Low-dose CT screening for lung cancer with automatic exposure control: phantom study

Abstract

We conducted a study to determine optimal scan conditions for automatic exposure control (AEC) in computed tomography (CT) of low-dose chest screening in order to provide consistent image quality without increasing the collective dose. Using a chest CT phantom, we set CT-AEC scan conditions with a dose-reduction wedge (DR-Wedge) to the same radiation dose as those for low-tube current, fixed-scan conditions. Image quality was evaluated with the use of the standard deviation of the CT number, contrast-noise ratios (CNR), and receiver-operating characteristic (ROC) analysis. At the same radiation dose, in the scan conditions using CT-AEC with the DR-Wedge, the SD of the CT number of each slice position was stable. The CNR values were higher at the lung apex and lung base under CT-AEC with the DR-Wedge than under standard scan conditions (p < 0.0002). In addition, ROC analysis of blind evaluation by four radiologists and three technologists showed that the image quality was improved for the lung apex (p < 0.009), tracheal bifurcation (p < 0.038), and lung base (p < 0.022) in the scan conditions using CT-AEC with the DR-Wedge. We achieved improvement of image quality without increasing the collective dose by using CT-AEC with the DR-Wedge under low-dose scan conditions.

Evaluation of an in-use chest CT protocol in lung cancer screening - A single institutional study

“…Study findings have shown greater variability and inaccuracy in volume determination of small nodules compared with large nodules with different slice thicknesses. [38][39][40] Winer-Muram and colleagues 41 found that an increase in slice thickness leads to an increase in overestimation of nodule volume. Our data indicates that MBIR (IMR) improves the image quality of LDCT more than hybrid algorithm (iDose) which is in accordance with previous studies.…”

A phantom study investigating the relationship between ground‐glass opacity visibility and physical detectability index in low‐dose chest computed tomography

“…The anthropomorphic chest phantom (LSCT001; Kyoto Kagaku Co., Kyoto, Japan) 12 , 15 , 16 , 17 used in this study has a chest circumference of 930 mm and a height of 370 mm, modeling Japanese adult men of 40 years of age or older. The materials used in the phantom are a radiographic water‐equivalent substance for the chest wall and mediastinum and a radiographic bone‐equivalent substance for the vertebrae and ribs.…”

“…For these reasons, the effect of acquisition and reconstruction parameters on GGO detectability has been of long‐standing interest in the investigation of LDCT performance. However, most previous reports on the technical aspects of LDCT have only studied the effects of dose level and/or image noise (i.e., standard deviation) 14 , 15 , 16 . To our knowledge, only a single published report has described the results of modulation transfer function (MTF) as a resolution property index (9) .…”