FDG Imaging for Assessing Cardiovascular Inflammation

1. Introduction

Noninvasive imaging techniques have been developed for diagnosis and clinical evaluation of cardiovascular diseases [1,2,3]. Positron emission tomography (PET) permits molecular imaging techniques in vivo and quantitative assessment of tracer functions, including myocardial blood flow, energy metabolism, and various receptor functions in vivo [3,4,5].

PET has a great advantage over other noninvasive imaging for performing various molecular imaging. ¹⁸F-fluorodeoxyglucose (FDG) is a radiopharmaceutical and glucose analog in which a hydroxyl group of the normal glucose molecule is replaced by ¹⁸F, a radioactive isotope of fluorine. FDG PET has been widely used for oncology studies, but also for cardiovascular diseases [5].

Recently FDG PET has been applied to identify and assess active cardiovascular inflammation. This review summarizes the unique characteristics of FDG PET in the cardiovascular field among other non-invasive imaging modalities. This includes important patient preparation to apply FDG PET for cardiovascular inflammation. Various clinical applications in this area are fully described.

1.1. Advantages and Disadvantages of PET Compared to Other Non-Invasive Imaging Modalities (Table 1)

Ultrasound imaging is widely available, inexpensive, and repeatable and does not involve the use of ionizing radiation [1,2,3,6]. Due to high spatial resolution, it permits precise assessment of structural abnormalities in the cardiovascular system. In addition, color doppler ultrasound and contrast enhanced ultrasound are valuable for the assessment of functional and tissue alterations. It is generally performed by an experienced sonographer using high-quality. The main limitation of ultrasound imaging is that it cannot depict structures below bone or air, and therefore, it does not provide reliable information about the thoracic aorta, unless performed via a transesophageal approach. In addition, the acquisition of ultrasound images is operator dependent, although studies of vascular ultrasound have shown high rates of inter-operator agreement.

Computed Tomography (CT) scans are renowned for their speed and high spatial resolution, enabling detailed anatomical visualization that is crucial for the assessment of disease states [1,2,3,7]. The ability to capture fine structural details quickly makes CT an indispensable tool in acute care settings. However, the use of iodinated contrast media, necessary for enhancing image contrast, poses risks, particularly for patients with renal impairment. These patients may experience further renal damage or other adverse effects from the contrast agent. Additionally, the intrinsic radiation exposure associated with CT scans is a concern, particularly in scenarios requiring repeated imaging.

CT is nicely suited to demonstrate pathological changes in the cardiac wall, as well as large, deep blood vessels [1,2,3,7]. It is a widely available and reproducible technique with high spatial resolution. CT angiography allows for the simultaneous assessment of the myocardial wall, the lumen, and the affected vessels. It also permits the detection of coronary stenosis. On the other hand, it involves the use of ionizing radiation and carries a risk connected to the use of iodinated contrast material.

Magnetic resonance imaging (MRI) offers distinct advantages over CT, particularly with its lack of ionizing radiation, making it safer for repeated use over time [1,2,3,8]. MRI excels in soft tissue contrast, making it ideal for imaging inflammatory changes in soft tissues and organs with superior clarity. However, the presence of loose metallic foreign bodies in a patient is a contraindication for MRI due to safety concerns and potential image distortion. Metal implants can also create significant artifacts, which may obscure diagnostic information and interfere with image interpretation. Despite these limitations, MRI remains a valuable tool for the detailed evaluation of inflammatory diseases without the risks associated with radiation.

PET/CT combines the anatomical detail provided by CT with the functional insight of PET imaging, offering a comprehensive overview of both structural and metabolic aspects of diseases in a single session [3,4]. This modality is particularly useful in evaluating inflammatory diseases as it can highlight areas of metabolic activity associated with inflammation. Importantly, PET/CT can be safely used in patients with renal failure, as it does not require iodinated contrast media. Nevertheless, the long acquisition times and exposure to ionizing radiation are significant drawbacks. Additionally, while PET/CT provides crucial functional information, its spatial resolution is less detailed compared to standalone CT, which can be a limitation in resolving fine anatomical details.

Table 1. Features of non-invasive imaging techniques for assessing cardiovascular field.

	Ultrasound	CT	MRI	PET/CT
Focus	Sound waves Structure and flow analysis	X-way attenuation Structure and functional analysis	Proton density and echo time Edema and necrosis	Various molecular functions Glucose metabolism
Patient advantage	Easy to perform even at bedside No radiation	Very fast scan Evaluation of other organs	No or minimally invasive procedure No radiation	Both anatomical and functional information Safe in renal failure
Patient disadvantage	Relatively long acquisition time Operator dependent	Radiation associated with imaging Side effect by contrast media	Long acquisition time Claustrophobia due to smaller patient bore Contraindicated in patients with loose foreign metals High cost	Long acquisition time Radiation with radiopharmaceuticals High cost
Imaging advantage	High spatial resolution Real-time imaging Simultaneous assessment of cardiac function	High spatial resolution Can evaluate calcified plaques	Superior soft tissue imaging with excellent spatial resolution True multiplanar capability to image in any oblique plane	Providing functional and biological information Several tracers
Imaging disadvantage	Limited use below bone or air Limited use for cardiac devices	Sub-optimal soft tissue imaging Lack of functional and biological information	MR image distortion Limited use for cardiac device	Limited spatial resolution Variable effect of thresholds or other criteria

Table 1. Features of non-invasive imaging techniques for assessing cardiovascular field.

	Ultrasound	CT	MRI	PET/CT
Focus	Sound waves Structure and flow analysis	X-way attenuation Structure and functional analysis	Proton density and echo time Edema and necrosis	Various molecular functions Glucose metabolism
Patient advantage	Easy to perform even at bedside No radiation	Very fast scan Evaluation of other organs	No or minimally invasive procedure No radiation	Both anatomical and functional information Safe in renal failure
Patient disadvantage	Relatively long acquisition time Operator dependent	Radiation associated with imaging Side effect by contrast media	Long acquisition time Claustrophobia due to smaller patient bore Contraindicated in patients with loose foreign metals High cost	Long acquisition time Radiation with radiopharmaceuticals High cost
Imaging advantage	High spatial resolution Real-time imaging Simultaneous assessment of cardiac function	High spatial resolution Can evaluate calcified plaques	Superior soft tissue imaging with excellent spatial resolution True multiplanar capability to image in any oblique plane	Providing functional and biological information Several tracers
Imaging disadvantage	Limited use below bone or air Limited use for cardiac devices	Sub-optimal soft tissue imaging Lack of functional and biological information	MR image distortion Limited use for cardiac device	Limited spatial resolution Variable effect of thresholds or other criteria

1.2. Patient Preparation in FDG PET Study

FDG uptake in the myocardium is dependent on cardiac energy substrate, either glucose or fatty acid depending on postprandial or long fasting conditions [9,10] (Figure 1). FDG PET is applicable for any patient. In addition, whole-body imaging is available once FDG is administered. Thus, such whole-body study is commonly used in the studies in oncology and generalized inflammatory diseases. Glucose is the major energy source in the myocardium under postprandial or glucose loading condition. Therefore, FDG uptake is seen in normal and ischemic myocardium in these conditions. In fasting condition, on the contrary, glucose energy metabolism is suppressed, and fatty acids are the major energy source in the normal myocardium. Thus, FDG uptake is observed only in the ischemic and/or injured myocardium. Therefore, patient preparation before FDG administration is quite important since FDG uptake in the myocardium is observed as either physiological uptake or abnormal active uptake depending on the patient nutritional condition [9,10,11,12,13,14,15].

One of the classical applications of PET is assessment of myocardial viability. FDG PET identifies glucose metabolism in the heart and thus myocardial viability [16,17,18,19]. A region with preserved FDG uptake indicates the presence of viable myocardium. For this purpose, glucose administration with oral loading or an insulin-glucose clamp is applied for an increase in FDG uptake both in the normal and ischemic but viable myocardium in comparison with no FDG uptake in infarcted tissue. Myocardial viability study using FDG PET has a great clinical impact on predicting reversible dysfunction after revascularization and prognosis in patients with coronary artery disease and left ventricular dysfunction [16,17,18,19].

The activation of granulocytes and macrophages during inflammation enhances the FDG uptake. Thus, FDG PET is useful for detecting active cardiovascular inflammation [20,21]. In order to identify active inflammation by FDG PET, physiological uptake in the normal myocardium should be suppressed by appropriate patient preparation. Figure 2 shows typical cases of positive FDG uptake in active inflammatory lesions in giant cell arteritis, cardiac sarcoidosis, and arteriosclerosis. High FDG uptake in large vessels is seen in giant cell arteritis and arteriosclerosis. In cardiac sarcoidosis, high FDG uptake in the myocardium and pulmonary nodules are well observed.

1.3. Roles of FDG-PET in Cardiovascular Inflammation

1.3.1. Assessment of Cardiac Sarcoidosis

Sarcoidosis is a systemic granulomatous disorder of unknown cause [22]. Cardiac involvement has the potential for life-threatening consequences such as atrioventricular block, ventricular arrhythmias, congestive heart failure, and sudden death [23]. Therefore, accurate diagnosis, suitable treatment, and treatment monitoring are required for those suspected of cardiac sarcoidosis.

Non-invasive cardiac imaging has recently been developed: cardiac magnetic resonance imaging (MRI) and various radionuclide imaging, including FDG PET were added to the Japanese Ministry of Health and Welfare (JMHW) modified diagnostic criteria for cardiac sarcoidosis in 2006 [24] and 2016 [25]. The Heart Rhythm Society (HRS) also published an expert consensus statement in 2014 [26]. The diagnostic pathways for cardiac sarcoidosis are divided into histological and clinical branches. Histopathological diagnosis is required to reveal noncaseating granulomas from endomyocardial biopsy (EMB) or surgical resection of the heart. However, the role of biopsy is limited as previously described [22,23]. Clinical diagnosis requires concordance among electrocardiography, echocardiography, and cellular and molecular imaging, including late gadolinium enhancement on MRI and FDG PET.

FDG PET is commonly used to assess the infiltration of sarcoidosis in the myocardium. Since FDG uptake is associated with the expression of glucose transporters, increased FDG uptake may reflect active inflammatory cells, such as macrophages, lymphocytes, and granulocytes. Thus, active sarcoid lesions may be nicely shown as focal FDG uptake in the myocardium as well as other active sarcoid lesions in the body. Patients with suspected cardiac sarcoidosis require adequate preparation, such as prolonged fasting, a low-carbohydrate diet, and/or a high-fat, high protein diet to suppress the false-positive association with physiological myocardial FDG uptake [27,28] as shown in Figure 1. FDG PET with an adequate preparation protocol is ideal for detecting active lesions. When evaluating cardiac sarcoidosis, it is important to assess not only the extent of FDG uptake but also its location. The involvement of specific myocardial segments, particularly the basal to mid-anterior and mid-septal segments, is associated with higher event rates in patients with suspected cardiac sarcoidosis [29]. FDG PET is also valuable for assessing the response to anti-inflammatory therapy in patients with cardiac sarcoidosis [30,31,32,33,34] (Figure 3). Furthermore, FDG PET has a potential for predicting patient outcomes [32,33].

A recent meta-analysis indicated that FDG-PET had slightly lower sensitivity than MRI but both modalities showed similar specificity for detecting cardiac sarcoidosis [34]. FDG PET may be valuable for identifying active inflammation as high FDG uptake but not fibrotic cardiac sarcoidosis. Thus, both FDG PET and MRI have important roles in diagnosing cardiac sarcoidosis and its tissue characterization. FDG PET and MRI are useful for the early detection of cardiac sarcoidosis. Ohira et al. investigated the prevalence and characteristics of cardiac sarcoidosis in patients with biopsy-proven extracardiac sarcoidosis, comparing those with normal and abnormal 12-lead electrocardiography and transthoracic echocardiography findings [35]. They found that around 20% of patients with normal results on these tests still had cardiac sarcoidosis, emphasizing the importance of physicians remaining alert to the possibility of cardiac involvement even in the absence of conduction or structural abnormalities.

There are several clinical studies going to clarify the values of semi-quantitative analysis of FDG uptake in active lesions of cardiac sarcoidosis. One recent report showed a value of follow-up by FDG PET in patients with active cardiac sarcoidosis [36]. After 12 months of prednisolone treatment, 80% of them showed a response with ≥70% metabolic reduction, but the remaining patients indicated either poor response or recurrence. Further studies are needed to evaluate the long-term prognostic value using FDG PET and MRI in patients with cardiac sarcoidosis.

2. Assessment of Endocarditis

Infective endocarditis is another severe cardiac inflammation, where FDG PET plays an important role in its diagnosis and management. In addition to local damage in the myocardium, metastatic infection, embolic phenomenon, or immune-mediated damage may cause considerable morbidity and mortality. In many cases, endocarditis may often be associated with a prosthetic valve [37]. Infective endocarditis demonstrates a variable clinical presentation, ranging from acute onset to a subacute or chronic course. The diagnosis is based on the modified Duke criteria: the major criteria include either the microbiological evidence of infection by typical microorganisms and/or the documentation of cardiac lesions by imaging techniques. The minor criteria include predisposing conditions, fever, embolic vascular dissemination, immunological phenomena, and microbiological evidence [37,38].

Cardiac devices have been accompanied by an even higher increasing rate of device infections. Echocardiography is the first-line imaging test in suspected endocarditis. However, echocardiography is more challenging in patients with prosthetic valves. Cardiac CT and MRI are commonly applied for assessing endocarditis. Such anatomical imaging can be affected by artifacts from the metal device, and abnormalities may not be specific for active infection. Therefore, they have an inherent limitation for accurate image analysis [37,38,39]. FDG PET, on the other hand, plays a powerful tool not only for identifying active myocardial lesions but also for detecting metastatic and embolic lesions throughout the body due to a whole-body PET survey [37,38,39,40,41,42,43]. The extracardiac infection source findings might change the clinical management and the course of the disease. In patients with prosthetic valve–related endocarditis, FDG PET/CT can identify septic embolism events, which is critical for patient management [39,42]. FDG PET/CT may identify active inflammation in endocarditis earlier than structure abnormalities assessed by echocardiography and CT.

The meta-analysis of 13 studies involving 537 patients, PET/CT had moderate sensitivity and specificity for the diagnosis of infective endocarditis [43]. However, the sensitivity improved when the evaluation of patients with suspected prosthetic valve endocarditis was selected. These data suggest that PET/CT has the potential for use as an adjunctive diagnostic modality in challenging cases of possible infective endocarditis. Recent expert consensus recommendations from many European and American Societies support clinical values of FDG PET for the evaluation of suspected cardiovascular infection by increasing diagnostic accuracy, identifying extracardiac involvement, and assessing cardiac implanted device pockets, leads, and all portions of ventricular assist devices [44]. This may aid in key medical and surgical considerations.

3. Assessment of Vasculitis

Vasculitis is a group of disorders characterized by inflammation of blood vessels, which can affect arteries, veins, or capillaries of various sizes (Table 2). The inflammation can lead to vessel wall damage, narrowing, and even occlusion, disrupting blood flow and causing tissue damage. Vasculitis is classified based on the size of the affected vessels: large, medium, small, variable vessel vasculitis, and vasculitis associated with systemic diseases or specific causes [45].

Large vessel vasculitis affects the largest arteries in the body, such as the aorta and its major branches. The large-vessel vasculitis is characterized by a mononuclear and granulomatous infiltration of the vessel wall. Two key types include giant cell arteritis and Takayasu arteritis. Giant cell aortitis is more prevalent among Caucasians and occurs in individuals over the age of 50. It commonly affects the temporal arteries, leading to symptoms like headaches, jaw pain, and vision problems, and can lead to serious complications such as vision loss. Takayasu arteritis is mainly observed in female patients under the age of 40, with a predilection for individuals of Asian descent. The affected arteries in Takayasu arteritis are mainly in the mesenteric, renal, and ilio-femoral arteries while sparing the medium-sized cranial arteries. Takayasu arteritis has a greater propensity for causing severe focal stenotic lesions of the affected vessels than giant cell arteritis. In both large-vessel vasculitis, the inflammatory process may deteriorate the aortic wall, resulting in potentially life-threatening vascular complications. Therefore, it is important to establish a diagnosis as early as possible using suitable biomarkers and imaging methods [46,47].

Medium vessel vasculitis targets medium-sized arteries, which supply blood to specific organs. Polyarteritis Nodosa affects the main arteries of various organs, leading to organ ischemia (insufficient blood supply) and skin lesions. Kawasaki Disease, which primarily affects children, involves the coronary arteries and can lead to coronary artery aneurysms, along with fever and other systemic symptoms.

Small vessel vasculitis involves the smallest blood vessels, including capillaries, venules, and arterioles. Key examples include Granulomatosis with Polyangiitis (formerly known as Wegener’s Granulomatosis) and Microscopic Polyangiitis. These conditions often affect the respiratory tract and kidneys, leading to sinusitis, lung nodules, and kidney disease. Another small vessel vasculitis, Churg-Strauss Syndrome (or Eosinophilic Granulomatosis with Polyangiitis, EGPA), is marked by asthma, high eosinophil levels, and involvement of the skin, nerves, and heart.

