Comparison of bone subtraction CT angiography with standard CT angiography for evaluating circle of Willis in normal dogs.

BACKGROUND: Bone subtraction computed tomography angiography (BSCTA) is a useful alternative technique for improving visualization of vessels surrounded by skull bone. However, no studies have compared computed tomography angiography (CTA) and BSCTA for improving the visibility of canine cerebral blood vessels. OBJECTIVES: To evaluate the potential benefit of BSCTA for better delineation of brain arteries of the circle of Willis (CoW) in dogs by comparing BSCTA with non-subtraction computed tomography angiography (NSCTA). METHODS: Brain CTA was performed for nine healthy beagle dogs using a bolus tracking method with saline flushing. A total dose of 600 mgI/kg of contrast agent with an iodine content of 370 mgI/mL was injected at a rate of 4 ml/s. Bone removal was achieved automatically by subtracting non-enhanced computed tomography (CT) data from contrast CT data. Five main intracranial arteries of the CoW were analyzed and graded on a scale of five for qualitative evaluation. RESULTS: Scores of basilar artery, middle cerebral artery, and rostral cerebral artery in the BSCTA group were significantly higher than those in the NSCTA group (p = 0.001, p = 0.020, and p < 0.0001, respectively). Scores of rostral cerebellar artery (RcA) and caudal cerebral artery (CCA) did not differ significantly between the two groups. However, scores of RcA and CCA in the BSCTA group were higher than those in the NSCTA group. CONCLUSIONS: BSCTA improved visualization of intracranial arteries of the CoW with close contact to bone. Thus, it should be recommended as a routine scan method in dogs suspected of having brain vessel disease.

Dynamic cone beam CT angiography of carotid and cerebral arteries using canine model.

PURPOSE: This research is designed to develop and evaluate a flat-panel detector-based dynamic cone beam CT system for dynamic angiography imaging, which is able to provide both dynamic functional information and dynamic anatomic information from one multirevolution cone beam CT scan. METHODS: A dynamic cone beam CT scan acquired projections over four revolutions within a time window of 40 s after contrast agent injection through a femoral vein to cover the entire wash-in and wash-out phases. A dynamic cone beam CT reconstruction algorithm was utilized and a novel recovery method was developed to correct the time-enhancement curve of contrast flow. From the same data set, both projection-based subtraction and reconstruction-based subtraction approaches were utilized and compared to remove the background tissues and visualize the 3D vascular structure to provide the dynamic anatomic information. RESULTS: Through computer simulations, the new recovery algorithm for dynamic time-enhancement curves was optimized and showed excellent accuracy to recover the actual contrast flow. Canine model experiments also indicated that the recovered time-enhancement curves from dynamic cone beam CT imaging agreed well with that of an IV-digital subtraction angiography (DSA) study. The dynamic vascular structures reconstructed using both projection-based subtraction and reconstruction-based subtraction were almost identical as the differences between them were comparable to the background noise level. At the enhancement peak, all the major carotid and cerebral arteries and the Circle of Willis could be clearly observed. CONCLUSIONS: The proposed dynamic cone beam CT approach can accurately recover the actual contrast flow, and dynamic anatomic imaging can be obtained with high isotropic 3D resolution. This approach is promising for diagnosis and treatment planning of vascular diseases and strokes.

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.

In vivo X-ray angiography in the mouse brain using synchrotron radiation.

BACKGROUND AND PURPOSE: We, for the first time, performed in vivo x-ray angiography in the mouse brain using SPring-8, a third-generation synchrotron radiation facility. METHODS: A thin PE-50 tube was placed in the unilateral external carotid artery in adult male C57BL/6J mice. While maintaining the blood flow in the internal carotid artery, 33 muL of contrast agent was injected and then selective angiography of the hemisphere was performed. RESULTS: The average diameters of cerebral artery were as follows: 142.5+/-7.90 microm in middle cerebral artery, 138.3+/-9.35 microm in anterior cerebral artery, 120.5+/-5.53 microm in posterior cerebral artery, and 162.6+/-10.87 microm in internal carotid artery (n=5). To demonstrate the changes in diameter, we induced hypercapnia and detected the dilatation of the vessels between 121% and 124% of the original diameters (n=5). We also repeated angiography in the mice before and after intracarotid injection of vasodilatation drugs papaverine hydrochloride, ATP disodium, and fasudil hydrochloride hydrate and demonstrated the chronological changes in the diameters in each artery at 1, 5, 15, and 30 minutes after injection (n=1 for each drug). CONCLUSIONS: Using only a minimum volume of the contrast agent, synchrotron radiation enables us to study x-ray angiography in the mouse brain. The morphology of the vessels can be clearly observed under physiological conditions. The diameters and their changes can also be successfully studied in vivo.

Controlled release of a nitric oxide donor for the prevention of delayed cerebral vasospasm following experimental subarachnoid hemorrhage in nonhuman primates.

