Comparison of five methods for the derivation of spectra for a constant potential dental X-ray unit

Objectives: To compare the diagnostic X-ray spectra derived by different me thods for a constant potential dental X-ray unit. Materials and methods: Five methods of deriving X-ray spectra for a constan t potential dental X-ray unit were compared: measurement by spectrometer us ing cadmium-zinc-telluride (CZT) detector, calculation by Monte Carlo simul ation, calculation by two different, semiempirical methods and estimation f rom transmission data. The dental X-ray set was a Heliodent MD unit (Sirona , Charlotte, NC, USA) operable at 60 or 70 kV. A semiconductor detector was used in the spectrometer measurements and an ionization chamber dosimeter in the transmission measurements. From the five methods, photon-fluence spe ctra were derived. Based on the photon-fluence spectra, average energies an d transmission curves in aluminum were calculated. Results: For all five methods, the average energies were within 2.4% of one another. Comparison of the transmission curves showed an average differenc e in the range of 1 to 6%. Conclusion: All of the five methods of deriving spectra are in extremely go od agreement with each other.