Low-dose CT of the lung: potential value of iterative reconstructions

• Published in: European radiology Vol. 22; no. 12; pp. 2597 - 2606
• Main Authors: Baumueller, Stephan, Winklehner, Anna, Karlo, Christoph, Goetti, Robert, Flohr, Thomas, Russi, Erich W., Frauenfelder, Thomas, Alkadhi, Hatem
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.12.2012; Springer Nature B.V
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Computed Tomography; Demographics; Diagnostic Radiology; Female; Humans; Imaging; Internal Medicine; Interventional Radiology; Lung Diseases - diagnostic imaging; Male; Medicine; Medicine & Public Health; Middle Aged; Neuroradiology; Patients; Prospective Studies; Radiation; Radiation Dosage; Radiographic Image Interpretation, Computer-Assisted - methods; Radiology; Statistics, Nonparametric; Tomography; Tomography, X-Ray Computed - methods; Ultrasound; Germany; Lung; Image reconstruction; Image enhancement; Radiation dosage; Spiral computed tomography
• ISSN: 0938-7994; 1432-1084
• DOI: 10.1007/s00330-012-2524-0

Objectives To prospectively assess the impact of sinogram-affirmed iterative reconstruction (SAFIRE) on image quality of nonenhanced low-dose lung CT as compared to filtered back projection (FBP). Methods Nonenhanced low-dose chest CT (tube current-time product: 30 mAs) was performed on 30 patients at 100 kVp and on 30 patients at 80 kVp. Images were reconstructed with FBP and SAFIRE. Two blinded, independent readers measured image noise; two readers assessed image quality of normal anatomic lung structures on a five-point scale. Radiation dose parameters were recorded. Results Image noise in datasets reconstructed with FBP (57.4 ± 15.9) was significantly higher than with SAFIRE (31.7 ± 9.8, P  < 0.001). Image quality was significantly superior with SAFIRE than with FBP ( P  < 0.01), without significant difference between FBP at 100 kVp and SAFIRE at 80 kVp ( P  = 0.68). Diagnostic image quality was present with FBP in 96% of images at 100 kVp and 88% at 80 kVp, and with SAFIRE in 100% at 100 kVp and 98% at 80 kVp. There were significantly more datasets with diagnostic image quality with SAFIRE than with FBP ( P  < 0.01). Mean CTDI vol and effective doses were 1.5 ± 0.7 mGy·cm and 0.7 ± 0.2 mSv at 100 kVp, and 1.4 ± 2.8 mGy·cm and 0.5 ± 0.2 mSv at 80 kVp ( P  < 0.001, both). Conclusions Use of SAFIRE in low-dose lung CT reduces noise, improves image quality, and renders more studies diagnostic as compared to FBP. Key Points • Low-dose computed tomography is an important thoracic investigation tool. • Radiation dose can be less than 1 mSv with iterative reconstructions. • Iterative reconstructions render more low-dose lung CTs diagnostic compared to conventional reconstructions.