Iranian Journal of Nuclear Medicine
Volume:16 Issue: 2, Summer-Autumn 2008

Attenuation correction is a useful process for improving myocardial perfusion SPECT and is dependent on activity and distribution of attenuation coefficients in the body (attenuation map). Attenuation artifacts are a common problem in myocardial perfusion SPECT. The aim of this study was to compare the effect of attenuation correction using different attenuation maps and different activities in a specially designed heart phantom. The SPECT imaging for different activities and different body contours were performed by a phantom using tissue-equivalent boluses for making different thicknesses. The activity was ranged from 0.3-2mCi and the images were acquired in 180 degree, 32 steps. The images were reconstructed by OSEM method in a PC computer using Matlab software. Attenuation map were derived from CT images of the phantom. Two quality and quantity indices, derived from universal image quality index have been used to investigate the effect of attenuation correction in each SPECT image. The result of our measurements showed that the quantity index of corrected image was in the range of 3.5 to 5.2 for minimum and maximum tissue thickness and was independent of activity. Comparing attenuation corrected and uncorrected images, the quality index of corrected image improved by increasing body thickness and decreasing activity of the voxels. Attenuation correction was more effective for images with low activity or phantoms with more thickness. In our study, the location of the pixel relative to the associated attenuator tissues was another important factor in attenuation correction. The more accurate the registration process (attenuation map and SPECT) the better the result of attenuation correction.

Patients administered with a therapeutic dose of 131I for thyroid cancer treatment are potential sources of unacceptably high radiation exposure to other individuals, particularly the patient''s immediate family members. The aim of this study is to investigate effects of early liothyronine consumption after radio-iodine therapy on accumulated dose and exposure rate in patients with thyroid carcinoma. This study was also undertaken to provide specific guidelines as to when 131I treated thyroid cancer patients may be safe to resume close contact with their family members.

Forty patients treated postoperatively by 131I for the first time were studied. These patients were divided into two groups of twenty (group 1 with liothyronine and group 2 without liothyronine). The administered dose was 100 mCi for all patients. Thermoluminescent dosimeter chips were placed on the neck of the patients to measure thyroid dose. Liothyronine was administered 24 h after iodine therapy. Accumulated dose was measured at 12, 24, 36 and 48 h after iodine therapy. Exposure rate was also measured at 0.5, 1 and 1.5 meters from the patient''s body axis with Geiger-Muller detectors at discharge time and one week later.

The findings indicated that liothyronine reduces accumulated dose of thyroid and stimulates rapid washout from the body after 48 h. The patient exposure rate was significantly higher in group 2 during or one week following discharge from the hospital

This study shows that liothyronine consumption decreases the exposure rate of patients at discharge time to the levels lower than that recommended by regulatory organizations.

BEBIG Ruthenium-106 ophthalmic plaques have been used for treatment of uveal melanoma, retinoblastoma, melanoma of the iris and other special applications for many years. The plaques consist of a thin film of 106Ru, a beta emitter, encapsulated in pure silver. The present work proposes a new mathematical eye model for ophthalmic brachytherapy dosimetry. This new model includes detailed description of internal structures, allowing dose determination in different regions of the eye for a more adequate clinical analysis. In the present work, we have used MCNP4C code to calculate relative dose in a new human eye model. The isodose curves and dosimetric characteristics for two 106Ru eye applicators have been determined. Also, absorbed dose values due to both small CCA and CCB concave applicators were obtained for each one of the different structures which compose the eye model and can give relevant information in eventual clinical analyses.

There is a consensus in the literature that sentinel lymph node biopsy is the standard procedure for axillary staging in early stage (I and II) breast cancer patients. Usually during lymphoscintigraphy, the location of the sentinel lymph node is marked on the skin by an indelible ink. In this study we evaluated this issue in our patients. 40 patients with the clinical diagnosis of early stage breast cancer (stage I or II) were included into the study. All patients received periareolar intradermal injections of 18.5 MBq Tc-99m antimony sulfide colloid 2-4 hours before the surgery and 2 ml patent blue V dye in a subdermal and periareolar fashion during surgery. The patients were divided randomly into two groups (20 patients in each group). In group I, the anterior and lateral locations of the sentinel lymph node were marked on the skin with an indelible ink. In group II, no skin marking was used. A sentinel node was defined as any blue node or any node with an ex vivo radioisotope count of twofold or greater than the axillary background. All patients underwent standard axillary lymph node dissection after sentinel node biopsy. Mean age and tumor size were not significantly different between groups. SLN detection rate and number of detected SLNs were not significantly different either (P>0.05). Number of detected lymph nodes was 1.24±0.43 and 1.28±0.61 in group I and II of the patients, respectively. False negative rate (negative SLN and positive axillary nodes) for both groups were 0%. Although marking the location of the sentinel lymph node on the skin with an indelible ink can guide the surgeon during surgery, it can not increase the sentinel lymph node detection rate or improve the results of sentinel lymph node biopsy.

