Past and present work practices of European interventional cardiologists in the context of radiation protection of the eye lens-results of the EURALOC study.

This paper investigates over five decades of work practices in interventional cardiology, with an emphasis on radiation protection. The analysis is based on data from more than 400 cardiologists from various European countries recruited for a EURALOC study and collected in the period from 2014 to 2016. Information on the types of procedures performed and their annual mean number, fluoroscopy time, access site choice, x-ray units and radiation protection means used was collected using an occupational questionnaire. Based on the specific European data, changes in each parameter have been analysed over decades, while country-specific data analysis has allowed us to determine the differences in local practices. In particular, based on the collected data, the typical workload of a European cardiologist working in a haemodynamic room and an electrophysiology room was specified for various types of procedures. The results showed that when working in a haemodynamic room, a transparent ceiling-suspended lead shield or lead glasses are necessary in order to remain below the recommended eye lens dose limit of 20 mSv. Moreover, the analysis revealed that new, more complex cardiac procedures such as chronic total occlusion, valvuloplasty and pulmonary vein isolation for atrial fibrillation ablation might contribute substantially to annual doses, although they are relatively rarely performed. The results revealed that considerable progress has been made in the use of radiation protection tools. While their use in electrophysiology procedures is not generic, the situation in haemodynamic procedures is rather encouraging, as ceiling-suspended shields are used in 90% of cases, while the combination of ceiling shield and lead glasses is noted in more than 40% of the procedures. However, we find that still 7% of haemodynamic procedures are performed without any radiation protection tools.

Obesity is a major determinant of radiation dose in patients undergoing pulmonary vein isolation for atrial fibrillation.

OBJECTIVES: This study sought to evaluate the impact of obesity on patient radiation dose during atrial fibrillation (AF) ablation procedures under fluoroscopic guidance. BACKGROUND: Obesity is a risk factor for AF and its recurrence after ablation. It increases patient radiation dose during fluoroscopic imaging, but this effect has not been quantified for AF ablation procedures. METHODS: Effective radiation dose and lifetime attributable cancer risk were calculated from dose-area product (DAP) measurements in 85 patients undergoing AF ablation guided by biplane low-frequency pulsed fluoroscopy (3 frames/s). Three dose calculation methods were used (Monte Carlo simulation, dose conversion coefficients, and depth-profile dose curves). RESULTS: Median DAP for all patients was 119.6 Gy x cm2 (range 13.9 to 446.3 Gy x cm2) for procedures with a median duration of 4 h and 83 +/- 26 min of fluoroscopy. Body mass index was a more important determinant of DAP than total fluoroscopy time (r = 0.74 vs. 0.37, p < 0.001), with mean DAP values per hour of fluoroscopy of 58 +/- 40 Gy x cm2, 110 +/- 43 Gy x cm2, and 184 +/- 79 Gy x cm2 in normal, overweight, and obese patients, respectively. The corresponding effective radiation doses for AF ablation procedures were 15.2 +/- 7.8 mSv, 26.7 +/- 11.6 mSv, and 39.0 +/- 15.2 mSv, respectively (Monte Carlo). Use of conversion coefficients resulted in higher effective dose estimates than other methods, particularly in obese patients. Mean attributable lifetime risk of all-cancer mortality was 0.060%, 0.100%, and 0.149%, depending on weight class. CONCLUSIONS: Obese patients receive more than twice the effective radiation dose of normal-weight patients during AF ablation procedures. Obesity needs to be considered in the risk-benefit ratio of AF ablation and should prompt further measures to reduce radiation exposure.

Evaluation of a radiation protection cabin for invasive electrophysiological procedures.

