Pediatr Radiol (2015) 45:706–713 DOI 10.1007/s00247-014-3211-x

ORIGINAL ARTICLE

Radiation doses for pediatric nuclear medicine studies: comparing the North American consensus guidelines and the pediatric dosage card of the European Association of Nuclear Medicine Frederick D. Grant & Michael J. Gelfand & Laura A. Drubach & S. Ted Treves & Frederic H. Fahey

Received: 9 April 2014 / Revised: 5 September 2014 / Accepted: 13 October 2014 / Published online: 1 November 2014 # Springer-Verlag Berlin Heidelberg 2014

Abstract Background Estimated radiation dose is important for assessing and communicating the risks and benefits of pediatric nuclear medicine studies. Radiation dose depends on the radiopharmaceutical, the administered activity, and patient factors such as age and size. Most radiation dose estimates for pediatric nuclear medicine have not been based on administered activities of radiopharmaceuticals recommended by established practice guidelines. The dosage card of the European Association of Nuclear Medicine (EANM) and the North American consensus guidelines each provide recommendations of administered activities of radiopharmaceuticals in children, but there are substantial differences between these two guidelines. Objective For 12 commonly performed pediatric nuclear medicine studies, two established pediatric radiopharmaceutical administration guidelines were used to calculate updated radiation dose estimates and to compare the radiation exposure resulting from the recommendations of each of the guidelines. Materials and methods Estimated radiation doses were calculated for 12 common procedures in pediatric nuclear medicine using administered activities recommended by the F. D. Grant (*) : L. A. Drubach : S. T. Treves : F. H. Fahey Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Boston Children’s Hospital, 300 Longwood Ave., Boston, MA 02115, USA e-mail: [email protected] F. D. Grant : L. A. Drubach : S. T. Treves : F. H. Fahey Joint Program in Nuclear Medicine, Department of Radiology, Harvard Medical School, Boston, MA 02115, USA M. J. Gelfand Section of Nuclear Medicine, Department of Radiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, USA

dosage card of the EANM (version 1.5.2008) and the 2010 North American consensus guidelines for radiopharmaceutical administered activities in pediatrics. Based on standard models and nominal age-based weights, radiation dose was estimated for typical patients at ages 1, 5, 10 and 15 years and adult. The resulting effective doses were compared, with differences greater than 20% considered significant. Results Following either the EANM dosage card or the 2010 North American guidelines, the highest effective doses occur with radiopharmaceuticals labeled with fluorine-18 and iodine-123. In 24% of cases, following the North American consensus guidelines would result in a substantially higher radiation dose. The guidelines of the EANM dosage card would lead to a substantially higher radiation dose in 39% of all cases, and in 62% of cases in which patients were age 5 years or younger. Conclusion For 12 commonly performed pediatric nuclear medicine studies, updated radiation dose estimates can guide efforts to reduce radiation exposure and provide current information for discussing radiation exposure and risk with referring physicians, patients and families. There can be substantial differences in radiation exposure for the same procedure, depending upon which of these two guidelines is followed. This discordance identifies opportunities for harmonization of the guidelines, which may lead to further reduction in nuclear medicine radiation doses in children. Keywords Nuclear medicine . Pediatric . Internal dosimetry . Radiopharmaceutical dose . Guidelines

Introduction Over the past 40 years, the utility of nuclear medicine procedures has been demonstrated for the clinical evaluation of

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children with a wide variety of medical conditions, including urological, orthopedic, neurological, gastrointestinal and oncological conditions [1]. While medical imaging provides enormous benefit, radiation exposure also may carry risk, and the judicious use of radiologic and nuclear medicine procedures requires a balancing of these potential benefits and risks in assessing the overall gain from exposing a patient to radiation. Infants and children may have a greater potential risk than adults for developing late effects of radiation exposure [2, 3]. Therefore, it is considered prudent to try to minimize even a small radiation risk, while ensuring that patients receive the benefits of undergoing nuclear medicine procedures. An important factor in assessing the relative risks and benefits of any radiation-based clinical study is estimating the radiation dose to the patient. Weighing these benefits and potential harms requires a quantifiable indicator of radiation dose, the effective dose, which can be translated to risk. Although effective dose estimates routinely are available for adults (for example, on the package insert of the radiopharmaceutical), these estimates are unlikely to accurately reflect radiation exposure in children. Pediatric patients are a particular challenge, as body size and the spatial relationships of individual organs can be very different compared to those of a typical adult. Estimates of effective dose do not apply to any particular individual and should not be used to express the radiation burden or potential harm to an individual patient. Effective dose is, however, a useful method of comparing the potential radiation effects resulting from different practices within a population, or to children of a similar age group, but should be used with caution when comparing the radiation risk of one age group to another since the organ-weighting factors are averaged over both age and gender. The International Commission on Radiological Protection (ICRP) has issued a number of reports addressing the radiation dose related to radiopharmaceutical administration for diagnostic nuclear medicine procedures. The first of these, ICRP Publication 17, was published in 1971 [4], and updated in ICRP Publications 53 [5] and 80 [6] with the most recent report, ICRP Publication 106 [7], being released in 2008. These reports represent a compilation of available data that may be used to estimate radiation dose, expressed as radiation dose to specified target organs as well as the effective dose, to a population of patients to whom a specific radiopharmaceutical has been administered. ICRP publications 53, 80 and 106 provide conversion factors for administered activity to effective dose (in mSv/MBq) based on models of patients of different ages (1-, 5-, 10- and 15-year-olds and adult). These values were used in the calculations in this report. Until recently, the amount of a radiopharmaceutical administered to children of similar size might vary by as much as twenty-fold among different institutions [8]. Recognition of this variation in administered activities and increasing

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awareness of potential radiation risk in children has led to national and international efforts to standardize and decrease administered activities of radiopharmaceuticals in pediatric nuclear medicine [9–11]. Two major guidelines providing recommended administered activities for children have been developed in Europe and North America. The European Association of Nuclear Medicine (EANM) issued guidance for administered activities in children that included a dosage card that provided recommended administered activities for a variety of diagnostic nuclear medicine procedures [9]. The underlying model of the EANM dosage card is to provide similar radiation doses to all patients undergoing a particular nuclear medicine procedure. Therefore, for each radiopharmaceutical, recommended administered activities were calculated so that patients in all age groups receive similar estimated effective doses [12]. More recently, a panel of North American experts representing the Society of Nuclear Medicine and Molecular Imaging, the American College of Radiology, the Society of Pediatric Radiology and the Image Gently campaign developed guidelines by identifying best practices and reaching expert consensus [10, 11]. These North American consensus guidelines are strictly weight-based for 10 of the 12 procedures included in the guideline, with recommended administered activities corrected for patient size (expressed as mCi/kg or MBq/kg). Consequently, for each nuclear medicine procedure, these guidelines tend to result in similar levels of image noise, and thus image quality, for patients of all sizes [11]. Discordance between these two guidelines reflects, in part, the different models used to develop them. In addition, for some radiopharmaceuticals, there are substantial differences between the two guidelines in the reference adult administered activities from which the pediatric administered activities are derived. These two approaches to developing pediatric guidelines have led to differences in the recommended administered activities for many radiopharmaceuticals. Thus, there could be substantial differences in radiation exposure for the same procedure, depending upon which of the two guidelines was followed. However, most published radiation dose estimates for pediatric nuclear medicine procedures have not been based on either of these guidelines for administered activities of radiopharmaceuticals in children. Therefore, using these guidelines, we updated and compared the radiation absorbed dose estimates for 12 commonly performed procedures in pediatric nuclear medicine.

