CT-Guided Lumbar Nerve Root Injections: Are We Using the Correct Radiation Dose Settings?

Comparison of CT and fluoroscopic guidance for lumbar puncture in an obese population with prior failed unguided attempt

“…CT has the advantages over fluoroscopy and ultrasonograpy of providing millimeter accuracy, soft tissue visualization, and direct thecal sac visualization. Negatives of CT guidance include potentially higher radiation dosage if an extensive area is imaged during planning, and machine settings are not optimized to minimize exposure 8 9…”

Effect of Body Habitus on Radiation Dose during CT Fluoroscopy-Guided Spine Injections

“…Tube current adjustments of this order of magnitude would ensure that organ doses would not be substantially increased in patients with smaller or larger than average habitus. Previous investigations have suggested that patients with an AP diameter of >30 cm on the scout image can be considered oversized 8 , and in practice, we have found that an AP diameter of <20 cm can generally be used to define patients of small body habitus.…”

“…There is, however, wide variation in the degree to which tube current may be adjusted by individual operators to account for changes in body habitus, even in similar procedures on the same population of patients 8 .…”

“…During such CTF procedures, the operator is required to select tube current settings for use during the procedure; patient body habitus is a major consideration in making this selection. In practice, however, tube current selection varies widely among proceduralists, and adjustments for body habitus are not always made in a systematic fashion 8 . Understanding the impact of body habitus on dose during CTF procedures is therefore important both for assisting the selection of an appropriate tube current, as well as for comparing the relative radiation exposure of CTF procedures to those performed with conventional fluoroscopy.…”

“…Although the relationship between body habitus and radiation dose in diagnostic CT imaging has been extensively investigated [9][10][11][12][13][14][15][16] , dose estimation in CTF procedures is more compli- Figure 1 Scout CT image of prone phantom demonstrating inner (*) and outer (**) layers of 4.5-cm-thick circumferential adipose-equivalent material. A single layer was applied to simulate average body habitus, and two layers were applied to simulate oversize habitus.…”