COMPUTED TOMOGRAPHIC MEASUREMENT OF THE MAIN PULMONARY ARTERY TO AORTIC DIAMETER RATIO IN HEALTHY DOGS: A COMPARISON TO ECHOCARDIOGRAPHICALLY DERIVED RATIOS.

Indicators of pulmonary hypertension in dogs examined with thoracic computed tomography (CT) are not well established in the veterinary literature. In humans, the main pulmonary artery to aortic diameter ratio (MPA:Ao) measured via CT, has been shown to be more sensitive than echocardiographic variables for predicting presence and severity of pulmonary hypertension, in some cases. In veterinary literature, the MPA:Ao has been determined echocardiographically to have an upper limit of about 1:1. Measurement of this ratio has not been described in dogs using CT. The objectives of this cross-sectional, prospective study were to compare echocardiographic measurement of MPA:Ao with that obtained via CT, determine if measurement of MPA:Ao via CT is repeatable and reproducible, and determine the effect of respiration and contrast administration on the measurement of MPA:Ao via CT. Ten healthy dogs without pulmonary hypertension were anesthetized to undergo thoracic CT using three protocols and echocardiography. The MPA:Ao was measured three times by three observers for each of the three CT protocols and compared to echocardiographic measurements. The mean MPA:Ao measured among all observers and CT protocols was 1.108 ± 0.152 (SD). The effect of CT scan protocol on MPA:Ao significantly differed among the three methods (P = 0.0014), where expiratory scans had lower MPA:Ao than inspiratory scans. The ratio measured on inspiratory CT scans consistently overestimated MPA:Ao when compared to echocardiography (bias = 0.226). Findings did not support the echocardiographically derived upper limit of MPA:Ao as an upper limit for determination of main pulmonary arterial enlargement on CT.

Establishment of optimal scan delay for multi-phase computed tomography using bolus-tracking technique in canine pancreas.

To establish a protocol for a multi-phase computed tomography (CT) of the canine pancreas using the bolus-tracking technique, dynamic scan and multi-phase CT were performed in six normal beagle dogs. The dynamic scan was performed for 60 sec at 1-sec intervals after the injection (4 ml/sec) of a contrast medium, and intervals from aortic enhancement appearance to aortic, pancreatic parenchymal and portal vein peaks were measured. The multi-phase CT with 3 phases was performed three times using a bolus-tracking technique. Scan delays were 0, 15 and 30 in first multi-phase scan; 5, 20 and 35 in second multi-phase scan; and 10, 25 and 40 sec in third multi-phase scan, respectively. Attenuation values and contrast enhancement pattern were analyzed from the aorta, pancreas and portal vein. The intervals from aortic enhancement appearance to aortic, pancreatic parenchymal and portal vein peaks were 3.8 ± 0.7, 8.7 ± 0.9 and 13.3 ± 1.5 sec, respectively. The maximum attenuation values of the aorta, pancreatic parenchyma and portal vein were present at scan sections with no scan delay, a 5-sec delay and a 10-sec delay, respectively. When a multi-phase CT of the canine pancreas is triggered at aortic enhancement appearance using a bolus-tracking technique, the recommended optimal delay times of the arterial and pancreatic parenchymal phases are no scan delay and 5 sec, respectively.

EFFECTS OF TWO CONTRAST INJECTION PROTOCOLS ON FELINE AORTIC AND HEPATIC ENHANCEMENT USING DYNAMIC COMPUTED TOMOGRAPHY.