Materials and methods Twelve diagnostic procedures commonly performed in the practice of nuclear medicine were identified for inclusion in this study (Table 1). To be evaluated, a nuclear medicine procedure had to be included in both the 2010 North

708 Table 1 Twelve commonly performed pediatric nuclear medicine studies for which estimates of effective dose and critical organ dose were made PET torso: 18F-FDG PET brain: 18F-FDG Skeletal scintigraphy: 99m Tc-methylene diphosphonate 18 F-sodium fluoride PET Lung perfusion scan: 99mTc-MAA Hepatobiliary scintigraphy: 99mTc-disofenin Dynamic renography: 99mTc-MAG3 Renal cortical scan: 99mTc-DMSA Radionuclide cystography: 99mTc-sodium pertechnetate Meckel scan: 99mTc-sodium pertechnetate Gastric emptying/reflux (solid): 99mTc-labeled sulfur colloid Whole-body MIBG scan: 123I-MIBG DMSA Dimercaptosuccinic acid, FDG Fluorodeoxyglucose, MAA Macroaggregated albumin, MAG3 Mercaptoacetyltriglycine, MIBG Metaiodobenzylguanidine, PET Positron emission tomography

American Consensus Guidelines [10, 11] and the EANM dosage card (version 1.5.2008) [9]. For each of the 12 procedures, these two guidelines were used to determine the recommended administered activities for five ages: 1, 5, 10 and 15 years and adult. For each age group, the age-specific nominal whole-body weight reported by Cristy and Eckerman [13] was used to calculate the recommended administered activities. Where appropriate by the age-specific weight, the recommended minimum or maximum administered activity indicated by each guideline was used for calculations. No alterations in calculations were made for gender. Calculations included effective dose and individual organabsorbed doses. The absorbed dose of the individual organ receiving the maximum organ-absorbed dose (critical organ) was identified. For each radiopharmaceutical, age-appropriate effective dose (in mSv/MBq) and organ doses (in mGy/MBq) were obtained from ICRP Publication 53 [5], ICRP Publication 80 [6], ICRP Publication 106 [7], NUREG/CR-6345 [14] or other published reports [15]. For calculation of effective dose, these publications all use the tissue-weighting factors available in ICRP Publication 60 [16] and not those in the recently published ICRP Publication 103 [17]. For radionuclide cystography, tissue-weighting data have not been reported for adult (nominal weight: 70 kg) patients, so radiation dose estimates were computed for only four ages for this procedure. For each radiopharmaceutical and age group, the estimated effective doses resulting from use of the North American Consensus Guidelines and the EANM dosage card were compared. Descriptive statistical analysis was performed and differences of greater than 20% were identified. The specified threshold of 20% was chosen primarily because the U.S. Nuclear Regulatory Commission specifies this limit for the difference between prescribed and administered

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radiopharmaceutical activities [18], and thus it may be considered a clinically significant variance in administered activity.

Results The estimated effective dose and the critical organ radiation absorbed dose were calculated for 5 age groups and 12 diagnostic nuclear medicine studies, using both the North American consensus guidelines and the EANM dosage card (Table 2). In the absence of organ-weighting data for adults, effective dose calculations could not be performed for radionuclide cystography performed in adult (nominal weight: 70 kg) patients. Therefore, effective dose and critical organ dose were calculated for 59 theoretical cases. Using the administered activities recommended by either guideline, the highest radiation exposures will occur with the radiopharmaceuticals labeled with 18F or 123I, including 18FFDG, 18F-sodium fluoride (18F-NaF), and 123I-MIBG. Out of the 12 procedures included in this study, the lowest effective doses will occur when using [99mTc] sodium pertechnetate for radionuclide cystography. In 22 of 59 (37%) cases, the difference in estimated effective doses that could result from following the two guidelines was less than 20% of the lower of the two effective doses. In 14 of 59 (24%) cases, using an administered activity recommended by the North American consensus guidelines would result in an effective dose more than 20% greater than following the EANM dosage card. This is most notable for studies using 99mTc-MAG3 for dynamic renography and [99mTc] sodium pertechnetate for radionuclide cystography. In 23 of 59 (39%) cases, using the administered activities recommended in the EANM dosage card would result in an effective dose more than 20% greater than following the North American guidelines. The differences between the effective doses resulting from use of the North American consensus guidelines and the EANM dosage card were more pronounced in younger patients. For ages 1 year or 5 years, using the administered activities indicated by the EANM dosage card would result in an estimated effective dose at least 20% greater than that provided by the North American consensus guidelines in 15 of 24 (62%) cases. This includes the studies providing relatively higher radiation doses to children ages 1 and 5 years when performed following either guideline, including 18F-FDG PET torso, 18F-FDG PET brain, 18F-NaF bone scan, wholebody 123I-MIBG scan, and hepatobiliary scan with 99mTcdisofenin. Conversely, in the same age groups, using the administered activities indicated by the North American consensus guidelines would result in an estimated effective dose of at least 20% greater than that provided by the EANM

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Table 2 Radiation dose estimates for 12 common pediatric nuclear medicine procedures (with indicated radiopharmaceuticals) for adults and children at four different ages using the administered activities

recommended by the European Association of Nuclear Medicine (EANM) Dosage Card (version 1.5.2008) [6] and the 2010 North American (NA) consensus guidelines [7]

Age: Nominal weight (kg):

1 year 9.8

5 years 19

10 years 32

15 years 55

Adult 70

Fluorodeoxyglucose (FDG) PET torso 18 F-FDG EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (5.2 MBq/kg) NA effective dose (mSv) NA critical organ dose (mGy) – Bladder

ICRP 106 70 6.7† 51 4.8 24

120 6.7† 99 5.5 34

189 7.0 166 6.2 42

302 7.2 286 6.9 46

370 7.0 364 6.9 47

Fluorodeoxyglucose (FDG) PET brain 18 F-FDG EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (3.7 MBq/kg) NA effective dose (mSv) NA critical organ dose (mGy) – Bladder

ICRP 106 70* 6.7† 37* 3.5 17

70* 3.9 70 3.9 24

102 3.8 118 4.4 30

163 3.9 204 4.9† 33

200 3.8 259 4.9† 34

Bone scan 99m Tc-methylene diphosphonate (MDP) EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (10.6 MBq/kg) NA effective dose (mSv) NA critical organ dose (mGy) – Bone

ICRP 80 80 2.2 91 2.5 48

162 2.3 177 2.5 39

255 2.8 298 3.3 39

408 2.9 512 3.6† 42

500 2.8 651 3.7† 41

Bone scan 18 F-sodium fluoride EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (2.22 MBq/kg) NA effective dose equivalent (mSv) NA critical organ dose (mGy) – Bladder

ICRP 53 70* 11.9† 22 3.7 24

70* 6.0† 42 3.6 26

102 5.3† 71 3.7 28

163 5.5† 122 4.2 33

200 5.4† 155 4.2 39

Lung perfusion scan 99m Tc-MAA (macroaggregated albumin) EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (1.1 MBq/kg) NA effective dose (mSv) NA critical organ dose (mGy) – Lung

ICRP 80 15 0.95 15* 0.93 5.8

26 0.88 22 0.72 4.2

41 0.94 37 0.82 4.6

65 1.04 63 0.98 5.9

90 0.88 78 0.85 5.1

Hepatobiliary scan 99m Tc-disofenin EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (1.85 MBq/kg) NA effective dose (mSv) NA critical organ dose (mGy) –Gallbladder

ICRP 80 28 2.8† 18* 1.8 17.6

49 2.2† 35 1.6 9.8

77 2.2† 59 1.7 9.5

122 2.6† 102 2.1 12.2

150 2.5 130 2.2 14.2

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Table 2 (continued) Age: Nominal weight (kg):

1 year 9.8

5 years 19

10 years 32

15 years 55

Adult 70

Dynamic renography 99m Tc-mercaptoacetyltriglycine (MAG3) EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (3.7 MBq/kg) NA effective dose (mSv) NA critical organ dose (mGy) – Bladder

