Akash Sharma

Routine positron emission tomography does not alter nodal staging in patients undergoing EUS-guided FNA for esophageal cancer

BACKGROUND Although EUS-guided FNA (EUS-FNA) and 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) are both used in the staging of esophageal cancer, the utility of routinely performing both tests is unclear. OBJECTIVES The primary aim of the study was to determine the benefit of routine FDG-PET for esophageal cancer nodal staging in patients undergoing EUS-FNA. The secondary objective was to determine EUS criteria that selectively identify patients in whom PET yields additional information. DESIGN Retrospective chart review. SETTING Tertiary-care academic medical center. PATIENTS AND INTERVENTIONS All patients who underwent both EUS and PET for initial staging of esophageal cancer between April 2003 and August 2007. MAIN OUTCOME MEASUREMENTS EUS and PET detection of malignant lymph nodes and distant metastases. RESULTS Of 242 patients who underwent esophageal EUS for a malignant indication, 148 also underwent PET within 30 days. EUS detected locoregional-node disease by EUS criteria or cytology in 92 patients, and PET was positive in a minority of these patients (n = 41 [45%]). For celiac-node staging, PET was positive in 2 of 17 patients (12%) with celiac-node involvement detected by EUS. EUS was also significantly more sensitive than PET in the detection of nodal disease confirmed by cytology or histology (86% vs 44%). PET did not alter nodal staging in any patient with complete EUS-FNA. PET identified distant metastases only in those patients with incomplete EUS or nodal disease detected by EUS. LIMITATIONS Single institution, retrospective analysis. CONCLUSIONS The addition of PET to a complete EUS examination did not alter regional-node or celiac-node staging. PET performance in overall staging is strongly associated with EUS assessment of lymph nodes.

From the Angio Suite to the γ-Camera: Vascular Mapping and 99mTc-MAA Hepatic Perfusion Imaging Before Liver Radioembolization—A Comprehensive Pictorial Review

Endovascular mapping and conjoint 99mTc-macroaggregated albumin (99mTc-MAA) hepatic perfusion imaging provide essential information before liver radioembolization with 90Y-loaded microspheres in patients with primary and secondary hepatic malignancies. The aims of this integrated procedure are to determine whether there is a risk for excessive shunting of 90Y-microspheres to the lungs; to detect extrahepatic perfusion emerging from the injected vascular territory, which might lead to nontargeted radioembolization; to reveal incomplete coverage of the liver parenchyma involved by the tumor, which may be related to anatomic or acquired variants of the arterial vasculature; and to aid in calculation of the 90Y-microsphere dose to be delivered to the liver. This pictorial essay presents an integrated comprehensive review of the anatomic, angiographic, and nuclear imaging aspects of planned liver radioembolization. The relevant anatomy of the liver, including the standard and the variant arterial vasculature, will be shown using digital subtraction angiography, SPECT/CT, contrast-enhanced CT, and anatomic illustrations. Technical details that will optimize the imaging protocols and important imaging findings will be discussed. From the angio suite to the γ-camera—the goal of this review is to help the reader better understand how the technical details of the angiographic procedure are reflected in the imaging findings of the 99mTc-MAA hepatic perfusion study. In addition, the reader should learn to better recognize the pertinent findings and their clinical implications. This knowledge will enable the reader to provide a more useful interpretation of this complex multidisciplinary procedure.

Clinical application of PET/MRI in oncology

Hybrid imaging with integrated positron emission tomography (PET) and magnetic resonance imaging (MRI) combines the advantages of the high‐resolution anatomic data from MRI and functional imaging data from PET, and has the potential to improve the diagnostic evaluation of various types of cancers. The clinical oncologic applications of this newest hybrid imaging technology are evolving and substantial efforts are underway to define the role of PET/MRI in routine clinical use. The current published literature suggests that PET/MRI may play an important role in the evaluation of patients with certain types of malignancies, involving anatomic locations such as the pelvis and the liver. The purpose of this article is to review the current published PET/MRI literature in specific body oncologic applications. In addition, PET/MRI protocols and some of the technical issues of this hybrid imaging will be briefly discussed. J. Magn. Reson. Imaging 2016;44:265–276.

Impact of MR-Based Attenuation Correction on Neurologic PET Studies

Hybrid PET and MR scanners have become a reality in recent years, with the benefits of reduced radiation exposure, reduction of imaging time, and potential advantages in quantification. Appropriate attenuation correction remains a challenge. Biases in PET activity measurements were demonstrated using the current MR-based attenuation-correction technique. We aimed to investigate the impact of using a standard MR-based attenuation correction technique on the clinical and research utility of a PET/MR hybrid scanner for amyloid imaging. Methods: Florbetapir scans were obtained for 40 participants on a hybrid scanner with simultaneous MR acquisition. PET images were reconstructed using both MR- and CT-derived attenuation maps. Quantitative analysis was performed for both datasets to assess the impact of MR-based attenuation correction to absolute PET activity measurements as well as target-to-reference ratio (SUVR). Clinical assessment was also performed by a nuclear medicine physician to determine amyloid status based on the criteria in the Food and Drug Administration prescribing information for florbetapir. Results: MR-based attenuation correction led to underestimation of PET activity for most parts of the brain, with a small overestimation for deep brain regions. There was also an overestimation of SUVRs with cerebellar reference. SUVR measurements obtained from the 2 attenuation-correction methods were strongly correlated. Clinical assessment of amyloid status resulted in identical classification as positive or negative regardless of the attenuation-correction methods. Conclusion: MR-based attenuation correction causes biases in quantitative measurements. The biases may be accounted for by a linear model, although the spatial variation cannot be easily modeled. The quantitative differences, however, did not affect clinical assessment as positive or negative.

Overview of PET Tracers for Brain Tumor Imaging

This article provides an overview of the key considerations for the development and application of molecular imaging agents for brain tumors and the major classes of PET tracers that have been used for imaging brain tumors in humans. The mechanisms of uptake, biological implications, primary applications, and limitations of PET tracers in neuro-oncology are reviewed. The available data indicate that several of these classes of tracers, including radiolabeled amino acids, have imaging properties superior to those of (18)F-fluorodeoxyglucose, and can complement contrast-enhanced magnetic resonance imaging in the evaluation of brain tumors.

An Overview of Nuclear Medicine Studies for Urgent and Emergent Indications

In the emergency setting, functional imaging provided by nuclear medicine techniques can complement anatomical imaging for specific presentations. In some instances, nuclear medicine studies in patients with acute presentations may be performed to clarify the diagnosis when clinical evaluation and initial imaging are equivocal, to substitute for a first-line imaging procedure when cross-sectional imaging is contraindicated, to reduce radiation exposure, or to allow bedside imaging in unstable patients. This article provides an overview of the nuclear medicine studies that may be encountered in an emergency setting. The strengths and limitations of the studies have been discussed, along with important practical details and potential pitfalls that may be encountered. When available, guidelines from professional societies including the Society of Nuclear Medicine and Molecular Imaging (SNMMI) and the American College of Radiology (ACR) are included to help readers correctly integrate nuclear medicine into the overall imaging evaluation in the ED setting.