Fast three-dimensional contrast-enhanced magnetic resonance angiography of the canine lumbar spinal cord vascular supply: A feasibility study.

Magnetic resonance angiography (MRA) is the noninvasive spinal cord vascular imaging modality of choice in human medicine. The aim of this exploratory, prospective, descriptive study was to assess the feasibility of fast three-dimensional (3D) contrast-enhanced (CE) MRA for visualization of spinal vascular structures in the canine lumbar region. Fourteen canine patients weighing > 5 kg were included. The lumbar arteries were consistently visualized (14/14;100%). Spinal arteries, radicular branches, great radicular artery (of Adamkiewicz), ventral spinal artery, and dorsal spinal arteries were not visualized (0/14;0%). The internal vertebral venous plexus was visualized in 11 of 14 (79%) dogs. Overall, the results of this study show that fast 3D CE-MRA of the lumbar region in dogs is feasible. However, the smaller arteries responsible for the spinal cord vascular supply were not visualized in this study.

Ferumoxytol-enhanced magnetic resonance angiography provides comparable vascular conspicuity to CT angiography in dogs with intrahepatic portosystemic shunts.

Computed tomography angiography (CTA) is currently the gold standard imaging modality for anatomically characterizing canine hepatic vascular anomalies; with conventional, gadolinium-enhanced MR angiography being less frequently utilized. However, both imaging modalities are limited by a brief, first pass peak of contrast medium in the vasculature that necessitates precisely timed image acquisition. A long-acting purely intravascular magnetic resonance imaging (MRI) contrast agent, ferumoxytol, offers the potential to reduce complexity of magnetic resonance angiography (MRA) protocol planning by ensuring diagnostic contrast medium concentration in all the vessels that are targeted for imaging. Aims of this prospective, pilot, methods comparison study were to develop an optimized MRA protocol using ferumoxytol in dogs with hepatic vascular anomalies, perform a dose escalation trial to compare image quality with four-dose regimens of ferumoxytol, and compare accuracy of vascular anatomic depiction based on the gold standard of CTA. Six dogs (10.7-36.1 kg) with portosystemic shunts (four intrahepatic left divisional shunts and two intrahepatic right divisional shunts) were recruited for inclusion in the study. A dose-escalation trial was performed to compare image quality at four incremental dose levels of ferumoxytol (1, 2, 3, and 4 mg/kg) and to compare the accuracy of vascular anatomic detection to CTA. Ferumoxytol contrast-enhanced MRA (CE-MRA) at 4 mg/kg provided similar conspicuity of normal and abnormal vasculature compared to CTA with a minimal decrease in spatial resolution. Findings indicated that ferumoxytol holds promise for comprehensive, single breath hold CE-MRA of all abdominal vessels in dogs with portosystemic shunts. Background information provided in this study can be used to support development of other future applications such as intracranial and cardiac MRA, real-time imaging, flow quantification, and potentially sedated MRI imaging.

Cardiovascular effects of two adenosine constant rate infusions in anaesthetized dogs.

OBJECTIVE: Adenosine induces vasodilatation. The aim of this study was to investigate cardiovascular effects of two adenosine constant rate infusion (CRI) doses in dogs. STUDY DESIGN: Experimental, longitudinal repeated measure design. ANIMALS: Ten healthy purpose-bred Beagle dogs. METHODS: Each dog was sedated with butorphanol. Anaesthesia was induced with propofol intravenously and maintained with sevoflurane (inspired oxygen fraction = 47-55%). Controlled mechanical ventilation was used to maintain normocapnia. Two doses of adenosine were administered as CRIs to each dog: 140 µg kg-1 minute-1 (A140) followed by 280 µg kg-1 minute-1 (A280). Pulse rate, invasive arterial pressure and stroke volume (by magnetic resonance phase contrast angiography) were measured at baseline, 3 minutes after starting adenosine and 3 and 10 minutes after discontinuing adenosine. Cardiac output, cardiac index and approximated systemic vascular resistances (approximate SVR) were calculated. Additionally, arterial blood gases, co-oximetry, electrolytes, glucose and lactate were measured and oxygen content and delivery calculated. One-way repeated measures analysis of variance (p < 0.05) was used for data analysis. RESULTS: A140 and A280 resulted in a significant decrease in arterial blood pressure [systolic (p = 0.008), mean (p = 0.003), and diastolic arterial pressure (p = 0.004)] and approximate SVR (p = 0.008) compared with baseline. No significant changes were detected for the other variables. All values returned to baseline within 3 minutes after adenosine discontinuation. CONCLUSIONS AND CLINICAL RELEVANCE: Adenosine CRI decreases arterial pressure by vasodilatation in healthy dogs. No additional effects were observed with the higher dose. The effects in compromised dogs remain to be investigated.

