Effects of Variations in Imaging Parameters on Image Quality of Non Contrast Computed Tomography Scans of Brain: A Cross-sectional Study

Abstract

Introduction: The radiation dose absorbed during Computed Tomography (CT) investigation of the head, which could be reduced by altering the scan parameters, is of great concern considering the radiosensitive organs around this region. Aim: To investigate the relationship between variations in scan parameters and image quality in brain CT scanning. Materials and Methods: This was an experimental cross-sectional study conducted at a private diagnostic clinic in Enugu State, Nigeria, from September 2018 to February 2019 with a total sample size of 150. All adult patients who reported at the centre for non contrast CT of brain during the study period {but not limited to participants with Anteroposterior Circumference Diameter (APCD) 170-180 cm of brain} were selected using consecutive sampling method. The samples was divided into three groups, a control group and two experimental groups. Scan parameters such as kilovolts (kV), milliamperes (mA) and Gantry Rotation Time (GRT) varied across the three groups studied and the corresponding image parameters such as image noise, Contrast to Noise Ratio (CNR) and Signal to Noise Ratio (SNR) were obtained and statistically analysed using both descriptive and inferential statistics. Results: There were statistically significant correlations of image parameters with scan parameters Group I (control): (CNR: r=0.857, p-value <0.001; Image noise: r=0.206, p-value=0.125, and SNR: r=0.875, p-value <0.001) (CNR: r=0.857, p-value <0.001; Image noise: r=0.211, p=0.115 and Image noise: r=-0.164, p-value=0.124 and SNR: r=0.880, p-value <0.001) for mA and kV, respectively. Group II (CNR: r=0.744, p-value <0.001, Image noise: r=0.521, p-value=0.024, and SNR: r=0.765, p-value <0.001), (CNR=r=0.761, p-value <0.001, Image noise: r=0.241, p-value=0.011 and SNR: r=0.780, p-value p=0.024) for mA and GRT, respectively. Group III (CNR: r=0.684, p-value=0.032; Image noise: r=0.646, p-value=0.032 and SNR: r=0.664, p-value=0.001) for mA. There was statistically significant relationship between scan parameters and radiation does parameters across all the sub groups at p-value <0.05. Conclusion: Altering the scan parameters (mA, kV and GRT) during CT brain investigation has tremendous effects on the image quality, particularly on the image noise and also on the radiation dose received by the patients.