1991, The British Journal of Radiology, 64, 567-568
VOLUME 64 NUMBER 763
JULY 1991
The British Journal of Radiology Editorial The Guidance Notes revisited: advice to patients leaving hospital after diagnostic nuclear medicine Recently the Radiation Protection Committee of the activity will, in every case, diminish by dint of physical British Institute of Radiology conducted an informal decay and biological elimination. Nevertheless the survey of the practices adopted concerned with the concept of a "controlled" (or a "supervised") area method and level of information given to patients around the patient is useful when considering the potenleaving hospital after administration of a radio- tial effects on hospital workers, e.g. technicians, nurses, pharmaceutical for diagnostic purposes only. There is a porters, who may come into contact with such patients wide variation in practice, which does not always follow on a regular basis. For these workers the fact that the the advice of the "Guidance Notes for the Protection of radioactivity in any one patient may be short-lived is Persons against Ionising Radiation Arising from irrelevant because there may be a constant supply of Medical and Dental Use" (National Radiological patients each with "fresh" radioactivity. Protection Board, 1988). It seems appropriate to When the patient leaves hospital and goes home or examine the logic of the relevant regulations and the back to his own workplace then the situation is comderived guidance with regard to the non-conformity of pletely different, because the radioactive substance standards practised. brought into the home or workplace constitutes a single Schedule 6 of the Ionising Radiations Regulations event which is unlikely to be repeated. The question of 1985 (HMSO, 1985) requires an employer to designate significance to members of the patient's family or to as "controlled" an area in which the dose rate is likely to colleagues at work is not "what annual dose would I exceed 7.5 /iSv/h. This value of dose rate was originally receive if I were constantly exposed to radioactivity at obtained by dividing 15 mSv by 2000 h. A dose equiva- this level?" but rather "what dose will I receive from this lent of 15mSv is three-tenths of the relevant annual event?". The worst possible situation representing the dose limit for workers, and the figure of 2000 (being highest conceivable absorbed dose that any other 40 x 50) is an upper estimate of the number of hours in a person might receive (the "third party dose") is the dose working year. A worker must be "classified" if he is absorbed by a frequently cuddled child of the patient. likely to receive more than three-tenths of a relevant This dose can be calculated on the basis of a suitably dose limit. The definition of "controlled area" is based conservative biokinetic model (even recognizing physion the concept of ensuring that a non-classified worker cal decay alone) without resorting to the absurdity of who is constantly exposed for the whole of the working postulating a constant exposure rate throughout the year does not receive more than three-tenths of the year. Such calculations have been made (Mountford, annual dose limit. 1987) and have shown that the total absorbed dose The same schedule provides for an equivalent defini- equivalent to cuddled infants following disgnostic radiotion of a "controlled area" in terms of the local quantity nuclide administration to the mother does not approach of a y emitting radioactive substance: an area must be 1 mSv for any diagnostic technique with the single controlled if the product of activity and total y energy exception of "'In-labelled leucocytes. The highest such per disintegration ("the product") exceeds dose from other diagnostic techniques has been esti50 MBq MeV. A relaxation of this figure is given for mated as 240 /*Sv. situations where the radioactivity is distributed in the The National Radiological Protection Board (1986) human body; the product must not exceed has recommended an annual dose limit for members of 150 MBq MeV. In both cases these values of the the public of 1 mSv. There is a suggestion that this product correspond to an exposure rate at 1 m from the should be lowered, but if it is more than halved then the source which would just give a worker three-tenths of figure will be well within the range of changes in natural the dose limit if the same exposure rate were maintained background radiation (currently estimated as an constantly during a 2000 h working year. average of 2.4 mSv annually in the UK). It is clear that The Regulations also define a "supervised area" as no nuclear medicine diagnostic technique can give rise one in which the dose rate might be more than one-third to a third party dose which could exceed an annual dose of the level which would require it to be "controlled". limit for members of the public or, indeed, which could Patients who have received doses of radioactive be greater than one-tenth of the average annual natural substances may constitute a source of y radiation during background radiation in the UK. the time that they retain radioactivity. The quantity of The UK Guidance Notes, published in 1986, provide Vol. 64, No. 763
567
R. A. Shields
