Vikram Lele

Current worldwide nuclear cardiology practices and radiation exposure: results from the 65 country IAEA Nuclear Cardiology Protocols Cross-Sectional Study (INCAPS)

Aims To characterize patient radiation doses from nuclear myocardial perfusion imaging (MPI) and the use of radiation-optimizing ‘best practices’ worldwide, and to evaluate the relationship between laboratory use of best practices and patient radiation dose. Methods and results We conducted an observational cross-sectional study of protocols used for all 7911 MPI studies performed in 308 nuclear cardiology laboratories in 65 countries for a single week in March–April 2013. Eight ‘best practices’ relating to radiation exposure were identified a priori by an expert committee, and a radiation-related quality index (QI) devised indicating the number of best practices used by a laboratory. Patient radiation effective dose (ED) ranged between 0.8 and 35.6 mSv (median 10.0 mSv). Average laboratory ED ranged from 2.2 to 24.4 mSv (median 10.4 mSv); only 91 (30%) laboratories achieved the median ED ≤ 9 mSv recommended by guidelines. Laboratory QIs ranged from 2 to 8 (median 5). Both ED and QI differed significantly between laboratories, countries, and world regions. The lowest median ED (8.0 mSv), in Europe, coincided with high best-practice adherence (mean laboratory QI 6.2). The highest doses (median 12.1 mSv) and low QI (4.9) occurred in Latin America. In hierarchical regression modelling, patients undergoing MPI at laboratories following more ‘best practices’ had lower EDs. Conclusion Marked worldwide variation exists in radiation safety practices pertaining to MPI, with targeted EDs currently achieved in a minority of laboratories. The significant relationship between best-practice implementation and lower doses indicates numerous opportunities to reduce radiation exposure from MPI globally.

Functional imaging in primary tumour-induced osteomalacia: relative performance of FDG PET/CT vs somatostatin receptor-based functional scans: a series of nine patients.

Localization of phosphatonin‐producing mesenchymal tumours in patients with primary tumour‐induced osteomalacia (pTIO) is challenging. Functional imaging plays an important role in the localization of these tumours.

Gastric mucosal blood flow and hepatic perfusion index in patients with portal hypertensive gastropathy

Endoscopic laser Doppler velocimetry is a simple non‐invasive method to measure gastric mucosal blood flow. The present study is an attempt to determine a correlation, if any, between gastric mucosal blood flow and the hepatic perfusion index in patients with portal hypertensive gastropathy and their relationship to the severity of liver disease. Thirty patients with portal hypertensive gastropathy due to cirrhosis of the liver (eight class A, 13 class B, nine class C, according to Child‐Pugh Classification) and six normal subjects were recruited into the study. In all subjects, the gastric mucosal blood flow and venous vasomotor reflex response was measured at two sites: the lesser and greater curvature, using endosoopic laser Doppler velocimetry. The hepatic perfusion index was measured using dynamic liver scintigraphy. The hepatic perfusion index (ratio of arterial/portal venous perfusion) in normal subjects and patients with portal hypertensive gastropathy belonging to Child‐Pugh class A, B and C were 0.36 ± 0.02, 0.53 ± 0.08, 0.62 ± 0.14 and 1.04 ± 0.28, respectively. The gastric mucosal blood flow was similar in Childs A, B and C cases, while the venous vasomotor reflex response was reduced according to the Child‐Pugh score (Childs A 37.4 ± 5.4%, normal control 62.3 ± 10.9%, Childs B 38.3 ± 18.2%, Childs C 22.5 ± 15.2%) and was statistically significant. The gastric mucosal blood flow and hepatic perfusion index are inversely correlated. The hepatic perfusion index altered with grading of cirrhotic change. This study confirms that the severity of portal hypertensive gastropathy is correlated with Child‐Pugh score.

