Anupam Mondal

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.

Differentiation of malignant and benign solitary thyroid nodules using 30- and 120-minute tc-99m MIBI scans.

Technetium-99m methoxy isobutylisonitrate (MIBI) has been found to be taken up by various tumors, including thyroid cancer. We prospectively evaluated 77 patients with cold thyroid solitary nodules on Tc-99m pertechnetate scintigraphy to evaluate the diagnostic value of Tc-99m MIBI scintigraphy. The aim of this study was to find out if thyroid nodules can be characterized on the basis of retention of MIBI and whether preoperative evaluation of malignancy is possible using this method. Single injection, dual-phase (30 and 120 minutes) thyroid scintigraphy using Tc-99m MIBI was performed in all these patients. In the following days and weeks, all patients underwent surgery. Using the 120/30-minute thyroid lesion to background radiouptake ratio (RUR), malignant and benign thyroid nodules could be separated with a sensitivity, specificity, and positive predictive value of 84.4%, 95.45%, and 93.33%, respectively. The mean RUR for malignant thyroid lesions was found to be 1.57 ± 0.32, whereas for benign lesions, the ratio was significantly lower, 0.32 ± 0.19. In conclusion, fine needle aspiration cytology along with the 120/30 minutes Tc-99m MIBI scintigraphy ratio appears to be useful in the preoperative assessment of solitary thyroid nodules.

11C-MET PET/CT and advanced MRI in the evaluation of tumor recurrence in high-grade gliomas.

Objectives The purpose of this study was to evaluate the performance of l-[methyl-(11)C]methionine (11C-MET) PET/CT and MRI (with the inclusion of advanced imaging techniques, namely, MR spectroscopy and MR perfusion) in the assessment of tumor recurrence in high-grade gliomas. Patients and Methods Twenty-nine patients with high-grade gliomas who underwent surgical resection, external beam radiation therapy, and standard regimens of chemotherapy were subjected to MRI (conventional, MR perfusion, and MR spectroscopy) and 11C-MET PET/CT scans. A definitive diagnosis was made based on histopathology and/or long-term clinical and radiological follow-up. Several indices were obtained for lesion characterization, namely, SUVmean, SUVmax, and mean lesion-to-normal tissue on PET/CT, as well as relative cerebral blood volume and choline-to-creatine ratio on MRI. Results Histological examination revealed viable tumor cells in 19 cases, whereas the remaining 10 were deemed to be negative based on histology (3 cases) or long-term follow-up (7 cases). All the quantitative indices mentioned previously tended to be higher in patients with tumor recurrence/residual. The sensitivity, specificity, and accuracy of 11C-MET PET/CT in identifying tumor recurrence/residual were 94.7%, 80%, and 89.6%, respectively, whereas that of MRI were 84.2%, 90%, and 86.2%, respectively. Conclusions Both 11C-MET PET/CT and MRI (with the inclusion of advanced MRI techniques) demonstrated a high diagnostic performance in the identification of tumor residual/recurrence in high-grade gliomas posttherapy. Although 11C-MET PET/CT seemed to be more sensitive, whereas advanced MRI seemed more specific, there was no statistically significant difference in the diagnostic performance of either modality in the present study. Further studies with a larger group of patients are warranted.

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.

Metastatic follicular carcinoma of the thyroid with tumor thrombus in the superior vena cava and right brachiocephalic and internal jugular veins: FDG-PET/CT findings.

Abstract:A 48-year-old woman who had undergone subtotal thyroidectomy with right modified neck dissection underwent F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) for assessing the extent of disease postoperatively (restaging). Biopsy was reported as follicular carcinoma thyroid. A

Hemiagenesis of the thyroid associated with chronic lymphocytic thyroiditis.

The authors report a case of hemiagenesis of the left thyroid lobe indicated on Tc-99m pertechnetate scan and later confirmed on ultrasonography. The patient was clinically hypothyroid with a right-sided goiter. The cytopathologic diagnosis was made by fine-needle aspiration cytologic analysis, which indicated chronic lymphocytic thyroiditis in the right lobe of the thyroid gland. Later the patient’s condition was stabilized with thyroxine replacement therapy. The association of hemiagenesis of the thyroid with chronic lymphocytic thyroiditis has not been reported in the literature.

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.

DNA flow cytometry and bladder irrigation cytology in detection of bladder carcinoma.

In this study we assessed the role of DNA flow cytometry (FCM) as an adjunct to bladder irrigation cytology to detect carcinoma of the bladder. We selected only those cases who had urinary symptoms and cystoscopic examination or histology‐proven cases of bladder cancer who underwent cystoscopy for a follow‐up study. Cystoscopy, cytologic examination, and DNA FCM were performed in every case. There were 9 fresh cases and 21 follow‐up cases of proven transitional‐cell carcinoma (TCC) of the bladder. Cystoscopy revealed growth in all 9 fresh cases as well as in 11 follow‐up cases. Cytology was positive in 16 cases, out of which there were 8 each of fresh and recurrent cases. None of the cases showed positive cytology with negative cystoscopy findings. DNA FCM was positive in 13 cases. Aneuploidy was detected in 5 cases, out of which there were 3 hyperdiploid and 2 hypodiploid cases. Nine cases had high (equal or more than 10%) S and G2‐M phase cells, ranging from 10–19.36%. One case showed aneuploidy along with high S‐G2M phase. Both cytology and DNA FCM were positive in 9 cases. In 2 cases, DNA FCM showed aneuploidy, but cytology and cystoscopy were negative. The sensitivity and specificity of the bladder wash cytology were 80% and 100%, and those for DNA FCM were 55% and 83.3%, respectively. We conclude that both bladder wash cytology and DNA FCM techniques should be done in all the cases of suspected TCC to detect more number of positive cases. Diagn. Cytopathol. 2001;24:153–156.

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