Subramanyam Padma

PET/CT in the evaluation of anti-NMDA-receptor encephalitis: What we need to know as a NM physician

Anti N-methyl-D-aspartate receptor encephalitis (ANMDARE), also known as limbic encephalitis (LE), is a treatable rare disorder characterized by personality changes, irritability, depression, seizures, memory loss and sometimes dementia. It is classified under paraneoplastic syndrome (PNS) and produces antibodies against NR1 and NR2 subunits of glutamate aspartate receptor. It is thought to be closely related with malignancies like small cell lung cancer, ovarian teratoma and Hodgkins lymphoma, apart from testis, breast and rarely gastric malignancies. Non-paraneoplastic encephalitis cases are the ones with no detectable malignancy and may be triggered by severe infection. As nuclear medicine physicians, we must be aware of the diverse presentation of ANMDARE or LE and should include a whole body positron emission tomography / computed tomography (PET/CT) and not just brain PETCT during imaging. We describe the first case of PET/CT in an idiopathic ANMDARE Indian adolescent girl.

Role of positron emission tomography computed tomography in carcinoma lung evaluation

Lung cancer has graduated from merely a reportable disease of 1912 to being the most common cause of cancer death in developed countries in recent years. The annual number of lung cancer deaths is greater than the combined cancer deaths from breast, colon and prostate. Its association with tobacco has been proved and is related to the type, amount of tobacco used, the age at initiation and duration of use. Significant advances have been made in the diagnosis and management of lung cancer over the past decade. The primary treatment of lung cancer is surgery and the best chance for a complete cure comes from the total resection of localized disease. Once nodal or distant metastases have developed, primary surgical intervention is ruled out and patient is considered for adjuvant chemotherapy with or without radiation therapy. Accurate staging and delineation of disease extent is therefore critical in the treatment planning of lung carcinoma patients. 18 F fluoro deoxy glucose (FDG) positron emission tomography (PET) has been proven to be a valuable noninvasive imaging modality in the evaluation of patients with known or suspected lung cancer and its integration with computed tomography (CT) has changed the face of PET imaging in many ways. This article will review the current role of FDG PET CT in the evaluation of pulmonary nodules, diagnosis, staging and restaging of non-small-cell lung carcinoma (NSCLC), role of PET in small cell lung Carcinoma (Ca), pleural disease and will also discuss its potential future applications.

Evolution of Damage in Near α IMI-834 Titanium Alloy Under Monotonic Loading Condition: A Continuum Damage Mechanics Approach

In the present work, a continuum damage mechanics model, based on Lemaitre’s concept of equivalent stress hypothesis (1986, “Local Approach to Fracture ,” Eng. Fract. Mech., 25, pp. 523–537), has been applied to study the evolution of damage under monotonic loading condition in a near α IMI-834 titanium alloy, used for aeroengine components in compressor module. The damage model parameters have been experimentally identified by in situ measurement of damage during monotonic deformation using alternating current potential drop technique. The damage model has been applied to predict damage evolution in an axisymmetrically notched specimen using finite element analysis. A reasonably good agreement has been observed between numerically simulated and experimentally measured damage behaviors. Damage micromechanisms operative in this alloy have also been identified which show multiple damage events.

18-F flourodeoxy glucose positron emission tomography-computed tomography imaging: A viable alternative to three phase bone scan in evaluating diabetic foot complications?

Background: This paper is based on the initial findings from a prospective ongoing study to evaluate the efficacy of flourodeoxy glucose positron emission tomography-computed tomography (FDG-PET CT) in diabetic foot evaluation. Objective: The aim was to compare the diagnostic accuracies of three phase bone scan (TPBS) and FDG PET-CT (FDG-PET) in diabetic foot evaluation. Methods: Seventy-nine patients with complicated diabetic foot (osteomyelitis/cellulitis, Charcots neuropathy) were prospectively investigated. TPBS (15 mci methylene di phosphonate [MDP] intravenous [IV]), followed by FDG-PET (5 mci IV) within 5 days were performed in all patients. Based on referral indication, patients grouped into Group I, n = 36, (?osteomyelitis/cellulitis) and Group II, n = 43 (?Charcots neuropathy). Interpretation was based on intensity, extent, pattern of MDP and FDG uptake (standardized uptake value) along with CT correlation. Findings were compared with final diagnostic outcome based on bone/soft tissue culture in Group I and clinical, radiological or scintigraphic followup in Group II. Results: Group I: For diagnosing osteomyelitis, TP: TN: FP: FN were 14:5:2:2 by FDG PET and 13:02:05:03 by TPBS respectively. Sensitivity, specificity, positive predictive value and negative predictive value (NPV) of FDG-PET were 87.5%, 71%, 87.5% and 71% and 81.25%, 28.5%, 72% and 40% for TPBS, respectively. Group II: charcots: cellulitis: Normal were 22:14:7 by FDG PET and 32:5:6 by TPBS, respectively. Conclusion: Flourodeoxy glucose PET-CT has a higher specificity and NPV than TPBS in diagnosing pedal osteomyelitis. TPBS, being highly sensitive is more useful than FDG-PET in detecting Charcots neuropathy.

