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Proceedings Paper

Dosimetric and image quality assessment of different acquisition protocols of a novel 64-slice CT scanner
Author(s): Cristina Vite; Monica Mangini; Sabina Strocchi; Raffaele Novario; Fabio Tanzi; Gianpaolo Carrafiello; Leopoldo Conte; Carlo Fugazzola
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Paper Abstract

Dose and image quality assessment in computed tomography (CT) are almost affected by the vast variety of CT scanners (axial CT, spiral CT, low-multislice CT (2-16), high-multislice CT (32-64)) and imaging protocols in use. Very poor information is at the moment available on 64 slices CT scanners. Aim of this work is to assess image quality related to patient dose indexes and to investigate the achievable dose reduction for a commercially available 64 slices CT scanner. CT dose indexes (weighted computed tomography dose index, CTDIw and Dose Length Product, DLP) were measured with a standard CT phantom for the main protocols in use (head, chest, abdomen and pelvis) and compared with the values displayed by the scanner itself. The differences were always below 7%. All the indexes were below the Diagnostic Reference Levels defined by the European Council Directive 97/42. Effective doses were measured for each protocol with thermoluminescent dosimeters inserted in an anthropomorphic Alderson Rando phantom and compared with the same values computed by the ImPACT CT Patient Dosimetry Calculator software code and corrected by a factor taking in account the number of slices (from 16 to 64). The differences were always below 25%. The effective doses range from 1.5 mSv (head) to 21.8 mSv (abdomen). The dose reduction system of the scanner was assessed comparing the effective dose measured for a standard phantom-man (a cylinder phantom, 32 cm in diameter) to the mean dose evaluated on 46 patients. The standard phantom was considered as no dose reduction reference. The dose reduction factor range from 16% to 78% (mean of 46%) for all protocols, from 29% to 78% (mean of 55%) for chest protocol, from 16% to 76% (mean of 42%) for abdomen protocol. The possibility of a further dose reduction was investigated measuring image quality (spatial resolution, contrast and noise) as a function of CTDIw. This curve shows a quite flat trend decreasing the dose approximately to 90% and a sharp fall below that value. A significant decrease in the effective dose to the patient, around 40%, was found; image quality analysis shows a further 10% dose reduction possibility.

Paper Details

Date Published: 3 March 2006
PDF: 7 pages
Proc. SPIE 6142, Medical Imaging 2006: Physics of Medical Imaging, 61423G (3 March 2006); doi: 10.1117/12.650618
Show Author Affiliations
Cristina Vite, Univ. Hospital of Insubria (Italy)
Monica Mangini, Univ. Hospital of Insubria (Italy)
Sabina Strocchi, Univ. Hospital of Insubria (Italy)
Raffaele Novario, Univ. of Insubria (Italy)
Fabio Tanzi, Univ. Hospital of Insubria (Italy)
Gianpaolo Carrafiello, Univ. of Insubria (Italy)
Leopoldo Conte, Univ. of Insubria (Italy)
Carlo Fugazzola, Univ. of Insubria (Italy)

Published in SPIE Proceedings Vol. 6142:
Medical Imaging 2006: Physics of Medical Imaging
Michael J. Flynn; Jiang Hsieh, Editor(s)

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