X-Ray Protective Aprons Re-Evaluated. / Röntgenschürzen ­ neu bewertet.

BACKGROUND: The evaluation of the protective effect of X-ray protective clothing requires new criteria. The current concept assumes more or less uniform covering of the torso with protective material. The frequently worn heavy wrap-around aprons can weigh 7 to 8 kg. As relevant studies show, orthopedic damage can result from long-term activity. It should therefore be investigated whether the apron weight can be reduced by optimizing the material distribution. For a radiobiological evaluation of the protective effect, the "effective dose" should be used. METHODS: Numerous laboratory measurements were performed with an Alderson Rando phantom as well as dose measurements on clinical personnel. The measurements were supplemented by Monte Carlo simulation of an interventional workplace in which a female ICRP reference phantom was used for the operator. The measured back doses on the Alderson phantom as well as the measured back doses at interventional workplaces were based on the personal equivalent dose Hp(10). Monte Carlo simulations were used to introduce protection factors for the protective clothing based on the "effective dose" introduced in radiation protection. RESULTS: Back doses in clinical radiology personnel are largely negligible. Therefore, back protection can be much lower than currently used or can even be eliminated. The Monte Carlo simulations show that the protective effect of protective aprons worn on the body is higher than when the flat protective material is radiated through (3 D effect). About 80 % of the effective dose is attributed to the body region from the gonads to the chest. By additional shielding of this area, the effective dose can be lowered or, optionally, aprons with less weight can be produced. Attention must also be paid to the "radiation leaks" (upper arms, neck, skull), which can reduce the whole-body protective effect. CONCLUSION: In the future, the evaluation of the protective effect of X-ray protective clothing should be based on the effective dose. For this purpose, effective dose-based protection factors could be introduced, while the lead equivalent should be used for measurement purposes only. If the results are implemented, protective aprons with approx. 40 % less weight can be produced with a comparable protective effect. KEY POINTS: · The protective effect of X-ray protective clothing should be described by protection factors based on effective dose.. · The lead equivalent should only be used for measurement purposes.. · More than 80 % of the effective dose is attributed to the body region from the gonads to the chest.. · A reinforcing layer in this area increases the protective effect considerably.. · With optimized material distribution, protective aprons could be up to 40 % lighter.. CITATION FORMAT: · Eder H. X-Ray Protective Aprons Re-Evaluated. Fortschr Röntgenstr 2023; 195: 234 - 243.

Use of effective dose to assess x-ray protective clothing.

This review article provides an overview on the results of studies conducted by the authors to improve the current personal protection concept in the clinical application of x-rays. With the aid of personal dose equivalent measurements during radiologically guided clinical interventions, laboratory tests using the Alderson-Rando phantom as well as Monte Carlo simulations various x-ray application scenarios were investigated. The organ doses and the effective doses of staff persons standing near the patient were determined. The 3D-attenuation properties of protective clothing under the scattered radiation emitted by the patient play a special role here. With regard to the minimisation of the quantity 'effective dose' the protection of the lower body from the gonads to the chest is of particular importance, since 80% of the effective dose is contributed by this region of the body. In contrast, protection of the back plays a subordinate role. Protective aprons optimised in terms of effective dose can be significantly lighter than conventional aprons, providing equal protection. The assessment of the attenuation properties of protective clothing should be based on the risk-related dose quantity, effective dose, rather than lead equivalent. In the future, the evaluation of radiation protective clothing could be based on the calculation of the effective dose assuming standardised irradiation conditions.

IEC 61331-1: A new setup for testing lead free X-ray protective clothing.

PURPOSE: Lead free protective clothing can create a higher part of secondary radiation (SR) than products that are based on lead. Hence, the attenuation properties may be downgraded. The international measuring standard IEC 61331-1:2014 declares the "inverse broad beam geometry" (IBG) as standard method, which has recently been modified to IBG∗ by the Physikalisch Technische Bundesanstalt (PTB). Because of the unspecific partial irradiation of the ionization chamber problems in the evaluation of lead equivalence values (LEVs) can occur. An alternative method proposed in this paper overcomes these problems. MATERIALS AND METHODS: The alternative setup "modified broad beam geometry" (BBG∗) was tested and compared to the IBG∗ method by performing Monte Carlo simulations and radiation measurements including several lead-composite and lead-free protective materials. RESULTS: Simulations show a reduced collection efficiency of SR under IBG∗ whereas BBG∗ features a high degree of SR collection. Material samples with a high amount of SR can feature up to 8% higher LEVs compared to IBG∗. For most of the currently salable materials the differences of BBG∗ vs IBG∗ amount to <3% (0.25 mm LEV) and <1% (0.50 mm LEV). In special cases the currently practiced method can lead to heavier protective clothings. CONCLUSIONS: The proposed BBG∗ setup meets the specifications of the IEC standard with respect to energy response and SR collection. The method should be implemented in the IEC standard.

Air-permeable hole-pattern and nose-droop control improve aerodynamic performance of primary feathers.

