Author: Corentin Desport, Dominique Iacchetti, Nicolas Kien, Ramiro Moreno, Melodie Munier, Séléna Pondard 👨🔬
Affiliation: Fibermetrix, Alara Expertise, Alara Group 🌍
Purpose: To evaluate the efficiency of organ-based tube current modulation (OBTCM) in thoracic and abdominopelvic Computed Tomography (CT) for different radiology departments and manufacturers. This study complements a previous one on head CT protocols.
Methods: Five CT scanners from four radiology departments were evaluated in this study. All scans were performed using routine abdominopelvic and thoracic protocols. A scintillating fiber optic detector was placed directly on the gantry to measure the tube exit dose and on the 32-cm BODY phantom to measure the surface dose. Image quality was quantified by measuring the signal-to-noise ratio (SNR) and the standard deviation of the Hounsfield units (HU) within circular regions of interest placed in the phantom. The measured values were compared on images with and without OBTCM.
Results: The study shows a maximum reduction in tube exit dose between 30% and 60% on the anterior part of the gantry using OBTCM. Maximum reduction in anterior phantom surface dose ranges between 30% and 55%. These variations depend on CT models and acquisition protocol used. Tube exit dose and phantom surface dose on the posterior part remains unchanged for GE and Canon CT scanners while it increases up to 40% for Siemens. Image noise and SNR increase by up to 25% in the seven CT scanners. Furthermore, differences in noise and SNR are statistically significant (p-value < 0.05).
Conclusion: Organ-based tube current modulation tools were effective to minimize x-ray dose. However, compared to the reference scan, OBTCM affects image quality, but the impact depends on the CT scanner. Defining a measurement protocol appears essential to assess the benefits and impacts of OBTCM tools.