Effective Dose of CT-Guided Epidural and Periradicular Injections of the Lumbar Spine: A Retrospective Study

Abstract

Spinal injection procedures can be performed blindly or, more accurately, with fluoroscopic or computed tomography (CT) guidance. Radiographic guidance for selective nerve root blocks and epidural injections allows an accurate needle placement, reduces the procedure time and is more secure for the patient, especially in patients with marked degenerative changes and scoliosis, resulting in a narrowing of the interlaminar space. Limiting factors remain the availability of scanners and the radiation dose. Interventional CT scan protocols in axial CT-acquisition mode for epidural and periradicular injections help to limit the radiation dose without a significant decrease of image quality. The purpose of this retrospective study was to analyze the effective radiation dosage patients are exposed during CT-guided epidural lumbar and periradicular injections. A total amount of n=1870 datasets from 18 months were analyzed after multiplying the dose length product with conversion factor k for each lumbar segment. For lumbar epidural injections (n=1286), a mean effective dose of 1.34 mSv (CI 95%, 1.30-1.38), for periradicular injections (n=584) a mean effective dose of 1.38 mSv (CI 95%, 1.32-1.44) were calculated.

Keywords: CT; Computed tomography; dose.; epidural; guidance; injections; interventions; perineural; periradicular; radiation; spinal.

Fig. (1)

Effective Dose in mSv in lumbar epidural (left) and periradicular (right) injections.

Fig. (2)

CT-guided epidural injection at the level L5/S1 (left image) and periradicular injection near the L5-nerve root (right image) in the standard interventional protocol (axial CT-acquisition).

Fig. (3)

Comparison of standard interventional protocol (left image) and low-dose protocol (right image) in CT-guided L5-nerve root block. Despite the reduced contrast in the low-dose image, the needle (29 gauge, most thin needle caliber) is still visible as good as the bony landmarks of the neuroforamen. A dose reduction of 85% was achieved.