Feasibility Study of Using XRV-124 Scintillation Detector for Collinearity Measurement in Uniform Scanning Proton Therapy.

PURPOSE

The purpose of this work is to study the feasibility of using an XRV-124 scintillation detector in measuring the collinearity of the x-ray system and uniform scanning proton beam.

METHODS

A brass aperture for Snout 10 was manufactured. The center of the aperture had an opening of 1 cm in diameter (4 cm for the film measurements). The 2D kV x-ray images of the XRV-124 were acquired such that the marker inside the detector is aligned to the imaging isocenter. After obtaining the optimal camera settings, a uniform scanning proton beam was delivered for various ranges (12 g/cm to 28 g/cm in step size of 2 g/cm). For each range, 10 monitor units (MU) of the first layer were delivered to the XRV-124 detector. Collinearity tests were repeated by using EDR2 and EBT3 films following our current quality assurance protocol in practice. The results from the XRV-124 measurements were compared against the collinearity results from EDR2 and EBT3 films.

RESULTS AND DISCUSSION

The collinearity results were evaluated in the horizontal (x) and vertical (y) directions. The average deviation in collinearity in the x-direction was -0.24 ± 0.30 mm, 0.57 ± 0.39 mm, and -0.27 ± 0.14 mm for EDR2, EBT3, and XRV-124, respectively. In the y-direction, the average deviation was 0.39 ± 0.07 mm, 0.29 ± 0.14 mm, and 0.39 ± 0.03 mm for EDR2, EBT3, and XRV-124, respectively.

CONCLUSION

The measurement results from the XRV-124 and films are in good agreement. Compared to film, the use of the XRV-124 detector for collinearity measurements in uniform scanning protons is more efficient and provides results in real time.