Understanding the linear and nonlinear optical responses of few-layer exfoliated MoS2and WS2nanoflakes: experimental and simulation studies.

Understanding the linear and nonlinear optical (NLO) responses of two-dimensional nanomaterials is essential to effectively utilize them in various optoelectronic applications. Here, few-layer MoS2and WS2nanoflakes with lateral size less than 200 nm were prepared by liquid-phase exfoliation, and their linear and NLO responses were studied simultaneously using experimental measurements and theoretical simulations. Finite-difference time-domain (FDTD) simulations confirmed the redshift in the excitonic transitions when the thickness was increased above 10 nm indicating the layer-number dependent bandgap of nanoflakes. WS2nanoflakes exhibited around 5 times higher absorption to scattering cross-section ratio than MoS2nanoflakes at various wavelengths. Open aperture Z scan analysis of both the MoS2and WS2nanoflakes using 532 nm nanosecond laser pulses reveals strong nonlinear absorption activity with effective nonlinear absorption coefficient (ßeff) of 120 cm GW-1and 180 cm GW-1, respectively, which was attributed to the combined contributions of ground, singlet excited and triplet excited state absorption. FDTD simulation results also showed the signature of strong absorption density of few layer nanoflakes which may be account for their excellent NLO characteristics. Optical limiting threshold values of MoS2and WS2nanoflakes were obtained as ∼1.96 J cm-2and 0.88 J cm-2, respectively, which are better than many of the reported values. Intensity dependent switching from saturable absorption (SA) to reverse SA was also observed for MoS2nanoflakes when the laser intensity increased from 0.14 to 0.27 GW cm-2. The present study provides valuable information to improve the selection of two-dimensional nanomaterials for the design of highly efficient linear and nonlinear optoelectronic devices.

Defect mediated improved charge carrier dynamics in hybrid bulk-heterojunction solar cell induced by phase pure iron pyrite nanocubes.

In this article, the synthesis of phase pure iron pyrite nanocubes (FeS2NCs) and their various effects on the charge carrier dynamics and photovoltaic performances of P3HT:PC71BM based hybrid bulk-heterojunction solar cells have been studied. The optimum doping concentration of FeS2NCs was found to be 0.3 wt%. For the optimally doped devices, the short-circuit current density was found to have improved from 5.47 to 7.99 mA cm-2leading to an overall cell efficiency improvement from 2.10% to 3.22% as compared to the undoped reference devices. The enhancement in photovoltaic performance is mainly attributed to the formation of localized energy states near the band edges leading to higher carrier generation rate by 72% whereas carrier dissociation probability is also increased by 13%. Urbach energy estimation reveals that the optimally doped devices have achieved a relatively balanced amount of localized states resulting in reduced non-radiative recombination. Such localized defect states formation with FeS2NCs doping was also found to have significant influence over the charge carrier dynamics of the active layer. Transient photocurrent and photovoltage studies revealed that FeS2NCs assist in faster carrier extraction by reducing the transport time from 1.4 to 0.6µs and by enhancing carrier recombination time from 51.7 to 78.9µs for the reference and optimum devices respectively. Such an unorthodox approach of defect state assisted efficiency improvement demonstrates the importance of simultaneously understanding the charge carrier dynamics and photovoltaic performance for rational device optimization, and opens new prospects for developing high-efficiency solution processable hybrid devices.

Somatostatin receptor based PET/CT imaging with 68Ga-DOTA-Nal3-octreotide for localization of clinically and biochemically suspected insulinoma.

BACKGROUND: Localization of primary tumor in insulinoma is often difficult. We evaluated the role of 68Ga-DOTA-Nal3-Octreotide (DOTANOC) PET/CT for localization of primary tumor in patients with clinical and biochemical suspicion of insulinoma. METHODS: Data of 35 patients (age: 38.4±16.5 years) who underwent 68Ga-DOTANOC PET/CT for clinical and biochemical suspicion of insulinoma (hypoglycemia, raised serum insulin and C-peptide levels) were retrospectively analyzed. PET/CT images were evaluated visually and semiquantitatively (SUV) by two experienced nuclear medicine physicians. A definite lesion in pancreas on non contrast CT showing increased 68Ga-DOTANOC was taken as positive. In the absence of CT lesion focal 68Ga-DOTANOC uptake in the pancreas more than liver was taken as positive. All patients had also undergone conventional imaging (CIM) (CT/MRI/endosonography) and their reports were retrieved for comparison. Histopathology and/or imaging/clinical/biochemical follow up (minimum 6 months) was used as reference standard. RESULTS: The mean serum insulin levels was 51.6±54 µIU/mL and C-peptide level was 6.9±7.3 ng/mL. 68Ga-DOTANOC PET/CT was interpreted as positive in 11 patients (31.5%) and negative in 24 (68.5%). PET/CT demonstrated total 16 pancreatic lesions in 11 patients. In two patients it also showed both liver and lymph nodal metastases. 68Ga-DOTANOC PET/CT was true positive in 8, true negative in 1, false positive in 3 and false negative in 23 patients. Per patient based sensitivity of PET/CT was 25.8% (95% CI: 11.8-44.6), specificity was 25% (95% CI: 0.6-80.5) and accuracy was 25.7%. The mean SUVmax of pancreatic lesions was 13.8±11.1. On comparison no significant difference was seen between CIM and PET/CT on patient based (P=1.00) or lesion based comparison (P=0.790). CONCLUSION: 68Ga-DOTANOC PET/CT has limited utility for localizing the primary tumor in patients with clinical and biochemical suspicion of insulinoma. However, it might be useful for differentiating benign and malignant insulinoma. Further prospective comparative studies are warranted.

Surgical Scar Site Recurrence in Patients With Cervical Cancer on 18F-FDG PET-CT: A Case-Control Study.

PURPOSE: The purpose of this study was to assess the role of fluorine 18 ((18)F)-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG PET-CT) in evaluating various parameters in patients with surgical scar site recurrence in cervical carcinoma. METHODS: Data of all patients with cervical cancer (n = 329) who underwent PET-CT at our institute between 2005 and 2013 was reviewed. Of these 329 patients, 132 patients who were surgically treated and underwent restaging/follow-up PET-CT were included in the present study for final analysis. Tumor recurrence at the abdominal surgical scar site was looked for. Abnormal uptakes suggestive of active disease at other sites were also noted. Maximum standardized uptake value was measured for all the lesions. Patients with scar site recurrence were taken as cases (n = 6), whereas the remaining patients served as controls (n = 126). Comparison with conventional imaging modalities was made wherever available. Histopathological examination was always sought for. RESULTS: The incidence of scar site recurrence after surgery was found to be 4.5% (6/117). A total of 56 of 132 patients had recurrent disease, including 6 patients with scar site recurrence. All of the patients with scar site recurrence also had recurrent disease at other sites (local, nodal, or distant). Conventional imaging modalities were available in 4 of these 6 patients and detected scar site recurrence in 3 of those 4 patients. In patients with scar site recurrence, the mean ± SD time to scar site recurrence was 14.0 ± 10.9 months (median, 10 months; range, 7-36 months). Significant difference was seen between cases and control for International Federation of Genecology and Oncology stage (P = 0.001) and nodal recurrence (P = 0.007). Additionally, age, nodal recurrence, distant recurrence, and scar site recurrence were significantly associated with death. CONCLUSIONS: Scar site recurrence carries a poor prognosis, and the incidence is much higher than previously known when PET-CT is used as a modality for its detection.

Does perfusion pattern influence stress-induced changes in left ventricular mechanical dyssynchrony on thallium-201-gated SPECT myocardial perfusion imaging?

BACKGROUND: The relationship between perfusion pattern and stress-induced changes in left ventricular mechanical dyssynchrony (LVMD) on stress-rest thallium-201-gated SPECT myocardial perfusion imaging (Tl-201 SPECT MPI) is not clear. The aim of the study is to assess the relation of perfusion pattern with stress-induced changes in LVMD on Tl-201 MPI. METHODS: Data of 194 patients who underwent exercise-rest Tl-201 MPI between January to December 2012 at our institute was retrospectively evaluated. Institute Ethical committee approval was obtained. Fifty patients who underwent Tl-201 MPI for suspected CAD and had normal LV perfusion and function on MPI were taken as normal group. Patients with perfusion abnormalities (n = 144) were divided into three groups: ischemia (n = 66), infarct (n = 32), and mixed group (n = 46; ischemia and infarct both). Summed stress score, summed rest score, summed difference score (SDS), and LV ejection fraction (EF) were evaluated. Two LVMD parameters, phase standard deviation (PSD) and phase histogram bandwidth (PHB), were assessed in post-stress and rest MPI images. ΔPSD (post-stress PSD - rest PSD) and ΔPHB (post-stress PHB - rest PHB) were calculated to measure stress-induced changes in LVMD. RESULTS: In all the groups, mean post-stress LVMD parameters were lower as compared to LVMD parameters at rest. Post-stress PSD was significantly lower than rest PSD in all groups. Similar trend was noted with PHB values also, but it was statistically significant in the normal and ischemia group only. Post-stress worsening of at least one of the LVMD parameters was noted in 28 patients and all these patients had perfusion abnormalities. But on subgroup analysis, no difference was found in proportion of patients showing post-stress worsening of LVMD between ischemia (13.6%), infarct (25%), and mixed (23.6%) groups. No significant correlation was found between ΔPSD/ΔPHB and ΔLVEF/SDS in any group. CONCLUSION: LV mechanical dyssynchrony parameters are smaller in post-exercise stress as compared to rest on Tl-201 MPI, regardless of perfusion pattern. Stress-induced worsening of LV dyssynchrony was observed only in patients with perfusion abnormalities, but this is not related to the type of perfusion abnormality.

