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a The limit values apply regardless of the exposed surface for a mean dose on every surface of 1 cm2.

b The effective dose for persons with radiation exposure in Cat. A may amount to up to 50 mSv in one single calendar year if the total dose of 100 mSv is not exceeded in the 5 successive calendar years.

According to § 23 Para. 1 No. 1 of the X-ray Ordinance, X-rays may »only be used directly on people in medical or dental healing if a person has made a justifying indication according to § 24 Para. 1 No. 1 or 2«.

Furthermore, when a justifying indication has been made, X-rays may always only be used on people under the responsibility of doctors who possess specialised knowledge in radiation protection, i.e. have acquired specialist know-how in radiation protection and can verify corresponding training (»justified persons« according to § 24 of the X-ray Ordinance). Here it must be noted that doctors are not considered to be specialists in accordance with radiation protection just on the basis of completing their medical training. The acquisition of the specialist knowledge and radiation protection know-how is stipulated as an implementing regulation to the X-ray Ordinance in the above mentioned specialist ordinance in the version dated 1991 [1] (This ordinance will probably come into effect in an updated version during 2005 on the basis of the amended X-ray Ordinance dated 2002). According to the currently valid ordinance dated 1991, specialist knowledge in radiation protection consists of the »technical knowledge« and successful attendance of »courses in radiation protection«. The technical knowledge »contains theoretical knowledge and practical experience in using X-ray radiation in the specific area of application«. The courses in radiation protection »convey a knowledge of the laws, other theory and practical exercises in radiation protection in the specific area of application«.

Technical knowledge »includes the practical implementation and assessment of X-ray examinations under the special aspects of radiation protection.« For surgeons at the moment as a rule, a minimum 12-month period is required for acquiring the technical knowledge in the area of »emergency diagnosis (extremities, skull, vertebral column, thorax, abdomen)«.

To this end, the specialist knowledge ordinance explains among others:

4 Emergency diagnosis: simple X-ray diagnosis as part of initial care and emergency treatment and 4 Emergency diagnosis of the abdomen: digestive, urinary and biliary tracts, reproductive organs.

If the technical knowledge has been verified in the corresponding application area with successful attendance of radiation protection courses - when using surgical image intensifiers after an initial 8-h »Instruction ... in radiation protection...«, a »basic course in radiation protection« and a »special course in X-ray diagnosis«, the responsible state Medical Council issues a corresponding specialist certificate. This specialist certificate is a prerequisite for the operation of surgical imaging intensifiers under their own responsibility by surgeons working in general practice.

A doctor without specialist knowledge in radiation protection, even a surgeon, may only use X-rays according to the X-ray Ordinance if he has the necessary »know-how in radiation protection« according to § 24 of the X-ray Ordinance and works »under constant supervision and responsibility« of a doctor »with specialist knowledge in radiation protection«. Know-how in radiation protection refers to an applied method of X-ray examination and the corresponding necessary radiation protection rules and is conveyed according to the specialist knowledge ordinance of 1991 as »instruction for doctors about radiation protection in diagnosis with X-ray radiation« in the 8-h special courses mentioned above.

For the use of surgical image intensifiers, it is stipulated that also those persons working as assistants only in the operating suite and using or switching on X-ray equipment under the direct instruction of the immediately present specialist doctor (technical execution) must have know-how in radiation protection. According to the above mentioned specialist knowledge ordinance, the necessary know-how in radiation protection is acquired in special courses which currently last 24 h.

With regard to transitional rulings, the amended X-ray Ordinance prescribes that specialist knowledge and know-how in radiation protection must be updated for the corresponding group of people at least every 5 years by attending corresponding radiation protection courses or other acknowledged training courses.

4.1.2.3 Radiation protection manager, radiation protection officer

The radiation protection manager requires a permit or notification according to the X-ray Ordinance (owner). Where necessary for safe operation, the radiation protection manager shall appoint in writing the required number of radiation protection officers to run or supervise the facility. The radiation protection manager is still responsible for compliance with the protection regulations even after he has appointed radiation protection officers (7 § 13 Para. 2 of the X-ray Ordinance).

In a university clinic or hospital with several independent departments with X-ray equipment, as a rule, the radiation protection manager (e.g. dean of the university or administrator of the city or district hospital) appoints the senior physician or medical director in writing as the radiation protection officer. »Required number of radiation protection officers to run or supervise the facility« means that a deputy must be appointed also in the event of the absence of a radiation protection officer while on holiday or incapacitated. A radiation protection officer must also be appointed to cover the eventuality that the use of X-ray radiation is planned on days being worked in several shifts, during night shifts, at the weekends or on public bank holidays.

D Fig. 4.4. Important dose definitions in radiation protection

Energy dose indicates the energy transferred to the tissue by radiation multiplied by the radiation weighting factor

Equivalent dose weights the energy dose in consideration of the biological effectiveness of the radiation types multiplied by the tissue weighting factor

Effective dose weights the equivalent dose in consideration of the susceptibility of the organs and tissues to radiation

The basic rule applies that medical staff in the possession of only »know-how in radiation protection« is only allowed to work in the application of radiation »under the constant supervision and responsibility« of a specialist doctor. This rule has meanwhile been interpreted by the responsible authorities in such a way that following a j us-tifying indication (in other words, »order for radiation application«) by a doctor with »specialist knowledge in radiation protection«, this doctor (or another specialist doctor) does not necessarily have to be personally present during the radiation application; however, he must be capable of arriving (back) in the place where radiation is being used within 15 min.

