[Comparative Study of Surface Conformity of Flexible Boluses Composed of Different Materials].

Purpose: The purpose of this study was to compare the surface conformity of Clearfit Bolus II (Clearfit2) (Fujidenolo, Aichi) and Clearfit Bolus (Clearfit1) (Fujidenolo) using an anthropomorphic phantom.

Methods: Clearfit1 and Clearfit2 boluses (5 mm thick) were placed in three anatomical regions of the anthropomorphic phantom: nose, breast, and abdomen, and CT scans were performed. Digital Imaging and Communications in Medicine (DICOM) structural data were used to measure the air gap between the bolus and the surface of the phantom. The surface conformity area ratio at the threshold (1-5 mm) was calculated. Statistical analysis was performed using the Mann-Whitney U test.

Results: Clearfit2 had significantly reduced air gaps compared to Clearfit1: 2.9±2.0 mm in the nose, 1.8±2.1 mm in the breasts, and 0.1±0.1 mm in the abdomen, which were lower than Clearfit1's 5.8±2.9 mm, 11.4±8.4 mm, and 2.2±2.1 mm, respectively (p<0.001). In the abdominal region, Clearfit2 achieved near-perfect surface conformity with over 99% of the surface showing gaps ≤1 mm.

Conclusion: We demonstrated that Clearfit2 significantly improves the surface conformity by reducing air gaps between the bolus and the phantom surface compared to Clearfit1.