This prospective study compared aortic and hepatic enhancement achieved using a contrast injection protocol with a fixed rate of 5 ml/s vs. that achieved using a protocol with fixed injection duration of 20 s in eight cats. Cats were assigned into two groups (Group 1, rate 5 ml/s; Group 2, duration 20 s). The dose of contrast was the same in both groups (740 mgI/kg). Regions of interest (ROI) were drawn in the aorta and liver for transverse scans acquired at the hepatic hilus. Time to peak aortic enhancement occurred significantly earlier in Group 1 (M = 11s, SD = 1.63) than in Group 2 (M = 25.5 s, SD = 2.51). Peak aortic enhancement was significantly higher in Group 1 (M = 1906.51 HU, SD = 368.64) than in Group 2 (M = 745.08 HU, SD = 201.84). Duration of aortic enhancement equal to or above 300 HU was statistically longer in Group 2 (M = 24.5 s, SD = 8.39) than in Group 1 (M = 10 s, SD = 1.63). There were no significant differences in time to peak liver enhancement, peak liver enhancement, or duration of hepatic arterial phase between groups. Findings supported the hypothesis that longer injection duration results in a broader bolus geometry with a longer time to peak and a lower peak aortic enhancement in cat. This strong influence of injection duration on timing of aortic enhancement may help future users optimize protocols for CT angiography of the aorta and multiphasic evaluation of the liver, pancreas, and small intestine.

[Multiphasic contrast-enhanced CT: correlation of the peak attenuation in the aorta abdominalis and portal vein with easily detectable clinical parameters]. / Multiphasen-Kontrastcomputertomographie: Korrelation der Anreicherungskurven in Aorta abdominalis und Vena portae mit einfach klinisch messbaren Parametern.

OBJECTIVE: The diagnostic value of a multiphase CT strongly depends on the correct timepoints of analysis. Therefore, we investigated whether the peak attenuation time in the aorta and portal vein are predictable using easily detectable clinical parameters. Regression equations were developed that enable an approximate prediction of these scan times. MATERIAL AND METHODS: Contrast dynamic CT was performed in 39 anaesthetised dogs of different breeds. The heart rate at the onset of the examination, the age and the body weight were documented. The contrast agent Imeron 300® was injected into a cephalic vein at 3 ml/s with 600 mg iodine/kg body weight using an automatic injector and a dynamic axial CT was started at the same time. The peak enhancement time in the aorta (pETA) and portal vein (pETP) were measured. RESULTS: The mean pETA was 24.5 ± 8.6 seconds and the mean pETP was 43.6 ± 13.4 seconds. There was a strong correlation (r = 0.92) between pETA and body weight in combination with the heart rate, and a moderate correlation (r = 0.66) between pETP and body weight in combination with the age. The regression equation was: pETA = 12.23 + 0.61 body weight - 0.07 heart rate. The time between pETA and pETP was 8-24 seconds in 34 animals. CONCLUSION: To plan the arterial peak the authors recommend the use of the established regression equations based on the statistical results or alternatively bolus tracking to plan the arterial peak. When it is planned to examine the portal venous peak, an interscan duration of 8-14 seconds is recommended.

Multidetector computed tomographic angiography evaluation of micropig major systemic vessels for xenotransplantation.

Due primarily to the increasing shortage of allogeneic donor organs, xenotransplantation has become the focus of a growing field of research. Currently, micropigs are the most suitable donor animal for humans. However, no standard method has been developed to evaluate the systemic vascular anatomy of micropigs and standard reference values to aid in the selection of normal healthy animals as potential organ donors are lacking. Using 64-channel multidetector row computed tomographic angiography (MDCTA), we evaluated morphological features of the major systemic vessels in micropigs and compared our results to published human data. The main vasculature of the animals was similar to that of humans, except for the iliac arterial system. However, diameters of the major systemic vessels were significantly different between micropigs and humans. Specifically, the diameter of the aortic arch, abdominal aorta, external iliac artery, and femoral artery, were measured as 1.50 ± 0.07 cm, 0.85 ± 0.06 cm, 0.52 ± 0.05 cm, and 0.48 ± 0.05 cm, respectively, in the micropigs. This MDCTA data for micropig major systemic vessels can be used as standard reference values for xenotransplantation studies. The use of 64-channel MDCTA enables accurate evaluation of the major systemic vasculature in micropigs.

