Structural and functional changes relevant to maxillary arterial flow observed during computed tomography and nonselective digital subtraction angiography in cats with the mouth closed and opened.

Some cats develop blindness during procedures with mouth gags, which possibly relates to maxillary arterial occlusion by opening the mouth. Our first aim was to use computed tomography (CT) to describe how vascular compression is possible based on morphologic differences between mouth positions. Our second aim was to use nonselective digital subtraction angiography to assess whether opening the mouth induces collateral circulation. Six healthy cats were examined. During CT, the maxillary artery coursed between the angular process of the mandible and the rostrolateral wall of the tympanic bulla. The median distance between these structures was shorter when the mouth was opened (left, 4.3 mm; right, 3.6 mm) vs. closed (left, 6.9 mm; right, 7.1 mm). Additionally, the distance was shorter on the side ipsilateral to the gag (P = 0.03). During nonselective angiography, with the mouth closed, there was strong sequential opacification of the external carotid arteries, maxillary arteries, maxillary retia mirabilia, cerebral arterial circle, and basilar artery. Additionally, there was uniform opacification of the cerebrum and cerebellum. With the mouth opened, opacification of the maxillary arteries (rostral to the angular processes) was reduced in all cats, the cerebral arterial circle and basilar artery had simultaneous opacification in four of six (67%) cats, and the cerebrum had reduced opacification compared to the cerebellum in four of six (67%). In conclusion, the maxillary arteries are situated such that they can be compressed when opening the mouth. Opening the mouth did not consistently induce collateral circulation sufficient to produce comparable cerebral opacification as when the mouth was closed.

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.

Non-selective computed tomography angiography of a vascular ring anomaly in a dog.

Non-selective computed tomography angiography (CTA) is an emerging imaging technique that will have continued application in veterinary medicine because of its short scan time, use of a single, peripheral venous injection and availability of more detailed anatomic information--including 3-dimensional reconstructions. The improved anatomic detail may facilitate veterinary students' learning of complex aortic arch malformations and details relative to the surgical approach. Herein we describe application of its use in a dog with a vascular ring anomaly due to a persistent right fourth aortic arch and left ligamentum arteriosum. Additionally, we compare images with a normal dog.

A high-precision contrast injector for small animal x-ray digital subtraction angiography.

The availability of genetically altered animal models of human disease for basic research has generated great interest in new imaging methodologies. Digital subtraction angiography (DSA) offers an appealing approach to functional imaging in small animals because of the high spatial and temporal resolution, and the ability to visualize and measure blood flow. The micro-injector described here meets crucial performance parameters to ensure optimal vessel enhancement without significantly increasing the total blood volume or producing overlap of enhanced structures. The micro-injector can inject small, reproducible volumes of contrast agent at high flow rates with computer-controlled timing synchronized to cardiopulmonary activity. Iterative bench-top and live animal experiments with both rat and mouse have been conducted to evaluate the performance of this computer-controlled micro-injector, a first demonstration of a new device designed explicitly for the unique requirements of DSA in small animals. Injection protocols were optimized and screened for potential physiological impact. For the optimized protocols, we found that changes in the time-density curves for representative regions of interest in the thorax were due primarily to physiological changes, independent of micro-injector parameters.

Angiografia in vivo para avaliação da vascularização do casco de eqüinos / In vivo angiography for evaluation of equine foot vasculature

A proposta deste trabalho foi estabelecer a angiografia digital palmar como método de avaliação qualitativa in vivo da vascularização distal laminar em eqüinos em posição quadrupedal. Foram realizadas 15 angiografias de eqüinos mestiços, sendo seis machos castrados e nove fêmeas, com idade variando entre seis e oito anos. As angiografias foram realizadas, após bloqueio anestésico perineural do nervo digital palmar lateral ou medial, por meio da aplicação de 20mL de contraste na veia digital palmar lateral ou medial garroteada por atadura elástica e torniquete. Imediatamente depois, foi realizada a primeira exposição radiológica em incidência dorso-palmar. Após a dispersão do contraste, o mesmo procedimento foi realizado com o casco submetido ao tratamento térmico com água aquecida e com água resfriada. Em quatro animais, obteve-se imagem radiopaca, com bordas maldefinidas, de aspecto sombreado, ao redor de cada lâmina dérmica, que foi creditada à vasodilatação ocasionada pelo calor. Quando da vasoconstrição ocasionada pelo tratamento com frio, observou-se redução da imagem radiopaca laminar. Esse aspecto pôde ser comprovado em quatro radiografias, porém não se repetiu em todas as angiografias realizadas. Em sete radiografias, houve falha de preenchimento de contraste, o que inviabilizou a comparação entre tratamentos térmicos, sendo que as radiografias realizadas sem nenhum tratamento térmico possuíam preenchimento de contraste adequado. A angiografia digital em eqüinos mostrou-se um método sensível para evidenciar vasoconstrição e vasodilatação in vivo dentro do estojo córneo, porém inúmeros fatores podem contribuir para o aparecimento de artefatos de técnica, o que inviabiliza a comparação de alterações da perfusão laminar do casco por esse método.

