[Dosimetry using pyromellitic acid and trimellitic acid. Part 1].

PURPOSE

The intention of the study was to demonstrate that a chemical dosimeter on the basis of fluorescing acids is able to measure ionizing radiation much more sensitively than the Fricke dosimeter.

MATERIALS AND METHODS

As detectors for ionizing radiation pyromellitic acid (1,2,4,5-benzene-tetracarboxylic acid) and trimellitic acid (1,2,4-benzene-tricarboxylic acid) were investigated. Both solutions were exposed to pulsed 10 MV photons. The dose rate and the radiation dose were modified according to the different questions.

RESULTS

The correlation between absorbed dose and intensity of fluorescence was studied from 2 Gy up to doses of 16 Gy. Within this dose range the intensity of fluorescence of the mentioned solutions correlate with the absorbed doses in a single-valued and linear way. The fluorescence of pyromellitic acid is independent of the dose rate in the studied range from 0.6 Gy/min to 5 Gy/min. Detectors with trimellitic acid are able to quantify the absorbed energy of ionising radiation independent of the dose rate from 0.6 Gy/min on, but in contrast to pyromellitic acid only up to 3.8 Gy/min. The stability of the excitation and fluorescence spectra, the fading of the irradiated detectors, the reproducibility of the measured results and the increase of the null value of both solutions qualify for the use of these dosimeters in the clinical routine.

CONCLUSIONS

If further measurements should prove the independence of the presented detectors from the kind of radiation, the radiation quality and the temperature, there is a new possibility to use the specific advantages of chemical dosimeters in a more simple way.