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This prospective, cross-sectional, pilot study aimed to investigate the effects of furosemide as a diuretic on the image quality of bone scintigraphy performed using 99m Tc-HDP and to investigate the impact of furosemide on the radiation dose rate. Thirty-one horses undergoing bone scintigraphy were included. The horses were divided into the control (n = 14) and furosemide group (n = 17), which received 1 mg/kg furosemide intravenously 1 h post 99m Tc-HDP administration. The image quality was assessed subjectively and semi-quantitatively. The bone-to-soft tissue (B:S) ratio was calculated from the counts per pixel of regions of interest (ROI) positioned over the left radial diaphysis (bone ROI) and its caudal soft tissue area (soft tissue ROI). The radiation rate dose (μSv/h) of both groups was measured at 0, 3, 6, 12, 18, and 24 h post 99m Tc-HDP administration at a distance of 0, 30, and 100 cm from the head, kidney, and pelvis. The results showed no significant differences in the B:S ratio or the radiation dose rate observed between the groups. However, the radiation dose rate decreased by 56% at 3 h post 99m Tc-HDP administration and keeping a distance of 30 cm reduced the radiation dose rate by 65%. Administering furosemide does not improve the image quality or reduce the radiation dose rate. The authors recommend commencing with bone scintigraphy 3 h post 99m Tc-HDP administration and keeping at least a distance of 30 cm from the horse to reduce the staff radiation dose., (© 2020 American College of Veterinary Radiology.)

Abomasal hypomotility is one of the important causes of neonatal mortality in small ruminants. Various pharmaceutical agents have been studied to address this problem in large ruminants. The aim of this study was to determine the effect of parenteral administration of tylosin and ivermectin on abomasal emptying rate in neonatal suckling lambs. Abomasal emptying rate was assessed using nuclear scintigraphic method in 10 healthy female Iranian fat tailed Ghezel lambs. Each lamb was tested three times, once as a control (1 ml of saline 0.9%, IM) and twice after the injection of tylosin (17.6 mg/kg, IM) and ivermectin (200 μg/kg, SC) in a crossover study. Based on radiopharmaceutical counts, remnant activity in abomasums at 90 min were 48.3 ± 3.5, 45.6 ± 7.5 and 41.6 ± 2.9% in control, tylosin and ivermectin groups, respectively. Administration of tylosin (p = 0.049) and ivermectin (p = 0.045) to lambs, significantly caused faster abomasal emptying rate compared to control. Evaluating the ROIs revealed that the half emptying time (T 1/2 ) in control, tylosin and ivermectin groups were 67.1 ± 8.6, 62.6 ± 14.2 and 54.3 ± 9.9 min, respectively. These difference between all groups, statistically were significant (p = 0.026). However, the clinical efficacy of abomasal emptying rate facilitating by tylosin or ivermectin administration in lambs remains to be determined., (Copyright © 2020. Published by Elsevier Ltd.)

Objective: To assess the influence of humeral stress fracture location on the time to return to racing and postinjury performance of thoroughbred racehorses., Study Design: Retrospective study (1992-2015)., Sample Population: Thoroughbred racehorses (n = 131) that presented for lameness with the sole diagnosis of humeral stress fractures in the lame limb, as determined by scintigraphy or radiology., Methods: Sex, fracture site, age, starts, earnings, and average earnings per race were examined for differences in pre-stress and post-stress fracture diagnosis for the entire population as well as individual stress fracture locations (general linear model, χ 2 tests). Pre-stress and post-stress fracture performance for the three stress fracture locations were assessed: (1) earnings pre-stress and post-stress fracture (Kruskal-Wallis one-way analysis of variance), (2) average earnings per start prefracture, and (3) average earnings per start postfracture (Wilcoxon signed-rank tests)., Results: Stress fracture locations were caudodistal (n = 36), craniodistal (n = 43), and caudoproximal (n = 52). One hundred ten of 131 horses raced postfracture, and 54 of 131 horses raced prefracture. Age at injury was 43.61 months caudodistal, 33.48 months caudoproximal, and 36.65 months craniodistal. Horses returned to race at a median of 244 days (range, 218-272). Postfracture earnings per start were greater for caudodistal vs caudoproximal (P = .04)., Conclusion: There were no differences in prefracture earnings or fracture site and sex or limb affected. Return-to-race time varied by location but not significantly. Differences in earnings preinjury and postinjury were not significant. Horses with a stress fracture at the caudodistal location earned significantly more compared with horses with a stress fracture at the caudoproximal location after they returned to race., Clinical Significance: Thoroughbred racehorses have a good prognosis for return to racing regardless of fracture location., (© 2020 The American College of Veterinary Surgeons.)

Background: Reflux and aspiration in people are associated with respiratory disease, whereas approximately 50% of healthy adults microaspirate without apparent consequence. In dogs, analogous information is lacking., Hypothesis: Healthy dogs commonly have gastroesophageal reflux and a proportion of these dogs will have laryngopharyngeal reflux with silent aspiration., Animals: Twelve healthy, client-owned dogs., Methods: Prospective study: Dogs were free-fed a meal containing (111 MBq) colloidal 99 m-technetium phytate. Dynamic-scans were performed 5 and 30 minutes postingestion. Time-activity curves, reflux margination, volume, frequency, and duration were evaluated over 7 regions of interest in dorsal ± left-lateral recumbency. Static scans (dorsal recumbency) were performed 2 and 18 hours postfeeding to detect aspiration. Reflux and aspiration were defined as counts ≥200% background activity ± decreased gastric counts. Between-group comparisons were performed by Wilcoxon rank-sum test or one-way ANOVA on ranks with significance of P < .05., Results: In this study, reflux of variable magnitude was detected in 12/12 dogs. No significant differences in outcome parameters were detected with recumbency (P > .05). Margination to the pharynx and proximal, middle, and distal esophagus was identified in 5/12, 2/12, 3/12, and 2/12 dogs, respectively. Median (IQR) reflux frequency and duration were 2 events/5 minutes (1-3.3 events/5 minutes) and 6 seconds (4-9 seconds) respectively. No dog had detectable aspiration., Conclusions and Clinical Importance: Nuclear scintigraphy can document reflux in dogs. Reflux, but not aspiration, is common in healthy dogs and must be considered when interpreting results in clinically affected dogs., (© 2020 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Background: Subchondral bone injury at the palmar/plantar aspect of the condyles of the third metacarpal/metatarsal bone (MC/MT3) commonly causes lameness and poor performance in racehorses. Injury occurs due to repetitive loading, the magnitude of which may be influenced by the position of the distal phalanx relative to the ground surface, i.e. the solar angle. The association of solar angle and injury at the palmar/plantar condyles of distal MC/MT3 therefore warrants investigation., Objectives: Investigate the relationship between solar angle and radiopharmaceutical uptake at the palmar/plantar aspect of distal MC/MT3 on scintigraphic images of racehorses., Study Design: Retrospective case-controlled study., Methods: Scintigraphic images of Thoroughbred racehorses presented for poor performance or lameness were graded for intensity of radiopharmaceutical uptake in the palmar/plantar aspect of distal MC/MT3. Solar angle was graded (positive, neutral or negative), referring to the angle of the solar plane of the distal phalanx relative to the ground surface. Repeatability of solar angle (n = 1226 limbs) and agreement with objective radiographic evaluation (n = 52 limbs) were evaluated. Prescintigraphy performance data were collected from race records. Associations between solar angle, performance and radiopharmaceutical uptake were investigated using multivariable logistic regression., Results: Repeatability of scintigraphic solar angle grading (κ = 0.89, 95% CI 0.87-0.91) and agreement of scintigraphic and radiographic solar angle (κ = 0.88, 95% CI 0.75-0.97) were excellent. Horses that performed best prior to presentation were more likely to have both greater radiopharmaceutical uptake and a neutral/negative solar angle. When controlling for prior performance, horses with neutral/negative forelimb solar angle were twice as likely to have moderate/marked radiopharmaceutical uptake than horses with positive solar angle (P<0.02). Horses with negative hindlimb solar angle were six times more likely to have moderate/marked radiopharmaceutical uptake than horses with positive/neutral solar angle (P<0.001)., Main Limitations: Population bias due to preselected hospital population., Conclusions: Both solar angle and race performance are independently associated with increased bone activity in the palmar/plantar aspect of the third metacarpal/tarsal condyles. The Summary is available in Portuguese - see Supporting Information., (© 2019 EVJ Ltd.)

