Radiation dose reduction in CT of the brain: can advanced noise filtering compensate for loss of image quality?

Background Computed tomography (CT) of the brain is performed with high local doses due to high demands on low contrast resolution. Advanced algorithms for noise reduction might be able to preserve critical image information when reducing radiation dose. Purpose To evaluate the effect of advanced noise filtering on image quality in brain CT acquired with reduced radiation dose. Material and Methods Thirty patients referred for non-enhanced CT of the brain were examined with two helical protocols: normal dose (ND, CTDIvol 57 mGy) and low dose (LD, CTDIvol 40 mGy) implying a 30% radiation dose reduction. Images from the LD examinations were also postprocessed with a noise reduction software with non-linear filters (SharpView CT), creating filtered low dose images (FLD) for each patient. The three image stacks for each patient were presented side by side in randomized order. Five radiologists, blinded for dose level and filtering, ranked these three axial image stacks (ND, LD, FLD) as best to poorest (1 to 3) regarding three image quality criteria. Measurements of mean Hounsfield units (HU) and standard deviation (SD) of the HU were calculated for large region of interest in the centrum semiovale as a measure for noise. Results Ranking results in pooled data showed that the advanced noise filtering significantly improved the image quality in FLD as compared to LD images for all tested criteria. No significant differences in image quality were found between ND examinations and FLD. However, there was a notable inter-reader spread of the ranking. SD values were 15% higher for LD as compared to ND and FLD. Conclusion The advanced noise filtering clearly improves image quality of CT examinations of the brain. This effect can be used to significantly lower radiation dose.

[1]  G. Granlund.  In search of a general picture processing operator , 1978 .

[2]  P F Judy,et al.  LESION DETECTION AND SIGNAL-TO-NOISE RATIO IN CT IMAGES , 1981, Medical physics.

[3]  P. Hall,et al.  Effect of low doses of ionising radiation in infancy on cognitive function in adulthood: Swedish population based cohort study , 2004, BMJ : British Medical Journal.

[4]  Reduction in dose from CT examinations of liver lesions with a new postprocessing filter: a ROC phantom study , 2008, Acta radiologica.

[5]  S. Stein,et al.  Meta-Analysis of Cranial CT Scans in Children , 2008, Pediatric Neurosurgery.

[6]  K. Ledenius,et al.  Evaluation of image-enhanced paediatric computed tomography brain examinations. , 2010, Radiation protection dosimetry.

[7]  E Godehardt,et al.  [Dose reduction and image quality in MDCT of the upper abdomen: potential of an adaptive post-processing filter]. , 2010, RoFo : Fortschritte auf dem Gebiete der Rontgenstrahlen und der Nuklearmedizin.

[8]  Mikael Gunnarsson,et al.  Post-processing image filtration enabling dose reduction in standard abdominal CT. , 2010, Radiation protection dosimetry.

[9]  [Image quality in multidetector CT of paranasal sinuses: potential of dose reduction using an adaptive post-processing filter]. , 2010, RoFo : Fortschritte auf dem Gebiete der Rontgenstrahlen und der Nuklearmedizin.

[10]  Y. Funama,et al.  [Quantitative evaluation of calcium (content) in the coronary artery using hybrid iterative reconstruction (iDose) algorithm on low-dose 64-detector CT: comparison of iDose and filtered back projection]. , 2011, Nihon Hoshasen Gijutsu Gakkai zasshi.

[11]  C. Fink,et al.  Coronary CT angiography: image quality, diagnostic accuracy, and potential for radiation dose reduction using a novel iterative image reconstruction technique—comparison with traditional filtered back projection , 2011, European Radiology.

[12]  Jacques Felblinger,et al.  CT image quality improvement using adaptive iterative dose reduction with wide-volume acquisition on 320-detector CT , 2012, European Radiology.

[13]  Anne Catrine Trægde Martinsen,et al.  Iterative reconstruction reduces abdominal CT dose. , 2012, European journal of radiology.