Combined PET and X-ray Computed Tomography Imaging in Pulmonary Infections and Inflammation

Jamshed Bomanji; Ahmad Almuhaideb; Alimuddin Zumla

Disclosures

Curr Opin Pulm Med. 2011;17(3):197-205. 

In This Article

Abstract and Introduction

Abstract

Purpose of review This review addresses issues relating to the use of the relatively new combined PET and X-ray computed tomography (PET/CT) modality for imaging pulmonary infections and inflammation, as well as assessing its potential for this purpose.
Recent findings Accurate definition and monitoring of the extent of lung infection is difficult using conventional chest radiograph, CT scan, MRI, and radioisotope scintigraphy. In the last decade, PET/CT using radiolabeled fluorodeoxyglucose has been added to the imaging armamentarium, mostly for imaging lung cancer. To date, very few data are available on the application of this technique for imaging pulmonary infections and inflammation; however, this situation is changing, and there is now more interest in using PET/CT for this purpose. In addition, there are new tracers on the horizon which remain to be exploited.
Summary This review addresses some of these issues and outlines the potential to use PET/CT for noncancer pulmonary indications.

Introduction

Lower respiratory tract infections are a major cause of morbidity and mortality worldwide despite advances in the identification of etiologic microorganisms and availability of potent antibiotic therapy. In addition, there is ongoing controversy regarding the optimal diagnostic approach. Imaging of pulmonary infection or inflammation provides means of localizing foci of infection and can be done with different modalities such as conventional chest radiographs, CT scan, magnetic resonance imaging (MRI), and radioisotope scintigraphy. This review will focus on the available literature on the role of combined PET and X-ray computed tomography (PET/CT) as a relatively new diagnostic modality for imaging pulmonary infection or inflammation.

One of the most commonly used tracers for PET scanning is fluorine-18 (18F) labeled fluorodeoxyglucose (FDG), which measures metabolic activity in various tissues. The main clinical indication in the pulmonary domain is the detection of malignant lung nodules or mediastinal nodes. It has also been shown that 18F-FDG detects sites of infection and inflammation in the chest. However, there is scant literature on the role of 18F-FDG PET/CT imaging in pulmonary infection. Furthermore, there are other potential PET tracers, such as gallium-68 citrate (68Ga-citrate) and gallium-68 DOTA-DPhe, Tyr-octreotate (68Ga-DOTATATE), which do not require a cyclotron for production and which can be used for imaging pulmonary infection or inflammation but have yet to be exploited.

PET/CT also has the ability to quantitatively delineate lung infection or inflammation, thus providing the ability to monitor treatment response in diverse conditions such as pneumonia, acute respiratory distress syndrome (ARDS), cystic fibrosis, pulmonary fibrosis, and chronic obstructive pulmonary disease.[1•] Chen et al.[2] have suggested that PET/CT should be considered the most accurate quantitative radionuclide imaging method currently available for imaging pulmonary inflammation.

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