فهرست مطالب

Nuclear Medicine - Volume:26 Issue: 2, Summer-Autumn 2018

Iranian Journal of Nuclear Medicine
Volume:26 Issue: 2, Summer-Autumn 2018

  • تاریخ انتشار: 1397/04/25
  • تعداد عناوین: 8
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  • Alireza Emami-Ardekani, Arefe Mirzabeigi, Armaghan Fard-Esfahani *, Babak Fallahi, Davood Beiki, Arman Hassanzadeh-Rad, Parham Geramifar, Mohammad Eftekhari Pages 68-75
    Introduction
    The present study was aimed to assess the diagnostic performance of the two imaging methods of 131I-metaiodobenzylguanidine (131I-MIBG) and 99mTc-hydrazinonicotinyl-Tyr3-Octreotide (99mTc-HYNIC-TOC) in diagnosis and localization of pheochromocytoma and neuroblastoma.
    Methods
    This study was conducted on 40 consecutive patients with positive pathological results for pheochromocytoma or neuroblastoma. The patients underwent both I-131 131I-MIBG and octreotide scintigraphies. By using the findings of cytopathology, biomarkers, imaging studies, as well as the results of a six-month follow-up, a composite reference standard (CRS) was defined as the diagnostic gold standard.
    Results
    Overall comparison of these two agents revealed higher sensitivity for 131I-MIBG than octreotide study both in patient-based analysis (100% vs. 80.9%, respectively), and lesion-based analysis (94.4% vs. 80.56%, respectively). In pheochromocytoma 131I-MIBG and octreotide are both highly sensitive (100%), while 131I-MIBG is more specific (100% vs. 87.5%). In neuroblastoma, 131I-MIBG is more sensitive than octreotide (100% vs. 81.25%).
    Conclusion
    Our study shows superiority of 131I-MIBG over octreotide scanning in detection of both neuroblastoma and pheochromocytoma lesions. However, a combination of these two diagnostic tools provides more complete information on the nature and the site of lesions. The first suggested study is 131I-MIBG scanning, and if it is not available, or detecting precise location of all lesions is of concern, octreotide scanning can be helpful as a complementary study. Furthermore, in case of octreotide positive lesions, follow-up can be performed with octreotide scan with less radiation burden.
    Keywords: 131I-MIBG, Somatostatin analog, Octreotide, 99mTc-HYNIC-TOC, Pheochromocytoma, Neuroblastoma
  • Maryam Fallahpoor, Mehrshad Abbasi *, Ali Asghar Parach, Ahmad Bitarafan Rajabi, Faraz Kalantari Pages 76-81
    Introduction
    Use of SPECT/CT data is the most accurate method for patient-specific internal dosimetry when isotopes emit single gamma rays. The manual or semi-automatic segmentation of organs is a major obstacle that slows down and limits the patient-specific dosimetry. Using digital phantoms that mimic patient’s anatomy can bypass the segmentation step and facilitate the dosimetry process. In this study, the results of a patient-specific dosimetry based on CT data and XCAT phantom, a flexible phantom with predefined organs, are compared.
    Methods
    The dosimetry results (S-value and SAF) were calculated for a patient with breast cancer who received Samarium-153 ethylenediamine-N,N,N′,N′-tetrakis(methylenephosphonic acid (153Sm-EDTMP). Biodistribution of activity was obtained from the SPECT scan. The anatomical data and attenuation map were extracted from CT as well as the XCAT phantom with different BMIs. GATE Monte-Carlo simulator was used to calculate the dose to different organs based on the activity distribution and segmented anatomy.
    Results
    The whole body dosimetry results are the same for both calculations based on the CT and XCAT with different BMIs; however for target organs, the differences between SAFs and S-values are high. In the spine, the clinically important target organ for Samarium therapy, the dosimetry results obtained from phantoms with unmatched BMIs between XCAT phantom and CT are substantially different.
    Conclusion
    We showed that atlas-based dosimetry using XCAT phantom even with matched BMI may lead to considerable errors as compared to calculations based on patient’s own CT. For accurate dosimetry results, calculations should be done using CT data.
    Keywords: 153Sm-EDTMP, Dosimetry, XCAT phantom, Atlas-based dosimetry, Radio-targeted therapy
  • Ali Rabie, Hassan Yousefnia *, Samaneh Zolghadri, Mojtaba Shamsaei, Amir Reza Jalilian Pages 82-86
    Introduction
    Bone metastases are common in the progression of various tumors leading to severe pain and decrease in quality of life. The aim of this study was to optimize the production of 68Ga-BPAMD as an ideal bone imaging agent using an in-house 68Ge/68Ga generator for future clinical use.
