低温核供热堆辐射防护安全准则

作者提出了低温核供热堆辐射防护安全准则的建议，即①要求半径５０ｋｍ范围内加权人口不超过１０６；②禁区半径为２５０ｍ；③限制发展区半径２ｋｍ；④低温核供热堆正常运行期间，由于放射性向环境释放所致公众个人剂量（全身或有效）不应超过０．１ｍＳｖ／ａ，集体剂量不超过１００ｍａｎ·Ｓｖ／ａ；⑤低温核供热堆事故期间，公众个人剂量不超过５ｍＳｖ，集体剂量不超过１０００ｍａｎ·Ｓｖ；⑥低温核供热堆正常运行期间，放射性流出物（气体、液体）的释放量不应超过国标ＧＢ６２４９规定值的２／５；⑦热网水中的放射性活度不应超过０．３７Ｂｑ／Ｌ；⑧建议应急状态分为三级，即应急待命、厂房应急和场区应急。     

Activity of administered radiopharmaceutical agents and the radiation burden of the Czechoslovak population caused by nuclear medicine

The authors assessed by means of questionnaires the activities of radiopharmaceuticals administered in departments of nuclear medicine in Czechoslovakia. The mean activities of individual radiopharmaceuticals are roughly equal as in Great Britain, but lower than in the Canadian province of Manitoba. The differences of activities used in different departments are approximately equal in all compared countries. In the Czech Republic the annual collective effective dose equivalent from nuclear medicine was 433 Sv in 1983 and 609 Sv in 1987. The mean effective dose equivalent per examination was 2.23 mSv in 1983 and 2.44 mSv in 1987. The mean effective dose equivalent per inhabitant of the Czech Republic was 0.042 mSv in 1983 and 0.059 mSv in 1987. The radiation dose of the Czech population from nuclear medicine amounts approximately to one tenth of the load from radiodiagnostics.     

Radon activity concentrations and effective doses in ancient Egyptian tombs of the Valley of the Kings.

Radon concentrations and equilibrium factors were measured in three pharaonic tombs during the year 1998. The tombs, which are open to the public are located in a limestone wadi on the West Bank of the River Nile at Luxor, 650 km south of Cairo. The radon activity concentration and equilibrium factor were measured monthly by two-integral nuclear track detectors (bare and diffusion detectors). Seasonal variation of radon concentrations, with summer maximum and winter minimum were observed in all tombs investigated. The yearly mean radon activity concentrations insidc the tombs ranged from 540 to 3115 Bq m(-3). The mean equilibrium factor over a year was found to be 0.25 and 0.32 inside and at the entrance, respectively. Estimated annual effective doses to tour guides ranged from 0.33 to 1.90 mSv, visitors receive doses from 0.65 to 3.80 microSv per visit. The effective dose to tomb workers did not exceed the 20 mSv yr(-1) limit.     

民航飞行人员宇宙辐射受照剂量的估算

目的计算被检测飞行人员个人宇宙辐射年均受照有效剂量。方法根据飞行指令数据使用美国联邦航空署开发的软件CARI 6,计算飞行航线的宇宙辐射有效剂量和乌鲁木齐地区地面的宇宙辐射有效剂量率 ,由运行软件输出数据计算个人年均受照有效剂量。结果乌鲁木齐地区地面个人年均受照有效剂量为 0 .42 0mSv ,新疆航空公司全部航线 1 997～ 1 999年平均宇宙辐射有效剂量率为 2 .381 μSv·h- 1 ( 0 .33～ 3.64μSv·h- 1 )。被检测飞行人员年均受照有效剂量为 2 .1 93mSv·a- 1 ( 0 .887～ 4.41 9mSv·a- 1 )。结论估算的 2 34个受检飞行人员的年均受照有效剂量均小于国际放射防护委员会 (ICRP)建议的限值 2 0mSv·a- 1 。     