Unexpected visitor on FDG PET/CT--brown adipose tissue (BAT) in mesentery in a case of retroperitoneal extra-adrenal pheochromocytoma: is the BAT activation secondary to catecholamine-secreting pheochromocytoma?

Fused positron emission tomography-computed tomography (PET/CT) technology has enabled the determination that nonmalignant fluorodeoxyglucose (FDG) uptake is observed in brown adipose tissue (BAT). FDG uptake in BAT is a known potential source of false-positive interpretations for PET. The typical locations of BAT include neck, supraclavicular area, mediastinum, and paravertebral intercostal spaces. Examples of atypical locations for BAT include posterior neck, left paratracheal area, axillae, perirenal area, and retrocrural area. We report PET/CT findings in a young male patient with malignant retroperitoneal extra-adrenal pheochromocytoma, who demonstrated FDG uptake in BAT at multiple locations including mesenteric BAT. We also propose catecholamine-secreting pheochromocytoma as a possible cause of BAT activation in our case.

Clinical translation of 177Lu-labeled PSMA-617: Initial experience in prostate cancer patients

OBJECTIVE PSMA-617 is reported to exhibit very high binding affinity towards PSMA receptors, over-expressed on prostate cancer cells and therefore, (177)Lu-labeled PSMA-617 is expected to play a pivotal role in the clinical management of patients suffering from ca prostate. The objective of the present study is to formulate the patient dose of (177)Lu-labeled PSMA-617, pre-clinical studies in animal model and clinical investigation in limited number of prostate cancer patients as well evaluating its potential for theranostic application. EXPERIMENTAL Patient dose of 7.4 GBq (200 mCi) of (177)Lu-labeled PSMA-617 was prepared by incubating 100 μg of PSMA-617 with (177)LuCl3 at 95 °C for 15 minutes. Radiochemical purity as well as in-vitro stability of the preparation was determined by PC and HPLC methods. The pharmacokinetic behavior and in-vivo distribution of the agent were studied by carrying out biodistribution studies in normal male Wistar rats. Preliminary clinical investigation was performed in 7 patients suffering from prostate cancer. RESULTS The complex was prepared with >98% radiochemical purity under the optimized reaction protocols and the preparation exhibited adequate in-vitro stability. Biodistribution studies revealed no significant uptake in any of the major organ/tissue along with major clearance through renal pathway. Clinical studies showed similar distribution in lesions and physiologic areas of uptake as seen in diagnostic (68)Ga-PSMA-11 PET scans performed earlier. CONCLUSION Preliminary clinical studies indicated the promising potential of the agent for theranostic applications. However, further investigations in large pool of patients are warranted to establish the theranostic potential of the agent.

Diffuse Large B-Cell Lymphoma In The Era Of Precision Oncology: How Imaging is Helpful

Diffuse large B cell lymphoma (DLBCL) is the most common histological subtype of Non-Hodgkins lymphoma. As treatments continues to evolve, so do imaging strategies, and positron emission tomography (PET) has emerged as the most important imaging tool to guide oncologists in the diagnosis, staging, response assessment, relapse/recurrence detection,and therapeutic decision making of DLBCL. Other imaging modalities including magnetic resonance imaging (MRI), computed tomography (CT), ultrasound, and conventional radiography are also used in the evaluation of lymphoma. MRI is useful for nervous system and musculoskeletal system involvement and is emerging as a radiation free alternative to PET/CT. This article provides a comprehensive review of both the functional and morphological imaging modalities, available in the management of DLBCL.

