EP1549220B1 - Radiation protection material based on silicone - Google Patents

Description

The invention relates to a lightweight lead replacement material for radiation protection purposes in the energy range of an x-ray tube with a voltage of 60-140 kV.

Conventional radiation protection clothing for use in X-ray diagnostics usually contains lead or lead oxide as protective material.

• Zum einen führt Blei und seine Verarbeitung aufgrund seiner Toxizität zu einer hohen Umweltbelastung, zum anderen führt Blei aufgrund seines sehr hohen Gewichts notwendigerweise zu einem sehr hohen Gewicht der Schutzkleidung und damit zu einer starken physischen Belastung des Anwenders. Beim Tragen von Schutzkleidung, beispielsweise bei medizinischen Operationen, ist das Gewicht für den Tragekomfort und die physische Belastung des Arztes und des Assistenzpersonals von großer Bedeutung.

Substitution of this protective material for other materials is desirable, in particular, for the following reasons:

• On the one hand leads lead and its processing due to its toxicity to a high environmental impact, on the other hand leads lead due to its very high weight necessarily to a very high weight of the protective clothing and thus to a strong physical burden on the user. When wearing protective clothing, for example during medical operations, the weight is of great importance for the wearing comfort and the physical stress of the physician and the assistant personnel.

Therefore, for years, a replacement lead material has been sought in radiation protection. Here, the use of chemical elements or their compounds with the atomic number of 50 to 76 is mainly proposed.

The DE 199 55 192 A1 describes a method for producing a radiation protection material from a polymer as matrix material and the powder of a metal of high atomic number.

The DE 201 00 267 U1 describes a highly elastic, lightweight, flexible, rubbery radiation protection material, with additions of chemical elements and their oxides with an atomic number greater than or equal to 50 is added to a particular polymer.

To reduce weight compared to conventional lead aprons is in the EP 0 371 699 A1 proposed a material which also has elements of higher atomic number in addition to a polymer as a matrix. This is called a large number of metals.

The DE 102 34 159 A1 describes a lead substitute material for radiation protection purposes in the energy range of an x-ray tube with a voltage of 60-125 kV.

Another essential component of the lead substitute materials is the matrix material, which should perform at least two functions. By matrix material is meant the carrier layer for the protective materials, which may consist of rubber, latex, flexible or solid polymers, for example. On the one hand, it is desirable for the end product to be as light, elastic and flexible as possible, without cracks or breaks occurring during subsequent processing. On the other hand, it should be ensured that the metallic fillers are distributed absolutely homogeneously, provided that they are firmly embedded in the matrix material, so that a satisfactory abrasion-resistant surface is ensured.

Another issue is the environmental compatibility of the matrix materials. Many conventional materials are halogenated polymers, e.g. As PVC, before. The use of these materials inevitably leads to serious problems in the production, use and recycling of the lead replacement materials, not only for the environment but also for those who come in direct contact with the lead replacement materials.

Furthermore, it has been found that the conventional absorption materials sometimes considerable tend to emit fluorescence radiation, which is a non-negligible health impact on the contact persons.

Depending on the elements used, the degree of attenuation or the lead equivalent (International Standard IEC 61331-1, Protective devices against diagnostic medical X-radiation) of the respective material shows a partially very pronounced dependence on the beam energy, which is a function of the voltage of the X-ray tube.

Lead-free materials have lead behavior that differs greatly from that of lead, depending on the X-ray energy. Therefore, for simulating the absorption behavior of lead while maximizing weight savings, an advantageous combination of different elements is required.

Thus, the known radiation protective clothing made of lead-free material compared to lead a more or less severe drop in absorption below 70 kV and above 110 kV, especially about 125 kV. That is, to achieve the same shielding effect as with leaded material, a higher basis weight of protective clothing is required for this range of tube tension.

Therefore, the scope of commercial lead-free radiation protection clothing is usually limited.

From the US 2002/0179860 For example, a radiation protection material comprising a rubber and a metal such as tungsten and / or bismuth is known. As the rubber to be used, silicone rubber is mentioned. The radiation protection materials provide protection in an energy range from 1173 kV to 1332 kV.

In order to substitute lead for radiation protection purposes, one is as similar as possible to lead Absorptive behavior over a wider energy range is required since radiation protection agents are usually classified according to the lead equivalent value and the radiation protection calculations are often based on lead equivalents.