    Methods
    The optimized conditions for the preparation of 68Ga-BPAMD were determined by varying ligand concentration, pH, time and temperature. The radiochemical purity of the complex was checked using ITLC method. The stability at room temperature and in human serum and the hydroxyapatite (HA) binding of the complex were studied. Biodistribution of 68Ga-BPAMD and 68GaCl3 were investigated in male Syrian rats.
    Results
    The radiolabelled compound was prepared with a radiochemical purity of >99% after 15 min at the optimized conditions (30 µg of ligand, 90 °C, pH=3-5). The complex was stable in the final preparation and in the presence of human serum (>98%). HA binding assay demonstrated that at the amount of 10 and 25 mg of HA, 62.3 and 88.5 % of the complex are bound to HA, respectively. The agent demonstrated significant accumulation in the bone tissue, while cleared very fast from blood circulation. Major difference in uptake between 68Ga-BPAMD and 68GaCl3 was observed especially in blood, bone, liver, and spleen which can be considered as favorable characteristics of this agent.
    Conclusion
    According to these results, this agent can be produced with the recently developed in-house generator and considered as a worthy bone PET imaging agent available for further clinical use.
    Keywords: Bone metastasis, BPAMD, 68Ga, PET scan
  • Ali Ketabi, Pardis Ghafarian, Mohammad Amin Mosleh-Shirazi, Seyed Rabi Mahdavi, Mohammad Reza Ay * Pages 87-97
    Introduction
    This study aims to investigate the influence of background activity variation on image quantification in differently reconstructed PET/CT images.
    Methods
    Measurements were performed on a Discovery-690 PET/CT scanner using a custom-built NEMA-like phantom. A background activity level of 5.3 and 2.6 kBq/ml 18F-FDG were applied. Images were reconstructed employing four different reconstruction algorithms: HD (OSEM with no PSF or TOF), PSF only, TOF only, and TOFPSF, with Gaussian filters of 3 and 6.4 mm in FWHM. SUVmax and SUVpeak were obtained and used as cut-off thresholding; Metabolic Tumor Volume (MTV) and Total Lesion Glycolysis (TLG) were measured. The volume recovery coefficients (VRCs), the relative percent error (ΔMTV), and Dice similarity coefficient were assessed with respect to true values.
    Results
    SUVmax and SUVpeak decreased and MTV increased as function of increasing the background dose. The most differences occur in smaller volumes with 3-mm filter; Non-TOF and Non-PSF reconstruction methods were more sensitive to increasing the background activity in the smaller and larger volumes, respectively. The TLG values were affected in the small lesions (decrease up to 12%). In a range of target volumes, differences between the mean ΔMTV in the high and low background dose varied from -11.8% to 7.2% using SUVmax and from 2.1% to 7.6% using SUVpeak inter reconstruction methods.
    Conclusion
    The effect of the background activity variation on SUV-based quantification in small lesion was more noticeable than large lesion. The HD and TOFPSF algorithms had the lowest and the highest sensitivity to background activity, respectively.
    Keywords: 18F-FDG-PET-CT, Background activity, Image reconstruction, MTV, TLG
  • Zehra Pinar Koc *, Pelin Ozcan Kara, Arzu Kaya, Erhan Yilmaz, Ozlem Ucer Pages 98-104
    Introduction
    Recently the most accurate diagnostic method in the diagnosis of prosthesis infection is the combination of Tc-99m labeled leukocyte/bone marrow imaging. However the diagnostic efficiency of the test is influenced because of its low spatial resolution. Recently SPECT/CT imaging is implicated in this test with efficient additional diagnostic improvement. In the departments without capability of SPECT/CT lateral imaging may provide important clinical information. The aim of this study was to analyze the additional diagnostic information provided by additional lateral spot images to the diagnostic accuracy of combined Tc-99m labeled leukocyte/bone marrow imaging in diagnosis of prosthesis infection.
    Methods
    Retrospective evaluation of 11 patients (9 F, 2 M; 61±8,6 years old) with pre-diagnosis of prosthesis infection (4 patients with right knee, 3 left, 2 bilateral, 2 right hip) by two experienced Nuclear Medicine physicians were included into the study. The age of the prosthesis were 7,8±15,3 months by the time of imaging. The imaging was performed from the region of interest at the first, second and fourth hour of injection of approximately 5 mCi (185 MBq) labeled leukocyte imaging and one hour after injection of 5 mCi (185 MBq) Tc-99m nanocolloid in anteroposterior and in additional lateral position. The diagnosis of prosthesis infection was decided in case of increased activity accumulation in leukocyte imaging higher than in bone marrow imaging. The final diagnosis was decided by additional aspiration biopsy (n=1), culture results (n=3), revision arthroplasty (n=1) or according to follow up results (n=6)(sedimentation, CRP) in 3,4±3,4 months follow up.