Spectrum of Physiologic and Pathologic Skeletal Muscle (18)F-FDG Uptake on PET/CT.

OBJECTIVE: Skeletal muscle (18)F-FDG uptake on PET/CT can be either physiologic or related to a variety of different pathologic conditions. FDG PET/CT can be used for assessment of primary and metastatic tumors and infective or inflammatory conditions affecting the musculature. CONCLUSION: In this article, we describe the various causes and patterns of skeletal muscle FDG uptake. Familiarity with these patterns is essential for proper interpretation of clinical FDG PET/CT images.

Evaluation of (68)Ga-DOTANOC PET/CT imaging in a large exclusive population of pancreatic neuroendocrine tumors.

PURPOSE: To evaluate the diagnostic accuracy of (68)Ga-DOTANOC PET/CT imaging in a large exclusive population of pancreatic neuroendocrine tumors (NETs). METHODS: Data of 141 (mean age 46.2 ± 15.2 years) patients who underwent 178 (68)Ga-DOTANOC PET/CT studies for diagnosis/staging (n = 88) and restaging (n = 90) of pancreatic NET were retrospectively analyzed. PET/CT results were compared to conventional imaging (CIM) when available (n = 86). Histopathology and/or clinical/imaging follow-up (minimum 6 months) were used as reference standard. RESULTS: The overall sensitivity, specificity, and accuracy of (68)Ga-DOTANOC PET/CT were 85.7%, 79.1%, and 84.8%. The corresponding values were 73%, 50%, and 70.4% for diagnosis/staging groups and 98.6%, 100%, and 98.8% for restaging groups. The accuracy was significantly higher for restaging as compared to diagnosis/staging (P < 0.0001) and in non-insulinoma tumors than insulinomas (P < 0.0001). The SUVmax of primary tumors was significantly higher than metastatic lesions overall (P = 0.001), as well as in diagnosis/staging (P = 0.041) and restaging (P = 0.0003) subgroups. When available, CIM was less specific than (68)Ga-DOTANOC PET/CT (P < 0.001) and showed fewer lesions. CONCLUSIONS: (68)Ga-DOTANOC PET/CT is useful for diagnosis/staging and restaging of patients with pancreatic NET. It demonstrates more lesions compared to CIM and is more specific.

Prospective evaluation of (68)Ga-DOTANOC PET-CT in differentiated thyroid cancer patients with raised thyroglobulin and negative (131)I-whole body scan: comparison with (18)F-FDG PET-CT.

PURPOSE: The purpose of the study was to evaluate the role of (68)Ga-DOTANOC PET-CT in differentiated thyroid cancer (DTC) patients with negative (131)I-whole body scan (WBS) along with serially increasing serum thyroglobulin (Tg), and compare the same with (18)F-FDG PET-CT. METHODS: Sixty two DTC patients with serially rising Tg levels and negative (131)I-WBS were prospectively enrolled. All patients underwent (68)Ga-DOTANOC PET-CT and (18)F-FDG PET-CT within an interval of two weeks. PET-CT analysis was done on a per-patient basis, location wise and lesion wise. All PET-CT lesions were divided into four categories-local, nodal, pulmonary and skeletal. Histopathology and/or serial serum Tg level, clinical and imaging follow up (minimum-1 year) were used as a reference standard. RESULTS: Ga-DOTANOC PET-CT demonstrated disease in 40/62 (65 %) patients and (18)F-FDG PET-CT in 45/62 (72 %) patients, with no significant difference on McNemar analysis (p = 0.226). Per-patient sensitivity and specificity of (68)Ga-DOTANOC PET-CT was 78.4 %, 100 %, and for (18)F-FDG PET-CT was 86.3 %, 90.9 %, respectively. Out of 186 lesions detected by both PET-CTs, 121/186 (65 %) lesions were seen on (68)Ga-DOTANOC PET-CT and 168/186 (90.3 %) lesions on (18)F-FDG PET-CT (p < 0.0001). There were 103/186 (55 %) lesions concordant on both. Excellent agreement was noted between (68)Ga-DOTANOC PET-CT and (18)F-FDG PET-CT for detection of local disease (ĸ = 0.92), while moderate agreement was noted for nodal and pulmonary disease (ĸ = 0.67). (68)Ga-DOTANOC PET-CT changed management in 21/62 (34 %) patients and (18)F-FDG PET-CT in 17/62 (27 %) patients. CONCLUSION: Ga-DOTANOC PET-CT is inferior to (18)F-FDG PET-CT on lesion based but not on patient based analysis for detection of recurrent/residual disease in DTC patients with negative WBS scan and elevated serum Tg levels. It can also help in selection of potential candidates for peptide receptor radionuclide therapy.

Diagnostic accuracy of (68)Ga-DOTANOC PET/CT imaging in pheochromocytoma.

PURPOSE: The purpose of the present study was to evaluate the diagnostic accuracy of (68)Ga-DOTANOC positron emission tomography (PET)/CT in patients with suspicion of pheochromocytoma. METHODS: Data of 62 patients [age 34.3 ± 16.1 years, 14 with multiple endocrine neoplasia type 2 (MEN2)] with clinical/biochemical suspicion of pheochromocytoma and suspicious adrenal lesion on contrast CT (n = 70), who had undergone (68)Ga-DOTANOC PET/CT, were retrospectively analyzed. PET/CT images were analyzed visually as well as semiquantitatively, with measurement of maximum standardized uptake value (SUVmax), SUVmean, SUVmax/SUVliver, and SUVmean/SUVliver. Results of PET/CT were compared with (131)I-metaiodobenzylguanidine (MIBG) imaging, which was available in 40 patients (45 lesions). Histopathology and/or imaging/clinical/biochemical follow-up (minimum 6 months) was used as reference standard. RESULTS: The sensitivity, specificity, and accuracy of (68)Ga-DOTANOC PET/CT was 90.4, 85, and 88.7%, respectively, on patient-based analysis and 92, 85, and 90%, respectively, on lesion-based analysis. (68)Ga-DOTANOC PET/CT showed 100% accuracy in patients with MEN2 syndrome and malignant pheochromocytoma. On direct comparison, lesion-based accuracy of (68)Ga-DOTANOC PET/CT for pheochromocytoma was significantly higher than (131)I-MIBG imaging (91.1 vs 66.6%, p = 0.035). SUVmax was higher for pheochromocytomas than other adrenal lesions (p = 0.005), MEN2-associated vs sporadic pheochromocytoma (p = 0.012), but no difference was seen between benign vs malignant pheochromocytoma (p = 0.269). CONCLUSION: (68)Ga-DOTANOC PET/CT shows high diagnostic accuracy in patients with suspicion of pheochromocytoma and is superior to (131)I-MIBG imaging for this purpose. Best results of (68)Ga-DOTANOC PET/CT are seen in patients with MEN2-associated and malignant pheochromocytoma.

Comparison of the prognostic values of 68Ga-DOTANOC PET/CT and 18F-FDG PET/CT in patients with well-differentiated neuroendocrine tumor.

PURPOSE: To determine the prognostic value of (68)Ga-DOTANOC PET/CT in patients with well-differentiated neuroendocrine tumor (NET), and to compare the prognostic value with that of (18)F-FDG PET/CT and other conventional clinicopathological prognostic factors. METHODS: Data from 37 consecutive patients (age 46.6 ± 13.5 years, 51% men) with well-differentiated NET who underwent (68)Ga-DOTANOC PET/CT and (18)F-FDG PET/CT were analyzed. All patients underwent a baseline visit with laboratory and radiological examinations. Clinical and imaging follow-up was performed in all patients. Progression-free survival (PFS) was measured from the date of the first PET/CT scan to the first documentation of progression of disease. RESULTS: (68)Ga-DOTANOC PET/CT was positive in 37 of the 37 patients and (18)F-FDG PET/CT was positive in 21. During follow-up 10 patients (27%) showed progression of disease and 27 (73%) showed no progression (24 stable disease, 3 partial response). The median follow-up was 25 months (range 2 - 52 months). Among the variables evaluated none was significantly different between the progressive disease and nonprogressive disease groups, with only SUVmax on (68)Ga-DOTANOC PET/CT being borderline significant (P = 0.073). In the univariate analysis for PFS outcome, SUVmax on (68)Ga-DOTANOC PET/CT (HR 0.122, 95% CI 0.019 - 0.779; P = 0.026) and histopathological tumor grade (HR 4.238, 95% CI 1.058 - 16.976; P = 0.041) were found to be associated with PFS. Other factors including age, sex, primary site, Ki-67 index, TNM stage, (18)F-FDG PET/CT status (positive/negative), SUVmax on (18)F-FDG PET/CT and type of treatment were not significant. In multivariable analysis, only SUVmax on (68)Ga-DOTANOC PET/CT was found to be an independent positive predictor of PFS (HR 0.122, 95% CI 0.019 - 0.779; P = 0.026). CONCLUSION: SUVmax measured on (68)Ga-DOTANOC PET/CT is an independent, positive prognostic factor in patients with well-differentiated NET and is superior to SUVmax on (18)F-FDG PET/CT and conventional clinicopathological factors for predicting PFS.

