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Session: Therapy Radiotherapy Planning and Delivery [Return to Session]

Use of a Novel Kernel Discovery Method for KV Beam Dose Calculation in Small Animal Irradiators

X Liu*, T Zhu, R Wiersma, University of Pennsylvania, Philadelphia, PA


WE-C1000-IePD-F7-6 (Wednesday, 7/13/2022) 10:00 AM - 10:30 AM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 7

Purpose: Small animal kilovoltage (kV) beam irradiators have been widely used in preclinical study. However, the related sub-millimeter resolution dosimetry is yet to be explored for such research platforms. In this work, we proposed a novel kernel discovery method for kV beam dose calculations based on experimental dose measurement.

Methods: The beam dose was measured on radiation research platform (SARRP, Xstrahl) using EBT3 Gafchromic films for several different collimator geometries. This measured film data was converted into 2D dose fluence map and inputted into an iteration algorithm to search for a kernel shape that minimized the difference between the simulated and experimentally measured fluence maps. The kernel is both x and y axis symmetry in the fluence map plane, and its bixel intensity is descended when away from its center. Once the optimal kernel for the particular machine is discovered, it can then be used to calculate any arbitrary dose distribution using typical pencil beam convolution. To perform end-to-end testing, several IMRT plans were generated using 3D printed compensators, delivered to Gafchromic film, and gamma analysis performed.

Results: The resulted kernel was used to calculate the dose distribution of the beams that were modulated by coper filament compensators and compared to the dose on the exposed films by gamma analysis. For all 10 compensator modulated beams, the gamma analysis pass rate for the criteria 0.3mm/3% was 98.0 +/-1.4 %.

Conclusion: The square-based kernels approach can generate accurate dosimetry for kV beam due to its special way of dividing the beam, and the kernels are not circular symmetry, which is different from the traditional point kernel-based algorithms. And the accuracy was verified by gamma analysis of modulated kV beams. The kernels can also be summed up to a larger size of the square beamlet to speed up dose calculation.


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