How to differentiate benign versus malignant cardiac and paracardiac 18F FDG uptake at oncologic PET/CT

Heterogeneous Uptake of Al 18 F-NOTA-FAPI and 18 F-FDG in Apical Aneurysm in Apical Hypertrophic Cardiomyopathy

ABSTRACT

Apical aneurysm in apical hypertrophic cardiomyopathy (HCM) is a very rare condition in clinical practice. Some studies have reported abnormal uptake of 18 F-FDG and 18 F-FAPI in HCM, respectively. We presented a case of FAPI and FDG imaging in a patient with apical aneurysm in apical HCM, and further analyzed the discrepancy of spatial distribution pattern of these 2 radiotracers.

Cardiac Neuroendocrine Tumor Metastases on 68Ga-DOTATATE PET/CT: Identification and Prognostic Significance

Neuroendocrine tumor (NET) metastases to the heart are found in 1%-4% of NET patients and have been reported primarily in the form of individual cases. We investigated the prevalence, clinical characteristics, imaging features, and outcomes of NET patients with cardiac metastases on 68Ga-DOTATATE PET/CT. Methods: 68Ga-DOTATATE PET/CT of 490 consecutive patients from a single institution were retrospectively reviewed for sites of metastases. The cumulative cardiovascular event rate and overall survival of patients with cardiac NET metastases (CNMs) were compared with those of a control group of metastatic NET patients without cardiac metastases. In patients with CNMs, the cardiac SUVmax with and without normalization to the myocardial background uptake was compared with a separate cohort of 11 patients with active cardiac sarcoidosis who underwent 68Ga-DOTATATE PET/CT for research purposes. Results: In total, 270 patients with metastatic NETs were identified, 9 (3.3%) of whom had CNMs. All 9 patients had grade 1-2 gastroenteropancreatic NETs, most commonly from the small intestine (7 patients). The control group consisted of 140 patients with metastatic grade 1-2 gastroenteropancreatic NETs. On Kaplan-Meier analysis, there was no significant difference in the risk of cardiovascular adverse events (P = 0.91 on log-rank test) or mortality (P = 0.83) between the metastatic NET patients with and without cardiac metastases. The degree of cardiac DOTATATE uptake was significantly higher in CNMs than in patients with cardiac sarcoidosis without overlap, in terms of both cardiac SUVmax (P = 0.027) and SUVmax-to-myocardial background ratio (P = 0.021). