Sampath Santhosh

Role of 18F-fluorodeoxyglucose positron emission tomography/computed tomography in the characterization of pancreatic masses: Experience from tropics

Early detection and differentiation of malignant from benign pancreatic tumors is very essential as mass‐forming pancreatitis is a frequently encountered problem. Positron emission tomography (PET) has a role in establishing the diagnosis of pancreatic carcinoma when the conventional imaging modalities or biopsies are nondiagnostic. In this prospective study, the utility of fluorodeoxyglucose (FDG)‐PET/computed tomography (CT) in the characterization of mass‐forming lesions of the pancreas was reported.

Added value of Spect/ct over planar Tc-99m mebrofenin hepatobiliary scintigraphy in the evaluation of bile leaks

ObjectiveTo determine the added value of single-photon emission computed tomography/computed tomography (SPECT/CT) over planar hepatobiliary scintigraphy (HBS) in suspected cases of bile leak. Materials and methodsAn analysis of the data of all patients who had undergone HBS for suspected bile leak during the last 3 years was carried out. All patients had undergone an initial 45 min dynamic study after an intravenous injection of Tc-99m mebrofenin, following which they underwent multiple static imaging studies for up to 24 h and SPECT/CT imaging whenever needed. ResultsA total of 203 patients had undergone an HBS for evaluation of a suspected bile leak. HBS was positive for bile leak in 110 patients, among whom 42 had undergone additional SPECT/CT. In 32 patients SPECT/CT was useful in (i) defining the exact location of collection [intracapsular vs. extracapsular vs. intraparenchymal leak (n=18/25)], (ii) defining the extent of intraparenchymal collections (n=6/6), (iii) characterizing large abdominal collections (n=2/2), and (iv) characterizing suspected contamination (n=4/4), (v) suspected collection (n=0/3), (vi) and other miscellaneous conditions (n=2/2). Defining the extent and exact localization of collection can have therapeutic implications such as the accurate site of placement of the drain for drainage. In approximately one-third of the bile leak-positive HBS studies (32/110), SPECT/CT images were helpful for better characterization of biliary collection. In all, 76% (32/42) of the SPECT/CT studies were found to provide additional useful information over planar imaging. ConclusionHybrid SPECT/CT offers the unique advantage of combining the anatomical information from CT with the functional information provided by HBS. It is most useful in characterization of biliary collections, which give important scintigraphic evidence of the severity of bile leak with therapeutic implications such as placement of a drain or surgical exploration.

Comparison of LVEF assessed by 2D echocardiography, gated blood pool SPECT, 99mTc tetrofosmin gated SPECT, and 18F-FDG gated PET with ERNV in patients with CAD and severe LV dysfunction.

IntroductionLeft ventricular ejection fraction (LVEF) is the single most important predictor of prognosis in patients with coronary artery disease (CAD) and left ventricular (LV) dysfunction. Equilibrium radionuclide ventriculography (ERNV) is considered the most reliable technique for assessing LVEF. Most of these patients undergo two dimensional (2D) echocardiography and myocardial viability study using gated myocardial perfusion imaging (MPI) or gated 18F-fluorodeoxyglucose (18F-FDG) PET. However, the accuracy of LVEF assessed by these methods is not clear. This study has been designed to assess the correlation and agreement between the LVEF measured by 2D echocardiography, gated blood pool single photon emission computed tomography (SPECT), 99mTc tetrofosmin gated SPECT, and 18F-FDG gated PET with ERNV in CAD patients with severe LV dysfunction. Patients and methodsPatients with CAD and severe LV dysfunction [ejection fraction (EF) <35 assessed by 2D echocardiography] were prospectively included in the study. These patients underwent ERNV along with gated blood pool SPECT, 99mTc tetrofosmin gated SPECT, and 18F-FDG gated PET as per the standard protocol for myocardial viability assessment and LVEF calculation. Spearman’s coefficient of correlation (r) was calculated for the different sets of values with significance level kept at a P-value less than 0.05. Bland–Altman plots were inspected to visually assess the between-agreement measurements from different methods. ResultsForty-one patients were prospectively included. LVEF calculated by various radionuclide methods showed good correlation with ERNV as follows: gated blood pool SPECT, r=0.92; MPI gated SPECT, r=0.85; and 18F-FDG gated PET, r=0.76. However, the correlation between 2D echocardiography and ERNV was poor (r=0.520). The Bland–Altman plot for LVEF measured by all radionuclide methods showed good agreement with ERNV. However, agreement between 2D echocardiography and ERNV is poor, as most of the values in this plot gave a negative difference for low EF and a positive difference for high EF. The mean difference between various techniques [2D echocardiography (a), gated blood pool SPECT (b), MPI gated SPECT (c), 18F-FDG gated PET (d)] and ERNV (e) was as follows: (a)−(e), 3.3; (b)−(e), 5; (c)−(e), 1.1; and (d)−(e), 2.9. The best possible correlation and agreement was found between MPI gated SPECT and ERNV. ConclusionThis study showed good correlation and agreement between MPI gated SPECT and 18F-FDG gated PET with ERNV for LVEF calculation in CAD patients with severe LV dysfunction. Thus, subjecting patients who undergo viability assessment by MPI gated SPECT or 18F-FDG gated PET to a separate procedure like ERNV for LVEF assessment may not be warranted. As the gated blood pool SPECT also showed good correlation and agreement with ERNV for LVEF assessment in CAD patients with severe LV dysfunction, with better characteristics than ERNV, it can be routinely used whenever accurate LVEF assessment is needed.