AIMS: Complex invasive electrophysiological procedures may result in high cumulative operator radiation exposure. Classical protection with lead aprons results in discomfort while radioprotection is still incomplete. This study evaluated the usefulness of a radiation protection cabin (RPC) that completely surrounds the operator. METHODS AND RESULTS: The evaluation was performed independently in two electrophysiology laboratories (E1-Leuven, Belgium; E2-Bordeaux, France), comparing operator radiation exposure using the RPC vs. a 0.5 mm lead-equivalent apron (total of 135 procedures). E1 used thermoluminiscent dosimeters (TLDs) placed at 16 positions in and out of the RPC and nine positions in and out of the apron. E2 used more sensitive electronic personal dosimeters (EPD), placed at waist and neck. The sensitivity thresholds of the TLDs and EPDs were 10-20 microSv and 1-1.5 microSv, respectively. All procedures could be performed unimpeded with the RPC. Median TLD dose values outside protected areas were in the range of 57-452 microSv, whereas doses under the apron or inside the RPC were all at the background radiation level, irrespective of procedure and fluoroscopy duration and of radiation energy delivered. In addition, the RPC was protecting the entire body (except the hands), whereas lead apron protection is incomplete. Also with the more sensitive EPDs, the radiation dose within the RPC was at the sensitivity threshold/background level (1.3+/-0.6 microSv). Again, radiation to the head was significantly lower within the RPC (1.9+/-1.2 microSv) than with the apron (102+/-23 microSv, P<0.001). CONCLUSION: The use of the RPC allows performing catheter ablation procedures without compromising catheter manipulation, and with negligible radiation exposure for the operator.

Quantification of Al-equivalent thickness of just visible microcalcifications in full field digital mammograms.

Characterization of digital mammography systems is often performed by means of contrast-detail curves using a homogeneous phantom with inserts of different sizes and thicknesses. In this article, a more direct measure of the threshold contrast-detail characteristics of microcalcifications in clinical mammograms is proposed, which also takes into account routine processing and display. The proposed method scores the detectability of simulated microcalcifications with known size and aluminum-equivalent thickness. Thickness estimates, based on x-ray transmission coefficients, were first validated for Al particles. The same approach was then applied to associate Al-equivalent thickness with simulated microcalcifications. Thirty-five mammograms of patients were acquired using a full field digital mammography (FFDM) system operating under standard exposure conditions. Different microcalcifications were simulated using templates of real microcalcifications as described in Med. Phys. 30, 2234-2240 (2003). These templates were first modified such that they simulated a template of the same microcalcification for an ideally sharp detector. They were then adjusted for the imaging characteristics of the FFDM, beam quality, and breast thickness. Microcalcification sizes in the image plane ranged from 200 to 800 microm. Their peak Al-equivalent thickness varied between 70 and 1000 microm. Software phantoms were created. They consisted of 0-10 simulated microcalcifications randomly distributed in 2 cm by 2 cm frames embedded within digital mammograms. Routine processing and printing followed. Three experienced radiologists recorded the locations of the microcalcifications, and confidence ratings were given. Free response receiver operating characteristics (FROC) analysis was performed. Using a binary score, the fractions of detected microcalcifications were plotted as a function of equivalent diameter for the different Al-equivalent thicknesses. Pair-wise agreement of the detected microcalcifications was calculated for the different Al-equivalent thickness groups. The FROC curves of each radiologist indicated similar true positive fractions for a given number of false positives per image. One radiologist applied a more conservative scoring. Detected fractions for the different sizes of the microcalcifications showed the same trend for all observers. In addition, the observer with the least FP also detected less microcalcifications. The pair-wise agreement of the detected microcalcifications was good. The average detected fractions were >0.5 for microcalcifications with equivalent diameter >400 microm and Al-equivalent thickness >400 microm. An average detected fraction >0.5 was also seen for microcalcifications with equivalent diameter <400 microm and equivalent thickness >800 microm. The detected fractions of smaller microcalcifications were <0.5. The results obtained with this method indicate that it may be possible to quantify the performance of a digital mammography detector including processing and viewing for the detection of microcalcifications. We hypothesize that the FROC curves and detected fractions of simulated microcalcifications of different sizes reflect the clinical reality.