Iranian Journal of Nuclear Medicine
Volume:12 Issue: 1, 2004

Sodium Iodide-131 is administrated for treatment of hyperthyroidism and thyroid cancer. Iodine-131 has multiple routs of excretion (Urine, saliva, sweat, milk, feces, exhalation) from the body. Patients receiving Sodium Iodide-131 therapy exposes other persons and the environment to unwanted radiation and contamination. The major source of radiation dose from administration of Iodine-131 is external radiation, also there is a potential for exposure via contamination. Precautions are necessary to limit the radiation dose to family members, nursing staff and members of public and waste treatment workers to less than 1mSv. Patients received Sodium Iodide-131 may come into close contact with other persons. In order to derive appropriate recommendations, dose rates were measured from the anterior mid-trunk of 29 patients in the upright position within 15 minutes post-dose administration at 3 meters and just before they left the nuclear medicine department at 0.5, 1 and 3 meters. We have also measured urinary iodide excretion in 29 patients to estimate Sodium Iodide-131 urinary excretion pattern in Iranian patients. Based on results, the maximum cumulative dose to nursing staff was on third day (Leaving day) still less than recommended dose by ICRP. The cumulative dose of family members will be more but regarding the time and distance in close contact it will also be less than recommended dose by ICRP. Radiation dose rate was decreased significantly on third day. The urinary excretion patterns in all patients were similar. The urinary excretion rate-time curve in all patients showed multiple peaks due to retention and redistribution of Iodine-131 or entrohepatic cycle of radioiodinated thyroid hormones, which didn’t allow calculation of urinary excretion rate constant. The results also showed that 67 hours post administration of Sodium Iodide-131 about 70% of radiopharmaceutical was excreted through urine, 28% physically decayed or eliminated through other biological routes.

99mTc methoxy isobutyl isonitrile (99mTc MIBI) has been proposed as a tumor-seeking agent in malignant disease. The goal of this study is to evaluate the frequency distribution of the different patterns, intensity and extension of abnormal uptake identified in MIBI scan in relation with various clinical status of the patients diagnosed as multiple myeloma. Forty-three patients entered the study, including six patients with no prior treatment, 22 patients who receive autologous bone marrow graft and 15 patients with history of chemotherapy and radiotherapy. Plasma protein electrophoresis for monoclonal antibody, bone marrow biopsy and urine analysis for Bence-Jones protein has been carried out and standard criteria were used for diagnosis of active disease and remission phase for each patients. The extension of the lesions (E-score) on scintigraphy were categorized into E0-E3 by three nuclear physicians who were blinded to the patient’s clinical condition. I-score was also obtained with comparing the intensity of the lesions with intensity of myocardial uptake and classified as I0-I3. The sensitivity, specificity, positive predicative value and negative predictive value of 99mTc MIBI scan for determining active lesions and relapsed cases were 69%, 100%, 100% and 60%, respectively. Nineteen patients were initially thought to be in remission phase, but scintigraphy was abnormal in 5 cases who were diagnosed as active myeloma later in the course of the study. There was a significant correlation between clinical status and pattern, intensity and extension of the abnormal uptake of 99mTc-MIBI. Also a significant correlation between intensity and extension of the abnormal tracer uptake with serum monoclonal component and urine Bence-jones protein was noted, however no correlation between blood hemoglobulin and degree of extension in scintigraphy was seen. Our study suggests the patterns, extension and intensity of 99mTc MIBI uptake, in addition to the hematological findings are associated with disease activity and clinical status of the patients. Hence, in addition to the standard protocol, 99mTx-MIBI has a very high accuracy for detection of active myeloma disease and also can detect the group of patients who might benefit from treatment.

Reverse redistribution pattern is defined as decreased activity in the myocardium in the rest phase of the myocardial perfusion scan in comparison with the stress images. There are many studies concerning the etiology and clinical significant of this phenomenon in nuclear medicine literature. The dominant idea about etiology of reverse redistribution is early wash out of the radiotracer from the myocardium. There is rather unaminous agreement among researchers about viability of the areas of reverse redistribution and the majority of the studies point to existence of viable tissue in these regions. However from prognostic point of view, this issue is much more controversial. In this review, we tried to summarize the current literature and reach a guideline for practical significance of reverse redistribution in every day work of nuclear medicine specialists.

Imaging of infection and inflammation is an important issue in nuclear medicine as it may have relevant implication for the management of patients with infections or inflammatory diseases. In this regard the synthesis of human polyclonal immunoglobuline G (IgG) radiolabeled with technetium-99m (99mTc) by a novel method, via a nicotinamide hydrazine derivative, was performed. The biological behavior, stability and its high specific activity make this radiopharmaceutical a suitable reagent for radiolabeling of proteins and peptides. In this article the method for synthesis of a sterile and apyrogen 99mTc-HYNIC-hIgG kit is presented. The preparation of the kit consists two steps, in the first step 740 MBq pertechnetate was added in Kit No.1, which contains SnCl2 and tricine. After 5 minutes the aliquot in Kit No.1 was added to Kit No.2, which contains HYNIC-hIgG. 99mTc-HYNIC-hIgG complex is stable in cysteine and serum with a labeling efficiency more than 90% after one hour.