Dental disorders are one of the top-ranking clinical domains in equine practice. Scintigraphy has emerged as a useful diagnostic imaging modality for equine dental diseases. There is a paucity of the normal scintigraphic uptake and its correlation with age. This prospective, cross-sectional, descriptive and pilot-designed study aimed to describe the radioisotope uptake (RU) patterns of the reserved crown and periodontal bone of the maxillary and mandibular cheek teeth (CT) in clinically sound horses and to evaluate the age effect on RU. For this purpose, 60 horses that underwent a bone scintigraphy for reason unrelated to head were included and divided equally into four age groups. Regions of interests (ROIs) were positioned around alveolar and periodontal bone of each maxillary and mandibular CT including their reserve crown, and a reference ROI positioned at the mandibular ramus. The count per pixel of each ROI was measured using a dedicated software and the RU ratio relative to the reference region was calculated. The results showed that the maxillary and mandibular CT had a standard RU pattern, where it increased from rostral to caudal, and peaked in the middle of dental arcades and decreased slightly towards the last CT. The maxillary CT had a higher RU compared with the mandibular CT, and there was no significant difference in the maxillary and mandibular CT uptake between age groups. This information may aid veterinarians evaluating potentially abnormal dental scintigraphy., Competing Interests: Competing interests: None declared., (© British Veterinary Association 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Ultrasound provides information on kidney morphology, but studies relating structural and functional abnormalities in chronic kidney disease (CKD) are lacking. The aim of this descriptive cross-sectional study was to compare individual kidney (IK) B-mode ultrasound abnormalities to IK glomerular filtration rate (GFR) estimated by scintigraphy normalized to plasma volume (PV) in dogs, to evaluate if ultrasonographic findings were associated with low IKGFR/PV. Eighty privately owned dogs with and without clinical suspicion of CKD were prospectively enrolled, and kidney ultrasound and IKGFR/PV were evaluated independently. Ultrasound images were assessed retrospectively for subjective abnormalities (shape, cortical, and medullary hyperechogenicity), and kidney size was measured. The normal IKGFR/PV cutoff was derived from dogs in the study group with no history and clinical signs of kidney disease and normal blood and urine results (n = 28) and was 16.84 mL/min/L. Kidneys were categorized into normal, mild, moderate, and severe ultrasound changes according to subjective ultrasound grades. Associations were found between low IKGFR/PV and abnormal kidney shape (P = .0004), cortical hyperechogenicity (P = .0008), medullary hyperechogenicity (P < .0001), and low kidney volume (P = .0092). Apart from the moderate and severe category comparison, IKGFR/PV value significantly decreased with increasing severity of category. The combination of ultrasonographic subjective abnormalities had a high sensitivity (93.8%) and moderate specificity (65.7%) for detecting low IKGFR/PV. Kidneys with normal IKGFR/PV had a low frequency of mild ultrasound changes. Findings indicate kidneys with increasing number and grade of subjective ultrasound abnormalities are more likely to have a lower IKGFR/PV., (© 2019 American College of Veterinary Radiology.)

Long bone fractures in racehorses may present as stress fractures which have a good prognosis, or complete fractures, which often result in a fatal outcome. In order to identify differences in modifiable management practices that may contribute to these outcomes, racing histories of horses with humeral or tibial fractures and of matched controls were examined. A retrospective case-control study of Australian Thoroughbred racehorses diagnosed with a fracture of the humerus or tibia by scintigraphy or at post-mortem between 2002 and 2016 was undertaken. Control horses were matched from the same race or trial on age and sex. Statistical analysis was performed using conditional logistic regression, χ 2 and Mann-Whitney U tests. More humeral fractures than tibial fractures were fatal (12/47, 26% vs. 3/35, 8.6%, P = 0.049). No differences in pre-injury racing histories were observed between cases and controls for humeral and tibial fractures. Both humeral and tibial fracture case horses were younger than the registered Thoroughbred racing population (P < 0.001), but horses sustaining humeral fractures were older than those with tibial fractures (3.3 ± 0.9 vs. 2.8 ± 0.8 years, P = 0.005) yet raced fewer times prior to the injury (0.5 ± 1.1 vs. 1.3 ± 1.7 races, P = 0.009). Horses with fatal humeral fractures were less likely to have raced than those with non-fatal humeral fractures (16.7% vs. 55.6%, P = 0.02). In conclusion, tibial and humeral fractures occur in young racehorses, and humeral fractures are more likely to be fatal in those with the least exposure to trialling and racing., (Copyright © 2019. Published by Elsevier Ltd.)

Objective: To evaluate agreement of 4 methods (Tikhonov gamma variate adaptive regularization of plasma concentration-time curve fitting applied to technetium Tc 99m diethylenetriamine pentaacetic acid [ 99m Tc-DTPA] plasma clearance [Tk-GV], plasma clearance of exogenous creatinine [CrCL], Gates gamma camera-based measurement method with 99m Tc-DTPA renal clearance and dynamic scintigraphy [GTS], and iohexol renal clearance assessed with dynamic CT with Patlak plotting [CT-Pp]) for measuring glomerular filtration rates (GFR) in healthy cats., Animals: 7 healthy, laboratory-raised cats., Procedures: Each method for measuring GFR was performed twice in 7 cats at 24-day intervals. The Wilcoxon signed-rank sum test was used to compare the results obtained from the 14 studies for each method. Results from the 4 methods were assessed for agreement and correlation., Results: The median GFR values were 2.75, 2.83, 3.14, and 4.26 mL/min/kg, for Tk-GV, CT-Pp, plasma CrCL, and GTS, respectively. Analysis with Wilcoxon signed-rank sum tests identified significant pairwise differences between results obtained with the Tk-GV versus the plasma CrCL method, the Tk-GV versus the GTS method, and the plasma CrCL versus the GTS method. The least variable method was Tk-GV, with an SD of 1.27 (mL/min/kg)., Conclusions and Clinical Relevance: Findings indicated that Tk-GV yielded GFR measurements comparable with those obtained with CT-Pp, plasma CrCL, and GTS; however, the Tk-GV method yielded the tightest range of results among the methods evaluated.

Impinging processi spinosi in the equine thoracic spine are a common cause of poor performance in the horse. A modified semiquantitative scintigraphic image analysis has been proposed for the evaluation of equine processi spinosi. This technique showed a high inter- and intraobserver agreement when compared to subjective and semiquantitative image analysis. The aim of this retrospective, method comparison study was to evaluate the agreement of the modified semiquantitative scintigraphic image assessment with previous methods of interpretation and to compare these scintigraphic evaluation techniques with radiographic and clinical findings. Two hundred twenty-three Warmblood horses that underwent scintigraphic, radiographic, and clinical examination of the thoracic spine were included in the study. Scintigraphic images were assessed using subjective, semiquantitative, and modified semiquantitative techniques. Radiographs were subjectively graded and horses were assigned to a group with or without thoracolumbar pain. Total radiographic and total scintigraphic grades were higher in horses with thoracolumbar pain (P < 0.05). Both the semiquantitative and the modified semiquantitative uptake ratios did not differ significantly in horses with or without thoracolumbar pain. The kappa agreement showed a substantial agreement between the modified semiquantitative scintigraphic and the semiquantitative scintigraphic evaluation techniques. The agreement between subjective scintigraphic and modified semiquantitative scintigraphic image evaluations was fair. There was a slight agreement between all scintigraphic techniques and radiographic findings. Limitations were the definition of thoracolumbar pain and the image analysis being restricted to the caudal thoracic processi spinosi. In conclusion, the modified semiquantitative scintigraphic image assessment obtained consistent results but did not perform better than previous evaluation methods. Further comparison to a defined diagnosis is warranted., (© 2018 American College of Veterinary Radiology.)

Background: Naturally occurring hypothyroidism in adult cats is rare, with only 4 cases reported., Objectives: To describe the historical, clinical, laboratory, and scintigraphic features of adult cats with spontaneous hypothyroidism., Animals: Seven adult cats referred for suspected hypothyroidism., Methods: Prospective case series. We collected data on cats' signalment, clinical signs, results of physical examination, routine laboratory and thyroid hormone testing, and thyroid imaging (thyroid scintigraphy or ultrasound). We subsequently treated cats with levothyroxine and evaluated their response to treatment., Results: Cats ranged from 3.5 to 11 years, with no apparent breed predilection; 6/7 cats were male. Only 2/7 cats were initially tested because of signs of hypothyroidism (hair-coat changes, lethargy, obesity); others were tested for routine thyroid monitoring or palpable thyroid nodules. Four were azotemic (serum creatinine, 2.2-3.4 mg/dL). Six of the cats had low serum thyroxine (T 4 ) and free T 4 (fT 4 ) concentrations, whereas all 7 cats had high thyroid-stimulating hormone (TSH) concentrations. In 6/7 cats, thyroid scintigraphy revealed bilateral goiter with intense radionuclide uptake; imaging showed no visible thyroid tissue in the other. After levothyroxine treatment, serum concentrations of T 4 and fT 4 increased and TSH fell; high serum creatinine normalized in azotemic cats; and repeat imaging showed reduction in goiter size., Conclusions and Clinical Importance: Primary hypothyroidism develops in adult cats, with a higher prevalence than previously thought. Most cats appear to develop a goitrous form of hypothyroidism associated with thyroid hyperplasia, whereas thyroid atrophy appears to be less common. With levothyroxine replacement, clinical and laboratory abnormalities improve or resolve., (© 2018 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

This article discusses the basis of image formation of radiography, scintigraphy, PET, computed tomography (fan beam and cone beam), and magnetic resonance as it relates to imaging of musculoskeletal injury in the sport horse. The benefits and drawbacks of each modality are discussed with particular emphasis on sensitivity, specificity, and accuracy of identification of subchondral bone injury. Examples of straightforward as well as confounding lesions are provided, emphasizing the need for appropriate clinical workup and diagnostic analgesia, where appropriate., (Copyright © 2018 Elsevier Inc. All rights reserved.)

