How accurate is image guided radiation therapy (IGRT) delivered with a micro-irradiator?

Abstract

There is significant interest in delivering precisely targeted small-volume radiation treatments, in the pre-clinical setting, to study dose-volume relationships with tumor control and normal tissue damage. In this work we investigate the IGRT targeting accuracy of the XRad225Cx system from Precision x-Ray using high resolution 3D dosimetry techniques. Initial results revealed a significant targeting error of about 2.4mm. This error was reduced to within 0.5mm after the IGRT hardware and software had been recalibrated. The facility for 3D dosimetry was essential to gain a comprehensive understanding of the targeting error in 3D.

Figure 1

Illustrative projection images through (a) an un-irradiated, and (b) an irradiated Presage dosimeter.

Figure 2

(a) an axial view through the Presage dosimeter at a plane through one of the 4 target points. (b) the same image but with central beam line annotations to highlight the cone misalignment.

Figure 3

Illustrative projection images, after recalibration of the IGRT system, through (a) an un-irradiated, and (b) an irradiated Presage dosimeter.

Figure 4

(a) axial view through the Presage dosimeter at a plane through one of the 4 target points treated with a 1mm cone. (b) the same image but with central beam line annotations to highlight much improved alignment compared with Figure 2. (c) similar image through another target point treated with a 5mm cone.