Diagnostic accuracy of ¹8F-FDG PET/CT for detection of suspected recurrence in patients with oesophageal carcinoma.

PURPOSE: To evaluate the role of (18)F-FDG PET/CT in the detection of recurrence in patients with oesophageal carcinoma, suspected clinically or following conventional investigations. METHODS: This was a retrospective study. Data from 180 patients (age 56.3 ± 10.4 years; 126 men, 54 women) with histopathologically proven oesophageal carcinoma (squamous cell 115, adenocarcinoma 59, neuroendocrine carcinoma 4, small cell 1, poorly differentiated 1) who had undergone 227 (18)F-FDG PET/CT studies for suspected recurrence were analysed. Recurrence was suspected clinically or following conventional investigations. PET/CT images were revaluated by two nuclear medicine physicians in consensus. Findings were grouped into local, nodal and distant recurrence. Results were compared to those from contrast-enhanced (CE) CT when available (109 patients). Clinical/imaging follow-up (minimum 6 months) with histopathology (when available) was taken as the reference standard. RESULTS: Of the 227 (18)F-FDG PET/CT studies,166 were positive and 61 were negative for recurrent disease. PET/CT showed local recurrence in 134, nodal recurrence in 115 and distant recurrence in 47, with more than one site of recurrence in 34. The PET/CT findings were true-positive in 153 studies, true-negative in 54, false-positive in 13 and false-negative in 7. The sensitivity of (18)F-FDG PET/CT was 96%, the specificity was 81%, the positive and negative predictive values were 92% and 89%, respectively, and the accuracy was 91%. PET/CT showed similar accuracy in patients with squamous cell carcinoma and in those with adenocarcinoma (P = 0.181).(18)F-FDG PET/CT was more specific than CECT (67% vs. 21%; P < 0.0001). PET/CT was superior to CECT for the detection of nodal recurrence (P < 0.0001), but not local recurrence (P = 0.093) or distant metastases (P = 0.441). CONCLUSION: (18)F-FDG PET/CT shows high accuracy in the detection of suspected recurrence in patients with oesophageal carcinoma. It is more specific than and is superior to CECT in the detection of nodal recurrence.

Potential role of 18F-FDG PET/CT in patients with fungal infections.

OBJECTIVE: Combined anatomic and functional imaging with (18)F-FDG PET/CT is slowly gaining foothold in the management of various infective pathologic abnormalities. However, limited literature is available regarding the role of FDG PET/CT in patients with fungal infections. CONCLUSION: Here, we briefly review the available literature and highlight the potential role that FDG PET/CT can play in the diagnosis and management of fungal infections.

Perfusion-metabolism coupling in recurrent gliomas: a prospective validation study with 13N-ammonia and 18F-fluorodeoxyglucose PET/CT.

INTRODUCTION: We assessed the validity of "perfusion-metabolism coupling" hypothesis in recurrent glioma with 13N-ammonia (13N-NH3) PET/CT and 18F-fluorodeoxyglucose (18F-FDG) PET/CT. METHODS: Fifty-six consecutive patients (age, 38.8 ± 12.1 years; 62.5% males) with histologically proven and previously treated glioma presenting with clinical suspicion of recurrence were prospectively enrolled and evaluated with 13N-NH3 PET/CT and 18F-FDG PET/CT. PET/CT images were evaluated both qualitatively and semiquantitatively. Tumor to white matter uptake ratio (T/W) and tumor to gray matter uptake ratio (T/G) were calculated and analyzed for both the modalities. A combination of clinico-radiological follow-up, repeated imaging, and biopsy (when available) were considered as the reference standard. RESULTS: Based on the reference standard, 27/56 patients had recurrence. 13N-NH3 PET/CT and 18F-FDG PET/CT were concordant in 55/56 patients. Overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 13N-NH3PET/CT were 77.8, 86.2, 84.0, 80.7, and 82.1%, respectively, and for 18F-FDG PET/CT were 77.8, 89.7, 87.5, 81.2, and 83.9%, respectively. There was excellent agreement between results of 13N-NH3 PET/CT and 18F-FDG PET/CT (ĸ = 0.964; P < 0.001). The performances of 13N-NH3 PET/CT and 18F-FDG PET/CT were not significantly different between high-grade and low-grade glioma (P = 1.000). A strong positive correlation was noted between the uptake ratios derived on the two modalities (ρ = 0.866, P < 0.001 for T/W; ρ = 0.918, P < 0.001 for T/G). CONCLUSION: A combination of 13N-NH3 PET/CT and 18F-FDG PET/CT demonstrates that perfusion and metabolism are coupled in recurrent gliomas. These tracers target two different but interrelated aspects of the same pathologic process and can be used as surrogates for each other.