Total lead equivalent in a protective-layer-shaped construction of a lead substitute material is understood to be the lead equivalent of the sum of all protective layers. The total nominal equivalent value is understood to mean the lead equivalent value specified by the manufacturer of personal protective equipment according to DIN EN 61331-3.

X-ray voltages of up to 140 kV occur in certain X-ray applications, such as computed tomography and bone density measurements, as well as in luggage inspection equipment.

The object of the present invention is to provide a lead substitute material which can be used over a wide energy range of an X-ray tube, ie over a large energy range and at the same time contains a matrix material that is environmentally friendly, free of pollutants, against UV radiation is stable.

The object of the invention is achieved in a first embodiment by a lead replacement material for radiation protection purposes in the energy range of an x-ray tube with a voltage of 60-140 kV, wherein the lead substitute 12-22 wt .-% of a silicone-based material as a matrix material, 1 -39% by weight of tin or tin compounds, 16-60% by weight of tungsten or tungsten compounds, 16-60% by weight of bismuth or bismuth compounds. The mixture detects nominal total lead values of 0.25-2.0 mm.

The object of the invention is achieved in a second embodiment by a lead replacement material for radiation protection purposes in the energy range of an x-ray tube with a voltage of 60-140 kV, wherein the lead substitute 12-22 wt .-% of a silicone-based material as matrix material, 40th -60% by weight of tin or tin compounds, 7-15% by weight of tungsten or tungsten compounds, 7-15% by weight of bismuth or bismuth compounds. The mixture also records nominal total lead values of 0.25-2.0 mm.

The solution to the problem was to find a choice of material in terms of the matrix material and the lead-substitute metals and their quantity selection, the X-ray radiation can also effectively shield in the high energy range, at the same time by the choice of silicone-based material, a lead substitute material is provided, which can meet the environmental requirements described above while maintaining a high elasticity.

Surprisingly, it has been found that the absorption effect at high energies by high proportions of tungsten and / or bismuth in the lead replacement material significantly improved.

It has been found that any silicone-based material is suitable as the matrix material, provided that it ensures a completely homogeneous, fine, uniform distribution of the metals or their compound. Preferred silicone rubbers are those which have alkyl groups, vinyl groups and / or phenyl groups on the polymer chain. Especially suitable Silicone rubber proved. Examples thereof include dimethylsilicone rubber, phenylmethyl rubber, phenylsilicone rubber and polyvinyl rubber.

In a further particularly preferred embodiment of the invention, the lead substitute material is characterized in that it additionally contains up to 40 wt .-% of one or more of the following elements Er, Ho, Dy, Tb, Gd, Eu, Sm and / or their compounds and or CsI includes.

Table 1 below shows the mass attenuation coefficients of lead-free protective substances outside the absorption edges at different photon energies. The advantageous elements to be used for the respective energy are underlined. Table 1 energy
(KeV) sn Gd He W Bi 40 19.42 6.92 8.31 10.67 14.95 50 10.70 3.86 4.63 5.94 8.38 60 6.56 11.75 13.62 3.71 5.23 80 3.03 5.57 6.48 7.81 2.52 100 1.67 3.11 3.63 4.43 5.74 150 0.61 1.10 1.28 1.58 2.08

By the lead substitute material, which additionally comprises one or more of the elements Er, Ho, Dy, Tb, Gd, Eu, Sm and / or their compounds and / or CsI, a particularly strong increase in the absorption effect is achieved. In this way, the weight of the protective clothing can be significantly reduced.

To achieve the described properties, according to Table 1, the individual elements can be arranged so that a certain energy range is covered or that as uniform a course of the weakening results over a larger energy range.

Surprisingly, it has been found that when using the above-mentioned additional elements of their compounds in the lead substitute material, a disproportionate increase in the protective effect occurs, preferably when their weight fraction of the lead substitute material is between 20% and 40%.

In a further preferred embodiment of the invention, the lead substitute material is characterized in that it additionally comprises up to 40% by weight of one or more of the following elements Ta, Hf, Lu, Yb, Tm, Th, U and / or their compounds.

In addition, in the lead substitute materials usable metals Er, Ho, Dy, Tb, Gd, Eu, Sm, Ta, Hf, Lu, Yb, Tm, Th, U can also metals and / or their compounds and / or Csl with a relatively low degree of purity are used, as they arise as waste products.