Cardiac-gated, phase contrast magnetic resonance angiography is a reliable and reproducible technique for quantifying blood flow in canine major cranial abdominal vessels.

Blood flow changes in cranial abdominal vessels are important contributing factors for canine hepatic disease. This prospective, experimental, pilot study aimed to evaluate cardiac-gated, phase contrast magnetic resonance angiography (PCMRA) as a method for characterizing blood flow in canine major cranial abdominal vessels. Eleven, healthy, adult beagle dogs were sampled. Cardiac-gated, phase contrast magnetic resonance angiography of the cranial abdomen was performed in each dog and blood flow was independently measured in each of the major cranial abdominal vessels by three observers, with two observers recording blood flow values once and one observer recording blood flow values three times. Each dog then underwent ultrasonographic examination of the liver with fine needle aspirations and biopsies submitted to cytologic and histologic examination. The mean absolute stroke volume and velocity were respectively 9.6 ± 1.9 ml and -11.1 ± 1.1 cm/s for the cranial abdominal aorta, 2.1 ± 0.6 ml and -6.6 ± 1.9 cm/s for the celiac artery, and 2.3 ± 1.0 ml and -7.9 ± 3.1 cm/s for the cranial mesenteric artery. The mean absolute stroke volume and velocity were respectively 6.7 ± 1.3 ml and 3.9 ± 0.9 cm/s for the caudal vena cava and 2.6 ± 0.9 ml and 3.2 ± 1.2 cm/s for the portal vein. Intraobserver reliability was excellent (intraclass correlation coefficient > 0.9). Interobserver reproducibility was also excellent (intraclass correlation coefficient 0.89-0.99). Results of liver ultrasonography, cytology, and histopathology were unremarkable. Findings indicated that cardiac-gated, phase contrast magnetic resonance angiography is a feasible technique for quantifying blood blow in canine major cranial abdominal vessels. Blood flow values from this sample of healthy beagles can be used as background for future studies on canine hepatic disease.

Evidence for Concerted and Mosaic Brain Evolution in Dragon Lizards.

The brain plays a critical role in a wide variety of functions including behaviour, perception, motor control, and homeostatic maintenance. Each function can undergo different selective pressures over the course of evolution, and as selection acts on the outputs of brain function, it necessarily alters the structure of the brain. Two models have been proposed to explain the evolutionary patterns observed in brain morphology. The concerted brain evolution model posits that the brain evolves as a single unit and the evolution of different brain regions are coordinated. The mosaic brain evolution model posits that brain regions evolve independently of each other. It is now understood that both models are responsible for driving changes in brain morphology; however, which factors favour concerted or mosaic brain evolution is unclear. Here, we examined the volumes of the 6 major neural subdivisions across 14 species of the agamid lizard genus Ctenophorus (dragons). These species have diverged multiple times in behaviour, ecology, and body morphology, affording a unique opportunity to test neuroevolutionary models across species. We assigned each species to an ecomorph based on habitat use and refuge type, then used MRI to measure total and regional brain volume. We found evidence for both mosaic and concerted brain evolution in dragons: concerted brain evolution with respect to body size, and mosaic brain evolution with respect to ecomorph. Specifically, all brain subdivisions increase in volume relative to body size, yet the tectum and rhombencephalon also show opposite patterns of evolution with respect to ecomorph. Therefore, we find that both models of evolution are occurring simultaneously in the same structures in dragons, but are only detectable when examining particular drivers of selection. We show that the answer to the question of whether concerted or mosaic brain evolution is detected in a system can depend more on the type of selection measured than on the clade of animals studied.

