The purpose of this study was the evaluation of two radiologists and three different CAD-systems as first and second readers for lung cancer screening at various CT dose levels including low kilo-voltage settings,
to find the best reader pairing at the lowest acceptable radiation exposure level.Sensitivity of CT for lung nodules depends on many things like nodule size,
reader and post-processing tools [1-7].
Most of these given variables may not be changed,
except for the last ones.
Methods and Materials
All CT scans were performed on a 64-row multi-detector CT scanner Somatom Sensation 64 (24x1.2mm,
slice thickness 1.5mm by Siemens,
Automatic current modulation (CareDose4D) was used for raw data acquisition and filtered back projection was used for image reconstruction.
Three tube current-time products of 25,
50 and 100 mAs (Miliampèresecond) were combined with 80,
120 kVp (peak Kilovoltage),
resulting in 9 different pairings: 8 low dose levels were compared against the standard dose CT of 100mAs/120kVp.
Individual nodule detection (first reader):
Individual standard CT sensitivities for lung nodules were 92.2%,
83.3% and 67.6% for reader 1,
respectively (Table 1).
Only the sensitivity of CAD3 is significantly lower than radiologists’ sensitivity (p<0.001).
Sensitivity at lowest dose level decreases to 87.8%,
and 67.8% for reader 1,
1). Only CAD2 showed a significant loss of sensitivity at lowest dose level (64.1%,
Combined nodule detection (first and second reader)...
Our results suggest that lung cancer screening should be performed by a radiologist using any CAD.
Combined CT-sensitivity does not drop significantly at lower dose levels,
including 25mAs/80kVpwith an average dose length product of 22.3 mGycm,
equaling an equivalent dose of 0.3 Millisievert.
In a previous study (under review),
we stated that a minimum dose level of 25 ref mAs/100kVp is needed to detect both solid and ground glass nodules.
This threshold level applies to GGNs when analyzed separately,
but in a lung cancer screening...
1 Christe A,
Charimo Torrente J,
Computed-Tomography (CT) screening and follow up of lung nodules: effect of CT-tube current-time,
nodule size and density on detectability of lung nodules and impact of tube current-time on the apparent nodule size.
Am J Roentgenol 2011;197(3):623-30
2 Ko JP,
Wavelet compression of low-dose chest CT data: effect on lung nodule detection.
Radiology 2003; 228:70 -75
3 Rusinek H,
McGuinness et al.
Pulmonary nodule detection: low-dose versus conventional...
1Department of Radiology,
Hospital Center of Biel,
3Department of Radiology,