ABSTRACT
OBJECTIVE: To evaluate the contribution of iterative reconstruction on image quality of reduced-dose multidetector computed tomography of the thoracic aorta. METHODS: A torso phantom was scanned using two tube potentials (80 and 120 kVp) and five different tube currents (110, 75, 40, 20, and 10 mAs). All images were reconstructed with both filtered back projection (FBP) and iterative reconstruction. Aortic attenuation, image noise within the thoracic aorta, signal-to-noise ratio, and sharpness of the aortic wall were quantified in the phantom for the two reconstruction algorithms. Data were analyzed using paired t test. A value of P < 0.05 was considered significant. RESULTS: The aortic attenuation was similar for FBP and iterative reconstruction (P > 0.05). Image noise level was lower (P < 0.0001), and image sharpness was higher (P = 0.046) with iterative reconstruction. Signal-to-noise ratios were higher with iterative reconstruction compared with those with FBP (P < 0.0001). Signal-to-noise ratio at 80 kVp with iterative reconstruction (9.8 ± 4.4) was similar to the signal-to-noise ratio at 120 kVp with FBP (8.4 ± 3.3) (P = 0.196). CONCLUSIONS: Less image noise and higher image sharpness may be achieved with iterative reconstruction in reduced-dose multidetector computed tomography of the thoracic aorta.
Subject(s)
Aorta, Thoracic/diagnostic imaging , Multidetector Computed Tomography/methods , Radiographic Image Interpretation, Computer-Assisted/methods , Algorithms , Humans , Phantoms, Imaging , Radiation Dosage , Signal-To-Noise RatioABSTRACT
OBJECTIVE: The purpose of this study was intrapatient comparison of image quality and radiation dose between MDCT scans of the chest, abdomen, and pelvis obtained with attenuation-based automated kilovoltage selection and sinogram-affirmed iterative reconstruction and scans obtained with standard kilovoltage selection and a filtered backprojection image reconstruction algorithm. MATERIALS AND METHODS: One hundred one oncology patients who had undergone two chest, abdominal, and pelvis CT scans within 1 year were imaged with standard tube voltage selection of 120 kVp using a filtered backprojection reconstruction algorithm (protocol 1) and with attenuation-based automated tube voltage selection using an iterative reconstruction algorithm (protocol 2). Radiation dose parameters (volumetric CT dose index [CTDIvol], dose-length product, and effective dose) as well as image noise, signal-to-noise ratio, and contrast-to-noise ratio were compared. Two independent radiologists evaluated image quality and sharpness. Student t test, Fisher exact test, and Wilcoxon signed-rank test were used for analysis. A p value less than 0.05 was considered significant. RESULTS: Mean ± SD CTDIvol values were 19.9 ± 4.43 mGy and 12.53 ± 4.79 mGy for protocols 1 and 2, respectively (p < 0.0001). Effective dose was 38.2% lower on average using protocol 2 compared with protocol 1 (12.08 vs 19.55 mSv; p < 0.0001). Objective image quality parameters were significantly better in protocol 2 (p < 0.0001). Both radiologists found the overall image quality and sharpness to be similar for both protocols (p > 0.05). CONCLUSION: In patients undergoing CT examination of the chest, abdomen, and pelvis, the combination of attenuation-based automated tube voltage selection with iterative reconstruction significantly reduced radiation dose parameters and maintained objective image quality when compared with standard tube voltage selection associated with filtered backprojection reconstruction.
Subject(s)
Multidetector Computed Tomography/methods , Radiographic Image Interpretation, Computer-Assisted/methods , Radiography, Abdominal , Radiography, Thoracic , Algorithms , Contrast Media , Female , Humans , Iohexol , Male , Middle Aged , Pelvis/diagnostic imaging , Radiation Dosage , Retrospective StudiesABSTRACT
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. CONCLUSION: 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.
