Abhinav Jaimini

Comparative evaluation of F-18 FDOPA, F-18 FDG, and F-18 FLT-PET/CT for metabolic imaging of low grade gliomas.

Introduction: We undertook this prospective study to compare amino acid metabolism, glucose metabolism, and proliferation in primary and recurrent low grade gliomas using positron emission tomography (PET)/computed tomography with F-18 FDOPA, F-18 FDG, and F-18 FLT. Methods: Fifteen patients with newly diagnosed or previously treated low grade gliomas (WHO grade I or II) were subjected to F-18-FDOPA, F-18 FDG, and F-18 FLT PET/computed tomography studies on consecutive days. This included 2 patients in remission as control subjects. Uptake of all the 3 tracers were analyzed visually and quantified using standardized uptake values and tumor to normal (T/N) ratios. The accuracy of all the 3 PET tracers in the detection of newly diagnosed and recurrent low grade gliomas was compared. Results: F-18 FDOPA was positive in all cases of primary and recurrent low grade gliomas and negative in the patients in remission. Tumor was visualized on F-18 FDG in 7 of 13 cases, F-18-FLT was positive in 4 of 13 cases. Average tumor standardized uptake values max for F-18 FDOPA (5.75 ± 4.9) and F-18 FLT (1.8 ± 0.91) was lower than that of F-18 FDG (8.5 ± 4.4). T/N ratios for F-18-FDOPA (2.3 ± 0.51) and F-18 FLT (1.8 ± 0.91) were higher than F-18 FDG (1.03 ± 0.64) providing good image contrast for tumor detection in positive cases. Conclusion: F-18 FDOPA scan is superior to both F-18 FLT and F-18 FDG for visualization of primary and recurrent low grade gliomas. F-18-FLT should not be considered for evaluation of recurrent low grade gliomas.

Comparison of F-18 FDG and C-11 methionine PET/CT for the evaluation of recurrent primary brain tumors.

Purpose of Study: With the availability of multiple positron emission tomography (PET) tracers for neurooncology, there is a need to define the appropriate tracer in a given clinical setting, and it is in this regard that we undertook this study to directly compare F-18 flurodeoxyglucose (FDG) PET and C-11 methionine (MET) PET for the evaluation of recurrence in primary brain tumors. Patients and Methods: Thirty-seven patients with a history of treated primary brain tumors referred for evaluation of recurrent disease were initially included in the study. Two patients had to be excluded because of insufficient follow-up. There were 23 males and 12 females, mean age: 33.7 ± 16.4 years; range: 5 to 65 years. All patients underwent the MET and FDG study on the same day. Visual image interpretation was performed independently by 2 PET physicians for each tracer using the plain PET and fused PET/CT images; the FDG images were evaluated first. Images were analyzed semiquantitatively using tumor to normal contralateral cortex ratios (T/N). Each patient was followed up for a minimum of 18 months. Imaging results were compared with histopathology on tumor excision or biopsy in 14 patients and with clinical follow-up and MRI/MRS at the end of 18 months in 21 patients. Results: The final diagnosis was tumor recurrence in 24 patients and no recurrence/stable disease in 11 patients. On FDG, findings in 15/35 (42%) were suggestive of recurrent tumors. On MET, findings in 24/34 (70.5%) cases were suggestive of recurrent tumors. Spatially separated secondary lesions including intraventricular deposits were clearly delineated in 5 cases, 3 were glioblastoma multiforme (GBM) and 2 were anaplastic astrocytomas. One of the secondary lesions was missed on FDG PET. Using a cutoff for T/N ratio on FDG of >0.75 to differentiate recurrence from no recurrence, sensitivity of FDG was 81.2% (confidence interval [CI] = 54.4%–96%), whereas specificity was 88.9% (CI = 51.8%–99.7%). Area under the curve was 0.819 (CI = 0.615–0.943), P = 0.0003. Using a cutoff for T/N ratio of >1.9 to differentiate recurrence from no recurrence, sensitivity of MET was 94.7% (CI = 74.0%–99.9%), whereas specificity was 88.89% (CI = 51.8%–99.7%). Area under the curve was 0.942 (CI = 0.785–0.995), P < 0.0001. Interobserver agreement, &kgr; coefficient, for MET was 0.93, suggesting good interobserver agreement, whereas for FDG, it was fair (0.23). Conclusions: MET should be the radiotracer of choice in the evaluation of recurrence of primary brain tumors because the sensitivity for detection and delineation of the possible recurrent tumor, as well as secondary deposits, is higher with MET. MET-PET is an easier technique to interpret, irrespective of the glioma grade, with less interobserver variability and straightforward localization of tumorous accumulation.

Prospective evaluation of CECT and 18F-FDG-PET/CT in detection of hepatic metastases.

