‐NaF PET in horses is currently available in the literature. The goals of this retrospective secondary analysis study were to provide reference values for 18F‐NaF SUVmax in the equine distal extremity and assess the effect of attenuation correction. Nonattenuation corrected (NAC) and CT‐based attenuation corrected (CTAC) SUVmax were obtained from 19 feet and 19 fetlocks. Twenty regions of interest (ROIs) were defined for the foot and 22 for the fetlock. Areas presenting abnormal uptake were excluded. The overall NAC and CTAC SUVmax were 3.6 +/‐ 1.5 (mean +/‐ sd) and 5.0 +/‐ 1.8 for the feet and 2.9 +/‐ 1.1 and 3.8 +/‐ 1.4 for the fetlocks, respectively. The 3 ROIs showing the highest attenuation correction were the navicular center (83.4%), navicular flexor surface (74.9%) and distal phalanx flexor surface (81.3%), whereas attenuation correction was only 5.2% at the dorsal aspect of the proximal phalanx. Significant SUVmax differences were observed between the different ROIs (P < 0.0001), with the toe (CTAC SUVmax 7.7 +/‐ 3.7), dorsal (7.5 +/‐ 1.9) and central (6.1 +/‐ 2.2) ROIs of the distal phalanx being significantly higher than those of the other areas. This study demonstrates that attenuation correction affects SUVmax in the equine distal extremity and should be performed if CT data are available. However, as the maximal attenuation correction results in less than doubling the signal intensity, nonattenuation corrected images likely remain relevant for subjective clinical interpretation.

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.

No abstract

A new approach for the detection of head motions during PET scanning is presented. The proposed system includes 4 modules, which are: input module, face segmentation, facial landmark detection, and head movement estimation. The developed system is tested on pictures monitoring a subject's head while simulating PET scanning (n=12) and face images of subjects with different skin colours (n=31). Experimental results show that the centres of chosen facial landmarks (eye corners and middle point of nose basement) can be detected with high precision (1r0.64 pixels). Processing of 2D images with known moving parameters demonstrates that the parameter movement in terms of rotation and translation along X, Y, and Z directions can be obtained very accurately via the developed methods.

No abstract