Pancreatic tuberculosis: Evaluation of therapeutic response using F-18 fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography

F-18 fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (FDG PET/CT) is a functional imaging technique that monitors glucose metabolism in tissues. Pulmonary tuberculosis (TB) has been reported to show intense uptake of FDG, with a decrease in metabolism of the tuberculous lesions after successful anti-tubercular treatment (ATT). The authors present a patient with pancreatic TB and demonstrate the usefulness of FDG PET/CT in monitoring the response to ATT.

Role of F-18 fluorodeoxyglucose positron emission tomography/computed tomography in the detection of recurrence in patients with cervical cancer

Introduction: Treatment of cervical cancer is usually surgery in the early stages and radiotherapy or chemoradiotherapy in more advanced stages of the disease. Recurrence may occur in multiple sites following primary treatment. Although recurrent metastatic disease is not curable, surgical treatment may be of great help if locoregional recurrence is detected early. Fluorine-18 Fluorodeoxyglucose positron emission tomography - computed tomography (F-18 FDG PET/CT) forms an important part of investigations in the diagnosis of clinically suspicious recurrent cervical cancer. Objective: To assess the role of F-18 FDG PET/CT in diagnosing recurrence in patients with clinical suspicion of recurrent cervical cancer. Materials and Methods: We retrospectively evaluated 53 histopathologically proved patients of cervical cancer. All the patients had been treated with either surgery/radiation therapy with or without chemotherapy. The standard PET/CT acquisition protocol, with delayed post void static pelvic images, wherever required, was followed in all patients. Significant uptake of FDG in the lymph nodes was considered to be a recurrence suggestive of metastasis. Para-aortic lymph nodal involvement was considered to be distant metastasis. Any significant uptake in the lung nodule on FDG PET was evaluated either by histological confirmation, by taking fine needle aspiration cytology (FNAC), or by a follow-up chest CT done after three months. Results: Of the 53 patients with clinically equivocal recurrence, FDG PET/CT suggested recurrence in 41 patients (local recurrence in 14 patients and distant recurrence/metastasis with or without local recurrence in 27 patients). It had a sensitivity of 97.5%, a specificity of 63.6%, positive predictive value of 90.9%, and negative predictive value of 87.5%. Conclusion: PET/CT appears to have an important role in detecting recurrence following primary treatment of cervical cancer. The high positive and negative predictive values of PET/CT may be helpful in planning management of recurrent cervical cancer.

Plasmacytoma of the ovary: additional role of 18F-FDG PET/CT.

We report a case of ovarian plasmacytomas where 18F-FDG PET/CT helped in staging by demonstrating increased FDG uptake limited to the ovary, and hence, surgical treatment was carried out as the disease was localized to the ovary.

Metabolic signatures of malignant and non-malignant mass-forming lesions in the periampulla and pancreas in FDG PET/CT scan: an atlas with pathologic correlation.

Positron emission tomography (PET) has been used for the characterization of pancreatic and periampullary lesions. Pancreatitis-associated inflammation affecting only a portion of the pancreas gives the appearance of a mass lesion on imaging. Consequently, the differential diagnosis between cancer and pancreatitis becomes a commonly encountered problem. Traditionally, PET was interpreted as positive (to denote malignancy) if fluorodeoxyglucose (FDG) activity in the pancreas exceeded background activity and as negative (to denote benign) if activity was less than or equal to background activity. However, the specificity was limited with this method of interpretation. A relatively wide overlap has been reported between semiquantitative uptake values obtained in cancers and those in inflammatory lesions. Also, the qualitative (metabolic patterns) and quantitative variables (standardized uptake values) have been complementary and at sometimes controversial to each other in various clinical situations. There is paucity of data in the literature highlighting the role of FDG PET/CT in characterization of such mass lesions. The primary aim of this pictorial review is to list the various pathologic processes of pancreas and periampulla that could be studied with FDG PET/CT and recognize the different FDG uptake patterns and apply this information to characterize the different lesions affecting the pancreas and periampulla. We have also discussed the limitations of conventional imaging and advantages of FDG PET/CT for the evaluation mass-forming lesions of the pancreas and periampulla.

Role of 18F-FDG PET/CT in the management of a case of autoimmune pancreatitis with extrapancreatic manifestations.

Autoimmune pancreatitis and pancreatic cancer share many clinical features like advanced age, painless jaundice, weight loss, and elevated serum levels of CA 19-9. The authors report a 58-year-old male patient provisionally diagnosed with periampullary carcinoma on the basis of ultrasonography and serological markers and planned for Whipple resection. (18)F-FDG PET/CT findings were suggestive of autoimmune pancreatitis, subsequently confirmed on cytological diagnosis. The follow-up PET/CT scan after 1 week of steroid therapy showed regression of FDG uptake in most of the lesions with appearance of salivary gland uptake.

Three-phase skeletal scintigraphy in pachydermoperiostosis.

Pachydermoperiostosis or primary hypertrophic osteoarthropathy is a rare syndrome with diverse radiologic and clinical features. Though the diagnosis can be made on the basis of classic clinical radiologic features, it is often misdiagnosed due to the varied clinical presentations. We report a patient with pachydermoperiostosis in whom 3 phase skeletal scintigraphy played a significant role in establishing the diagnosis.

Nuclear medicine imaging in osteonecrosis of hip: Old and current concepts

Osteonecrosis (ON) is caused by inadequate blood supply leading to bone death, which results in the collapse of the architectural bony structure. Femoral head is the most common site involved in ON. Magnetic resonance imaging (MRI) is a commonly used imaging modality to detect early ON. When MRI is inconclusive, bone scan is helpful in detecting ON during early phase of the disease. As newer nuclear medicine equipment, like single photon emission computed tomography/computed tomography (CT) and positron emission tomography/CT, are emerging in medical science, we review the role of these imaging modalities in ON of femoral head.