Variable vessel vasculitis can affect vessels of any size. For instance, Behçet’s Disease causes recurrent ulcers on mucous membranes (oral and genital) and uveitis (eye inflammation), while Cogan’s Syndrome affects the eyes and ears, leading to ocular and auditory disturbances.

Some types of vasculitis are associated with systemic diseases. For example, Rheumatoid Vasculitis occurs in severe cases of rheumatoid arthritis, typically involving small and medium vessels. Similarly, Lupus Vasculitis affects multiple organs in individuals with systemic lupus erythematosus.

Vasculitis is characterized by mostly autoimmunologically induced inflammatory processes of vascular structures. They have various clinical and radiologic appearances. Diagnosis and therapy monitoring of vasculitis are often challenging because of the heterogeneity of subgroups and their variable clinical, laboratory, and radiologic manifestations. The choice of an adequate imaging method mainly depends on the size and localization of the affected vessels, as well as on the patient’s individual circumstances and the specific question. For vascular imaging, morphologic changes in the context of the disease can be visualized by radiologic imaging methods in many forms of vasculitis, either directly by visualizing the vessel lesions or indirectly by visualizing the consequences of vessel inflammation in the affected organ. The choice of an adequate imaging modality depends on the size and localization of the affected vessels. Several different imaging techniques are available for visualizing direct and indirect signs of vessel inflammation. Vessel lesions in small vessel vasculitis are usually below the radiologic detection limits. Vascular imaging can also help in the selection of the best biopsy point [48].

FDG PET imaging has recently been used for accurate detection of vascular inflammation in the aortic wall [46,49,50,51]. Functional FDG PET combined with anatomical CT angiography may be of synergistic value for optimal diagnosis, monitoring of disease activity, and evaluating damage progression in large vessel vasculitis. There is a joint paper showing international recommendations and statements, based on the available evidence in the literature and the consensus of experts on FDG PET study, including patient preparation under FDG PET/CT study, interpretation for the diagnosis, and follow-up of patients with suspected or diagnosed large vessel vasculitis [50]. FDG PET is considered a valuable tool for monitoring the treatment effects of this disease. Based on the review of systematic literature, FDG PET showed sensitivity of 77% and specificity of 71% for detecting relapsing/refractory disease in patients with large vasculitis [51]. In addition, a new recommendation for the use of imaging modalities including FDG PET has recently been reported in the diagnosis and management of patients with primary large vessel vasculitis [52]. FDG PET may hold an important role in distinguishing between large vessel aortitis subtypes, evaluating disease distribution, and detecting extracranial involvement in patients with cranial giant cell arteritis or polymyalgia phenotypes [53]. It also has a promising utility in predicting clinical outcomes and assessing treatment response, based on the correlation between reductions in FDG uptake and improved disease control. Future research should focus on further refining PET/CT techniques, exploring their utility in monitoring treatment response, and investigating novel imaging modalities.

4. Assessment of Atherosclerosis

Atherosclerosis is a chronic condition characterized by arterial stiffening due to the buildup of cholesterol plaques on vessel walls. Progressive enlargement of these plaques may lead to a spectrum of debilitating cardiovascular conditions, such as peripheral artery disease, ischemic stroke, coronary artery disease, and acute myocardial infarctions. These conditions represent a major cause of morbidity and mortality. Therefore, a suitable diagnosis to identify unstable atherosclerotic disease is valuable [54,55].

Hypercholesterolemia with deposition and oxidation of low-density lipoproteins in the arterial vessel wall may be responsible for the initiation and progression of atherogenesis. The migration, infiltration, and death of inflammatory monocytes/macrophages in the arterial wall ultimately lead to the formation of vulnerable atherosclerotic plaques at high risk for causing fatal cardiovascular events [54,55]. In addition, systemic inflammation, such as inflammatory or autoimmune diseases may also accelerate the development of atherosclerosis, independent of lipid levels.