general guidance to medical and dental workers on "good practice", consistent with regulatory requirements. However, the guidance given in Chapter 12 ("Patients leaving hospital after administration of radioactive substances") is based on an unnecessarily rigid premise. The authors had to determine what levels of radioactivity in patients might give rise to "significant" exposure to third parties. (This requirement is identified in paragraph 33 of part 2 of the Approved Code of Practice (Health and Safety Commission, 1985)). In determining what levels might lead to significant exposures, the authors have used critical values of "the product", thus extending the concept of "controlled" and "supervised" areas outside the workplace. They have apparently failed to note that this concept is based upon the need to ensure that a worker who is constantly exposed for the whole working year does not exceed his annual dose limit. It is wholly inappropriate to the consideration of third party doses from nuclear medicine patients. Such doses can and have been estimated as the consequence of individual events and can be shown (see above) to be quite "insignificant" for almost all diagnostic nuclear medicine. The Guidance Notes advise that instructions should be given to certain patients on reducing close contact with other persons, and especially on "avoiding unnecessary contact with children". We consider this advice to be inappropriate and unhelpful to patients who have received diagnostic quantities of radionuclide. Patients who come to hospital for tests are often anxious and one aspect of our care for them must be to help them to keep the problems in perspective. The maximum conceivable dose to a cuddled infant will be of the same order as variations in annual natural background and the reduction in the child's annual dose achieved by avoiding "non-essential contact" with his mother will be even less than these insignificant amounts. The advice to "avoid non-essential contact" may well raise levels of anxiety further and would, therefore, be "unreasonable" in the context of ALARA or ALARP. By the same token, doses to people other than the patient's children will be even smaller, and the advice recommended in the Guidance Notes will be even less reasonable. The Guidance Notes draw attention to the possibility that radioactive excreta might cause contamination problems, but state "Normal sanitary arrangements should suffice. The use of bed pans should be avoided if possible". Such advice may be considered gratuitous. It is unfortunate that the justifiable concern over potential hazards following large therapeutic administrations should here be confused with the negligible hazards associated with diagnostic procedures. The Guidance Notes also recommend advice to a patient to notify his employer if his work might be affected by radiation. This is no doubt well meant, but is not required by any regulation. The patient's work may be considered in two categories: (a) work with materials (e.g. photographic film) which happen to be radiosensitive, and (b) work involving radiation (e.g. in assays or dosimetry). In the first category it is extremely 568
unlikely that the patient could have any significant effect on the materials (remembering that the calculated maximum dose to a cuddled infant is of the order of geographic changes in natural background). In the second category the employer will already have taken precautions against fluctuations in background, will already have appropriate local rules and should have instructed his employees in appropriate precautions. These instructions should, if appropriate, include the exercise of care following nuclear medicine, and are obviously best determined by the employer. Sensitive radiation-detection alarms can be triggered by workers who have undergone nuclear medicine examinations; this must be understood by those using the radiation detectors but it does not constitute a hazard. We conclude that patients leaving hospital after receiving diagnostic nuclear medicine administrations do not generally present any external radiation hazard to other persons, and that no special instructions are necessary. The single known exception is that of 11 'In-labelled leucocytes, when special advice may be necessary for mothers of babies (and the dose administered to such mothers should be restricted to less than lOMBqof m In). The foregoing does not, of course, apply to the potential internal radiation hazard associated with breastfeeding, and special advice may be necessary for nursing mothers (Mountford & Coakley, 1986, 1989). Such advice will be based upon whether the estimated dose to the infant is likely to exceed 1 mSv. Similarly the foregoing does not apply to therapeutic administrations. It should be noted, in particular, that a potential hazard might exist for other persons following the administration to a patient of more than 30 MBq of 131I. Appropriate instructions should then be given. R. A. SHIELDS
for the Radiation Protection Committee of the BIR References
HEALTH AND SAFETY COMMMISSION, 1985. Approved Code Practice. The Protection of Persons against Ionising Radiation arising from any Work Activity (HMSO, 1985). HMSO, 1985. The Ionising Radiations Regulations 1985 (Statutory Instrument 1985 No. 1333) (HMSO, London). MOUNTFORD, P. J., 1987. Estimation of close contact doses to young infants from surface dose rate on radioactive adults. Nuclear Medicine Communications, 8, 857-863. MOUNTFORD, P. J. & COAKLEY, A J., 1986. Guidelines for
breast-feeding following maternal radiopharmaceutical administration. Nuclear Medicine Communications, 7, 399-401 (Editorial). 1989. A review of the secretion of radioactivity in human and breast milk: data, quantitative analysis recommendations. Nuclear Medicine Communications, 10, 15-27. NATIONAL
RADIOLOGICAL
PROTECTION
BOARD,
1986. Dose
Limits for Members of the Public (NRPB-GS4) (HMSO, 1986). 1988. Guidance Notes for the Protection of Persons against Ionising Radiations arising from Medical and Dental Use (HMSO, London).
