Fluorine‐18 fluorodeoxyglucose positron emission tomography imaging exhibits increased SUVmax at the level of the spinal intumescence in normal dogs

Abstract

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.

Imaging techniques in veterinary medicine. Part II: Computed tomography, magnetic resonance imaging, nuclear medicine

“…Those techniques are even more sensitive than the morphological techniques in the early detection of many diseases. However, they are often combined with CT or Magnetic Resonance (MRI) to provide morphological reference points to the PET or SPECT functional images [160] .…”

“…SPECT imaging is widely used in Human medicine to diagnose heart ischemia, but this pathology is rare in small animals. Furthermore, in Veterinary medicine there is not a great interest about the study of neuroreceptors, or brain perfusion, thus raising the main interest of SPECT: the study of neurological diseases [139] , [140] , [141] , [142] , [143] , [144] , [145] , [146] , [147] , [148] , [149] , [150] , [151] , [152] , [153] , [154] , [155] , [156] , [157] , [158] , [159] , [160] , [161] , [162] , [163] , [164] , [165] , [166] , [167] , [168] , [169] , [170] , [171] , [172] , [173] , [174] , [175] . Fig.…”

External Exposure to Veterinary Staff and Pet Owners from ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) Positron Emission Tomography

“…However, some studies reported inducing general anesthesia and placing the patient on the PET scanner bed, and then injecting the radiotracer. [24][25][26][27][28] Martinez et al 17) reported that the estimated radiation dose during a PET/CT scan when 18 F-FDG injection was performed before anesthesia induction was higher than the 18 Japanese legislation restricts the 24 h detention period of radioactive animal patients when administering FDG radiopharmaceuticals. Thus, steps of the 18 F-FDG PET imaging protocol, evaluation of the external radiation exposure for veterinary staff in Japan under the applied SPECT system, necessity of the 24 h detention period of animal patients in hospitals, and risk assessment of owners are discussed in this study to increase familiarity and confidence in the PET fields of veterinary staff.…”