The purpose of this study was to assess the eye lens radiation dose in two adult virtual head voxel models for three different dental Cone Beam Computed Tomography (CBCT) imaging protocols via Monte Carlo (MC) simulations and examine the influence of the orbital bone density on the dose to the eye lenses.

A fully validated Monte Carlo framework, previously developed in our group, was used to model a Planmeca Promax 3D Max CBCT (Planmeca, Helsinki, Finland) system1,2. Simulations were performed with the Zubal and the ICRP reference female voxel phantoms3,4. Three different protocols were simulated to calculate the dose delivered to the eye lenses under different exposure conditions. A.Monte Carlo framework Our EGSnrc based MC framework was initially customized towards dosimetric applications3,4. It was adapted to enable the calculation of the energy imparted into predefined voxels and...

Tables 4 and 5 display the calculated lens doses for the six different in bone density versions of the Zubal and the ICRP female phantom respectively. The mineral density of a healthy bone is 1.92 g/cm3 according to ICRP 1104.

We calculated the dose to the eye lenses for different bone densities ranging from 2.2 g/cm3 (normal densities) to 1.2 g/cm3 (to account for variations in bone thickness, density and pathologies across population). The varying bone density has an immediate influence to the lens dose due to the bony orbit which encloses the eye bulb. Jaw protocol analysis highlights the shielding role of the orbit against scatter radiation. There is a substantial increase in the eye lens dose while density decreases from 2.2 to 1.2...

Andreas Stratis, Department of Imaging and Pathology, OMFS-IMPATH, KU Leuven email. [email protected]

[1] Zhang, G., Pauwels, R., Marshall, N., Shaheen, E., Nuyts, J., Jacobs, R., Bosmans, H., “Development and validation of a hybrid simulation technique for cone beam CT: application to an oral imaging system,” Phys. Med. Biol., 56, 5823–5843 (2011). [2] Zhang, G., Marshal,l N., Bogaerts, R., Jacobs, R., Bosmans, H., “Monte Carlo modeling for dose assessment in cone beam CT for oral and maxillofacial applications,” Med. Phys., 40 (7), 072103 (2013). [3] Zubal, I.G., Harrell, C.R., Smith, E.O., Rattner, Z., Gindi, G. and Hoffer, P.B.,...