Measurement of absolute or differential renal function using radiotracers plays an important role in the clinical management of various renal diseases. Gamma camera quantitative methods in approximation of renal clearance may potentially be as accurate as plasma clearance methods. However some critical factors such as kidney depth and background counts are still troublesome in the use of this technique. In this study the conjugate-view method along with some background correction techniques have been used for the measurement of renal activity in 99mTc-MAG3 renography. Transmission data were used for attenuation correction and the source volume was considered for accurate background subtraction. The study was performed in 35 adult patients referred to our department for conventional renography and ERPF calculation. Depending on the patient’s weight approximately 10-15 mCi 99mTc-MAG3 was injected in the form of a sharp bolus and 60 frames of 1 second followed by 174 frames of 10 seconds were acquired for each patient. Imaging was performed on a dual-head gamma camera (SOLUS; SunSpark10, ADAC Laboratories, Milpitas, CA). Anterior and posterior views were acquired simultaneously. A LEHR collimator was used to correct scatter for the emission and transmission images. Buijs factor was applied on background counts before background correction (Rutland-Patlak equation). Gamma camera clearance was calculated using renal uptake in 1-2, 1.5-2.5, 2-3 min. The same procedure was repeated for both renograms obtained from posterior projection and conjugate views. The plasma clearance was also directly calculated by three blood samples obtained at 40, 80, 120 min after injection. 99mTc-MAG3 clearances using direct sampling method were used as reference values and compared to the results obtained from the renograms. The maximum correlation was found between conjugate view clearance at 2-3 min (R=0.99, R²=0.98, SE=15). Conventional posterior view acquisition at the same time had showed less correlation (R=0.956, R²=0.914). Both gamma camera methods after vascular activity subtraction revealed worse correlation (R=0.717 to 0.812). Conjugate view clearance can be used for calculation of renal clearance with a very good approximation. However in the presence of overlapping organs (Liver and spleen) may interfere with the results. Further work needed on to find the best method of background subtraction.

[18F]KF, considered as a reference standard for positron emission tomography of the skeletal system, was produced by the bombardment of enriched water ([18O]H2O>95%) with high energy protons in NRCAM cyclotron. After the extraction of fluoride from enriched water as KF, and passing it through microbial filter and fine adjustment of acidity and osmolality, it was converted into an injectable form. Pre-clinical investigations and biological controls were performed to determine radioisotope distribution in laboratory rats, thus suitable information was gathered for imaging in humans. This radiopharmaceutical was proved to be quite safe and of high quality as a result of testing in laboratory rats.

Scatter radiation is one of the major sources of error in nuclear medicine data processing. Different methods of scatter correction have been introduced in order to improve the quality of data. However the best method is to avoid recording of scatter photons in acquisition. The only difference between scattered and non-scattered photons is the energy. Pulse height analyzer is the only option available to discriminate primary photons from scattered ones. Energy resolution of the gamma camera is gradually improving consequently the energy window width has to be decreased accordingly. In this study we tried to determine the most appropriate energy window width for present gamma camera systems. Methods and Materials: Since it is not possible to retrieve the data spectrum from the most of the gamma camera systems, a simple method was developed to extract the data from the image of the energy spectrum. Using a scatter phantom different level of scatter and count rate were generated and corresponding energy spectrum data were analyzed. It was assumed that around the peak of the spectrum, the primary photons obey a Gaussian distribution. The data were analyzed using three different methods. All methods prove that the optimum window width regarding the present gamma camera energy resolution is 15%. At this level, the scattered radiation is decreased to 5%. In comparison to the conventional widow width of 20%, the sensitivity does not change dramatically. At the present, for most gamma camera, the energy window width of 20% is recommended. However occasionally energy window width of 15% and 25% are also used. In this study the energy spectrum at different levels of scatter were analyzed and the most suitable energy window width was found to be 15% for the gamma camera having approximate energy resolution of 11%. At this window setting the scatter decreases to 5% of the total counts recorded. Visually the quality of the images dose not improves significantly. However accuracy of data quantification improve significantly.

Few nuclear cardiology surveys were published in the literature, mostly from developed countries. The aim of this study is to perform a nuclear cardiology survey in Iran. This may lead to better decision making and programming. Methods and Materials: A questionnaire was sent by mail or e-mail to all nuclear medicine centers in Iran asking for details of nuclear cardiology practice in year 2002. Also ownership of the centers, number and type of gamma cameras and number of cardiac studies in each week were recorded. Some centers were studied using telephone interviews. From 79 nuclear medicine centers in Iran, 55 centers (69.6%) filled the questionnaire including 28 centers in Tehran and 27 centers in other cities. Among them 27 centers were private clinics. There was 69 gamma cameras in these centers, 62.3% with SPECT capability. It is estimated that we may have 100 gamma cameras in Iran. About 85.5% of centers perform cardiac studies routinely. Tc-99m-MIBI is used in more than 85.7% of the studies and some centers do not use Tl-201. Pharmacological stress with infusion of Dipyridamole is used in 56.7% of the studies and treadmill is the main type of physical exercise (40.2%). SPECT technique was used in 93% of studies including 2.5% of gated SPECT. About 64.3% of centers used two day protocol for imaging. Our study showed that about 65594 cardiac studies were done in Iran each year with myocardial perfusion scan accounting for about 99.2% of the studies. Considering population of the country (About 65 millions) nuclear cardiology activity will be about 1.01 study/1000/year. For viability assessment, Tl-201 with rest redistribution technique is used in 10.7% of cases while re-injection is used in 29.8% of cases and TNG augmented Tc-99m-MIBI injection at rest in 59.5%. Activity of nuclear cardiology is about 15 studies/1000 population/year in USA and 2.2 studies/1000/year in Europe. Although it is not uniformly practiced in different countries of Europe, however the numbers indicate that nuclear cardiology is underutilized in Iran (Less than half of the European mean). Education of the physicians as well as upgrading gamma cameras will improve practice of nuclear cardiology in Iran.