Testing the impact of two key scan parameters on the quality and repeatability of measurements from CT scan data

Computed tomographic (CT) scanning is becoming a popular research tool across earth and life sciences. However, despite its prominence, there have not been systematic investigations into how CT scan parameters affect data quality and reproducibility. Here we conduct two sets of trials to test how exposure time, the number of x-ray radiographs averaged per view, and overall scan time affect the quality of CT scan data, assessed using signal and contrast to noise ratios and the repeatability of measurements derived from these data, in this case the calculated volume of pteropod shells. We find that contrast to noise ratio and calculated shell volume increase and the variability in shell volume measurements decrease with increasing overall scan time. However, the benefits of increased overall scan time diminish considerably at scan times of 50 minutes or more. Furthermore, as overall scan time increases, scans are at greater risk of being affected by sample movement, which can make the data unusable. By balancing exposure time and the number of x-ray radiographs averaged per view, the image quality in a 50-minute scan can be comparable to, or better than, that collected in a 75-minute scan. By selecting a 50-minute rather than a 75-minute scan, data collection can be increased by between 66 and 75%, maximizing both the quantity and quality of CT data collected.