Influence of Different Arm Positions in the Localizer Radiograph(s) on Patient Dose during Exposure-Controlled CT Examinations of the Neck to Pelvis.

Tony M Svahn,Jennifer C Ast,Lovre Peric

doi:10.3390/tomography7030028

Tony M Svahn, Jennifer C Ast + Show 1 more

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https://doi.org/10.3390/tomography7030028

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Abstract

Our aim was to examine the impact of different arm positions during imaging of the localizer radiograph(s) on effective dose for exposure-controlled computed tomography (CT) (Siemens/Canon) scans of the neck to pelvis. An anthropomorphic whole-body phantom was scanned from the neck to pelvis with the arms positioned in three different ways during the acquisition of the localizer radiograph: (i) above the head, (ii) alongside the trunk, and (iii) along the trunk with the hands placed on the abdomen. In accordance with clinical routines, the arms were not included in the subsequent helical scans. Effective doses were computed to a standard-sized patient (male/female) using a dedicated system-specific Monte Carlo-based software. Effective doses for the Canon CT scanner for the different alternatives (male/female) were (a) 5.3/6.62 mSv, (b) 5.62/7.15 mSv and (c) 5.92/7.44 mSv. For the Siemens CT scanner, effective doses were (a) 4.47/5.59 mSv, (b) 5.4/6.69 mSv and (c) 5.7/6.99 mSv. Arms placed above the head during localizer radiograph imaging in the current CT procedures substantially reduced the total effective dose to the patient.

Highlights

The increased use of computed tomography (CT) is a concern because of potential risks associated with ionizing radiation
Concerning automatic exposure control (AEC) modulation, one aspect is that the positioning of the arms during localizer radiograph imaging may affect the resulting dose to the patient because the modulation depends on the attenuation information of the patient in the localizer radiograph(s) [13]
Having the arms raised during localizer radiograph(s) may result in an increase of the effective dose due to the thyroid and other relevant radiosensitive organs located above the shoulders

Summary

Introduction

The increased use of computed tomography (CT) is a concern because of potential risks associated with ionizing radiation. It estimates potential radiation hazards by taking into account the stochastic risks of cancer induction by summing organ exposure to ionizing radiation weighed against susceptibility of the specific tissues (i.e., adjusting for organs’ different sensitivity) to radiation damage. One approach for estimating effective dose is to apply global conversion factors multiplied by the dose length product (DLP) [11]. These are not systemspecific and do not account for manufacturer/model-specific details such as varying design in beam-shaping filter, over-ranging effects, scanner geometry, etc. The task can be regarded as organ-based dose optimization

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