    Results
    The labeling efficiency of the patients was in an acceptable range (33-67%) in leukocyte labeling. The diagnosis of prosthesis infection was decided in two patients according to scintigraphy results and these two patients were documented to have prosthesis infection (revision arthroplasty and biopsy results). One patient was decided to have prosthesis infection despite negativity of scintigraphy (false negative) due to persistently high sedimentation, CRP levels in follow up despite proper antibiotic treatment. One patient was diagnosed as negative due to demonstration of anterior cellulites rather than prosthesis infection in the lateral images. The diagnostic sensitivity, specificity, accuracy, negative and positive predictive value of the test were 60%, 87.5%, 81%, 60%, 87.5%, respectively for anteroposterior imaging only with additional lateral imaging the rates were increased to 60%, 100%, 91%, 89% and 89%, respectively.
    Conclusion
    Lateral imaging increases the diagnostic accuracy of the combined Tc-99m labeled leukocyte/bone marrow scintigraphy compared to anteroposterior imaging only and might be implemented in combined imaging protocol in case of non-availability of SPECT/CT imaging.
    Keywords: Prosthesis, Infection, Lateral imaging, Tc-99m labeled leukocyte
  • Babak Fallahi, Davood Beiki, Yalda Salehi *, Alireza Emami-Ardekani, Armaghan Fard-Esfahani, Farahnaz Aghahosseini, Mohammad Eftekhari Pages 105-111
    Introduction
    Myocardial perfusion imaging (MPI) is an important imaging modality in managing patients with cardiovascular disease. MPI has a significant role in diagnosis and management of cardiovascular disease; however it is subjected to different artifacts. Combining pharmacologic stress with submaximal exercise reduces side effects, improves image quality, and enhances the detection of ischemia, compared with suboptimal exercise or vasodilator stress alone.
    Methods
    97 patients (62 males and 35 females) which were randomly allocated into two groups were studied using gated single-photon emission computed tomography (SPECT) imaging. The patients were randomly allocated into two different groups: dipyridamole or dipyridamole combined with submaximal exercise group. Subsequently, they were imaged at 15, 60, 120, and 180 minutes after radiotracer injection.
    Results
    97 patients with an average age of 57.1 were compared 15, 60, 120 and 180 minutes after radiotracer injection. Comparing dipyridamole and dipyridamole submaximal exercise group a significant difference in target areas (myocardium, inferior and lateral wall) count ratio to both liver and colon count ratio was observed (P
    Conclusion
    A protocol that combines submaximal exercise with dipyridamole stress is highly effective in improvingthe average count ratio of myocardial walls compared to visceral activity.
    Keywords: Sub maximum exercise, Dipyridamole, Sub-diaphragmatic activity, Gated SPECT
  • Behnoosh Teimourian Fard, Mojtaba Shamsaei Zafarghandi, Soheil Hosseini, Hamid Sabet, Mohammad Reza Ay * Pages 112-120
    Introduction
    Substantive amount of work has been done in modeling and analyzing the scintillation camera system processes including positioning and image formation. The goal of this work is to develop a framework for analyzing performance of nonlinear positioning methods upon construction of a mathematical model of the system. In this study, the photodetector array counts are assumed to follow a multinomial distribution.
    Methods
    We studied effects of several parameters on system performance, including photomultiplier tube (PMT) non-uniform response, gains, shape, size and positioning methods. This was done by constructing linearity and resolution maps, feeding the system a uniform grid of point sources showing the distorted output along with associated blurring intensity. The spatial resolution and linearity parameters are used to evaluate the performance of simulated scintillation camera.
    Results
    The study findings revealed that the square PMT is the best option due to better fitting and quality especially near the edge of the detector and also ability to cover the rectangular crystal area with minimum numbers of PMTs. Also, the resolution resulted from CSE is 5% and 20% better than center of mass and modified center of mass respectively.
    Conclusion
    We showed that the rectangular gamma camera accompanied by an array of square PMTs can introduce the optimum performance regarding linearity and resolution if the nonlinear method, called CSE, is used as positioning method. Further evaluation is needed to evaluate the performance of the proposed gamma camera in practice.
    Keywords: Gamma camera, Square PMT, mathematical modeling, Multinomial distribution, Nonlinearity Map, Correlated signal enhancement
  • Mahdi Haghighatafshar, Tahereh Ghaedian * Pages 121-123
    A 10-year-old boy with a history of bloody discoloration of urine following recent appendectomy was referred to our department for urinary leakage/fistula evaluation. A renal Technetium-99m-L,L-ethylenedicysteine (99mTc-EC) scintigraphy was performed. After injection of radiotracer, a focus of activity appeared in the supralateral part of the right kidney which was confirmed as accumulation of radiotracer in the gall bladder by SPECT and delayed images. Although it is stated that the biliary excretion of 99mTc-EC is negligible, in some cases it could be prominent and potential source of misinterpretation.
    Keywords: 99mTc-EC, Renal scintigraphy, Hepatobiliary excretion, SPECT