Compelling 3D dosimetric measurements with an electronic detection device has been a long-standing problem in radiotherapy with no real solution in sight, until now. A 3D electronic detector array prototype based on active-matrices was constructed.
Active-matrices are fundamental in digital radiography, but in this case, the technology was re-purposed to measure dose from a 6 MV photon beam from different radiotherapy linacs. An active-matrix can provide fast data readout of several detector elements through shared data channels (multiplexing) without data loss, essential for 3D dosimetry with an electronic system. A prototype 3D cubic electronic detector array of PMMA material comprising 5 active-matrices (AM) with 529 detector elements per AM at strategic depths, is described below.
3D View of the detector prototype
Only detector elements within 10×10 cm2 were included in the deviation histogram data. This amounted to 169 pixels per AM and a total of 845 pixels for the 3D detector.
The linearity, dose rate, PDD, and profile results indicate that a 3D cubic electronic detector array works, and can provide reliable dosimetric data. Also, it shows that the detector has the sensitivity to distinguish a photon beam pulse quality from different linac vendors, which could be of interest to a user. Finally, it can provide a compelling 3D dose distribution measurement of a patient-specific treatment plan QA minutes after irradiation. Although more work remains to be done, these results are encouraging and could lead to a clinical model capable of providing, just about, all aspects of radiotherapy QA with a single device, as shown below.
