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13 March 2006 Subtraction computed tomographic angiography: use of pre-contrast images for calcification removal
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Arterial stenoses may be obscured by calcified atherosclerotic plaque in computed tomographic angiography (CTA). A technique of subtraction computed tomographic angiography (sCTA) for calcification removal is proposed and evaluated in a preliminary manner. In the proposed sCTA method, the examination includes a pre-contrast computed tomogram (pcCT) and a CTA. The pcCT is performed using the CTA scan protocol. Subtraction of the registered pcCT from the CTA is performed after calcifications in the pcCT are registered to the CTA using a piecewise-rigid transformation model. The registration is based on a maximum-cancellation cost-function. Points at the boundary of the artery in the CTA are given a greater weight in the cost function than those towards the center of the artery. sCTA was evaluated using a calcified-artery phantom whose dimensions approximate those of the superficial femoral artery. The phantom represented both calcified plaque surrounding stenotic segments of the artery. pcCT and CTA's were obtained on a 4-multidetector-row CT system with 1.25-mm slice thickness and 0.7-mm in-plane resolution. The phantom was slightly displaced between the pcCT and the CTA. sCTA closely resembled a gold-standard image of the phantom that was obtained with the calcification material removed. The sCTA accurately demonstrated the degree of stenosis and artifacts in the sCTA were minimal. This study demonstrates in a preliminary manner that sCTA is feasible.
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Peter J. Yim and John L. Nosher "Subtraction computed tomographic angiography: use of pre-contrast images for calcification removal", Proc. SPIE 6143, Medical Imaging 2006: Physiology, Function, and Structure from Medical Images, 61432L (13 March 2006);

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