Corrugated fiberboard as a positioning insert for patients undergoing radiotherapy

We have developed a new body fixation system for single patient use,which consists of a vacuum cushion,a thermoplastic fixation sheet which is used to suppress involuntary and voluntary patient movement,and a triple-wall corrugated fiberboard base plate to which both the vacuum cushion and the thermoplastic sheet are affixed. to evaluate the characteristics of the fiberboard as a patient-positioning insert,the photon beam attenuation of a fiberboard base plate,a carbon-fiber base plate,and a vacuum-formed cushion were compared. the strength of the fiberboard was also evaluated. the attenuation for the carbonfiber base plate was 3.7% and 2.6% in 4 mv and 10 mv photon beams,respectively,while the results were less for the fiberboard base plate,i.e. 1.9% and 1.6%. the vacuum-formed cushion had a minimal effect on transmission. none of the materials subsided under the weight loading of 20 g/cm2. there was no difference between the thicknesses of the fiberboard before and after a 50 times daily load with the 60 kg weight of a volunteer. corrugated fiberboard is a robust and low attenuating material that functions well as a patient-positioning insert.