TC Kalawat, CK Kishore¹, R Ram¹, AY Lakshmi², B Vijaylakshmi², P Lakshmi², MR Gupta, R Narayan,K Radhika³, V Siva Kumar¹

Departments of Nuclear Medicine, ¹Nephrology, ²Radiology, and ³Pathology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India

Background: Pyrexia of unknown origin (PUO) is a common clinical problem and often creates a diagnostic dilemma in patients with chronic kidney disease (CKD). In this subset of patients, if the cause of fever remains un-diagnosed, it may increase the morbidity and mortality. In this study, we used 18 F FDG PET CT scan in CKD patients presenting with PUO to localize the hidden focus of infection.

Materials and Methods: In this retrospective study from August 2010 to December 2012, total n = 10 patients (6 M and 4 F), mean age 45 years, range 31-60 years, known CKD patients on renal replacement therapy, 9 patients on hemodialysis and one on continuous ambulatory peritoneal dialysis (CAPD) all clinically labeled as case of PUO and subsequently referred for 18 F-fluorodeoxy glucose (FDG) positron emission tomography-computed tomography (PET CT) from Department of Nephrology. Following, standard guidelines for patient preparation and data acquisition, PET CT performed in all patients on Biograph 06, PET CT scanner, PET CT images reviewed and reported jointly by radiologist and nuclear medicine physician.

Results: In all 10 patients, PET CT scan detected one or multiple metabolically active lesions in body. These were involving lymph nodes, bones, spleen, adrenal gland, lung and intestinal lesions in descending order. Histo-pathological diagnosis was possible in 8/10 patients, from one of the approachable lymph node or bone lesion. In remaining two patients, no histo-pathological evaluation performed, as in one patient CT lung of PET CT scan clearly revealed milliary tuberculosis and multiple mediastinal lymph nodes which were difficult to sample by FNAC and in other one patient, a metabolically active lesion detected in ilio-caecal region, for further characterization of this lesion, patients refused to co-operate for any invasive procedure. All patients, treated appropriate antibiotics or anti tubercular drugs and responded clinically to the given treatment.

Conclusion: 18F-FDG PET CT survey of body highly sensitive test, can provide high yield in localization of hidden infection in body, and reduce the morbidity and mortality in affected patients.

GS Shagos, Shanmuga Sundaram Palaniswamy, Padma Subramanyam, Ajith Kumar Varma¹

Departments of Nuclear Medicine and PET CT, and ¹Podiatry, Amrita Institute of Medical Sciences, Kochi, Kerala, India

Objectives: We attempted to compare the diagnostic accuracies of three phase bone scan (TPBS) and FDG PET-CT (FDG PET) in the evaluation of complicated diabetic foot.

Materials and Methods: 36 diabetic patients, (M: F, 27:09, age range 44-73 years [mean age 58.7]),with clinical suspicion of pedal osteomyelitis were prospectively investigated between July 2010 and 2012. TPBS (15 mci MDP IV) performed followed by FDG PET (5 mci IV) within 05 days in all patients. Findings were assessed by two nuclear medicine physicians. Interpretation was based on intensity, extent, pattern of MDP and FDG uptake (SUV). CT correlation was used for localisation. Bone/soft tissue culture and sensitivity was considered as the gold standard for diagnostic correlation. All patients followed up for 6 months.

Results: In the study Gp, n = 36, osteomyelitis: cellulitis were 19:17 by FDG PET and 27:9 for TPBS respectively. Of the 36 patients, culture and sensitivity were available for 23 patients. 13 patients whose culture was not available were not included in calculating sensitivity and specificity. In diagnosing osteomyelitis, TP: TN:FP: FN were 14:5:2:2 by FDG PET-CT- and 13:02:05:03 by TPBS respectively. Sensitivity, specificity, PPV and NPV of FDG PET were 87.5%, 71%, 87.5% and 71% and for TPBS were 81.25%, 28.5%, 72% and 40% respectively. Though MDP uptake was noted in bones in many patients in TPBS, many of them showed FDG uptake restricted to soft tissue than in bones showing high sensitivity, but low specificity of TPBS.

Conclusion: FDG PET-CT has higher specificity and positive predictive value than TPBS in diagnosing osteomyelitis in complicated diabetic foot. By excluding osteomyelitis, FDG PET due to its higher negative predictive value can help to spare patients from more aggressive surgical management. FDG PET-CT alone can be considered in the place of TPBS in complicated diabetic foot evaluation.

Shashwat Verma, Sanjay Gambhir, Prasanta Kumar Pradhan, Sukanta Barai, Amitabh Arya

Department of Nuclear Medicine, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India

Objective: 2-deoxy-2-(18F) fluoro-D-glucose positron emission tomography/computed tomography (18F- FDG PET/CT) has now become an established imaging tool in oncology. It is now emerging in the field of infectious diseases. The objective of this study was to assess the value of 18F-FDG PET/CT in investigating patients with pyrexia of unknown origin (PUO).

