Eye lens dose levels in interventional rooms using simple phantom simulation, dose management software and Monte Carlo method of uncertainty assessment

RELATIONSHIPS BETWEEN TYPES OF PROTECTIVE EYEWEAR AND EYE LENS DOSE WITHIN ENDOSCOPIC RETROGRADE CHOLANGIOPANCREATOGRAPHY

In this study, variations in eye lens dose across different types of protective operator eyewear as well as the most appropriate protective methods when conducting endoscopic retrograde cholangiopancreatography were evaluated. The eye lens doses of 10 types of commercially available protective eyewear were compared. The ratio of the measured value near the eye to the measured value at the eye lens position ranged from 0.65 to 5.40 and it varied according to the mounting position of the dosemeter as well as the type of protective eyewear. Thus, the eye lens dose may have been overestimated or underestimated. Regardless of the working conditions, a face shield type of protective eyewear is recommended to reduce the eye lens dose. Moreover, it is preferable to attach a lens dosemeter near the eye to measure and evaluate the eye lens dose.

Estimating radiation exposure of the brain of a physician with a protective flap in interventional radiology: A phantom study

PURPOSE

The efficiency of protective equipment for the brain has not been verified at the left anterior oblique (LAO) position, which is commonly used in clinical procedures. The purpose of this study was to investigate radiation exposure of the brain in interventional radiology (IR) and the shielding ability of a new protective flap.

METHODS

We made a flap that combined a protective cap with a left lateral face shield. The flap was made of tungsten-containing rubber (TCR). An anthropomorphic head phantom was placed at the physician's position, and air kerma rates (μGy/min and μGy/15s) were measured by electronic dosimeter at three locations: the surface of the left side of the head, and the left and right temporal lobes with the protective cap and the flap in fluoroscopy and cine modes. The X-ray tube was at the lower left side of the physician, and its angles were LAO60 and LAO60CAU40. The tube voltage (95-125 kV), tube current (4.7-732 mA), and air kerma rate (27.8-1078 mGy/min) were automatically adjusted by the X-ray system. We obtained the cap and the flap shielding efficiencies.

RESULTS

In cine mode at LAO60CAU40, the shielding efficiencies on the surface of the left side of the head and left temporal lobe with the cap were 92.6% and 5.1%, respectively, and the corresponding shielding efficiencies with the flap were 92.5% and 86.1%, respectively. The flap can reduce radiation exposure of the brain more than the cap alone.

CONCLUSIONS

At the left anterior oblique in interventional radiology, the flap can reduce exposure to the brain.

Evaluation of calibration factor of OSLD toward eye lens exposure dose measurement of medical staff during IVR

The eye lens is a sensitive organ of which an x‐ray exposure dose should be managed during interventional radiology (IVR). In the actual situations, the eye lens is exposed to scattered x‐rays; they have different from the standard x‐ray energies which are used for general dose calibration of the dosimeter. To perform precise dose measurement, the energy dependence of the dosimeter should be properly accounted for when calibrating the dosimeter. The vendor supplies a calibration factor using 80‐kV diagnostic x‐rays under a free‐air condition. However, whether it is possible to use this calibration factor to evaluate the air kerma during the evaluation of the eye lens dose is unclear. In this paper, we aim to precisely determine calibration factors, and also examine the possible application of using a vendor‐supplied calibration factor. First, the x‐ray spectrum at the eye lens position during fluoroscopy was measured with a CdTe x‐ray spectrometer. We mimicked transfemoral cardiac catheterization using a human‐type phantom. Second, we evaluated the doses and calibration factors at three dosimetric points: front and back of protective goggles, and the front of the head (eye lens position). We used the measured x‐ray spectrum to determine the incident photon distribution in the eye lens regions, and x‐ray spectra corresponding to the dosimetric points around the eye lens were estimated using Monte Carlo simulation. Although the calibration factors varied with dosimetric positions, we found that the factors obtained were similar to the vendor‐supplied calibration factor. Furthermore, based on the experiment, we propose a practical way to calibrate an OSL dosimeter in an actual clinical situation. A person evaluating doses can use a vendor‐supplied calibration factor without any corrections for energy dependences, only when they add a systematic uncertainty of 5%. This evidence will strongly support actual exposure dose measurement during a clinical study.

Assessment of the Annual Eye Lens Dose for Cardiologists During Interventional Procedures Using Anthropomorphic Phantoms and mEyeDose_X Tool

OBJECTIVES

In this study, eye lens dose measurements were performed using two anthropomorphic phantoms simulating the cardiologist and patient during interventional procedures.

BACKGROUND

Interventional procedures known as areas with high potential risk and the cardiologists can receive relatively high doses to their eyes.

METHODS

This study was comprised of both phantom and computer simulations. Thermoluminescent dosimeters (TLDs) and mEyeDose_X tool were used to measure and calculate eye lens doses for the cardiologist. 144 TLDs measurements were performed using cardiac protocol for three angiographic projections: anterior-posterior (AP), left anterior oblique 90° (LAO90) and left anterior oblique 45° with cranial 30° (spider) angulations. All cine and fluoroscopy modes including the projections used in this study performed with and without protection tools.

RESULTS

The annual equivalent doses with protective tools using mEyeDose_X were found to be 1.831 and 1.424 mSv/year, whereas the values using phantom were found to be 2.204 and 1.802 mSv/year for the lens of lift and right eye respectively.

CONCLUSION

The annual doses reported in this study are almost comparable to other studies performed on interventional cardiology (IC) procedures. The highest dose rate in the lens was 20.21 ± 0.015 mSv/h without protective tools in cine mode for spider projection. Cardiologists may therefore easily exceed the lens dose limit if protective tools are not used.