Prospective evaluation of 18F-fluorodeoxyglucose positron emission tomography-computed tomography for response evaluation in recurrent carcinoma cervix: does metabolic response predict survival?

PURPOSE: This study aimed to assess the role of (18)F-fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG PET-CT) in response assessment of patients with recurrent carcinoma cervix and in evaluating the predictive value of metabolic response for progression-free survival (PFS) and overall survival (OS). METHODS: Thirty-six patients with histopathologically or clinically evident recurrent cervical carcinoma underwent a pretherapy and a posttherapy (18)F-FDG PET-CT for treatment response evaluation. Positron emission tomography-CT images were analyzed by 2 experienced nuclear medicine physicians. Response was categorized using European Organization for Research and Treatment of Cancer (EORTC) criteria into complete metabolic response (CMR), partial metabolic response (PMR), stable metabolic disease (SMD), and progressive metabolic disease (PMD). Clinical/imaging follow-up (minimum of 6 months) and/or histopathologic findings were taken as reference standard. Patients were categorized into 2 groups, those with PMD and those without PMD (ie, CMR, PMR, and SMD). Progression-free survival and OS based on PET-CT response were measured from the date of posttherapy PET-CT to the first documentation of progression of disease and death, respectively. RESULTS: On the basis of metabolic response on posttherapy PET-CT, 6 patients had CMR, 12 patients had PMR, 7 patients had SMD, and 11 patients had PMD. Progression-free survival for patients with cervical carcinoma ranged from 0.5 to 26.5 months (mean [SD], 6.7 [6.1] months). Median PFS for patients with PMD was 3.1 months, whereas median PFS for those without PMD was not reached. Patients who did not show PMD on posttherapy PET-CT had a significantly better PFS than those patients who showed PMD (P < 0.0001; HR, 0.14). There was no statistically significant difference in OS between the 2 groups (P = 0.187; HR, 0.39). CONCLUSIONS: (18)F-fluorodeoxyglucose PET-CT is an effective tool for treatment response evaluation in recurrent carcinoma cervix. Patients with metabolically progressive disease on posttherapy (18)F-FDG PET-CT have a significantly shorter PFS.

Production of the PET bone agent (18)F-fluoride ion, simultaneously with (18)F-FDG by a single run of the medical cyclotron with minimal radiation exposure- a novel technique.

Our aim was to establish an easy and convenient procedure for the preparation of fluorine-18-sodium fluoride ((18)F-NaF) for bone positron emission tomography (PET) during routine (18)F-FDG production using the Explora FDG4 radiochemistry module (EFRM) by single run of Cyclotron with negligible radiation exposure. We compared three techniques for (18)F-NaF production during routine PET radiochemistry at our setup. In one method we used synthesis module and in other two methods we did not. In the first and third method, F-18 was directly extracted from the V-vial and in the second method, (18)F-NaF was extracted by post processing from the EFRM. In the first method, F-18 was extracted directly from V-vial manually by opening the V-vial cap. In the second method, Explora FDG-4 Module was used. First, F-18 was transferred from the V-vial. Then, after post processing in EFRM, pure F-18 was obtained in the product vial. In the third method, pure F-18 was obtained in the product vial with the help of a mechanical robotic arm. The above were followed by routine quality control of (18)F-NaF produced by each method. Results of quality control of the (18)F-NaF obtained by all three methods satisfied all parameters prescribed by the United States Pharmacopeia (USP) and the British Pharmacopeia (BP) including biological, physical and chemical specifications. The radiochemical purity was 98.5±1.5% with Rf 0.006. The level of Kryptofix-222 (K222) in (18)F-NaF was within the prescribed limit. Mean pH of (18)F-NaF was 6.0±1.5. The exposure rate around the hot cell was negligible. In conclusion, from the results it was obvious that by our method number three (18)F-NaF was directly obtained from the V-vial using mechanical robotic arms. This method was the most appropriate with minimized radiation exposure to the handling Radiochemist and was also saving time as compared to the other two methods.

18F-FDOPA PET/CT for detection of recurrence in patients with glioma: prospective comparison with 18F-FDG PET/CT.