OBJECT: Results of prior studies in rats and rabbits show that the alteration of vasomotor tone in vasospasm following periadventitial blood exposure may be reversed, at least in part, by the administration of compounds releasing nitric oxide (NO). The authors have now generalized this finding to nonhuman primates. METHODS: Ten cynomolgus monkeys underwent cerebral angiography before and 7 days following the induction of subarachnoid hemorrhage (SAH) by the placement of 2 to 3 ml clotted autologous blood around the supraclinoid carotid, proximal anterior cerebral, and proximal middle cerebral arteries. An ethylene vinyl acetate copolymer, either blank (five animals) or containing 20% w/w (Z)-1-[2-(2-aminoethyl)-N-(2-aminoethyl)amino]diazen-1-ium-1,2-diolate (DETA/NO, 4.3 mg/kg; five animals) was placed adjacent to the vessels at the time of surgery. Animals were killed on Day 7 post-SAH following repeated cerebral angiography. The mean percentage of control vascular areal fraction was calculated from angiograms. Cerebral vessels were sectioned and the mean percentage of lumen patency was calculated. One animal that had received the DETA/NO polymer died prior to repeated angiography. In the remaining animals, DETA/NO caused a significant decrease in vasospasm compared with controls, according to both angiographic (84.8 +/- 8.6 compared with 56.6 +/- 5.2%, respectively, p < 0.05) and histological studies (internal carotid artery 99.3 +/- 1.8 compared with 60.1 +/- 4.4%, respectively, p < 0.001; middle cerebral artery 98.4 +/- 3 compared with 56.1 +/- 3.7%, respectively, p < 0.001; and anterior cerebral artery 89.2 +/- 8.5 compared with 55.8 +/- 6.3%, respectively, p < 0.05). CONCLUSIONS: The controlled release of DETA/NO is effective in preventing delayed cerebral vasospasm in an SAH model in nonhuman primates. The death of one animal in the treatment group indicates that the present dosage is at the threshold between therapeutic efficacy and toxicity.

Effects of ionic and nonionic contrast media on cardiohemodynamics and quality of radiographic image during canine angiography.

Cardiovascular responses and radiographic image quality during cerebral angiography, aortofemoral angiography and left ventriculography with nonionic ioxilan, iohexol or iopamidol were compared with those of ionic sodium meglumine diatrizoate in pentobarbital anesthetized dogs. Injection of all contrast media caused cardiovascular changes to a greater or lesser degree, e.g., hypotension, bradycardia, tachycardia, a decrease in left ventricular pressure (LVP) and its first derivative (dP/dt), and prolongation of the P-Q and Q-T intervals. Ionic diatrizoate had a greater effect on cardiovascular parameters than nonionic contrast media during angiography in all areas. Moreover, diatrizoate produced cardiac arrhythmias and prominent changes in blood rheology concerned with blood viscosity and deformability of the erythrocyte. The cause of various effects of contrast media seemed to lie mainly in osmolality, viscosity and partially ionic additives. The radiographic image quality of all of the contrast media used was similar, but nonionic ioxilan and iohexol with lower iodine content and low osmolality gave better radio opacity than ionic diatrizoate in cerebral angiography. These results suggested that nonionic contrast media should be recommended as a diagnostic tool for both animals and human patients in poor health.

Selected contrast studies. Portal venography and cerebral angiography.

Portography is the most commonly used technique for demonstrating portal venous anatomy and abnormal communications between the portal and systemic venous systems. This article reviews normal anatomy, anomalies, and radiology of the portal venous system. Also included is a discussion of cerebral angiography, which is mainly used in the diagnosis of space-occupying lesions of the brain.

Carotid and cerebral angiography in the horse.

Carotid and cerebral angiography has been found to be a relatively simple technique to carry out in the horse. At most it involves a cutdown approach to the carotid artery, followed by catheterisation of the artery and selective catheterisation, if necessary, of one of its three branches. The technique can be carried out with standard equipment normally available within equine hospital facilities. The authors have employed angiography as a routine aid to diagnosis over the past nine years, without encountering any serious complications or adverse reactions. Carotid angiography has been especially valuable in the investigation of horses with guttural pouch mycosis. The technique has permitted the presence of aneurysms to be detected in many cases and significant vascular abnormalities in four cases. This information is valuable for the surgical treatment of horses with guttural pouch mycosis by ligation of the appropriate artery. Other indications for the use of carotid angiography include the investigation of ethmoidal haematoma, idiopathic Horner's syndrome, neoplasia of the head, venous aneurysms and arterial aneurysms in sites not associated with the guttural pouch. There are fewer occasions for the use of cerebral angiography in the horse, but it is indicated as an aid to the differential diagnosis of some abnormalities of the central nervous system.

Cerebral angiography of the dog.

Cerebral angiography of the dog performed in the radiology research laboratory is used to demonstrate the results of surgical and imaging research for which the canine model is used. This article describes the catheterization and radiographic techniques of a cerebral angiogram performed in the evaluation of a canine model being developed for use in a study of cerebral aneurysms.

