0° Vs. 180° CT Localiser: The Effect of Vertical Off-centring, Phantom Positioning and Tube Voltage on Dose Optimisation in Multidetector Computed Tomography

Overview

Journal J Med Radiat Sci

Specialties Nuclear Medicine
Radiology

Date 2021 Aug 17

PMID 34402591

Citations 4

Authors

Yazan Al-Hayek

Xiaoming Zheng

Rob Davidson

Christopher Hayre

Dana Al-Mousa

Campbell Finlay

Kelly Spuur

Affiliations

Soon will be listed here.

Abstract

Introduction: Patient positioning is an essential consideration for the optimisation of radiation dose during CT examinations. The study objectives seek to explore the effects of vertical off-centring, localiser direction (0° and 180°), and phantom positioning (supine and prone) on radiation dose, using three different tube voltages in multidetector computed tomography (MDCT) imaging.

Methods: The trunk of a PBU-60 anthropomorphic phantom was imaged using a Discovery CT750 HD - 128 slice (GE Healthcare). Images employing 0° and 180° localisers were acquired in supine and prone orientation for each combination of vertical off-centring (±100, ±60 and ±30 mm) and different tube voltages (80, 120 and 140 kVp), using the system's automatic tube current modulation (ATCM) function. The displayed volume CT dose index (CTDI ) and dose length product (DLP) were recorded.

Results: With incremental table off-centring of ±100 mm, the dose at 120 kVp in the supine position ranged from 63% to 196% (0° localiser) and from 66% to 191% (180° localiser) as compared to iso-centre. While in the prone position, the dose ranged from 62% to 195% (0° localiser); and 62% to 193% (180° localiser), with a notable dose increase at higher tube voltages. Dose variation and vertical off-centring showed a significant relationship for both 0° and 180° localisers (r = 0.94 and 0.96, respectively, P < 0.001). The CTDI variation between supine and prone phantom positions at ±100 mm off-centring was 0.22 mGy (2.9%), and 0.19 mGy (2.3%) when the 0° and 180 ° localisers were utilised, respectively.

Conclusions: Phantom off-centring and localiser direction evidenced large dose variation. It is recommended that the 0° localiser is employed during CT examinations, in order to minimise the potential additional radiation dose which may result from off-centring and the use of lower tube voltages where clinically appropriate.

Citing Articles

Automatic patient centering in computed tomography: a systematic review and meta-analysis.

Hadi Y, Keaney L, England A, Moore N, McEntee M Eur Radiol. 2024; .

PMID: 39570368 DOI: 10.1007/s00330-024-11170-z.

The Impacts of Vertical Off-Centring, Localiser Direction, Phantom Positioning and Tube Voltage on CT Number Accuracy: An Experimental Study.

Al-Hayek Y, Spuur K, Davidson R, Hayre C, Zheng X J Imaging. 2022; 8(7).

PMID: 35877619 PMC: 9316438. DOI: 10.3390/jimaging8070175.

Impacts of Phantom Off-Center Positioning on CT Numbers and Dose Index CTDIv: An Evaluation of Two CT Scanners from GE.

Zheng X, Gutsche L, Al-Hayek Y, Stanton J, Elshami W, Jensen K J Imaging. 2021; 7(11).

PMID: 34821866 PMC: 8625132. DOI: 10.3390/jimaging7110235.

0° vs. 180° CT localiser: The effect of vertical off-centring, phantom positioning and tube voltage on dose optimisation in multidetector computed tomography.

Al-Hayek Y, Zheng X, Davidson R, Hayre C, Al-Mousa D, Finlay C J Med Radiat Sci. 2021; 69(1):5-12.

PMID: 34402591 PMC: 8892417. DOI: 10.1002/jmrs.535.

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