PURPOSE: Differentiation between recurrence and radiation necrosis in patients with glioma is crucial, since the two entities have completely different management and prognosis. The purpose of the present study was to compare the efficacies of (18)F-FDG PET/CT and 3,4-dihydroxy-6-[(18)F]fluoro-phenylalanine ((18)F-FDOPA) PET/CT in detection of recurrent gliomas. METHODS: A total of 28 patients (age 38.82 ± 1.25 years; 85.7% men) with histopathologically proven glioma with clinical/imaging suspicion of recurrence were evaluated using (18)F-FDG PET/CT and (18)F-FDOPA PET/CT. (18)F-FDG PET/CT and (18)F-FDOPA PET/CT images were evaluated qualitatively and semiquantitatively. The combination of clinical follow-up, repeat imaging and/or biopsy (when available) was taken as the reference standard. RESULTS: Based on the reference standard, 21 patients were positive and 7 were negative for tumour recurrence. The sensitivity, specificity and accuracy of (18)F-FDG PET/CT were 47.6%, 100% and 60.7%, respectively, and those of (18)F-FDOPA PET/CT were 100%, 85.7% and 96.4%, respectively. The results of (18)F-FDG PET/CT and (18)F-FDOPA PET/CT were concordant in 57.1% of patients (16 of 28) and discordant in 42.9% (12 of 28). The difference in the findings between (18)F-FDG PET/CT and (18)F-FDOPA PET/CT was significant (P = 0.0005, McNemar's test). The difference was significant for low-grade tumours (P = 0.0039) but not for high-grade tumours (P = 0.250). CONCLUSION: (18)F-FDOPA PET/CT is highly sensitive and specific for detection of recurrence in glioma patients. It is superior to (18)F-FDG PET/CT for this purpose and is especially advantageous in patients with low-grade gliomas.

Diagnostic accuracy of 18F-FDG PET/CT for detecting recurrence in patients with primary skeletal Ewing sarcoma.

PURPOSE: To evaluate the diagnostic accuracy of (18)F-FDG PET/CT for detecting recurrence in patients with primary skeletal Ewing sarcoma. METHODS: We retrospectively analysed data from 53 patients (age 20.1 ± 10.5 years, 39 male) who had undergone 71 (18)F-FDG PET/CT studies for suspected recurrence (52 studies) or for routine follow-up (19 studies) after primary therapy of skeletal Ewing sarcoma. (18)F-FDG PET/CT studies were evaluated qualitatively and quantitatively (maximum standardized uptake value, SUVmax) by two nuclear medicine physicians in consensus. Sensitivity, specificity, predictive values and accuracy were calculated on per study basis. Clinical/imaging follow-up (minimum 6 months) and/or histopathology (when available) were taken as the reference standard. RESULTS: Of the total of 71 (18)F-FDG PET/CT studies, 42 (59.1%) were positive for recurrence and 29 (40.9%) were negative for recurrence. Local recurrence was most common (38 studies) followed by bone metastasis (9 studies), and node and lung metastasis (2 studies each). Of the 71 studies, 38 were true-positive, 27 were true-negative, 4 were false-positive and 2 were false-negative. Overall per study based sensitivity was 95%, specificity was 87%, PPV was 90%, NPV was 93% and accuracy was 91.5%. No significant difference was found in the accuracy of PET/CT between the suspected recurrence group and the routine follow-up group (94% vs. 84%; P = 0.390). Overall mean lesion SUVmax was 7.8 ± 4.1 (range 1.9-17.2). No site-based difference was found in SUVmax. CONCLUSION: (18)F-FDG PET/CT demonstrates high diagnostic accuracy for detecting recurrence in patients with primary skeletal Ewing sarcoma, when it is suspected (clinically or on imaging) or during routine follow-up.

Comparative diagnostic accuracy of contrast-enhanced MRI and (18)F-FDOPA PET-CT in recurrent glioma.

