18F-FDG 18F-FDG Positron Emission Tomography Imaging of Cortical Reorganization in Spinal Trauma.

Objective: Spinal cord injury (SCI) extensively impacts the sensorimotor reorganization in the brain. The effects can be both anatomical and functional. To date, not many studies using 18F-Fluoro-2-Deoxyglucose positron emission tomography (18F-FDG PET) to evaluate metabolic changes in the brain are done. Understanding such changes is crucial for developing clinical management and evidence-based rehabilitation strategies for these patients. Subjects and Methods: In this study, we compared 18F-FDG PET imaging of 6 SCI patients with complete paraplegia and 19 controls. Statistical parametric mapping software was utilized to compare the images on a voxel to voxel basis (significance level P < 0.05 and clusters having >50 voxels). Results: The study showed raised metabolism in supplementary motor areas, comprehension centers, some areas in the parietal and temporal lobe, putamen and cerebellum while reduced metabolic uptake in areas like anterior cingulate gyrus, hippocampus and sensory cortical areas when SCI patients were compared against healthy controls. The frontal lobe showed varied results where certain regions showed higher metabolism while the others showed lower in patients compared with controls. Conclusion: Cerebral deafferentation or disuse atrophy can be linked with reduced metabolism while raised uptake can be associated with initiation and planning of movement and cognitive changes in the brain posttrauma.

Role of fluoroethyl tyrosine positron emission tomography-computed tomography scan in differentiating ewing's sarcoma from osteomyelitis.

Ewing's sarcoma is a kind of undifferentiated reticulocytic sarcoma, which was first reported in 1921 by James Ewing. It is difficult to differentiate Ewing's sarcoma from osteomyelitis on computed tomography (CT) and X-ray and hence cytological confirmation is needed. Fluorodeoxy glucose being a nonspecific tracer cannot differentiate between malignant and inflammatory lesions. However, it is found that Ewing's sarcoma has increased LAT1 transporter expression at the cell surface. This property has been utilized to specifically target the tumor cells and differentiate them from inflammatory lesions. 18F-fluoroethyl tyrosine (FET) is a radiotracer which shows increased uptake in tumors having LAT1 expression and no uptake in inflammatory lesions. Thus, FET positron emission tomography-computed tomography can serve as a useful tool in diagnosing recurrence or residual Ewing's sarcoma from infective pathology. Besides, it is also helpful in monitoring response to therapy.

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.

Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography imaging in response monitoring of extra-pulmonary tuberculosis.

Positron emission tomography/computed tomography (PET/CT) using 2-deoxy-2-(fluorine-18) fluoro-D-glucose ((18)F-FDG) has become a standard diagnostic modality in oncological practice. F18-FDG PET/CT is sensitive in detecting malignancy; however, specificity is low in differentiating infections or inflammatory diseases from tumor. In the present case study, we report a patient with postoperative carcinoma of tongue presenting with cervical lymphadenopathy and fever. The PET/CT scan showed metabolically active generalized lymphadenopathy, and a possibility of lymphoma was suggested. Fine needle aspiration cytology showed the Ziehl-Neelsen staining to be strongly positive for acid-fast bacilli and first line of antitubercular drug was administrated. Six months later after the initiation of therapy, a follow-up PET/CT showed remarkable improvement of the disease status. This case study illustrates that tubercular infection can be a pitfall in F18-FDG PET/CT imaging. PET positive lesions do not always indicate malignancy, and histological confirmation of lesions with biopsy should always be performed. Once diagnosed to be tubercular, FDG PET/CT is a powerful imaging tool in monitoring the therapy.

Utility of intrastriatal ratios of FDOPA to differentiate idiopathic Parkinson's disease from atypical parkinsonian disorders.

