Reduction of effective and Reduction of effective and organ dose to the eye lens organ dose to the eye lens in cerebral MDCT scans in cerebral MDCT scans using iterative image using iterative image reconstruction reconstruction Zizka J, Jandura J, Kvasnicka T, Zizka J, Jandura J, Kvasnicka T, Klzo L, Grepl J Klzo L, Grepl J Dept. of Radiology Dept. of Radiology Charles University Teaching Hospital Charles University Teaching Hospital Hradec Kralove Hradec Kralove Czech Republic Czech Republic ECR 2012 ECR 2012
Reduction of effective and organ dose to the eye lens in cerebral MDCT scans using iterative image reconstruction. Zizka J, Jandura J, Kvasnicka T, Klzo L, Grepl J Dept . of Radiology Charles University Teaching Hospital Hradec Kralove Czech Republic. ECR 2012. - PowerPoint PPT Presentation
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Reduction of effective and organ dose Reduction of effective and organ dose
to the eye lens in cerebral MDCT scans to the eye lens in cerebral MDCT scans
using iterative image reconstructionusing iterative image reconstruction
– effective dose calculated by ImPACT softwareeffective dose calculated by ImPACT software
– organ dose to the lens was derived from the actual tube current-time product organ dose to the lens was derived from the actual tube current-time product
value applied to the slices with lens includedvalue applied to the slices with lens included
– image noise (SD) in a 1.5 cmimage noise (SD) in a 1.5 cm22 ROI in the centrum semiovale ROI in the centrum semiovale
• qualitative visual assessment: two experienced radiologists blinded qualitative visual assessment: two experienced radiologists blinded to the type of image reconstruction using a visual analogue scaleto the type of image reconstruction using a visual analogue scale
• eye lens radiosensitivity is higher than previously thought eye lens radiosensitivity is higher than previously thought • the lens is frequently exposed to the primary beam in the lens is frequently exposed to the primary beam in
spiral MDCT scansspiral MDCT scans• the organ dose to the lens leading to cataract formation the organ dose to the lens leading to cataract formation
(0.5 Gy) might be acquired in as low as 7 (!) non-(0.5 Gy) might be acquired in as low as 7 (!) non-optimized CT head scans (CTDI ≈ 60 mGy)optimized CT head scans (CTDI ≈ 60 mGy)
• with optimized iterative reconstruction acquisition the with optimized iterative reconstruction acquisition the number of CT head scans leading to lens opacities number of CT head scans leading to lens opacities formation rises approx. 3-fold (20 MDCT head scans)formation rises approx. 3-fold (20 MDCT head scans)
DiscussionDiscussion
• even in the settings of optimized FBP based CT even in the settings of optimized FBP based CT
protocols, iterative reconstruction is capable of protocols, iterative reconstruction is capable of
further substantial radiation dose savings which, further substantial radiation dose savings which,
in our population, further reduced both the in our population, further reduced both the
effective and eye lens dose by more than 33 % effective and eye lens dose by more than 33 %
compared to optimized FBP protocols and by 58 compared to optimized FBP protocols and by 58
% compared to reference standard% compared to reference standard