Dosimetry of a cone beam CT device for oral and maxillofacial radiology using Monte Carlo techniques and ICRP adult reference computational phantoms

Abstract

Objectives: The aim of this study was to calculate organ and effective doses for a range of available protocols in a particular cone beam CT (CBCT) scanner dedicated to dentistry and to derive effective dose conversion factors. Methods: Monte Carlo simulations were used to calculate organ and effective doses using the International Commission on Radiological Protection voxel adult male and female reference phantoms (AM and AF) in an i-CAT CBCT. Nine different fields of view (FOVs) were simulated considering full-and half-rotation modes, and also a high-resolution acquisition for a particular protocol. Dose-area product (DAP) was measured. Results: Dose to organs varied for the different FOVs, usually being higher in the AF phantom. For 360°, effective doses were in the range of 25-66 mSv, and 46 mSv for full head. Higher contributions to the effective dose corresponded to the remainder (31%; 27-36 range), salivary glands (23%; 20-29%), thyroid (13%; 8-17%), red bone marrow (10%; 9-11%) and oesophagus (7%; 4-10%). The high-resolution protocol doubled the standard resolution doses. DAP values were between 181 mGy cm 2 and 556 mGy cm 2 for 360°. For 180°protocols, dose to organs, effective dose and DAP were approximately 40% lower. A conversion factor (DAP to effective dose) of 0.130 6 0.006 mSv mGy 21 cm 22 was derived for all the protocols, excluding full head. A wide variation in dose to eye lens and thyroid was found when shifting the FOV in the AF phantom. Conclusions: Organ and effective doses varied according to field size, acquisition angle and positioning of the beam relative to radiosensitive organs. Good positive correlation between calculated effective dose and measured DAP was found. Dentomaxillofacial Radiology (2013) 42, 92555893. doi: 10.1259/dmfr/92555893Cite this article as: Morant JJ, Salvadó M, Hernández-Girón I, Casanovas R, Ortega R, Calzado A. Dosimetry of a cone beam CT device for oral and maxillofacial radiology using Monte Carlo techniques and ICRP adult reference computational phantoms.

Radiation exposure to foetus and breasts from dental X-ray examinations: effect of lead shields

“…Many studies of dosimetry in dental examinations focus on the effective dose and organ doses in the head and neck region. Some studies [24][25][26] also report that the dose to non-shielded breasts is negligible or, presumably, zero.…”

Imaging dose from cone beam computed tomography in radiation therapy

“…It also does not include the topic of dose delivered to patients as a result of CBCT in diagnostic radiology, cardiology, and dentistry. Recent papers by Kalendar [9] and Dougeni et al [10] provide a review of CT imaging doses in diagnostic radiology and other publications include dose values for Tomotherapy [11,12], C-arm CBCT [13], dental CBCT [14,15], and 4D CT systems [16].…”

Assessment of protocols in cone-beam CT with symmetric and asymmetric beams usingeffective dose and air kerma-area product

“…In the asymmetric beam or off-axis geometry, Fig. 2(a), organs such as the salivary glands and lymph nodes remain exposed to the direct beam only part of acquisition (Morant et al, 2013). On the other hand, these organs are exposed during the entire the image acquisition time at protocols that uses symmetric beam.…”