Nuclear medicine practice and patient doses in New Zealand in

Nuclear medicine practice

K Beach

NRL R
2006/1eport
and patient dosesin New Zealand

in 2005

Nuclear medicine practice

and patient doses in New Zealand

in 2005

K Beach

National Radiation Laboratory Ministry of Health

PO Box 25099, Christchurch, New Zealand

© NRL, 2006

ISSN 1174-6483

National Radiation Laboratory Web site: http://www.nrl.moh.govt.nz

Contents

1 Introduction 1

2 Survey details 2

3 Data analysis 3

4 Historical trends 4

5 Variation in the types of procedures performed at each nuclear 7 medicine centre

6 Administered activities 9

7 Dose to the population 16

8 Comparison with other developed countries 18

9 Discussion and conclusions 21

Acknowledgements 23

References 24

Appendices

A: Covering letter and survey forms sent to the nuclear medicine 26 centres

B: Tabulated dosimetry data for nuclear medicine use in 31 New Zealand

C: Quantification of radiation risk arising from medical exposure to ionising radiation 38

1

1 Introduction

The National Radiation Laboratory (NRL)a has surveyed the use of radioactive materials in medicine in New Zealand each decade since 19661,2,3,4. The most recent survey was carried out in 2006 and used data on the diagnostic use of nuclear medicine collected nationally for the period January-December 2005. This report documents the findings of the most recent survey. Any diagnostic procedure involving the use of ionising radiation must be justified and performed in such a way as to obtain the necessary diagnostic information for the minimum practicable radiation dose (and hence minimum risk) to the patient, staff and public. In determining the minimum practicable radiation dose there will always be an element of uncertainty and judgement. Consequently, the principal aims of the survey were to: • assess trends in the frequency of different diagnostic nuclear medicine procedures

in comparison with previous national surveys; • assess the distribution by age group (age 0-4, age 5-9, age 10-14, age 15-19 and

adult) of different nuclear medicine procedures and compare with similar studies carried out elsewhere;

• determine the annual collective effective dose to the New Zealand population

from nuclear medicine and the relative contributions of the different procedures; • compare the mean activities of the administered radionuclides for some common

procedures with published reference levels and to allow for peer review; • compare practices and patient doses in New Zealand with those in other countries. NRL’s project team for this work comprised Karen Beach, Tony Cotterill, Glenn Stirling and John Laban.

a The NRL under a system of delegated authorities administers the New Zealand radiation protection legislation. Under the Radiation Protection Act 1965 persons using ionising radiation are required to be licensed and through a condition of their licence, users of radioactive materials in medical diagnosis must comply with NRL’s code of safe practice NRL C3 'unsealed radioactive material in medical diagnosis, therapy and research'. As part of its regulatory function NRL is charged with collecting data on practices and patient doses.

2

2 Survey details

The survey was designed to obtain and analyse information provided on: 1 the frequencies and types of procedures being performed; 2 the radiopharmaceuticals being used for each type of procedure; 3 the frequency of administrations and mean activity administered for each of the

age groups - child aged 0-4, child aged 5-9, child aged 10-14, child aged 15-19 and adult;

4 the methods used by nuclear medicine staff to determine the amount of activity to

be administered; 5 significant periods of 'down time' at the nuclear medicine centres. To obtain this information, each of the fourteen nuclear medicine centres in New Zealand were asked to answer two sets of questions on NRL-supplied forms. The first set related to such matters as the method used to determine the amount of activity to be administered. The second set asked for data on the frequency and mean activity administered for each of the age groups and for specified procedures. The forms were supplied to each facility both in hard copy and electronic formats. The list of procedures was taken from the Australian and New Zealand Society of Nuclear Medicine (ANZSNM)/Australasian Radiation Protection Society (ARPS) Table of Reference Activities for Nuclear Medicine5. The covering letter and forms sent to each facility are shown in Appendix A. Respondees were asked, if possible, to complete the forms electronically. This was to facilitate transfer of the data into an Excel spreadsheet, thereby minimising the possibility of transcription errors.

3

3 Data analysis

Each of the responses from the nuclear medicine centres were imported as separate worksheets in to a single spreadsheet. The supplied information was manipulated and dosimetric data applied to calculate effective doses (refer to section 7 for a discussion of this dose quantity). Calculations utilised the most recent data published by the International Commission on Radiological Protection (ICRP)6,7,8. Data that was entered manually at NRL was re-checked prior to importing it into the master spreadsheet. All data on the master spreadsheet and the formulae used within it were independently verified. A few of the centres were unable to provide detailed paediatric data as it was not easily accessible retrospectively. In some instances the centres were able to give a detailed breakdown for a procedure commonly carried out on paediatric patients, namely renal scans. In cases where detailed paediatric data was not provided it was assumed that all of the procedures were carried out on adults. This had minimum effect on the overall collective effective dose as the relative number of procedures treated in this way was not significant. Several of the centres provided data on procedures that were not included on the NRL-supplied list. This was not surprising as the nuclear medicine field is continually developing and the ANZSNM/ARPS Table of Reference Activities5 was produced about five years prior to the survey. The additional procedures were reconciled and added to the master list. A wide range of administered activities was reported for lung ventilation procedures using either Tc-99m DTPA or Tc-99m Technegas (eg, for Technegas this was 10-1500 MBq). The reason for these differences is that some centres reported an estimate of the activity absorbed by the patient whereas others provided the activity loaded into the nebuliser. For establishments providing data in terms of activity dispensed, the activity taken up by the patient was estimated to be 10% of the dispensed activity9. In some cases this may be an overestimate. Some centres reported administering I-131 activities in excess of 1 GBq for some procedures. It was identified that these scans were performed following a therapeutic administration and therefore the data was discounted from this study. The analysed data is presented either in tabular and/or graphic format in the following sections.

4

4 Historical trends

In this section the frequency of use of nuclear medicine investigations are summarised and compared against equivalent data from earlier surveys. The historical data used for comparisons in this section was obtained from NRL survey report4 for 1993 apart from the 2001 data which was obtained from the New Zealand branch of the ANZSNM10. Table 1 shows the number of total administrations and administrations per 1000 members of the New Zealand population (1000 population) for the years that have been surveyed. Table 1: Total annual administrations and administrations per 1000 population

Year 1966 1973 1983 1993 2000* 2005

Population (millions) 2.68 2.97 3.23 3.48 3.86 4.10 Number of diagnostic administrations

6164 17720 24113 29056 29600 26895

Number per 1000 2.3 6.0 7.5 8.4 7.7 6.6

* data obtained as part of this study is incomplete. Missing data has been estimated based on the 2005 survey data

It can be seen that the number of administrations per 1000 population in 2005 was lower than in previous surveys (excluding 1966) and has remained relatively static over the last 30 years. Table 2 shows the total annual numbers of the main types of procedures performed for the years that have been surveyed. Table 2: Total annual numbers of the main types of procedures performed

Number of procedures performed 1973 1983 1993 2000* 2005

Bone scans 1032 7126 14260 13973 13945 Cardiac (cardiovascular) 206 847 1653 593 Cardiac (myocardium) - 178 459

2616 3986

Renal 512 1787 2959 2860 2558 Lung 1373 2284 2617 2793 2063 Liver/spleen 2932 4407 298 71 82 GB + biliary - 51 277 259 341 Brain 4491 3762 878 564 57 Thyroid 5352 3031 2428 1857 1675 Gastro-intestinal - - - 497 229 Sentinel lymph node biopsy 53** 626

* data obtained as part of this study is incomplete; the number of procedures may be 10% higher. ** this value may include a small number of lymphangiograms.