ObjectivesThe purpose of this study was to evaluate the performance of 18F-fluorodeoxy-D-glucose (FDG)-PET/computed tomography (CT) and contrast-enhanced CT (CECT) in the detection and characterization of hepatic metastases. MethodsForty-five patients harboring an extrahepatic primary malignancy, with suspected hepatic metastases on clinical or ultrasonographic examination were enroled prospectively. Each patient underwent contrast-enhanced abdominal CT and 18F-FDG-PET/CT within 72 h of each other, reported by an experienced radiologist and nuclear medicine specialist, respectively in a blinded manner. CECT and PET-CT findings were compared and analyzed. Final diagnosis was based on histology and/or follow-up (ranging from 6 to 12 months). ResultsThe sensitivity and specificity of CECT in the detection of hepatic metastases was 87.9 and 16.7%, respectively, whereas that of PET/CT was 97 and 75%, respectively. This study showed the superiority of PET/CT over CECT in the detection of hepatic metastases, irrespective of the primary site. This was especially owing to the latters inability to reliably distinguish small (less than 15 mm) lesions as benign or malignant. ConclusionMany studies have been conducted on the impact of FDG-PET/CT in the evaluation of hepatic metastases, especially from colorectal primary. Very few prospective studies, however, have been conducted on its role in evaluation of hepatic metastases from nongastrointestinal primaries. Despite its superior performance, it cannot replace CECT for this purpose, owing to the low but definite risk of false positivity based on PET-CT findings alone. Inclusion of CECT in PET/CT protocols may enable us to achieve a higher diagnostic accuracy. This suggests the need for a large prospective study with serial evaluations and pathological correlation.

Differential Diagnosis of Neurodegenerative Dementias Using Metabolic Phenotypes on F-18 FDG PET/CT:

Positron emission tomography (PET) imaging with F-18 fluorodeoxyglucose (FDG) can be used as a downstream marker of neuronal injury, a hallmark of neurodegenerative dementias. Characteristic patterns of regional glucose metabolism have been used to classify the dementia subtypes, namely Alzheimers dementia (AD), frontotemporal dementia (FTD), diffuse Lewy body (DLBD) and vascular dementia (VD). We undertook this study to assess the utility of FDG-PET in the differential diagnosis of dementia subtypes. One hundred and twenty-five patients diagnosed with dementia were referred from cognitive disorders and memory clinics of speciality neurology centres for the FDG-PET study. Imaging-based diagnosis of dementia type was established in 101 patients by visual assessment of individual scans by a PET physician blinded to the clinical diagnosis. The results were compared with an 18-month follow-up clinical assessment made by the specialist neurologist. Concordance of visual evaluation of FDG-PET scans with clinical diagnosis of the dementia type was achieved in 90% of patients scanned. This concordance was 93.4% for AD, 88.8% for FTD, 66.6% for DLBD and 92.3% for the other dementia syndromes. FDG-PET performed after the initial work-up of dementias is useful for supporting the clinical diagnosis of dementia subtype.

Demonstration of diffuse leptomeningeal metastasis in a treated case of medulloblastoma with F-18 FDG PET/CT.

Abstract:A 20-year-old man diagnosed as a case of desmoplastic cerebellar medulloblastoma had undergone shunting of the lateral ventricles and resection of the mass followed by postoperative irradiation to the entire neuraxis. There was evidence of residual disease in the posterior fossa on craniosp

Acute and sub acute toxicity and efficacy studies of Hippophae rhamnoides based herbal antioxidant supplement

Objectives: Present study was carried out to evaluate acute and subacute toxicity and efficacy of Seabuckthorn (Hippophae rhamnoides) based herbal antioxidant supplement (HAOS). Materials and Methods: In vivo toxicity studies were performed in male balb ‘C’ mice by oral administration. Acute toxicity study was done at doses ranging from 2000 to 10 000 mg/ kg while in subacute studies, HAOS was given at doses of 2000, 4000, and 8000 mg/kg body weight. Animals were observed for any toxic sign and symptoms periodically. At completion of study animals were sacrificed; their hematological, biochemical parameters were analyzed and histopathology of vital organs was done. In vivo efficacy studies in human volunteers were done and the levels of vitamin A and Vitamin C in blood samples were analyzed in comparison to a similar commercially available formulation. Results: No mortality and any clinical signs of toxicity were found in HAOS administered group of animals. There were no significant alterations in hematological and biochemical parameters. Histopathological analysis of vital organs showed normal architecture in all the HAOS administered groups. Human studies showed an increase of 32% and 172% in Vitamin A and Vitamin C levels respectively in term of bioavailability. Conclusion: The data obtained indicate no toxicity of this antioxidant supplement up to the highest dose studied. Efficacy in terms of increased bioavailability of vitamin A and C in human volunteers indicates the clinical usefulness of the supplement.

