A two dimensional silicon detectors array for quality assurance in stereotactic radiotherapy: MagicPlate-512

Area of Science:

• Medical Physics
• Radiation Oncology
• Detector Technology

Background:

• Silicon diode arrays offer advantages for radiation therapy quality assurance (QA), including real-time operation, high spatial resolution, large dynamic range, and small size.
• Existing diode arrays often have detector pitches too coarse for precise measurements in small radiation fields common in SBRT and SRS.
• The MagicPlate-512 (MP512) is a novel 2D monolithic silicon diode array designed to address these limitations.

Purpose of the Study:

• To characterize the performance of the MagicPlate-512 (MP512), a 2D monolithic silicon diode array.
• To evaluate its suitability for quality assurance (QA) in stereotactic body radiation therapy (SBRT) and stereotactic radio surgery (SRS).

Main Methods:

• The MP512 array, featuring 512 pixels (0.5x0.5 mm2 each) with a 2 mm pitch, was characterized.
• Evaluations included pixel response uniformity, dose linearity, percent depth dose, output factor, and beam profiling.
• Comparisons were made against ionization chambers and radiochromic films for various beam sizes relevant to SBRT and SRS.

Main Results:

• The MP512 demonstrated excellent dose linearity (R2=0.998) and repeatability (<0.2%).
• Depth dose measurements agreed within 1.3% with an ionization chamber for a 10x10 cm2 field.
• Output factors for field sizes down to 1x1 cm2 agreed within 2% with other detectors, though a 4% over-response was noted for beams <1 cm compared to film.

Conclusions:

• The MP512 2D detector array is suitable for in-phantom dosimetry in SRS and SBRT QA applications.
• While accurate for beam profiles and larger fields, discrepancies arise in output factor determination for very small fields (<0.5x0.5 cm2) due to field perturbation.
• Improving accuracy for sub-1 cm fields may require a reduced detector pitch, balancing performance with electronic complexity.