5

Bone scans continue to be the most common nuclear medicine procedure, representing over 50% of the total. In fact, New Zealand has the highest contribution of bone scans to the total number of procedures of all developed countries listed in the 2000 United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) Report11. However, the number of bone scans in New Zealand amounts to about 3 per 1000 population which is consistent with data for other developed countries. The frequency of brain scans and liver tests have continued to fall as other techniques, namely computerised tomography (CT), magnetic resonance imaging (MRI) and ultrasound scanning, have taken over. The numbers of cardiovascular scans have also reduced significantly over the past twelve years for similar reasons. In contrast, the numbers of myocardial perfusion studies have increased almost ten-fold since 1993, and now amounts to about 15% of the total number of procedures performed. The use of nanocolloid labelled Tc-99m for sentinel lymph node biopsy has not been reported in previous NRL studies. This is a relatively new procedure which is already being performed at a number of clinical sites. It is expected that the number of these procedures will increase significantly over the next few years. The use of positron emitting radionuclides for diagnostic procedures commenced in early 2006 at two of the nuclear medicine centres. It is envisaged that several other centres will be able to provide this service within the next five to ten years. Data on this type of procedure will therefore be collected as part of the next NRL survey. Paediatric data was collected as part of the 1993 study and it has therefore been possible to compare the numbers of the main types of procedures performed with data from the 2005 study. This is given in Table 3 below. From this data it can be seen that the number of paediatric bone scans has reduced significantly since 1993, particularly in the 10-14 and 15-19 age groups, whereas the number of renal studies has remained constant. There has also been a reduction in the number of other procedures carried out such as cardiac studies, lung studies and thyroid scans. Table 3: Total annual numbers of paediatric procedures performed

Number of procedures performed 0-4 years 5-9 years 10-14 years 15-19 years

1993 2005 1993 2005 1993 2005 1993 2005 Bone 146 190 256 202 554 285 694 425

Cardiac 0 1 0 3 12 2 18 4

Lung 0 11 6 15 12 15 73 6

Renal 560 600 274 355 91 155 97 98

Thyroid 12 31 6 0 24 7 61 26

For comparative purposes the paediatric data has been normalised with the population data for the relevant age group and is shown graphically for the two main types of procedure, bone scans and renal studies in Figure 1. About 50% of all renal studies are carried out on patients aged 0-15 years which is significantly higher than in other countries11. This is believed to be because renal studies on adults have recently tended towards the use of CT and ultrasound techniques rather than the use of nuclear medicine. In contrast, when the relatively high prevalence of urinary infections is considered alongside the usefulness of nuclear medicine in the diagnosis of urological problems in paediatric patients, it is not surprising that there are relatively high numbers of renal scans in the paediatric age groups. Figure 1: Number of paediatric procedures shown by age group

Bone

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0-4 5-9

No

of p

roce

dure

s pe

r 100

0po

pula

tion

(in a

ge g

roup

)

scans

10-14 15-19

Age Group

1993 2005

Renal studies

0.0

0.5

1.0

1.5

2.0

2.5

0-4 5-9 10-14 15-19

Age Group

No

of p

roce

dure

s pe

r 100

0po

pula

tion

(in a

ge g

roup

)

1993 2005

6

5 Variation in the types of procedures performed at each nuclear medicine centre

In this section the relative numbers of the main types of procedures carried out at the fourteen nuclear medicine centres have been compared. The data has been normalised using the total number of procedures performed at each centre and is shown in Figure 2. Figure 2: Percentage of total procedures for each centre

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Nuclear Medicine Centre

% o

f Tot

al A

dmin

istr

atio

ns

Bone Scan Cardiac (cardiovascular) Cardiac (Myocardium) Renal

Lung Liver/spleen GB + biliary Brain

Thyroid GI Tract Other

It can be seen from Figure 2 that the most frequent procedure carried out at each of the centres is a bone scan. However, the percentage contribution to the total number of procedures ranges from 40% to more than 80%.

7

8

The number of cardiac studies carried out by each of the centres varies significantly, with one centre not carrying out any cardiac studies and another centre having cardiac studies contributing more than 40% to its total workload. This variation in different types of studies is consistent with that previously reported10. The variation between centres is due to a number of factors. These include the functional capability (some types of procedure require more specialist knowledge and equipment) and the preferences of referring specialists, some of whom use other diagnostic images procedures, eg, ultrasound or CT scans.

9

6 Administered activities Reference levels for administered activities of radiopharmaceuticals have been published in the International Atomic Energy Agency’s (IAEA) Basic Safety Standards (BSS)12. The reference activity is defined as the activity that should normally be administered to a 70 kg adult. Also, NRL’s Code of Safe Practice NRL C313 provides a table of reference activities. In 1998 a Working Party was jointly established by the ANZSNM and the ARPS to develop diagnostic Reference Levels for Nuclear Medicine in Australia and New Zealand5. In addition to adult reference activities, ANZSNM/ARPS has also produced reference levels for paediatric procedures14. Each of the nuclear medicine centres indicated that they use reference levels based on a 70 kg patient. For large or small patients the activity administered may be increased or decreased. However, the basis of these reference levels varies from centre to centre. In general they are based on the previously mentioned guidelines, used in addition to literature supplied by the pharmaceutical companies and information published elsewhere, eg, the UK Administration of Radioactive Substances Advisory Committee Guidance Notes15. Table 4 provides a comparison of the mean and the range of activities administered to patients aged 20 and over (ie, adults) during 2005, with the BSS, NRL C3 and ANZSNM/ARPS reference levels. Overall the mean activity administered is consistent with the reference levels. However, the range of activities administered for some procedures is significant. For illustrative purposes some of this data is shown as a series of histograms in Figure 3 for several common procedures. Generally, the maximum and minimum administrations are appreciably different from the mean. This range of administrations is attributable to a number of factors. Different centres base their reference levels on different sets of published data and there is likely to be variation in the techniques used and in the technical specification of the detectors, eg, counting efficiency. The administered activity also varies by at least 10-20% for obese or petite patients. The mean activity administered has been compared with the results from the 1993 survey. These are summarised in Table 5. Generally the activities are similar, indicating that procedures have generally become standardised in line with the reference levels. From Table 4 it can be seen that there is a wide range of administered activities for GFR procedures using Tc-99m. This is because two different types of procedure have actually been reported – the use of DTPA for a renogram which typically requires an activity of up to about 200 MBq and the use of DTPA for an in vivo GFR measurement which typically requires an activity of about 10 MBq.

