Image quality can be maintained while reducing patient radiation dose

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By Hannah Woolley

Substantial radiation dose reduction (62%) with a live peripheral image can be achieved without compromising feature visibility during neuroendovascular interventions. That is what researchers from the State University of New York, Gates Vascular Institute at Kaleida Health, and the Jacobs Institute (all New York, USA) have found. The results were published in the American Journal of Neuroradiology.

In 2010, the US FDA Centre for Devices and Radiological Health launched an initiative to reduce unnecessary radiation exposure from medical imaging. These efforts were in response to increasing exposure to ionising radiation from medical imaging highlighted in the National Council on Radiation Protection and Measurements Report No. 160 and safety concerns highlighted in FDA’s Safety Investigation of CT Brain Perfusion Scans.

Since then there has been an increase in research looking to reduce radiation exposure.

The study set out to see if X-ray dose could be reduced while maintaining image quality, and the group compared image quality of simulated neurointerventions with regular and reduced radiation doses using a standard flat panel detector system.

Ten 3D-printed intracranial aneurysm models were generated on the basis of a single patient vasculature derived from intracranial digital subtraction angiography and CT angiography. The incident dose given to each model was reduced using a 0.7mm thick copper attenuator with a circular 10mm region of interest (ROI) hole. Each model was treated twice with a primary coiling intervention using ROI-dose-reduced intervention and regular-dose intervention protocols. For each aneurysm coiling intervention, a set of four images were generated at various stages of the intervention. Thus, each intervention generated eight images. Overall, 80 images were acquired at various interventional stages. They were shown twice to two neurointerventionalists who independently scored image quality (visibility of aneurysm-parent vessel morphology, associated vessels, and/ or devices used). Both were blinded to patient data and ROI status. Each aneurysm was treated using both the ROI-dose-reduction intervention (ROIDRI) and the regular-dose intervention (RDI) protocols and dose-reduction measurements were performed using an ionisation chamber.

For each defined stage, image quality was rated in three categories: Unacceptable, when it was difficult to discern any of the following: Vessel morphology, aneurysm morphology, and devices. Acceptable, when it was easy to discern all the following: Vessel morphology, aneurysm morphology, and devices. High, when the discernibility was superior to the rater’s experience with conventional angiography in all of the following: Vessel morphology, aneurysm morphology, and devices.

The Wilcoxon signed rank sum test was used to compare the scores from the neurointerventionalists’ ratings of the RDI and ROI-DRI images.

For each frame a total integral dose reduction of 62% was achieved, while the mean scores for regular-dose intervention and ROI dose-reduced intervention images did not differ significantly, suggesting similar image quality. Overall intra-rater agreement for all scored criteria was substantial (Kendall τ=0.62887; p˂ .001) and overall inter-rater agreement for all criteria was fair (κ=0.2816; 95% CI,0.2060–0.3571).

This study demonstrated a (simulated) neurointervention in a reduced-dose environment using the

technique of dose reduction with a clear, real-time view of the periphery was similar in image quality to a standard dose paradigm. This study suggests that incorporation of dose-reduced intervention should allow for a marked reduction in radiation exposure to both the patient and surgeons, without compromising the ability to visualise critical anatomy and devices.

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