The lead substitute material according to the invention fulfills by the combination of the matrix material based on silicone and the selection of lead-substitute metals or their compounds in a surprising manner, the conditions of a high-shielding radiation protection material that is elastic and lightweight and to a great extent all environmental requirements, eg. B. biocompatibility, recyclability, low emissions.

The lead substitute material of the present invention may further contain fillers for reinforcement and additives in conventional amounts. The fillers include, for example, fibers or fibrous materials of cotton fibers, synthetic fibers, fiberglass fibers and aramid fibers.

Possible reinforcing fillers include fumed silica, precipitated silicas, iron oxide, titanium oxide, aluminum trihydrate and carbon black.

Thus, the lead substitute material of the invention may also contain processing aids that further enhance the properties of the material. These include, for example, typical plasticizers.

In DIN EN 61331-3 a deviation from the nominal lead equivalent value downwards is not permitted. Only the German version of the standard allows one exception, namely a deviation of 10% from the nominal lead equivalent. For these reasons, it is desirable to have as flat a lead as possible over the energy of a lead substitute material.

A fall in the lead equivalent below the nominal lead equivalent or below the lower tolerance limit means that the radiation protection material can not be used at the relevant tube voltages, since the shielding effect is too low. In this case, alternatively, the basis weight of the lead substitute material must be increased to the extent that the permissible tolerances of DIN EN 61331-3 are met. However, an increase in basis weight is considered disadvantageous.

Another possibility is to limit the scope of application in terms of energy or tube voltage.

It was therefore a further object of the present invention to select elements or their compounds in such a way that the lowest possible drop in the lead equivalent in the desired energy utilization range takes place, taking into account the accessibility of the respective elements or their compounds.

The relative effectiveness N _rel as an increase in the lead equivalent (PbGW) based on a standardized mass coverage of 0.1 kg / m ² was determined in a series of materials in test series and summarized in Table 2 below. It reproduces the weakening properties of the individual elements even more clearly than the mass attenuation coefficients described above, since here the absorption is included in the immediate area of the respective absorption edges. Table 2 material N _rel
Average increase PbGW based on 0.1 kg / m ² (relative Pb) Increase PbGW from 60 to 80 kV
based on 0.1 kg / m ² group 60-90 kV 60-125 kV 100-125 kV 125-150 kV sn 1.64 1.30 0.96 0.80 -0,005 A Bi 1.41 1.27 1.13 1.17 -0,005 A W 0.91 1.07 1.25 1.07 + -0.000 A Gd 1.85 2.05 2.27 1.56 +0.007 B He 1.20 1.45 1.70 1.36 +0.009 B

Surprisingly, it was found that the elements or their compounds can be classified as follows: Group A: Relatively less effective materials with values of N _rel <1.2 - 1-6 mm PbGW per 0.1 kg / m ² and a small or negative increase of 60-80 kV. These elements or their compounds include Sn, Bi and W. Group B: Relatively high efficiency materials with N _rel ≥ 1.3 mm PbGW per 0.1 kg / m ² and a high rise of 60-80 kV.

In a particularly preferred embodiment of the invention, therefore, the energy range 60-140 kV is divided into a plurality of partially overlapping regions in accordance with the most common applications of X-ray radiation:

1. Energy range 60-90 kV

In this field of energy predominantly dental applications of the single-shot technique and the panoramic layer technique take place.

2. Energy range 60-125 kV

This area of energy includes the most common X-ray and X-ray interventions, such as angiography, computed tomography, cardiac catheter examinations, interventional radiology, thorax hard-beam technique.

3. Energy range 100-125 kV

Most computer tomographs fall into this energy range.

4. Energy range 125-150 kV

This is an energy range for specific applications such as special computed tomography, bone density measurements, special thorax hard-jet technology and nuclear medicine diagnostics.

Lead-free protective clothing that can only be used in a certain energy range must be marked accordingly by the manufacturer.

In the relatively narrow energy range, it was shown from Table 2 that of the group A elements Sn is the most effective. From Group B Gd is preferred, but Csl also resulted in a lead substitute with very good properties.

• Aus der Tabelle 2 können beispielsweise Elemente mit geringem und hohem Anstieg des Bleigleichwerts in vorteilhafter Weise in der Weise ausgewählt werden, dass die Verläufe des Bleigleichwerts über den gesamten Bereich möglichst flach bleiben. Eine gewisse Überhöhung bei 80 und 100 kV ist dabei physikalisch nicht zu umgehen.