Comparison of digital subtraction angiography, micro-computed tomography angiography and magnetic resonance angiography in the assessment of the cerebrovascular system in live mice.

PURPOSE: Mice are often used as small animal models of brain ischemia, venous thrombosis, or vasospasm. This article aimed at providing an overview of the currently available methodologies for in vivo imaging of the murine cerebrovasculature and comparing the capabilities and limitations of the different methods. METHODS: Micro-computed tomography angiography (CTA) was performed during intra-arterial and intravenous administration of a contrast agent bolus. Digital subtraction angiography (DSA) was performed during intra-arterial administration of contrast agent using the micro-CT scanner. Time-of-flight (ToF) magnetic resonance (MR) angiography was performed using a small animal scanner (9.4 T) equipped with a cryogenic transceive quadrature coil. Datasets were compared for scan time, contrast-to-noise ratio (CNR), temporal and spatial resolution, radiation dose, contrast agent dose and detailed recognition of cerebrovascular structures. RESULTS: Highest spatial resolution was achieved using micro-CTA (16 x 16 x 16 µm) and DSA (14 x 14 µm). Compared to micro-CTA (20-40 s) and ToF-MRA (57 min), DSA provided highest temporal resolutions (30 fps) allowing analyses of the cerebrovascular blood flow. Highest mean CNR was reached using ToF-MRA (50.7 ± 15.0), while CNR of micro-CTA depended on the intra-arterial (19.0 ± 1.0) and intravenous (1.3 ± 0.4) use of agents. The CNR of DSA was 10.0 ± 1.8. CONCLUSIONS: The use of dedicated small animal scanners allows cerebrovascular imaging in live animals as small as mice. As each of the methods analyzed has its advantages and limitations, choosing the best suited imaging modality for a defined question is of great importance. By this means the aforementioned methods offer a great potential for future projects in preclinical cerebrovascular research including ischemic stroke or vasospasm.

Potential of optical microangiography to monitor cerebral blood perfusion and vascular plasticity following traumatic brain injury in mice in vivo.

Optical microanglography (OMAG) is a recently developed imaging modality capable of volumetric imaging of dynamic blood perfusion, down to capillary level resolution, with an imaging depth up to 2.00 mm beneath the tissue surface. We report the use of OMAG to monitor the cerebral blood flow (CBF) over the cortex of mouse brain upon traumatic brain injury (TBI), with the cranium left intact, for a period of two weeks on the same animal. We show the ability of OMAG to repeatedly image 3-D cerebral vasculatures during pre- and post-traumatic phases, and to visualize the changes of regulated CBF and the vascular plasticity after TBI. The results indicate the potential of OMAG to explore the mechanism involved in the rehabilitation of TBI.

Animal model for cerebral arteriovenous malformation.

BACKGROUND: The present study was conducted to establish an animal model for the investigation of the pathophysiology and haemodynamics of cerebral arteriovenous malformation (AVM) but also to assess therapeutic aspects. METHOD: For anatomic and haemodynamic reasons, dogs were chosen as the animal model. An arteriovenous fistula was created by interposing a segment of the superficial temporal artery between one of the main branches of the middle cerebral artery and the dorsal sagittal sinus. A temporal muscle graft supplied by this artery was implanted intracerebrally in the ischaemic area. FINDINGS: The angiographic and histopathologic findings obtained in the animal model are comparable with the situation found in intracerebral AVM in humans. INTERPRETATION: The animal model of intracerebral AVM established in this study allows for further investigation of the pathophysiology and dynamics of this disorder. It may help to develop better therapeutic options and thus improve the prognosis of affected patients.

Intraoperative thermal artery imaging of an EC-IC bypass in beagles with infrared camera with detectable wave-length band of 7-14 microm: possibilities as novel blood flow monitoring system.

OBJECTIVE: In the past, the usefulness of thermal arterial imaging during coronary bypass surgery using an infrared camera has been reported by several investigators. The goal of this study is to apply this novel imaging system for intraoperative arterial imaging, as well as to develop new utilizations for a neurosurgical procedure. MATERIALS: We have attempted real-time imaging of anastomotic and flow status in an external carotid-internal carotid artery (EC-IC) bypass surgery using a new-generation infrared camera (IRIS IV thermographic imaging system) in beagles. No contrast medium or radiation was used to obtain the images. The detectable wave-length band of the infrared lens was 7-14 microm. After completion of bypass monitoring, an additional teflon tube was inserted into a branch of the STA to inject physiological saline of different temperatures to see the changes in cortical images. RESULTS: Anastomotic and flow status were clearly visualized throughout the operation without local surface cooling, which had been an inevitable procedure in coronary imaging to make a pronounced temperature difference between artery and adjacent tissue. In addition, cortical flow territory was visualized after injection of either cold or warm physiologic saline into the artery from an additionally inserted teflon tube into a branch of STA via bypass artery. CONCLUSION: From the present experience, it is considered that infrared imaging using a detectable wave length band of 7-14 microm may be applicable to a wide variety of near surface lesions, providing a non-invasive functional angiography.