Non-invasive imaging is becoming more essential to investigate the role of inflammation in cardiovascular diseases. Conventional imaging modalities, including ultrasonography, CT, and MRI angiography, are widely used clinically to visualize large symptomatic plaques but are limited in their ability to assess the early stages of atherosclerosis [56,57]. Atherosclerotic plaque is another target for PET to identify microscopic inflammation. Molecular imaging using FDG and/or ¹⁸F-sodium fluoride (NAF) targeting microcalcification is clinically used in combination with high resolution CT or MRI [58,59]. The most used diagnostic signs are halo sign in ultrasound study and visual positive uptake on FDG PET which are often seen not only in large vessel vasculitis but also in atherosclerosis. When visually scoring FDG uptake intensity and pattern, FDG　PET/CT attained 95% specificity for diagnosing LVV against an atherosclerotic control group [60].

These imaging are applied for assessing carotid plaque and even coronary plaque. A whole-body PET may identify unpredictable atherosclerotic plaque and even embolic lesions after endocarditis [61,62]. FDG vascular uptake is reflective of functional changes in the arterial vessel wall which may predict structural changes related to the progression of atherosclerosis. Furthermore, this study suggests that early targeting of vascular inflammation with appropriate therapeutic regimens may slow down the formation of high-risk, vulnerable plaques [54,55].

5. Assessment in Cardio-Oncology

Cancer and cardiovascular disease are the leading causes of death in most developed countries. Cancer and cardiovascular disease are closely related from both scientific and clinical perspectives. Advances in cancer treatment have improved in patient survival rate of cancer. On the other hand, management of cardiovascular complications has been increasingly required in cancer patients. Both cardiologists and oncologists should pay caution in this new field called “cardio-oncology” [63,64,65,66]. More recently, radiologists have played important roles in suitable image selection and interpretations for assessing cardiovascular complications. In addition, radiology specialists may provide appropriate radiotherapy planning with reduced radiation dose to the cardiovascular system. Radiotherapy is well known to have significant cardiovascular complications, such as pericarditis, and long-term complications, such as restrictive or constrictive pericarditis. Cardiovascular imaging has played a key role for the non-invasive assessment of cardiovascular alterations complimentary to biomarkers and clinical assessment. Cardiovascular imaging should also play an important role for suitable radiation planning [67].

Secondary large vessel vasculitis should also be considered. Extensive chemotherapy for cancer treatment, particularly human epidermal growth factor receptor 2 (HER2) inhibitor and immune checkpoint inhibitor, may cause severe cardiotoxic effects [63,64]. In addition, radiation therapy for the esophageal cancer or breast cancer may possibly cause cardiovascular dysfunction [65,66]. Novel therapeutic therapies have significantly improved survival and long-term outcomes in many cancer entities. Unfortunately, this improvement in outcome is often accompanied by increasingly relevant therapy-related cardiovascular toxicity. Molecular imaging using MRI and nuclear imaging are used for assessing tissue function before and after cancer therapy from molecular perspectives. Since FDG PET is often applied for the detection, and extension of cancers, and cancer treatment monitoring. FDG PET is valuable for detecting active cardiovascular inflammation, particularly in the early stage of cancer therapy, and monitoring toxic effects [67]. Cardiovascular toxicity may carry a risk of arterial thrombosis, including myocardial infarction. FDG serves as a sensitive indicator of the metabolic shift in the myocardium, which occurs in the early stages of coronary artery disease [67].

Active cardiovascular inflammation may often be observed on abnormal FDG uptake after cancer treatment, which may possibly cause fatal cardiovascular dysfunction. Suitable imaging modalities in combination with suitable biomarkers should play an important role in detecting and monitoring cardiotoxic effects after cancer treatment [68,69]. Particularly, FDG PET is considered an elegant approach for the simultaneous assessment of tumor response to cancer therapy and early detection of possible cardiovascular involvement as well [69,70,71,72].

6. Conclusions

Among various imaging methods for assessing cardiovascular dysfunction, FDG PET is useful for detecting active cardiovascular inflammation mainly due to enhanced glucose utilization by the activation of granulocytes and macrophages. To identify active inflammation by FDG PET, physiological uptake in the normal myocardium should be suppressed by appropriate patient preparation. FDG PET has been used to detect active lesions and assess the response to anti-inflammatory therapy in patients with cardiac sarcoidosis. FDG PET has also been used to identify other active cardiovascular inflammation, such as endocarditis, aortitis, and unstable atherosclerosis. Furthermore, FDG PET may be applied not only to assess response to cancer therapy but also to detect possible cardiovascular involvement. More clinical experiences are expected to confirm the value of FDG PET for assessing and monitoring active cardiovascular inflammation.