Primary feathers of soaring land birds have evolved into highly specialized flight feathers characterized by morphological improvements affecting aerodynamic performance. The foremost feathers in the cascade have to bear high lift-loading with a strong bending during soaring flight. A challenge to the study of feather aerodynamics is to understand how the observed low drag and high lift values in the Reynolds (Re) regime from 1.0 to 2.0E4 can be achieved. Computed micro-tomography images show that the feather responds to high lift-loading with an increasing nose-droop and profile-camber. Wind-tunnel tests conducted with the foremost primary feather of a White Stork (Ciconia ciconia) at Re = 1.8E4 indicated a surprisingly high maximum lift coefficient of 1.5 and a glide ratio of nearly 10. We present evidence that this is due to morphologic characteristics formed by the cristae dorsales as well as air-permeable arrays along the rhachis. Measurements of lift and drag forces with open and closed pores confirmed the efficiency of this mechanism. Porous structures facilitate a blow out, comparable to technical blow-hole turbulators for sailplanes and low speed turbine-blades. From our findings, we conclude that the mechanism has evolved in order to affect the boundary layer and to reduce aerodynamic drag of the feather.

Shielding properties of lead-free protective clothing and their impact on radiation doses.

The shielding properties of two different lead-free materials-tin and a compound of 80% tin and 20% bismuth-for protective clothing are compared with those of lead for three typical x-ray spectra generated at tube voltages of 60, 75, and 120 kV. Three different quantities were used to compare the shielding capability of the different materials: (1) Air-kerma attenuation factors in narrow-beam geometry, (2) air-kerma attenuation factors in broad-beam geometry, and (3) ratios of organ and effective doses in the human body for a whole-body irradiation with a parallel beam directed frontally at the body. The thicknesses of tin (0.45 mm) and the tin/bismuth compound (0.41 mm) to be compared against lead correspond to a lead equivalence value of 0.35 mm for the 75 kV spectrum. The narrow-beam attenuation factors for 0.45 mm tin are 54% and 32% lower than those for 0.35 mm lead for 60 and 120 kV; those for 0.41 mm tin/bismuth are 12% and 32% lower, respectively. The decrease of the broad-beam air-kerma attenuation factors compared to lead is 74%, 46%, and 41% for tin and 42%, 26%, and 33% for tin/bismuth and the spectra at 60, 75, and 120 kV, respectively. Therefore, it is recommended that the characterization of the shielding potential of a material should be done by measurements in broad-beam geometry. Since the secondary radiation that is mainly responsible for the shielding reduction in broad-beam geometry is of low penetrability, only more superficially located organs receive significantly enhanced doses. The increase for the dose to the glandular breast tissue (female) compared to being shielded by lead is 143%, 37%, and 45% when shielded by tin, and 35%, 15%, and 39% when shielded by tin/bismuth for 60, 75, and 120 kV, respectively. The effective dose rises by 60%, 6%, and 38% for tin, and 14%, 3% and, 35% for tin/bismuth shielding, respectively.

Personal dosimetry of exposure to mobile telephone base stations? An epidemiologic feasibility study comparing the Maschek dosimeter prototype and the Antennessa SP-090 system.

The aim of our study was to test the feasibility and reliability of personal dosimetry. Twenty-four hour exposure assessment was carried out in 42 children, 57 adolescents, and 64 adults using the Maschek dosimeter prototype. Self-reported exposure to mobile phone frequencies were compared with the dosimetry results. In addition, dosimetry readings of the Maschek device and those of the Antennessa DSP-090 were compared in 40 subjects. Self-reported exposures were not associated with dosimetry readings. The measurement results of the two dosimeters were in moderate agreement (r(Spearman) = 0.35; P = .03). Personal dosimetry for exposure to mobile phone base station might be feasible in epidemiologic studies. However, the consistency seems to be moderate.

Patient exposure in medical X-ray imaging in Europe.

Patients are exposed to X rays when undergoing medical examinations in diagnostic radiology. Exposure data acquired and assessed in Germany for the year 1997 resulted in a mean annual effective dose of 2 +/- 0.5 mSv per head of the population, thereby reaching or exceeding the average level of environmental radiation in many cases. The underlying frequency of medical X-ray examinations was approximately 136 million, i.e. approximately 1.7 examinations annually per head of the population. For comparison, corresponding data of other countries were extracted from the UNSCEAR 2000 report or originate from the literature. Data analysis shows significant differences in national radiological practices and a very uneven distribution of patient doses amongst the world population. The mean annual effective dose per head of the population varies by up to a factor of 60 between health care level I and IV countries, and still by a factor of approximately 6 within health care level I countries. While projection radiography has succeeded in reducing dose consumption, computed tomography and radiological interventions have given rise to a significant growth of patient exposure, and interventional radiology can even exceed thresholds for deterministic radiation effects. Patient exposure is further shown to result from misadministration and retakes of X-ray examinations, usually not registered, as well as from technical failures of X-ray facilities, which can cause significantly enhanced exposure times. Corresponding data are presented and comments are made on the international situation of non-harmonised data collection on patient exposure as well as of parameters affecting the assessment of exposure and risk.