Background and Aims. The purpose of this study was to examine the influence of the scanner type, reconstructed slice thickness and subjective image quality on precision of bone length measurements in multi-detector computed tomography (MDCT).
Materials and Methods. Twenty dry long bones were scanned on two MDCT units, GE LightSpeed Ultra, 8 detector rows and GE LightSpeed VCT, 64 detector rows using reconstructed slice thickness of 0.625 and 1.25 mm. Four observers evaluated the subjective image quality and maximum bone length. Conventional caliper bone length measurements served as ground truth.
Results and Conclusions. Measurements on the 64-row scanner were more precise than on the 8-row scanner. However, slice thickness did not seem to have any effect on the precision of measurements. Nevertheless, differences are small and may be correlated to minimal physical detector resolution in the Z-axis. Subjective image quality was best at the 64-row scanner with 0.625 mm reconstructed slice thickness (full-isotropy) and worst at the 64-row scanner with 1.25 mm (anisotropy). The depiction of small structures such as trabecular bone was best at isotropic voxel size. Subjective image quality had no influence on bone length measurement precision.