Computed tomography imaging with the Adaptive Statistical Iterative Reconstruction (ASIR) algorithm: dependence of image quality on the blending level of reconstruction

Abstract

Computed tomography (CT) is a useful and widely employed imaging technique, which represents the largest source of population exposure to ionizing radiation in industrialized countries. Adaptive Statistical Iterative Reconstruction (ASIR) is an iterative reconstruction algorithm with the potential to allow reduction of radiation exposure while preserving diagnostic information. The aim of this phantom study was to assess the performance of ASIR, in terms of a number of image quality indices, when different reconstruction blending levels are employed. CT images of the Catphan-504 phantom were reconstructed using conventional filtered back-projection (FBP) and ASIR with reconstruction blending levels of 20, 40, 60, 80, and 100%. Noise, noise power spectrum (NPS), contrast-to-noise ratio (CNR) and modulation transfer function (MTF) were estimated for different scanning parameters and contrast objects. Noise decreased and CNR increased non-linearly up to 50 and 100%, respectively, with increasing blending level of reconstruction. Also, ASIR has proven to modify the NPS curve shape. The MTF of ASIR reconstructed images depended on tube load/contrast and decreased with increasing blending level of reconstruction. In particular, for low radiation exposure and low contrast acquisitions, ASIR showed lower performance than FBP, in terms of spatial resolution for all blending levels of reconstruction. CT image quality varies substantially with the blending level of reconstruction. ASIR has the potential to reduce noise whilst maintaining diagnostic information in low radiation exposure CT imaging. Given the opposite variation of CNR and spatial resolution with the blending level of reconstruction, it is recommended to use an optimal value of this parameter for each specific clinical application.

Feasibility of bronchial wall quantification in low‐ and ultralow‐dose third‐generation dual‐source CT: An ex vivo lung study

“…In our study, ADMIRE 5 resulted in improved SNR and lower noise in comparison to ADMIRE 1 and 3 with the same radiation dose, which confirms results from previous studies 13,36 . Although the ADMIRE strength of 5 possibly had a higher amount of noise reduction, blocky appearance (losing detail in the image) of higher strength IR 30,37 was not observed in our study, which may due to ADMIRE’s excellent noise reduction potential, the technology adopts a "statistical model" and iterative decoding chip to integrate the statistical data of virtual data domain, image domain, and model domain efficiently 38 . Through multiple iterations, the artifact was removed and the noise was reduced to achieve real‐time high‐definition iterative imaging 38 .…”

Impact of increasing levels of adaptive statistical iterative reconstruction on image quality in oil-based postmortem CT angiography in coronary arteries

“…Lack of familiarity of the image appearance might cause missing diagnoses, since the radiologist might misinterpret manifestations or structures, which appear different with different IR levels or vendors. The optimal IR level might differ between different types of CT examinations and should be evaluated when establishing a standard protocol [ 20 ]. In our study, objective image quality increased significantly with higher levels of IR due to the decreasing image noise (Fig.…”

“…Because the higher radiation dose in PMCT results in less image noise compared to clinical routine CT, optimal IR levels for noise suppression may differ between PMCT and clinical CT examinations. Further, the IR level specifically needs to be evaluated for different PMCT protocols (e.g., PMCT of the coronary arteries) in terms of quantitative and qualitative image quality [ 20 ]. For this purpose, we aimed to investigate the impact of different levels of IR on the objective and subjective image quality in PMCTA.…”

Patient Safety in Radiology

“…Moreover, particular attention should be given to ensure that radiation dose variability is minimized in patients undergoing repeat CT examination [17]. Because of the strict correlation between image noise and radiation expo-sure, the iterative reconstruction approach has the potential to be employed with data acquired at lower radiation doses while preserving clinical information [18].…”