Low-dose lung cancer screening with photon-counting CT: a feasibility study

Abstract

Objective To evaluate the feasibility of using a whole-body photon-counting detector (PCD) CT scanner for low dose lung cancer screening compared to a conventional energy integrating detector (EID) system. Materials and Methods Radiation dose-matched EID and PCD scans of the COPDGene 2 phantom were acquired at different radiation dose levels (CTDIvol: 3.0, 1.5, and 0.75 mGy) and different tube voltages (120, 100, and 80 kVp). EID and PCD images were compared for quantitative Hounsfield unit accuracy, noise levels, and contrast-to-noise ratios (CNR) for detection of ground-glass nodules (GGN) and emphysema. Results The PCD Hounsfield unit accuracy was better than EID for water at all scan parameters. PCD HU stability for lung, GGN and emphysema regions were superior to EID and PCD attenuation values were more reproducible than EID for all scan parameters (all P<0.01), while Hounsfield units for lung, GGN and emphysema ROIs changed significantly for EID with decreasing dose (all P<0.001). PCD showed lower noise levels at the lowest dose setting at 120, 100 and 80 kVp (15.2±0.3 HU vs 15.8±0.2 HU, P=0.03; 16.1±0.3 HU vs 18.0±0.4 HU, P=0.003; and 16.1±0.3 HU vs 17.9±0.3 HU, P=0.001, respectively), resulting in superior CNR for evaluation of GGNs and emphysema at 100 and 80 kVp. Conclusion PCD provided better Hounsfield unit stability for lung, ground-glass, and emphysemaequivalent foams at lower radiation dose settings with better reproducibility than EID. Additionally, PCD showed up to 10% less noise, and 11% higher CNR at 0.75 mGy for both 100 and 80 kVp. PCD technology may help reduce radiation exposure in lung cancer screening while maintaining diagnostic quality.

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

“…The suppression of electronic noise with PCD CT leads to better attenuation stability and lower image noise; this concept has been extensively evaluated in a specialized lung phantom for chest CT (9,10). PCD CT demonstrated up to 11.8% less image noise and 11.4% higher CNR in low-contrast lesion detectability (eg, ground-glass nodules and emphysema) for multiple combinations of tube current and tube voltage settings.…”

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

“…18 Therefore, we matched the tube voltage and tube current-time product values to obtain a similar energy spectrum and the number of x-ray photons incident on both detector systems, allowing a fair comparison. 13 The effective dose was calculated by multiplying the dose-length product by 0.0021 mSv/mGy as the constant k-value for brain imaging.…”

“…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.…”

Spectral performance of a whole-body research photon counting detector CT: quantitative accuracy in derived image sets

“…Previous studies using this scanner demonstrated that the PCCT was capable of providing clinical image quality at X-ray photon flux encountered in routine CT exams, which were commensurate with commercial EID systems (Yu et al, 2016a, Pourmorteza et al, 2016). Benefits of this specific PCCT scanner over the state-of-the-art CT scanner using EIDs have been previously demonstrated and include improved CNR, increased spatial resolution, and better HU stability at low dose (Gutjahr et al, 2016, Leng et al, 2017, Symons et al, 2016). These studies, however, focused only on traditional image quality in a single-energy mode, i.e.…”