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Evaluation of the Dosimetric Properties of a Synthetic Single Crystal Diamond Detector in Clinical Proton Beams

A Mandapaka

A Mandapaka1*, G Verona-Rinati2, A Ghebremedhin1, B Patyal1, (1) Loma Linda Univ Medical Center, Loma Linda, CA, (2) Universita di Roma "Tor Vergata", Roma,Italy

SU-E-T-104 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To investigate the dosimetric properties of a new synthetic single crystal diamond
Schottky diode for accurate relative dose measurements in clinical proton beams.

Methods: The dosimetric properties of the synthetic single crystal diamond detector (SCDD) were assessed by comparison with a reference parallel plate ionization chamber (PTW Markus Chamber 23343) and a micro ionization chamber (Exradin A16). The diamond detector was operated at zero bias voltage at all times. Comparative dose distribution measurements were performed by means of percent depth dose curves and lateral beam profiles using the diamond detector and a reference ionization chamber in clinical proton beams of energies 155MeV and 250 MeV for a 14cm square cerrobend aperture and 126 MeV for 3cm, 2cm and 1cm diameter circular brass collimators. ICRU 78 recommended beam parameters are used to compare the percent depth dose curves and lateral profiles obtained using the SCDD and the reference ionization chamber. The warm-up/stability of the detector response, dose linearity and dose-rate dependency were also evaluated in a 250 MeV proton beam.

Results: During warm-up/stability the diamond detector was irradiated 6 times and the maximum deviation from the average reading was less than 0.5%. The detector response shows a good linear behavior as a function of dose with observed deviations below 0.5% over a dose range of 50cGy to 500cGy. The detector response is dose rate independent, with deviations below 0.5% in the investigated dose-rates of 64cGy/min,47.5cGy/min and 17.5cGy/min. Percent depth dose curves and lateral beam profiles obtained with the diamond detector were in good agreement with those obtained using reference dosimeters.

Conclusion: The observed dosimetric properties of the SCDD indicate that its behavior is proton energy independent in the investigated energy range and it is suitable for accurate relative dosimetric measurements in large field and small field clinical proton beams.

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