Visualization of the Adamkiewicz Artery by IV-CTA in Dual Power Mode
Yoshiyuki Mizutani, MD* and Tomoko Fujihara**
*Department of Radiology, Sakakibara Heart Institute, Tokyo, Japan
**Application Department CT Team, Customer Service Division, Siemens-Asahi Medical Technologies, Tokyo, Japan | 2010-08-05
A 75-year-old female was referred to the radiology department of Sakakibara Heart Institute Radiology Department before treatment of her thoracic descending aortic aneurysm (TAA) to determine where her Adamkiewicz artery originated. The patient was scanned with Dual Source CT in Dual Power mode.
At the referring hospital, the patient had been diagnosed with TAA (descending aorta of 5.6 cm diameter) by computed tomography and echography. A right coronary artery (RCA) stenosis was also diagnosed by conventional angiography. She was referred to Sakakibara Heart Institute for surgical vessel replacement and coronary artery bypass grafting with saphenous vein graft to RCA.
TAA was clearly seen as expected on the Dual Source CT images. An artery originating from lumbar artery was detected, bifurcating from the aorta at the upper level of the 4th lumbar vertebra, entering into the spinal canal from the intervertebral foramen between the 4th and 5th lumbar vertebrae and running along the spinal cord on the ventral side up to the lower level of the 12th thoracic vertebra where it changed direction, forming a hairpin shaped structure. It connected into the anterior spinal artery. According to these characteristics, it was identified as an Adamkiewicz artery.
The true lumen of the aorta was highly enhanced reaching a CT value of 745.7 ± 14.5 HU at the level between the 4th and 5th lumbar vertebrae whereas the Adamkiewicz artery reached a maximum CT value of only 140 HU.
The course of the Adamkiewicz artery needed to be determined before surgery for TAA repair to ensure that it is not damaged during surgery and to reduce the risk of post-operative paraplegia. However, visualizing the Adamkiewicz artery with intravenous (IV) CTA is a challenging task as injection and scan protocols need to be tailored to the location and size of this artery. Since the Adamkiewicz artery is a tiny vessel, a fair amount of contrast media needs to be injected at reasonably high rates to ensure that this tiny vessel is enhanced. In addition, since the Adamkiewicz artery runs partially inside the spinal canal, enough dose needs to be applied to achieve a high signal-to-noise ratio (S/N) in an area surrounded by bones.
Dual Source CT in the dual power mode combines the power of two X-ray tubes and two generators and can therefore provide twice as much X-ray output as a single source CT at the same pitch. As a result, areas that need additional dose can be scanned at high scan speed and appropriate tube current for a high S/N. The high scan speed was essential for visualizing the Adamkiewicz artery, since it allowed waiting several seconds after enhancement of the aorta until the small arteries were enhanced, then quickly scanning over the required long scan range while the small arteries were still enhanced.
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