Energy range 60-125 kV (general X-ray range):

• From Table 2, for example, elements with low and high rise of the lead equivalent can be advantageously selected in such a way that the waveforms of the lead equivalent remain as flat as possible over the entire range. A certain elevation at 80 and 100 kV is physically impossible to avoid.

Thus, one or more elements or their compounds of group A can be optimally combined with one or more elements or their compounds of group B, the choice being made according to the efficiency of the shielding, the accessibility of the respective element or its compound and As constant as possible of the lead equivalent takes place.

Here, a dependence of the proportion of the A elements or their compounds of those of the B elements or given their connections. Thus, when increasing the content of a B-element, the relative weight fraction of an A-element with opposite energy behavior must also be significantly increased in order to keep the course of the lead equivalent above the energy as flat as possible.

For example, if more than 20% by weight of B-elements or their compounds, the proportion of Sn or Bi should exceed 40% by weight to ensure low energy dependence.

• Das ist der Energiebereich für die meisten neueren Computer-Tomographen.

Energy range 100-140 kV:

• This is the energy range for most recent computer tomographs.

High protective effects or low basis weights can be achieved by using the elements or their compounds, which have their highest shielding effect especially in this small energy range. For reasons of accessibility, a greater proportion of the elements or their group A compounds should be combined with a smaller proportion of the elements or their group B compounds, in which case a flat energy balance of the lead equivalent will not be so important because of the relatively small energy window is.

Energy range 125-150 kV:

This area concerns special applications in radiology and nuclear medicine. The weight per unit area of the radiation protection clothing is not in the foreground of the optimization in this area since the protective clothing is generally worn here only for a short time or fixed radiation protection screens are used.

The selection of the elements or their connections is done according to the above criteria. Very good results provide Gd and Er in combination with Bi. The effect of W is too low in this area.

In summary, it can thus be stated that the composition of protective substances for individual energy ranges can be expediently optimized by splitting according to the most frequently occurring X-ray applications.

In a further preferred embodiment of the invention, the lead substitute material has a structure of at least two separate or interconnected protective layers of different composition, wherein at least one layer at least 50% of the total weight of only one element from the group Sn, W and Bi or their Connections exists.

In a further preferred embodiment of the invention, the lead substitute material is characterized in that it comprises a construction of at least two separate or interconnected protective layers of different composition, wherein the protective layer (s) removed from the body predominantly the elements or their compounds with higher X-ray fluorescence yield and the body-near protective layer (s) comprising the elements or their compound with lower X-ray fluorescence yield.

In the irradiation of materials with X-rays, characteristic X-radiation is excited as fluorescence radiation. The fluorescence yield depends on the atomic number. This proportion of fluorescence leads to an additional radiation exposure of the skin and the organs immediately below it. From measurements on protective clothing it was determined that in particular elements with smaller atomic numbers, in the present case in particular Sn, fluoresce particularly strongly. In a layered structure of the radiation protection material can advantageously a Stratification by elements so that the elements lie with the lowest fluorescence yield on the skin side.

The fluorescence component, also referred to as build-up factor, is represented by commercially available lead-free protective materials (material B) in the following Table 3 in comparison with a material constructed in layers according to the principle described here (material A). As can be seen, the build-up factor can reach values up to 1.42. That is, the skin is burdened in this case by the fluorescent component by 42% more. Table 3 kV Material A Material B 80 1.15 1.42 90 1.14 1.35 100 1.14 1.32 110 1.16 1.36

In a further particularly preferred embodiment of the invention, the lead substitute material is characterized in that it has a structure of protective layers of different composition.

The lead substitute material may comprise a construction of at least two separate or interconnected protective layers of different composition, with the body-removed protective layer (s) predominantly comprising the lower atomic number elements or their compounds and the proximal protective layer (s) comprise the elements of higher atomic number or their compounds.

The lead substitute material may also be characterized in that a weakly radioactive layer is embedded between two separate or nonradioactive protective layers connected to the radioactive layer.

It can be used as elements or their compounds of group B to shield high energy radiation and the actinides thorium or uranium, the latter z. B. as depleted uranium, are used. They have a high shielding effect in the energy range of 125-150 kV, but are themselves weakly radioactive.

The effect of self-radiation can be mitigated by embedding the radioactive layer between two non-active layers of Bi.