There is good correlation between increased radiopharmaceutical uptake anywhere in the feet of sports or leisure horses and the presence of foot pain. However, low sensitivity of scintigraphy for identifying lesions contributing to foot pain as determined by magnetic resonance imaging (MRI) has been reported. The aim of this retrospective, cross-sectional, analytical study was to assess the accuracy of scintigraphy for identifying the cause(s) of foot pain, using MRI as the reference standard. Sports and leisure horses that underwent both skeletal scintigraphy and MRI of the front feet between March 2008 and December 2014 and for which a definitive diagnosis of the cause(s) of front foot pain was reached were included (121 feet of 70 horses). Imaging studies were evaluated retrospectively, blindly. Agreements between scintigraphic localization of increased radiopharmaceutical uptake and subjective categorization of lesions with MRI diagnosis were assessed using Kappa statistics (κ). Measures of diagnostic accuracy were calculated. Sensitivity of increased radiopharmaceutical uptake varied among regions (31.8-76.2%) but specificity was at least high for all (84.6-100%). Agreements between both scintigraphy measures and MRI diagnosis were substantial for the distal phalanx (palmar processes and body) (κ = 0.77 and κ = 0.74, respectively), and ungular cartilages and chondral ligaments (κ = 0.62, for both). When all regions were combined, agreements of increased radiopharmaceutical uptake (κ = 0.49) and relevance categorization (κ = 0.45) with MRI diagnosis were moderate. In conclusion, skeletal scintigraphy does not meet the minimum reliability level for a diagnostic test, but is reliable for identification of osseous trauma to the distal phalanx and ungular cartilages., (© 2018 American College of Veterinary Radiology.)

Scintigraphy is a standard diagnostic method for evaluating horses with back pain due to suspected thoracic processus spinosus pathology. Lesion detection is based on subjective or semi-quantitative assessments of increased uptake. This retrospective, analytical study is aimed to compare semi-quantitative and subjective methods in the evaluation of scintigraphic images of the processi spinosi in the equine thoracic spine. Scintigraphic images of 20 Warmblood horses, presented for assessment of orthopedic conditions between 2014 and 2016, were included in the study. Randomized, blinded image evaluation was performed by 11 veterinarians using subjective and semi-quantitative methods. Subjective grading was performed for the analysis of red-green-blue and grayscale scintigraphic images, which were presented in full-size or as masked images. For the semi-quantitative assessment, observers placed regions of interest over each processus spinosus. The uptake ratio of each processus spinosus in comparison to a reference region of interest was determined. Subsequently, a modified semi-quantitative calculation was developed whereby only the highest counts-per-pixel for a specified number of pixels was processed. Inter- and intraobserver agreement was calculated using intraclass correlation coefficients. Inter- and intraobserver intraclass correlation coefficients were 41.65% and 71.39%, respectively, for the subjective image assessment. Additionally, a correlation between intraobserver agreement, experience, and grayscale images was identified. The inter- and intraobserver agreement was significantly increased when using semi-quantitative analysis (97.35% and 98.36%, respectively) or the modified semi-quantitative calculation (98.61% and 98.82%, respectively). The proposed modified semi-quantitative technique showed a higher inter- and intraobserver agreement when compared to other methods, which makes it a useful tool for the analysis of scintigraphic images. The association of the findings from this study with clinical and radiological examinations requires further investigation., (© 2018 American College of Veterinary Radiology.)

Skeletal scintigraphy is an established imaging modality, however, its validity as a diagnostic test in lame or poorly performing sports horses has not been determined. The objective of this retrospective cross-sectional analytical study was to determine the accuracy of skeletal scintigraphy as an indiscriminate screening test in sports horses. All sports horses that underwent scintigraphic examination between March 2008 and December 2014 for which a definitive diagnosis was reached were included. Examinations were evaluated blindly. Characteristics of increased radiopharmaceutical uptake were recorded and subjectively categorized as possibly relevant or non-relevant. Kappa statistics were used to assess agreement between test results and final diagnosis. There were 1222 positive clinical diagnoses in 480 horses, of which 687 regions (56.4%) had no associated increased radiopharmaceutical uptake and 99 regions (8.1%) had non-relevant increased radiopharmaceutical uptake. The sensitivity of increased radiopharmaceutical uptake for identification of final diagnosis was low (43.8%) and specificity was high (94.0%). The agreement was fair (κ = 0.36). Relevance categorization improved the test; the sensitivity for final diagnosis was low (35.7%), specificity was high (98.9%), and the agreement was moderate (κ = 0.45). The agreements of increased radiopharmaceutical uptake and relevance categorization with final diagnosis were only substantial for feet (κ = 0.67 and κ = 0.66, respectively) and proximal aspect of the forelimb (elbow, shoulder, and scapula combined) (κ = 0.69 and 0.78, respectively). Scintigraphic examination is unlikely to lead to a full and correct diagnosis of the cause(s) of lameness or poor performance in sports horses when used as an isolated or indiscriminate screening tool., (© 2018 American College of Veterinary Radiology.)

Background: A low plasma total thyroxine (TT 4 ) concentration in combination with a plasma TSH concentration within reference range does not distinguish between hypothyroidism and nonthyroidal illness (NTI) in dogs. Hypothyroidism is associated with TSH-releasing hormone (TRH)-induced increased release of growth hormone (GH)., Hypothesis: Basal and TRH-induced plasma GH concentrations can be used to distinguish hypothyroid dogs from NTI dogs., Animals: Twenty-one dogs with signs consistent with hypothyroidism, a low plasma TT 4 concentration, and a plasma TSH concentration within reference interval., Methods: Case control study. Thyroid scintigraphy was performed to classify dogs as having hypothyroidism or NTI. All dogs underwent a TRH stimulation test with measurement of plasma concentrations of GH and TSH before and 30 and 45 minutes after IV administration of TRH., Results: Eleven of the dogs were classified as hypothyroid and 10 as having NTI. Basal plasma GH concentration in the hypothyroid dogs (3.2 μg/l; range, 2.0 to 12.5 μg/l) was significantly higher (p<0.001) than that in the NTI dogs (.73 μg/l; range, .45 to 2.3 μg/l), with minimal overlap, and increased (p=.009) after TRH administration in hypothyroid dogs, whereas it did not change in NTI dogs. At T=45, plasma GH concentrations in hypothyroid dogs and NTI dogs did not overlap. The plasma TSH concentration did not change significantly after TRH administration in hypothyroid dogs, whereas it increased (p<.001) in NTI dogs. At T=45, there was no overlap in percentage TSH increase from baseline between hypothyroid dogs., Conclusions and Clinical Importance: Measurement of basal plasma GH concentration and concentrations of GH and TSH after TRH stimulation can distinguish between hypothyroidism and NTI in dogs., (Copyright © 2018 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Objectives The outcome of radioiodine therapy in hyperthyroid cats is suspected to be influenced by multiple factors. The degree of activity of the thyroid gland, represented by uptake of sodium pertechnetate or tracer activities of radioiodine by the thyroid gland on thyroid scintigraphy, has been suggested in the literature as one of those. Thyroid gland pertechnetate uptake can be represented by (semi-)quantitative factors such as the thyroid to salivary gland (T/S) ratio, the thyroid to background (T/B) ratio and the percentage technetium uptake by the thyroid glands (%TcU). The aim of this study was to investigate a possible relationship between these thyroid scan parameters and radioiodine therapy outcome. Methods Sodium pertechnetate thyroid scans of 75 hyperthyroid cats were retrospectively evaluated and statistical analysis was performed with and without correction for injected radioiodine activity. Three different background regions of interest (ROIs) were used to calculate the T/B ratio and %TcU: 'neck', 'circle' and 'copy ROI'. Results Higher T/S ratios were found to be significantly related to a persistent hyperthyroid outcome in both analyses. For the T/S ratio, a threshold value of 5.4 was determined, with a sensitivity of 73% and a specificity of 59%. An increased risk for persistent hyperthyroidism compared with a final euthyroid outcome with an increased T/B circle ratio was only found to be significant without correction for the activity of radioiodine administered. For the %TcU no statistical significance was reached. Regarding a low total thyroxine outcome, no significant relationships with any of the investigated parameters were found. Conclusions and relevance The findings of this study suggest that semi-quantification of thyroid gland uptake is best performed using the T/S ratio. A T/S ratio ⩾5.4 is a possible indicator for an increased risk of persistent hyperthyroidism.