Materials and Methods: After proper patient preparation and informed consent, a total of 36 referred patients (24 men, 12 women, with age range 21-63 years) underwent 18F-FDG-PET/CT for evaluation of pyrexia of unknown origin. All examinations were performed using dedicated LSO PET-CT scanner in 3-D mode, 60 min after i.v. injection of 370 MBq of 18F-FDG. No IV contrast was given. Reconstruction of the acquired data was performed so as to obtain fused PET-CT images in transaxial, coronal and sagittal views.

Results: Twenty three out of 36 patients showed foci of increased FDG uptake in the whole body image thus helping in diagnosis and localising the active focus of disease. Remaining 13 patients did not show any area of abnormal FDG uptake. The sensitivity of 18F-FDG PET/CT for identifying the cause of PUO was 63.88%.

Conclusion: 18F-FDG PET/CT in addition to contribution towards the diagnosis also helped in localization of disease. Our results suggest that 18F-FDG PET/CT may be used as an initial non-invasive diagnostic modality for assessment of patients with pyrexia of unknown origin.

BP Tiwari, P Kand, R Ranade

Radiation Medicine Centre (BARC), Tata Memorial Centre Annexe, Parel, Mumbai, Maharashtra, India

Objective: Cardiac FDG PET study is conducted to evaluate hibernating status in perfusion defects at rest evident on myocardial perfusion study. FDG uptake of myocardium is affected by various factors with inadequate results obtained in myocardial FDG PET study. We studied myocardial FDG uptake at different times after injection to investigate the usefulness of delayed imaging.

Materials and Methods: Twenty patients (18 male +2 female, age range 27-71 years) with coronary artery disease showing perfusion defect at rest on myocardial perfusion imaging were referred for cardiac FDG PET. Patients underwent myocardial FDG PET imaging as usual at 1 h. Further additional imaging was performed at 2 h and 4 h post FDG injection. We calculated FDG activity concentration in defective myocardial segments (as per myocardial perfusion imaging) as well as in whole heart for the images taken at different intervals each time by SUVmax in ROI. An ROI was drawn over liver region and SUVmax was noted for background. Mean value of SUVmax obtained for diabetic (9) and non-diabetic (11) patients were grouped together for comparison.

Results: In non-diabetic patients mean of SUVmax was 7.26 (3.46-12.03), 9.43 (5.04-12.13) and 10.43 (4.4-15.57) at 1 h, 2 h and 4 h respectively for regions showing defect. Global SUVmax in these patients at these time intervals was 11.79 (5.45-14.83), 14.14 (9.1-16.2) and 14.76 (5.67-17.26) respectively. In diabetic group only global SUVmax could be calculated for one patient. In other 3 diabetic patients, regional defect could not be identified on 1 h image. Mean SUVmax of defective regions in 5 patients was 5.52 (4.35-7.34) at 1 h. Mean SUVMax for 8 patients in defective regions at 2 h and 4 h was 5.81 (2.24-8.7) and 6.86 (2.55-10.94) respectively. Global SUVmax for diabetic patients was found to be 7.13 (3.45-10.93), 9.81 (4.75- 17.32) and 12.05 (5.7-22.25) at 1 h, 2 h and 4 h respectively. There was no significant change in liver SUVmax in all cases.

Conclusion: Progressive increase in FDG concentration is noted in the myocardium resulting in delayed PET showed higher SUVmax values at 4 h in both diabetic and non-diabetic patients. Delayed studies in myocardial FDG PET may provide incremental value over conventional protocol in assessment of hibernating myocardium in perfusion defects noted at rest.

Swasti Dixit, Deepti Rathod, Sujith Rai, Anand Zade, B Rajashekharrao, A Velumani

Nuclear Healthcare Ltd. 4/1A, Sector 23, Kopar Khairane,Navi Mumbai, Maharashtra, India

Objective: ¹⁸F-FDG PET-CT scan has found wide applications in oncology, neurology and cardiology. Though introduced in clinical practice for over a decade, the data on the whole body retention of ¹⁸F-FDG at different time intervals is limited. This study was performed to assess the whole body ¹⁸F-FDG retention using the 1 m external dose rates data measured at different time intervals.

Materials and Methods: This prospective study was performed on 21 consecutive patients referred for whole body ¹⁸F-FDG PET-CT scan. 5 MBq/kg of ¹⁸F-FDG was injected intravenously. The dose rate at a distance of 1 m was recorded both anteriorly and posteriorly, using G.M. Survey meter (S.E. International, Model: Radiation alert inspector). The readings were recorded immediately after the injection, prior to imaging (45-60 min post-injection) and 90-105 min after the injection. Decay corrected retention of the ¹⁸F- FDG was computed from the geometric mean of the readings obtained at these time intervals.