The proportion of self-exposure by thorium or uranium should be low in most cases and therefore negligible. There is a trade-off here, which contrasts the benefits of lead elimination and higher protection with low intrinsic exposure.

aufweisen, worin D₅₀ die 50er-Perzentile der Korngrößenverteilung, d die Schichtdicke in mm und p den Gewichtsanteil der jeweiligen Materialkomponente am Gesamtgewicht bedeuten und die 90er Perzentile der Korngrößenverteilung D₉₀ ≤ 2 • D₅₀ ist.In a further preferred embodiment of the invention, the lead substitute material is characterized in that the metals or metal compounds are grained and their grain sizes of a 50th percentile according to the following formula $${\mathrm{D}}_{\mathrm{50}}\mathrm{=}\frac{\mathrm{d}\mathrm{\cdot }\mathrm{p}}{\mathrm{10}}\mathrm{mm}$$

wherein D _{50 is} the 50th percentile of the particle size distribution, d is the layer thickness in mm and p is the weight fraction of the respective material component in the total weight and the 90th percentile of the particle size distribution D ₉₀ ≤ 2 • D ₅₀ .

In measurements of lead equivalents on protective layers, which consist of metal powders or powders of metal compounds, it was surprisingly found that the radiolucency of the grained Substances existing layer is higher compared to a film layer at the same mass occupancy. This mainly affects the lower energy range of 60-80 kV. At higher energies, the local permeability differences, ie the X-ray contrast, become increasingly smaller.

For example, with an Sn content of 30% = 0.3 and a layer thickness of 0.4 mm $${\mathrm{D}}_{50}=0.4\mathrm{mm}•0.3=0.012\mathrm{mm}=12\mu \mathrm{m}\mathrm{,}$$

In addition, the 90th percentile of the particle size distribution should not be greater than 2 • D ₅₀ = 24 μm.

Therefore, low weight materials must also have a small grain size, i. be very finely distributed to develop an optimal protective effect.

By taking advantage of this effect, the weight of a radiation protection clothing can be further reduced.

The lead substitute material according to the invention, after mixing the silicone matrix material and the metal / metal compounds in a conventional manner, after which a homogeneous mixture is obtained, further processed and cured, forming a dense, elastic material in a desired shape. Further processing techniques include, for example, extrusion, injection molding, calendering, compression molding or transfer molding. In a preferred embodiment, the lead substitute material according to the invention is provided as sheet material which is cut into the desired shape according to techniques known per se or the like.

The material according to the invention can be used, for example, for protective gloves, protective aprons, patient covers, gonad protection, ovarian protection, dental protective shields, stationary lower body protection, table tops, stationary or portable radiation protection walls or radiation curtains are applied advantageously.

Fig. 1:

ein Blei-Ersatzmaterial (Referenz) mit 22 Gew.-% Zinn, 27 Gew.-% Wolfram, 4 Gew.- % Erbium und 15 Gew.-% Silikon-Matrixmaterial,

Fig. 2:

das erfindungsgemäße Blei-Ersatzmaterial mit 20 Gew.-% Zinn, 36 Gew.-% Wolfram, 29 Gew.-% Wismut und 15 Gew.-% Silikon-Matrixmaterial und

Fig. 3:

die berechneten relativen Flächengewichte einer Schutzkleidung mit Nenn- Bleichgleichwerten von 0,5 mm gemäß den Beispielen 3, 4 und 6 im Vergleich zu einer Bleischürze mit 0,5 mm Bleigleichwert.

In the following, the invention will be explained in more detail by way of examples with reference to the drawing. In the drawing show:

Fig. 1:

a lead substitute (reference) containing 22 wt% tin, 27 wt% tungsten, 4 wt% erbium and 15 wt% silicone matrix material,

Fig. 2:

the lead replacement material according to the invention with 20 wt .-% tin, 36 wt .-% tungsten, 29 wt .-% bismuth and 15 wt .-% silicone matrix material and

3:

the calculated relative basis weights of protective clothing with nominal bleaching equivalents of 0.5 mm according to Examples 3, 4 and 6 compared to a lead apron with 0.5 mm lead equivalent.

Example 1 (reference)

The FIG. 1 shows a lead substitute with 22 wt% tin, 27 wt% tungsten, 4 wt% erbium, and 15 wt% silicone matrix material. This lead substitute is in the FIG. 1 denoted by 2. 1 denotes a commercially available material of the composition 65% by weight of antimony, 20% by weight of tungsten and 15% by weight of matrix material.

