Comparison between effective radiation dose of CBCT and MSCT scanners for dentomaxillofacial applications

https://doi.org/10.1016/j.ejrad.2008.06.002Get rights and content

Abstract

Objectives

To compare the effective dose levels of cone beam computed tomography (CBCT) for maxillofacial applications with those of multi-slice computed tomography (MSCT).

Study design

The effective doses of 3 CBCT scanners were estimated (Accuitomo 3D®, i–CAT®, and NewTom 3G®) and compared to the dose levels for corresponding image acquisition protocols for 3 MSCT scanners (Somatom VolumeZoom 4®, Somatom Sensation 16® and M×8000 IDT®). The effective dose was calculated using thermoluminescent dosimeters (TLDs), placed in a Rando® Alderson phantom, and expressed according to the ICRP 103 (2007) guidelines (including a separate tissue weighting factor for the salivary glands, as opposed to former ICRP guidelines).

Results

Effective dose values ranged from 13 to 82 μSv for CBCT and from 474 to 1160 μSv for MSCT. CBCT dose levels were the lowest for the Accuitomo 3D®, and highest for the i-CAT®.

Conclusions

Dose levels for CBCT imaging remained far below those of clinical MSCT protocols, even when a mandibular protocol was applied for the latter, resulting in a smaller field of view compared to various CBCT protocols. Considering this wide dose span, it is of outmost importance to justify the selection of each of the aforementioned techniques, and to optimise the radiation dose while achieving a sufficient image quality. When comparing these results to previous dosimetric studies, a conversion needs to be made using the latest ICRP recommendations.

Introduction

During the last decade, there has been a tendency of using three-dimensional (3D) information to aid in dentomaxillofacial diagnostics and surgery planning [1], [2]. Conventional CT protocols are generally associated with relatively high radiation dose levels and even clinical protocols for multi-slice CT (MSCT) still show high doses [3], [4]. The introduction of Cone Beam Computed Tomography (CBCT) holds promising potential for oral and craniofacial imaging applications [5], [6], [7], [8]. Although the radiation dose of CBCT is generally lower than for MSCT, the use of CBCT may increase the collective radiation dose given for medical purposes disproportional to its frequency of justified utilisation. Therefore, there is a need for reference values for the effective radiation dose for protocols used in CBCT scanners.

Loubele et al. and Guerrero et al. reported radiation dose levels for different MSCTs and CBCTs and related the variation in dose levels to the resulting image quality for various exposure protocols [4], [5]. This is an essential relation, although most studies report on either image quality or dose levels. If one would strictly adhere to the ALARA principle, than it is required to try optimising image quality at reasonably low radiation dose levels [9], [10]. In a state-of-the-art report on CBCT, Scarfe et al. already discussed the need for optimisation [6]. Few recent studies examined radiation dose levels for CBCT [11], [12]. Dose levels varied amongst equipment, exposure protocols and applied methodology. Furthermore, no comparison to spiral CT and MSCT was made. From these data, it is obvious that there is a need for a standardised protocol for effective dose determination for both CBCTs and MSCTs, leading to comparative data which can be generated and reported. This can be accomplished by effective radiation dose estimations using a Rando® Alderson phantom [13], [14].

The objective of the present paper is to compare the effective doses of 3 CBCTs for maxillofacial applications with those of corresponding imaging protocols from 3 MSCTs.

Section snippets

Evaluated CBCT scanners

The following CBCTs were evaluated for radiation dose levels: Accuitomo 3D® (J. Morita Corporation, Kyoto, Japan), NewTom 3G® (Quantitative Radiology, Verona, Italy), and i-CAT® (Imaging Sciences International, Hatfield, Pennsylvania, USA) (Table 1).

The Accuitomo 3D® used in the present study works with an analogue detector. However, it should be noted that the newer Accuitomo 3D FPD® includes a flat panel detector (FPD) with advantages for both image quality and radiation dose levels [15]. The

Results

Table 3A shows the effective dose for the different acquired regions, along with the relative organ distribution of the dose of the Accuitomo 3D® and i-CAT®. Table 3B shows the effective dose and organ distribution for two additional protocols of the i-CAT® and for the NewTom 3G®.

For the Accuitomo 3D®, the highest effective dose is found for the premolar and canine upper jaw region (44 μSv) and the lowest effective dose for the front lower jaw region (13 μSv). The red bone marrow absorbs the

Discussion

As demonstrated before, the introduction of Cone Beam Computed Tomography (CBCT) holds promising potential for oral and craniofacial imaging applications [5], [6], [7], [8]. The radiation dose of different CBCT scanners was compared with different MSCT scanners. The radiation dose was evaluated by effective dose measurements on Rando® Alderson phantoms.

A huge difference in effective dose between CBCT and MSCT can be observed, with effective dose ratio's up to 90. However, especially for the

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