Iranian Journal of Nuclear Medicine
Volume:19 Issue: 2, Summer-Autumn 2011

Radioiodine therapy is the safest, simplest, least expensive and most effective method for treatment of hyperthyroidism. The method employed in this research was a systematic bibliographic review, in which only valid studies or the clinically detailed enough open-labeled studies using validated scales were used. Iodine-131 (I-131) acts by the destructive effect of short-range beta radiation on thyroid cells. Indications for radioiodine therapy include toxic nodules (in which I-131 is the first choice of treatment), recurrent hyperthyroidism after antithyroid treatment or surgery, intolerance to antithyroid therapy due to side-effects and patient preference. Due to difficulties in previous methods for dose determination, fixed dose method of I-131 is now considered the best practical method for radioiodine therapy in primary hyperthyroidism. Absolute contraindications for radioiodine treatment are pregnancy and lactation. In pediatric patients, radioiodine therapy can be used, but is mainly considered in recurrent toxic goiter and when antithyroid medication is ineffective. There is no clear evidence indicative of carcinogenic or teratogenic effect of this agent.

Despite widespread use of 67Gallium for lymphoma evaluation, timing of imaging after injection is a matter of controversy and to the extent of our knowledge no direct comparison has been made between early and delayed gallium images. We aimed to compare 24 and 48 hours post injection planar gallium imaging for evaluation of lymphoma recurrence. 255 patients suspicious of recurrent lymphoma were included in the study. Twenty four and 48 hours post injection (10 mCi) whole body Gallium imaging was performed. Semi-quantitative evaluation (background corrected) was carried out in positive whole body 67Gallium scans. Diagnosis of recurrence was made by combination of clinical or pathologic examination if possible. In 59 patients the final diagnosis was made by tissue biopsy. In case of uncertain diagnosis, follow up of the patients (mean duration of 13 months) was used. The diagnosis was finally made by the referring hematologist. Whole body gallium scintigraphy was positive in 115 out of 150 patients with recurrence (sensitivity of 76%). Comparison of the 24 and 48 hour images did not show any new lesion in the 48 hour images. However, delayed 48 hours images were required for definite detection of the gallium avid lesions in the abdominal and pelvic areas in 40 patients. Semi-quantitative evaluation of the lesions showed higher lesion to background ratio for 48 compared to the 24 hour images (p<0.001). Considering higher lesion to background activity in the 48 hour images, delayed whole body 67Gallium imaging may be more desirable for diagnosis of recurrent lymphoma, however 24 hour images may be sufficient. Delayed imaging can be reserved for suspicious activities (such as in abdominal images). This strategy can save time and is more convenient for the imaging centers.

Due to the interesting pharmacological properties of radiolabeled metal oxine derivatives such as cell internalization, tumor avidity and antiproteosome activity, 111In-tris[8-Hydroxy-2-methylquinoline] (111In-HMQ) was developed in this study. 111In-HMQ was prepared using 111InCl3 and 8-Hydroxy-2-methylquinoline (HMQ) for 60 min at 100°C (radiochemical purity: >99% ITLC, >99% HPLC, specific activity: 13-14 GBq/mmol). Stability of the complex was checked in final formulation and in the presence of human serum for 48 h. The partition coefficient was calculated for the compound (log P=0.68). The biodistribution of the labeled compound in vital organs of wild-type rats was studied using scarification studies and SPECT up to 24 h. A detailed comparative pharmacokinetic study for 111In cation and 111In-HMQ are performed up to 24h. The complex is mostly cleaned from the circulation by kidneys and is a compound rapidly washing from the circulation. The biodistribution of the complex in tumor models is on-going.

In order to assess echocardiographic left ventricular functional indices in patients with differentiated thyroid carcinoma (DTC), after L-T4 withdrawal (short-term overt hypothyroidism) and during TSH suppressive therapy, we have evaluated cardiac hemodynamics in a single cohort study. 24 patients with DTC were studied in two phases: 1: at least 4 weeks after L-T4 withdrawal, 2: at least 8 weeks after beginning TSH suppressive therapy. All patients underwent conventional, Doppler and tissue Doppler echocardiography. Although early diastolic mitral inflow velocity (E wave) (p=0.033), and early diastolic velocity of mitral annulus [E(m)] (p Short-term overt hypothyroidism or L-T4 suppressive therapy in patients with DTC may have undesirable cardiovascular effects. So in patients with known history of cardiovascular abnormalities, the caring physician should be aware of the cardiovascular complications during hypothyroidism or suppressive therapy.

