Fifty-eighth annual meeting of the american association of physicists in medicine
SU-F-I-04: Low Dose CT Lung Cancer Screening Protocol Evaluation
The purpose of this study was to evaluate protocols for low dose CT (LDCT) for lung cancer screening on a Revolution CT (GE Healthcare; Waukesha, WI). Lung cancer the leading cause of cancer death for men and women, and more deaths are attributable to lung cancer than breast, colon and prostate cancers combined. Recently, the National Lung Screening Trial (NLST) showed LDCT screening resulted in a 20% reduction in lung cancer mortality and 6.7% in mortality from all causes [NEJM, 2011].
The protocols for this study (Table 1) were designed based on the following criteria: (1) CTDIvol ≤ 3.0 mGy (for an “average” person), (2) dose variation based on patient size, (3) the ability to scan the entire lung in a single breath, (4) adequate image quality for LCS including the ability to detect nodules ≥ 5mm. A chest phantom (Chest Phantom N1, Kyoto Kagaku Co., Ltd, Kyoto Japan) was scanned with three fat plate configurations (small, average and large) and six artificial nodules: solid (+100 HU; 5, 8, and 10 mm) and non-solid (-630 HU; 5, 8, and 10 mm). The nodules were inserted into the lung structure along the vessels. Each scan was repeated 5 times. The contrast to noise ratio (CNR) was measured in the 5 mm nodules as the figure of merit for detectability (Figure 1). The sizes of all nodules were measured using a manual distance tool.
All phantom images showed sufficient image quality for lung nodule detection. CNR values were all more than sufficient for nodule detection of the kind and size related to lung cancer screening (Figure 2). Nodule size measurements all showed accuracy within 0.3 mm (Figure 3).
This phantom study shows the presented low-dose protocols should meet the needs for LDCT Lung Cancer Screening.
All authors are employees of GE Healthcare.