Objectives The study aims were to evaluate the feasibility of contrast-enhanced ultrasonography in feline renal transplant recipients in the post-transplantation period and to report findings in a case with presumptive delayed allograft ischemia. Methods Cats were imaged postoperatively using contrast harmonic ultrasonography after a bolus injection of a microbubble contrast medium. Time/mean pixel intensity curves were generated for cortical and medullary regions of interest in the renal allograft in each cat. Arrival time, time to peak, wash-in slope, wash-out slope, mean transit time and renal blood flow were calculated for each area. Results Within the renal cortices of cats without ureteral obstruction 1 day post-transplantation, arrival time was 2.0-6.3 s, time to peak was 3.6-30.1 s, wash-in rate was 2.45-41.14 mean pixel intensity (MPI)/s, wash-out rate was -2.01 to -0.47 MPI/s and blood flow was 6.1-106.5 MPI/s. Ratio mean transit time was 0.29-1.29. Typical cortical and medullary perfusion patterns were observed in these cats. In one cat with delayed graft ischemia followed by presumptive acute transplant rejection, dynamic and heterogeneous cortical and medullary perfusion was demonstrated. Decreases in cortical blood flow were paralleled by elevated serum creatinine. Conclusions and relevance Contrast-enhanced ultrasonography can be used in feline renal transplant recipients and provides both qualitative and quantitative data regarding renal allograft perfusion.

Although scintigraphy is an important tool for the assessment of thyroid function in cats, time variation of commonly used thyroid variables has not been investigated to this day. The aim of this study was to investigate whether a week-to-week variation of scintigraphic variables exists in healthy cats of a magnitude that is clinically relevant, as this could lead to misinterpretation of results. Fourteen adult, healthy, experimental cats were included in the study. At 3 time points, with 7-day intervals, the cats underwent a thyroid pertechnetate scan and blood samples were collected. The scintigraphic variables calculated were the thyroid to salivary gland ratio (T/S), thyroid to background ratio (T/B), percentage technetium uptake in the thyroid glands (%TcU T ) and additionally percentage technetium uptake in the salivary glands (%TcU SG ). Two thyroid hormones, total thyroxine (TT 4 ) and thyroid stimulating hormone (TSH), were included in the analysis. All scintigraphic variables, with the exception of the %TcU T and T/B neck ratio, were within the normal reference ranges reported in literature. No clinically relevant week-to-week variation was observed for any of the variables included in this study., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: Aerosolized medications are increasingly being used to treat respiratory diseases in dogs. No previous studies assessing respiratory tract deposition of radiolabeled aerosols have been performed in conscious dogs., Hypothesis/objectives: Assess respiratory tract deposition of radiolabeled, inhalant corticosteroid (fluticasone propionate labeled with 99m Tc) delivered from a nebulizer and metered dose inhaler (MDI) to healthy dogs., Animals: Ten healthy Foxhounds., Methods: Prospective, randomized, cross-over pilot study. Initial inhalation method (nebulizer or MDI) was randomly assigned. Treatments were crossed over after a 7-day washout period. Treatments initially were performed using sedation. Dogs were imaged using 2-dimensional planar scintigraphy, with respiratory tract deposition quantified by manual region-of-interest analysis. Deposition calculated as percentage of delivered dose. Six of 10 dogs were randomly selected and reassessed without sedation., Results: Inhalation method had significant effect on respiratory tract deposition (P = 0.027). Higher deposition was achieved by nebulization with mean deposition of 4.2% (standard deviation [SD], 1.4%; range, 1.9-6.1%); whereas MDI treatment achieved a mean of 2.3% (SD, 1.4%; range, 0.2-4.2%). Nebulization achieved higher respiratory tract deposition than MDI in 7 of 10 dogs. No statistical difference (P = 0.68) was found between mean respiratory tract deposition achieved in dogs when unsedated (3.8%; SD, 1.5%) or sedated (3.6%; SD, 1.7%)., Conclusions and Clinical Importance: Study confirms respiratory tract deposition of inhalant medications delivered from a nebulizer and MDI in healthy dogs, breathing tidally with and without sedation. Respiratory tract deposition in these dogs was low compared to reported deposition in adult humans, but similar to reported deposition in children., (Copyright © 2017 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Background: Thyroid cysts are rare in cats and poorly documented., Objectives: To report distinguishing clinical features and treatment responses of cats with thyroid cysts., Animals: Forty client-owned cats., Methods: Retrospective review of medical records for cats with thyroid cysts confirmed by scintigraphy, ultrasound, magnetic resonance imaging, or necropsy at 4 referral centers between 2005 and 2016. Signalment, clinical findings, diagnostic testing, treatment, and outcome were recorded., Results: Cats ranged in age from 8 to 20 years with no apparent breed or sex predilection. 37 of 40 (93%) cats were hyperthyroid (duration, 1-96 months). Clinical findings included palpable neck mass (40/40, 100%), weight loss (15/40, 38%), dysphagia (8/40, 20%), decreased appetite (5/40, 13%), and dyspnea (4/40, 10%). Cysts were classified as small (≤8 cm 3 ) in 16 (40%) and large (>8 cm 3 ) in 24 (60%) cats. Of 25 cats treated with radioiodine, hyperthyroidism resolved in 23 (92%), whereas thyroid cysts resolved in 12 (50%). Radioiodine treatment resolved small cysts in 8 of 13 (62%) cats and large cysts in 4 of 11 (36%) cats. Eight cats, including 2 euthyroid cats, underwent thyroid-cystectomy; 3 with bilateral thyroid involvement were euthanized postoperatively for hypocalcemia. Excised cystic thyroid masses were identified as cystadenoma (4) and carcinoma (4)., Conclusions and Clinical Importance: Thyroid cysts are encountered in hyperthyroid and euthyroid cats with benign and malignant thyroid tumors. Radioiodine treatment alone inconsistently resolved thyroid cysts. Thyroid-cystectomy could be considered in cats with unilateral thyroid disease or when symptomatic cysts persist despite successful radioiodine treatment of hyperthyroidism., (Copyright © 2017 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Background: The prevalence of gastric emptying (GE) disorders in cats is unknown due to lack of clinically applicable diagnostic tests., Objectives: The principal aim of this study was to assess correlation between scintigraphic and ultrasonographic measurements of GE time (GET) in healthy cats. Additionally, variability of ultrasonographic GET, and correlation between scintigraphy and ultrasonographic parameters of gastric motility were evaluated., Animals: Eight healthy domestic shorthair cats., Methods: Prospective study. Scintigraphic GET was determined using a solid test meal containing 4 mCi 99m Tc-mebrofenin. Each cat had 3 separate ultrasonographic assessments of GE, performed independent of scintigraphic assessment, after solid test meal consumption. The motility index (MI) of antral contractions was plotted against time and time for each fraction of the area under the MI curve determined. Ultrasonographic GET and MI were correlated to scintigraphic GET., Results: Scintigraphic GET (mean ± SD) for 25, 50, and 75% GE was 103 ± 32 minutes, 196 ± 45 minutes, and 288 ± 62 minutes, whereas sonographic GET for 25, 50, and 75% GE was 106 ± 13 minutes, 203 ± 19 minutes, and 305 ± 27 minutes. There was good correlation between scintigraphic and sonographic GET (r = 0.72-0.82) at 45-90% fractional GE and between scintigraphic GET and time of corresponding MI curve fraction (r = 0.78-0.86) at 40-90% fraction of the MI curve. There was moderate intraindividual variability for sonographic GET and MI curve fraction times as well as significant variation among individuals., Conclusions and Clinical Importance: Ultrasonography is a valid alternative to scintigraphy for assessment of solid-phase GE and allows assessment of postprandial gastric motility in healthy cats., (Copyright © 2017 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