Detection of atypical metastases in recurrent adenoid cystic carcinoma of parotid gland

We report a known case of adenoid cystic carcinoma of right parotid gland in a 36-year-old Indian male, diagnosed 5 years ago for which he underwent surgery followed by radiotherapy. Now the patient has presented to the surgical oncologist with a mass near angle of right jaw. Computed tomography (CT) performed elsewhere was reported negative for local recurrence. Subsequently, 18 F Fluorodeoxyglucose positron emission tomography-CT (FDG PET-CT) demonstrated local recurrence in right parotid bed. Surprisingly, metabolically active metastatic skeletal deposits were also identified, thus the disease was upstaged and management was changed. Trucut biopsy from left iliac bone lesion confirmed metastases from adenoid cystic carcinoma. Thus a whole body PET-CT has a significant impact on management of patients with salivary gland malignancies in assessing both local recurrence as well as distant metastases, especially in atypical and unsuspected sites.

Role of myocardial perfusion single photon emission computed tomography in pediatric cardiology practice.

Diagnostic and prognostic power of myocardial perfusion imaging in patients with coronary artery disease has been demonstrated with planar imaging which was further improvised with addition of gated SPECT and newer Technetium labeled myocardial perfusion tracers like SestaMIBI, Tetrofosmin. Myocardial perfusion abnormalities at rest and after stress are considered to be the best predictors of cardiac event–free survival in adults with ischemic heart disease. This article highlights various myocardial perfusion imaging (MPI) radiopharmaceuticals, exercise procedures, pharmacological stress protocols, indications for MPI and myocardial perfusion patterns in children with some of the common congenital and acquired heart diseases.

Cardiac fatty acid metabolism and ischemic memory imaging with nuclear medicine techniques.

There has been a dramatic improvement in the clinical management of myocardial diseases with the advent of cardiac metabolic and molecular imaging. Although both myocardial perfusion and metabolic imaging provide insight of myocardium at risk for infarction or ischemia, it is known that metabolic derangements precede perfusion abnormalities, especially after reperfusion therapy. Deranged myocyte loses its flexibility of choosing the right substrate for energy production and it switches its substrate, especially between fatty acid (FA) and glucose depending on disease condition; for example, predominance of FA metabolism is noted in diabetic heart disease, whereas glucose metabolism is enhanced in pressure overload conditions such as left ventricular hypertrophy. We thus hypothesize that with better technological advancements and different substrates, the metabolic footprint of various heart diseases can be charted out in future to help in the optimization of patient management. This review attempts to discuss the importance of radionuclide-labeled FAs in cardiac metabolic and ischemic memory imaging.

Current practice and recommendation for presurgical cardiac evaluation in patients undergoing noncardiac surgeries.

The increasing number of patients with coronary artery disease (CAD) undergoing major noncardiac surgery justifies guidelines concerning preoperative cardiac evaluation. This is compounded by increasing chances for a volatile perioperative period if the underlying cardiac problems are left uncorrected prior to major noncardiac surgeries. Preoperative cardiac evaluation requires the clinician to assess the patients probability to have CAD, severity and stability of CAD, placing these in perspective regarding the likelihood of a perioperative cardiac complication based on the planned surgical procedure. Coronary events like new onset ischemia, infarction, or revascularization, induce a high-risk period of 6 weeks, and an intermediate-risk period of 3 months before performing noncardiac surgery. This delay is unwarranted in cases where surgery is the mainstay of treatment. The objective of this review is to offer a comprehensive algorithm in the preoperative assessment of patients undergoing noncardiac surgery and highlight the importance of myocardial perfusion imaging in risk stratifying these patients.

Radioiodine as an adjuvant therapy and its role in follow-up of differentiated thyroid cancer

Papillary and follicular cancers of thyroid are the most common varieties of differentiated thyroid cancers exhibiting excellent long-term prognosis when carefully managed. Being a slow-growing malignancy, guidelines exist on the staging, preoperative risk stratification, and management of these cancers to increase the overall survival of these patients. Radioactive iodine has a central role in differentiated thyroid malignancies. It has the same physical properties as stable iodine, thus both normal and malignant thyrocytes cannot differentiate radioactive from stable iodine. Differentiated thyroid carcinoma (DTC) cells concentrate cytocidal amounts of Iodine -131 (131 I) by trapping (the function of the sodium iodine symporter, or NIS) and organifying the iodide ion to produce levothyroxine and triiodothyronine. We shall discuss the role of radioiodine in the management and followup of DTC patients.

PET/CT in paediatric malignancies - An update

18F-fluorodeoxyglucose positron emission tomography (FDG-PET) is a well-established imaging modality in adult oncological practice. Its role in childhood malignancies needs to be discussed as paediatric malignancies differ from adults in tumor subtypes and they have different tumor biology and FDG uptake patterns. This is also compounded by smaller body mass, dosimetric restrictions, and physiological factors that can affect the FDG uptake. It calls for careful planning of the PET study, preparing the child, the parents, and expertise of nuclear physicians in reporting pediatric positron emission tomography/computed tomography (PET/CT) studies. In a broad perspective, FDG-PET/CT has been used in staging, assessment of therapy response, identifying metastases and as a follow-up tool in a wide variety of pediatric malignancies. This review outlines the role of PET/CT in childhood malignancies other than hematological malignancies such as lymphoma and leukemia.