use of radioactive pharmaceuticals for diagnostic nuclear medicine procedures is one of the main sources of radiation exposure resulting from ionizing radiation to populations
. annual assessment of patients absorbed dose can give a quantitative estimate of per capita population absorbed dose .
risk of exposure to ionizing radiations is expressed by factors such as shortening of life span and induced malignancies .
the international commission on radiological protection ( icrp ) provides the effective doses , and hence the radiation risk to patients caused by various radiopharmaceuticals and nuclear medicine procedures .
although , the annual number of nuclear medicine procedures and their collective dose are way below the corresponding values for medical x - ray examinations ( 2% and 6% , respectively ) , the mean dose per procedure is larger for nuclear medicine ( 4.6 msv ) than for medical x - rays ( 1.2 msv ) . with respect to the rapid growth in number of nuclear medicine procedures performed in iran , and considering the fact that previous survey in tehran was performed
a decade ago , in 2003 , we performed this study to give an updated estimate on the statistics and trends of nuclear medicine procedures as part of a residency thesis .
the data of the annual diagnostic nuclear medicine procedures were obtained for all four active nuclear medicine centers affiliated to shahid beheshti university of medical sciences , tehran , iran , during 2009 and 2010 .
the data comprised the type and frequency of examinations , type of radiopharmaceuticals used , range of administered activity for each examination , and age distribution of the patients . as the amount of dose used in different nuclear centers varied , the mean administered activity for each examination was used in the five age brackets of < 1 year , 1 - 5 years , 6 - 10 years , 11 - 15 years , and > 16 years .
the first column in table 1 shows the diagnostic nuclear medicine procedures and corresponding radiopharmaceuticals used . to calculate the effective dose and collective effective dose , the authors used the effective dose per unit administered activity given in icrp publication no .
53 ( 1988 ) and its addenda , icrp publication no . 80 ( 1999 ) , and icrp publication no .
the effective dose per examination ( fourth column ) was obtained by multiplying the mean administered activity ( second column ) by the corresponding effective dose per unit administered activities for each examination ( third column ) .
the annual number of each examination in the five age groups is listed in the fifth column of table 1 .
the collective effective dose for each examination is shown in the last column , which was calculated by multiplying the effective dose per examination by the corresponding number of examinations in each age bracket .
the effective dose per procedure was obtained by summing the effective doses used for all radiopharmaceuticals , and the collective effective dose was obtained .
mean administered activities , effective dose per unit administered activities , effective dose per examination , annual number of examinations , and collective effective doses for diagnostic nuclear medicine examinations in 2010 frequency and percentage of nuclear medicine examinations in 2009 - 2010
the annual activities of the nuclear medicine centers in 2010 is provided in table 1 , which comprises the examination type , radiopharmaceutical used , mean administered activities ( mbq ) , effective dose per unit administered activity ( msv / mbq ) , and the effective dose per examination ( msv ) for each examination in the five age groups .
some miscellaneous procedures , such as red blood cell scan , indirect radionuclide cystography , and dacryoscintigraphy using tc pertechnetate , are provided as 
the annual total number of examinations and corresponding collective effective doses are calculated and provided in the last row of table 1 .
figure 1 is showing the percentage of the total number of examinations and percentage collective effective dose . during these 2 years ,
results reveal a 6.14% and 3.63% increase in the annual number of examinations and collective effective dose , respectively [ figure 1 and table 2 ] . the contribution of nuclear medicine procedures from total annual number of examinations and collective effective dose ( average of 2009 , 2010 ) percentage share of radionuclides from total number of procedures and collective effective dose ( average of 2009 , 2010 ) the most frequently performed procedures were bone ( 30.16% ) , cardiac ( 28.96% ) , renal ( 17.97% ) , and thyroid scintigraphies ( 7.93% ) , which contributed to 24.01% , 36.76% , 5.82% , and 2.08% of the average collective and effective dose during these 2 years .
figure 2 shows the relative contribution of radionuclides to collective effective dose and total number of procedures as averaged over these 2 years .
the most frequently used radiopharmaceutical was tc , which contributed to 98.20% of a total number of examinations and 89.89% of collective effective dose .
although i accounted for only 0.34% of procedures , it contributed to 5.68% of the collective effective dose .
comprehensive studies on diagnostic nuclear medicine procedures and their contribution to the population absorbed doses have been reported by many investigators worldwide . however , despite the rapid growth of these procedures in iran , there is a profound lack of statistics and the previous survey in tehran was conducted a decade ago .
compared to the previous study by the same group in the same centers , striking differences are noted in trends of diagnostic nuclear medicine procedures .
thyroid scintigraphies with i which accounted for 2.35% of total number of procedures and resulted in 16.59% of collective effective dose in 1999 and 2000 contributed to only 0.03% of the number of examinations and 0.07% of the effective dose in 2009 and 2010 .
this is due to substitution of i with tc for thyroid examinations , which has led to less radiation absorbed dose from i to the patients . on the other hand
, there is tremendous growth in the number of cardiac ( 55.7-fold ) and bone ( 3.60-fold ) scans with increases from 0.52% and 8.4% to 28.97% and 30.25% during the same period .
the huge increase in the number of cardiac examinations is mainly due to the introduction of single - photon emission computed tomography technique .
the changes in bone scan frequency could be the result of an increase in the prevalence of malignancies and lack of other screening techniques such as positron emission tomography ( pet ) scanners in the country .
the overall number of thyroid examinations has decreased from higher than 80% in 1989 to 7.91% in 2010 .
this could be the result of lower prevalence of goiter due to the implementation of iodine enrichment diet programs , lower referral of patients by specialists , and the introduction of fine needle aspiration and advanced ultrasonography techniques .
the latter two reasons are also responsible for the 78-fold decrease in liver / spleen tc - sulfur colloid examinations from 7% in 1989 to 0.09 in 2010 .
together , bone , cardiac , and renal scans accounted for 70.04% of examinations and 66.59% of collective effective dose .
based on the results of our study , striking changes are noted on the trends of diagnostic nuclear medicine procedures in iran . this field is still evolving in the country , and this trend will change further with the introduction of pet scanners .
 purpose : use of radiopharmaceuticals for diagnostic nuclear medicine procedures is one of the main sources of radiation exposure . we performed this study with respect to the rapid growth in nuclear medicine in iran and lack of updated statistics.materials and methods : the data were obtained for all active nuclear medicine centers affiliated to shahid beheshti university of medical sciences during 2009 and 2010.results:the most frequently performed procedures were bone ( 30.16% ) , cardiac ( 28.96% ) , renal ( 17.97% ) , and thyroid ( 7.93% ) scans . 
 there was a significant decrease in the number of thyroid scintigraphies with 131i and 99mtc - sulfur colloid liver / spleen scans and tremendous increase in the frequencies of cardiac and bone scintigraphies compared to one decade ago.conclusion:compared to previous studies , there were striking changes in trends of diagnostic nuclear medicine procedures in tehran . 
 this field is still evolving in the country , and this trend will further change with the introduction of positron emission tomography scanners in future . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION
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Conflicts of interest