4.1.2.4 Obligations when operating an X-ray machine

Instruction of the staff. Given the special use of radiation with surgical image intensifiers in the operating theatre and the necessary presence of the doctors and assistants while using the radiation within the control area, the »instruction« in the correct handling of this equipment required in § 18 Para. 1 No. 1 of the X-ray Ordinance is of very special significance. This instruction, which must be arranged by the owner on the basis of an operating manual in the German language provided by expert staff of the machine manufacturer or supplier, is only required »at initial commissioning«, but should be repeated at appropriate intervals by the radiation protection officer in view of the special potential for danger involved in using the equipment, together with the frequently high fluctuation rate among staff in surgical departments. Records must be kept about holding such instruction sessions for the staff.

Radiation protection areas - control area. According to the X-ray Ordinance (§ 19), areas where persons can re ceive a higher effective dose than 6 mSv per calendar year (Sv, Sievert: dose unit for the effective equivalent dose) are to be marked off and identified as control areas. Given standard use of surgical image intensifiers, the control area depends not only on the radiation exposure times but also on the size of the maximum possible effective radiation field; in standard applications it ends between 2.5 m and 3.5 m from the region of the patient's body where the radiation was used. When using surgical image intensifiers for long procedures with long radiation exposure times, under certain circumstances the whole operating theatre is to be declared as control area. The control area identification must be clearly visible, containing at least the words »No entry - X-rays«. It can also be affixed to the (mobile) image intensifier in a clearly visible form stating the stipulated distance. But given the meanwhile wide range of applications of surgical image intensifiers, it is advisable to consider the whole operating theatre as control area in each case, and to apply the protection regulations of the X-ray Ordinance to all persons present there.

Monitoring areas. Monitoring areas are areas not belonging to the control area where persons can receive an annual effective dose higher than 1 mSv. These areas are to be set up as monitoring areas and given a permitted presence time of 40 h/week and 50 weeks/ calendar year, as in the control areas, unless other details apply to the actual presence time (§ 19 of the X-ray Ordinance).

The »effective dose« stated in § 2 No. 6 Letter b of the X-ray Ordinance is a dimension for the total damage or total risk from stochastic radiation effects which can occur with the comparatively low radiation exposure of persons with occupational radiation exposure in X-ray diagnosis. The effective dose is the sum of the weighted mean equivalent doses in the individual organs and tissues,

D Fig. 4.5. Official personal dosimeter (film badge)

which are possibly exposed to differing amounts of radiation (O Fig. 4.4). The unit of measurement for the effective dose is the sievert (Sv). The effective dose allows for a better comparison of the risks with regard to cancer or genetic damage for whole body exposure or exposure of just individual parts of the body. Stochastic radiation effects are random biological effects whose probability increases with radiation exposure, but for which no limit dose is presumed. As far as the stochastic effects are concerned, it is presumed that these are mono-cellular processes, i.e. the malignant transformation of one single cell is sufficient to trigger this kind of effect. It is only with considerably higher radiation exposure, such as that used for example in radiotherapy, that random (stochastic) effects reliably no longer occur; the effects here are deterministic (non-stochastic) radiation effects where the severity increases with increasing radiation exposure according to the number of damaged cells; here a limit dose is presumed. These effects come about as a result of multi-cellular processes, i.e. many cells have to be damaged before these effects are manifested. These radiation effects include all acute radiation effects, e.g. cataract or fibrotic processes in various tissues.

4.1.2.5 Occupational exposure to radiation, personal dosimetry

When surgical image intensifiers are being used in the operating theatre, the medical and nursing staff can receive a body dose as effective dose or part body dose of more than 1 mSv/a in certain organs. This group of persons is thus considered as having »occupational exposure to radiation«, and their radiation exposure, i.e. their body dose, must be monitored by measuring the personal dose. So-called personal dosimeters (film badges) are used for this purpose; they are usually replaced once a month and evaluated by the authority responsible according to state law (O Fig. 4.5).

The result of this evaluation is the amount of the received body dose. The radiation protection manager, radiation protection officer or person supervised by them can stipulate the use of a second dosimeter in addition to the official dosimeter, which can be read off at any time, e.g. a rod dosimeter (D Fig. 4.6).

The details of the type and scope of personal dosimetry for occupational exposure to radiation are stipulated in the amended »Guideline for physical radiation protection control for ascertaining body doses« dated 8 December 2003 [9]. Given the significance of occupational exposure to radiation when »using X-rays in the operating theatre«, D Figure 4.7 shows the suggestions made by these guidelines for personal dosimetry in the operating theatre and in interventional radiology.

The intensity of radiation used in the operating theatre is very unevenly distributed. In the case of unhindered, free dissipation, radiation from a punctiform origin will decrease in intensity according to the distance square law. Although these perquisites usually do not apply when using radiation in the operating theatre, enlarging the distance to the patient volume being exposed to radiation always considerably reduces the

Ocular lens

Clip

Scale

Ocular lens

Clip

Scale

Objective

Ionisation chamber Quartz fibre electrometer

Capacitor

Bellows valve Loading pin Safety cap

Fig. 4.6. Rod dosimeter which can be read off at any time

Objective

Ionisation chamber Quartz fibre electrometer

Capacitor

Bellows valve Loading pin Safety cap

Fig. 4.6. Rod dosimeter which can be read off at any time

GUIDELINE for physical radiation protection control ... o Fig. 4.7. Suggestions for personal dosimetry

Part 1 ¡Ascertaining the body dose for external radiation exposure (...;§ 35 X-ray Ordinance) dated 08.12.2003 Part B:Suggestions for... »Personal dosimetry«,X-RAY DIAGNOSIS

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