Zero-bias operation of polycrystalline chemically vapour deposited diamond films for Intensity Modulated Radiation Therapy

Abstract

A detailed investigation of the performance as a dosimeter of state-of-art polycrystalline CVD (pCVD) diamond detectors operated in photovoltaic regime for applications in clinical radiotherapy has been carried out with conventional 6-10-18 MV X-photons, as well as with a 10 MV photon Intensity Modulated Radiation Therapy (IMRT) beam from a linear accelerator. Our results show that the performances of a pCVD diamond dosimeter improves dramatically when operated in null-bias conditions. Main improvements with respect to operation with an external voltage applied are: a reduced pre-irradiation dose; an excellent time stability, characterised by standard deviations less than 0.5%; a rise-time comparable to that of commercial reference dosimeters; a linearity with dose proven over three decades; a reduced deviation from linearity of the current vs. dose-rate curve, output factors comparable to that of commercial reference dosimeters. These results represent a significant step towards clinical applications as IMRT with synthetic polycrystalline CVD diamond films.

High- quality polycrystalline CVD diamond for conformal radiotherapy applications

“…at the zero-field plane motion. Recently it has been shown by some of the authors that a considerable improvement of the performance of the pCVD diamond dosimeters can be obtained using them in zero-bias conditions [7]. Nonetheless, the choice of null-bias has as a drawback that current polarity of the pCVD diamond samples during exposure to irradiation in null bias could be either plus or minus, depending on which of the two Schottky barriers in fig.…”

“…On the contrary, current state-of-art technology demonstrates that segmented devices can be processed on high quality polycrystalline CVD diamond 4-6" wafers [6]. Recently it has been shown by some of the authors that a considerable improvement of the performance of the pCVD diamond dosimeters can be obtained using them in zero-bias conditions [7]. Nonetheless, applying an external bias, low enough to prevent unwanted polarization effects in the device, can be useful in view to preselect the polarity of the output current.…”

First dose-map measured with a polycrystalline diamond 2D dosimeter under an intensity modulated radiotherapy beam

“…These techniques in fact require to perform routinely accurate dosimetry analysis of large area, complex radiation fields delivered to the patients. Recently, a bidimensional dosimeter made with polycrystalline diamond, developed by us, was shown to successfully evaluate dose profiles in IMRT fields, when operated at low voltage [4][5][6].…”

A synthetic diamond diode in volumetric modulated arc therapy dosimetry

“…The behavior of synthetic diamonds for IMRT dosimetry has been analyzed in a few papers. [6][7][8][12][13][14] In particular, in the paper by Almaviva,6 very promising features of a synthetic single crystal diamond detector (SCDD) developed at Roma Tor vergata University are shown. These SCDDs have been tested as radiotherapy dosimeters with different beam qualities (photons from 60 Co to 10 MV and electrons from 6 MeV to 18 MeV).…”

“…4 Diamond detectors seem to be the best candidates for point dose measurements in this kind of highly conformal radiotherapy techniques. [5][6][7][8][9] A PTW natural diamond based dosimeter has been previously used for IMRT applications, 10,11 but its use is limited because of high costs and low availability of detector grade natural diamonds. The behavior of synthetic diamonds for IMRT dosimetry has been analyzed in a few papers.…”