Low-dose CT scanning reduces radiation exposure without increasing complication rate

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Juraj Artner, Department of Orthopaedic Surgery, University of Ulm, Ulm, Germany, and others outline, in Patient Safety in Surgery, a new approach to CT-guided periradicular injections in the lumbar spine for reducing radiation exposure. 

Artner et al commented that the main benefit of CT-guided spinal injections is “the precise and safe needle placement, especially in patients with severe degenerative spinal changes”. However, they added that the radiation exposure, because of the CT scan, to the patient and to the performing interventionalist was a concern. They wrote: “The stochastic radiation effect due to a cumulative radiation dose in patients suffering from degenerative spinal disorders, implicating a long-term therapy and use of spinal injections is often used as an argument against the use of CT-guidance.”

Therefore, Artner et al retrospectively reviewed a prospective database in which a low-dose CT protocol was used for periradicular injections over a four-month period and compared it with data from patients who had received standard CT-guided periradicular injections. In the low-dose protocol, a CT-scanner (Somatom Emotion CT scanner syngoCT 2009E, 16-slice solution, Siemens) was put into “low-dose mode”—which involved a narrowing of the scanner area and a reduction of energy and tube current. Patients in both the standard and low-dose CT protocols were adult patients with radicular pain due to a lumbar disc herniation.

They found that the mean dose length product for 50 patients who received injections with the low-dose protocol was 13.87mGycm2 compared with 94.44mGycm2 for 50 patients who received injections with a standard CT protocol. Artner et al wrote: “Compared to 50 perineural injections performed in the conventional interventional CT-protocol, an average dose reduction of 85.31% could be achieved using the low-dose protocol.”

The dose reduction was achieved without an increase in the rate of complications and although the low-dose protocol was associated with lower image quality than the standard approach, it had good visibility when even the thinnest needle calibre was used. Artner et al commented that radiation doses at their institution (ranging from 1.30 to 1.44mSv), even when using the standard CT approach, were lower than those in the reported literature (eg, 3.3–9.1mSv) and said: “Using the low-dose protocol for periradcular injections, these doses could be once more reduced significantly. This underlines the need of further dose reduction and standardisation of settings.”

Concluding their paper, the authors stated that a low-dose protocol only required a short learning curve and was practical on most CT scanners. They added: “Reducing the cumulative radiation exposure in patients with spinal disorders undergoing CT-guided injections using thin needle systems which reduce tissue traumatisation as well as maintaining a good needle targeting using CT guidance in low-dose protocols contribute to an increase of patient safety.”