G. Solomou

Data and methods to assess occupational exposure to personnel involved in cardiac catheterization procedures

PURPOSE To provide normalized scatter exposure data and methods for reliable estimation of cumulative effective dose and eye-lens equivalent dose to personnel involved in fluoroscopically guided cardiac catheterization (FGCC) procedures. METHODS An anthropomorphic phantom was placed supine on the table of a modern digital C-arm angiographic system and 17 different fluoroscopic projections commonly employed during FGCC procedures were represented. Scatter exposure rates at the waist and eye level were measured for varying exposure parameters and position in the operating room. The effect of beam field size, patient size, use of radioprotective garments and small variations in projection angulation and table height on scatter radiation was investigated. RESULTS Apart from the position and use of radio-protective garments, radiation burden to operators during fluoroscopic guidance was found to remarkably depend beam field size (>45% reduction if a 10 × 10 cm(2) instead of 15 × 15 cm(2) fluoroscopy beam is used) and patient size (>25% increased scatter for obese patients). In contrast, the variation of measured scatter exposure from a given projection was found to be <10% when the source to skin distance was altered by ±10 cm or beam angulation of a specific projection was altered by ±10°. CONCLUSION Presented scatter exposure data charts and methods allow for prospective and retrospective estimation of effective dose and eye-lens equivalent dose to personnel involved in any FGCC procedure. Projection specific maps of scatter exposure produced may enhance familiarization of involved medical staff to good radiation protection practice and optimization of working habits in the cardiac catheterization lab.

Data and methods to estimate fetal dose from fluoroscopically guided prophylactic hypogastric artery balloon occlusion

PURPOSE To provide data for estimation of fetal radiation dose (DF) from prophylactic hypogastric artery balloon occlusion (HABO) procedures. METHODS The Monte-Carlo-N-particle (MCNP) transport code and mathematical phantoms representing a pregnant patient at the ninth month of gestation were employed. PA, RAO 20° and LAO 20° fluoroscopy projections of left and right internal iliac arteries were simulated. Projection-specific normalized fetal dose (NFD) data were produced for various beam qualities. The effects of projection angle, x-ray field location relative to the fetus, field size, maternal body size, and fetal size on NFD were investigated. Presented NFD values were compared to corresponding values derived using a physical anthropomorphic phantom simulating pregnancy at the third trimester and thermoluminescence dosimeters. RESULTS NFD did not considerably vary when projection angle was altered by ±5°, whereas it was found to markedly depend on tube voltage, filtration, x-ray field location and size, and maternal body size. Differences in NFD < 7.5% were observed for naturally expected variations in fetal size. A difference of less than 13.5% was observed between NFD values estimated by MCNP and direct measurements. CONCLUSIONS Data and methods provided allow for reliable estimation of radiation burden to the fetus from HABO.

MO-F-CAMPUS-I-02: Occupational Conceptus Doses From Fluoroscopically-Guided Interventional Procedures

Purpose: The aim of this method was to provide dosimetric data on conceptus dose for the pregnant employee who participates in fluoroscopically-guided interventional procedures. Methods: Scattered air-kerma dose rates were obtained for 17 fluoroscopic projections involved in interventional procedures. These projections were simulated on an anthropomorphic phantom placed on the examination table supine. The operating theater was divided into two grids relative to the long table sides. Each grid consisted of 33 cells spaced 0.50 m apart. During the simulated exposures, at each cell, scatter air-kerma rate was measured at 110 cm from the floor i.e. at the height of the waist of the pregnant worker. Air-kerma rates were divided by the dose area product (DAP) rate of each exposure to obtain normalized data. For each projection, measurements were performed for 3 kVp and 3 filtration values i.e. for 9 different x-ray spectra. All measurements were performed by using a modern C-arm angiographic system (Siemens Axiom Artis, Siemens, Germany) and a radiation meter equipped with an ionization chamber. Results: The results consist of 153 iso-dose maps, which show the spatial distribution of DAP-normalized scattered air-kerma doses at the waist level of a pregnant worker. Conceptus dose estimation is possible using air-kerma to embryo/fetal dose conversion coefficients published in a previous study (J Cardiovasc Electrophysiol, Vol. 16, pp. 1–8, July 2005). Using these maps, occupationally exposed pregnant personnel may select a working position for a certain projection that keeps abdominal dose as low as reasonably achievable. Taking into consideration the regulatory conceptus dose limit for occupational exposure, determination of the maximum workload allowed for the pregnant personnel is also possible. Conclusion: Data produced in this work allow for the anticipation of conceptus dose and the determination of the maximum workload for a pregnant worker from any fluoroscopically-guided interventional procedure. This study was supported by the Greek Ministry of Education and Religious Affairs, General Secretariat for Research and Technology, Operational Program ‘Education and Lifelong Learning’, ARISTIA (Research project: CONCERT).