SU-E-T-153: Detector-Grade CVD Diamond for Radiotherapy Dosimetry

Area of Science:

• Medical Physics
• Materials Science
• Radiotherapy Physics

Background:

• Accurate dosimetry is critical in radiotherapy for effective cancer treatment.
• Current detectors may have limitations in sensitivity or spatial resolution for small radiation fields.
• Synthetic diamond films offer unique properties for radiation detection applications.

Purpose of the Study:

• To evaluate commercially available synthetic diamond films produced via chemical vapor deposition (CVD) as x-ray detectors.
• To assess their suitability for radiotherapy dosimetry, particularly in small radiation fields.

Main Methods:

• A CVD diamond detector with a 0.4 mm³ sensitive volume was fabricated and encapsulated.
• Measurements were performed in a water phantom using a clinical linear accelerator (linac) with 6- and 10-MV photons.
• Key detector characteristics evaluated included leakage current, response dynamics, dose linearity, dose rate dependence, percent depth dose, and output factors, with comparisons to ion chambers and silicon diodes.

Main Results:

• Negligible leakage currents (∼1 pA) and high sensitivity (680 nC/Gy) were observed.
• Detector response showed fast rise/fall times (< 2 s) and linearity up to 5 Gy.
• Percent depth dose profiles closely matched ion chamber measurements, and output factors were accurate for field sizes 5-15 cm.

Conclusions:

• CVD synthetic diamond films demonstrate significant potential for small field dosimetry in radiotherapy.
• Their small sensitive volume and high sensitivity are advantageous for precise dose measurements.
• Further research is needed to optimize detector packaging and explore broader clinical applications.