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Measurement of Eye Lens Dose for Varian On-Board Imaging with Different CBCT Acquisition Techniques

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S DESHPANDE1*, D Dhote2 , R Kumar3 , K Thakur4 , (1) ,,,(2) Brijlala Biyani Mahavidyalaya, Amravati, Maharastra, (3) BARC, Mumbai, Maharastra, (4) Holyspirit hospital, Mumbai, Maharastra


SU-E-J-11 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

To measure actual patient eye lens dose for different cone beam computed tomography (CBCT) acquisition protocol of Varian’s On Board Imagining (OBI) system using Optically Stimulated Luminescence (OSL) dosimeter and study the eye lens dose with patient geometry and distance of isocenter to the eye lens

OSL dosimeter was used to measure eye lens dose of patient. OSL dosimeter was placed on patient forehead center during CBCT image acquisition to measure eye lens dose. For three different cone beam acquisition protocol (standard dose head, low dose head and high quality head) of Varian On-Board Imaging, eye lens doses were measured. Measured doses were correlated with patient geometry and distance between isocenter to eye lens.


Measured eye lens dose for standard dose head was in the range of 1.8 mGy to 3.2 mGy, for high quality head protocol dose was in range of 4.5mGy to 9.9 mGy whereas for low dose head was in the range of 0.3mGy to 0.7mGy. Dose to eye lens is depends upon position of isocenter.For posterioraly located tumor eye lens dose is less.

Conclusion:From measured doses it can be concluded that by proper selection of imagining protocol and frequency of imaging, it is possible to restrict the eye lens dose below the new limit set by ICRP. However, undoubted advantages of imaging system should be counter balanced by careful consideration of imaging protocol especially for very intense imaging sequences for Adoptive Radiotherapy or IMRT

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