Application of diamond detectors to the dosimetry of 45 and 100 kVp therapy beams: comparison with a parallel-plate ionization chamber and Monte Carlo

Abstract

Diamond detectors have become an increasingly popular dosimetric method where either high spatial resolution is required or where photon or electron spectra are likely to change with depth or field size. However, little work has been previously reported for superficial energies. This paper reports the response of a commercially available diamond detector (PTW Freiburg/IPTB Dubna) at 45 kVp (0.55 mm Al first HVL) and 100 kVp (2.3 mm Al first HVL) including dose and dose-rate linearity, percentage depth-dose and output factors as a function of applicator size. Comparisons are made with Br J. Radiol. supplement 25 data, measurements using a PTW parallel-plate chamber and Monte Carlo simulations based on spectra determined from transmission measurements in aluminium. Excellent agreement was obtained for percentage depth-dose curves between Monte Carlo and diamond after correcting for sublinearity of the dose-rate response and energy dependence of the diamond detector. However, significant differences were noted between diamond/Monte Carlo and the parallel-plate chamber, which is attributed to the perturbation caused by the polyethylene base of the chamber

An evaluation of ionization chambers for the relative dosimetry of kilovoltage x‐ray beams

“…11 Based on these recommendations, the accepted detector for relative dosimetry of kilovoltage x-ray beams is the Farmer-type ionization chamber, which has been used widely for clinical dosimetry measurements. 3,4,9,[11][12][13][14][15][16][17][18] While Farmer chambers usually have an excellent energy response, they have a relatively large diameter, thus limiting their use in measurements near the surface of a water phantom. Other dosimeters that have been studied for the dosimetry of kilovoltage x-ray beams include diamond detectors, Gafchromic film, diode detectors, and MOSFETs.…”

“…Other dosimeters that have been studied for the dosimetry of kilovoltage x-ray beams include diamond detectors, Gafchromic film, diode detectors, and MOSFETs. 16,[19][20][21][22] Each of these either requires calculation of various corrections factors or gives significant dose deviations. Another option is to simply use published depth dose data as provided by the BJR.…”

The Bland–Altman analysis: Does it have a role in assessing radiation dosimeter performance relative to an established standard?

“…A number of studies have evaluated different detector types for the dosimetry of low energy photon beams (Fletcher and Mills, 2008;Guillerminet et al, 2005;Healy et al, 2005;Hill et al, 2008;Hugtenburg et al, 2001;Jurado et al, 2005;Li et al, 1997;Ma et al, 1998;Nelson et al, 2008;Prestwich and Murphy, 2000;Rink et al, 2007;Sellakumar et al, 2009). There are limited recommendations by which a new detector should be tested in order that it can replace a gold standard detector.…”

“…For example, what are the requirements to replace a Farmer type ionisation chamber in the measurement of depth dose curves for kilovoltage x-ray beams? The methods that are currently used in this case include determining the mean or maximum dose difference, plotting the two depth doses or listing them in table form, taking the ratios of the doses and comparing air kerma calibration measurements performed in a standards laboratory (Aukett et al, 2005;Cheung et al, 2005;Hugtenburg et al, 2001;Jurado et al, 2005;Li et al, 1997;Ma et al, 1998). Taking the ratio of measured depth doses is not suitable because for the smaller values of relative dose at depth, the ratio of two smaller numbers with a small difference is large.…”

Characterization of X-Ray Diamond Detector by Monte Carlo Method

“…Excellent agreement was obtained for percentage depth-dose curves between Monte Carlo and diamond after correcting for sublinearity of the dose--rate response and energy dependence of the diamond detector. However, significant differences were noted between diamond detector/Monte Carlo and the parallel--plate chamber, which is attributed to the perturbation caused by the polyethylene base of the chamber [7].…”