Table 4: Comparison of mean activities administered for patients aged 20 and over against NRL C3 reference activities, ANZSNM/ARPS Reference Activities and BSS Guidance Activities

Procedure description Radionuclide Pharmaceutical Mean activity administered (MBq)

Range of activities administered (MBq)

NRL C3 reference activities (MBq) (planar)

ANZSNM/ARPS reference activities (MBq)

BSS guidance activity (MBq)

(planar/spect)

Bone scan Brain Brain Cardiac GHPS Cardiac first pass Cardiac R/L shunt GIT blood loss GIT colonic transit GIT gastric emptying Hepatobiliary Infection Infection Liver blood flow Liver/spleen Lung perfusion Lung ventilation Lymphoscintigraphy – melanoma Lymphoscintigraphy – breast Ca Meckel’s diverticulum Myocardial perfusion-rest Myocardial perfusion–2 day stress/rest(rest)

Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Ga-67 Tc-99m Tc-99m Tc-99m Ga-67 Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tl-201 Tc-99m

MDP or HDP DTPA HMPAO RBCs RBCs MAA RBCs citrate colloid HIDA/EHIDA/DISIDA/Disofenin WBC-colloid citrate RBCs colloid MAA Technegas nanocolloid nanocolloid pertechnetate chloride mibi

751 740 661 670 550 150 656

8 29

126 501 155 680 125 134

41 45 52

300 183 743

700-825 740-740 500-754 450-800 550-550 150-150 450-894

4-20 19-50

100-210 233-600 141-180 400-773

72-150 40-220 10-150

30-80 26-100

158-370 120-208 600-792

750 700 750

- - - - - -

150 -

150 -

150 200

- - -

300 - -

900 800 800

1000 925 185

1000 40 40

200 740 200

1000 200 200

- 80 80

400 120 750

600/800 500/800

500 800 800

- 400

- 40

150 -

300 -

80/200 160/200

- - -

400 100 600

Procedure description Radionuclide Pharmaceutical Mean activity administered (MBq)


NRL C3 reference activities (MBq) (planar)

ANZSNM/ARPS reference activities (MBq)

BSS guidance activity (MBq)

(planar/spect)

Myocardial perfusion -2 day stress/rest(stress)Myocardial perfusion -2 day rest/stress(stress)Myocardial perfusion -1 day rest/stress (rest) Myocardial perfusion -1 day rest/stress(stress)Parathyroid Renal scan Renal scan Renal scan Renal transplant Salivary glands Somatostatin receptors Spleen Testicular scan Thyroid Thyroid-WB scan for Ca Tumour Tumour Tumour Tumour Tumour GFR GFR Red cell volume

Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m TC-99m In-111 Tc-99m Tc-99m Tc-99m I-131 Tl-201 Ga-67 I-131 I-123 Tc-99m Tc-99m Cr-51 Cr-51

mibi mibi mibi mibi mibi DTPA DMSA MAG3 DTPA pertechnetate octreotide RBCs-damaged pertechnetate pertechnetate iodine chloride citrate MIBG MIBG mibi DTPA EDTA RBCs

739 1100

402 1082

730 320 127 221 297 110 185 200 172 123

43 140 204

27 171 685 136

4 1

600-778 1100-1100

370-440 949-1100

550-925 150-410

65-200 180-400 290-450 110-110 117-280 200-200 172-172

78-200 23-207

140-140 140-370

25-28 157-200 550-753

3-227 3-7

0.4-5

- - - - - -

150 200

- - - - -

150 - - - - - -

300 3 2

750 - -

1000 800 500 185 350 400 300 200 400 600 200 200 160 400

37 370 800 110

8 4

600 600 300 600 600

- 160 100 350

- -

100 -

200 -

100 300

- - - - - -

Figure 3: Variation in administered activities

Bone scans

0

500

1000

1500

2000

2500

3000

701- 710

711- 720

721- 730

731-740

741- 750

751- 760

761- 770

771-780

781-790

791-800

801-810

811-820

821-830


Mean = 751 MBq

No

of p

roce

dure

s

Renal Scans using DTPA

0

50

100

150

200

250

126- 150

151- 175

176- 200

201-225

226- 250

251- 275

276-300

301-325

326-350

351-375

376-400

401-425


Mean = 320 MBq

No

of p

roce

dure

s

Parathyroid studies

0 10 20 30 40 50 60 70 80

501-550 551-600 601-650 651-700 701-750 751-800 801-850 851-900 901-950Range of activities administered (MBq)

Mean = 730 MBq

No

of p

roce

dure

s

12

13

Table 5: Trends in mean administered activity adults

Mean Administered Activity (MBq) Procedure

1993 2005

Bone scan (MDP/HDP) 699 751

Brain (DTPA) 744 740

Brain (HMPAO) 705 661

Cardiac GHPS/first pass 586 670 / 550

GIT blood loss (RBCs) 603 656

GIT gastric emptying (colloids) 34 29

Hepatobiliary (HIDA/EHIDA/DISIDA/Disofenin)

116 126

Infection (citrate) 110 155

Liver/spleen (colloid) 198 125

Lung perfusion (MAA) 144 134

Meckel’s diverticulum 307 300

Renal scan (DTPA) 354 320

Renal scan (DMSA) 98 127

Renal scan (MAG3) 228 221

Thyroid (pertechnetate) 190 123

GFR (DTPA) 222 136

GFR (EDTA) 3 4

Red cell volume (RBCs) 2 1 There is a relatively wide range of mean administered activities for the main paediatric procedures. These are shown in Table 6a. This is to be expected due to the small number of procedures performed and the relatively wide age and weight range within each group. The activity to be administered to paediatric patients is generally calculated individually based on a fraction of the adult activity for each centre, which is determined by the weight and/or age of the patient. The European Association Nuclear Medicine (EANM) paediatric task force reference minimum16 and the ANZSNM/ARPS reference minimum (Amin) and maximum (Amax) activities for administration to paediatrics14 are also shown in Table 6a. In some instances the activity administered to infants was found to be below the ANZSNM/ARPS reference minimum activity. The mean effective doses received by paediatric patients have been calculated based on the mean activities administered given in Table 6a (see Section 7 for the radiation dose calculation methodology used). These are given in Table 6b. It should be noted that although the effective dose to paediatric patients is similar to that to adults the overall risk will be higher due to the application of the age correction re-normalisation factors for radiation risk17. These vary from 3.0 at age 1 to 1.5 at age 15 (see Appendix C).