The British Journal of Radiology, July 1991
of
VOLUME 64 NUMBER 763
JULY 1991
The British Journal of Radiology Editorial The Guidance Notes revisited: advice to patients leaving hospital after diagnostic nuclear medicine Recently the Radiation Protection Committee of the activity will, in every case, diminish by dint of physical British Institute of Radiology conducted an informal decay and biological elimination. Nevertheless the survey of the practices adopted concerned with the concept of a "controlled" (or a "supervised") area method and level of information given to patients around the patient is useful when considering the potenleaving hospital after administration of a radio- tial effects on hospital workers, e.g. technicians, nurses, pharmaceutical for diagnostic purposes only. There is a porters, who may come into contact with such patients wide variation in practice, which does not always follow on a regular basis. For these workers the fact that the the advice of the "Guidance Notes for the Protection of radioactivity in any one patient may be short-lived is Persons against Ionising Radiation Arising from irrelevant because there may be a constant supply of Medical and Dental Use" (National Radiological patients each with "fresh" radioactivity. Protection Board, 1988). It seems appropriate to When the patient leaves hospital and goes home or examine the logic of the relevant regulations and the back to his own workplace then the situation is comderived guidance with regard to the non-conformity of pletely different, because the radioactive substance standards practised. brought into the home or workplace constitutes a single Schedule 6 of the Ionising Radiations Regulations event which is unlikely to be repeated. The question of 1985 (HMSO, 1985) requires an employer to designate significance to members of the patient's family or to as "controlled" an area in which the dose rate is likely to colleagues at work is not "what annual dose would I exceed 7.5 /iSv/h. This value of dose rate was originally receive if I were constantly exposed to radioactivity at obtained by dividing 15 mSv by 2000 h. A dose equiva- this level?" but rather "what dose will I receive from this lent of 15mSv is three-tenths of the relevant annual event?". The worst possible situation representing the dose limit for workers, and the figure of 2000 (being highest conceivable absorbed dose that any other 40 x 50) is an upper estimate of the number of hours in a person might receive (the "third party dose") is the dose working year. A worker must be "classified" if he is absorbed by a frequently cuddled child of the patient. likely to receive more than three-tenths of a relevant This dose can be calculated on the basis of a suitably dose limit. The definition of "controlled area" is based conservative biokinetic model (even recognizing physion the concept of ensuring that a non-classified worker cal decay alone) without resorting to the absurdity of who is constantly exposed for the whole of the working postulating a constant exposure rate throughout the year does not receive more than three-tenths of the year. Such calculations have been made (Mountford, annual dose limit. 1987) and have shown that the total absorbed dose The same schedule provides for an equivalent defini- equivalent to cuddled infants following disgnostic radiotion of a "controlled area" in terms of the local quantity nuclide administration to the mother does not approach of a y emitting radioactive substance: an area must be 1 mSv for any diagnostic technique with the single controlled if the product of activity and total y energy exception of "'In-labelled leucocytes. The highest such per disintegration ("the product") exceeds dose from other diagnostic techniques has been esti50 MBq MeV. A relaxation of this figure is given for mated as 240 /*Sv. situations where the radioactivity is distributed in the The National Radiological Protection Board (1986) human body; the product must not exceed has recommended an annual dose limit for members of 150 MBq MeV. In both cases these values of the the public of 1 mSv. There is a suggestion that this product correspond to an exposure rate at 1 m from the should be lowered, but if it is more than halved then the source which would just give a worker three-tenths of figure will be well within the range of changes in natural the dose limit if the same exposure rate were maintained background radiation (currently estimated as an constantly during a 2000 h working year. average of 2.4 mSv annually in the UK). It is clear that The Regulations also define a "supervised area" as no nuclear medicine diagnostic technique can give rise one in which the dose rate might be more than one-third to a third party dose which could exceed an annual dose of the level which would require it to be "controlled". limit for members of the public or, indeed, which could Patients who have received doses of radioactive be greater than one-tenth of the average annual natural substances may constitute a source of y radiation during background radiation in the UK. the time that they retain radioactivity. The quantity of The UK Guidance Notes, published in 1986, provide Vol. 64, No. 763
567
R. A. Shields
