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DIGITAL RADIOGRAPHY FOR QUALITY DETERMINATION OF SMALL AGRICULTURAL PRODUCTS: DEVELOPMENT AND CALIBRATION OF EQUIPMENT

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  036231,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.14168) @2003
Authors:   Nachiket Kotwaliwale, Jeyamkondan Subbiah, Paul W. Weckler, Gerald H. Brusewitz, Glenn A. Kranzler
Keywords:   X-ray, Radiation shielding, Calibration, Digital radiograph, X-ray imaging, Beam hardening

Soft X-ray imaging of agricultural products for quality determination is gaining worldwide interest. Recent advances in technology have made it possible to capture and store or instantaneously process digital X-ray images at higher resolution for lower cost. An X-ray imaging system was developed and calibrated to capture images with a resolution of 1024 x 1024 pixels in 50 mm x 50 mm area. Maximum X-ray tube voltage was 50 kVp, maximum current 1 mA, and signal integration time ranged from 460 to 6700 ms. The system consist of an X-ray source tube producing polychromatic X-rays, a camera composed of CMOS photodiode arrays, a frame grabber, and a data acquisition and control card. Because the X-ray beam is polychromatic, and the detector responses are variable, calibration is necessary to relate image intensity to X-ray intensity. Imprecision of the system was 1.62 gray level for 8-bit pixel depth. Response, measured as mean pixel intensity, varied linearly with X-ray tube current and integration time and had a quadratic relationship with peak tube voltage. A statistical model was developed to estimate blank image intensity at higher voltages and currents. Prediction and validation errors for the model were 1.18 and 2.72 gray level, respectively. The Beam hardening effect was demonstrated using polystyrene.

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