Feasibility of Dose-reduced Chest CT with Photon-counting Detectors: Initial Results in Humans

Abstract

Purpose To investigate whether photon-counting detector (PCD) technology can improve dose-reduced chest computed tomography (CT) image quality compared with that attained with conventional energy-integrating detector (EID) technology in vivo. Materials and Methods This was a HIPAA-compliant institutional review board-approved study, with informed consent from patients. Dose-reduced spiral unenhanced lung EID and PCD CT examinations were performed in 30 asymptomatic volunteers in accordance with manufacturer-recommended guidelines for CT lung cancer screening (120-kVp tube voltage, 20-mAs reference tube current-time product for both detectors). Quantitative analysis of images included measurement of mean attenuation, noise power spectrum (NPS), and lung nodule contrast-to-noise ratio (CNR). Images were qualitatively analyzed by three radiologists blinded to detector type. Reproducibility was assessed with the intraclass correlation coefficient (ICC). McNemar, paired t, and Wilcoxon signed-rank tests were used to compare image quality. Results Thirty study subjects were evaluated (mean age, 55.0 years ± 8.7 [standard deviation]; 14 men). Of these patients, 10 had a normal body mass index (BMI) (BMI range, 18.5-24.9 kg/m; group 1), 10 were overweight (BMI range, 25.0-29.9 kg/m; group 2), and 10 were obese (BMI ≥30.0 kg/m, group 3). PCD diagnostic quality was higher than EID diagnostic quality (P = .016, P = .016, and P = .013 for readers 1, 2, and 3, respectively), with significantly better NPS and image quality scores for lung, soft tissue, and bone and with fewer beam-hardening artifacts (all P < .001). Image noise was significantly lower for PCD images in all BMI groups (P < .001 for groups 1 and 3, P < .01 for group 2), with higher CNR for lung nodule detection (12.1 ± 1.7 vs 10.0 ± 1.8, P < .001). Inter- and intrareader reproducibility were good (all ICC > 0.800). Conclusion Initial human experience with dose-reduced PCD chest CT demonstrated lower image noise compared with conventional EID CT, with better diagnostic quality and lung nodule CNR. RSNA, 2017 Online supplemental material is available for this article.

Photon Counting Computed Tomography With Dedicated Sharp Convolution Kernels

“…14 Fourth, without the intermediate transformation step needed in EIDs, the electronic noise of PCDs is lower, translating into lower image noise and higher contrast-tonoise ratios. 6,15,16 In theory, such technical advances of PCD arrays should translate into an improved image quality and better coronary stent evaluation. In a first in vitro study, Mannil et al 17 found increased overall image quality, improved in-stent lumen delineation, and reduced blooming artifacts.…”

“…Investigative Radiology • Volume 00, Number 00, Month 2018 Photon Counting CT With Sharp Stent Kernel novel technique might be an important step improving imaging characteristics not only in-plane but also in through-plane direction. First in vivo measurements found that PCD technology, in combination with standard convolution kernels, can yield lower image noise and an increased contrast-to-noise ratio in low-dose chest CT 16 and low-dose lung cancer screening. 15 In contrast, noise measurements in our study showed that use of dedicated sharp convolution kernels was associated with a significant increase in image noise compared with standard kernels.…”

Photon-Counting CT of the Brain: In Vivo Human Results and Image-Quality Assessment

“…8 In addition, the direct conversion and counting of individual photons provide a better estimate of the underlying photon statistics, which, in turn, may improve image quality by reducing image noise. 8,[12][13][14] We hypothesized that the combined effects of better contrast and reduced noise may lead to better overall GM-WM differentiation in brain PCD CT.…”

Basic principles and clinical potential of photon-counting detector CT

“…The better performance of photon-counting CT at very low radiation dose was attributed to the effective elimination of electronic noise and better weighting of low-energy X-ray photons. In a study with 30 human subjects [52], the authors evaluated whether photon-counting detectors can improve dose-reduced chest CT image quality in vivo. Compared to energy-integrating CT, photon-counting CT demonstrated higher diagnostic quality with significantly better image quality scores for lung, soft tissue, and bone and with fewer beam-hardening artifacts, lower image noise, and higher CNR for lung nodule detection (see Fig.…”