CASE DESCRIPTION An 8-year-old Brahman-cross bull was evaluated for left hind limb lameness of 2 months' duration. The lameness was first noticed during a rodeo bucking performance, immediately after the bull appeared to land inappropriately on the affected limb. CLINICAL FINDINGS Physical examination findings revealed left hind limb lameness, ataxia, and left-sided epaxial muscle atrophy. Palpation per rectum along the lumbar portion of the vertebral column revealed evidence of exostosis of the ventral aspect. High-definition infrared thermal imaging revealed a pattern of reduced skin temperature in the area of the left lumbar and gluteal regions suggestive of a disruption in the sympathetic control of peripheral blood flow. Nuclear scintigraphy revealed a focal area of increased radioisotope uptake on the left ventrolateral aspect of the L2-3 intervertebral joint. A presumptive diagnosis of ventrolateral vertebral spondylosis resulting in spinal nerve impingement was made. TREATMENT AND OUTCOME 200 mg of methylprednisolone was epidurally injected at the site of the lesion, and treatment with polysulfated glycosaminoglycans was initiated (500 mg, IM, every 4 days for 7 treatments, then monthly thereafter). The lameness and ataxia observed in the left hind limb resolved within 1 week after treatment began. Subsequently, the bull was discharged from the hospital and was used successfully for semen collection and live-cover breeding. CLINICAL RELEVANCE Use of thermography for the bull of this report provided additional insight into neurovascular physiologic function that classical imaging modalities are unable to provide and, when combined with nuclear scintigraphy, aided in identifying the most critical lesion in a complex clinical case.

Background: Diagnosis of protein loss into the gastrointestinal tract using noninvasive techniques is challenging. In people, scintigraphy not only is a sensitive tool to confirm protein-losing enteropathy (PLE), but it also allows for localization of protein loss., Hypothesis/objectives: To investigate the feasibility of 99m Tc-labeled human serum albumin (HSA) scintigraphy in dogs with PLE in comparison with control dogs., Animals: A total of 8 clinically healthy control research dogs and 7 client-owned dogs with gastrointestinal clinical signs and hypoalbuminemia (serum albumin concentration <2.0 g/dL)., Methods: Prospective case-control study. After IV injection of 400 MBq freshly prepared 99m Tc HSA (30 mg/dog), images of the abdomen were obtained 10, 60, 120, and 240 minutes postinjection. Additional images of the salivary and thyroid glands were obtained to rule out free 99m Tc. A scan was considered positive for PLE when radiopharmaceutical exudation was detectable in the intestinal tract., Results: Only 1 control dog showed exudation of the radiopharmaceutical into the intestinal tract. No free 99m Tc was detected in any dog. In dogs with PLE, focal small intestinal and diffuse small intestinal radiopharmaceutical exudation into the bowel was detected in 2 and 3 dogs, respectively, whereas in 2 dogs, there was disagreement about whether radiopharmaceutical exudation was focal or diffuse., Conclusion and Clinical Importance: 99m Tc-labeled HSA scintigraphy was feasible to diagnose PLE in dogs., (Copyright © 2017 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Objective: To assess the feasibility of intra-arterial administration of allogeneic mesenchymal stem cells (MSC) in the median artery of standing horses and evaluate the distribution and retention of radiolabeled cells., Study Design: In vivo experimental study., Animals: Six research horses., Methods: Technetium(99m) -HexaMethyl-Propylene-Amine Oxime-labeled MSC were injected under ultrasound guidance in the median artery of 6 front limbs of 3 horses, standing under sedation. Scintigraphic images were obtained at the time of injection, and at 1, 6, and 24 hours postinjection. Six additional limbs from 3 horses were similarly injected with unlabeled MSC. Ultrasound was performed the following day for assessment of vascular changes., Results: Intra-arterial injection was performed successfully in 11 of 12 limbs. In 1 limb, partial periarterial injection compromised the success of the procedure. Homogeneous distribution of radiolabeled MSC was observed through the entire distal limb, including within the hoof. Partial venous thrombosis was found in both groups of horses, but was subjectively less severe in horses injected with unlabeled MSC. No lameness was observed. Transient swelling of the distal limb occurred in only 1 limb., Conclusion: Intra-arterial injection of MSC can be performed in standing horses under sedation and successfully distribute MSC to the distal limb. A risk of periarterial injection was identified but can be reduced with proper sedation, local anesthesia, and increased experience. Partial venous thrombosis was observed as a complication, but did not cause changes of clinical importance, other than rare transient swelling., (© Copyright 2016 by The American College of Veterinary Surgeons.)

Thyroid scintigraphy is commonly used for evaluation of cats with hyperthyroidism, with the thyroid-to-salivary ratio (T/S) being the most common method to quantify the degree of thyroid activity and disease. Calculation of thyroid-to-background ratios (T/B) or percent thyroidal uptake of (99m) TcO(-) 4 (TcTU) has only been reported in a few studies. The purpose of this prospective, cross-sectional study was to evaluate a number of quantitative scintigraphic indices as diagnostic tests for hyperthyroidism, including the T/S, three different T/B, TcTU, and estimated thyroid volume. Of 524 cats referred to our clinic for evaluation of suspected hyperthyroidism, the diagnosis was confirmed (n = 504) or excluded (n = 20) based on results of a serum thyroid panel consisting of thyroxine (T4 ), triiodothyronine (T3 ), free T4 (fT4 ), and thyroid-stimulating hormone (TSH) concentrations. In the hyperthyroid cats, median values for TcTU, T/S, and three T/B ratios were all significantly higher (P < 0.001) than values in euthyroid suspect cats or clinically normal cats. All scintigraphic parameters were relatively sensitive and specific as diagnostic tests for hyperthyroidism, but the T/S ratio had the highest test accuracy. The T/S ratio correlated strongly with the TcTU (r = 0.85). However, the TcTU had a higher and more significant correlation (P < 0.01) with serum T4 (r = 0.76 vs. 0.64), T3 (r = 0.77 vs. 0.64), and estimated thyroid volume (r = 0.62 vs. 0.38). Overall, calculation of TcTU is an accurate diagnostic test, but also appears to be the best parameter to predict the functional volume and metabolic activity of the feline adenomatous thyroid gland., (© 2016 American College of Veterinary Radiology.)

Thyroid-to-salivary ratio and percent dose uptake are the most widely recognized scintigraphic measurements. Recently, the thyroid-to-background ratio has been proposed as an alternate method. However, this method has not been validated. The purpose of this observational, cross-sectional, prospective study was to determine the location of a background region of interest (ROI) that is most reflective of blood pool activity. We also hypothesized that the thyroid-to-background ratio using this background ROI would be a better predictor of thyroid function. Fifty-six cats presented to the Virginia-Maryland College of Veterinary Medicine seeking radioiodine therapy for hyperthyroidism were enrolled in this cross-sectional study to evaluating thyroid-to-background ratio. A blood sample for measuring plasma radioactivity was collected at the time of scintigraphy. The plasma radioactivity was compared to the background ROIs in eight anatomic regions. Scintigraphic measures of thyroid-to-background and thyroid-to-salivary ratios, and percent dose were then compared to serum T4 . The heart ROI was most closely correlated with plasma pertechnetate activity (r = 0.70). Percent dose uptake was most closely correlated with serum T4 (r = 0.74), followed by thyroid-to-salivary ratio (r = 0.66) and thyroid-to-background ratio using the heart ROI (r = 0.59). Thyroid-to-background ratio using the heart background ROI is a good predictor T4 but percent dose uptake and thyroid-to-salivary ratio proved to be better predictors of T4 than any of the thyroid-to-background ratios., (© 2016 American College of Veterinary Radiology.)

The aim of this study was to assess inter- and intraobserver variability of commonly used semi-quantitative and quantitative parameters in feline thyroid scintigraphy: thyroid to salivary gland ratio (T/S), thyroid to background ratio (T/B) and the percentage technetium pertechnetate uptake for the thyroid glands (%TcUT). These parameters are being used to diagnose thyroid disease and to assess its severity, but may be influenced by operator related factors when processing the images. Additionally, inter- and intraobserver variability of the percentage technetium pertechnetate uptake for the salivary glands was determined (%TcUSG). The study included technetium pertechnetate scans of 100 hyperthyroid cats. Variability within and between three observers was determined using a random effects model and variance components were estimated by the restricted maximum likelihood procedure. The %TcU for the thyroid and salivary glands, as well as the T/S ratio, showed little to no difference in inter- and intraobserver variability, whereas this was clearly present for the T/B ratio. Overall, the T/S ratio and %TcUSG showed a good repeatability and reproducibility with low inter- and intraobserver variabilities. Inter- and intraobserver variability was higher for the %TcUT, however variations were still considered to be acceptable. On the contrary, inter- and intraobserver variability was clearly larger for the T/B ratio. These findings suggest the preferential use of the T/S ratio or %TcU, especially in facilities with a less experienced staff., (Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.)

