Impact of miscentering on patient dose and image noise in x-ray CT imaging: phantom and clinical studies

Habibzadeh, M A; Ay, Mohammad Reza; Asl, A R Kamali; Ghadiri, H; Zaidi, Habib

doi:10.1016/j.ejmp.2011.06.002

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Title		Impact of miscentering on patient dose and image noise in x-ray CT imaging: phantom and clinical studies
Authors		Habibzadeh, M A Ay, Mohammad Reza Asl, A R Kamali Ghadiri, H Zaidi, Habib
Published in		Physica Medica. 2012, vol. 28, no. 3, p. 191-9
Abstract		The operation of the bowtie filter in x-ray CT is correct if the object being scanned is properly centered in the scanner's field-of-view. Otherwise, the dose delivered to the patient and image noise will deviate from optimal setting. We investigate the effect of miscentering on image noise and surface dose on three commercial CT scanners. Six cylindrical phantoms with different size and material were scanned on each scanner. The phantoms were positioned at 0, 2, 4 and 6 cm below the isocenter of the scanner's field-of-view. Regression models of surface dose and noise were produced as a function of miscentering magnitude and phantom's size. 480 patients were assessed using the calculated regression models to estimate the influence of patient miscentering on image noise and patient surface dose in seven imaging centers. For the 64-slice CT scanner, the maximum increase of surface dose using the CTDI-32 phantom was 13.5%, 33.3% and 51.1% for miscenterings of 2, 4 and 6 cm, respectively. The analysis of patients' scout scans showed miscentering of 2.2 cm in average below the isocenter. An average increase of 23% and 7% was observed for patient dose and image noise, respectively. The maximum variation in patient miscentering derived from the comparison of imaging centers using the same scanner was 1.6 cm. Patient miscentering may substantially increase surface dose and image noise. Therefore, technologists are strongly encouraged to pay greater attention to patient centering.
Keywords		Adolescent — Adult — Aged — Aged, 80 and over — Artifacts — Female — Humans — Male — Middle Aged — Patient Positioning — Phantoms, Imaging — Radiation Dosage — Tomography, X-Ray Computed/instrumentation — Young Adult
Identifiers		DOI: 10.1016/j.ejmp.2011.06.002 PMID: 21741870
Full text		Article (Published version) (951 Kb) - Free access
Structures		Faculté de médecine / Section de médecine clinique / Département de radiologie et informatique médicale
Research group		Imagerie Médicale (TEP et TEMP) (542)
Project		FNS: 31003A-135576
Citation (ISO format)		HABIBZADEH, M A et al. Impact of miscentering on patient dose and image noise in x-ray CT imaging: phantom and clinical studies. In: Physica Medica, 2012, vol. 28, n° 3, p. 191-9. https://archive-ouverte.unige.ch/unige:30800