Diagnostic reference levels (DRLs) for radiopharmaceuticals administered in nuclear medicine — four-year experience with their use

Vaclav Husali, Pavel Koranda, Zuzana PaSkova X), Karia Petrovd J), Zdenek Prouza J) Department of Nuclear Medicine, University Hospital and Palacky University, Olomouc State Office for Nuclear Safety (SONS) S), Prague, Czech Republic

Introduction of DRLs levels in Czech Republic (CR). DRLs were established four years ago using the results of the national questionnaire survey on the type and amount of administered radiopharmaceuticals (RP) performed during 1996. DRLs were implemented in SONS Regulation No. 184/1997 Coll. for 92 nuclear medicine (NM) procedures, e. g. for "mTc- phosphates bone scintigraphy DRL was 800 MBq, for "mTc-HMPAO brain scintigraphy 800 MBq, for "mTc-MIBI planar scintigraphy of myocardial perfusion 600 MBq, for 2OIT1 SPECT myocardial perfusion 110 MBq, for ""Tc-DMSA kidney scintigraphy 200 MBq etc. DRLs guidelines. In order to facilitate the implementation of DRLs into the clinical practice an explanatory information (guidelines) was prepared about the purpose, significance and correct use of DRLs; the principles given! in BSS [1] and ICRP 73 [2] were taken into account. There are two inappropriate regions of administered activity of RP to patients. The upper inappropriate region is connected with a unnecessarily high radiation burden of a patient without improving a quality of scintillation camera images. The lower inappropriate region results in a poor image quality which may lead to serious diagnostic errors and/or repetition of an examination. DRL indicates the upper boundary of the region of acceptable practice in which the optimal activity of RP administered to a patient is chosen according to the scintillation camera geometry (I, 2, 3 detectors), collimators, time available for the examination etc.; optimal value of RP activity below DRL should assure the lowest necessary dose to achieve the diagnostic information needed. DRLs are applied to a typical 70 kg patient and should be adjusted to account for significantly under-weight and over-weight patients. Activity A of RP administered to a patient having a weight W different from 70 kg (< 60 kg and > 85 kg) is recommended to be 7 calculated as A = A70 x F where F = W° /70 is the scaling factor derived from body surface area. Factor F for children is practically identical with that given in the known EANM recommendation [3]. Thus, activities recommended to be administered to children and adults are determined consistently on a body surface area basis. Our guidelines points out, in accordance with BBS [1] and ICRP 73 [2], that DRL is not a limit which could not be exceeded. DLR should not be exceeded in routine clinical practice; higher levels are acceptable in individual - relatively rare cases - which are justifiable by a patient's clinical condition (other diseases, complications etc.). Check of DRLs practical use. With regard to the prepared amendment to SONS Regulation No. 184/1997 it has been necessary to check how DRLs have been respected in clinical practice. Therefore, two surveys were conducted in 1998 and 2001. The first more detailed questionnaire circulated to 49 departments of NM in CR focussed on three major topics: an observance of DRLs in clinical practice, a method used for the determination of RP activity administered to patients having a weight different from 70 kg and a percentage of examinations in which DRLs had to be exceeded on clinical grounds (with the exception of examinations requiring administration of higher activities due to a patient's weight above 70 kg). The complete response rate was 82 % (40/49). 26 departments which had no remarks on DRLs in SONS Regulation No. 184/1997 were supposed to adhere to them without difficulties. The remaing ones complained that DRLs for some examinations were too low: whole-body planar 67Ga scintigraphy 150 MBq, thyroid gland m 99m " TcO4 scintigraphy 150 MBq, whole-body scintigraphy (tumours) with Tc labelled monoclonal antibodies 500 MBq and others.

