Evaluation of automatic tube current modulation in a CT scanner using a customised homogeneous phantom

Area of Science:

• Medical Imaging
• Radiological Physics

Background:

• Automatic tube current modulation (ATCM) in CT scanners creates complex interactions between scanner settings, patient anatomy, radiation dose, and image quality.
• Understanding these relationships is crucial for optimizing CT protocols and ensuring patient safety.

Purpose of the Study:

• To develop mathematical models capable of predicting CT radiation dose and image noise.
• To establish models based on attenuating diameter and all relevant scanner parameters for ATCM systems.

Main Methods:

• A homogenous phantom was used to test ATCM on a Philips CT scanner.
• Data was extracted from DICOM images using a MATLAB script.
• R statistical software was employed for data analysis, plotting, and regression modeling.

Main Results:

• Models for tube current and noise were developed with high adjusted R-squared values (0.965 and 0.912, respectively).
• Analysis revealed significant impacts of tube potential, DoseRight Index (DRI), helical pitch, rotation time, and detector collimation on tube current and noise.
• For example, increasing DRI from 12 to 24 at a 24 cm diameter increased mA by 294% and decreased noise by 46%.

Conclusions:

• The developed models provide accurate predictions of radiation dose and image quality for specific patient sizes and scanner configurations.
• These models serve as a practical tool for imaging professionals to optimize CT scan protocols, balancing radiation dose and image quality objectives.