Reducing patient radiation exposure from CT fluoroscopy-guided lumbar spine pain injections by targeting the planning CT

OBJECTIVE. CT fluoroscopy-guided lumbar spine pain injections typically include a preprocedural planning CT that contributes considerably to patient dose. The purpose of this study was to quantify the degree of radiation exposure reduction achieved by modifying only the planning CT component of the examination. MATERIALS AND METHODS. A retrospective review was performed of 80 CT fluoroscopy-guided lumbar spine injections. Forty patients were scanned with a standard protocol using automatic tube current modulation (method A). Another 40 patients were scanned using a new technique that fixed the tube current of the planning CT to either 50 or 100 mA on the basis of the patient's anteroposterior diameter and that reduced the z-axis coverage (method B). Dose-length products (DLPs) were compared for the two methods. RESULTS. The mean maximal tube current for the planning CT was 435.0 mA for method A and 67.5 mA for method B. The mean z-axis was shorter for method B at 6.5 cm than for method A at 9.6 cm (p < 0.0001). The mean DLP for the planning CT was 11 times lower for method B than for method A: 27.9 versus 313.1 mGy × cm, respectively (p < 0.0001). When method B was used, the mean DLP for the total procedure (i.e., planning CT plus CT fluoroscopy components) was reduced by 78%. There was no significant difference between methods A and B in CT fluoroscopy time (p = 0.37). All procedures were technically successful. CONCLUSION. A nearly fivefold reduction in radiation exposure can be achieved in CT fluoroscopy-guided lumbar spine pain injections through modifications to the planning CT alone.