Digital scintillation-based dosimeter-on-a-chip

A reliable, low-cost, real-time dosimeter is constructed from a scintillation crystal mounted to a CMOS solid-state photomultiplier. Determination of the minimum silicon area that can provide reliable dose information is important to minimize dosimeter cost, and allow pervasive deployment. The purpose of this paper is to examine the effect of errors from event statistics and temperature variations on the dose measured in the crystal and the calculated human equivalent dose calculated using principal component analysis (PCA). Measured spectra are written as a linear combination of the calibration data sets, or principal components, and weighting factors from the calibration data are used to calculate the human equivalent dose. Applying this method to data measured by a 1.2times1.2times 0.2-mm
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LYSO scintillator coupled to a 100-pixel SSPM allows a predicted dose sensitivity better than 1 muSv, with far less than 40% error in determination of the dose from several unknown sources outside the calibration set. The measured sensitivity is approximately 1/300 the radiation dose from natural background in one month, making possible use as a potential replacement for a monthly film badge. Statistical fluctuations, temperature-induced gain fluctuations, and number of calibration sources required are investigated with respect to the dose calculated using the PCA method.