Abstract
Objective
Radiation induced cataract has been observed at lower threshold doses than expected. Therefore, the annual limit for equivalent dose to the eye lens has been reduced from 150 to 20 mSv. We aimed to evaluate radiation exposure to the eye lens of vascular surgeons working in a hybrid operating room before and after a dose reduction program was established.
Methods
Prospective non-randomized trial with a historic control group. From April – October 2019, radiation exposure to the operator was measured during all endovascular procedures performed in the hybrid operating room using BeOSL Hp(3) eye lens dosimeters placed outside the 0.75mm lead equivalent glasses on the side of the radiation source and behind the lead glasses. Measured values were compared to data from a prospective study performed at the same center in the years of 2012 and 2013 before a dose reduction program had been implemented.
Results
A total of 181 consecutive patients underwent an endovascular procedure in the hybrid operating room. The mean unprotected eye lens dose of the main operator was 0.119 mSv for EVAR (n = 30), 0.118 mSv for TEVAR (n = 23), 0.312 mSv for more complex aortic procedures (F/BrEVAR; n = 15) and 0.046 mSv for peripheral interventions.
Compared to the control period, EVAR had 75% lower, TEVAR 79% lower and more complex aortic procedures 55% lower radiation exposure unprotected eye lens of the operator. The 0.75 mm lead equivalent glasses led to a median reduction of the exposure to the eye lens by the factor 3.43. Behind the lead glasses at the level of the eye lens, radiation exposure exceeding the detection limit of 0.042 mSv was measured only in 22 of 181 cases. There was a significant correlation between DAP between both protected and unprotected eye lens dose (p < 0.0001, r2 = 0.512 and 0.282). DAP correlated significantly with patients’ body mass index, operating time, fluoroscopy time and digital subtraction angiography time.
Conclusion
The dose reduction program at our institution has led to a relevant reduction of the radiation dose to the head and the eye lens of the main operator in endovascular procedures. With optimum radiation protection measures including a ceiling-mounted shield and 0.75 mm lead equivalent glasses, more than 440 EVARs, 280 TEVARs or 128 FEVARs could be performed per year until the dose limit for the eye lens of 20 mSv would be reached.
Monte Carlo simulation of eye lens dose reduction from CT scan using organ based tube current modulation