Recent advances in the application of bone marrow mesenchymal stem cells (BMMSC) for the treatment of tendon and ligament injuries in the horse suggest improved outcome measures in both experimental and clinical studies. Although the BMMSC are implanted into the tendon lesion in large numbers (usually 10 - 20 million cells), only a relatively small number survive (<10%) although these can persist for up to 5 months after implantation. This appears to be a common observation in other species where BMMSC have been implanted into other tissues and it is important to understand when this loss occurs, how many survive the initial implantation process and whether the cells are cleared into other organs. Tracking the fate of the cells can be achieved by radiolabeling the BMMSC prior to implantation which allows non-invasive in vivo imaging of cell location and quantification of cell numbers. This protocol describes a cell labeling procedure that uses Technetium-99m (Tc-99m), and tracking of these cells following implantation into injured flexor tendons in horses. Tc-99m is a short-lived (t1/2 of 6.01 hr) isotope that emits gamma rays and can be internalized by cells in the presence of the lipophilic compound hexamethylpropyleneamine oxime (HMPAO). These properties make it ideal for use in nuclear medicine clinics for the diagnosis of many different diseases. The fate of the labeled cells can be followed in the short term (up to 36 hr) by gamma scintigraphy to quantify both the number of cells retained in the lesion and distribution of the cells into lungs, thyroid and other organs. This technique is adapted from the labeling of blood leukocytes and could be utilized to image implanted BMMSC in other organs.

Injuries involving the femoral third trochanter are an uncommon but important source of equine lameness; however, clinical localization can be challenging. The purpose of this retrospective study was to describe ultrasonographic and scintigraphic findings in a group of horses with presumed third trochanter injury. Medical records of an equine referral hospital were searched from 2004-2014, and 20 horses met the inclusion criteria. Lesions consistent with third trochanter fracture were identified with ultrasound in 14/20 horses. Onset of lameness was acute (11), insidious (2), or unknown (1). All but one horse was lame at presentation, ranging from Grade 2-4/5. Ultrasound was the primary diagnostic modality in 5/14 horses with fragmentation, while scintigraphic findings of intense (3), moderate (5), and mild (1) increased radiopharmaceutical uptake (IRU) prompted ultrasonographic examinations in 9/14 fractured horses. A nondisplaced fracture was suspected in an additional horse with intense IRU and negative ultrasound findings. In the remaining five horses, imaging findings included only mild IRU. Lameness was localized to other regions in these cases. Six of 12 fractured horses with available outcome data were returned to function after a prolonged rehabilitation of 8-18 months. Scintigraphic findings helped to direct focused ultrasound exams in the majority of fracture cases. Horses with evidence of third trochanter fracture had similar clinical characteristics to that reported for pelvic fractures and authors therefore recommend ultrasonographic examination of both regions, especially when scintigraphy is unavailable. Prognosis for return to function in horses of the current study was less favorable than previously reported., (© 2015 American College of Veterinary Radiology.)

Reasons for Performing Study: There is limited information regarding the impact of training track surface on the occurrence of stress fractures., Objectives: To evaluate the impact of training track surface on the proportion of long bone and pelvic stress fractures associated with lameness in Thoroughbred horses in flat race training undergoing nuclear scintigraphic examination., Study Design: Retrospective study., Methods: Scintigraphic examinations of Thoroughbred flat racehorses were evaluated from 2 hospitals (hospital A [Toronto Equine Hospital], 2003-2009, and hospital B [George D. Widener Hospital for Large Animals, School of Veterinary Medicine, University of Pennsylvania], 1994-2006). Horses admitted to hospital A trained at a single track, at which the main training surface changed from dirt to synthetic on 27 August 2006. Two distinct populations existed at hospital B: horses that trained on dirt (numerous trainers) and those that trained on turf (single trainer). All scintigraphic images were evaluated by a blinded reviewer. Fisher's exact test and logistic regression were used when appropriate, and significance was set at P<0.05., Results: When reviewing 528 scintigraphic examinations from hospital A (257 dirt and 271 synthetic, numerous trainers), there was a greater proportion of stress fractures detected in scintigraphic examinations from horses training on a synthetic surface (31.7%) in comparison to scintigraphic examinations from horses training on a dirt surface (23.0%) at an earlier point in time (P = 0.03). There was a greater proportion of hindlimb/pelvic and tibial stress fractures diagnosed in horses from the synthetic surface-trained group than from the dirt-trained group at hospital A (P<0.04 and P = 0.03, respectively)., Conclusions: This study provides evidence that training surface may affect the proportion of stress fractures diagnosed, but other factors, such as training philosophy, appear to be important. Future prospective investigations to fully elucidate the relationship between training track surface and the proportion of stress fractures and other nonfatal musculoskeletal injuries are warranted., (© 2014 EVJ Ltd.)

Objective: To assess distribution, uptake, and persistence of radiolabeled mesenchymal stem cells (MSC) using scintigraphy after intravenous regional limb perfusion (RLP) and subcutaneous injections in standing, sedated horses., Study Design: Experimental study., Animals: Horses (n = 12)., Methods: Six horses had RLP performed through the cephalic vein on 1 limb and subcutaneous injection in the metacarpal area in the opposite limb. The other 6 horses had RLP performed through the lateral palmar digital vein and subcutaneous injection in the coronary band. A pneumatic tourniquet was used for the RLP. MSC were labeled with technetium-HMPAO. Scintigraphic images were obtained at the time of injection, 1, 6, and 24 hours later. Results of RLP were compared with results from previous studies where similar injections were performed in anesthetized horses., Results: Both RLP techniques led to greater variability, lower uptake, lower persistence, and poorer distribution when compared to results previously reported for horses under general anesthesia. The subcutaneous injections in the metacarpal area and coronary band resulted in MSC loss to the general circulation but no evidence of local migration., Conclusion: Due to partial or complete failure of the tourniquet, RLP performed in the standing horse as described is less efficient than performed under general anesthesia. Further work is needed to optimize the use of tourniquets to perform RLP for MSC administration in standing patients. The subcutaneous injections did not result in local migration in these normal horses., (© Copyright 2014 by The American College of Veterinary Surgeons.)

The current standard scintigraphic method for estimating glomerular filtration rate (GFR) in dogs is the integral method, which normalizes renal GFR to body weight. The plasma volume method, that is normalizing GFR to plasma volume, has been reported to be more physiologically correct. The aim of this prospective study was to test the effect of hydration status on GFR measured by these two methods in a group of dogs with suspected renal disease. Eleven dogs were recruited. All dogs underwent standardized scintigraphic examinations before and after 15 ml/kg of fluid was administered intravenously at 5-7 ml/kg/min. Individual kidney GFR estimates (n = 22) were calculated using both methods and a consensus of two observers who were unaware of clinical findings. Individual kidney GFR increased significantly (P = 0.0008) after fluid administration using the integral method and individual kidney GFR using the plasma volume method remained constant. Percentage differences for individual kidney GFR before and after fluid administration were 31.4 ± 58.1% (change ± 95% CI) for the integral method and 0.1 ± 70% (change ± 95% CI) for the plasma volume method. Intravenously administered fluid increased individual kidney GFR from low to normal in 10 of 22 kidneys using the integral method and in 1 of 22 kidneys using the plasma volume method. Findings supported the use of the plasma volume method for scintigraphic calculation of GFR in dogs with suspected renal disease and indicated that errors of kidney status classification may more likely occur when the integral method is used., (© 2014 American College of Veterinary Radiology.)

Objective: To evaluate the relationship between hepatic steatosis and increase in liver size and resolution of shunting after surgical attenuation of congenital extrahepatic portosystemic shunts in dogs., Study Design: Prospective study., Animals: Dogs (n = 20) with congenital extrahepatic portosystemic shunts., Methods: Shunts were attenuated using ameroid ring constrictors. Portal blood flow and liver volume were evaluated using computed tomography before and ≥8 weeks after surgery. Hepatic steatosis was quantified by stereological point counting of lipid droplets and lipogranulomas (LG) in liver biopsies stained with Oil-red-O. Associations between steatosis and preoperative liver volume, liver growth after surgery, and development of acquired shunts were evaluated., Results: Acquired shunts developed in 2 dogs (10%). Dogs with larger preoperative liver volumes relative to bodyweight had fewer lipid droplets per tissue point (P = .019). LG per tissue point were significantly associated with age: 0.019 ± 0.06 for dogs <12 months versus 0.25 ± 0.49 for dogs >12 months (P = .007). There was a significant positive association between liver growth after surgery and the number of LG/month of age in dogs >12 months (P = .003). There was no association between steatosis, presence of macrosteatosis, the number of LG or development of acquired shunts., Conclusions: This preliminary study suggests that the presence of hepatic lipidosis and LG has no demonstrable effect on development of acquired shunts or the magnitude of increase in liver volume after attenuation of congenital extrahepatic portosystemic shunts in dogs., (© Copyright 2014 by The American College of Veterinary Surgeons.)

