[New three-dimensional compensating filter for TBI using compu-former associated with RT LAN].
To shorten the TBI process, we developed a new device for making the three-dimensional (3D) compensating filter that improves dose distribution. The dose distributions in the phantom and manufacturing time were compared between the new device and the previous one. Clinical evaluations included dose distribution in patients and the clinical rate of interstitial pneumonitis (IP). Our 3D compensating filter is made of polystyrene resin and gypsum. The filter was made after performing two procedures as follows. Patient data were measured by CT, and the 3D dose-distribution data and 3D compensating-filter data were obtained from the CT data by the 3D radiation planning system. We were able to produce the new 3D compensating filter within about 4 hours, including all procedures. The average dose distribution to each site when the 3D compensating filter was used was 92.7% to the head, 102.1% to the thorax, 106.4% to the pelvis, 90.2% to the knee, and 93.8% to the ankle joint, when the scheduled dose was taken as 100%. Dose distribution was improved. IP occurred in 6 of 32 patients (18.8%). There was no significant difference between the TBI and non-TBI groups in the frequency of IP (p = 0.27).