This study was aimed at establishing the palmar digital angiography as an in vivo qualitative method of evaluation the laminar digital vasculature on horses in standing position. Six gelding and nine mares were used in this study, with age going from 6 to 8 years old. After the perineural anesthesia of lateral or medial palmar digital nerve and the surgical preparation an intravenous catheter was fixed to the palmar digital vein, lateral or medial. After performing a simple radiography an elastic bandage and tourniquet was applied to the area. The animal and the RX equipment were adequately positioned and 20mL of contrast were injected, followed by a first radiological exposition in dorsum palmar incidence. In sequence the tourniquet and the elastic bandage were removed for the dissipation of the contrast, keeping the venous access with infusion of isotonic saline solution. The same procedure was performed with the hoof submitted to the thermal treatment with warmed water and cold water. In four animals a radiopaque image, around each dermic lamina with vasodilatation induced by the heat was obtained, with poorly defined edges and blurred aspect. On the other hand, it was observed reduction of the radiopaque laminar image because of the vasoconstriction caused by the treatment with cold water. This fact can be seen only in four radiographies, but it has not being repeated in all angiographies performed. In seven radiographies incomplete contrast filling was observed. For this reason, it was not possible to compare the radiographs performed with no thermal treatment, that have had the appropriate filling of the contrast. The digital angiography in horses was showed to be a sensible method to evidence in vivo vasoconstriction and vasodilatation inside the hoof, however this method cannot be use to analyze alteration in the laminar perfusion because some techniques artefactual.

Optimized radiographic spectra for small animal digital subtraction angiography.

The increasing use of small animals in basic research has spurred interest in new imaging methodologies. Digital subtraction angiography (DSA) offers a particularly appealing approach to functional imaging in the small animal. This study examines the optimal x-ray, molybdenum (Mo) or tungsten (W) target sources, and technique to produce the highest quality small animal functional subtraction angiograms in terms of contrast and signal-difference-to-noise ratio squared (SdNR2). Two limiting conditions were considered-normalization with respect to dose and normalization against tube loading. Image contrast and SdNR2 were simulated using an established x-ray model. DSA images of live rats were taken at two representative tube potentials for the W and Mo sources. Results show that for small animal DSA, the Mo source provides better contrast. However, with digital detectors, SdNR2 is the more relevant figure of merit. The W source operated at kVps >60 achieved a higher SdNR2. The highest SdNR2 was obtained at voltages above 90 kVp. However, operation at the higher potential results in significantly greater dose and tube load and reduced contrast quantization. A reasonable tradeoff can be achieved at tube potentials at the beginning of the performance plateau, around 70 kVp, where the relative gain in SdNR2 is the greatest.

Use of percutaneous arterial embolization for treatment of intractable epistaxis in three dogs.

Intractable epistaxis can be a life-threatening condition. Surgical options are presently limited to ligation of the carotid artery. Extensive collateralization develops after occlusion of the carotid artery, so the benefits are likely only transient and the procedure cannot be repeated. In humans, endovascular treatment avoids many of the complications associated with surgery and has a lower recurrence rate than that associated with ligation of the internal maxillary artery. In 3 dogs with intractable epistaxis, embolization of the terminal portion of the maxillary artery was performed with polyvinyl alcohol particles and contrast slurry. Minor, self-limiting bleeding recurred in 1 dog 8 months after surgery; 2 dogs had no important complications or recurrence within a minimum 10-month follow-up time. Results indicate the feasibility of embolization of the terminal branches of the maxillary artery to control epistaxis in dogs that do not require surgery and as a useful adjunctive procedure prior to rhinotomy.

Digital angiography of the feet of horses.

