Impact of reconstruction techniques on low dose chest CT image quality: comparison of FBP, Clear View at Mzuzu Central Hospital, Malawi

Hui Zhang¹, Blessed Kondowe², Jiaojiao Zhang³, Xinming Xie⁴, Qiang Song⁵, Gang Niu¹, Jin Shang¹

1. Department of Medical Imaging, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, PR China
2. Radiology Department, Mzuzu Central Hospital, Mzuzu, Malawi
3. Department of Pathology, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, PR China
4. Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, PR China
5. Department of Cardiovascular Medicine, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, PR China

*Corresponding Author: Jin Shang; E-mail: shangjin01@qq.com

Abstract
Objective
To investigate the impact of two reconstruction techniques, Filtered Back Projection (FBP) and Clear View (CV) iterative algorithm, on the image quality of low-dose thin-slice chest CT.
Methods
A retrospective study of 42 patients undergoing low-dose chest CT at Mzuzu Central Hospital from Feb-Apr 2024 used automatic tube current modulation at 120 kV. Raw data were reconstructed with FBP, 20% CV, 40% CV, 60% CV, and 80% CV, with 1 mm slice thickness and 0.625 mm spacing. Image noise, Signal-to-Noise Ratio (SNR), and Contrast-to-Noise Ratio (CNR) were measured, and image quality was rated on a 5-point scale for lung and mediastinal windows. Qualitative and quantitative parameters of the two different reconstruction algorithms in the five groups were comparatively analyzed.
Results
(1) Objective evaluation showed noise decreased in lung parenchyma, aorta, and erector spinae muscle with increasing CV weight. Mean noise reductions in lung parenchyma were 23.34% and 27.69% in 60% CV and 80% CV (P < 0.05). Aorta noise decreased by 23.43%, 37.16%, and 46.18% in 40% CV, 60% CV, and 80% CV (P < 0.05, P < 0.001, P < 0.001). Erector spinae muscle noise decreased by 35.91% and 44.78% in 60% CV and 80% CV (P < 0.05, P < 0.001). SNR and CNR were higher in CV groups than FBP. Among them, the differences in SNR between the 60% CV and 80% CV groups and the FBP group were statistically significant (P < 0.05). (2) Subjective scores for all groups were > 3, meeting diagnostic standards, with 60% CV yielding the highest lung and mediastinal window image quality (P < 0.05).
Conclusion
Compared to FBP, CV iterative reconstruction reduces noise and improves chest CT image quality under low-dose conditions as the weight increases, with 60% CV showing optimal performance.

Keywords: Iterative reconstruction algorithm; Low-dose; Chest diseases; Computed Tomography; Radiation dose