The FIG. 1 shows a weight comparison of lead substitutes for a nominal lead equivalent of 0.5 mm.

From the FIG. 1 It can be seen that the basis weight required to achieve a rated lead equivalent of 0.5 mm is between 100 and 140 kV in the case of the material increases only about 7%, while the increase in the comparison material is significantly greater.

Example 2

The FIG. 2 shows the lead replacement material according to the invention with 20 wt .-% tin, 36 wt .-% tungsten, 29 wt .-% bismuth and 15 wt .-% silicone matrix material. This lead substitute is in the FIG. 2 denoted by 2. 1 denotes a commercially available material of the composition 70% by weight of tin, 10% by weight of barium and 20% by weight of matrix material.

The FIG. 2 shows a weight comparison of lead substitutes for a nominal lead equivalent of 0.5 mm.

From the FIG. 2 It can be seen that the basis weight required to reach a nominal lead equivalent of 0.5 mm between 100 and 140 kV only increases by about 9% for the material according to the invention, while the increase in the comparison material is about 60%.

Example 3 (reference)

Lead-free, light radiation protection apron for the dental sector of 60-90 kV Pb nominal lead equivalent 0.5 mm.

A lead-free radiation protection apron was produced from 59% by weight Sn, 24% by weight Gd, 1% by weight W and 16% by weight silicone matrix material.

The radiation protection effect corresponded to that of a corresponding lead apron with a reduced basis weight of only 4.4 kg / m ² by about 35%.

Example 4 (reference)

Lead-free light radiation protection apron for the application range 60-125 kV.

A radiation protection apron was made from 50% by weight Sn, 11% by weight W, 23% by weight Gd and 16% by weight silicone matrix material.

In this case, for a nominal lead equivalent of 0.5 mm lead, a surface weight of 4.5 kg / m ^{2 was obtained} , for a nominal lead equivalent of 0.35 mm lead a surface weight of 3.3 kg / m ² and a nominal Lead equivalent of 0.25 mm lead a basis weight of 2.4 kg / m ² .

Example 5 (reference)

Lead-free lightweight radiation protection apron for the application range 60-125 kV.

A radiation protection apron of 40% by weight of Bi, 20% by weight of Sn, 24% by weight of Gd and 16% by weight of silicone matrix material was produced.

This resulted in a basis weight of 5.0 kg / m ² for a nominal lead equivalent of 0.5 mm lead.

Lead-free commercial radiation protection aprons have basis weights of 5.4 to 6.1 kg / m ² at nominal lead equivalent values of 0.50 mm. Conventional lead-rubber material has a basis weight of 6.75 kg / m ² .

Thus, the essential advantage of the present invention becomes apparent, according to which the protective clothing can be considerably easier. This is a very significant advantage especially for several hours of application of protective clothing.

In addition, if the user works with tube voltages of 80-100 kV, the lead equivalent value is approximately 20% higher than the nominal value of 0.5 mm Pb of a corresponding lead apron. This means an additional increased radiation protection.

Example 6 (reference)

Lead-free lightweight radiation protection apron for computer tomography.

A radiation protection apron of 40% by weight of Bi, 10% by weight of W, 34% by weight of Gd and 16% by weight of silicone matrix material was produced.

There was a surprisingly low basis weight for 0.5 mm nominal lead equivalent of only 4.6 kg / m ² .

Example 7 (Reference)

Lead-free lightweight apron for nuclear medicine applications.

A nuclear medicine apron was prepared from 50 wt% Bi, 25 wt% Gd, 9 wt% Er and 16 wt% silicone matrix material.

The basis weight was 4.8 kg / m ² for 0.5 nominal total lead equivalent.

Example 8

The FIG. 3 Figure 4 shows the calculated relative basis weights of protective clothing with nominal bleaching equivalences of 0.5 mm according to Examples 3, 4 and 6 compared to a lead apron with 0.5 mm lead equivalent. From the illustration it can be seen that the protective aprons for dental application, general X-ray and computer tomography (CT) each have the lowest basis weight in the envisaged energy ranges.

