Department of Cancer, West Michigan Cancer Center, USAFulltext PDF
Purpose: Use optical imaging guidance to test the effectiveness of three different methods for immobilizing stereotactic radio surgery patients.
Methods: Patients were immobilized with a BRW stereotactic head frame, an Orfit model 33759: 3-point Hybrid open face thermoplastic mask, or an Orfit face mask with Nanor reinforcement. The face masks are open around the mouth, nose, eyes, brows, and temples so that the optical system images the face of the patient not the mask itself. Real time 3D surface images of the patient are compared by AlignRT software against this reference image. Changes in patient alignment are reported as a vector distances every 0.2s during the treatment.
Results: A histogram analysis of the optical noise signal in the AlignRT system shows an equivalent average motion of 0.05 mm and 90% of the time has a motion less than 0.07 mm. For 26 patients with the model 33759 face masks, the average motion is found to be 0.34 mm and for 26 patients with the Nanor mask 0.32 mm. 90% of the time motion was less than 0.50 mm with a range of 0.28 mm to 1.85 mm. When the head frame was used the average motion is 0.93 mm and 90% of the time the motion was less than 1.4 mm.
Conclusion: Both types of open-face masks immobilize patients to ≤ 0.4 mm of motion. The head ring allows 3 fold more patient motion than an open-face mask. AlignRT is a useful tool for monitoring motion of stereotactic radiosurgery patients.
Optical guidance radiation therapy; Stereotactic radiosurgery; Head immobilization; Thermoplastic face mask
Jursinic P. Comparison of Head Immobilization with a Metal Frame and Two Different Models of Face Masks. J Cancer Cure. 2018;1(1):1002.