REGIONAL BRAIN PERFUSION IN 10 NORMAL DOGS MEASURED USING TECHNETIUM‐99m ETHYL CYSTEINATE DIMER SPECT

Abstract

Single photon emission computed tomography (SPECT) of the brain using perfusion tracers allows estimation of regional brain perfusion. This allows in vivo examination of brain function in the setting of neuropsychologic and pathophysiologic changes. However functional imaging data on brain perfusion in dogs are limited. Hence, the aim of this study was to determine the scintigraphic regional perfusion pattern of the normal canine brain. Ten healthy shepherd type dogs were injected with 925 MBq Technetium-99m ethyl cysteinate (ECD) 20 minutes before the examination. Acquisition was performed using a triple head gamma camera equipped with fanbeam collimators. Uniform attenuation correction and triple energy window correction were applied. Computed tomographic images were obtained from the same dogs, reoriented along the orbito-meatal axis and SPECT perfusion data were coregistered to the CT-volume data. Based on morphological and suggested brain divisions, regions-of-interest (ROIs) were defined for the bilateral frontocerebral, temporocerebral, parietocerebral, occipitocerebral, cerebellar, thalamic, and striatal area. Regional count density was normalized on total counts. All dogs had the highest uptake in the thalamic/striatal area compared to a rather homogeneous cerebral uptake. No significant left/right count differences were found, but a rostro-caudal gradient (+12-13%) was present. In this group, age and gender did not influence the perfusion pattern.

Cerebral Metabolism in Dogs Assessed by 18F-FDG PET: A Pilot Study to Understand Physiological Changes in Behavioral Disorders in Dogs

“…Thus, the age and sex of our subjects were biased towards a young age and the female gender. A previous study of normal dogs that analyzed regional brain perfusion using technetium-99 m ethyl cysteinate dimer and single photon emission computed tomography (SPECT) found that in normal shepherd-mix dogs, age (1 to 9 years) and gender did not influence the perfusion pattern in 7 ROIs, frontal cerebral, temporal cerebral, parietal cerebral, occipital cerebral, cerebellar, thalamic and striatal areas [8]. Cerebral glucose metabolism and cerebral blood flow correlate positively [14] thus, it is assumed that the effect of age and sex are not critical.…”

Regional brain perfusion in 12 cats measured with technetium-99m-ethyl cysteinate dimer pinhole single photon emission computed tomography (SPECT)

“…In the feline brain the cerebellum is the region with the lowest perfusion index, whereas, in dogs, the cerebellar tracer uptake is higher than in the cortical regions, but lower than in the subcortical region. 5 An age-related decrease in the ECD perfusion pattern and an increased left-right asymmetry was observed in several brain regions in humans. 6,15 Also, in dogs, a decreased perfusion in the frontotemporal cortex and in the subcortical region, together with a significant leftright difference in the parietal cortex, was reported in a group of 'aged' dogs (older than 96 months) when compared with a reference group (aged between 12 and 84 months).…”

“…Similar to dogs and humans, the uptake of 99m Tc-ECD also varies significantly between brain regions in the feline brain. 5,6,15 The highest uptake occurs in the subcortical structures like the amygdala, hippocampus, basal ganglia and thalamus, and in the cingulate gyrus (Table 2), which reflects the relative dominance of these structures in feline behaviour. ECD is a 99m Tc-labelled lipophilic tracer used for SPECT imaging of rCBF.…”

“…25 In dogs, 99m Tc-ECD rCBF datasets of healthy adults have already been created. 5,11 This created the possibility of comparing the rCBF of dogs suffering from pathological anxiety, impulsive aggression or epilepsy with the perfusion pattern of healthy subjects. 10,11,26 Also, in humans, the importance of such a rCBF dataset of healthy volunteers has already been emphasised.…”

“…2 The lipophilic 99m Tc-ECD crosses the blood-brain barrier and is trapped intracellularly, proportionally to the cerebral blood flow, within 2 mins after intravenous (IV) injection, probably by de-esterification to polar complexes. [3][4][5] This results in a fixed distribution of the tracer, representing the regional cerebral blood flow (rCBF) at the time of tracer injection.…”