Dose distribution for dental cone beam CT and its implication for defining a dose index

Abstract

6 Listing of partners on www.sedentexct.euObjectives: To characterize the dose distribution for a range of cone beam CT (CBCT) units, investigating different field of view sizes, central and off-axis geometries, full or partial rotations of the X-ray tube and different clinically applied beam qualities. The implications of the dose distributions on the definition and practicality of a CBCT dose index were assessed. Methods: Dose measurements on CBCT devices were performed by scanning cylindrical head-size water and polymethyl methacrylate phantoms, using thermoluminescent dosemeters, a small-volume ion chamber and radiochromic films. Results: It was found that the dose distribution can be asymmetrical for dental CBCT exposures throughout a homogeneous phantom, owing to an asymmetrical positioning of the isocentre and/ or partial rotation of the X-ray source. Furthermore, the scatter tail along the z-axis was found to have a distinct shape, generally resulting in a strong drop (90%) in absorbed dose outside the primary beam. Conclusions: There is no optimal dose index available owing to the complicated exposure geometry of CBCT and the practical aspects of quality control measurements. Practical validation of different possible dose indices is needed, as well as the definition of conversion factors to patient dose.

A retrospective, semi-quantitative image quality analysis of cone beam computed tomography (CBCT) and MSCT in the diagnosis of distal radius fractures

“…Unfortunately, exact dosage comparisons are not very straightforward as the CT dose index (CTDI) used to approximate the effective radiation dose of MSCT scans cannot directly be applied to CBCT scanners due to different beam geometry. To date, there is no widely accepted CTDI-like dose estimation for CBCT scanners [9,13,23,24]. While the radiation doses reported vary, the consensus is that the radiation dose of CBCT scans is lower than that of standard MSCT protocols yet significantly higher than that of plain radiography [25][26][27][28][29].…”

Movement characteristics in young patients and the impact on CBCT image quality

“…[1][2][3] In this context the word "lower" must be interpreted with caution, since there is no low-dose threshold to define the amount of radiation to be considered as safe. 4,5 This is a major concern, particularly when the patient is a child, children being consistently more susceptible to radiation than adults.…”

Evaluating the quality characteristics of TLD-100T and TLD-100H exposed to diagnostic X-rays and 64 multislice CT using Taguchi's quality loss function

“…Multiple applications of the two kinds of TLDs have received considerable attention. While using both kinds of TLDs, Pauwels and colleagues evaluated the effective dose for dental cone beam computed tomography (CT) (Pauwels et al, 2013). Those researchers also evaluated the dose distribution for dental CT with either acrylic or water phantom by using two kinds of TLDs as well (Pauwels et al, 2012).…”

“…While using both kinds of TLDs, Pauwels and colleagues evaluated the effective dose for dental cone beam computed tomography (CT) (Pauwels et al, 2013). Those researchers also evaluated the dose distribution for dental CT with either acrylic or water phantom by using two kinds of TLDs as well (Pauwels et al, 2012). By using TLD-100H, Changlaiet and colleagues evaluated the low background dose of environmental gamma exposure (Changlai et al, 2012).…”