SU-E-J-74: Evaluation of the Commercial Prototype Open Face Mask Used with Surface Rendering Imaging System for Proton Therapy Patients with Cancers of the Brain and Head: Successful Preclinical Study.

PURPOSE: Evaluation of the commercial prototype open face mask (Fibreplast, Q-FixTM) used with surface rendering imaging system (AlignRTTM, London, UK) for setup and monitoring of proton therapy patients with cancers of the brain and head.

METHODS

Fibreplastic open face masks were used with Base-of-Skull frame/moldcare pillow. Two sizes of the pre-made cutouts in the masks were investigated: leaveing open skin surface in the oval-shaped area between (I) upper lip and forehead boss, II) between mandible and forehead boss in superior-inferior direction; and between zygomatic (cheek-) bones/sphenoid bones laterally. Calibration of AlignRT system was verified with SRS cube phantom (VisionRT)and 2D X-ray patient positioning system (DIPS, IBA). The accuracy of translational shifts and rotations was a) verified using a head&neck phantom and b) tested using volunteers. Within AlignRT software, only the open area was used as ROI for the registration; the option 'Intracranial SRS' used for surface capture.

RESULTS

For the isocenter determination accuracy within 0.3mm/0.2 degrees, the head&neck phantom registration was performed with the 0.5mm/0.5 degree accuracy; the volunteer tests showed the registration accuracy within 0.5mm ±0.2mm (1 s)/0.7±0.2 (1 s) degree. The simulation of the noise in the surface data such as eye blinking and attempts to swallow/chew was performed, with negligible effect on the registration. No significant differences between the study results between the masks of type (I) and (II) were noticed.

CONCLUSIONS

The AlignRT surface rendering system has sufficient accuracy when used with the open face head&neck mask for localization/registration of the proton therapy patients with tumors of the head and brain.