Table 6a: Comparison of mean activities administered for paediatric patients

Mean activity administered (MBq) (Range shown in brackets)

Procedure description

Radionuclide Pharmaceutical EANMRef Amin (MBq)

ANZSNM/ARPS Ref Amin (MBq)

ANZSNM/ARPS Ref Amax(MBq)

Age 0-4 years Age 5-9 years Age 10-14 years Age 15-19 years

Bone scan Lung perfusion Meckel’s diverticulum Renal scan Renal scan Renal scan GFR GFR

Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Cr-51

MDP or HDP MAA pertechnetate DTPA DMSA MAG3 DTPA EDTA

40 10 -

20 15 15 - -

70 20 40 50 35 30 - -

750 150 400 370 130 180

- -

139 (116-257) 29 (15-70) 59 (25-100) 52 (23-127) 33 (23-65) 41 (22-116) 21 (12-66) 1 (1-4)

259 (220-521) 39 (25-89) 128 (40-180) 103 (56-247) 56 (39-110) 84 (64-200) 20 (14-117) 2 (2-4)

536 (431-717) 45 (20-73) 161 (68-220) 156 (90-251) 90 (59-150) 145 (79-300) 22 (2-167) 2 (2-4)

674 (581-844) 50 (30-70) 269 (150-390) 255 (201 -432) 113 (85-173) 199 (157-320) 35 (1-192) 3 (3-4)

Table 6b: Comparison of mean effective doses received by paediatric patients

Mean radiation dose per procedure (mSv) Procedure

description Radionuclide Pharmaceutical Mean adult

radiation dose (mSv) Age 0-4 years Age 5-9 years Age 10-14 years Age 15-19 years

Bone scan Lung perfusion Meckel’s diverticulum Renal scan Renal scan Renal scan GFR GFR

Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Cr-51

MDP or HDP MAA pertechnetate DTPA DMSA MAG3 DTPA EDTA

4.3 1.5 3.9 1.6 1.1 1.5 0.7

0.008

3.8 1.8 4.7 0.8 1.2 0.9 0.3

0.008

3.6 1.3 5.4 0.9 1.2 1.0 0.2

0.007

5.9 1.0 4.2 1.3 1.4 1.7 0.2

0.007

4.7 0.8 4.6 1.6 1.2 1.8 0.2

0.008

Several different methods have been reported as being used to determine the fraction of the adult activity to be administered to a paediatric patient. The main ones used are the EANM paediatric task force protocol16, the use of a nomogram18 and also direct scaling as a fraction of the standard adult 70 kg weight. These are compared in Figure 4. From the graph it can be seen that paediatric administrations could vary by up to 10-100% at different centres depending on the method used to assess the fraction of the adult activity. The variation in the fraction administered is highest for infants and reduces as the patient weight increases. These variations are of significance, particularly when considered alongside the increased radiation risk factors for paediatric patients. Figure 4: Fractional activity administered to children

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 7

Weight (kg)

Frac

tion

of a

dult

adm

inis

tere

d ac

tivity

0

EANM proportion of standard adult `70 kg' weightnomogram - bone nomogram - renal DMSAmean

15

16

7 Dose to the population

Any administration of a radiopharmaceutical to a patient delivers a certain radiation dose to that patient. The magnitude of the radiation dose depends on the radionuclide used, the pharmaceutical used and the activity administered. For a given radiopharmaceutical, various organs in a patient’s body will be irradiated in differing proportions as a result of the biological distribution and kinetics of the particular pharmaceutical. In order to be able to make meaningful comparisons of radiation dose between different procedures in which different organs are irradiated, a quantity known as effective dose has been defined. Effective dose converts a distribution of known radiation doses to individual organs into an equivalent uniform whole body radiation dose presenting the same overall risk. In this way, for example, the risk to a patient undergoing a lung ventilation study can be compared to the risk due to exposure to x-rays in the course of a CT examination. It should be noted that the risk-based weighting factors strictly only apply to normal healthy adults, so the extension to medical patients of all ages has limitations. However, it is generally considered that effective dose is useful as an index for comparison of risks between different modalities using ionising radiation, but should be treated with care. The unit of effective dose is the Sievert (Sv). Collective effective dose takes account of the group of persons exposed to radiation. It is obtained by multiplying the number of exposed persons by the mean radiation dose they received. The unit of collective effective dose is the man Sievert (man Sv). Care should be taken when using this measure of dose. Collective dose is a quantity designed for optimisation and is not suitable for use in epidemiologic risk assessment and is therefore inappropriate to use in risk projections based on epidemiological studies (ie, the calculation of cancer deaths based on small exposures to large populations is not a reasonable application). Effective dose data for the range of nuclear medicine procedures currently carried out in New Zealand have been obtained from ICRP publications6,7,8. These effective dose data have been applied to the results of this survey to calculate the effective dose per administration and the collective effective dose for each of the procedures. The results are provided in Appendix B for each of the patient age groups. For non-thyroid studies using pertechnetate, it has been assumed that a thyroid-blocking agent has not been used. A summary of the collective effective doses and the mean effective doses per examination for the main examination types are given in Table 7 below. The total collective effective dose for all diagnostic procedures carried out during 2005 amounted to 100 man Sv (see Table 7). A collective effective dose of 100 man Sv for the population equates to a mean effective dose of 25 µSv per capita per annum. As a comparison, the effective dose from all

17

sources of naturally occurring radiation is approximately 1.8 mSv per capita per annum in New Zealand19. Table 7: Summary of collective effective doses from the main nuclear medicine procedures and summary of mean effective dose per administration for some main examinations Collective effective doses Effective doses per mean administration (adult) Main procedure type Collective

effective dose

(man Sv)

Examination Effective dose (mSv)

Bone scans Cardiac Renal Lungs Liver Brain Thyroid Gastrointestinal Other

60

27

2.7

2.2

0.3

0.3

2.7

0.6

4.9 TOTAL 100

Bone scan – HDP Gated cardiac – RBC Myocardium – MIBI Renal – DTPA Renal – DMSA Lung perfusion – MAA Lung Ventilation - DTPA Liver – tin colloid Brain scan DTPA Thyroid scan – TcO4 Biliary – IDA GI bleeding - RBC

4.3

4.7 6.6 1.6 1.1 1.5 0.6 1.2

3.6

1.6

2.1 4.6

In terms of effective dose to the population from all man-made sources, the effective dose from nuclear medicine represents a relatively small contribution, of the order of about 5%. The mean effective dose per procedure for adults and paediatric patients is 3.8 mSv and 2.8 mSv respectively. The calculation of effective dose and the associated risk factors are all based on an average population. For a given radiation dose, the risk to an individual is higher than the average if the radiation dose is received in childhood and it is lower than the average if received in later life17. Appropriate risk factors to use in the quantification of radiation risk are given in Appendix C. For nuclear medicine the major contribution to collective dose is from bone scans, of which a proportion are carried out on elderly patients, a significant proportion of whom will have on average reduced life expectancies. Consequently, the overall risk arising from collective dose will be proportionately lower than would be calculated using the ICRP nominal risk coefficients20.

