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SU‐FF‐I‐30: Image Quality and Dose Trends in Tube‐Current Modulated Multi‐Detector CT Imaging
Author(s) -
Fisher R,
Hintenlang D,
Arreola M
Publication year - 2007
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2760407
Subject(s) - imaging phantom , image quality , detector , scanner , flat panel detector , modulation (music) , materials science , tube (container) , nuclear medicine , biomedical engineering , optics , physics , medicine , acoustics , image (mathematics) , computer science , artificial intelligence , composite material
Purpose: This project quantifies image quality and dose trends in a multi‐detector CT system incorporating a tube‐current modulation system. Method and Materials: An elliptical phantom series constructed of a tissue‐equivalent pliable polyurethane elastomer material was used to test tube‐current modulation systems of a Siemens 16 slice CT scanner equipped with CareDose4D. A composite phantom comprised of elliptical segments of varying dimensions evaluated image quality and dose for both in‐plane and z‐axis tube‐current modulation. The standard deviation of CT number was recorded in reconstructed images in the slice plane as well as along the z‐axis of the scan in order to evaluate image quality at specific locations in the phantom. Image quality was compared for tube‐current modulated versus fixed tube‐current scans. CTDIw measurements were made with and without tube‐current modulation using a CTDI head phantom modified by the addition of elliptical phantom segments in order to independently evaluate the potential dose savings of tube‐current modulation. Results: CTDIw was invariant for scans with and without tube‐current modulation, an effect attributed to the inadequacy of CTDIw to adequately characterize dose for helical MDCT scanning modes. Image quality with tube‐current modulation was uniform along the entire scan length. Comparable scans with fixed tube‐current techniques showed variations in image quality of up to 40% along the z‐axis of the scan, and dose increases of up to 35%. In‐plane image quality measurements showed a trend towards larger variation in CT number towards the center of the phantom. The use of tube‐current modulation was demonstrated to reduce the effects of variable tissue thickness and geometry on image quality. Conclusion: Tube‐current modulation in CT provides more uniform image noise throughout the patient scan length while reducing dose as compared to fixed‐current techniques. Weighted CTDI is not an adequate measure of dose in comparing modulated to fixed‐current techniques.