Kazumasa Arakita

Accurate registration of coronary arteries for volumetric CT digital subtraction angiography

In the diagnosis of coronary artery disease with coronary computed tomography angiography, accurate evaluation remains challenging in the presence of calcifications or stents. Volumetric CT Digital Subtraction Angiography is a novel method that may become a powerful tool to overcome these limitations. However, precise registration of structures is essential, as even small misalignments can produce striking and disruptive bright and dark artefacts. Moreover, for clinical acceptance, the tool should require minimal user interaction and fast turnaround, thereby raising several challenges. In this paper we address the problem with a registration method based on a global non- rigid step, followed by local rigid refinement. In our quantitative analysis based on 10 datasets, each consisting of a pair of pre- and post-contrast scans of the same patient, we achieve an average Target Registration Error of 0.45 mm. Runtimes are less than 90 seconds for the global step, while each local refinement takes less than 15 seconds to run. Initial clinical evaluation shows good results in cases of moderate calcification, and indicates that around 50% of severely calcified and previously non-interpretable cases have been made interpretable by application of our method.

Accurate, fully-automated registration of coronary arteries for volumetric CT digital subtraction angiography

Diagnosis of coronary artery disease with Coronary Computed Tomography Angiography (CCTA) is complicated by the presence of signi cant calci cation or stents. Volumetric CT Digital Subtraction Angiography (CTDSA) has recently been shown to be e ective at overcoming these limitations. Precise registration of structures is essential as any misalignment can produce artifacts potentially inhibiting clinical interpretation of the data. The fully-automated registration method described in this paper addresses the problem by combining a dense deformation eld with rigid-body transformations where calci cations/stents are present. The method contains non-rigid and rigid components. Non-rigid registration recovers the majority of motion artifacts and produces a dense deformation eld valid over the entire scan domain. Discrete domains are identi ed in which rigid registrations very accurately align each calci cation/stent. These rigid-body transformations are combined within the immediate area of the deformation eld using a distance transform to minimize distortion of the surrounding tissue. A recent interim analysis of a clinical feasibility study evaluated reader con dence and diagnostic accuracy in conventional CCTA and CTDSA registered using this method. Conventional invasive coronary angiography was used as the reference. The study included 27 patients scanned with a second-generation 320-row CT detector in which 41 lesions were identi ed. Compared to conventional CCTA, CTDSA improved reader con dence in 13/36 (36%) of segments with severe calci cation and 3/5 (60%) of segments with coronary stents. Also, the false positive rate of CTDSA was reduced compared to conventional CCTA from 18% (24/130) to 14% (19/130).

Diagnostic performance of coronary CT angiography with ultra-high-resolution CT: Comparison with invasive coronary angiography

PURPOSE Recently, ultra-high-resolution computed tomography (U-HRCT) with a 0.25 mm × 128-row detector was introduced. The purpose of this study was to evaluate the diagnostic performance of coronary CT angiography (CCTA) using U-HRCT. METHODS This retrospective study included 38 consecutive patients with suspected coronary artery disease (CAD) who underwent CCTA with U-HRCT followed by invasive coronary angiography (ICA). Per-segment diameter stenosis was calculated. Diagnostic performance of CCTA relative to ICA as the reference standard was determined. For segments with >30% diameter stenosis, the correlation and agreement of percent diameter stenosis between CCTA and ICA were calculated. RESULTS Obstructive CAD was observed in 65 segments (12%) of 51 vessels (45%) in 32 patients (84%) during ICA. The per-patient, vessel, and segment analyses showed a sensitivity of 100% (95% confidence interval [CI], 95%-100%), 96% (95% CI: 89%-99%) and 95% (95% CI: 89%-98%), respectively, and a specificity of 67% (95% CI: 38%-67%), 81% (95% CI: 75%-83%) and 96% (95% CI: 96%-97%), respectively. The percentage of diameter stenosis, as determined by CCTA, demonstrated an excellent correlation with ICA (R = 0.90; 95% CI: 0.83-0.95) and a slight significant overestimation (mean: 4% ± 7%, p < .01), with the agreed range of limits being ± 16%. The median effective radiation dose for CCTA was 5.4 mSv (range: 2.9-18.0 mSv). CONCLUSIONS CCTA with U-HRCT demonstrated an excellent correlation and agreement with ICA in the quantification of coronary artery stenosis.

Systematic evaluation of collateral pathways to the artery of Adamkiewicz using computed tomography

OBJECTIVES Preoperative identification of the artery of Adamkiewicz can help prevent postoperative spinal cord injury in patients undergoing thoracic and thoraco-abdominal aortic aneurysm repair. Although several studies have shown the feasibility of evaluating the artery of Adamkiewicz using multidetector row computed tomography (MDCT), no detailed investigations regarding the collateral circulation to the artery of Adamkiewicz have been performed. The purpose of this study was to investigate the collateral circulation to the artery of Adamkiewicz using MDCT in patients with thoracic and thoraco-abdominal aortic aneurysms. METHODS Our institutional review board approved this study. Sixty-four patients with descending thoracic and thoraco-abdominal aortic aneurysms associated with the occlusion of the segmental artery from which the artery of Adamkiewicz originated were scanned using 64- or 320-detector row computed tomography. Two independent observers evaluated the MDCT images based on the degree of visualization of the artery of Adamkiewicz and its collateral circulation using a 4-point scale. RESULTS The average visualization score was 2.8 ± 0.6. In 53 of the 64 (83%) patients, image quality was judged to be diagnostic. MDCT demonstrated 75 collateral pathways to the artery of Adamkiewicz in these 53 patients. Sixty-four of the 75 (85%) pathways were collaterals around the spinal column, and the remaining 11 (15%) pathways were collateral arteries in the thoracic wall. CONCLUSIONS MDCT revealed the collateral pathways to the artery of Adamkiewicz around the spinal column and in the thoracic wall in 83% of our patients with thoracic and thoraco-abdominal aortic aneurysms.

Novel developments in non-invasive imaging of peripheral arterial disease with CT: experience with state-of-the-art, ultra-high-resolution CT and subtraction imaging

Despite advances, challenges remain for less invasive imaging of peripheral arterial occlusive disease (PAOD) using computed tomography (CT) angiography. The application of dual-energy imaging to PAOD has been reported to improve the diagnostic accuracy of this application; however, severe arteriosclerosis with heavy arterial wall calcification still hampers definitive lesion characterisation, especially in distal and smaller arteries. Recently an ultra-high resolution scanner has been introduced. In combination with advances in post-processing, such as subtraction techniques, these developments may overcome some of the current challenges and allow far more detailed characterisation of PAOD non-invasively. The aim of this review is to describe our current experience with ultra-high resolution CT in combination with subtraction and discuss the potential advantages of their application for peripheral angiography.