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|Title:||Assessment of Various Thermoplastic Masks Used for Radiation Therapy Immobilization in Terms of Shrinkage and Pressure|
|Abstract:||The aims of this study are first, to assess and compare the amount of deformation for seven thermoplastic masks from three different manufacturers [Aquaplast RT-1889YS (Aqua variable perf), Fiberplast RT-1889KYS (Fiber variable perf), Embrace RT-8320 (Embrace), AccuPerf IMRT head mask RG461-4SHT (AccuPerf), Fiberplast RT-1889KS (Fiberplast), Aquaplast RT-1989S (Aqua thick), and Aquaplast RT-1889S( Aquaplast)] using time lapse photography, and second, to measure the amount of pressure exerted by each mask on a rigid head phantom using pressure sensitive film. For the first aim, all masks were marked with fiducial points located near forehead, nose, and chin. The masks were fabricated on a rigid head phantom following manufacturer instructions. Each mask was mounted on a plastic mounting tray, and photographed in a sagittal view over the span of one week. The fiducial coordinates were determined by a center of mass algorithm. A scale factor was determined by photographing a graph sheet mounted in place of the mask. For the second aim, the pressure exerted by each mask was evaluated by mounting the mask on the head phantom after sandwiching a strip of pressure sensitive film between the two at three anatomical locations: the forehead, nose, and chin. Measurement of translation in the posterior direction did not give reproducible results as direct caliper measurements did not agree with those from the time-lapse photography technique. In the superior/inferior direction, the Embrace mask showed the greatest deformation at forehead and nose areas (1.069±0.017mm (inferiorly), and 0.432±0.010mm (inferiorly) respectively), while the Aqua thick mask showed the greatest deformation at chin area (0.970±0.016mm (superiorly)). The averaged median pressure of the masks at the forehead location were not significantly different except for the Fiber variable perf which showed the greatest averaged median pressure ( 0.118 MPa). At the nose location, no mask showed a significantly different averaged median pressure. At the chin location, the Aqua thick mask showed a significantly higher averaged median pressure compared to the others (0.180 MPa).|
|Appears in Collections:||Open Access Dissertations and Theses|
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