18

8 Comparison with other developed countries

In this section the frequency of nuclear medicine use, and the mean activities for some common procedures are compared with practices in other developed countries. Table 8 shows a comparison of New Zealand’s diagnostic nuclear medicine administrations per 1000 population with some other developed countries. The majority of the information currently available is taken from the latest UNSCEAR report11 which provides data for the period 1991-1996. Several countries have also independently reported relevant data in the previous five years and this is also provided in Table 8. Although the data for 2005 is limited, it can be reasonably concluded that the frequency of diagnostic nuclear medicine administrations in New Zealand is relatively low when compared with other countries. As Positron Emission Tomography (PET) scans only generally amount to less than 1% of the total number of procedures in countries that use PET, this does not account for the relatively low frequency of nuclear medicine procedures in New Zealand. Table 8: Comparison of examination (administration) rates with other developed countries

Examinations per 1000 Country

1991-1996 2000-2005

Argentina 11.1 -

Australia 12.0 -

Canada 64.6 -

Czech Republic 28.3 -

Denmark 15.2 -

Germany 34.1 4721

Italy 11.0 -

Japan 11.7 -

Netherlands 11.6 -

New Zealand 8.4 6.6

Romania 3.0 -

Sweden 13.6 11.622

United Kingdom 8.2 10.823

USA 31.5 -

19

Table 9 shows a comparison of the annual per capita effective dose received by the population of New Zealand with a number of other developed countries. The majority of the information currently available is in the latest UNSCEAR report11. Although the data for 2005 is limited, it can be reasonably concluded that the annual per capita effective dose from diagnostic nuclear medicine administrations in New Zealand is also relatively low when compared with other countries. Table 9: Comparison of annual per capita effective dose (µSv) with other developed countries

Annual per capita effective dose (µSv) Country

1991-1996 2000-2005

Australia 64 -

Canada 160 -

Germany 100 12021

Netherlands 67 -

New Zealand 26 25

Romania 49 -

United Kingdom 36 3023

USA 140 - Table 10 provides a comparison of the mean activities administered in New Zealand for some common examinations with those from other developed countries. It can be seen that the mean activity administered for these procedures is consistent with those reported by other countries. There is limited data available from other developed countries with respect to the use of nuclear medicine specifically on paediatric patients. The available data is given in Table 11. For comparative purposes the New Zealand paediatric data covers the age range 0-14 years, rather than age 0-20 years as reported earlier in this report. The number of paediatric administrations expressed as a percentage of the total number of administrations is comparable with those reported by other countries. Similarly, the mean effective dose per administration is of a comparable magnitude. Although the main types of procedures performed by each country are the same, there is a noticeable variation in the percentage numbers of these procedures performed. Renal studies, however, are the most common type of paediatric procedure for all of the countries reported.

Table 10: Comparison of mean radionuclide activities (in MBq) administered to adult patients during 2005 for some common examinations with mean activities administered in other developed countries (data taken from UNSCEAR report11 unless referenced otherwise)

Bone Brain Cardiovascular Liver/spleen Lung RenalCountry

phosphates HMPAO MIBI colloid MAA DMSA DTPA MAG3Canada 925 740 600 111 185 - 400 -

Czech Republic 730 740 680 148 188 188 250 -

Denmark 637 667 615 83 112 - 165 92

Germany21 616 584 949 114 142 57 53 81

Italy 630 720 600 150 150 148 148 -

Japan - 787 - - - 197 377 -

Netherlands - 500 650 80 100 - - 80

New Zealand 751 661 810 125 134 127 320 221

Romania - - - 140 125 - 300 -

Sweden22 528 940 629 163 121 45 107 96

United Kingdom23 598 - 414 98 89 77 203 89

Table 11: Comparison of paediatric nuclear medicine with other countries

Percentage of procedures on paediatric patients compared to total population

Breakdown of main types of procedure (expressed as a percentage of the total)

Country

by number of administrations

by collective effective dose

Mean effective dose per

administration (mSv) Bone Renal Thyroid

Czech Republic (age <18 years)24 7.5% 5.1% 2.9 17% 64% 3%Germany (age <15 years) 21 3.3% 2.1% 1.9 20% 60% 4%Iran (age <15 years)25 5.3% 4.0% 3.8 27% 38% 27%New Zealand (age <15 years) 7.3% 4.7% 2.4 35% 57% 2% Sweden (<15 years) 22 5.4% - - 11% 60% 0.2%

21

9 Discussion and conclusions

The use of nuclear medicine as a diagnostic tool has reduced in the decade since 1993 with the number of administrations decreasing by 21% from 8.4 per 1000 population per annum in 1993 to 6.6 per 1000 population per annum in 2005. This reduction is believed to be mainly due to competition from other imaging modalities such as CT, MRI and ultrasound. However, there has also been a significant increase in the numbers of myocardial perfusion scans and sentinel lymph node biopsies performed since 1993. Bone scans remain the most commonly performed procedure representing 52% of the total number of procedures carried out in 2005. Although the total number of bone scans carried out has remained approximately constant, the number of bone scans performed on paediatric patients has reduced significantly (by approximately 33%) from 1650 in 1993 to 1102 in 2005. The numbers of other types of procedures carried out on paediatric patients have, however, remained constant. There is a significant variation in the numbers of different types of procedure carried out at each of the nuclear medicine centres. For example, one centre does not carry out any cardiac studies whereas the significant workload of another centre is due to cardiac studies (more than 40%). This is due to a number of factors including differences in the functional capability and the types of specialists associated with the different centres and the preferred diagnostic techniques of referring specialists. The mean activities of radionuclides administered for some common examinations have been compared with practices in other developed countries. Overall, New Zealand practice is in line with the rest of the developed world. The mean activities of radionuclides administered for adults for some common examinations have been compared with those published in NRL C313, ANZSNM/ARPS5 reference activities and guidance levels of activity in the 1996 IAEA BSS publication12. There is reasonable consistency with the activity levels given in these publications. The mean activity administered to adults for the common examinations has largely remained unchanged in the last decade although there are significant variations between different centres. Compared to the adult data there is a much wider range of mean administered activities for the common paediatric procedures. This is largely due to variations between centres in the methods employed to calculate the paediatric activity as a fraction of the adult activity. This can account for a variation in the administered activity of up to 100%. The minimum administered activity in some instances was found to be below the ANZSNM/ARPS minimum reference activity. The mean effective dose received by paediatric patients was found in some cases to be higher than the comparable effective dose received by adults. For bone scans, the mean effective dose received by the age group 10-14 years was found to be nearly 40%

22

greater than the mean effective dose received by adults. This is compounded by the higher risk factors for the paediatric age group. The average effective dose per capita to the population from the administration of radiopharmaceuticals for diagnostic purposes was found to be approximately 25 µSv per annum, which is comparable to the 1993 survey (26 µSv per annum). The mean effective dose per capita is relatively low when compared with other countries with comparable effective doses ranging from 30 µSv to 160 µSv. It also tends to be higher in countries which perform significant numbers of myocardial perfusion studies, especially if Tl-201 is used instead of Tc-99m (the mean effective dose per study is approximately 7 mSv using Tc-99m and about 20 mSv using Tl-201). Although there is limited data available from other countries with respect to the use of nuclear medicine procedures on paediatric patients the data obtained from this survey is comparable to that reported.

