Abstract
In CT, ionizing radiation exposure from the scan has attracted much concern from patients and doctors. This work is aimed at improving head CT images from low-dose scans by using a fast Dictionary learning (DL) based post-processing. Both Low-dose CT (LDCT) and Standard-dose CT (SDCT) nonenhanced head images were acquired in head examination from a multi-detector row Siemens Somatom Sensation 16 CT scanner. One hundred patients were involved in the experiments. Two groups of LDCT images were acquired with 50 % (LDCT50 %) and 25 % (LDCT25 %) tube current setting in SDCT. To give quantitative evaluation, Signal to noise ratio (SNR) and Contrast to noise ratio (CNR) were computed from the Hounsfield unit (HU) measurements of GM, WM and CSF tissues. A blinded qualitative analysis was also performed to assess the processed LDCT datasets. Fifty and seventy five percent dose reductions are obtained for the two LDCT groups (LDCT50 %, 1.15 ± 0.1 mSv; LDCT25 %, 0.58 ± 0.1 mSv; SDCT, 2.32 ± 0.1 mSv; P < 0.001). Significant SNR increase over the original LDCT images is observed in the processed LDCT images for all the GM, WM and CSF tissues. Significant GM–WM CNR enhancement is noted in the DL processed LDCT images. Higher SNR and CNR than the reference SDCT images can even be achieved in the processed LDCT50 % and LDCT25 % images. Blinded qualitative review validates the perceptual improvements brought by the proposed approach. Compared to the original LDCT images, the application of DL processing in head CT is associated with a significant improvement of image quality.
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Abbreviations
- LDCT:
-
Low-dose CT
- SDCT:
-
Standard-dose CT
- DL:
-
Dictionary learning
- K-SVD:
-
K-means singular value decomposition
- SD:
-
Standard deviation
- SNR:
-
Signal to noise ratio
- CNR:
-
Contrast to noise ratio
- CTDIvol :
-
Volume CT dose index
- DLP:
-
Dose length product
- ED:
-
Effective dose
- FBP:
-
Filtered back-projection
- mA:
-
Milliampere
- mAs:
-
Milliampere second
- HU:
-
Hounsfield unit
- ASIR:
-
Adaptive statistical iterative reconstruction
- PICCS:
-
Prior image constrained compressed sensing
- ROI:
-
Region of interest
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Acknowledgments
This research was supported by National Basic Research Program of China (2010CB732503), National Natural Science Foundation (81370040, 31100713), and the Natural Science Foundation of Jiangsu Province (BK2011593), This work was also supported by the Key Laboratory of Computer Network and Information Integration (Southeast University), Ministry of Education.
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Chen, Y., Shi, L., Yang, J. et al. Radiation dose reduction with dictionary learning based processing for head CT. Australas Phys Eng Sci Med 37, 483–493 (2014). https://doi.org/10.1007/s13246-014-0276-7
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DOI: https://doi.org/10.1007/s13246-014-0276-7