High‐pitch, high temporal resolution, multi‐energy cardiac imaging on a dual‐source photon‐counting‐detector CT

Abstract

To measure the accuracy of material decomposition using a dualsource photon-counting-detector (DS-PCD) CT operated in the high-pitch helical scanning mode and compare the results against dual-source energyintegrating-detector (DS-EID) CT, which requires use of a low-pitch value in dual-energy mode. Methods: A DS-PCD CT and a DS-EID CT were used to scan a cardiac motion phantom consisting of a 3-mm diameter iodine cylinder. Iodine maps were reconstructed using DS-PCD in high-pitch mode and DS-EID in low-pitch mode. Image-based circularity, diameter, and iodine concentration of the iodine cylinder were calculated and compared between the two scanners. With institutional review board approval, in vivo exams were performed with the DS-PCD CT in high-pitch mode. Images were qualitatively compared against patients with similar heart rates that were scanned with DS-EID CT in low-pitch dual-energy mode.Results: On iodine maps, the mean circularity was 0.97 ± 0.02 with DS-PCD in high-pitch mode and 0.95 ± 0.06 with DS-EID in low-pitch mode. The mean diameter was 2.9 ± 0.2 mm with DS-PCD and 3.1 ± 0.2 mm with DS-EID, both of which are close to the 3 mm ground truth. For DS-PCD, the mean iodine concentration was 9.6 ± 0.8 mg/ml and this was consistent with the 9.4 ± 0.6 mg/ml value obtained with the cardiac motion disabled. For DS-EID, the concentration was 12.7 ± 1.2 mg/ml with motion enabled and 11.7 ± 0.5 mg/ml disabled. The background noise in the iodine maps was 15.1 HU with DS-PCD and 14.4 HU with DS-EID, whereas the volume CT dose index (CTDI vol ) was 3 mGy with DS-PCD and 11 mGy with DS-EID. On comparison of six patients (three on PCD, three on EID) with similar heart rates, DS-PCD provided iodine maps with welldefined coronaries even at a high heart rate of 86 beats per minute. Meanwhile, there were substantial motion artifacts in iodine maps obtained with DS-EID for patients with similar heart rates. Conclusion:In a cardiac motion phantom, DS-PCD CT can perform accurate material decomposition in high-pitch mode, providing iodine maps with excellent geometric accuracy and robustness to motion at approximately 38% of the dose for similar noise as DS-EID CT.

Influence of heart rate and heart rate variability on the feasibility of ultra-fast, high-pitch coronary photon-counting computed tomography angiography

“…At the same dose, the higher photon efficiency leads to lower image noise [13], possibly shifting the threshold above which unacceptable decreases in image quality occur. Furthermore, the generated virtual monoenergetic images improve iodine contrast, which may allow better differentiation between cardiac vessels and tissue [18]. Only 5.4% of the included patients had a HR of 70 or more, and the highest recorded heart rate at the scan was 73.…”

Photon-Counting Detector Computed Tomography Versus Energy-Integrating Detector Computed Tomography for Coronary Artery Calcium Quantitation

“…Patients were brought to PCD-CT immediately after completion of their EID-CT scan. Photon-counting detector CT scans were acquired using a prospectively triggered dual-source high-pitch “Flash” protocol (“CardiacFlashSpiralAdultQuantumplus,” pitch = 3.2) 15 with 120-kV, CARE keV image quality level of 32, 0.25-second rotation time, 144 × 0.4-mm collimation (5.76-cm z -axis coverage), and a 55% starting phase.…”

“…13,14 This provides brighter signal for low concentrations of high atomic number materials. With use of 2 x-ray tubes and 2 detectors (ie, a dual-source geometry) and a 0.25-second rotation time, cardiac multienergy imaging is possible with a temporal resolution of 66 ms. 6,15 In dual-source EID-CT scanners, the temporal resolution must be decreased to 125 ms if multienergy imaging capabilities are desired. In total, PCD-CT offers many advantages for quantitative imaging applications in the heart.…”

High-Pitch Multienergy Coronary CT Angiography in Dual-Source Photon-Counting Detector CT Scanner at Low Iodinated Contrast Dose

“…In cardiac phantoms, this mode performs material decomposition with excellent geometric and quantitative accuracy, and motion robustness, due to improved temporal resolution and spatiotemporal registration. 20 A dynamic phantom study showed the possibility of 50% contrast reduction using low-energy VMI in this mode. 21 A thoracic CTA study using this mode showed significantly increased contrast-to-noise ratio (CNR) of low-energy VMI compared with conventional energy integrating detector (EID) CT at the same radiation dose.…”

“…The first commercial dual-source (DS) PCD-CT (NAEOTOM Alpha; Siemens) has a novel high-pitch helical ME scan mode (Quantumplus), which enables a helical pitch up to 3.2 simultaneous to an ME acquisition at a temporal resolution of 66 milliseconds. In cardiac phantoms, this mode performs material decomposition with excellent geometric and quantitative accuracy, and motion robustness, due to improved temporal resolution and spatiotemporal registration 20 . A dynamic phantom study showed the possibility of 50% contrast reduction using low-energy VMI in this mode 21 .…”