OBJECTIVES: To compare the diagnostic accuracy of contrast enhanced magnetic resonance imaging (Ce-MRI) and (18)F-fluorodopa ((18)F-FDOPA) positron emission tomography (PET)-computed tomography (CT) for detecting recurrent glioma. METHODS: In this prospective study, 35 patients (age, 36.62 ± 0.86 years; 80 % male) with histopathologically proven glioma with clinical suspicion of recurrence were evaluated using Ce-MRI and (18)F-FDOPA PET-CT. (18)F-FDOPA PET-CT images were evaluated qualitatively and semi-quantitatively. Combination of clinical follow-up (minimum 1 year), repeat imaging and/or biopsy (when available) was taken as the reference standard. RESULTS: Based on the reference standard, 26 patients were positive and nine were negative for recurrence. The sensitivity, specificity and accuracy of Ce-MRI were 92.3 %, 44.4 % and 80 % respectively, whereas those of (18)F-FDOPA PET-CT were 100 %, 88.89 % and 97.1 % respectively. Results of Ce-MRI and (18)F-FDOPA PET-CT were concordant in 74.3 % (29/35) and discordant in 17.1 % of patients (6/35). On McNemar analysis the difference was not statistically significant overall (P = 0.687), for high-grade tumour (P = 0.5) or low-grade tumours (P = 1.0). However, (18)F-FDOPA PET-CT was more specific than Ce-MRI overall (P = 0.0002), for high-grade tumour (P = 0.006) and low-grade tumours (P = 0.004). CONCLUSION: F-FDOPA PET-CT shows a high but comparable diagnostic accuracy to Ce-MRI for the detection of recurrent glioma. However, it is more specific than Ce-MRI. KEY POINTS: • Recurrent glioma in the postoperative site remains a diagnostic dilemma. • (18) F-FDOPA PET-CT shows high diagnostic accuracy for detecting recurrent glioma. • Diagnostic accuracies for (18) F-FDOPA PET-CT and contrast enhanced MRI are comparable. • However, (18) F-FDOPA PET-CT is more specific than Ce-MRI for recurrent glioma.

Quantitative assessment of cardiac mechanical synchrony using equilibrium radionuclide angiography.

BACKGROUND: Data on normal parameters of cardiac mechanical synchrony is limited, variable and obtained from small cohorts till date. In most studies, software used for such assessment has not been mentioned. The aim of study is to establish normal values of mechanical synchrony with equilibrium radionuclide angiography (ERNA) in a larger population using commercially available software. METHODS: We retrospectively analysed ERNA studies of 108 patients having low pretest likelihood of coronary artery disease, no known history of cardiac disease, normal electrocardiogram and whose ERNA studies were considered normal by experienced observers. In addition, ten patients diagnosed with dilated cardiomyopathy (DCM) and having LVEF ≤ 40% underwent ERNA. Fourier first harmonic analysis of phase images was used to quantify synchrony parameters using commercially available software (XT-ERNA). Intraventricular synchrony for each ventricle was measured as the standard deviation of the LV and RV mean phase angles (SD LVmPA and SD RVmPA, respectively). Interventricular synchrony was measured as LV-RVmPA. Absolute interventricular delay was calculated as absolute difference between LV and RVmPA (without considering ± sign). All variables were expressed in milliseconds (ms) and degree (°). Intra-observer and inter-observer variabilities were assessed. Cut-off values for parameters were calculated from the normal database, and validated against patient group. RESULTS: On phase analysis, LVmPA was observed to be 343 ± 48.5 milliseconds (174.7° ± 18.5°), SD LVmPA was 16.3 ± 5.4 milliseconds (8.2° ± 2.5°), RVmPA was 339 ± 50.4 milliseconds (171.8° ± 18.5°) and SD RVmPA was 37.3 ± 15.7 milliseconds (18.7° ± 7.2°). LV-RVmPA was observed to be 3.9 ± 21.7 milliseconds (2.9° ± 9.6°) and absolute interventricular delay was 16.3 ± 14.8 milliseconds (7.9° ± 6.1°). The cut-off values for the presence of dyssynchrony were estimated as SD LVmPA > 27.1 milliseconds (>13.2°), SD RVmPA > 68.7 milliseconds (>33.1°) and LV-RVmPA > 47.3 milliseconds (>22.1°). There was no statistically significant intra-observer or inter-observer variability. Using these cut offs, 9 patients with DCM showed the presence of left intraventricular dyssynchrony, 5 had right intraventricular dyssynchrony and 2 had interventricular dyssynchrony. CONCLUSIONS: ERNA phase analysis offers an objective and reproducible tool to quantify cardiac mechanical synchrony using commercially available software and can be used in routine clinical practice to assess mechanical dyssynchrony.

Somatostatin receptor-based PET/CT of intracranial tumors: a potential area of application for 68 Ga-DOTA peptides?

OBJECTIVE: Similar to neuroendocrine tumors (NETs) at other sites, a wide array of intracranial tumors also express somatostatin receptors (SSTRs). This expression can be exploited for both imaging and therapy. The introduction of (68)Ga-labeled tetraazacyclododecanetetraacetic acid (DOTA)-peptide PET/CT has given new dimension to SSTR-based imaging because of its improved sensitivity and excellent spatial resolution. CONCLUSION: However, in contrast to gastropancreatic and bronchopulmonary NETs, limited literature is available regarding the use of (68)Ga-DOTA-peptide PET/CT in intracranial tumors. Here, we briefly review the available literature and highlight the potential role that (68)Ga-DOTA-peptide PET/CT can play in the management of intracranial tumors.