Weighing up the radiation risks in CT-guided vs. fluoroscopy-guided spinal injections

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Tobias Dietrich

New research published in Radiology reports that CT-guidance is just as effective a tool for allowing interventional radiologists (IRs) to perform lumbar spinal injections as fluoroscopy-guidance, but exposes the physician to a lower radiation dose. However, the Swiss research team found that radiation exposure was greater for the patient when CT-guidance was used.

Both fluoroscopy- and CT-guided techniques are utilised by IRs to facilitate the administration of steroid therapy due to their proven ease of use and reliability, notes lead author Tobias Dietrich (Department of Radiology, Orthopedic University Hospital Balgrist, Zurich, Switzerland) and colleagues. The study investigators sought to compare the radiation exposure for patients and interventionalists, as well as the outcomes, between fluoroscopy-guided versus CT-guided lumbar spinal injections.

In their prospective, non-randomised observational study, Dietrich et al analysed the results of 1,446 patients who received transforaminal epidural injections or facet joint injections under fluoroscopic or CT guidance between October 2009 and April 2016. They measured radiation exposure for interventionalists with dosimeters at the body and wrist, and followed the “as low as reasonably achievable” (ALARA) concept for radiation dose.

There was no clinically significant difference in patient outcome as measured by the Patient Global Impression of Change (PGIC) scale, a patient-reported measure of pain used in this instance to evaluate efficacy at one day and one month post-procedural intervals. However, radiation dose to patients was higher with CT than fluoroscopy, as discerned through student t and χ2 tests.

The mean effective patient dose for fluoroscopy-guided lumbar transforaminal epidural injections was 0.24mSv±0.22, compared with the higher mean effective radiation dose of 0.33mSv±0.1 for CT-guided injections (P<0.003). This difference was more pronounced in effective radiation doses for lumbar facet joint injections: 0.1mSv±0.11 with fluoroscopy guidance, versus 0.33±0.13 for CT guidance (P<0.001).

However, the authors report interventionalists experiencing a reversal of this dose difference, with fluoroscopy-guided injections exposing physicians to more radiation than CT-guided ones: 0.42×103mSv recorded on body readings for the former versus 0.11±x103mSv±0.44 for the latter. Radiation exposure of the wrist for the interventionalist was higher during fluoroscopy-guided compared with CT-guided lumbar facet injections as well: 0.46×10-3mSv±0.93 vs. 0.06×10-3mSv±0.24, respectively (P<.006).

Overall, physicians’ radiation exposure was 3.7 to 10 times lower during CT-guided spinal injections than it was during fluoroscopy-guided injections (P<0.03). However, CT guidance required a statistically significant increase in patient radiation dose by a factor of 1.4 for epidural injections and 3.3 for facet joint injections, compared with fluoroscopy (P<0.003).

The benefits of CT-guided spinal injections, according to the study investigators, include less radiation exposure to the IR, and improved needle steering and manipulation without the need to constantly confirm the needle’s location. On the other hand, fluoroscopy-guided injections require real-time image guidance that increases radiation exposure to clinicians but decreases effective radiation dose for patients.

Clinicians also have the option of using other imaging techniques, such as ultrasound, MRI, and augmented reality, to guide lumbar injection therapies, the authors note. However, they add that physicians tend to feel less confident using these newer modalities, but propose that additional training and experience may enable them to further reduce the risk of radiation exposure.

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