Noise Reduction in Abdominal Computed Tomography Applying Iterative Reconstruction (ADMIRE).
The study aimed to compare image quality of filtered back projection (FBP) and iterative reconstruction (advanced modeled iterative reconstruction, ADMIRE) in contrast-enhanced computed tomography (CT) of the abdomen, and to assess the differences of reconstructions according to these methods. It also aimed to investigate the potential for noise reduction of ADMIRE for different reconstructed slice thicknesses.



CT data of the abdomen and pelvis were acquired using a 128-slice single-source CT system using automated kV selection and tube current adaption based on patients' anatomy. Raw data sets from patients scanned at 100 kV were selected, and images were reconstructed with slice thicknesses of 1 mm, 3 mm, and 5 mm, both with FBP and ADMIRE. Filter strength F1, F3, and F5 of the ADMIRE algorithm and the corresponding reconstruction kernels were used. In total, 58 raw data sets from 17 patients were used to reconstruct from the same raw data FBP and ADMIRE images, representing identical body regions. Identical regions of interest were placed at the same position of up to four images and image noise was measured. Differences of reconstructed images and detail preservation were tested using an image subtraction technique, and subjective image quality was assessed using a 5-point Likert scale.



On average, for 1-mm slice thickness, noise reduction was 9.15% ± 2.4% with filter strength level F1, 30.2% ± 3.4% with F3, and 54.4% ± 7.0% with F5 as compared to FBP. For a slice thickness of 3 mm, noise reduction was 8.5% ± 3.7% with F1, 28.6% ± 3.9% with F3, and 52.2% ± 9.1% with F5. For 5 mm, the corresponding values are 8.9% ± 2.7%, 31.4% ± 2.8%, and 52.7% ± 7.7%. On subtraction images, edge information of tissue classes with a high attenuation gradient was found, but structures with small differences in attenuation were not detectable on subtraction images, confirming that no relevant details were lost in the iterative reconstruction process.



ADMIRE is able to reduce image noise considerably (up to 50%) without any obvious negative impact on lesion depiction as assessed visually. Noise reduction of ADMIRE seems to be independent of slice thickness.
Department of Radiology, University Hospital Erlangen, Friedrich-Alexander-University-Erlangen-Nuremberg, Maximiliansplatz 1, D 91054, Erlangen, Germany. Electronic address: frank.schaller@yahoo.de.
Frank
F
Schaller
Siemens Healthcare, CT, Forchheim, Germany.
Martin
M
Sedlmair
Siemens Healthcare, CT, Forchheim, Germany.
Rainer
R
Raupach
Department of Radiology, University Hospital Erlangen, Friedrich-Alexander-University-Erlangen-Nuremberg, Maximiliansplatz 1, D 91054, Erlangen, Germany.
Michael
M
Uder
Department of Radiology and Nuclear Medicine, Klinikum Nuremberg, Paracelsus Medical University.
Michael
M
Lell
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D016477:Artifacts; D003287:Contrast Media; D006801:Humans; D008875:Middle Aged; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media
Computed tomography; iterative reconstruction; low tube voltage; noise reduction; radiation dose