Interventional neuroradiology procedures may deliver lens radiation doses exceeding safe thresholds

1. Patients undergoing interventional neuroradiology procedures were often exposed to eye lens radiation doses that met or exceeded the threshold dose thought to produce lenticular opacities (500 mGy or higher).

Evidence Rating: 4 (Below Average)

Study Rundown: Neurointerventional procedures are known to deliver high doses of ionizating radiation to patients, particularly in the parts of the body closest to the lateral C-arm X-ray source. Recent epidemiologic studies have suggested that as little as 0.5 Gy may produce lenticular opacities, reducing the prior threshold for safety from 5 Gy. The current study examined the radiation doses delivered to each eye of 5 patients undergoing diagnostic and 31 patients undergoing therapeutic neuroradiology procedures using optically stimulated luminescence dosimeters. Overall, the left eye (closest to the C-arm radiation source) received a radiation dose 4.5 times greater than that delivered to the right. Average dose to the left eye during an embolization procedure was 300 mGy, with a maximum dose of 2000 mGy in one multi-embolization procedure. Sixteen percent of patients undergoing embolization procedures received suprathreshold eye doses greater than 500 mGy. Increased awareness of the radiation doses during these procedures is the first step in evaluating how to minimize radiation doses while maintaining diagnostic quality images. This study was significantly limited by its overall small size and nonrandomized nature. Future studies should focus on both delineating which types of procedures pose the greatest risk of high radiation doses but also on which techniques minimize radiation exposure without limiting quality.

Click to read the study in American Journal of Neuroradiology

Relevant reading: Dose Measurement on Both Patients and Operators during Neurointerventional Procedures Using Photoluminescence Glass Dosimeters

In-Depth [case series]: Five patients undergoing diagnostic cerebral angiography and 31 patients undergoing therapeutic procedures (13 arteriovenous malformation embolizations, 2 fistula embolizations and 16 aneurysm coilings) were randomly chosen at a single academic medical center in Spain, and radiation doses to the eye were measured using optically stimulated luminescence dosimeters (OSLDs) placed over the eyelids. Dose contribution from the conebeam CT was also evaluated using phantom simulations. These were carried out using a phantom model with OSLDs located over the phantom eyes. During CBCT irradiation, phantoms received 10 mGy in the low dose mode, and 20 mGy for high resolution images. Overall, diagnostic cases had a lower radiation dose than patients undergoing therapeutic procedures with mean delivered doses of 56±21 Gy x cm² vs 203±120 Gy x cm² respectively. The correlation between dose-area product (DAP) and the dose to the left eye was moderate (r² = 0.6). The OSLDs utilized were not specifically made for capturing radiation at an angle and issues with calibration and angular dependence were cited as potential factors reducing the reliability of the measured values, possibly increasing the level of inherent uncertainty to 20%.

Image: PD

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