The overall r2 value of .67 indicates that TIC might be useful for trend analysis of different groups of patients. However, for diagnostic interpretation, a r2 value of .53 might not meet the required accuracy of the study. Great care should be taken when TIC is applied to the cardiac patient. However, because the applied reference method was of significant influence, differences between TIC and the reference method are incorrectly attributed to errors in TIC alone.

No abstract

This study investigated the effect of different CT scanners, reconstruction protocols, scan positions, and air gaps on HU and/or calibrated calcium hydroxyapatite concentrations (CaHA). Phantoms containing bone-like materials were scanned on four different CT scanners. The effect of slice thickness, field of view (FOV) and reconstruction kernel on HU was investigated. Using clinical scan and reconstruction protocols and a calibration phantom, HU and CaHA were determined for different positions, and air gaps between phantom and calibration phantom. Changing reconstruction kernel considerably affected the HU (range −31 HU to 64 HU), whereas slice thickness and FOV did not. Inter-scanner differences in HU were <88 HU and decreased to <47 CaHA after calibration. Different positions of the phantom resulted in differences (on average up to −26 HU and −24 CaHA). An air gap of 2.5 cm atop the calibration phantom resulted in errors up to −41 CaHA. If absolute HU and calibrated CaHA are needed, different reconstruction kernels and changes in position within the FOV as well as air gaps should be avoided. RECEIVED

No abstract

TIC might be useful for trend analysis of different groups of patients. However, since the reference method was of significant influence, differences between TIC and the reference method are incorrectly attributed to TIC alone.