Scattered radiation from a DSA compensation filter

When a compensation filter for DSA is placed at the X-ray exit port, scattered radiation is emitted from the port, and the space dose rate outside the intended irradiation fields increases. The authors therefore assessed the effect of scattered radiation generated by a DSA compensation filter and by the patient's body at sites outside the irradiated fields. An acrylic compensation filter was placed at the X-ray exit port, and scattered radiation doses were measured with an ionization chamber and a photoluminescence dosimeter. The results showed that scattered radiation emitted by the compensation filter was greater than emitted by the body in most outside the intended irradiation fields. The thickness of the compensation filters made of acrylic acid resin (0-6 cm) had no effect on scattered radiation from the body, but the scattered radiation dose from the acrylic filter increased with its thickness, and with the 6 cm acrylic filter it was more than 5 fold the dose emitted by the body. When the scattered radiation dose was compared according to the material, the generated dose was found to be the greatest with the acryl filter and least with the Cu filter. The difference between acrylic and Cu filters was more than 30 fold. The thickness of the filter influenced the scattered radiation dose more than the material. When a Cu filter is used in addition to the acrylic filter with a compensation filter, the scattered radiation and entrance dose were reduced 45% and 40%, respectively, compared to when an acrylic filter was used alone. When the thickness of the additional Cu filter was changed (0.2-0.6 mm), the scattered radiation dose decreased with every size filter added, but the percentage reduction was greatest with the 0.2 mm Cu filter. (K.H.)