Pulmonary perfusion quantification with flow-sensitive inversion recovery (FAIR) UTE MRI in small animal imaging.

Blood perfusion in lung parenchyma is an important property for assessing lung function. In small animals, its quantitation is limited even with radioactive isotopes or dynamic contrast-enhanced MRI techniques. In this study, the feasibility flow-sensitive alternating inversion recovery (FAIR) for the quantification of blood flow in lung parenchyma in free breathing rats at 7 T has been investigated. In order to obtain sufficient signal from the short T2 * lung parenchyma, a 2D ultra-short echo time (UTE) Look-Locker read-out has been implemented. Acquisitions were segmented to maintain acquisition time within an acceptable range. A method to perform retrospective respiratory gating (DC-SG) has been applied to investigate the impact of respiratory movement. Reproducibilities within and between sessions were estimated, and the ability of FAIR-UTE to identify the decrease of lung perfusion under hyperoxic conditions was tested. The implemented technique allowed for the visualization of lung parenchyma with excellent SNR and no respiratory artifact even in ungated acquisitions. Lung parenchyma perfusion was obtained as 32.54 ± 2.26 mL/g/min in the left lung, and 34.09 ± 2.75 mL/g/min in the right lung. Application of retrospective gating significantly but minimally changes the perfusion values, implying that respiratory gating may not be necessary with this center-our acquisition method. A decrease of 10% in lung perfusion was found between normoxic and hyperoxic conditions, proving the feasibility of the FAIR-UTE approach to quantify lung perfusion changes.

Variations in magnetic resonance venographic anatomy of the dorsal dural venous sinus system in 51 dogs.

Variations in intracranial dural venous sinus anatomy have been widely reported in humans, but there have been no studies reporting this in dogs. The purpose of this retrospective study was to describe variations in magnetic resonance (MR) venographic anatomy of the dorsal dural venous sinus system in a sample population of dogs with structurally normal brains. Medical records were searched for dogs with complete phase contrast, intracranial MR venograms and a diagnosis of idiopathic epilepsy. Magnetic resonance venograms were retrieved for each dog and characteristics of the dorsal dural sinuses, symmetry of the transverse sinuses and other anatomic variations were recorded. A total of 51 dogs were included. Transverse sinus asymmetry was present in 58.8% of the dogs, with transverse sinus hypoplasia seen in 39.2%, and aplasia in 23.5% of dogs. For 70.6% of dogs, at least one anatomic variation in the dorsal sagittal sinus was observed, including deviation from the midline (33.3%) and collateral branches from either the dorsal sagittal sinus or dorsal cerebral veins (54.9%). In 5 dogs (9.8%) a vessel was also identified running from the proximal transverse sinus to the distal sigmoid sinus, in a similar location to the occipital sinus previously reported in children. Findings from this study indicated that, as in humans, anatomic variations are common in the intracranial dural venous sinus system of dogs. These anatomic variations should be taken into consideration for surgical planning or diagnosis of cerebrovascular disease.

Time-of-flight magnetic resonance angiography of the canine brain at 3.0 Tesla and 7.0 Tesla.