23

Acknowledgements

This survey would not have been possible without the co-operation of the staff from the following nuclear medicine centres who completed the nuclear medicine questionnaires:

Auckland Hospital Auckland Radiology Group Christchurch Hospital Dunedin Hospital Fulford Radiology Services Hawkes Bay District Health Board New Zealand Medical Imaging, Auckland New Zealand Medical Imaging, Hamilton Pacific Radiology Palmerston North Hospital Southland Waikato Hospital Wairau Hospital Wellington Hospital

Kevin Smidt and Peter Gene, Palmerston North Hospital, for reviewing and providing comments on the nuclear medicine questionnaires. Kevin Smidt for clarifying medical related queries arising during the drafting of the report and for commenting on the draft report. John Turner and Darin O’Keeffe, Christchurch Hospital for reviewing the draft report.

24

References

1 McEwan A.C. Unsealed radioisotopes in medical practice in New Zealand. Christchurch: National Radiation Laboratory, 1967 NRL/PDS/1967.

2 McEwan A.C. Unsealed radioactive materials in medical practice in New

Zealand. NZ Medical Journal 82:163-168. 1975. 3 McEwan A.C. and Smyth V.G. Survey of radiopharmaceuticals used for in vivo

studies in medical practice in New Zealand. Christchurch: National Radiation Laboratory, 1984 NRL report 1984/2.

4 Laban J.A. and Smyth V.G. Survey of the use of Nuclear Medicine in New

Zealand. Christchurch: National Radiation Laboratory, 1999 NRL report 1999/1.

5 Smart R.C. and Towson J.E. Diagnostic reference activities for nuclear

medicine procedures in Australia and New Zealand. ANZ Nuclear Medicine 31(1) 23-30.

6 International Commission on Radiological Protection. Radiation dose to patients

from radiopharmaceuticals. Oxford: ICRP, 1987. ICRP publication 53. 7 International Commission on Radiological Protection. Radiological protection in

biomedical research. Oxford: ICRP, 1993. ICRP publication 62. 8 International Commission on Radiological Protection. Radiation dose to patients

from radiopharmaceuticals. Oxford: ICRP, 1998. ICRP publication 80. 9 Early P.J. and Sodee D.B. Principles and practice of nuclear medicine. St Louis:

C V Mosby Co., 1985. 10 Private communication with K. Smidt. New Zealand Nuclear Medicine

Benchmark Study 2001 presented by Kevin Smidt at the NZ Branch ANZSNM Meeting in 2002.

11 UNSCEAR 2000 Report to the General Assembly: Sources and effects of

Ionizing Radiation Volume 1: Sources. 12 International Atomic Energy Agency. International basic safety standards for

protection against ionizing radiation and for the safety of radiation sources. Vienna: IAEA, 1996. Safety series No. 115.

25

13 National Radiation Laboratory. Code of safe practice for the use of unsealed radioactive materials in medical diagnosis, therapy and research. Christchurch: National Radiation Laboratory, 1994. NRL C3.

14 Towson J.E., Smart R.C. and Rossleigh M.A. Radiopharmaceutical activities

administered for paediatric nuclear medicine procedures in Australia. ANZ Nuclear Medicine 32(1) 15-23.

15 Administration of Radioactive Substances Advisory Committee. Notes for

guidance on the clinical administration of radiopharmaceuticals and use of sealed radioactive sources, 1998 (updated in March 2006).

16 Piepsz A., Hahn K., Roca I., Ciofetta G., Toth G., Gordon I., Kolinska J. and

Gwidlet J. A radiopharmaceutical schedule for imaging in paediatrics. European Journal of Nuclear Medicine 1990 17:127-129.

17 International Commission on Radiological Protection ICRP Committee 3,

Minutes of the Wützberg Meeting, September 1995. 18 Private communication with M. Ellwood (Wairau Hospital) and L. Murray

(Christchurch Hospital). 19 Robertson M.K., Randle M.W. and Tucker L.J. Natural radiation in New

Zealand houses. Christchurch: National Radiation Laboratory, 1988. NRL Report 1988/6.

20 International Commission on Radiological Protection. 1990 Recommendations

of the International Commission on Radiological Protection. Oxford: ICRP, 1991. ICRP publication 60.

21 Stamm-Meyer A., Noβke D., Schnell-Inderst P., Hacker M., Hahn K. and Brix

G. Radiation exposure of patients undergoing nuclear medicine procedures in Germany between 1996 and 2000. Nuklearmedizin 2005 44 (119-130).

22 Jönsson H. and Richter S. Isotopstatistik 2003 – för nukleärmedicinsk

verksamhet. Swedish Radiation Protection Authority, 2004. SSI report 2004:16. 23 Hart D. and Wall B.F. A Survey of nuclear medicine in the UK in 2003/04.

Health Protection Agency, 2005. HPA-RPD-003. 24 Hušák V., Petrová K., Prouza Z. and Mysliveček. Medical radiation exposure of

the Czech Republic paediatric population due to diagnostic nuclear medicine. Nuclear Medicine Review 2000 3(2) (143-147).

25 Neshandar A., Tabeie F. Pediatric Radiation Exposure from Diagnostic Nuclear

Medicine Examinations in Tehran. Iran. J. Radiol. 3(1)( 35-39).

26

Appendices

A: Covering letter and survey forms sent to the nuclear medicine centres

21 March 2006 See distribution Study of the Use of Nuclear Medicine in New Zealand 2005 During the course of 2006 NRL will be carrying out a study of the use of Nuclear Medicine in New Zealand based on data obtained from 2005. This will update the previous survey data collected in 1993. The information collected will be for the use of Nuclear Medicine for diagnostic purposes only. The aims of the study are:

• to assess trends in the frequency of different nuclear medicine procedures in comparison with previous national surveys

• to assess the distribution by age group (child aged 0-4, child aged 5-9, child

aged 10-14, child aged 15-19 and adult) of different nuclear medicine procedures

• to determine the annual effective dose to the NZ population from nuclear

medicine and the relative contributions of the different procedures

• compare the frequency of nuclear medicine use and the average activities of the radionuclide administered for some common procedures compared with other developed countries.