Results: The 1 m dose rate measured at 0, 45-60 and 90-105 min post- injection ranged from 1.98 to 4.70, 1.05-2.69 and 0.65-1.28 mR/h respectively with a mean (± SD) of 3.11 (±0.73), 1.69 (±0.42), 0.94 (±0.25) and median of 3.2, 1.69 and 0.90 mR/h respectively. The mean (±SD) percentage whole body retention of ¹⁸F-FDG calculated from the dose rate data at 45-60 min and 90-105 min post-injection was observed to be 72.71 (±9.2) % and 53.9 (±10.03)% respectively.

Conclusion: The whole body retention data of ¹⁸F-FDG would be useful for modeling effective dose calculations to the patient, comforters and members of the public.

Akanksha Jindal, Anupam Mathur¹, Haladhar D Sarma², Usha Pandey, Ashutosh Dash

Isotope Applications and Radiopharmaceuticals Division, ²Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, ¹Board of Radiation and Isotope Technology, Mumbai, Maharashtra, India

Objective: [11C]-palmitate is used clinically for myocardial PET imaging. However, the short half-life (20 min) of [11C] and complicated radiolabeling protocol produces low yields of the final radiopharmaceutical. Therefore, we aimed to prepare ⁶⁸Ga-labeled fatty acids as substitutes for [11C]-palmitate, since ⁶⁸Ga with a half-life of 67.71 min, is available from a ⁶⁸Ge/⁶⁸Ga generator and is known to form high yielding complexes with convenient chemistry.

Materials and Methods: The desired fatty acid conjugates were synthesized by reaction of p-SCN-benzyl NOTA with the ω-amino group of 11-aminoundecanoic acid and 12-aminododecanoic acid, respectively. Both the derivatives were radiolabeled with ⁶⁸Ga in acetate buffer. Characterisation of the complexes as well as determination of radiochemical yields was done by HPLC. Bioevaluation studies were carried out in Swiss mice to assess their potential for myocardial imaging.

Results: Both the ⁶⁸Ga labeled fatty acid complexes could be prepared in >90% yields. Biodistribution studies in Swiss mice showed reasonable myocardial uptake at 2 min for both the derivatives (7 ± 2.75% ID/g for 11-carbon fatty acid-NOTA conjugate and 6 ± 2.12% ID/g for 12-carbon fatty acid-NOTA conjugate). Initial uptake was followed by rapid clearance of the activity from the target organ over time, as expected for long chain fatty acids. The complexes cleared rapidly from the other organs via the hepatic route.

Conclusions: The significant heart uptake of the ⁶⁸Ga labeled fatty acid complexes and their rapid clearance from non-target organs makes them potential candidates for dynamic myocardial imaging. Further studies are underway to establish their clinical utility.

K Ganesh Kadiyala, Anupriya Adhikari, Kanchan Chauhan, M Thirumal, AK Mishra, Anupama Datta

Division of Cyclotron and Radiopharmaceutical Sciences, Institute of Nuclear Medicine and Allied Sciences, DRDO, Delhi, India

Aim: Positron emission tomography is one of most common non-invasive technique in the field of molecular imaging. Breast cancer is the most prevalent form of diagnosed cancer in women and is the second leading cause of death in women. ER+ concentration is high in cancer cells when compared to healthy cells, this is one of the early indication of cancer. One way to determine the ER+ of cells would be to image breast tumors, using positron emission tomography (PET). Estradiol is the most active endogenous estrogen, and its derivatives are used by millions of women in hormone replacement therapy. E₂CF₃ was synthesized and the conditions for the labelling with ¹⁸F were optimized. The ligand was finally labelled with 18F to evaluate its potential for ER+ tumor imaging through Positron Emission Tomography technique.

Materials and Methods: Synthesis of desired probe was performed using estrogen derivative, 17α-ethynylestradiol as precursor. The 17α-ethynyl-estradiol was derivatized by click chemistry to give 15-(1-(2-aminoethyl)-1H-1,2,3-triazol-4-yl)-14-methyl-7,8,9,11,12,13,14,15,16,17-decahydro-6H-cyclopenta[a]phenanthrene-2,15-diol (Est-NH₂). The obtained Est-NH₂ was converted to the ligand E₂CF₃ through a multistep reaction. The conditions to radiolabel it with ¹⁸F through nucleophilic reaction approach were optimized. Post cold labelling the compound was characterized with spectroscopic techniques.

Results: Synthesized compounds were characterized by NMR and mass spectroscopy. Radiolabeling efficiency with ¹⁸F was found to be >84% and serum stability indicated that ¹⁸F remained bound to E₂CF₃ upto 4 h.

Conclusion: The desired compound was synthesized through click reaction in high yield (>90%) and initial studies suggested that the E₂CF₃ can be further explored for ER+ targeted PET imaging for breast cancer.