OBJECTIVE: To evaluate the ability of 2-D time-of-flight (ToF) magnetic resonance angiography (MRA) to depict intracranial vasculature and compare results obtained with 3.0- and 7.0-T scanners in dogs. ANIMALS: 5 healthy Beagles. PROCEDURES: 2-D ToF-MRA of the intracranial vasculature was obtained for each dog by use of a 3.0-T and a 7.0-T scanner. Quantitative assessment of the images was obtained by documentation of the visibility of major arteries comprising the cerebral arterial circle and their branches and recording the number of vessels visualized in the dorsal third of the brain. Qualitative assessment was established by evaluation of overall image quality and image artifacts. RESULTS: Use of 3.0- and 7.0-T scanners allowed visualization of the larger vessels of the cerebral arterial circle. Use of a 7.0-T scanner was superior to use of a 3.0-T scanner in depiction of the first- and second-order arterial branches. Maximum-intensity projection images had a larger number of vessels when obtained by use of a 7.0-T scanner than with a 3.0-T scanner. Overall, image quality and artifacts were similar with both scanners. CONCLUSIONS AND CLINICAL RELEVANCE: Visualization of the major intracranial arteries was comparable with 3.0- and 7.0-T scanners; the 7.0-T scanner was superior for visualizing smaller vessels. Results indicated that ToF-MRA is an easily performed imaging technique that can be included as part of a standard magnetic resonance imaging examination and should be included in the imaging protocol of dogs suspected of having cerebrovascular disease.

In vivo measurement of local aortic pulse-wave velocity in mice with MR microscopy at 17.6 Tesla.

Transgenic mouse models of human diseases have gained increasing importance in the pathophysiology of cardiovascular diseases (CVD). As an indirect measure of vascular stiffness, aortic pulse-wave velocity (PWV) is an important predictor of cardiovascular risk. This study presents an MRI approach that uses a flow area method to estimate local aortic pulse-wave velocity at different sites in the murine aorta. By simultaneously measuring the cross-sectional area and the through-plane velocity with a phase-contrast CINE method, it was possible to measure average values for the PWV in the ascending and descending aorta within the range of 2.4-4.3 m/s for C57BL/6J mice (ages 2 and 8 months) and apoE-knockout mice (age 8 months). Statistically significant differences of the mean values of the PWV of both groups could be determined. By repeating CINE measurements with a time delay of 1 ms between two subsequent data sets, an effective temporal resolution of 1000 frames/s (fps) could be achieved.

Validation of cerebral blood perfusion imaging as a modality for quantitative pharmacological MRI in rats.

The aim of this study was to validate continuous arterial spin labeling (CASL) as a quantitative imaging modality for pharmacological MRI (phMRI) based on local cerebral blood perfusion. Specifically, the capability of CASL to assess brain-activity signatures of pharmacological interventions in animal models was evaluated with respect to drug discovery in diseases of the central nervous system (CNS). Perfusion as a surrogate for neuronal activity was measured in various brain areas of the rat. The validation approach was threefold. First, perfusion was shown to reliably reflect differential effects of anesthesia on striatal activation. Different baseline levels and different temporal response profiles after amphetamine challenges under isoflurane, propofol, ketamine, and alpha-chloralose anesthesia were consistent with known properties of these anesthetics. Second, remarkable consistency of multi-area baseline perfusion patterns between independent groups of animals confirmed the notion that CASL is highly reproducible and thus particularly suitable for long-term longitudinal studies. Third, administration of the well-characterized psychotomimetic compounds amphetamine and phencyclidine (PCP) elicited dose-dependent activation patterns that were related to the drugs' particular interactions with the dopaminergic and glutamatergic systems, respectively. In conclusion, perfusion-based phMRI is a robust, reliable and valid quantitative technique suitable for evaluating brain-activation patterns in animal models of CNS diseases.

Contrast-enhanced magnetic resonance angiography (CE-MRA) of intra- and extra-cranial vessels in dogs.