It would therefore be appreciated if you could complete the attached questionnaires (Part A and Part B) and return them to NRL at the earliest opportunity and no later than 31st May 2006. Part A of the questionnaire comprises as a small number of questions relating to procedures used within your nuclear medicine department. It can be forwarded to NRL as a Word attachment to an e-mail to [email protected]. or as a printed out hard copy.

27

Part B requests data relating to the total number of administrations from 1 January 2005 to 31 December 2005 for each procedure and age group and the mean activity administered. In the event of a procedure not being listed, please feel free to add additional rows of data. The data should relate to the number of administrations relating to diagnostic procedures only. It would be appreciated, though, if you could give as much information as possible to enable the procedure to be compared with those used at other centres. It would be appreciated, if possible if Part B was forwarded to NRL as an Excel attachment to an e-mail to [email protected]. This will help to reduce transcription errors when entering the data into our database. However, if it is not possible to provide the data in this format a print out filled in is acceptable. Yours sincerely Karen Beach Health Physicist Encl: NRL Nuclear Medicine Study 2005 Questionnaire Parts A and B <Distribution>

28

NRL NUCLEAR MEDICINE STUDY 2005

QUESTIONNAIRE PART A

Name of Hospital

Name and position of person completing the questionnaires

Q1. Please describe the method used to assess the amount of activity to be administered for a particular procedure to an adult. A.

Q2. Please describe the method used to assess the amount of activity to be administered for a particular procedure to a child. A. Q3. Are there any reasons why the data provided in Part B of the questionnaire is atypical for a typical year’s activity, e.g. equipment inoperable for a number of months etc? Please provide details. A. Q4. If there is any other information which you would like to provide with respect to the data entered in Part B of the questionnaire please enter it below. A.

B: Tabulated dosimetry data for nuclear medicine use in New Zealand Table B.1: Data for child aged 0-4 years Procedure description Radionuclide Pharmaceutical Number of

administrationsMean activity administered

(MBq)

Effective dose per unit activity

(mSv/MBq)

Collective effective dose for

2005 (mSv) Arterial infusion Bone scan GIT oesoph reflux “milk scan” Hepatobiliary Lung perfusion Meckels’ diverticulum Myocardial hot spot Renal scan Renal scan Renal scan Thyroid Tumour Tumour GFR GFR Mucociliary Flow Studies

Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m I-131 I-123 Tc-99m Cr-51 Tc-99m

MAA MDP or HDP colloid HIDA/EHIDA/DISIDA/DisofeninMAA pertechnetate PYP DTPA DMSA MAG3 pertechnetate MIBG MIBG DTPA EDTA colloid

1 190

3 17 11

8 1

90 346 141

31 1 6 6

17 10

30 139

20 35 29 59 47 52 33 41 21 18

117 21

1 4

6.3E-02 2.7E-02 1.4E-01 1.0E-01 6.3E-02 7.9E-02 2.7E-02 1.6E-02 3.7E-02 2.2E-02 7.9E-02

- 6.8E-02 1.6E-02 7.1E-03

-

2 714

9 60 20 37

1 75

421 128

51 -

48 2

0.1 -

Table B.2: Data for child aged 5-9 years Procedure description Radionuclide Pharmaceutical Number of


(MBq)


(mSv/MBq)


2005 (mSv) Arterial infusion Bone scan GIT blood loss Lung perfusion Lung ventilation Meckel’s diverticulum Myocardial hot spot Myocardial perfusion – 2 day stress/rest (rest) Myocardial perfusion – 2 day stress/rest (stress) Renal scan Renal scan Renal scan Renal transplant Tumour GFR GFR

Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m I-123 Tc-99m Cr-51

MAA MDP or HDP RBCs MAA Technegas pertechnetate PYP mibi mibi DTPA DMSA MAG3 DTPA MIBG DTPA EDTA

2 202

1 12

3 9 1 1 1

92 179

33 1 1

31 19

57 259 150

39 2

128 133 365 414 103

56 84

100 180

20 2

3.4E-02 1.4E-02 2.1E-02 3.4E-02 4.7E-02 4.2E-02 1.4E-02 2.8E-02 2.3E-02 9.0E-03 2.1E-02 1.2E-02 9.0E-03 3.7E-02 9.0E-03 3.9E-03

4 732

3 16 0.3 49

2 10 10 85

212 33

1 7 6

0.1



(MBq)


(mSv/MBq)


2005 (mSv) Bone scan GIT oesoph reflux “milk scan” Hepatobiliary Lung perfusion Lung ventilation Meckel’s’ diverticulum Myocardial perfusion – 2 day stress/rest (rest) Myocardial perfusion – 2 day stress/rest (stress)Renal scan Renal scan Renal scan Renal transplant Spleen Thyroid GFR GFR

Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Cr-51

MDP or HDP colloid HIDA/EHIDA/DISIDA/DisofeninMAA Technegas pertechnetate tetrofosmin - Myoview tetrofosmin - Myoview DTPA DMSA MAG3 DTPA RBCs damaged pertechnetate DTPA EDTA

285 1 1

10 5

10 1 1

51 42 12

3 7 7

21 26

536 12 90 45 16

161 180 480 156

90 145 150 250

77 22

2

1.1E-02 4.8E-02 2.9E-02 2.3E-02 3.1E-02 2.6E-02 1.3E-02 1.2E-02 8.2E-03 1.5E-02 1.2E-02 8.2E-03 3.8E-02 2.6E-02 8.2E-03 3.4E-03

1681 1 3

10 2

42 2 6

65 57 21

4 67 14

4 0.2


administrations

Mean activity administered

(MBq)


(mSv/MBq)


2005 (mSv) Bone scan Cardiac GHPS Cardiac R/L shunt CSF shunt patency GIT gastric emptying Hepatobiliary Infection Lung perfusion Lung ventilation Meckel’s’ diverticulum Renal scan Renal scan Renal scan Renal transplant Thyroid Tumour GFR GFR

Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Ga-67 Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Ga-67 Tc-99m Cr-51

MDP or HDP RBCs MAA DTPA colloid HIDA/EHIDA/DISIDA/DisofeninCitrate MAA Technegas pertechnetate DTPA DMSA MAG3 DTPA pertechnetate citrate DTPA EDTA

425 3 1 1 1 1 1 4 2 8

26 12

8 3

26 2

27 22

674 525 150

20 23

166 191

50 100 269 255 113 199 200 105 206

35 3

7.0E-03 8.9E-03 1.6E-02 4.8E-03 3.1E-02 2.1E-02 1.3E-01 1.6E-02 2.2E-02 1.7E-02 6.2E-03 1.1E-02 9.0E-03 6.2E-03 1.7E-02 1.3E-01 6.2E-03 2.6E-03

2005 14

2 0.1

1 3

25 3 4

37 41 15 14

4 46 53

6 0.2

Table B.5: Data for adult Procedure description Radionuclide Pharmaceutical Number of


