Coronary Computed Tomography Angiography-Based Calcium Scoring

Abstract

PurposeThe aim of this study was to evaluate coronary computed tomography angiography (CCTA)-based in vitro and in vivo coronary artery calcium scoring (CACS) using a novel virtual noniodine reconstruction (PureCalcium) on a clinical first-generation photon-counting detector–computed tomography system compared with virtual noncontrast (VNC) reconstructions and true noncontrast (TNC) acquisitions.Materials and MethodsAlthough CACS and CCTA are well-established techniques for the assessment of coronary artery disease, they are complementary acquisitions, translating into increased scan time and patient radiation dose. Hence, accurate CACS derived from a single CCTA acquisition would be highly desirable. In this study, CACS based on PureCalcium, VNC, and TNC, reconstructions was evaluated in a CACS phantom and in 67 patients (70 [59/80] years, 58.2% male) undergoing CCTA on a first-generation photon counting detector–computed tomography system. Coronary artery calcium scores were quantified for the 3 reconstructions and compared using Wilcoxon test. Agreement was evaluated by Pearson and Spearman correlation and Bland-Altman analysis. Classification of coronary artery calcium score categories (0, 1–10, 11–100, 101–400, and >400) was compared using Cohen κ.ResultsPhantom studies demonstrated strong agreement between CACSPureCalcium and CACSTNC (60.7 ± 90.6 vs 67.3 ± 88.3, P = 0.01, r = 0.98, intraclass correlation [ICC] = 0.98; mean bias, 6.6; limits of agreement [LoA], −39.8/26.6), whereas CACSVNC showed a significant underestimation (42.4 ± 75.3 vs 67.3 ± 88.3, P < 0.001, r = 0.94, ICC = 0.89; mean bias, 24.9; LoA, −87.1/37.2). In vivo comparison confirmed a high correlation but revealed an underestimation of CACSPureCalcium (169.3 [0.7/969.4] vs 232.2 [26.5/1112.2], P < 0.001, r = 0.97, ICC = 0.98; mean bias, −113.5; LoA, −470.2/243.2). In comparison, CACSVNC showed a similarly high correlation, but a substantially larger underestimation (24.3 [0/272.3] vs 232.2 [26.5/1112.2], P < 0.001, r = 0.97, ICC = 0.54; mean bias, −551.6; LoA, −2037.5/934.4). CACSPureCalcium showed superior agreement of CACS classification (κ = 0.88) than CACSVNC (κ = 0.60).ConclusionsThe accuracy of CACS quantification and classification based on PureCalcium reconstructions of CCTA outperforms CACS derived from VNC reconstructions.

Radiation Dose Reduction for Coronary Artery Calcium Scoring Using a Virtual Noniodine Algorithm on Photon-Counting Detector Computed-Tomography Phantom Data

“…Despite the application of iterative reconstructions, this study demonstrated strong correlation and excellent agreement of CACS VNI with CACS TNC at every radiation dose level from 100 to 25%. This is in line with a previous study that evaluated the performance of the same VNI algorithm at standard radiation dose and demonstrated high accuracy for CACS [17]. CACS VNI differed significantly from CACS TNC at standard radiation dose only at 55 keV/QIR1 and dose level 50% but showed no significant differences at any radiation dose level for VNI reconstructions at 60 keV/QIR4.…”

“…For this study, a commercially available anthropomorphic chest phantom (QRM GmbH, Moehrendorf, Germany) was used with an insert designed for calcium scoring at the heart position. This insert contained nine cylinders with different diameters (1, 3, and 5 mm) and different densities (200, 400, and 800 mg/cm 3 calcium hydroxyapatite), and two calibration rods (one water-equivalent and one with 200 mg/cm 3 calcium hydroxyapatite) as recently described [17]. To simulate the different chest diameters, the phantom was scanned with and without extension rings, resulting in a total of three chest diameters: 300 × 200 mm (small; no extension ring), 350 × 250 mm (medium; extension ring M), and 400 × 300 mm (large; extension ring L).…”

“…Since conventional IR algorithms cannot simply be transferred to PCD-CT systems [30], the vendor of this first-generation PCD-CT introduced a quantum IR (QIR) algorithm with four strength levels. The images of all four radiation dose levels were postprocessed using a VNI algorithm (PureCalcium, Siemens Healthineers) as previously described [17], and reconstructed at two different VMI and QIR levels: 55 keV/QIR1 and 60 keV/QIR4. These reconstructions showed that VNI-based scores were the closest to the corresponding scores from reference TNC scans [31].…”

“…According to the guideline for minimizing radiation exposure during the acquisition of coronary artery calcium scans with the use of multidetector computed tomography [33], the recommended IN targets of 20 HU for small/medium-sized phantoms and 23 HU for large phantoms were used to further compare the IN between different reconstructions. CACS quantification was performed on VNI (CACS VNI ) and TNC (CACS TNC ) datasets using commercially available software (syngo.via Version VB60; Siemens Healthineers) that highlights calcified lesions by discriminating them from the background using a threshold of 130 HU [8], as recently described [17].…”

“…In this context, an iodine-removal algorithm specifically developed for PCD-CT outperformed virtual noncontrast (VNC) reconstructions for CACS at a standard radiation dose [17]. Due to the advantages of PCD-CT and accordingly this new VNI algorithm, we hypothesized that VNI reconstructions enable accurate CACS even in low-dose examinations.…”