Finger doses for staff handling radiopharmaceuticals in nuclear medicine

Radiation doses to the fingers of occupational workers handling 99mTc-labeled compounds and 131I for diagnostic and therapeutic procedures in nuclear medicine were measured by thermoluminescence dosimetry. METHODS: The doses were measured at the base of the ring finger and the index finger of both hands in 2 groups of workers. Group 1 (7 workers) handled 99mTc-labeled radiopharmaceuticals, and group 2 (6 workers) handled 131I for diagnosis and therapy. Radiation doses to the fingertips of 3 workers also were measured. Two were from group 1, and 1 was from group 2. RESULTS: The doses to the base of the fingers for the radiopharmacy staff and physicians from group 1 were observed to be 17+/-7.5 (mean+/-SD) and 13.4+/-6.5 microSv/GBq, respectively. Similarly, the dose to the base of the fingers for the 3 physicians in group 2 was estimated to be 82.0+/-13.8 microSv/GBq. Finger doses for the technologists in both groups could not be calculated per unit of activity because they did not handle the radiopharmaceuticals directly. Their doses were reported in millisieverts that accumulated in 1 wk. The doses to the fingertips of the radiopharmacy worker and the physician in group 1 were 74.3+/-19.8 and 53.5+/-21.9 microSv/GBq, respectively. The dose to the fingertips of the physician in group 2 was 469.9+/-267 microSv/GBq. CONCLUSION: The radiation doses to the fingers of nuclear medicine staff at our center were measured. The maximum expected annual dose to the extremities appeared to be less than the annual limit (500 mSv/y), except for a physician who handled large quantities of 131I for treatment. Because all of these workers are on rotation and do not constantly handle radioactivity throughout the year, the doses to the base of the fingers or the fingertips should not exceed the prescribed annual limit of 500 mSv.     

Nuclear medicine exposure in the United States, 2005-2007: preliminary results

Medical radiation exposure of the U.S. population has not been systematically evaluated for almost 25 years. In 1982, the per-capita dose was estimated to be 0.54 mSv and the collective dose 124,000 person-Sv. The preliminary estimates of the National Council on Radiation Protection and Measurements Scientific Committee 6-2 medical subgroup are that, in 2006, the per-capita dose from all medical exposure (not including radiotherapy) had increased almost 600% to 3.0 mSv and the collective dose had increased more than 700% to approximately 900,000 person-Sv. >Nuclear medicine accounted for only about 2% of all procedures but 26% of the total collective dose from diagnostic studies in medicine. In 1982, the estimated number of nuclear medicine procedures was about 7.5 million. The per-capita effective dose from nuclear medicine was 0.14 mSv and the collective dose was 32,000 person Sv. By 2005, the estimated number of procedures had increased to about 19.6 million. The per-caput effective dose increased to about 0.75 mSv and the collective dose to about 220,000 person Sv. There also has been a marked shift in the type of procedures being performed with cardiac scanning accounting for about 70% of procedures.     

Measurement of radiation exposure to a PET institution driver from patients injected with FDG

With the recent increase in FDG-PET examinations, concern has mounted regarding radiation exposure to hospital staff and the general public from patients injected with FDG. Because our PET institution is located 15 km from the hospital that provides these examinations, a driver has been designated to transport patients injected with FDG. This study was designed to measure the radiation dose to the driver from these patients (n=28) and to compare it with the estimated dose. A pocket dosimeter was used to measure radiation exposure to the driver. When the distances between the driver and patient were 1.1 m and 1.9 m, mean measured doses were 7.31 microSv and 2.26 microSv, respectively, while mean estimated doses were 8.61 microSv and 2.82 microSv, respectively, per trip. It was presumed that maximum radiation exposure per year was between 3.02 mSv (1.1 m) and 0.92 mSv (1.9 m). According to our data, the measured dose was 20% lower than the estimated dose. This discrepancy may be due to the difference between the volume source (measured dose) and point source (estimated dose).     