(MBq)


(mSv/MBq)


2005 (mSv) Bone scan Brain Brain Brain Cardiac GHPS Cardiac first pass Cardiac R/L shunt GIT blood loss Intra-abdominal bleed GIT colonic transit GIT gastric emptying GIT protein loss Hepatobiliary Infection Infection Infection Lacrimal scintography Liver blood flow Liver/spleen Pre SIRT liver perfusion Lung perfusion Lung ventilation Lung ventilation

Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Ga-67 Tc-99m Tc-99m Tc-99m Tc-99m Ga-67 Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m

MDP or HDP DTPA HMPAO Neurolite RBCs RBCs MAA RBCs RBCs citrate colloid Dextran (HAS) HIDA/EHIDA/DISIDA/DisofeninWBC-colloid citrate MAB pertechnetate RBCs colloid MAA MAA Technegas DTPA Aerosol

12843 2

53 1

585 1 3

55 1

28 80

2 322

48 30 10 20

4 10 58

1057 948

11

751 740 661 800 670 550 150 656 700

8 29

250 126 501 155 630

15 680 125 336 134

41 118

54945 5.7E-03 7 4.9E-03

326 9.3E-03 7 9.3E-03

2742 7.0E-03 4 7.0E-03 5 1.1E-02

253 7.0E-03 5 7.0E-03

41 1.9E-01 55 2.4E-02

3 6.1E-03 687 1.7E-02 265 1.1E-02 465 1.0E-01

59 9.3E-03 4 1.2E-02

19 7.0E-03 12 9.4E-03

214 1.1E-02 1563 1.1E-02

576 1.5E-02 6.1E-03 8

Procedure description Radionuclide Pharmaceutical Number of administrations


(MBq)


(mSv/MBq)


2005 (mSv) Lymphangiogram Lymphoscintigraphy – melanoma Lymphoscintigraphy – breast Ca Lymphoscintigraphy Breast & melanoma Meckel’s’ diverticulum Myocardial perfusion – rest Myocardial perfusion – stress Myocardial perfusion – 2 day stress/rest (rest) Myocardial perfusion – 2 day stress/rest (stress)Myocardial perfusion – 2 day rest/stress (stress)Myocardial perfusion – 1 day rest/stress (rest) Myocardial perfusion – 1 day rest/stress (stress)Myocardial perfusion – 1 day rest/stress (rest) Myocardial perfusion – 1 day rest/stress (stress)Parathyroid Plasma volume measurements Renal scan Renal scan Renal scan Renal transplant Salivary glands Schilling Tests Somatostatin receptors Spleen Testicular scan Thyroid Thyroid – WB scan for Ca

Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tl-201 Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m I-125 Tc-99m Tc-99m Tc-99m Tc-99m Tc-99m Co-57 In-111 Tc-99m Tc-99m Tc-99m I-131

nanocolloid nanocolloid nanocolloid filtered sulphur colloid pertechnetate chloride mibi mibi mibi mibi mibi mibi tetrofosmin - Myoview tetrofosmin - Myoview mibi albumen DTPA DMSA MAG3 DTPA pertechnetate cyanocobalamin (with flushing)octreotide RBCs damaged pertechnetate pertechnetate iodine

10 204 243 179

23 7 6

208 235

13 528 581 235 235 231

86 429 159 295

45 1

26 29

3 21

1583 28

48 45 52 40

300 183 876 743 739

1100 398

1075 350

1007 730 0.08 320 127 221 297 110 0.02 185 200 172 123

43

4.3E-03 1.0E-02 1.0E-02 1.0E-02 1.3E-02 2.2E-01 7.9E-03 9.0E-03 7.9E-03 7.9E-03 9.0E-03 7.9E-03 7.6E-03 7.0E-03 9.0E-03 2.2E-01 4.9E-03 8.8E-03 7.0E-03 4.9E-03 1.3E-02 2.1E+00 5.4E-02 1.9E-02 1.3E-02 1.3E-02 6.1E-02

2 92

128 72 90

282 42

1391 1371

113 5416

13227 625

1642 1518

2 672 177 457

66 1 1

289 11 47

2538 73

Procedure description Radionuclide Pharmaceutical Number of administrations


(MBq)


(mSv/MBq)


2005 (mSv) Tumour Tumour Tumour Tumour Tumour GFR GFR Red cell volume

Tl-201 Ga-67 I-131 I-123 Tc-99m Tc-99m Cr-51 Cr-51

chloride citrate MIBG MIBG mibi DTPA EDTA RBCs

2 43

2 3 6

240 182 147

140 204

27 171 685 136

4 1

2.2E-01 1.0E-01 1.4E-01 1.3E-02 9.0E-03 4.9E-03 2.0E-03 1.7E-01

62 878

7 7

37 160

1 34

38

C: Quantification of radiation risk arising from medical exposure to ionising radiation

Risk coefficients have been derived based on stochastic effects. These are discussed in detail in ICRP60a and summarised further in ICRP73b. The risk coefficients can either be expressed in terms of the probability of fatal cancer, non-fatal cancer, severe hereditary effects or of total detriment. These are given in Table C.1 below, which is taken from ICRP73. Table C.1: Nominal probability coefficients for stochastic effects (probability per unit effective dose)

Detriment (% per Sv) Exposed population Fatal cancer Non-fatal cancer Severe hereditary

effects Total

Adult workers 4.0 0.8 0.8 5.6

Whole population 5.0 1.0 1.3 7.3

Generally the risk is either quoted as a total risk or a risk of death (fatal cancer). When considering the risks arising as a consequence of working with ionising radiation the risk factors for adult workers should be used, whereas for radiation risk to members of the public the risk factors for the whole population should be used. However, there are limitations with this generalised approach to calculating risk, particularly for doses arising from medical exposure to radiation and additional normalisation factors should be applied to take account of gender and age effects. Furthermore, the risk coefficients given in Table 1 do not take into account deterministic effects. Exposure of paediatric patients would lead to a greater risk than would be assessed using only the coefficients in Table C.1, whereas conversely the risk to the geriatric population would be lower. Therefore, Committee 3 of the ICRP introduced age-dependent renormalisation factors to correct risk factors for the age effectc. These are given in Table C.2.

a International Commission on Radiological Protection. 1990 Recommendations of the International Commission on Radiological Protection. Oxford: ICRP, 1991. ICRP publication 60. b International Commission on Radiological Protection. Radiological protection and safety in medicine. Oxford: ICRP, 1996. ICRP publication 73. c ICRP Committee 3, Minutes of the Wützberg Meeting, September 1995

39

Table C.2: Age correction renormalisation factors for radiation risk Age (years) 1 5 10 15 50 70

Renormalisation factor 3.0 2.5 2.0 1.5 0.5 0.3

The correction factor for adults between the ages of 15 and 50 is taken to be unity.

Business

Nuclear medicine practice and patient doses in New Zealand in