ICRP 80 23 0.51 37* 0.81† 1.2

33 0.40 70 0.84† 1.3

45 0.54 118 1.42† 2.0

61 0.55 204 1.83† 2.8

70 0.50 259 1.81† 2.8

Renal cortical scan 99m Tc-dimercaptosuccinic acid (DMSA) EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (1.85 MBq/kg) NA effective dose (mSv) NA critical organ dose (mGy) – Kidney

ICRP 80 33 1.22† 18 0.67 0.76

48 1.00† 35 0.73 0.43

64 0.96 59 0.89 0.30

87 0.96 102 1.12 0.22

100 0.88 130 1.14† 0.18

Radionuclide cystography [99mTc] sodium pertechnetate EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (MBq) NA effective dose (mSv) NA critical organ dose (mGy) – Bladder

MIRD 20* 0.03 37* 0.06† 0.90

20* 0.02 37* 0.03† 0.50

20* 0.01 37* 0.02† 0.33

20* 0.01 37* 0.02† 0.23

– – – – –

Meckel scan [99mTc] sodium pertechnetate EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (1.85 MBq/kg) NA effective dose (mSv) NA critical organ dose (mGy) – Colon

ICRP 80 20* 1.60† 11 0.86 2.9

26 1.09† 21 0.89 3.0

41 1.06 36 0.92 3.1

65 1.11 61 1.04 3.2

80 1.04 78 1.01 3.3

Gastric emptying/reflux (solid) 99m Tc-labeled sulfur colloid EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (MBq) NA effective dose (mSv) NA critical organ dose (mGy) – Colon

ICRP 80 10* 1.40 9.25* 1.30 6.1

13 0.99† 9.25* 0.70 3.2

20 0.98 18.5* 0.89 4.1

33 1.01† 18.5* 0.57 2.4

40 0.96† 18.5* 0.44 1.9

Whole-body meta-iodobenzylguanidine (MIBG) scan 123 I-MIBG EANM administered activity (MBq) EANM effective dose (mSv) NA administered activity (5.2 MBq/kg) NA effective dose (mSv) NA critical organ dose (mGy) – Liver

ICRP 80 80* 5.4† 51 3.5 17

130 4.8† 99 3.7 18

204 5.3† 166 4.3 22

326 5.5 286 4.9 25

400 5.2 364 4.7 24

Calculations of effective dose and critical organ dose are based on International Commission on Radiological Protection (ICRP) 53 [3], ICRP 80 [4], ICRP 106 [5] and NUREG/CR-6345 (MIRD) [10], as indicated for each study. (*) indicates use of a recommended minimum or maximum administered activity indicated by the guideline. († ) indicates that the indicated effective dose (mSv) is at least 20% greater than the effective dose calculated using the other (EANM or NA) consensus guideline

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dosage card in only 4 of 24 (17%) cases (99mTc-MAG3 renography and radionuclide cystography). For each procedure, the organ that is considered the critical organ is independent of the administered activity of radiopharmaceutical. The most common critical organ is the urinary bladder, which is the critical organ for 5 of the 12 procedures. At the administered activities recommended by the two guidelines, the highest radiation absorbed doses to other critical organs are those produced by 99mTc-MDP to bone and 123I-MIBG to liver.

