University of Twente Student Theses


Artery size adjusted calcium score for contrast-enhanced CT scans in peripheral artery disease patients

Derksen, M. (2022) Artery size adjusted calcium score for contrast-enhanced CT scans in peripheral artery disease patients.

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Embargo date:1 September 2024
Abstract:Background: Patients suffering from peripheral artery disease (PAD) are at increased risk of major amputations and cardiac mortality. Identifying patients at risk is desired to optimize patient care and minimize the risk of these complications. Calcium scores, determined on non-contrast computed tomography (CT) scans in coronary arteries, have proven to be a strong tool in identifying patients at risk for future cardiovascular events. Objectives: The objective of this study was divided into two parts. First, a reliable method is developed for determining the calcium score on contrast-enhanced CT scans in non-coronary arteries. Second, the developed contrast calcium score method determined in the iliofemoral arteries is associated with worse patient outcomes within the first year of an endovascular or surgical revascularization. Methods: First, a volume adjusted calcium score (VACS) was proposed to compensate for variation in artery size between patients. Four-phase liver scans were used to compare the VACS for non-contrast and contrast CT scans. Patient-specific thresholds of two and three standard deviations (SD) above the mean contrast attenuation were analyzed. In addition, the inter-observer agreement and influence of slice thickness were investigated. Second, in addition to the VACS, the length adjusted calcium score (LACS) was proposed and evaluated for patients with PAD. A complication and matched control group with similar characteristics were created, with the complication patients undergoing secondary revascularization, major amputation or all-cause mortality within the first year of a primary revascularization. Calcium scores were determined in three arterial segments: common iliac artery (CIA), external iliac artery (EIA) & common femoral artery (CFA) and proximal superficial femoral artery (SFA). Results: The three SD above the mean contrast attenuation was best for distinguishing contrast and calcium. An excellent intra-class correlation (ICC) coefficient (0.97) was found between VACS determined on non-contrast and contrast scans after applying a correction factor of 1.95. The inter-observer agreement for VACS determined on the contrast CT scan was also excellent (0.99). Furthermore, the 0.75 mm slices were less suitable for determining the calcium score than the 2 mm slices due to an increase in noise. No statistically significant difference was found between the complication and control group for any of the segments and complications. However, most high scores calcium scores were found in the complication group in the proximal SFA. Conclusion: The proposed VACS determined on contrast-enhanced CT scans correlated excellently with non-contrast calcium scores. Furthermore, the VACS had an excellent inter-observer agreement. No statistically significant differences were found between patients with and without complications after a revascularization intervention. However, in future studies the distal SFA and popliteal artery should be included.
Item Type:Essay (Master)
Faculty:TNW: Science and Technology
Subject:44 medicine
Programme:Technical Medicine MSc (60033)
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