Improved repeatability of subsolid nodule measurement in low-dose lung screening with monoenergetic images: a phantom study

Abstract

Background: To investigate whether monoenergetic images captured with dual-layer spectral computed tomography (CT) can improve the repeatability of subsolid nodule measurement, and whether this approach can further reduce the radiation dose of CT while maintaining its measurement repeatability. Methods: An anthropomorphic phantom with simulated subsolid nodules at three different levels was repeatedly scanned with both conventional single-energy CT and dual-layer spectral CT. A proxy for the measurement repeatability in the National Lung Screening Trial (proxy for NLST) was calculated with the typical CT protocol used in NLST. Using the dual-layer spectral CT, monoenergetic images of 40 to 110 keV, with an interval of 10 keV, were generated. The average diameter and volume of a total of 15,120 nodules in 840 CT images were measured by using a commercially-available computer-aided detection (CAD) system. The repeatability coefficient (RC), %RC, and 95% confidence intervals (CIs) of each image set were calculated and compared. Results: At the same tube voltage and tube current-time product, monoenergetic images resulted in significantly lower RC than the proxy for NLST, indicating that measurement repeatability was enhanced. When the radiation dose was lowered by 30% or 55%, monoenergetic images showed significantly lower RC at high-energy keV than the proxy for NLST. The estimated measurement repeatability from monoenergetic images with 30% or 55% lower radiation dose was comparable to the repeatability from conventional singleenergy CT images with standard radiation dose and iterative reconstruction. Conclusions: Monoenergetic images captured by using dual-layer spectral CT can improve the repeatability of subsolid nodule measurement. The use of monoenergetic images would allow lung cancer screening with a lower radiation dose, while maintaining comparable measurement repeatability.

The application of dual-layer spectral detector computed tomography in solitary pulmonary nodule identification

“…The latest dual-layer spectral detector CT (SDCT) acquires homologous, in-phase, and temporally synchronized photons from a single source, thereby enabling energysensitive projection data to be obtained simultaneously. The system applies anti-correlated noise suppression and an iterative algorithm, thus reducing image noise and improving image quality (10)(11)(12). Another advantage that SDCT has over other types of dual-energy CT is that it can generate all spectral datasets without the need to pre-set dual-energy protocols, thereby efficient clinical workflow (13)(14)(15)(16).…”

Factors influencing the outcome of volumetry tools for pulmonary nodule analysis: a systematic review and attempted meta-analysis

“…Mono-energetic reconstructions at 70 keV using dual-energy spectral CT are considered equivalent to conventional CT images acquired using 120 kVp, and several authors found no significant difference in volumetry accuracy between them [ 86 – 88 ]. In addition, mono-energetic reconstructions improved the repeatability of volumetry at the same radiation dose [ 87 ].…”

Ultra-low-dose spectral-detector computed tomography for the accurate quantification of pulmonary nodules: an anthropomorphic chest phantom study

“…The measurement repeatability of VMIs for pulmonary nodules were equivalent to that of conventional images using the IR algorithm at a standard dose, suggesting the use of monoenergetic images might allow lung cancer screening at a lower radiation dose. 31 Other data revealed that images at a low single-energy level have lower noise and higher image contrast. 32 Regarding spectral CT, low VMIs exhibited better image quality than conventional images from the same system.…”