The impact of integrated circuit detector technology in routine MDCT: Improved image quality compared to conventional detector design for constant SSDE

Khoschy Schawkat, Ralph M. Fischer, Johannes T. Heverhagen, Andreas Christe


Purpose: The aim of this study was to compare the image quality and radiation dose of routine CT scans acquired with a third-generation scanner built with integrated circuit detector technology (Stellar®-detector) to those acquired with a conventional solid-state detector (UFC-ultra fast ceramic solid-state detector) equipped with a discrete system using the same protocol setting on the same 128-MDCT scanner.

Material and Methods: 262 routine CT examinations of 240 patients (140 male, 100 female) with a mean age of 61.7 years (range: 20-89 years) were reviewed retrospectively. 131 examinations were acquired with a UFC solid-state detector and 131 with the new digital Stellar®-detector (23 CT chest and abdomen, 50 CT chest and 58 CT abdomen). The following parameters were recorded: BMI, scan length, kVp, CT dose index (CTDIvol) and dose-length-product (DLP). CTDIvol multiplied with a conversion factor depending on the patient size determined the size-specific dose estimates (SSDE). The image noise was defined as standard deviation of mean attenuation values in Hounsfield units and was quantitatively assessed by circular region of interest at predefined size of 31.4 mm2 (20 mm diameter) manually placed in the center of the left liver lobe. Iterative reconstruction (SAFIRE, level 3) was used.

Results: Changing the detector unit from a UFC solid-state detector with distributed electronics (conventional) to a fully-digital Stellar® detector leads to a significant decrease of image noise by 7.5% in the liver (mean ± SD: 25.5 ± 5.4 HU vs. 23.6 ± 5.8 HU; p=0.0019) for all CT scans included in this study. In the subgroup CT chest (n=100) the average noise reduction was 6% (mean ± SD: 28.2 ± 5.7 HU vs. 26.5 ± 7.1 HU; p=0.038) and 6,4% for the subgroup CT abdomen (n=116) (mean ± SD: 23.2 ± 3.7 HU vs. 21.9 ± 3.7 HU; p=0.022). kVp, mAs and total scan length were the strongest predictors for effective dose (ED, p<0.0001) whereas SSDE shows a strong positive correlation with kV, mAs and effective diameter (p<0.0001). The liver noise correlates negatively with both ED as well as SSDE (p=0.0002 and p<0.0001, respectively).

Conclusion: For the same applied radiation level the implementation of an integrated circuit digital detector reduces image noise compared to detectors having distributed electronics. Using a detector with integrated circuit detector technology provides great potential to reduce radiation dose. Further measures such as changing the CT-image noise level must be performed to achieve dose reduction.


tomography, x-ray computed/instrumentation; multidetector; radiation dosage; effective dose; size specific dose estimate

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