XXIV DRO Demanovskii dolina 82 SK0PK018^ 33 departments reported the use of the known procedure recommended by EANM [3] for determining RP activities administered to children and of that for persons having weight higher than 85 kg which was recommended in our DRL guidelines mentioned above. Only 5 departments determined RP activity according to a patient's weight. 23 departments announced no cases of exceeding DRLs with regard to patient's condition and other circumstances. The estimate of a percentage of these cases given by 17 departments ranged from 0.5 % to 10 %. The second questionnaire was distributed in 2001 several months ago before working out the first proposal of the table containing modified values of DRL to be included into the amendment to SONS Regulation No. 184/1997 Coll. The purpose of this survey performed after almost three years since the first one was to find out latest comments on DRLs. Of 49 departments only 20 ones answered; the low response rate was not a surprise because in our covering letter no reply was required in case that a department was satisfied with DRLs and had no comments. Of 20 replies 5 ones contained no remarks, answers of remainig 15 departments helped us to improve the table for the proposed SONS Regulation. DRLs in the amendment to SONS Regulation No.184/1997 Coll. Table 1 contains DRLs proposed to be included into the amendment to this regulation. Using the results of questionnaires and, in some cases, regarding DRLs valid abroad [4, 5, 6], too, the following changes were performed: - eight new radiopharmaceuticals and examinations were included (18F-FDG, 123I iomazenil, 123IIBZM, examination of sentinel nodes and others; 99m - DRL was increased for eight examinations: Tc04 scintigraphy of thyroid gland from 150 MBq to 200 MBq, "mTc-MIBI planar scintigraphy of parathyroid from 400 MBq to 750 MBq, 99mTc-antibodies tumours and inflammation imaging from 600 MBq to 800 MBq etc.; m 99m DRL was decreased for seven examinations: " TcO4 or Tc-DTPA dynamic brain scintigraphy from 800 MBq to 600 MBq,, "Tc-MAA, microspheres lung scintigraphy from 200 MBq to 150 MBq, "mTc-DMSA kidney scintigraphy from 200 MBq to 150 MBq etc.); - two examinations, 133Xe lungs ventilation and mI bengal rose chromextr. function of liver, were omitted; some minor modifications were carried out to improve the arrangement of the table. The increase in DRLs for some examinations was substantiated very carefully taking pains to counterbalance it by their decrease for other examinations where reasonable. Conclusion. The use of DRLs, as a component of a Quality Assurance Programme supervised in departments of NM by SONS, appears to aid in the optimisation of radiation protection for patients undergoing NM procedures.

References [1J Safety Series No. 115: International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources. Vienna, IAEA 1996. [2] ICRP Publication 73: Radiological Protection and Safety in Medicine. Annals of the ICRP, 26, 1996. Oxford, Elsevier Science Ltd. 1996. [3] Paediatric Task Group of the European Association of Nuclear Medicine (EANM): A radiopharmaceutical schedule for imaging in paediatrics. Eur. J. Nucl. Med. 17, 1990, 127 - 129. [4] Notes for Guidance on the Clinical Administration of Radiopharmaceuticals and Use of Sealed Radioactive Sources. Chilton, NRPB 1998. [5] Schtcha, H.: Diagnostische Referenzwerte in der Nuklearmedizin Empfehlungen der Strahlenschutzkommission verabschiedet in der 167. Sitzung der Strahlenschutzkommission am 6./7. Juli 2000. Nuklearmedizin 39 (2000), Nl 18 -Nl 19. [6] Smart, R. C, Towson, J. E.: Diagnostic Reference Activities for Nuclear Medicine Procedures in Australia and New Zealand. Rad. Prot. In Australasia 17, 2000, No.l, 2-14.

XXIV DRO Demanovska dolina 83 Table 1 Proposal of diagnostic reference levels in nuclear medicine to be included in amendment to SONS Regulation No. 184/1997 Coll.