Diabetes mellitus and osteoporosis are two frequent medical conditions with an increasing prevalence in elderly. This study is conducted to evaluate osteoporosis in postmenopausal females with type 2 diabetes mellitus in Sanandaj, the provincial center of Kurdistan province in the west of Iran. From an initial population of 2500 women with type 2 diabetes, 242 postmenopausal women were randomly selected and were compared with 221 non-diabetic postmenopausal women, matched by age and body mass index (BMI). Bone mineral density (BMD) was measured at the L2-L4 vertebrae (anteroposterior projection) and femoral neck with dual energy X-ray absorptiometry (DXA). The statistical significance was set at a P value of. 05 or lower. Prevalence of femoral neck osteoporosis in diabetic women was 30.2 percent (73 cases) and osteopenia was 48.3 percent (117 cases). Osteoporosis prevalence in spine was 7.9 percent (19 cases) and ostropenia was 46.3 percent (112 cases). Osteoporosis in both femoral neck (P=0.001) and spine (P=0.04) were significantly higher in patients than in controls. Correlation between HbA1c and femoral neck (p=0.11, correlation coefficient=0.04) and also spine (p=0.10, correlation coefficient= -0.12) T score was not significant. No significant correlation was found between osteoporosis with presence of microalbuminuria (P=0.91), retinopathy (P=0.33), hypertension (P=0.70), ischemic heart disease (P=0.57) and insulin therapy (P=0.08). This study shows that type 2 diabetic patients have significantly lower T score values and more frequency of osteoporosis than healthy postmenopausal women.

Cardiovascular disease is the major cause of morbidity and mortality in developing and developed countries. Rapid diagnosis of the thrombosis can be an essential step in management of the stroke. In this work a recently developed radiolabeled streptokinase (STP) tracer was evaluated in an animal thrombotic model using SPECT imaging and biodistribution studies. Locally labeled [67Ga]-Streptokinase was checked by ITLC, HPLC and SDS-PAGE experiments to check the tracer integrity and purity. The biodistribution studies were performed in thrombotic femoral vein of rats using tissue counting and preliminary SPECT studies, respectively (up to 2 h). [67Ga]-Streptokinase prepared with suitable radiochemical purity (HPLC >95%, ITLC >99%) was administered to FeCl3 induced thrombotic rats and the percentage of injected dose per gram of tissue (ID/g%) as well as the SPECT images demonstrated the good specific binding of the tracer in thrombotic clots located in heart and aorta 2 hours post injection. [67Ga]-DTPA-STP can be a suitable probe for imaging of thrombosis in cardiovascular diseases. Ga-68 labeled STP has the potential to be an alternative superior labeled compound due to positron emission properties for PET studies as well as appropriate physical half life.

Bilateral diffuse intense breast uptake was noted in a 40 year old female who was evaluated with Tc-99m sestamibi (MIBI) myocardial perfusion scan for possible ischemia. She was breast feeding her 1.5 year old child. The intense uptake in the breasts was superimposed on the apical and anteroapical regions of the myocardium and caused interpretation problem. We recommend considering Tc-99m MIBI breast uptake during breast feeding as a possible cause of non-interpretable, superimposition of radiotracer on the myocardium in myocardial perfusion scan.

Tc-99m pertechnetate scintigraphy is the modality of choice for diagnosis of Meckel''s diverticulum. Interpretation of Meckel''s scan identifies a focal area of radiopharmaceutical uptake in the anterior abdomen similar to normal gastric mucosa. The activity must be of the same pattern and intensity as gastric uptake. We present a 13-year-old patient with gastrointestinal bleeding and anemia. Tc-99m pertechnetate scintigraphy was performed and initial images did not show any abnormal tracer activity in the abdomen. However, imaging continued and a focal activity was detected on the right side of the abdomen 60 minutes delayed image. Follow laparascope operation the Meckel''s diverticulum was removed and the patient''s symptoms disappeared completely. It is suggest to pay special attention to delayed images (60 minutes or beyond) especially when earlier images are negative.