云南省部分地区环境放射性水平调查及居民所受外照射剂量估算

目的 探讨云南省部分地区的环境放射性水平及所致居民外照射剂量。方法 通过对表层土壤、近地面空气气溶胶和水中放射性核素的γ能谱测量分析,利用卫生系统全国土壤调查中选用的模式,估算环境中²³⁸U、²²⁶Ra、²³²Th、⁴⁰K和¹³⁷Cs所致居民的受照剂量。利用美国航空管理局的CARI-6软件,估算了调查地区居民的宇宙辐射剂量。 结果 调查地区近地面空气气溶胶和水样中各核素比活度都低于探测下限。土壤中放射性核素所致居民人均外照射年有效剂量为0.5206 mSv/年,其中,0.52 mSv/年来自土壤中天然放射性核素,0.6 μSv/年来自土壤中¹³⁷Cs。宇宙辐射所致居民剂量为0.61 mSv/年。结论 宇宙辐射和土壤中天然辐射对居民所受外照射剂量贡献为99.95%,人工放射性核素¹³⁷Cs所致居民的外照射剂量贡献仅为0.05%。     

Radiation doses from nuclear medicine patients to an imaging technologist: relation to ICRP recommendations for pregnant workers.

The ICRP has now recommended that the dose limit to the surface of the mother's abdomen during the declared term of pregnancy is reduced to 2 mSv. Direct measurements of the radiation dose to technologists carrying out a variety of imaging studies were made. The average dose ranged from 0.3 micro Sv for a liver scan to 5.3 micro Sv for a brain scan. Using national data for the frequency of nuclear medicine studies, a weighted average figure of 1.5 micro Sv per study was derived. A technologist could therefore perform approximately eight imaging studies per day during the declared term of her pregnancy and remain within the proposed limit. Generally, there should be no need to alter a technologist's duties during her pregnancy, and these findings should be helpful in allaying any anxiety.     

Patient and staff dose during CT guided biopsy, drainage and coagulation

Patient and staff dose during CT guided coagulation of osteoid osteoma, tissue biopsy and abscess drainage were evaluated retrospectively on a conventional CT scanner and prospectively on a scanner equipped with fluoroscopic CT. The computed tomography dose index (CTDI) and the individual dose equivalent, i.e. the penetrating dose for workers at a depth of 10 mm tissue, were measured. Evaluation of CTDI enabled effective dose and maximum skin entrance doses for the patient to be determined. Doses were assessed for 96 CT guided interventions, including 16 drainages with average effective doses of 13.5 mSv and 9.3 mSv for the conventional CT scanner and the scanner with spiral CT fluoroscopy, respectively, 49 biopsies (effective doses of 8 mSv and 6.1 mSv, respectively), and 31 coagulations of osteoid osteoma (effective doses of 2.1 mSv and 0.8 mSv, respectively). Effective doses to patients were in the same range as those observed for regular diagnostic CT examinations. Entrance skin doses were well below the 2 Gy threshold for deterministic skin effects on the CT scanner equipped with fluoroscopic function (0.03-0.33 Gy), whilst skin doses on the conventional scanner were considerably higher (0.09-1.61 Gy). This is mainly owing to the fact that on the conventional scanner mAs was rarely reduced for scans evaluating needle position whereas low mAs per rotation was selected on the scanner with the fluoroscopy option. The maximum dose to a worker measured outside the lead apron was 28 microSv for one single procedure. The mean dose per procedure was below 10 microSv for radiologists and below 1 microSv for radiographers. Correcting for attenuation of the lead apron, the doses to workers are very low.     