Claims (18)

1. Lead substitute material for radiation protection purposes in the energy range of an X-ray tube having a voltage of from 60 to 140 kV, wherein for nominal overall lead equivalents of from 0.25 to 2.00 mm, the lead substitute material comprises
   from 12 to 22 wt.% of a silicone-based material,
   from 1 to 39 wt.% Sn or Sn compounds,
   from 16 to 60 wt.% W or W compounds, and
   from 16 to 60 wt.% Bi or Bi compounds.
2. Lead substitute material for radiation protection purposes in the energy range of an X-ray tube having a voltage of from 60 to 140 kV, wherein for nominal overall lead equivalents of from 0.25 to 2.00 mm, the lead substitute material comprises
   from 12 to 22 wt.% of a silicone-based material,
   from 40 to 60 wt.% Sn or Sn compounds,
   from 7 to 15 wt.% W or W compounds, and
   from 7 to 15 wt.% Bi or Bi compounds.
3. Lead substitute material according to any one of claims 1 or 2,
   characterized in that
   the lead substitute material additionally comprises up to 40 wt.% of one or more of the following elements Er, Ho, Dy, Tb, Gd, Eu, Sm and/or their compounds and/or CsI.
4. Lead substitute material according to claim 3,
   characterized in that
   the lead substitute material additionally comprises up to 20 wt.% of the elements and/or their compounds and/or CsI.
5. Lead substitute material according to claim 4,
   characterized in that
   the lead substitute material additionally comprises up to 8 wt.% of the elements and/or their compounds and/or CsI.
6. Lead substitute material according to any one of claims 1 to 5,
   characterized in that
   the lead substitute material additionally comprises up to 40 wt.% of one or more of the following elements Ta, Hf, Lu, Yb, Tm, Th, U and/or their compounds.
7. Lead substitute material according to claim 6,
   charcterized in that
   the lead substitute material additionally comprises up to 20 wt.% of the elements and/or their compounds.
8. Lead substitute material according to claim 7,
   characterized in that
   the lead substitute material additionally comprises up to 8 wt.% of the elements and/or their compounds.
9. Lead substitute material according to any one of claims 1 to 8,
   characterized in that
   the silicone-based material comprises silicone rubber.
10. Lead substitute material according to claim 9,
    characterized in that
    the silicone rubber comprises dimethyl silicone rubber, phenylmethyl silicone rubber, phenyl silicone rubber and polyvinyl silicone rubber.
11. Lead substitute material according to any one of claims 1 to 10,
    characterized in that
    it comprises fillers and processing aids.
12. Lead substitute material according to any of claims 1 to 11,
    characterized in that
    it comprises a structure of protective layers of different compositions.
13. Lead substitute material according to claim 12,
    characterized in that
    it comprises a structure of at least two protective layers of different compositions which are separate or joined together, wherein the protective layer(s) more remote from the body comprise(s) predominantly the elements having a lower atomic number, or their compounds, and the protective layer(s) close to the body comprise(s) predominantly the elements having a higher atomic number, or their compounds.
14. Lead substitute material according to claims 12 or 13,
    characterized in that
    it comprises a structure of at least two protective layers of different compositions which are separate or joined together, wherein at least in one layer at least 50% of the total weight consists of only one element from the group Sn, W and Bi or their compounds.
15. Lead substitute material according to claim 13,
    characterized in that
    it comprises a structure of at least two protective layers of different compositions which are separate or joined together, wherein the protective layer(s) more remote from the body comprise(s) predominantly the elements or their compounds having a higher X-ray fluorescent yield, and the protective layer(s) close to the body comprise(s) the elements or their compounds having a lower X-ray fluorescent yield.
16. Lead substitute material according to any one of claims 13 to 15,
    characterized in that
    a weakly radioactive layer is embedded between two non-radioactive protective layers which are separate from or joined to the radioactive layer.
17. Lead substitute material according to any one of claims 1 to 16,
    characterized in that
    the metals or metal compounds are granular and their particle sizes exhibit a 50^th percentile according to the following formula $${\mathrm{D}}_{\mathrm{50}}\mathrm{=}\frac{\mathrm{d}\mathrm{\cdot }\mathrm{p}}{\mathrm{10}}\mathrm{mm}$$

    

    
    wherein

    D₅₀ represents the 50^th percentile of the particle size distribution,

    d represents the layer thickness in mm, and

    p represents the proportion by weight of the particular material component in the total weight,

    and the 90^th percentile of the particle size distribution is D₉₀ ≤ 2 · D₅₀.
18. Radiation protection clothing of lead substitute material according to any one of claims 1 to 17.

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