Examination Radio- Substance, DRL Organ Kind, group nuclide chemical form [MBq] scintigraphy bone (whole - body, three - phases, Tc-99m phosphates 800 SPECT) scintigraphy bone marrow (whole - body, SPECT) Tc-99m nanocolloids 550 brain scintigraphy dynamic Tc-99m TcO4, DTPA 600 planar Tc-99m TcO4, DTPA 600 SPECT Tc-99m TcO4, DTPA, HMPAO, ECD 800 receptors 1-123 Iomazenil, IBZM 200 glucose uptake F-18 F-18-FDG 400

cisternography In-Ill DTPA 40 Yb-169 EDTA 40 thyroid gland uptake 1-131 iodide 0.5 Tc-99m TcO4 40 scintigraphy Tc-99m TcO 200 planar 4 Tc-99m MIBI, DMSA 400 1-123 iodide 20 1-131 iodide 7 Tl-201 chloride 80 whole - body, SPECT C Tc-99m MIBI, DMSA (V) 600 in carcinoma of thyroid ~< 1-131 iodide 300 gland [_ Tl-201 chloride 100 parathyroid scintigraphy gland planar Tc-99m • TcO4 200 Tc-99m MIBI 750 Tl-201 chloride 80 adrenals scintigraphy planar 1-123 MIBG 200 norcholesterol, 1-131 MIBG 20 lungs scintigraphy ventilation Tc-99m aerosol, technegas 1000 Kr-81m gas 6000 perfusion static Tc-99m MAA, microspheres 150 SPECT Tc-99m MAA, microspheres 300 heart myocardial imaging Tc-99m MIBI, tetrofosmin 1000 (SPECT) Tl-201 chloride 110 reinjection Tl-201 chloride 40 viability F-18 FDG 500 ventriculography Tc-99m erythrocytes 800 first pass Tc-99m ,. TcO4, HSA 900 lymphatic radionuclide Tc-99m nanocoloid 150 system lymphography sentinel nodes Tc-99m nanocolloid 100 vessels fibrinogen uptake 1-125 3 radionuclide venography Tc-99m MAA 200 (one extremity) DTPA, 300 radionuclide angiography Tc-99m erythrocytes, TcO4, DTPA,HSA 800 thrombus detection Tc-99m platelets 500

XXIV DRO Demanovska doiina 84 blood volume of blood and Tc-99m HSA 80 components 1-131 HSA 6 Cr-51 erythrocytes 6 survival and local destruction Cr-51 erythrocytes, platelets 6 of blood elements In-Ill platelets 10

iron metabolism Fe-59 Fe(III) citrat 3 spleen scintigraphy planar Tc-99m denatured erythrocytes 100 SPECT Tc-99m denatured erythrocytes 200 hepatobiliary scintigraphy system planar Tc-99m colloids 150 SPECT Tc-99m colloids 300 dynamic Tc-99m IDA derivates 250

GIT scintigraphy of salivary glands Tc-99m TcO4 100 oesophagus motility Tc-99m colloids 60 oesophageal reflux Tc-99m colloids 50 gastric emptying Tc-99m colloids 50 Meckel's diverticulum imaging Tc-99m TcO4 400 GI bleeding Tc-99m erythrocytes 700 determination of blood and Cr-51 erythrocytes 4 albumin loss in GIT 1-125 HSA 6 1-131 HSA 6

Schilling test Cc-57 monocyanocobal amin 1 kidneys one — probe renography 1-131 hippuran 1 scintigraphy planar Tc-99m DMSA (III), gluconate 150 SPECT Tc-99m DMSA (III), gluconate 250 dynamic Tc-99m DTPA, MAG3, ECD 250 EPPL, GFR determination Tc-99m MAG3, DTPA 20 1-131 hippuran 0.5 Cr-51 EDTA 3 urinary radionuclide cystography bladder direct Tc-99m TcO4 50 indirect Tc-99m MAG3 200 testes, scintigraphy Tc-99m TcO 400 scrotum 4 tumours scintigraphy (planar, SPECT) Tc-99m MIBI, antibodies 800 In-Ill antibodies, pentetreotide 120 Ga-67 Oa 300 Tl-201 chloride 100 1-123 MIBG 400 1-131 MIBG 20 F-18 FDG 750 scintimammography Tc-99m MIBI, tetrofosmin, (planar, SPECT) phosphonates 800 inflammations scintigraphy (planar, SPECT) Tc-99m leucocytes, HIG 600 Tc-99m antibodies 800 In-Ill leucocytes 30 3+ Ga-67 Ga 200

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