Exposure of medical personnel to radiation during radionuclide therapy practices

OBJECTIVES: Radioisotopes that emit beta radiation are used for the treatment of hepatocellular carcinoma, of arthritic patients (radiosynovectomy) and treatment of bone metastases with, respectively, I-labelled lipiodol, colloidal citrate of Y or and Sm-labelled EDTMP. Radiation energy of these radioisotopes that emit beta or beta and gamma radiation (from 300 to 2000 keV) leads to an increase in radiation dose received by nuclear medicine staff. In this paper we focused on clinical and laboratory staff exposure during these types of metabolic radiation therapies. METHODS: Cylindrical LiF thermoluminescence dosimeters were used to measure radiation-related whole-body doses (WBDs) and finger doses of the clinical staff. RESULTS: Exposure of the two radiopharmacists and three nurses taking part in I-labelled lipiodol, Y-colloid and Sm-EDTMP therapies, for 12 months in succession, were 146 microSv and 750 microSv, respectively, considering WBD, and 14.6 mSv and 6.5 mSv, respectively, considering finger doses. Extrapolated annual exposures (six radiosynovectomies per year) for the rheumatologists were estimated to be 21 microSv (WBD) and 13.2 mSv (finger dose). Extrapolated annual WBDs and finger doses (25 I-labelled lipiodol treatments per year) for radiologists were estimated to 165 microSv and 3.8 microSv, respectively. CONCLUSION: Fortunately, these doses were always lower than the limits reported in the European Directive EURATOM 96/29 05/13/1996 (WBD <20 mSv.year; finger dose: 500 mSv.year) but have to be added to those relative to other metabolic radiotherapies such as radioiodine treatments and new metabolic radiotherapies (Y-conjugated peptides or antibodies). Nevertheless, the global exposure of medical staff involved in all these clinical practices justifies dosimetry studies to validate protocols and radiation protection devices for each institution.     

UK nuclear medicine survey 2003-2004

OBJECTIVES: This survey was designed to assess the trends in the frequencies of nuclear medicine procedures in the UK and to determine their contributions to the annual collective effective dose to the UK population. The average activities administered by nuclear medicine departments were compared with guidance on diagnostic reference levels issued by the Administration of Radioactive Substances Advisory Committee. METHOD: The survey was carried out by e-mailing a questionnaire to every known nuclear medicine centre in the UK. RESULTS: The total number of procedures performed annually has increased by 36% over the last 10 years to a level of about 11 procedures per 1000 head of population in the financial year 2003-2004. Seventy-three per cent of all nuclear medicine administrations are for planar imaging, with single-photon emission computed tomography and positron emission tomography contributing 16% and 2%, respectively. Non-imaging diagnostic procedures represent 7% of all nuclear medicine administrations, and therapy 2%. Bone scans continue to be the most frequent procedure. The UK annual collective effective dose from diagnostic nuclear medicine is about 1600 man Sv, resulting in an annual per caput dose of nearly 0.03 mSv. Bone scans are the largest contributor to the collective dose, but myocardium scans are close behind. Planar imaging is responsible for 62% of the total collective effective dose from diagnostic nuclear medicine in the UK, with single-photon emission computed tomography, positron emission tomography and non-imaging contributing 33%, 5% and 0.3%, respectively. CONCLUSIONS: The practice of nuclear medicine is still expanding in the UK with single-photon emission computed tomography imaging of the myocardium rapidly approaching bone scans as the main contributor to population exposure. The activities administered for most procedures have remained substantially unchanged and adhere closely to those recommended by the Administration of Radioactive Substances Advisory Committee.     

Dosimetry studies in Zaborie village.

