Effect of radiation dose and iterative reconstruction on lung lesion conspicuity at MDCT: does one size fit all?
OBJECTIVE
To evaluate the effect of different acquisition parameters and reconstruction algorithms in lung lesions conspicuity in chest MDCT.


METHODS
An anthropomorphic chest phantom containing 6 models of lung disease (ground glass opacity, bronchial polyp, solid nodule, ground glass nodule, emphysema and tree-in-bud) was scanned using 80, 100 and 120 kVp, with fixed mAs ranging from 10 to 110. The scans were reconstructed using filtered back projection (FBP) and iterative reconstruction (IR) algorithms. Three blinded thoracic radiologists reviewed the images and scored lesions conspicuity and overall image quality. Image noise and radiation dose parameters were recorded.


RESULTS
All acquisitions with 120 kVp received a score of 3 (acceptable) or higher for overall image quality. There was no significant difference between IR and FBP within each setting for overall image quality (p>0.05), even though image noise was significantly lower using IR (p<0.0001). When comparing specific lower radiation acquisition parameters 100 kVp/10 mAs [Effective Dose (ED): 0.238 mSv] vs 120 kVp/10 mAs (ED: 0.406 mSv) vs 80 kVp/40 mAs (ED: 0.434 mSv), we observed significant difference in lesions conspicuity (p<0.02), as well as significant difference in overall image quality, independent of the reconstruction algorithm (p<0.02), with higher scores on the 120 kV/10 mAs setting. Tree-in-bud pattern, ground glass nodule and ground glass opacity required lower radiation doses to get a diagnostic score using IR when compared to FBP.


CONCLUSIONS
Designing protocols for specific lung pathologies using lower dose acquisition parameters is feasible, and by applying iterative reconstruction, radiologists may have better diagnostic confidence to evaluate some lesions in very low dose settings, preserving acceptable image quality.
Department of Radiology, Northwestern Memorial Hospital, Northwestern University - Feinberg School of Medicine, Chicago, IL, USA.
Marcos Paulo Ferreira
MP
Botelho
Rishi
R
Agrawal
Fernanda Dias
FD
Gonzalez-Guindalini
Eric M
EM
Hart
Suresh K
SK
Patel
Hüseyin Gürkan
HG
Töre
Vahid
V
Yaghmai
D000465:Algorithms; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D061330:Multidetector Computed Tomography / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011874:Radiometry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
CT; Conspicuity; Lung lesions; Radiation dose; Reconstruction Algorithm