Shimbo G, Karatsu K, Miyabayashi T.
Introduction/Purpose: On magnetic resonance imaging (MRI), contrast enhancement of the spinal cord has been associated with spinal cord infarction and compressive myelomalacia, most likely due to the disruption of the blood-spinal cord barrier (BSCB). However, availability of MRI is still limited. Recently, multiple-detector computed tomography (MDCT) is widely available. Yet, a contrast enhancement pattern of the canine spinal cord on MDCT has not been well studied. The purpose of this study was to evaluate the contrast enhancement pattern of the lumber spinal cord using dynamic CT.
Methods: Five clinically normal dachshunds (4-7 years of age and weighing 4.1-6.1 kg) were used. The dogs were anesthetized and positioned in a dorsal recumbency. After imaging a thoracolumbar area using a 16-slice multiple-detector CT unit (Hitachi Medico Co Ltd., Tokyo, Japan), dynamic CT images (slice thickness of 5 mm; 0.625mmx8) were obtained for 120 seconds at the level of L1-2 intervertebral disk. lopamidol (600 mgl/kg , injection duration of 6 sec) was injected intravenously, using a power injector. Regions of interest (ROI) were made manually centering the abdominal aorta and spinal cord, and CT numbers were recorded in each region. The contrast enhancement pattern was evalua ted.
Results: The contrast enhancement of the aorta occurred at 7 to 9 sec after contrast injection. The average CT numbers of the spinal cord within the ROI increased at median of 15 (7-15) sec, and the maximal enhancement effect was seen at median of 19 (11-21) sec. The duration of mild enhancement lasted for median of 8 (4-14) sec. After the peak enhancement, the baseline CT numbers were lower than the ones measured prior to contrast enhancement. During this period, both kidneys were markedly contrast enhanced. The maximal enhancement ratio of the spinal cord was 15.7 (8.1-24.0) %.
Discussion/Conclusion: In the present study, there is one dog that did not show a clear peak of contrast enhancement. There is no clear explanation, but this dog had duplicated caudal vena cava from the level of renal vein. There may be a different arterial blood flow pattern to the spinal cord in this dog.
We hypothesize that the peak enhancement rate and duration will increase in cases of spinal cord infarct and myelomalacia in association with acute intervertebral disk protrusion. Experimentally in rats, acute spinal cord trauma caused decreased blood flow and increased permeability, suggesting an abnormal contrast enhancement pattern . In the present study, although the contrast enhancement effect of the spinal cord was minimal in neurologically normal dachshunds, we have established the contrast enhancement pattern of the spinal cord. We will continue to study the usefulness of contrast MDCT in clinically affected dachshunds with acute intervertebral disk disease.