Dosimetry studies in Zaborie, a territory in Russia highly contaminated by the Chernobyl accident, were carried out in July, 1997. Studies on dosimetry for people are important not only for epidemiology but also for recovery of local social activity. The local contamination of the soil was measured to be 1.5-6.3 MBq/m2 of Cs-137 with 0.7-4 microSv/h of dose rate. A case study for a villager presently 40 years old indicates estimations of 72 and 269 mSv as the expected internal and external doses during 50 years starting in 1997 based on data of a whole-body measurement of Cs-137 and environmental dose rates. Mean values of accumulated external and internal doses for the period from the year 1986 till 1996 are also estimated to be 130 mSv and 16 mSv for Zaborie. The estimation of the 1986-1996 accumulated dose on the basis of large scale ESR teeth enamel dosimetry provides for this village, the value of 180 mSv. For a short term visitor from Japan to this area, external and internal dose are estimated to be 0.13 mSv/9d (during visit in 1997) and 0.024 mSv/50y (during 50 years starting from 1997), respectively.     

Fetal dose estimates and the ICRP abdominal dose limit for occupational exposure of pregnant staff to technetium-99m and iodine-131 patients

The International Commission on Radiological Protection has recently recommended a supplementary dose limit of 2 mSv to the abdominal surface of a pregnant member of staff in order to provide protection to her fetus comparable to that in members of the public, whose annual limit is recommended to be 1 mSv. In order to determine whether this apparent attenuation factor of 50% is appropriate for nursing and imaging staff exposed to nuclear medicine patients, estimates were made of the ratios of the maternal abdominal surface to fetal dose appropriately weighted for time, distance and dose rate. Thermoluminescent dosimeter (TLD) measurements were made at various depths in an anthropomorphic phantom irradiated at different distances by a distributed source of either technetium-99m or iodine-131 in order to determine the corresponding attenuation factors at the average fetal midline depth. Dose estimates were based on these factors and on published values of dose rate and exposure times for nursing and imaging staff at these distances from the patient. Fetal doses to nursing staff caring for an adult^99mTc patient were estimated to vary from 86 Sv to 1.6 Sv, with the corresponding ratio of the abdominal surface to fetal dose varying from about 1.8:1 to 1.5:1 as the patient became less dependent on nursing care and the mean distance from the patient increased. Fetal doses to imaging staff varied from 1.12 Sv to 0.17 Sv for three types of^99mTc scan, but the ratio only varied from 1.4:1 to 1.3:1. Fetal doses to imaging staff were estimated to be 6.7 Sv and 9.0 Sv for a whole-body scan of a thyroid cancer patient after 1311 ablation and therapy respectively, and the ratio was 1.3:1 for both types of scan. It was concluded that for a pregnant ward nurse or imaging technologist exposed to an adult or paediatric patient administered^99mTc or¹³¹I, a dose limit of 1.3 mSv to the maternal abdominal surface will restrict their fetal dose to 1 mSv. A pregnant imaging technologist should perform no more than six adult^99mTc studies or one¹³¹I whole-body scan per day, and may have to wear a more sensitive personal dosimeter than a film badge.     

Radiation dose rates from patients undergoing PET: implications for technologists and waiting areas

Increasingly hospitals are showing an interest in developing their imaging services to include positron emission tomography (PET). There is therefore a need to be aware of the radiation doses to critical groups. To assess the effective whole-body dose received by technologists within our dedicated PET centre, each staff member was issued with a dose rate meter, and was instructed to record the time spent in contact with any radioactive source, the dose received per working day and the daily injected activity. On average each technologist administered 831 MBq per day. The mean whole-body dose per MBq injected was 0.02 microSv/MBq(-1). The average time of close contact (<2.0 m) with a radioactive source per day was 32 min. The average effective dose per minute close contact was 0.5 microSv/min(-1), which resulted in a mean daily effective dose of 14.4 microSv. No technologist received greater than 60 microSv (the current UK limit for non-classified workers) in any one day, and in general doses received were less than 24 microSv, the daily dose corresponding to the proposed new annual limit for non-classified workers of 6.0 mSv per annum. However, we recognise that the layout of nuclear medicine departments will not mirror our own. We therefore measured the instantaneous dose rates at 0.1, 0.5, 1.0 and 2.0 m from the mid-thorax on 115 patients immediately after injection, to provide estimates of the likely effective doses that might be received by technologists operating dual-headed coincidence detection systems, and others coming into contact in the waiting room with patients who have been injected with fluorine-18 fluorodeoxyglucose. The mean (95th percentile) dose rates measured at the four aforementioned distances were 391.7 (549.5), 127.0 (199.8), 45.3 (70.0) and 17.1 (30.0) microSv/h(-1), respectively. A number of situations have been modelled showing that, with correct planning, FDG studies should not significantly increase the effective doses to technologists. However, one possible area of concern is that, depending on the number of patients in a waiting area at any one time, accompanying persons may approach the limits set by the new UK IRR 1999 regulations for members of the public.     