Reasons for Performing Study: Intra-arterial (i.a.) and intravenous (i.v.) regional limb perfusions (RLP) through the median artery and cephalic vein, respectively, have been previously investigated for administration of mesenchymal stem cells (MSCs) to the equine distal limb. Limitations due to thrombosis of the arteries after i.a. RLP and poor distribution of MSCs to the foot with i.v. RLP were observed. These techniques need to be modified for clinical use., Objectives: Evaluate the distribution, uptake and persistence of radiolabelled MSCs after i.a. injection through the median artery without a tourniquet and after i.v. RLP through the lateral palmar digital vein., Study Design: In vivo experimental study., Methods: (99m) Tc-HMPAO-labelled MSCs were injected through the median artery of one limb and the lateral palmar digital vein of the other limb of 6 horses under general anaesthesia. No tourniquet was used for the i.a. injection. A pneumatic tourniquet was placed on the metacarpus for i.v. injection. Scintigraphic images were obtained up to 24 h after injection., Results: Intra-arterial injection resulted in MSCs retention within the limb despite the absence of a tourniquet and no thrombosis was observed. Both i.a. injection and i.v. RLP led to distribution of MSCs to the foot. The i.a. injection resulted in a more homogeneous distribution. The MSC uptake was higher with i.v. RLP at the initial timepoints, but no significant difference was present at 24 h., Conclusions: Both i.a. injection through the median artery without a tourniquet and i.v. RLP performed through the lateral palmar digital vein under general anaesthesia are safe and reliable methods for administration of MSCs to the equine foot. The i.a. technique is preferred owing to the better distribution, but is technically more challenging. The feasibility of performing these techniques on standing horses remains to be investigated., (© 2013 EVJ Ltd.)

Objective: To directly compare solid-phase gastric emptying times assessed by means of a [(13)C]sodium acetate breath test ([(13)C]-SABT) and technetium Tc 99m albumin colloid radioscintigraphy ((99m)Tc-ACR) in healthy cats., Animals: 12 healthy cats., Procedure: After ingestion of a test meal containing 50 mg of [(13)C]sodium acetate and 250 MBq of (99m)Tc-albumin colloid, each cat underwent simultaneous [(13)C]-SABT and (99m)Tc-ACR on 2 consecutive days. Breath samples and scintigrams were acquired at 30, 60, 90, 120, 150, 180, 210, 240, 300, 360, 480, and 600 minutes after meal ingestion. Quartiles of gastric emptying (25%, 50%, and 75%) were calculated for breath test analysis by use of the area under the curve of the (13)C:(12)C ratio. Quartiles of gastric emptying times were extrapolated from the scintigraphic findings by beans of nonlinear curve regression analysis., Results: Mean ± SD gastric half-emptying (50%) times obtained with [(13)C]-SABT and (99m)Tc-ACR, were 239 ± 28 minutes and 276 ± 59 minutes, respectively. A 2-way repeated-measures ANOVA revealed that mean gastric emptying times determined with [(13)C]-SABT and (99m)Tc-ACR differed significantly. For the stages of gastric emptying, Pearson correlation between the 2 methods was good at 25% (r = 0.655) and weak at 50% (r = 0.588) and 75% (r = 0.566)of gastric emptying., Conclusions and Clinical Relevance: Results indicated that the [(13)C]-SABT can be a valid alternative to (99m)Tc-ACR in healthy cats; it was easy to perform, was tolerated well by the cats, and had acceptable correlation to scintigraphic findings at gastric emptying of 25%, 50% and 75%. Studies in cats with delayed gastric emptying will be needed to verify the validity of the [(13)C]-SABT.

Scintigraphic examination of the thoracic spine is well documented. However, there is limited information about the effects of time on image quality in the period following injection of radionuclide. This study aimed to determine the optimal time point after injection of (99m)Tc-HDP (hydroxymethylene-diphosphonate) to achieve scintigraphic images with the best possible contrast and adequate count rates. Scintigraphic images of the thoracic spine of 21 horses were acquired two, four and six hours after administering (99m)Tc-HDP. Eight regions of interest were drawn in the images, four in the spinous processes and four in the adjacent soft tissue. The bone uptake, soft tissue uptake and the bone-to-soft tissue ratio were determined and compared between the different time points. Total count rates decreased with time after injection, but were at least as high as 150,000 counts per image at every time point after injection. The bone-to-soft tissue ratio was significantly higher for the images acquired after six hours compared to those acquired after two and four hours (P<0.01). Delayed scintigraphic examinations of the spinous processes of the equine thoracic spine achieved images with high contrast and sufficient count rates. Therefore, the scintigraphic examination of the equine thoracic spine is recommended to be done four to six hours after injecting (99m)Tc-HDP. However, additional studies should be performed to determine the effect of delayed image acquisition compared to images taken after three hours on the detectability of lesions in other parts of the thoracic spine and the soft tissue., (British Veterinary Association.)

Renal scintigraphy is performed commonly in dogs and cats and has been used in a variety of other species. In a 2012 survey of the members of the Society of Veterinary Nuclear Medicine, 95% of the respondents indicated they perform renal scintigraphy in their practice. Renal scintigraphy is primarily used to assess renal function and to evaluate postrenal obstruction. This article reviews how renal scintigraphy is used in veterinary medicine and describes the methods of analysis. Species variation is also discussed., (Copyright © 2014 Elsevier Inc. All rights reserved.)

The most common veterinary application of liver scintigraphy is for the diagnosis of portosystemic shunts (PSSs). There has been a continual evolution of nuclear medicine techniques for diagnosis of PSS, starting in the early 1980s. Currently, transplenic portal scintigraphy using pertechnetate or (99m)Tc-mebrofenin is the technique of choice. This technique provides both anatomical and functional information about the nature of the PSS, with high sensitivity and specificity. Hepatobiliary scintigraphy has also been used in veterinary medicine for the evaluation of liver function and biliary patency. Hepatobiliary scintigraphy provides information about biliary patency that complements finding in ultrasound, which may not be able to differentiate between biliary ductal dilation from previous obstruction vs current obstruction. Hepatocellular function can also be determined by deconvolutional analysis of hepatic uptake or by measuring the clearance of the radiopharmaceutical from the plasma. Plasma clearance of the radiopharmaceutical can be directly measured from serial plasma samples, as in the horse, or by measuring changes in cardiac blood pool activity by region of interest analysis of images. The objective of this paper is to present a summary of the reported applications of hepatobiliary scintigraphy in veterinary medicine., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Thyroid scintigraphy is performed in cats and dogs and has been used to a limited degree in other species such as the horse. Thyroid scintigraphy is most commonly used to aid in the diagnosis and treatment management of feline hyperthyroidism but is also used in the evaluation of canine hypothyroidism and canine thyroid carcinoma. This article reviews the normal scintigraphic appearance of the thyroid in the cat, the dog, and the horse and the principles of interpretation of abnormal scan results in the cat and the dog. Radioiodine is the treatment of choice for feline hyperthyroidism, and the principles of its use in the cat are reviewed., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Nuclear scintigraphic examination of equine athletes has a potentially important role in the diagnosis of lameness or poor performance, but increased radiopharmaceutical uptake (IRU) is not necessarily synonymous with pain causing lameness. Nuclear scintigraphy is highly sensitive to changes in bone turnover that may be induced by loading and knowledge of normal patterns of RU is crucial for accurate diagnosis. Blood pool images can be useful for identification of some soft tissue injuries, although acute bone injuries may also have intense IRU in blood pool images. Some muscle injuries may be associated with IRU in bone phase images. The use of scintigraphy together with other diagnostic imaging modalities has helped us to better understand the mechanisms of some musculoskeletal injuries. In immature racehorses, stress-related bone injury is a common finding and may be multifocal, whereas in mature sport horses, a very different spectrum of injuries may be identified. False-negative results are common with some injuries., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Reasons for Performing Study: Intralesional (i.l.) injection is currently the most commonly used technique for stem cell therapy in equine tendon injury. A comparison of different techniques of injection of mesenchymal stem cells for the treatment of tendon lesions is required., Objectives: We hypothesised that vascular perfusion of the equine distal limb with mesenchymal stem cells (MSCs) would result in preferential distribution of MSCs to acute tendon injuries., Study Design: In vivo experimental study., Methods: Lesions were surgically induced in forelimb superficial digital flexor tendons of 8 horses. Three or 10 days after lesion induction, technetium-99 hexamethyl propylene amine oxime-labelled MSCs were injected via i.v. or intra-arterial (i.a.) regional limb perfusion (RLP) at the level of the distal antebrachium and compared to i.l. injection. Mesenchymal stem cell persistence and distribution within the forelimb and tendon lesions was assessed with scintigraphy for 24 h., Results: Lesion uptake was higher with i.l. injection than with RLP, but MSC persistence decreased similarly over time in all 3 techniques. Intra-arterial RLP resulted in a better distribution of MSCs and a higher uptake at the lesion site than i.v. RLP. Limbs perfused i.a. on Day 10 showed greater accumulation of MSCs in the lesion than limbs perfused on Day 3. Arterial thrombosis occurred in 50% of the i.v. RLP limbs and in 100% of the i.a. RLP limbs, which led to clinical complications in one horse., Conclusions and Potential Relevance: Compared with i.l. injection, RLP results in lower uptake but similar persistence of MSCs at the site of tendon lesions. A time dependent accumulation of MSCs was identified with i.a. RLP. The i.a. RLP appears more advantageous than the i.v. RLP in terms of distribution and uptake. However, the described i.a. technique produced arterial thrombosis and thus cannot currently be recommended for clinical use., (© 2013 EVJ Ltd.)