general guidance to medical and dental workers on "good practice", consistent with regulatory requirements. However, the guidance given in Chapter 12 ("Patients leaving hospital after administration of radioactive substances") is based on an unnecessarily rigid premise. The authors had to determine what levels of radioactivity in patients might give rise to "significant" exposure to third parties. (This requirement is identified in paragraph 33 of part 2 of the Approved Code of Practice (Health and Safety Commission, 1985)). In determining what levels might lead to significant exposures, the authors have used critical values of "the product", thus extending the concept of "controlled" and "supervised" areas outside the workplace. They have apparently failed to note that this concept is based upon the need to ensure that a worker who is constantly exposed for the whole working year does not exceed his annual dose limit. It is wholly inappropriate to the consideration of third party doses from nuclear medicine patients. Such doses can and have been estimated as the consequence of individual events and can be shown (see above) to be quite "insignificant" for almost all diagnostic nuclear medicine. The Guidance Notes advise that instructions should be given to certain patients on reducing close contact with other persons, and especially on "avoiding unnecessary contact with children". We consider this advice to be inappropriate and unhelpful to patients who have received diagnostic quantities of radionuclide. Patients who come to hospital for tests are often anxious and one aspect of our care for them must be to help them to keep the problems in perspective. The maximum conceivable dose to a cuddled infant will be of the same order as variations in annual natural background and the reduction in the child's annual dose achieved by avoiding "non-essential contact" with his mother will be even less than these insignificant amounts. The advice to "avoid non-essential contact" may well raise levels of anxiety further and would, therefore, be "unreasonable" in the context of ALARA or ALARP. By the same token, doses to people other than the patient's children will be even smaller, and the advice recommended in the Guidance Notes will be even less reasonable. The Guidance Notes draw attention to the possibility that radioactive excreta might cause contamination problems, but state "Normal sanitary arrangements should suffice. The use of bed pans should be avoided if possible". Such advice may be considered gratuitous. It is unfortunate that the justifiable concern over potential hazards following large therapeutic administrations should here be confused with the negligible hazards associated with diagnostic procedures. The Guidance Notes also recommend advice to a patient to notify his employer if his work might be affected by radiation. This is no doubt well meant, but is not required by any regulation. The patient's work may be considered in two categories: (a) work with materials (e.g. photographic film) which happen to be radiosensitive, and (b) work involving radiation (e.g. in assays or dosimetry). In the first category it is extremely 568
unlikely that the patient could have any significant effect on the materials (remembering that the calculated maximum dose to a cuddled infant is of the order of geographic changes in natural background). In the second category the employer will already have taken precautions against fluctuations in background, will already have appropriate local rules and should have instructed his employees in appropriate precautions. These instructions should, if appropriate, include the exercise of care following nuclear medicine, and are obviously best determined by the employer. Sensitive radiation-detection alarms can be triggered by workers who have undergone nuclear medicine examinations; this must be understood by those using the radiation detectors but it does not constitute a hazard. We conclude that patients leaving hospital after receiving diagnostic nuclear medicine administrations do not generally present any external radiation hazard to other persons, and that no special instructions are necessary. The single known exception is that of 11 'In-labelled leucocytes, when special advice may be necessary for mothers of babies (and the dose administered to such mothers should be restricted to less than lOMBqof m In). The foregoing does not, of course, apply to the potential internal radiation hazard associated with breastfeeding, and special advice may be necessary for nursing mothers (Mountford & Coakley, 1986, 1989). Such advice will be based upon whether the estimated dose to the infant is likely to exceed 1 mSv. Similarly the foregoing does not apply to therapeutic administrations. It should be noted, in particular, that a potential hazard might exist for other persons following the administration to a patient of more than 30 MBq of 131I. Appropriate instructions should then be given. R. A. SHIELDS
for the Radiation Protection Committee of the BIR References
HEALTH AND SAFETY COMMMISSION, 1985. Approved Code Practice. The Protection of Persons against Ionising Radiation arising from any Work Activity (HMSO, 1985). HMSO, 1985. The Ionising Radiations Regulations 1985 (Statutory Instrument 1985 No. 1333) (HMSO, London). MOUNTFORD, P. J., 1987. Estimation of close contact doses to young infants from surface dose rate on radioactive adults. Nuclear Medicine Communications, 8, 857-863. MOUNTFORD, P. J. & COAKLEY, A J., 1986. Guidelines for
breast-feeding following maternal radiopharmaceutical administration. Nuclear Medicine Communications, 7, 399-401 (Editorial). 1989. A review of the secretion of radioactivity in human and breast milk: data, quantitative analysis recommendations. Nuclear Medicine Communications, 10, 15-27. NATIONAL
RADIOLOGICAL
PROTECTION
BOARD,
1986. Dose
Limits for Members of the Public (NRPB-GS4) (HMSO, 1986). 1988. Guidance Notes for the Protection of Persons against Ionising Radiations arising from Medical and Dental Use (HMSO, London).
The British Journal of Radiology, July 1991
of