Lymphadenopathy resulting from acute toxoplasmosis mimicking relapse of non-Hodgkin's lymphoma on fluorodeoxyglucose positron emission tomography/computed tomography

We report a case documenting fluorodeoxyglucose (FDG) accumulation in cervical, supraclavicular and axillary lymph nodes resulting from acute toxoplasmosis. A 50-year-old Indian female with history of non-Hodgkins lymphoma (NHL) of left breast, postchemotherapy status, was found to have hypermetabolic right cervical, supraclavicular and axillary lymph nodes on a surveillance FDG positron emission tomography/computed tomography (PET/CT) scan. Her previous two PET/CT scans were unremarkable with no evidence of metabolically active disease. Therefore, a differential diagnosis of relapse of NHL versus infectious/inflammatory pathology was raised in the report. Biopsy of axillary lymph node demonstrated features characteristic of toxoplasmosis. The serological test results were also compatible with acute toxoplasmosis infection. Infective and inflammatory diseases are known to accumulate FDG, resulting in false positives for malignancy. This case demonstrates lymph nodal toxoplasmosis as a potential cause of false positive FDG PET/CT findings in patients with known malignancy and highlights the importance of histopathological and laboratory correlation for the accurate interpretation of FDG PET/CT scans.

Scintigraphy of the small intestine: a simplified standard for study of transit with reference to normal values

We read with interest the paper by Per Grybäck et al. [1]. However, we had difficulty in comprehending Fig. 1a. The arrow is shown as indicating the common bile duct. However, it actually appears to point to the second part of the duodenum, and the region of interest (ROI) seems to have been drawn on the early loops of the jejunum. It is unlikely that the common bile duct would extend so caudally to the inferior surface of the liver as has been indicated on the figure. One worries whether the ROIs were applied to all patients in the same manner. Any inconsistency in this respect would have significantly affected the conclusions of the study. Clarification is also needed on how the caecum was identified.

Direct Myocardial Ischemia Imaging: a New Cardiovascular Nuclear Imaging Paradigm

Myocardial perfusion imaging (MPI), using radiotracers, has been in routine clinical use for over 40 years. This modality is used for the detection of coronary artery disease (CAD), risk stratification, optimizing therapy, and follow‐up of patients with CAD. Molecular cardiovascular imaging using targeted radiotracers provides a unique opportunity for imaging biochemical and metabolic processes, and cell membrane transporter and receptor functions at a cellular and molecular level in experimental animal models as well as in humans. Cardiac imaging using radiolabeled free fatty acid analogues and glucose analogues enable us to image myocardial ischemia directly as an alternative to stress‐rest MPI. Direct ischemia imaging techniques can avoid and overcome some of the limitations of standard stress‐rest MPI. This article describes recent studies using 18F‐fluorodeoxyglucose (18FDG) for myocardial ischemia imaging.

Cardiac Hot Spot Imaging With 18FDG

Myocardial perfusion imaging is the mainstay of nuclear cardiovascular imaging. It has been in extensive clinical use for well over 35 years for diagnosing, risk-stratification, and long-term follow-up of patients with suspected or known coronary artery disease. A unique strength of nuclear imaging is its ability to provide a repertoire of tools for imaging metabolic and biochemical processes, receptor and transporter function, inflammation, and gene expression at molecular and cellular levels in intact organisms, under a wide variety of physiological conditions. With this approach, only selective myocardium with targeted abnormality can be visualized (hot spot imaging). This provides an opportunity for imaging complex biochemical, metabolic, and inflammatory processes of the cardiovascular system. (18)F-labeled (18)FDG, a radiolabeled glucose analogue, tracks cellular uptake and metabolism of glucose in the tissue and organs. Profound changes in regional glucose metabolism accompany several cardiovascular disease processes, which can be imaged using (18)FDG. However, caution is required while performing and interpreting these images. Because myocardial glucose uptake can vary widely under different metabolic and physiological states and this variation can overlap with the changes in myocardial glucose uptake under pathologic conditions, a strict and careful regulation of metabolic milieu is required while performing (18)FDG imaging. Cardiac (18)FDG imaging can be used for imaging myocardial ischemia, viability, and sarcoidosis. These techniques can overcome many of the limitations of current imaging techniques. In this article, we describe recent studies using (18)FDG for imaging myocardial ischemia and cardiac sarcoidosis.