The thickness of Cu filter to reduce 1/2 of the patient dose

Medical X-ray examination are increased double for the last 6 ∼ 8 years. Therefore a patient exposure dose should be decrease half every 7 years. We made an experiment on copper filter thickness to decrease a patient exposure dose up to half and compared to the image quality by MTF. The results as follow a thin region like extremities needs a thicker Cu filter as compared a thick region. 1/2 reduction filter must be thicker when kVp increase. Exposure factor should be increas when using 1/2 reduction filter : extremity is 4.0 times, chest 2.9 times, skull 1.62 times, and abdomen 1.58 times. The MTF of using 1/2 reduction filter is lower than without filter. But no difference of visual image. 1/2 reduction filter compared with double speed screen showed almost same image quality