PATIENT SAFETY Radiation Dose for 345 CT-Guided Interlaminar Lumbar Epidural Steroid Injections

BACKGROUNDAND PURPOSE: CT guidance is increasingly being used to localize the epidural space during epidural steroid injections. A common concern is that CTmay be associatedwith significantly higher radiation doses comparedwith conventional fluoroscopy. The goal of this retrospective study was to determine the average dose-length product and effective dose delivered while interlaminar epidural steroid injections are performed and allow comparison with other modalities. MATERIALS AND METHODS: A total of 281 patients who had undergone 345 consecutive CT-guided epidural steroid injections of the lumbar spine were evaluated for radiation exposure. The dose-length product for each scan was derived from the CT dose index volume and scan length. Effective dose was then calculated from the dose-length product and a coefficient of 0.015. Procedure time was calculated from the PACS time stamp on the scout image to the last CT image of the last image series. RESULTS: The average dose-length product across all procedures was 89.6 3.33 mGy cm, which represents an effective dose of 1.34 0.05 mSv. No complications from the procedure were observed, and average procedure time was 8 minutes. CONCLUSIONS: The use of a stationary table and an intermittent scanning technique allow for short procedures and doses that are significantly lower than those of conventional diagnostic CT scans. Furthermore, because CT dose index overestimates radiation dose in stationary table procedures, the actual radiation dose may be even lower than stated here. ABBREVIATIONS: CTDI CT dose index; CTDIvol CTDI volume; DLP dose-length product; ED effective dose; ESI epidural steroid injection CT guidance has been increasingly adopted for use in interventional procedures of the spine, including epidural steroid injections (ESIs). ESIs are performed by injection of a corticosteroid solution, often with a local anesthetic, into the epidural space of the spine. This procedure is frequently used to treat radicular pain from herniated disks and spinal stenosis. CT offers several advantages versus traditional fluoroscopy, including the ability to visualize the soft tissues and provide higher anatomic precision and more accurate needle placements, and the option of using air instead of contrast medium to localize the epidural space. Accurate localization of the epidural space and needle position during ESIs is crucial, as it facilitates precise delivery of medications and reduces the risks for needle misplacement and subsequent complications. Previous reports on blind injections have shown incorrect placement in up to 25% of cases, even when performed by experienced providers. We recently reported our experience of safely performing 1000 procedures with CT guidance and air contrast to localize the epidural space. The goal of this study was to analyze a cohort of similar patients to evaluate the dose-length product (DLP) and effective dose (ED) delivered while interlaminar ESI was being performed. Review of CT Dose Index, Dose-Length Product, and Effective Dose CT dose index (CTDI) is a commonly used measure of dose in CT dosimetry. It is defined by the formula