Discussion The medical use of radiation for imaging and evaluation of organ function has revolutionized medicine. Since the discoveries of X-rays and radioactivity, medical imaging has become an indispensable part of the practice of medicine. The detrimental effects of radiation were recognized very soon after these discoveries. A single exposure to higher doses of ionizing radiation can cause acute, dose-dependent toxicity, such as skin burns or bone marrow suppression. However, of greater concern with medical imaging are the stochastic effects of radiation expressed perhaps years later, most especially carcinogenesis. The radiation risk of a nuclear medicine or radiology procedure depends on the level of radiation exposure to the different organs and tissues of the body, which have differing sensitivities to radiation. For any radiation exposure, the radiation burden can be expressed as the effective dose, which is a quantitative expression of the stochastic radiation harm to a population of specified individuals. Although originally developed to express the radiation effect in radiation workers [19], the concept of effective dose also can be used to express the detrimental radiation effect to a group of patients undergoing a radiologic or nuclear medicine procedure. The effective dose depends on the estimated absorbed dose to each organ and the relative radiation sensitivity of each organ. For most radiographic procedures, the field of view of the X-ray beam determines which organs are exposed to radiation. However, in nuclear medicine, the radiation exposure of each organ depends on the biodistribution and pharmacokinetics of the administered radiopharmaceutical. Based on models of the spatial relationships of individual organs and the organ-specific biokinetics of a radiopharmaceutical, estimated absorbed radiation doses can be determined for each organ including the critical organ. Then, estimates of tissuespecific radiation sensitivity are used to develop tissueweighting factors that are used to calculate the effective dose. These tissue-weighting factors are based on broad population averages across different age groups and gender, and, therefore, do not apply to any particular individual. In particular, the tissue-weighting factors may not represent those associated with children. Thus, effective dose should not be used to express the radiation burden to a single individual and cannot

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be used to determine the potential harm to any individual patient. During the past two decades, both theoretical models and experimental studies have been used in attempts to more accurately estimate radiation doses for children undergoing radiologic or nuclear medicine procedures. These have been promulgated in publications of the ICRP [5–7], as well as those of other organizations and individual investigators [14, 15]. The ICRP publications express the stochastic risk of radiation harm as organ-absorbed radiation dose (mGy/ MBq) and effective dose (mSv/MBq) per unit of administered activity and do not specify a particular administered activity for any radiopharmaceutical. Therefore, using information from these ICRP publications, an estimated effective dose can be calculated for nearly all radiopharmaceuticals and for any amount of administered activity. Calculation of effective dose in children is limited in a number of ways. Current tissue-weighting factors, the anatomical relationship of different organs and models of radiopharmaceutical biokinetics are not pediatric-specific. In children, the organspecific sensitivity to radiation exposure might be different than that in adults. As there is little published information regarding this, tissue-weighting factors based on adult averages are used for the calculation of estimated effective dose in children. In the ICRP publications, the information compiled is based on current anatomical models for adults, children and infants, and the estimated absorbed doses to the different organs are based on models that make assumptions about body size and the spatial relationships of different organs. The most commonly used anatomical models are those utilized by the ICRP and those based on anatomical phantoms developed by investigators at the Oak Ridge National Laboratories. However, adult models of body morphology may not reflect the spatial relationship of organs in children. Pediatric anatomical models have been developed to assist in more accurate radiation dose estimation in children [13], but have not been incorporated into most published tissue-weighting factors. Calculation of organ-absorbed doses relies on biokinetic models for each organ. The ICRP typically uses the same biokinetic models for all ages, as most data are from adults, with little pediatric-specific biokinetic data. In some circumstances, this may overestimate dose, as children may have more rapid clearance of radiopharmaceuticals. On the other hand, the standard dosimetry models may underestimate the dose for other pediatric studies. For example, these models do not account for uptake in the growth centers of the developing skeleton and so may underestimate the effective dose of bone agents in children with an immature skeleton [20]. Age-specific or disease-specific alteration in organ function can change the biokinetics of a radiopharmaceutical, and thus change radiation exposure. For example, the ICRP allows an adjustment for abnormal renal function or for unilateral ureteral blockage when calculating the absorbed radiation