AIM: The striatal-to-occipital ratio (SOR) is commonly used as an analytical parameter in L-3,4-dihydroxy-6-18F-fluorophenylalanine (FDOPA) PET studies. It has been shown to be useful in differentiating idiopathic Parkinson's disease (IPD) patients from healthy individuals. We assessed the performance of SORs and subregional ratio of striatal-to-occipital ratios (RSORs) in the clinical assessment of nigrostriatal dopaminergic function for differentiating typical IPD from atypical parkinsonian disorders (APD). MATERIALS AND METHODS: A total of 117 patients referred from movement disorder clinics in speciality neurology centres underwent an FDOPA PET study and were kept under follow-up for at least 2 years. Sixty-five patients (43 IPD and 22 APD) completed the 2-year follow-up and were included in the final analysis. Their PET images were spatially normalized to occipital counts and analysed with three striatal subregional regions of interest (caudate, anterior putamen and posterior putamen) and two occipital regions of interest. The RSORs of the caudate and posterior putamen, the caudate and anterior putamen, the caudate and whole putamen and the anterior putamen and posterior putamen were also calculated and compared between the IPD and APD groups using the t-test. RESULTS: The P values for these SORs were found to be insignificant between IPD and APD patients (caudate: 0.1325; anterior putamem: 0.5469; and posterior putamen: 0.9835). However, the RSORs of the caudate and posterior putamen showed significant differences between these two populations of patients. CONCLUSION: The SOR method is already known to be a good diagnostic tool to differentiate between IPD patients and the normal population. SOR, however, fails to distinguish IPD from APD patients, and hence the RSOR of the caudate and posterior putamen can be utilized to differentiate between them.

Utility of gray-scale ultrasound to differentiate benign from malignant thyroid nodules.

OBJECTIVE: The objective was to assess the utility of gray-scale USG to identify patterns of thyroid nodules and to correlate the characteristics of benign and malignant nodules with pathological diagnosis. MATERIALS AND METHODS: From September 2009 to August 2010, a total of 203 patients (17 males and 186 females), with 240 nodules detected at USG, were included in this study. The characteristics of each nodule were determined. The results were then compared with fine needle aspiration (FNA)/histopathological diagnosis. RESULTS: Of the 240 nodules examined, 44 (18.33%) were found to be malignant on cytopathology. The malignant nodules demonstrated solid or predominantly solid composition (sensitivity 88.6%, specificity 53.5%); presence of microcalcification (sensitivity 65.9%, specificity 97.9%); irregular or poorly defined margins (sensitivity 84%, specificity 88.7%); anteroposterior (AP) diameter > transverse diameter (sensitivity 77.2%, specificity 80.1%); absent or thick incomplete halo (sensitivity 70.4%, specificity 65.8%); and markedly hypoechoic character (sensitivity 65.9%, specificity 84.6%). Among males, malignant nodules were found in 36.8%, whereas in females the occurrence was 16.7%. CONCLUSION: Gray-scale USG features of thyroid nodules are useful to distinguish patients with clinically significant thyroid nodules from those with innocuous nodules despite the overlap of findings. From our study, it is apparent that the USG findings of poorly defined margins, marked hypoechogenicity, microcalcifications, and a taller-than-wider shape have a high diagnostic accuracy for identifying malignant thyroid nodules.

Spectrum of neurocognitive dysfunction in Indian population on FDG PET/CT imaging.

BACKGROUND: A variety of neurodegenerative disorders produce significant abnormal brain function which can be detected using fluorodeoxyglucose positron emission tomography (FDG PET) scan even when structural changes are not detected on CT or MRI Scan. A study was undertaken at our institute to evaluate the FDG PET/CT findings in Indian population suffering from mild cognitive impairment (MCI), Alzheimer's disease (AD), fronto-temporal dementia (FTD), dementia with lewy body disease (DLBD) and other miscellaneous causes of dementia. MATERIALS AND METHODS: 117 subjects having neurocognitive deficits and 36 normals were included in our study. All patients underwent a detailed history and clinical examination. This was followed by a mini mental state examination. Subsequently an FDG brain PET scan and an MRI were done. RESULTS: In the patient population included in our study group 36 were normal, 39 had MCI, 40 had AD, 14 had FTD, and 13 had DLBD and 11 dementia due to other miscellaneous causes. MCI patients showed primarily reduced tracer uptake in the mesio-temporal cortex. AD patients showed reduced tracer concentration in temporo-parietal lobes, while patients with advanced diseases showed frontal lobe disease additionally. In subjects of FTD, reduced radiotracer uptake in the fronto-temporal lobes was noted. In addition, FTD patients also showed basal ganglia defects. In contrast the DLBD patients showed globally reduced FDG uptake including severely affecting the occipital cortices. CONCLUSION: In the current study the F18-FDG PET scans have been shown to be highly useful in the diagnosis of various neurocognitive disorders of the brain. AD was found to be the most common dementia in the Indian population followed by MCI. Diffuse Lewy body disease, FTD and other miscellaneous categories of dementia had a near similar incidence.