Until recently intra- and extra-cranial vessels in dogs have been imaged using conventional X-ray or digital subtraction angiography. As both of these methods are surgically demanding and involve the use of complex equipment with potential risks for the animal, they are now mainly used in experimental work. In this study, a method for delineating the intra- and extra-cranial vessels of dogs using contrast-enhanced magnetic resonance angiography (CE-MRA) has been examined. The MR images were acquired on a 1.5-T scanner after a bolus injection of gadolinium contrast medium. CE-MRA showed most of the major intra- and extra-cranial arteries and veins as well as most venous sinuses and plexuses of the brain. Difficulties may arise in differentiating between minor arterial and venous vessels as well as in the measurement of vessel diameter. More frequent use of this diagnostic method in clinical cases will indicate whether MRA of the head and brain is of as much use in veterinary medicine as it has become in human medicine. There is certainly potential value in detecting rare conditions in animals such as aneurysms and vascular malformations, as well as in examining vessels feeding intracranial masses and the investigation of cerebrovascular accidents.

An in vivo magnetic resonance imaging technique for measurement of rat lumbar vertebral body blood perfusion.

The technical feasibility of dynamic contrast-enhanced magnetic resonance imaging (MRI) measurement of rat vertebral blood perfusion using a 1.5 T clinical scanner and a small surface coil was investigated in this study. Nine male 7-month-old Wistar-Kyoto rats were used. Computed tomographic assessment of lumbar vertebral bone mineral density (BMD) and MRI assessment of lumbar vertebral blood perfusion were performed twice with 8 weeks' interval. A 4.7 cm surface coil was used for receiving radiofrequency signal. Gadolinium-DOTA (0.3 mmol/kg) was injected through the tail vein of the rat as a quick bolus and dynamic MRI scan was carried out on the central sagittal plane of the lumbar spine for 8 min with a temporal resolution of 0.6 s. Blood perfusion parameters of wash-in rate, maximum enhancement and wash-out rate were derived from the dynamic MR images. No vertebral body size and vertebral BMD difference was detected between the two time points (P=0.222 and 0.123, respectively). Wash-in rate was 0.105 (+/-0.016)% and 0.111 (+/-0.018)%, maximum enhancement 126.5 (+/-10.6)% and 129.2 (+/-13.4)%, and wash-out rate 0.788 (+/-0.182)% and 0.792 (+/-0.182)% for the two time points. With these parameters, no difference was found between the two time points with a P value of 0.575, 0.889 and 0.754, respectively. We conclude that dynamic contrast-enhanced MRI measurement of rat vertebral blood perfusion using a 1.5 T clinical scanner and a small surface coil is feasible and reliable. This technique offers a non-invasive means to probe vertebral blood perfusion changes associated with rat disease models.

Vascular ultrasound studies for the non-invasive assessment of vascular flow and patency in experimental surgery in the pig.

Vascular ultrasound is a reliable non-invasive tool used for the routine assessment of vascular flow and patency in human recipients. We describe the use at three different time points (immediately, 1 week and 4 weeks postsurgery) of ultrasound studies and its validation by angiographic studies in 37 swine undergoing carotid graft replacement. We calculated predictive values (>92%), sensitivity (>85%) and specificity (>92%) with high results at all time points. Ultrasound appeared as an accessible non-invasive technique, providing rapid, safe, repeatable and reliable results. It is an excellent alternative to angiography, avoiding risks inherent to invasive methods and therefore contributing to animal welfare.

Diffusion-weighted and perfusion-weighted magnetic resonance imaging of the prostate gland of healthy adult dogs.

OBJECTIVE: To describe diffusion and perfusion characteristics of the prostate gland of healthy sexually intact adult dogs as determined by use of diffusion-weighted and perfusion-weighted MRI. ANIMALS: 12 healthy sexually intact adult Beagles. PROCEDURES: Ultrasonography of the prostate gland was performed. Subsequently, each dog was anesthetized, and morphological, diffusion-weighted, and perfusion-weighted MRI of the caudal aspect of the abdomen was performed. The apparent diffusion coefficient was calculated for the prostate gland parenchyma in diffusion-weighted MRI images in the central ventral and peripheral dorsal areas. Perfusion variables were examined in multiple regions of interest (ROIs) in the ventral and dorsal areas of the prostate gland and in the gluteal musculature. Signal intensity was determined, and a time-intensity curve was generated for each ROI. RESULTS: Results of ultrasonographic examination of the prostate gland revealed no abnormalities for any dog. Median apparent diffusion coefficient of the prostate gland was 1.51 × 10-3 mm2/s (range, 1.04 × 10-3 mm2/s to 1.86 × 10-3 mm2/s). Perfusion-weighted MRI variables for the ROIs differed between the prostate gland parenchyma and gluteal musculature. CONCLUSIONS AND CLINICAL RELEVANCE: Results provided baseline information about diffusion and perfusion characteristics of the prostate gland in healthy sexually intact adult dogs. Additional studies with dogs of various ages and breeds, with and without abnormalities of the prostate gland, will be necessary to validate these findings and investigate clinical applications.