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dose from renal imaging agents [6]. We have assumed normal renal function when calculating dose estimates. Infants with biliary atresia have an underdeveloped or absent gallbladder, so the gallbladder is unlikely to be the critical organ during performance of hepatobiliary scintigraphy in these children. Using effective dose to estimate pediatric radiation risk may not take into consideration the potentially higher risk of children at different ages. In its most recent report on the subject, the National Academy of Science recommended a linear-no-threshold model be used in evaluations of radiation risk [2]. Children may be at higher risk than adults for some adverse events from internal ionizing radiation. This may reflect greater radiosensitivity, the spatial relationship of organs in a child’s body, and a longer life span during which later effects can be realized [2, 3]. As estimates of effective dose do not apply to any particular individual, they should not be used to express the radiation burden or potential harm to an individual patient. Recognizing these factors reinforces the limitations of using effective dose for comparing the radiation risk of one age group to another group. Despite these constraints, effective dose remains most useful as a method for comparing the potential radiation effects of different medical imaging studies to children within a single age group. Until recently, the amount of a radiopharmaceutical administered to children of similar size might vary by as much as twenty-fold among different institutions [8]. Some of these differences may have reflected the imaging equipment available at each institution. Depending on age and design, gamma and PET cameras may demonstrate different levels of performance that might require adjustment of radiopharmaceutical administered activity. However, in the current era, it seems more likely that much of this variability represents a legacy of prior generations of imaging equipment [8]. Recognition of this variation in administered activities has led to national and international efforts to standardize pediatric radiopharmaceutical administered activities [9–11]. However, different approaches in developing and expressing these guidelines have led to substantial differences in recommended administered activities. For example, the EANM dosage card [9] assigns radiopharmaceuticals to three classes based on different patterns of pharmacokinetics. The North American consensus guidelines [10] provide recommended administered activities that are strictly weight-based (mCi/kg) for 10 of the 12 radiopharmaceuticals included in the guideline. As we have shown, there can be substantial differences in radiation exposure for the same procedure, depending which of these two guidelines is followed. In this study, we chose 12 common pediatric nuclear medicine procedures by identifying the radiopharmaceuticals that are included in both the EANM dosage card [9] and the North American consensus guidelines [10]. The North American guidelines include a smaller number of radiopharmaceuticals than are listed on the EANM dosage card, and so the selected procedures include all 12 of the procedures listed in the North

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American guidelines. For each radiopharmaceutical, the two guidelines were used to calculate the recommended administered activities for the nominal body weights of each of the five representative ages used in the ICRP publications. Our findings show that there can be substantial differences in radiation exposure for the same procedure, depending upon which of these two guidelines is followed. With a wide variation in the practice of pediatric nuclear medicine [8], guidelines such as those provided by the EANM [9] and the North American consensus group [10] can be of great value in encouraging lower radiation doses to children. This particularly can be true for departments that perform nuclear medicine procedures only occasionally in children. However, these two major guidelines have not been fully concordant. Radiation dose could vary substantially depending upon whether the EANM dosage card or the North American consensus guidelines is followed. Rather than suggesting a preference for either of the guidelines, these differences identified an opportunity to harmonize these recommendations, as well as other practice guidelines, with the aim of minimizing administered activities and radiation exposure to children. Based, in part, on these findings, substantial progress recently has been made toward harmonizing these two guidelines [21]. Identifying the lowest administered activity with which each pediatric nuclear medicine study can be performed as a diagnostic quality study will further the goal of minimizing radiation exposure to children, while maintaining the health benefits provided by nuclear medicine procedures.

Conclusion For commonly performed pediatric nuclear medicine studies, following either the EANM dosage card (version 1/5/2008) or the 2010 North American consensus guidelines for administered activities of radiopharmaceuticals can result in substantial differences in radiation exposure for the same procedure. This discordance has identified opportunities for harmonization of the guidelines, which may lead to further reduction in nuclear medicine radiation doses in children. Acknowledgments This work was presented in part at the International Pediatric Radiology (IPR) 6th Congress and Exhibition of the Joint Societies of Paediatric Radiology, May 2011, London, UK Conflicts of interest None

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Radiation doses for pediatric nuclear medicine studies: comparing the North American consensus guidelines and the pediatric dosage card of the European Association of Nuclear Medicine.

Estimated radiation dose is important for assessing and communicating the risks and benefits of pediatric nuclear medicine studies. Radiation dose dep...
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