OBJECTIVE: To describe the vascular anatomy of the palmar digital artery and its major branches in the equine foot and to quantify the diameter of these vessels by use of digital angiograms. Sample Population-6 thoracic limbs obtained from 6 horses. PROCEDURE: Distal portions of each limb were perfused with aerated Krebs-Henseleit solution. Digital angiograms were acquired in standing and lateral recumbent positions, following an intra-arterial injection of iopamidol. Select vessels were measured on radiographic views, and values were corrected for magnification. RESULTS: The palmar digital artery tapered from 2.28 mm at the coronary region to 1.61 mm at the entrance to the solar canal, and the major arterial branches ranged in diameter from 0.71 to 1.42 mm in the standing position. CONCLUSIONS AND CLINICAL RELEVANCE: Digital angiography is useful for imaging small vessels, but penumbra limits the image resolution of the macrovasculature of the foot. The palmarodorsal projection is more useful for evaluation of the terminal arch and solar branches, but 2 projections are necessary for a thorough examination of the foot. Image magnification, position of horse, and vascular response to contrast medium must be considered in the quantitative assessment of vessel diameter. Digital angiography may be performed in clinical cases and research models for examination of vascular perfusion of the distal portion of the limb.

Characterization of the renal portal system of the common green iguana (Iguana iguana) by digital subtraction imaging.

Digital subtraction angiography was used to map the venous blood flow from the pelvic limb and the tail in the common green iguana (Iguana iguana). The majority of blood returning from the pelvic limb bypassed the kidney and entered the general circulation, whereas venous blood flow from the tail entered the renal portal circulation. No evidence was found of a renal portal valve.

Anatomic and surgical approach to the ethmoidal nerve and parasympathetic innervation of the nasal and cerebral circulation in sheep.

OBJECTIVE: To describe an anatomic and surgical approach to the efferent parasympathetic branches of the pterygopalatine ganglia in sheep, with particular reference to the ethmoidal nerve and innervation of nasal and cerebral blood vessels. ANIMALS: 12 adult sheep used for monolateral (n = 7) or bilateral (n = 5) ethmoidal neurectomy; 2 sheep used for angiography (1 live sheep for digital subtraction angiography, 1 embalmed cadaver for injection studies); and 5 embalmed cadavers, 4 frozen specimens, and 2 dry skulls used for dissection, x-rays, and computed tomographic (CT) or magnetic resonance (MR) scans. PROCEDURE: Transverse (coronal) MR scans, transverse, sagittal, and dorsal CT scans, radiography, angiography, photographic images, and dissections of embalmed material were used to study the topographic anatomy of the temporal and pterygopalatine fossae of the head. RESULTS: Images were stored, then compared with photographs of frozen sections from the same or a similar specimen to plan a surgical approach to the ethmoidal nerve. Mono- and bilateral experimental ethmoidal neurectomies were performed, allowing characterization of a safe and reliable method. The series of pterygopalatine ganglia typical of this species was localized, dissected, and analyzed for topographic relations. CONCLUSIONS: From the results, a new approach to the efferent branches of the pterygopalatine ganglia (ethmoidal nerve) for experimental parasympathectomy of the cerebral and nasal circle is proposed. This experimental approach could be used for studies involving thermoregulation of the face, and in experimental control of blood flow in the nasal cavity and rostral part of the brain.

Intraoperative use of subtraction angiography and an ultrasonic aspirator to improve identification and isolation of an intrahepatic portosystemic shunt in a dog.

Mesenteric portography, using a C-arm fluoroscope equipped with digital subtraction capability, was performed intraoperatively to locate a single, intrahepatic portocaval shunt. An ultrasonic aspirator was used to isolate the shunt, which was ligated completely. Typical portal venous arborization was seen on postligation intraoperative mesenteric portography. Subtraction angiography used intraoperatively and dissection with the ultrasonic aspirator improve the surgeon's ability to localize and isolate intrahepatic portocaval shunts and can reduce surgical time. Film development and patient repositioning and transport, before and after shunt ligation, are not necessary when mesenteric portography is performed intraoperatively, using a C-arm fluoroscope and digital subtraction. Dissection around intrahepatic portocaval shunts is facilitated by the ultrasonic aspirator, which selectively fractures and suctions tissue from around the shunt. Hemorrhage is decreased, because hepatic ductules and small blood vessels are left intact.