Measurement of skin dose from cone-beam computed tomography imaging

Kenneth M Abramovitch,Sercan Akyalcin,Jeryl D English,Xiujiang J Rong

doi:10.1186/1746-160x-9-28

Abstract

ObjectiveTo measure surface skin dose from various cone-beam computed tomography (CBCT) scanners using point-dosimeters.Materials & methodsA head anthropomorphic phantom was used with nanoDOT optically stimulated luminescence (OSL) dosimeters (Landauer Corp., Glenwood, IL) attached to various anatomic landmarks. The phantom was scanned using multiple exposure protocols for craniofacial evaluations in three different CBCT units and a conventional x-ray imaging system. The dosimeters were calibrated for each of the scan protocols on the different imaging systems. Peak skin dose and surface doses at the eye lens, thyroid, submandibular and parotid gland levels were measured.ResultsThe measured skin doses ranged from 0.09 to 4.62 mGy depending on dosimeter positions and imaging systems. The average surface doses to the lens locations were ~4.0 mGy, well below the threshold for cataractogenesis (500 mGy). The results changed accordingly with x-ray tube output (mAs and kV) and also were sensitive to scan field of view (SFOV). As compared to the conventional panoramic and cephalometric imaging system, doses from all three CBCT systems were at least an order of magnitude higher.ConclusionsPeak skin dose and surface doses at the eye lens, thyroid, and salivary gland levels measured from the CBCT imaging systems were lower than the thresholds to induce deterministic effects. However, our findings do not justify the routine use of CBCT imaging in orthodontics considering the lifetime-attributable risk to the individual.

Highlights

A three-dimensional radiographic examination of the craniofacial skeleton with cone beam computed tomography (CBCT) is indicated for a number of clinical conditions
Peak skin dose and surface doses at the eye lens, thyroid, and salivary gland levels measured from the CBCT imaging systems were lower than the thresholds to induce deterministic effects
Our findings do not justify the routine use of CBCT imaging in orthodontics considering the lifetime-attributable risk to the individual

Summary

Introduction

A three-dimensional radiographic examination of the craniofacial skeleton with cone beam computed tomography (CBCT) is indicated for a number of clinical conditions. Like any x-ray exposure, CBCT scans expose the patient to certain biologic risks of radiation. CTDI is a dose descriptor, not a direct measurement of patient dose Because it is measured by using a standardized, homogeneous, cylindrical phantom, it questionably represents the dose for objects of substantially different size, shape, or attenuation, like the human body [7]. In order to determine the dose to a point within the scan volume, a point (small) dosimeter is required. For such evaluations optically stimulated luminescence (OSL) ‘dot’ dosimeters, thermoluminescent dosimeters (TLDs), small solid-state detectors, and metal oxide semiconductor field-effect transistors (MOSFET) have been used.

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