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Program Information

A Patient Pebble Bed Pool for TBI


S Koren

S Koren1*, K Bernstein1, S Chen1, D Passarelli1, D No1, C Tai1, N Kalach1, E Furhang2, (1) Beth Israel Comprehensive Cancer Center, New York, NY, (2) Beth Israel Medical Center, New York, NY

SU-E-T-465 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:
To introduce a patient pebble bed pool that will enable a homogeneous patient dose distribution for TBI.

Methods:
We demonstrate the technique feasibility using a Rando phantom immersed in several hundred golf balls. We override the high density golf balls (HU ~800) to a water equivalent. A uniform dose distribution using a two lateral TBI treatment beams with an extended SSD was calculated using Eclipse (Varian inc.). A future system will have an optimized pebble radius size, while the smaller the radius the more homogeneous the surrounding media is. Larger pebble diameter will be used around the head in order to allow the patient to breath.

Results:
The body dose was found significantly more homogeneous using the pebble bed pool. The maximum dose was calculated about 11.5% higher without using the pool. For a quarter of the body volume the dose is about 2.6 times lower when the pool is used, while the other three quarters are comparable. A homogeneous neck axial cross-section dose profile is shown, overcoming an about 20% heterogeneity dose difference; between a pool to a none pool delivery.
This technique may also be suitable for proton and heavy ion beams therapy by allowing the usage of different beam angels while using the same compensator.

Conclusion:
We have demonstrated the feasibility of pebble bed pool usage for TBI cases where homogeneous dose distribution is needed. Future research includes pebble size optimization and investigation of the applicability of this technique for different treatment modalities conducted with a Monte Carlo technique in order to overcome the large amount of inhomogeneities.

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