Multidetector computed tomographic angiography evaluation of micropig major systemic vessels for xenotransplantation

Due primarily to the increasing shortage of allogeneic donor organs, xenotransplantation has become the focus of a growing field of research. Currently, micropigs are the most suitable donor animal for humans. However, no standard method has been developed to evaluate the systemic vascular anatomy of micropigs and standard reference values to aid in the selection of normal healthy animals as potential organ donors are lacking. Using 64-channel multidetector row computed tomographic angiography (MDCTA), we evaluated morphological features of the major systemic vessels in micropigs and compared our results to published human data. The main vasculature of the animals was similar to that of humans, except for the iliac arterial system. However, diameters of the major systemic vessels were significantly different between micropigs and humans. Specifically, the diameter of the aortic arch, abdominal aorta, external iliac artery, and femoral artery, were measured as 1.50 +/- 0.07 cm, 0.85 +/- 0.06 cm, 0.52 +/- 0.05 cm, and 0.48 +/- 0.05 cm, respectively, in the micropigs. This MDCTA data for micropig major systemic vessels can be used as standard reference values for xenotransplantation studies. The use of 64-channel MDCTA enables accurate evaluation of the major systemic vasculature in micropigs.

Feline distal aortic thromboembolism: a review of 44 cases (1990-1998).

The clinical case records of 44 cats with distal aortic thromboembolism were reviewed. These detailed 49 separate episodes of thromboembolism. Of the 44 cats, 33 (75%) were neutered males, and 43 (98%) were domestic shorthairs. The mean age was 8.7 years (age range 2-16 years). Evidence of pre-existing heart disease had been noted in 23% of cases. Heart failure was a concurrent diagnosis in 51% of episodes and 36% of these cases survived their thromboembolic episodes. Overall, cats survived 39% of the episodes. Cats died during 28% of the episodes, while 33% of the episodes resulted in the cats being euthanased. The median survival time was 6 months. Seventeen per cent of cats on prophylactic aspirin therapy experienced an episode of re-embolisation. Forty-three per cent of episodes occurred in the spring.

A retrospective study of 100 cases of feline distal aortic thromboembolism: 1977-1993.

The medical records of 100 cats with distal aortic thromboembolism were reviewed. The average age was 7.7 years, with the neutered male being the most common signalment (63%). Evidence of preexisting cardiac disease was noted in 11% of the cases. A murmur or arrhythmia was noted in 57% of the cases on presentation. Frequent laboratory abnormalities included elevations in blood glucose, alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, and creatinine. Radiographic and electrocardiographic abnormalities were common (89% and 85%, respectively). The most frequent, underlying disease was hypertrophic feline cardiomyopathy (58%), with the left atrial size (as measured by M-mode) significantly increased in the majority of cases (mean left atrial-to-aortic ratio, 2.08). The average, long-term survival in the 37% of cases which survived the initial thromboembolic episode was 11.5 months. The remaining cases either died (28%) or were euthanized (35%).

Pulmonary arteriography and hemodynamics during feline heartworm disease. Effect of aspirin.

The ability of aspirin to block arterial disease and thromboembolism of the pulmonary arteries was studied in heartworm-infected cats. Three groups of cats were transplanted with four heartworms per cat and studied. One group of eight cats (aspirin group) received aspirin (97.5 mg, twice a week) for the five-month infection and another group of eight cats served as the nontreated control group (nontreated group). Based upon the results of the first two groups, the third group (adjusted aspirin group) of six cats was studied in which the aspirin dosage was adjusted in order to maintain an inhibition of in vitro platelet aggregation. Cats were studied by nonselective pulmonary arteriograms before heartworm transplantation and by selective arteriograms, aortograms, and pulmonary hemodynamics five months after heartworm transplant. Pulmonary hypertension, (mean pulmonary artery pressures greater than 16 mmHg), was discovered in three cats with one cat in each group. There were no differences in the mean pulmonary artery pressure or vascular resistance between the groups. Many of the arterial diameters for the nontreated and aspirin groups were greater after the five-month infection than before heartworm infection. All of the postinfection caudal arteries were tortuous and had aneurysms. Some of the caudal lung lobes had perfused areas that appeared to have a hypervascular microvasculature. The proportion of obstructed right and left distal caudal pulmonary arteries and the resulting nonperfused area of the caudal lung lobe in the nontreated and aspirin treated groups were each greater than in the adjusted aspirin group.(ABSTRACT TRUNCATED AT 250 WORDS)