To assess visualization of the intracranial arteries and internal carotid artery (ICA) on 3-D time-of-flight (TOF) magnetic resonance angiography (MRA) images obtained at 1.5 T and to investigate factors that affect the image quality of those arteries in dogs.
39 dogs with idiopathic epilepsy.
Each dog underwent 3-D TOF MRA, and 5 pairs of intracranial arteries, the basilar artery, and both ICAs were evaluated. Each artery was assigned an image-quality score on a scale of 0 to 3, where 0 = poor and 3 = excellent. Multivariable regression analysis was used to assess whether age, body weight (BW), serum total cholesterol concentration, intracranial volume (ICV), and mean arterial pressure were significantly associated with the image quality of each vessel.
In all dogs, the image-quality score was 2 or 3 for the proximal middle cerebral arteries, basilar artery, and caudal aspect of the caudal communicating arteries. In some dogs, the rostral cerebellar arteries, rostral aspect of the caudal communicating arteries, and middle and rostral aspects of the ICA were poorly visualized. For various arteries, image quality was negatively associated with age and positively associated with BW and ICV.
CONCLUSIONS AND CLINICAL RELEVANCE
Results indicated that 3-D TOF MRA images obtained at 1.5 T did not consistently and clearly delineate the ICA and narrow or peripheral intracranial arteries of dogs; therefore, careful attention is required when such images are assessed. Patient age, BW, and ICV can also affect the image quality of some intracranial arteries on 3-D TOF MRA images. (Am J Vet Res 2019;80:480–489)
OBJECTIVE To compare conventional MRI and nonenhanced 3-D time-of-flight (TOF) magnetic resonance angiography (MRA) findings between dogs with meningioma and dogs with intracranial histiocytic sarcoma (IHS).
DESIGN Retrospective case series.
ANIMALS 14 dogs with meningioma and 5 dogs with IHS.
PROCEDURES Medical records of dogs with meningioma or IHS that were examined at a tertiary veterinary hospital from 2010 through 2014 and underwent 3-D TOF MRA in conjunction with conventional MRI were reviewed. Findings for conventional MRI and 3-D TOF MRA were compared between the 2 groups of dogs to evaluate whether there were any characteristics that could be used to differentiate meningioma from IHS.
RESULTS Tumor type was significantly associated with signal intensity on conventional T2-weighted and fluid-attenuated inversion recovery MRI images; most meningiomas were hyperintense, and most IHSs were isointense or hypointense on those images. Tumor type was not associated with signal uniformity, tumor location, tumor origin, or the presence of edema, midline shift, or brain herniation. On MRA, blood vessels adjacent to the tumor were identified and characterized for 9 of 14 dogs with meningioma and all 5 dogs with IHS. Vessels adjacent to meningiomas were displaced in 8 of 9 dogs, whereas vessels adjacent to IHSs were not displaced.
CONCLUSIONS AND CLINICAL RELEVANCE Results indicated nonenhanced 3-D TOF MRA findings provided additional information that can be assessed in conjunction with conventional MRI findings to help differentiate meningiomas from IHSs in dogs.
Objective—To investigate age-related and regional differences in estimated metabolite concentrations in the brain of healthy dogs by means of magnetic resonance spectroscopy (MRS).
Animals—15 healthy Beagles.
Procedures—Dogs were grouped according to age as young (n = 5; all dogs were 2 months old), adult (5; mean age, 4.5 years), or geriatric (5; all dogs were 12 years old). Imaging was performed by use of a 1.5-T MRI system with T1- and T2-weighted spin-echo and fluid-attenuated inversion recovery sequences. Signal intensity measurements for N-acetyl aspartate, creatine, choline, and lactate-alanine (the spectroscopic peaks associated with alanine and lactate could not be reliably differentiated) were determined with MRS, and areas under the spectroscopic peaks (representing concentration estimates) were calculated. Ratios of these metabolite values were compared among age groups and among brain regions with regression analysis.
Results—The choline-to-creatine ratio was significantly higher in young dogs, compared with other age groups. The N-acetyl aspartate-to-choline ratio was significantly lower in young dogs and geriatric dogs than in adult dogs. When all age groups were considered, the choline-to-creatine ratio was significantly higher and N-acetyl aspartate-to-choline ratio was significantly lower in the frontal lobe than in all other regions. The N-acetyl aspartate-to-creatine ratio was significantly lower in the cerebellum than in other regions.
Conclusions and Clinical Relevance—Metabolite ratios varied significantly among age groups and brain regions in healthy dogs. Future studies should evaluate absolute concentration differences in a larger number of dogs and assess clinical applications in dogs with neurologic diseases.
Objective—To characterize clinical signs and findings from magnetic resonance imaging (MRI) and CSF analysis for dogs with progressive myelomalacia (PM) diagnosed on the basis of clinical and histologic features.
Design—Retrospective case series.
Animals—5 dogs with confirmed PM and 7 with presumptive PM evaluated from 1997 through 2008.
Procedures—Medical records of study dogs were reviewed, and clinical signs and MRI and CSF findings were evaluated. A clinical diagnosis of PM was made on the basis of detection of disk-associated spinal cord compression via MRI and progression of clinical signs from initial paraparesis or paraplegia to thoracic limb lower motor neuron paresis to tetraplegia associated with cranial migration of the extent of cutaneous trunci reflex extinction and analgesia, terminating in death due to respiratory paralysis.
Results—All dogs were paraplegic and had signs of lower motor neuron lesions. As revealed by MRI of the vertebral column, the length of abnormal signal intensity was more than 6-fold, compared with the body length of L2. In some dogs, these abnormal MRI findings were observed before PM was clinically diagnosed. The CSF examination revealed hemorrhagic xanthochromia.
Conclusions and Clinical Relevance—A hyperintense region of the spinal cord > 6 times the length of L2 on T2-weighted imaging might be a characteristic MRI finding of PM. In some dogs, such MRI findings were observed before PM was clinically diagnosed. Progressive myelomalacia may thus be diagnosable at the early stage through MRI and CSF examination before signs of PM develop.