Perfusion-weighted and diffusion-weighted magnetic resonance imaging of the liver, spleen, and kidneys of healthy adult male cats.

OBJECTIVE To describe perfusion and diffusion characteristics of the liver, spleen, and kidneys of healthy adult male cats as determined by morphological, perfusion-weighted, and diffusion-weighted MRI. ANIMALS 12 healthy adult male cats. PROCEDURES Each cat was anesthetized. Morphological, perfusion-weighted, and diffusion-weighted MRI of the cranial aspect of the abdomen was performed. A region of interest (ROI) was established on MRI images for each of the following structures: liver, spleen, cortex and medulla of both kidneys, and skeletal muscle. Signal intensity was determined, and a time-intensity curve was generated for each ROI. The apparent diffusion coefficient (ADC) was calculated for the hepatic and splenic parenchyma and kidneys on diffusion-weighted MRI images. The normalized ADC for the liver was calculated as the ratio of the ADC for the hepatic parenchyma to the ADC for the splenic parenchyma. RESULTS Perfusion-weighted MRI variables differed among the 5 ROIs. Median ADC of the hepatic parenchyma was 1.38 × 10-3 mm2/s, and mean ± SD normalized ADC for the liver was 1.86 ± 0.18. Median ADC of the renal cortex and renal medulla was 1.65 × 10-3 mm2/s and 1.93 × 10-3 mm2/s, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Results provided preliminary baseline information about the diffusion and perfusion characteristics of structures in the cranial aspect of the abdomen of healthy adult male cats. Additional studies of cats of different sex and age groups as well as with and without cranial abdominal pathological conditions are necessary to validate and refine these findings.

Myoclonus and hypercalcemia in a dog with poorly differentiated lymphoproliferative neoplasia.

A 1-year, 8-month-old Rhodesian Ridgeback was presented with obtundation, ambulatory tetraparesis, and myoclonus. Initial clinical findings included ionized hypercalcemia with an apparent marked increase in parathyroid hormone, thrombocytopenia, and nonregenerative anemia. Low numbers of circulating atypical cells were noted on blood film evaluation. Brain magnetic resonance imaging identified an extra-axial contrast enhancing subtentorial lesion, and cerebrospinal fluid (CSF) analysis documented a marked atypical lymphocytic pleocytosis. Flow cytometry performed on the CSF demonstrated expression of only CD45, CD90, and MHC class II, with Pax5 positivity on subsequent immunohistochemistry. The final diagnosis was of B-cell lymphoblastic lymphoma or acute leukemia, given the distribution of disease and the presence of significant bone marrow infiltration alongside an aggressive clinical course. The unusual immunophenotype of the neoplastic cells and hypercalcemia presented antemortem diagnostic challenges, highlighting the need for a multidisciplinary approach and caution in the interpretation of clinical abnormalities in cases with multiple comorbidities.

Use of three-dimensional time-of-flight magnetic resonance angiography at 1.5 Tesla to evaluate the intracranial arteries of 39 dogs with idiopathic epilepsy.

OBJECTIVE: 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. ANIMALS: 39 dogs with idiopathic epilepsy. PROCEDURES: 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. RESULTS: 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).

Anatomical variations in the circle of Willis in canines.

