PATIENT DOSES DUE TO DIAGNOSTIC NUCLEAR MEDICINE EXAMINATIONS IN LITHUANIA Vaida Grigonienė, A. Čepulienė, F. Sakalauskas, J. Marcinkevičius, J. Žiliukas Kaunas, 2012 1
Radiation protection Efficient radiation protection includes the elimination of unnecessary or unproductive radiation exposure. According to Basic Safety Standard all countries should constrain the diagnostic reference levels (DRLs). DRLs are expressed in administered activities (MBq). 2
Diagnostic reference levels in Lithuania DRLs have to be established for the most frequent examinations. Periodically these DRLs have to be reviewed and updated, if it is need. DRLs incorporated into Lithuanian legislation are taken from [1]. DRLs in Lithuania were not reviewed until now. [1] International Atomic Energy Agency (IAEA). Applying Radiation Safety Standards in Nuclear Medicine Safety Report series No. 40. Vienna, 2005. 3
Data collection Data about diagnostic nuclear medicine examinations and patient were collected from all NM centers. In the survey were included 6 body localizations for which NM examinations are performed mostly in Lithuania: bone, kidney, thyroid, parathyroid, heart and lung. 4
Average activity calculation All data were grouped according to examined organ and used radiopharmaceuticals (RF). Average administered activity per examination was estimated in each NM center and compared between them. Later was estimated arithmetic average of administered activity per examination in Lithuania. Average activities per diagnostic nuclear medicine examination were compared with DRLs of Lithuania and seven other countries. 5
Patients effective dose calculation Patients effective doses were estimated using conservative method. S ef =k*a k- conversion coefficients (msv/mbq), A administered activity (MBq) This method does not evaluate individual patient s characteristics and all patients are equated to standard patient. Patients effective doses due to various NM examinations were compared between NM centers. Average patients effective doses of most popular NM examinations were calculated in Lithuania too. 6
Most frequent NM examinations in Lithuania It is performed from 3 to 26 different examinations in one NM center in Lithuania. 16951 diagnostic nuclear medicine examinations of bone, kidney, myocardial, lung, thyroid and parathyroid were performed in Lithuania in 2011 according to NM centers given information. Most frequent examinations are bone (31%), kidney (28%) and thyroid (25%) examinations. Fig. 1. Distribution of bone, kidney, thyroid, parathyroid, Myocardial, lung NM examinations in 2011 year. 7
Radiopharmaceuticals Radiopharmaceuticals usage depends on few circumstances: its properties, NM center specialization, type of equipment in NM center and national insurance health fund financing. Were analyzed 10 radiopharmaceuticals used for NM examinations of 6 most popular body localizations : 99mTc - MAG3, 99mTc DTPA, 99mTc MDP, 99mTc MIBI, 99mTc pertechnetate, 99mTc MYO, 99mTc MAA, 99mTc DMSA, 131I hipuran, 131I sodium iodide. 8
Radiopharmaceuticals distribution in Lithuania The most frequent radionuclide is 99mTc, 87% used radiopharmaceuticals are labeled with it, and only 13% are labeled with 131I. According to literature frequency of radiopharmaceuticals with 99mTc radionuclide increased about 50% in the last ten years*. * L. Kid. Cures for Patients, Nuclear Engineering International, 2008. 9
Administered activity I Administered activity to patient depends on few factors: examination, patient s physical and pathological condition and type of equipment. Administered activity can vary even for the same examination, but different patients. The most important is, that administered activity would be optimized - a view has to be good enough to make accurate diagnose while patient dose is minimal. 10
Administered activity II Administered activity per NM examination can vary up to two times if the same examination is performed with the same RF in different NM centers. The average activity is 108 MBq in this case, but generally results are very scattered (the biggest deviation from average is 63% and the less 24%). 11
Medium, minimum and maximum administered activity for patients performing NM examinations of 6 most popular body localizations in Lithuanian NM centers 12
Medium, minimum and maximum administered activity for patients performing thyroid scintigraphy NM examination in Lithuanian NM centers The biggest differences are between big and little nuclear medicine centers. Probably the biggest influence is done by type of equipment. 13
Average, maximal and minimal administered activity to patients performing different nuclear medicine examinations in Lithuania centers. Examination Radiopharmaceutical Average activity, MBq Max. activity, MBq Min. activity, MBq Bone 99m Tc MDP 517 690 380 Kidney 131 I-hipuranas 366 99m Tc DTPA 108 200 40 99m Tc MAG3 129 176 80 Thyroid Na 131 I 63 320 3 TcO 4-92 150 78 Parathyroid 99m Tc MIBI 347 600 77 Heart 99m Tc MIBI 581 640 500 99m Tc MYO 700 700 700 Lungs 99m Tc MIBI 682 740 650 14
Average patient s effective doses per examination 15
Comparison of average administered activity per NM examination in NM centers with Lithuanian DRLs 16
Comparison of average administered activity per NM examination in NM centers with Lithuanian and 7 others countries DRLs (I) 17
Comparison of average administered activity per NM examination in NM centers with Lithuanian and 7 others countries DRLs (II) 18
Conclusions Administered activities to patient in Lithuania are one of the smallest. Lithuanian practitioners considers to individual patient physical parameters before RF administer. It need to continue the data collecting about diagnostic nuclear medicine examinations to standard patients. Only then would be possible to evaluate DRLs optimally in Lithuania. 19
Thank You 20