The Third International Intercomparison on EPR Tooth Dosimetry: part 2, final analysis

The objective of the Third International Intercomparison on EPR Tooth Dosimetry was to evaluate laboratories performing tooth enamel dosimetry <300 mGy. Final analysis of results included a correlation analysis between features of laboratory dose reconstruction protocols and dosimetry performance. Applicability of electron paramagnetic resonance (EPR) tooth dosimetry at low dose was shown at two applied dose levels of 79 and 176 mGy. Most (9 of 12) laboratories reported the dose to be within 50 mGy of the delivered dose of 79 mGy, and 10 of 12 laboratories reported the dose to be within 100 mGy of the delivered dose of 176 mGy. At the high-dose tested (704 mGy) agreement within 25% of the delivered dose was found in 10 laboratories. Features of EPR dose reconstruction protocols that affect dosimetry performance were found to be magnetic field modulation amplitude in EPR spectrum recording, EPR signal model in spectrum deconvolution and duration of latency period for tooth enamel samples after preparation.     

Fundamentals of a Pulsewidth Modulated Power Circuit

This paper describes the practical design and operating principles of the pulsewidth modulated (PWM) inverter. The use of this power circuit in a variable voltage, variable frequency ac motor drive is emphasized. A comparison with the conventional adjustable voltage input inverter is made with respect to input-output characteristics as well as the effect of the unit on the input supply. This paper demonstrates the ability to design and produce a practical system using state of the arts components.