In order to develop a radiolabeled calcitonin (CT) derivative for receptor imaging studies, CT was successively labeled with 67Ga-gallium chloride. The best results of the conjugation were obtained by the addition of 0.5 ml of a CT nasal pharmaceutical solution (1100 IU) to a glass tube pre-coated with DTPA-dianhydride (0.01 mg) at 25°C with continuous mild stirring for 30 min. After solid phase purification of the radiolabeled hormone, instant thin layer chromatography (ITLC) showed radiochemical purity of higher than 95 % at optimized conditions (specific activity =67-134 KBq/IU, labeling efficiency 70%). 67Ga-DTPA-CT mainly accumulates in the liver. Preliminary in vivo studies (ID/g%) in male wild-type rats showed significant liver uptake of the tracer after 24 hours. 67Ga-DTPA-CT can be a suitable probe for biodistribution study of CT receptors in various physiological as well as neoplastic lesions with over-expressed calcitonin receptors.

The aim of this study was to evaluate the impact of measurement of coronary artery calcification score (CAC) in patients with suspected coronary artery disease (CAD) and a normal myocardial perfusion scan. In a prospective study we measured the calcium score of 74 patients (29 m, 45 f, mean age 58.7 (m) and 64.4 (f)) with suspicion of CAD and a normal perfusion scan. In all patients a pharmacological stress myocardial perfusion imaging (MPI) with dipyridamole was performed. Both the myocardial perfusion scintigraphy and calcium scoring were performed on a T6 Symbia gamma camera (Siemens, Knoxville, USA). Attenuation correction was performed using a low dose CT. The mean total CAC score was 182.6±435.7 and ranged from 0 -2309. 21/29 of the male patients (72%) and 17/45 of the female patients (38%) had an Agatston score of > 10. There were 9 cases (5m, 4f) with a calcium score of > 400 and 3 cases (2m, 1f) with a calcium score > 1000. No cardiac event was noted in these patients during a mean follow up time of 10.3 months (range 7-13 months, median 11 months) except one cardiac death of a patient with total Agatston score of 278. Seven patients also underwent angiography because of their clinical symptoms, 4 of which (57%) had an elevated Agatston score. Our study showed that calcium score measurement accompanied with SPECT imaging is feasible in routine myocardial perfusion imaging with SPECT/CT machines. Calcium score measurement in patients with normal stress myocardial perfusion scintigraphy, may be useful in risk stratification of the patients. Further prospective studies with larger patient numbers and longer follow-up time are needed to find out the impact of this advantage by hybrid imaging.

Photon attenuation in tissues is the primary physical degrading factor limiting both visual qualitative interpretation and quantitative analysis capabilities of reconstructed Single Photon Emission Computed Tomography (SPECT) images. The aim of present study was to investigate the effect of attenuation correction on the detection of activation foci following statistical analysis with SPM. The study population consisted of twenty normal subjects (11 male, 9 female, and age 30-40 years). SPECT images were reconstructed using filter back projection and attenuation correction was done by the Chang method. The SPECT imagings was obtained 20 min after intravenous injection of 740-1110 MBq (20-30 mCi) of Tc99m-ECD and were acquired on 128×128 matrices with a 20% symmetric energy window at 140 keV. These data publicly distributed by the Society of Nuclear Medicine of Toronto Hospital. The data was standardized with respect to the Montreal Neurological Institute (MNI) atlas with a 12 parameter affine transformations. Images were then smoothed by a Gaussian filter of 10 mm FWHM. Significance differences between SPECT images were estimated at every voxel using statistical t-test and p-value as the significant criteria was set at 0.05. The contrast comparing non attenuation corrected to attenuation corrected images suggest that regional brain perfusion activity increase in the cerebrum, frontal (T-value 12.06), temporal (T-value 10.63) and occipital (T-value 9.31) lobe and decrease in the sub-lobar, extra-nuclear (T-value 17.46) and limbic lobe, posterior cingulate (T-value 17.46) before attenuation correction compare with attenuation correction. It can be concluded that applying attenuation correction in brain SPECT can effectively improve the accuracy of the detection of activation area (p<0.05).

Various bone palliative therapeutic agents have been developed and widely used for bone metastasis such as 153Sm-EDTMP. In this study, production, quality control and biodistribution studies of a newly developed therapeutic compound have been presented followed by imaging studies in wild-type rodents. 153Sm-TTHMP was prepared starting from 153Sm-SmCl3, prepared by neutron activation of an enriched 152Sm sample (purity >98%), and in-house synthesized TTHMP in 1h at 25°C followed by stability tests, partition coefficient determination and biodistribution studies of in wild-type rodents using scarification and SPECT imaging. The radiolabled Sm complex was prepared in high radiochemical purity (>99%, ITLC) and specific activity of 278 GBq/mmol and demonstrated significant stability at 4, 25 and 37°C (in presence of human serum). Initial biodistribution data showed significant bone accumulation of the tracer in 48h. 153Sm-TTHMP can be a potential candidate for bone pain palliation therapy in skeletal metastases, although further biological studies in other mammals is still needed.