Scintigraphy is currently the reference standard for diagnosing feline hyperthyroidism; however, computed tomography (CT) is more widely available in veterinary practice. The purposes of this prospective study were to describe the CT appearance of thyroid glands in cats with hyperthyroidism and compare CT findings with findings from (99m) Tc-pertechnetate scintigraphy. Twenty-five adult hyperthyroid cats were included. Plain CT images were acquired for each cat and the following characteristics recorded for each thyroid lobe: visibility, delineation, position, attenuation, shape, and subjective size. Scintigraphic images were also acquired and the following characteristics recorded: radiopharmaceutical uptake, delineation, ectopic foci, shape, and subjective size. In CT images, thyroid lobes were most commonly found between the second and fourth cervical vertebrae, dorsolateral to the trachea. Affected thyroid lobes (based on scintigraphy reference standard) were most commonly oval and moderately enlarged in CT images. A heterogeneous attenuation pattern (isoattenuating to adjacent soft tissues with hypo- and hyperattenuating foci) was most commonly found in affected thyroid lobes. A positive correlation (P < 0.01) was identified between CT and scintigraphy for left-to-right thyroid lobe size relationship and subjective size of the larger thyroid lobe. The CT estimated mass was significantly higher (median = 148.8; range = [0;357.6]) for the more active thyroid lobe compared to the less active thyroid lobe (median = 84.6; range = [0;312.3]); (W = 154; P < 0.01). Findings indicated that CT may not reliably differentiate unilateral vs. bilateral hyperthyroidism in cats; however, CT may be a reliable alternative test for correctly identifying the more active thyroid lobe., (© 2013 Veterinary Radiology & Ultrasound.)

In older cats presenting with clinical features of hyperthyroidism, confirming the diagnosis of thyroid disease is usually straightforward. However, the potential for false-negative and false-positive results exists with all thyroid function tests, especially when used for routine screening of large numbers of asymptomatic cats. Therefore, all thyroid function test results must be interpreted in light of the cat's history, clinical signs, and other laboratory findings. If a high serum thyroxine (T4) value is found in a cat that lacks clinical signs of hyperthyroidism, or if hyperthyroidism is suspected in a cat with normal total T4 concentrations, repeating the total T4 analysis, determining the free T4 concentration, or performing thyroid scintigraphy may be needed to confirm the diagnosis.

Although naturally occurring hypothyroidism is very rare in cats, iatrogenic hypothyroidism is a recognized complication of treatment for hyperthyroidism. However, confirming the diagnosis of hypothyroidism in cats is not generally straightforward. The potential for false-negative and false-positive results exists with all thyroid function tests, especially in older cats that may have concurrent nonthyroidal illness. Therefore, all thyroid function test results must be interpreted in light of the cat's history, clinical signs, and other laboratory findings. If a low to low-normal serum thyroxine (T4) value is found in a cat that has been treated for hyperthyroidism, repeating the total T4 analysis, determining free T4 and thyroid stimulating hormone (TSH) concentrations, or performing a TSH stimulation test or thyroid scintigraphy may be needed to confirm the diagnosis.

Scintigraphy is an extremely sensitive tool for the detection of early changes in bone metabolism. Sixty-eight lame dogs underwent a scintigraphic examination. For each elbow lateromedial (LM), caudomedial (CdM) flexed and caudomedial (CdM) extended scintigraphic views were obtained. Semi-quantitative analysis was performed to determine radiopharmaceutical uptake at the medial coronoid process (MCP) and at the attachment of the flexor muscles at the medial humeral epicondyle, normalised to activity registered in either the total elbow joint or the radius/ulna. MCP pathology/flexor enthesopathies were divided into simple (containing one abnormality) or complex (containing more than one abnormality) lesions. The influence of different views or normalisation procedures on sensitivity and specificity was evaluated. MCP lesions were detected on radiography, ultrasound, computed tomography, magnetic resonance imaging and/or arthroscopy in 49 elbows, with 13 simple and 36 complex lesions. Flexor enthesopathy was diagnosed in 54 elbows, with 14 simple and 40 complex lesions. In seven elbows only degenerative changes were present, whereas in 50 elbows no abnormalities could be detected. MCP lesions were best detected with the CdM extended view, whereas for flexor enthesopathy the CdM flexed view offered the best result. To detect simple lesions, the normalisation procedure to the elbow gave the best result, whereas normalisation to the radius/ulna was the best choice for complex lesions. This study suggests that semi-quantification is a valuable method in case of simple pathology, especially when MCP lesions are considered. For elbows with complex lesions, the quantification procedure is less reliable., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Reasons for Performing Study: Veterinarians have observed a putative change in the location of humeral stress remodelling in Thoroughbred racehorses with change from dirt to synthetic racetrack surfaces., Objectives: To determine whether the location and severity of humeral stress remodelling differs between Thoroughbred racehorses exercising on dirt and synthetic racetrack surfaces, the potential significance of different locations of stress remodelling, and the potential usefulness of scintigraphy for prevention of complete humeral fracture., Methods: Scintigraphic images of humeri from 841 Thoroughbred racehorses at 3 racetracks during 2 years before and after conversion from dirt to synthetic surfaces were evaluated for location and severity of lesions. The effects of surface on lesion distributions were examined using Chi-square or Fisher's exact tests. Archived fractured humeri were examined to determine the location and severity of stress remodelling associated with complete fracture. Databases were queried to determine whether racehorses with scintigraphic lesions suffered humeral fracture and whether racehorses with a complete humeral fracture had had a scintigraphic examination., Results: Horses at synthetic racetracks had a greater proportion of distal humeral lesions, whereas horses at dirt racetracks had a greater proportion of caudoproximal lesions (P<0.001). Proximal lesions were more likely to be severe than distal lesions (P<0.001). Most complete fractures were associated with caudoproximal lesions, which were more often severe than distal lesions (P = 0.002). None of the horses with a scintigraphic lesion had a complete humeral fracture. None of the horses with a complete humeral fracture underwent scintigraphic examination., Conclusions: Race surface affected humeral scintigraphic lesion location and hence the location of stress remodelling. Lesion severity was associated with lesion location. Complete humeral fracture was associated with caudoproximal stress remodelling and lack of scintigraphic examination., Potential Relevance: Risk for complete humeral fracture may be lower on synthetic surfaces than on dirt surfaces, and, by inference, for horses examined using scintigraphy., (© 2012 EVJ Ltd.)

Equine bone scintigraphy is usually performed with horses in standing position under sedation. However, swaying motion often leads to poor-quality images. To examine the usefulness of motion correction (MC) processing, equine bone scintigrams were evaluated using Scheffé's method of paired comparisons. A significant difference in evaluation scores was detected by analysis of variance (F test, P<0.01). According to all observers, Yardstick analysis scores were higher for images use of MC processing than for those no use of MC processing, for all parts. Overall scores of 5 observers were as follows: without MC 100% acquisition time (AT, lowest), use of MC with 25% AT, MC 50% AT, MC 75% AT and MC 100% AT (highest). Thus, MC processing shortens AT in equine bone scintigraphy, and it contributes to a reduction in the external radiation exposure of nurses/technicians.