Patient doses from computed tomography in Manitoba from 1977 to 1987

The number of patients undergoing computed tomographic (CT) examinations in the province of Manitoba is reported for the period 1977-1987. The annual patient throughput has increased from 4.2 per 10(3) population in 1978 to 18.2 per 10(3) population in 1987. Over the same period, the per capita population dose from CT has increased from 4.2 to 81.0 microSv. This substantial rise has occurred because of an increase in patient throughput, higher radiation doses associated with modern CT scanners and an increasing proportion of (higher dose) body CT studies. The mean patient dose on a second generation (EMI 5005) scanner was about 1.4 mSv, whereas the corresponding doses on third generation scanners operating in Manitoba were 3.9 mSv (GE 9800) and 5.6 mSv (Siemens DRH).     

Safe radiation exposure of medical personnel by using simple methods of radioprotection while administering 131I-lipiodol therapy for hepatocellular carcinoma

The intra-arterial administration of 131I-lipiodol is a therapeutic approach increasingly used for the treatment of inoperable hepatocellular carcinomas. This technique has even become the reference treatment for hepatocellular carcinomas with portal thrombosis and is the only effective treatment to reduce the risk of recurrence among patients who could benefit from surgical operation. Currently, few data have been published concerning the levels of exposure for personnel carrying out this type of treatment. We undertook a dosimetric study targeted mainly on the exposure of the person performing the injection of 131I-lipiodol to show that this treatment can be carried out with an exposure at the extremities distinctly lower than the regulatory annual threshold by using simple means of radioprotection. The point of puncture was carried out at the level of left femoral artery, the preparation and injection of the therapeutic dose was carried out extemporaneously by the nuclear medicine specialist using a 10 ml syringe (for an injected volume of 4 ml) fitted with an adapted syringe protector. The injection was carried out as rapidly as possible under scopic control while avoiding reflux, with compression carried out by the radiologist. This study comprises 52 intra-arterial injections of 131I-lipiodol (2016+/-92 MBq). For the nuclear medicine specialists, 52 measurements were carried out at the level of the thorax and 41 on the fingers. For the radiologists, 22 measurements were carried out at the level of the thorax and six on their index fingers; nine measurements were carried out at the level of the thorax for the technologist and four at the level of the thorax for the stretcher bearer. For the nuclear medicine specialists, the average dose received at the level of the fingers varies between 140 and 443 microSv (according to the fingers) and the average dose at the thorax is 17 microSv. For the radiologists, the average dose received is 215 microSv at the level of the fingers and 15 microSv at the thorax. These results show that the administration of high therapeutic activities of 131I-lipiodol can be carried out for the exposed personnel with a dose at the level of the fingers much lower than the European regulatory limit of 500 mSv.     

