A methodology for on-board CBCT imaging dose using optically stimulated luminescence detectors

Area of Science:

• Medical Physics
• Radiation Oncology
• Dosimetry

Background:

• Cone-beam computed tomography (CBCT) is vital for patient positioning in radiation therapy.
• CBCT imaging contributes significant radiation dose to healthy tissues.
• Accurate dosimetry is essential for assessing and minimizing this dose.

Purpose of the Study:

• To present a comprehensive dosimetry procedure for CBCT using optically-stimulated luminescence (OSL) nanoDots.
• To quantify key dose parameters including mean slice dose, cone beam dose index, and mean volume dose.
• To evaluate the feasibility of OSL nanoDots for CBCT quality assessment.

Main Methods:

• Utilized InLight optically-stimulated luminescence (OSL) nanoDots for dose measurement.
• Calibrated OSL nanoDots against a Farmer-type ionization chamber.
• Performed measurements using a custom-made phantom and a standard pelvic CBCT protocol.
• Quantified five dose parameters: DMSD, CBDIW, DMVD, D(FOV), and off-field dose.

Main Results:

• Measured mean slice dose (DMSD) of 31.1 ± 0.85 mGy and cone beam dose index (CBDIW) of 34.5 ± 0.6 mGy.
• Determined mean volume dose (DMVD) of 25.6 ± 1.1 mGy and off-field dose of 10.5 mGy.
• Reported patient skin doses: anterior 39.04 ± 4.4 mGy, lateral 27.1 ± 1.3 mGy.

Conclusions:

• OSL nanoDots offer a convenient and accurate method for CBCT dosimetry.
• The developed calibration and measurement procedure reduces uncertainty and aids quality assessment.
• OSL nanoDots' high spatial resolution enables precise dose measurement in regions with steep dose gradients.