FDG-PET/CT in lymphoma

Lymphomas are a heterogeneous group of diseases that arise from the constituent cells of the immune system or from their precursors. 18F-fludeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is now the cornerstone of staging procedures in the state-of-the-art management of Hodgkins disease and aggressive non-Hodgkins lymphoma. It plays an important role in staging, restaging, prognostication, planning appropriate treatment strategies, monitoring therapy, and detecting recurrence. However, its role in indolent lymphomas is still unclear and calls for further investigational trials. The protean PET/CT manifestations of lymphoma necessitate a familiarity with the spectrum of imaging findings to enable accurate diagnosis. A meticulous evaluation of PET/CT findings, an understanding of its role in the management of lymphomas, and knowledge of its limitations are mandatory for the optimal utilization of this technique.

Edetate calcium disodium nanoparticle dry powder inhalation: A novel approach against heavy metal decorporation

Objective was to develop and characterize nano-edetate calcium disodium (Ca-Na(2)EDTA) dry powder inhaler (DPI), and assess its in vitro and in vivo deposition using pharmacoscintigraphy techniques. Factors influencing nanoparticle formation including concentration of drug, polymer solution and stirring rate were determined. Optimized formulation was characterized with the help of SEM, TEM and Malvern Zetasizer studies. Any change in physical characteristics after nanosizing was determined by FT-IR, XRD and DSC studies. Anderson cascade impaction showed that nano Ca-Na(2)EDTA exhibited significantly higher respirable fraction of 67.35±2.27% and 66.40±2.87% by scintigraphic and spectroscopic analysis respectively, as compared to 10.08±1.17% and 9.36±1.02% respectively for micronized form. Ventilation lung scintigraphy done in 12 volunteers showed significant increase in drug delivery till alveolar region with nano Ca-Na(2)EDTA. The developed formulation may have a role in neutralizing heavy metal toxicity through inhalation route, including radio-metal contamination.

Tuberculosis the great mimicker: 18F-fludeoxyglucose positron emission tomography/computed tomography in a case of atypical spinal tuberculosis.

Tuberculosis (TB) has aptly been called the great mimicker. A 14-year-old boy, who had been treated for Hodgkins Lymphoma 2 years back and had been in remission, underwent a whole body 18F-fludeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) scan, owing to a recent onset of backache and difficulty in walking. The study showed an FDG avid destructive lesion of the posterior elements of the sixth, seventh and eighth dorsal vertebrae along with a hypermetabolic collection in the adjacent paraspinal muscles with extension into the spinal canal, causing encasement of the thecal sac as well. Based on this constellation of findings, a diagnosis of atypical spinal TB was made, which was subsequently proven on histopathology. The present case illustrates that spinal TB, including the atypical form can be diagnosed on PET/CT even in clinically unsuspected cases.

A comparison study of 11 C-methionine and 18 F-fluorodeoxyglucose positron emission tomography-computed tomography scans in evaluation of patients with recurrent brain tumors

Introduction: 11 C-methonine ([11 C]-MET) positron emission tomography-computed tomography (PET-CT) is a well-established technique for evaluation of tumor for diagnosis and treatment planning in neurooncology. [ 11 C]-MET reflects amino acid transport and has been shown to be more sensitive than magnetic resonance imaging (MRI) in stereotactic biopsy planning. This study compared fluorodeoxyglucose (FDG) PET-CT and MET PET-CT in the detection of various brain tumors. Materials and Methods: Sixty-four subjects of brain tumor treated by surgery, chemotherapy, and/or radiotherapy were subjected to [ 18 F]-FDG, [ 11 C]-MET, and MRI scan. The lesion was analyzed semiquantitatively using tumor to normal contralateral ratio. The diagnosis was confirmed by surgery, stereotactic biopsy, clinical follow-up, MRI, or CT scans. Results: Tumor recurrence was found in 5 out of 22 patients on [F-18] FDG scan while [ 11 C]-MET was able to detect recurrence in 18 out of 22 patients in low-grade gliomas. Two of these patients were false positive for the presence of recurrence of tumor and later found to be harboring necrosis. Among oligodendroglioma, medulloblastoma and high-grade glioma out of 42 patients 39 were found to be concordant MET and FDG scans. On semiquantitative analysis, mean T/NT ratio was found to be 2.96 ± 0.94 for lesions positive for recurrence of tumors and 1.18 ± 0.74 for lesions negative for recurrence of tumor on [ 11 C]-MET scan. While the ratio for FDG scan on semiquantitative analysis was found to be 2.05 ± 1.04 for lesions positive for recurrence of tumors and 0.52 ± 0.15 for lesions negative for recurrence of tumors. Conclusion: The study highlight that [ 11 C]-MET is superior to [ 18 F]-FDG PET scans to detect recurrence in low-grade glioma. A cut-off value of target to nontarget value of 1.47 is a useful parameter to distinguish benign from malignant lesion on an [ 11 C]-MET Scan. Both [ 18 F]-FDG and [ 11 C]-MET scans were found to be useful in high-grade astrocytoma, oligodendroglioma, and medulloblastoma.