Optimization of beam quality for lumbar spine imaging with heavy metal filters: a phantom model study

In radiological imaging, much research has been conducted on tube voltage and additional filters to reduce radiation exposure. In this study, the usefulness of heavy metal filters in lumbar spine imaging to maintain image quality and reduce radiation dose was investigated. A human-body phantom was irradiated with various combinations of tube voltages (70, 75, 80, 85, and 90 kV) and filters (Cu, Gd, Ho, Yb, W). For all beam qualities, the mAs value was adjusted so that the amount of CsI fluorescence at each dose after passing through the phantom was the same, and the contrast-to-noise ratio (CNR) and entrance-surface air dose (ESD) were measured. At 80 kV-Gd, the ESD was reduced by 34% while maintaining the CNR. The results showed that 80 kV-Gd gave the optimal beam quality for anterior–posterior lumbar spine imaging of patients with a standard body type.