Flourine-18 fluorodeoxyglucose positron emission tomography imaging exhibits increased SUVmax at the level of the spinal intumescence in normal dogs.

Positron emission tomography (PET) imaging utilizing fluorine-18 labeled fluorodeoxyglucose is a relatively new imaging modality in veterinary medicine that is becoming more common for oncological staging and for musculoskeletal imaging. Thus, it is important to identify the normal variations on PET imaging that may be mistaken for pathology. Variation in standardized uptake values (SUVmax) have been anecdotally identified in the spinal cord of dogs undergoing fluorodeoxyglucose (FDG) PET-CT examinations for oncological staging, with notable increase in SUVmax values identified in the region of the cervical and lumbar spinal intumescences. The aim of this retrospective, analytical study was to compare the SUVmax values at four different locations throughout the spinal cord (C3, C5-T1, T13, and L3-S1) of a group of dogs with no evidence of neurologic disease and compare those findings to histologic specimens from dogs euthanized for unrelated disease. SUVmax values were significantly higher at the cervical and lumbar intumescences in comparison to the control regions (P < .0001 and P < .0001, respectively). Neuronal count and spinal cord gray matter area were also significantly greater at the cervical and lumbar intumescences (neuronal count P = .0025 and P = .0001; area P = .0004 and P = .0009, respectively) while overall neuronal density was lower (P = .003 and P = .028, respectively). We presume the increased SUVmax values at the spinal cord intumescences are the result of overall increased neuron count, increased proportion of gray matter, and increased spinal cord gray matter area. These findings will aid in the interpretation of future PET-CT studies and hopefully prevent the misdiagnosis of spinal cord disease in normal canines.

Ultrasonographic features of mesenteric cysticercosis in a domestic rabbit (Oryctolagus cuniculus).

A 5-year-old, 0.92-kg (2-lb), spayed female Dwarf Hotot rabbit was evaluated for a 1-day duration of lethargy and anorexia. Survey radiographs revealed evidence of gastrointestinal stasis. Abdominal ultrasonography characterized multiple small, round, anechoic structures embedded in the mesentery. These structures were thin walled with hyperechoic strands/septations. Most of the structures contained a well-defined, eccentric, hyperechoic nodule adherent to the intraluminal wall. Mesenteric cysticercosis was confirmed via exploratory laparotomy and histopathology. To the authors' knowledge, this is the first description of the ultrasonographic features of mesenteric cysticercosis in a domestic rabbit.

The prognostic significance of metabolic tumour volume and total lesion glycolysis for dogs staged for appendicular osteosarcoma with fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography.

Metabolic tumour volumes (MTV) and total lesion glycolysis (TLG) are metabolic parameters that are becoming more commonly reported in human medicine to quantify tumours detected on fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (18 F-FDG PET/CT). In this retrospective study dogs afflicted with appendicular osteosarcoma that were staged with 18 F-FDG PET/CT had MTV and TLG at a variety of set and fixed thresholds calculated by two observers. These values, along with SUVmax , were evaluated for prognostic significance in this population of dogs. There was excellent correlation between two observers for all values. Multiple volumetric parameters were significantly associated with survival. SUVmax had the highest sensitivity for survival and TLG at 2.5 SUV*cm3 had the highest specificity for prediction of survival based on ROC calculations. The SUVmax , MTV at 2.5 SUV and TLG at 2.5 SUV*cm3 were significantly different between dogs that survived more than or less than 1 year. This study is the first of its kind in veterinary medicine that retrospectively evaluated volumetric tumour values for prognostic significance and may provide a basis for standardized method of reporting 18 F-FDG PET/CT results.

Staging canine patients with appendicular osteosarcoma utilizing fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography compared to whole body computed tomography.

Few studies have investigated the diagnostic performance of fluorine-18-fluorodeoxyglucose (18 F-FDG) positron emission tomography/computed tomography (PET/CT) for staging veterinary patients with appendicular osteosarcoma. The purpose of this study was to evaluate the efficacy of 18 F-FDG-PET/CT compared to whole-body CT (WBCT) for staging canine patients with appendicular osteosarcoma. The 18 F-FDG-PET/CT imaging studies of 66 dogs with appendicular osteosarcoma were anonymized and separated into two detached studies (one with whole body pre- and post-contrast CT images and the other with the whole body pre- and post-contrast CT images with the associated 18 F-FDG-PET overlay). Image assessment was performed retrospectively by five board-certified veterinary radiologists. The radiologists were instructed to assign a predefined categorical score (1-4) to each pre-designated anatomic region based on a devised lesional scoring system. A score of 1 was normal, 2 abnormal but not neoplastic, 3 abnormal and concerning for neoplasia, and 4 abnormal, most likely neoplastic. Overall, the likelihood of detection of '3 or 4' was found to be significantly higher with 18 F-FDG PET/CT when compared to WBCT after adjusting for the effect of evaluator and the subject. Most significantly, 13 osseous lesions concerning for metastasis (scored 3-4) were identified in 10/66 dogs by at least one reviewer on 18 F-FDG PET/CT, which were not identified by any reviewer on WBCT. Additionally, four comorbid neoplastic lesions were identified with 18 F-FDG PET/CT and not with WBCT. The results of this study suggest that 18 F-FDG PET/CT is more efficacious in detecting metastatic and comorbid neoplastic lesions compared to WBCT in dogs with appendicular osteosarcoma.

Prognostic value of fluorine18 flourodeoxyglucose positron emission tomography/computed tomography in dogs with appendicular osteosarcoma.

BACKGROUND: Factors indicative of a negative prognosis for appendicular osteosarcoma (OSA) in dogs are visible metastatic disease, location, and size of lesion. In human medicine maximum standard uptake value (SUVmax ), as measured on a fluorine18 flourodeoxyglucose positron emission tomography/computed tomography (18 F-FDG PET/CT), is prognostic for survival for several tumor types. OBJECTIVE: Determine if SUVmax is associated with progression-free interval (PFI) and determination of survival in dogs with appendicular OSA. ANIMALS: Sixty-two dogs with untreated appendicular OSA that had been staged with 18 F-FDG PET/CT. METHODS: Retrospective analysis of the 18 F-FDG PET/CT was performed. Dogs were excluded from the study if they did not receive definitive intent treatment for their primary OSA and adjuvant chemotherapy with carboplatin, or had visible metastatic disease on initial imaging. A region of interest (ROI) was created around the primary tumor to measure SUVmax . Univariable and multivariable Cox proportional hazards analysis was performed to evaluate for associations between variables including SUVmax and outcome of PFI and overall survival (OS). RESULTS: Maximum standard uptake value of the primary tumor was significantly associated with the OS (P = .04) with adjustment for treatment type and monocyte count. The overall median survival time (OST) was 284 days (range, 39-1293 days) with the OST of dogs having an SUVmax of ≥7.4 of 254 days (range, 98-428 days) and dogs with an SUVmax of <7.4 of 680 days (range, 108-811 days, P = .01). CONCLUSIONS AND CLINICAL IMPORTANCE: Maximum standard uptake value as measured via 18 F-FDG PET/CT is significantly associated with survival in dogs with appendicular OSA with a high SUVmax being an indicator of a negative prognosis.