Transition in occupational radiation exposure monitoring methods in diagnostic and interventional radiology

Radiation exposure monitoring is a traditional keystone of occupational radiation safety measures in medical imaging. The aim of this study was to review the data on occupational exposures in a large central university hospital radiology organisation and propose changes in the radiation worker categories and methods of exposure monitoring. An additional objective was to evaluate the development of electronic personal dosimeters and their potential in the digitised radiology environment. The personal equivalent dose of 267 radiation workers (116 radiologists and 151 radiographers) was monitored using personal dosimeters during the years 2006-2010. Accumulated exposure monitoring results exceeding the registration threshold were observed in the personal dosimeters of 73 workers (59 radiologists' doses ranged from 0.1 to 45.1 mSv; 14 radiographers' doses ranged from 0.1 to 1.3 mSv). The accumulated personal equivalent doses are generally very small, only a few angiography radiologists have doses >10 mSv per 5 y. The typical effective doses are <10 μSv y(-1) and the highest value was 0.3 mSv (single interventional radiologist). A revised categorisation of radiation workers based on the working profile of the radiologist and observed accumulated doses is justified. Occupational monitoring can be implemented mostly with group dosimeters. An active real-time dosimetry system is warranted to support radiation protection strategy where optimisation aspects, including improving working methods, are essential.     

Effects of menu structure and touch screen scrolling style on the variability of glance durations during in-vehicle visual search tasks

The effects of alternative navigation device display features on drivers' visual sampling efficiency while searching forpoints of interest were studied in two driving simulation experiments with 40 participants. Given that the number of display items was sufficient, display features that facilitate resumption of visual search following interruptions were expected to lead to more consistent in-vehicle glance durations. As predicted, compared with a grid-style menu, searching information in a list-style menu while driving led to smaller variance in durations of in-vehicle glances, in particular with nine item displays. Kinetic touch screen scrolling induced a greater number of very short in-vehicle glances than scrolling with arrow buttons. The touch screen functionality did not significantly diminish the negative effects of the grid-menu compared with physical controls with list-style menus. The findings suggest that resumability of self-paced, in-vehicle visual search tasks could be assessed with the measures of variance of in-vehicle glance duration distributions. Statement of Relevance: The reported research reveals display design factors affecting safety-relevant variability of in-vehicle glance durations and provides a theoretical framework for explaining the effects. The research can have a significant methodical value for driver distraction research and practical value for the design and testing of in-vehicle user interfaces.     

Effect of cognitive load on speech prosody in aviation: Evidence from military simulator flights

Mental overload directly affects safety in aviation and needs to be alleviated. Speech recordings are obtained non-invasively and as such are feasible for monitoring cognitive load. We recorded speech of 13 military pilots while they were performing a simulator task. Three types of cognitive load (load on situation awareness, information processing and decision making) were rated by a flight instructor separately for each flight phase and participant. As a function of increased cognitive load, the mean utterance-level fundamental frequency (F0) increased, on average, by 7 Hz and the mean vocal intensity increased by 1 dB. In the most intensive simulator flight phases, mean F0 increased by 12 Hz and mean intensity, by 1.5 dB. At the same time, the mean F0 range decreased by 5 Hz, on average. Our results showed that prosodic features of speech can be used to monitor speaker state and support pilot training in a simulator environment.     

High-power operation of aluminum-free (κ=0.98 μm) pumplaser for erbium-doped fiber amplifier

The authors discuss the fabrication and characteristics of high-power (P_CW=430 mW) InGaAs/InGaAsP/InGaP ridge waveguide lasers emitting at λ=0.98 μm, which is the optimum wavelength for pumping erbium-doped fiber amplifiers. In the past, high-power operation of Al-free pump lasers has been limited to 150 mW because of catastrophic optical damage of the mirror facet. This problem has been largely removed by increasing the spot size of the laser with the aid of an improved waveguide design. As a result, Al-free lasers can now achieve a maximum power comparable to the conventional GaAlAs-based pump lasers for λ=0.98 μm     

Novel detector implementations for 3G LTE downlink and uplink

We summarize our recent state-of-the-art programmable and reconfigurable detector and QR decomposition (QRD) implementations targeting 3G long term evolution (LTE) downlink and uplink requirements. The downlink transmission is based on the orthogonal frequency division multiplexing, whereas the uplink transmission uses a single-carrier frequency-division multiple access. The downlink implementations are based on the programmable transport triggered architecture (TTA) which provides a flexible and energy efficient architecture template. In TTA detector implementation, the LTE detection rate requirements up to 20 MHz bandwidth and 4 × 4 antenna system with 64-QAM, are achieved by using 1–6 programmable cores in parallel. Each core runs at 277 MHz clock frequency and consumes 55.5–64.0 mW depending on the detector configuration. The downlink detector is based on the selective spanning with fast enumeration algorithm. The uplink field-programmable gate array (FPGA) detector implementation is targeted for 4 × 4 antenna system and 64-QAM achieving a detection rate requirement for 20 MHz bandwidth. The used FPGA board for uplink implementation is Xilinx Virtex-6 and the implementation has been carried out using Xilinx Vivado high level synthesis tool. Two different detector architectures are implemented. The first one achieves the detection rate requirement with a single processing block running at 231 MHz and the latter one with four blocks in parallel, each running at 247 MHz. The implemented detector is based on the K-best algorithm. A multiple-input multiple-output receiver requires QRD to produce valid inputs for the detector. In addition to detector implementations, QRD is also implemented on both TTA and FPGA. Modified Gram–Schmidt algorithm is used in both QRD implementations.     

Personal radiation doses in PET/CT facility: measurements vs. calculations

The estimation of shielding requirement of a new positron emission tomography (PET) facility is essential. Because of penetrating annihilation photons, not only radiation safety in the vicinity of patients should be considered, but also rooms adjacent to uptake and imaging rooms should be taken into account. Before installing a PET/CT camera to nuclear medicine facilities of Helsinki University Central Hospital (HUCH), a typical PET imaging day was simulated using phantoms. Phantoms were filled with 300 +/- 36 MBq of (18)F isotope and dose rates were measured at 12 central locations in the laboratory. In addition to measurements, dose rates were also calculated using guidelines of AAPM Task Group 108. The relationship between the measured and calculated dose rates was found to be good and statistically significant, using Pearson's correlation test. The evaluated monthly doses were compared with personal dosemeter readings. AAPM's report gives practical tools for evaluation of radiation shielding. Calculations can be carried out successfully for existing hospital complexes too. However, calculations should be carried out carefully, because especially doors, windows and partitions can easily cause underestimation of shielding requirements as shown in this work.     

Integral equation formulation for scatter density problem

Integral equation formulation for the problem of finding a circularly symmetric scatter density (SD) around the mobile is deduced, and the SD is computed assuming that the distribution of angle-of-arrival (AoA) in the base station is known. The corresponding integral equation is solved by using the spline collocation method. Thus, instead of fitting a priori selected SD to estimated AoA distribution, the SD is solved based on AoA characteristics.     

Bayesian Fusion for Indoor Positioning Using Bluetooth Fingerprints

This paper studies the use of received signal strength indicators (RSSI) applied to fingerprinting method in a Bluetooth network for indoor positioning. A Bayesian fusion (BF) method is proposed to combine the statistical information from the RSSI measurements and the prior information from a motion model. Indoor field tests are carried out to verify the effectiveness of the method. Test results show that the proposed BF algorithm achieves a horizontal positioning accuracy of about 4.7 m on the average, which is about 6 and 7 % improvement when compared with Bayesian static estimation and a point Kalman filter method, respectively.