Optimization of Low-Dose CT Protocols for Lung Cancer Screening: A Comprehensive Analysis Using Clinical and Phantom Data

Pichan Kaewpookum; Natthida  Malithong; Sitthiluck Luckhan; Siranat Butalome; Korndech Pattanasittiwong

Authors

Pichan Kaewpookum Ramkhamhaeng University
Natthida Malithong Division of Radiological Technology, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand
Sitthiluck Luckhan Division of Radiological Technology, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand
Siranat Butalome Division of Radiological Technology, Faculty of Science, Ramkhamhaeng University, Bangkok, Thailand
Korndech Pattanasittiwong Radiology department, Phayathai Nawamin Hospital, Bangkok, Thailand

Keywords:

CT protocol optimization, Low-dose CT, iterative reconstruction, lung cancer screening, Hounsfield Unit accuracy

Abstract

Abstract

Objective: To optimize Low-Dose Computed Tomography (LDCT) protocols for lung cancer screening by evaluating radiation dose, image quality, and the accuracy of Hounsfield Unit (HU) measurements across various technical settings.

Methods: The study compared clinical data with phantom experiments. Clinical analysis was performed on 190 patients (95 standard-dose and 95 low-dose CT) scanned with a 128-slice CT system. Radiation metrics (CTDIvol, DLP, SSDE, and Effective Dose) and image quality (SNR, CNR, and noise) were recorded. In the experimental phase, a CT Tissue Equivalent (TE) phantom with 18 tissue-mimicking inserts was scanned using nine different protocols (mA: 11–350; kV: 70–140) to determine the correlation between electron density and CT numbers.

Results: The LDCT protocols achieved a radiation dose reduction of over 70% compared to standard-dose protocols (p < 0.05). Although image noise increased at lower doses, CNR and SNR remained clinically acceptable for screening purposes. Phantom analysis demonstrated a strong linear correlation (R² > 0.99) between electron density and CT numbers across all protocols. Two specific settings, 22 mA/120 kV and 30 mA/100 kV, were identified as the most effective for balancing dose reduction with quantitative accuracy.

Conclusion: Optimized LDCT protocols can significantly reduce radiation exposure while maintaining the reliability of CT numbers. The use of a tissue-equivalent phantom is a valid method for establishing screening protocols that adhere to the ALARA principle. However, a visual assessment of image quality is recommended to ensure that diagnostic clarity and essential anatomical details are preserved before these optimized protocols are implemented in routine screening.

Keywords: Low-Dose CT (LDCT), Optimization, Lung Cancer Screening, Radiation Dose, Image Quality, CT Tissue Equivalent Phantom.

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