The circle of Willis (CW) supplies blood to the brain. In humans, anatomical variations in the CW are an important risk factor for transient ischaemic attack and stroke. In canines, anatomical variations in the CW have not been reported. The aim of this study was to determine anatomical variations in the CW in dogs by magnetic resonance angiography. Normal configuration of the CW was observed in 82%, aplasia of the precommunicating segment of the rostral cerebral artery was observed in 14%, and aplasia of the rostral communicating artery was observed in 4% of dogs included in the study.

Comparison of left and right ventricular stroke volume of dogs calculated on the basis of morphology and blood flow determined by use of cardiac magnetic resonance imaging.

OBJECTIVE To compare stroke volume (SV) calculated on the basis of cardiac morphology determined by MRI and results of phase-contrast angiography (PCA) of ventricular inflow and outflow in dogs. ANIMALS 10 healthy Beagles. PROCEDURES Cardiac MRI was performed twice on each Beagle. Cine gradient echo sequences of both ventricles in short-axis planes were used for morphological quantification of SVs by assessment of myocardial contours. From the long-axis plane, SVs in 4-chamber and left ventricular 2-chamber views were acquired at end diastole and end systole. For calculation of SV on the basis of blood flow, PCA was performed for cardiac valves. RESULTS Mean ± SD values for SV quantified on the basis of blood flow were similar in all valves (aortic, 17.8 ± 4.1 mL; pulmonary, 17.2 ± 5.4 mL; mitral, 17.2 ± 3.9 mL; and tricuspid, 16.9 ± 5.1 mL). Morphological quantification of SV in the short-axis plane yielded significant differences between left (13.4 ± 2.7 mL) and right (8.6 ± 2.4 mL) sides. Morphological quantification of left ventricular SV in the long-axis plane (15.2 ± 3.3 mL and 20.7 ± 3.8 mL in the 4- and 2-chamber views) yielded variable results, which differed significantly from values for flow-based quantification, except for values for the morphological 4-chamber view and PCA for the atrioventricular valves, for which no significant differences were identified. CONCLUSIONS AND CLINICAL RELEVANCE In contrast to quantification based on blood flow, calculation on the basis of morphology for the short-axis plane significantly underestimated SV, probably because of through-plane motion and complex right ventricular anatomy.

Interictal diffusion and perfusion magnetic resonance imaging features of cats with familial spontaneous epilepsy.

OBJECTIVE To evaluate the usefulness of diffusion and perfusion MRI of the cerebrum in cats with familial spontaneous epilepsy (FSECs) and identify microstructural and functional deficit zones in affected cats. ANIMALS 19 FSECs and 12 healthy cats. PROCEDURES Diffusion-weighted, diffusion tensor, and perfusion-weighted MRI of the cerebrum were performed during interictal periods in FSECs. Imaging findings were compared between FSECs and control cats. Diffusion (apparent diffusion coefficient and fractional anisotropy) and perfusion (relative cerebral blood volume [rCBV], relative cerebral blood flow [rCBF], and mean transit time) variables were measured bilaterally in the hippocampus, amygdala, thalamus, parietal cortex gray matter, and subcortical white matter. Asymmetry of these variables in each region was also evaluated and compared between FSECs and control cats. RESULTS The apparent diffusion coefficient of the total amygdala of FSECs was significantly higher, compared with that of control cats. The fractional anisotropy of the right side and total hippocampus of FSECs was significantly lower, compared with that of control cats. The left and right sides and total hippocampal rCBV and rCBF were significantly lower in FSECs than in control cats. The rCBV and rCBF of the parietal cortex gray matter in FSECs were significantly lower than in control cats. CONCLUSIONS AND CLINICAL RELEVANCE In FSECs, diffusion and perfusion MRI detected microstructural changes and hypoperfusion (lowered function) in the cerebrum during interictal periods from that of healthy cats. These findings indicated that diffusion and perfusion MRI may be useful for noninvasive evaluation of epileptogenic foci in cats.