Introduction: Modern digital fluoroscopy machines have computerized dose reduction algorithms that are operator-independent. In some, the dose-rate output of the fluoroscope is tied to a selectable patient size. While patient size may play a significant role in visceral or cardiac procedures, head morphology is less variable, and high dose outputs may not be necessary even in very obese patients. We hypothesized that very small patient size settings can be used to reduce dose for cerebral angiography without compromising image quality.
Methods: Patients who underwent endovascular neurosurgical procedures during the 2015-16 academic year were identified, and estimated procedural air kerma (AK) tabulated retrospectively. Technologists were instructed to begin using the very small patient size setting for all procedures performed using our Philips Allura Xper FD20 biplane fluoroscopy system beginning in March 2016. No changes were made in a second procedure room using a Toshiba Infinix system . Student t-tests and logistic regression models were used to compare radiation doses before and after March 1, 2016 for both machines.
Results: For diagnostic cerebral angiograms performed on the Philips system (n = 302), AK was reduced by approximately 17% (1,277 vs 1,061 mGy; p=0.0006.) Changes in table height, total fluoroscopy time, patient weight, and BMI did not contribute to this difference. No significant change was seen in total AK using the Toshiba system (n = 237), indicating that changes are not explained by increasing operator skill. A trend towards reduced AK was seen for aneurysms coiled primarily (3,126 vs 2,814 mGy; p=0.27), and no difference for flow diversion (2,446 vs 2,393 mGy; p=0.93.) No cases were identified where image quality was insufficient for diagnosis or treatment.
Conclusions: Using the very small patient size reduces fluoroscopy dose by 17% for cerebral angiography without impacting image quality. A trend in dose reduction was also seen in endovascular aneurysm treatment.
Patient Care: By reducing radiation dose in endovascular neurosurgery patients, we can reduce adverse events and side effects related to radiation exposure.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Identify radiation dose-reduction strategies in endovascular neurosurgery, and:
2) Recognize patient weight setting as an easily modifiable setting on many modern fluoroscopes