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. 2017 Jan 7;62(1):202-213.
doi: 10.1088/1361-6560/62/1/202. Epub 2016 Dec 17.

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

Rolf Symons  1 , Tyler E Cork, Pooyan Sahbaee, Matthew K Fuld, Steffen Kappler, Les R Folio, David A Bluemke, Amir Pourmorteza
Affiliations

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

Rolf Symons et al. Phys Med Biol. .

Abstract

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. 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 (HU) accuracy, noise levels, and contrast-to-noise ratios (CNR) for detection of ground-glass nodules (GGN) and emphysema. The PCD HU 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 HUs 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 versus 15.8 ± 0.2 HU, P = 0.03; 16.1 ± 0.3 HU versus 18.0 ± 0.4 HU, P = 0.003; and 16.1 ± 0.3 HU versus 17.9 ± 0.3 HU, P = 0.001, respectively), resulting in superior CNR for evaluation of GGNs and emphysema at 100 and 80 kVp. PCD provided better HU stability for lung, ground-glass, and emphysema-equivalent 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.

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Conflict of interest statement

Authors who are not employees of or consultants for Siemens had control of inclusion of any data and information that might present a conflict of interest for the authors who are employed by Siemens.

Figures

Figure 1
Figure 1
EID (A) and PCD (B) scans of the COPDGene 2 phantom. The 7 calibrated test object materials regions-of-interest (ROIs) used for analysis are labeled: A, emphysema foam; B, acrylic; C, 12-lb foam; D, water; E, ground-glass nodule foam; F, lung foam; G, air.
Figure 2
Figure 2
Hounsfield unit (HU) accuracy with standard error of the mean (SEM) for lung (A), ground-glass nodules (B), and emphysema (C) equivalent foams of the COPDGene 2 phantom for EID and PCD at different dose levels. For better visualization, the measured values are subtracted from nominal HU values reported by the phantom manufacturer at 120 kVp. EID HU accuracy was inferior to PCD at 1.5 and 0.75 mGy CTDIvol dose levels. **: P<0.05.
Figure 3
Figure 3
Image noise of SAFIRE 3 Q30f reconstructions of the COPDGene 2 phantom at different tube voltages. Dots represent the noise levels for individual repetitions at each dose level. Lines connect the average noise levels for EID (blue) and PCD (red) at each dose level. PCD noise was significantly lower than EID at the lowest dose setting for all tube voltages. **: P<0.05.
Figure 4
Figure 4
Contrast-to-noise ratios (CNR) for the detection of ground-glass nodules (A) and emphysema (B). CNR for both ground-glass nodules and emphysema was significantly higher for PCD (red) than EID (blue) for the lowest dose setting at 100 and 80 kVp. **: P<0.05
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