Assessment of radiation safety instructions to patients based on measured dose rates following prostate brachytherapy

PURPOSE: To validate radiation safety instructions to patients and to evaluate the potential radiation doses to members of the public after (125)I or (103)Pd prostate implantation. METHODS AND MATERIALS: Radiation dose rate measurements were made in the immediate postoperative period on 636 consecutive patients with stage T1-T2 prostate cancer who underwent transperineal (125)I or (103)Pd implantation at Memorial Sloan-Kettering Cancer Center during the period from August 1995 through January 2003. RESULTS: The mean radiation dose rate at the anterior skin surface following a prostate implant was 37 microSv/hr for (125)I and 8 microSv/hr for (103)Pd. At 30 cm from the anterior skin surface, these dose rates were reduced to 6 microSv/hr for (125)I and 3 microSv/hr for (103)Pd. At 1 m from the anterior skin surface the dose rates from both types of implants were reduced to less than 1 microSv/hr. The effect of body weight on dose rates from (125)I sources was examined for a select sub-group of patients and the measured dose rate was found to decrease with increasing body weight. In another group of patients, dose rate measurements were made on both lateral skin surfaces and were less than 16.8 microSv/hr in all cases. Assuming a 33% occupancy factor and utilizing the mean measured dose rate for (125)I, the time required to reach an effective dose equivalent limit of 5 mSv for caregivers was estimated to be 19 days on contact with the skin surface. Using a similar calculation, the lifetime doses for (125)I at a distance of 30 cm from the anterior skin surface, as well as the lifetime doses for (103)Pd on contact with the skin surface and at 30 cm from the anterior skin surface can be shown to be less than 5 mSv. CONCLUSIONS: The large number of cases available for this study permits a validation of radiation safety recommendations and provides concrete information from which the permitted exposure times following implantation can be estimated. The data support the conclusion that patients treated with these implants do not represent a radiation risk to members of the public.     

Radiation dose rates from paediatric patients undergoing 99Tcm investigations.

Infants or children undergoing nuclear medicine investigations may subsequently come into close contact with nurses or parents responsible for their care. In order to estimate the radiation dose to these individuals, and to formulate appropriate recommendations, dose rates were measured at distances of 0.1, 0.5 and 1.0 m from 148 paediatric patients who had undergone one of 12 99Tcm studies. The maximum dose rates of 70, 14 and 5 microSv h-1 at these distances were not greater than the corresponding maximum values found in an earlier study of adult patients. However, the maximum dose rates per unit activity of 0.5, 0.2 and 0.1 microSv h-1 MBq-1 were greater than the corresponding maximum 99Tcm adult values, consistent with a general increase of dose rate per unit activity with decrease of body weight observed in the paediatric measurements. A parent caring for and feeding a young infant is most unlikely to receive a dose equivalent of 1 mSv, and a nurse attending to one young radioactive patient is most unlikely to receive a dose equivalent in a working day of 60 microSv. The data obtained should allow radiation doses to be estimated and appropriate recommendations to be formulated for other circumstances, including any future legislative changes in dose limits or derived levels.     

Radiation dose rates from adult patients undergoing nuclear medicine investigations

Adult patients undergoing nuclear medicine investigations may subsequently come into close contact with members of the public and hospital staff. In order to expand the available dosimetry and derive appropriate recommendations, dose rates were measured at 0.1, 0.5 and 1.0 m from 80 adult patients just before they left the nuclear medicine department after undergoing one of eight 99Tcm studies, an 123I thyroid, an 111In leucocyte or a 201Tl cardiac scan. The maximum departure dose rates at these distances of 150, 30 and 7.3 microSv h-1 were greater than those found in similar published studies of adult and paediatric patients. To limit the dose to an infant to less than 1 mSv, an 111In leucocyte scan is the only investigation for which it may be necessary to restrict close contact between the infant and a radioactive parent, depending on the dose rate near the surface of the patient, the parent's habits and how fretful is the infant. It is unlikely that a ward nurse will receive a dose of 60 microSv in a working day if caring for just one radioactive adult patient, unless the patient is classified as totally helpless and has undergone a 99Tcm marrow, bone or brain scan. The data and revised calculations of effective exposure times based on a total close contact time of 9 h in every 24 h period should allow worst case estimates of radiation dose to be made and recommendations to be formulated for other circumstances, including any future legislative changes in dose limits or derived levels.