Room: ePoster Forums
Purpose: We made patient specific plastic scintillation detectors in the shape of the tumor shape using a 3D printer and in-house plastic ink to develop a new method to assess the accuracy of IMRT plans.
Methods: A scintillating plastic material was developed to be used in a commercial 3D printer. The patient specific detector was printed along the shape of the tumor which was extracted from patient DICOM images. The conversion factors from light output to absorbed dose rates were obtained using Monte Carlo simulations with Geant4 and measurement with a Gamma Knife Perfexion. In order to apply the detector for verification of IMRT plans, Varian Clinac IX 2300 system was simulated also with Geant4. The code was commissioned with the percent depth dose curve and lateral distributions. Absorbed doses to the patient specific detector in a water phantom in various IMRT planning will be generated and compared with actual measurement.
Results: The light output of the scintillation detector was about 20% compared to that of a commercial BC408 detector. The current from the detector in 2 Gy/min radiation from a Gamma Knife was in the order of 0.1 micro ampere and signal to noise ratio was higher than 100. The conversion factors were obtained by irradiating the detector using the 4, 8, and 16 mm collimators. The absorbed energies measured using the scintillating detector were showed the acceptable difference within the error range of the treatment planning program.
Conclusion: This study showed that the developed scintillation material and the patient specific detectors made of it can be used to assess the accuracy of the total energy absorbed to the tumor of radiation treatment plans. The accuracy of the conversion factor needed to be improved in order that this system is used in actual patient specific QA.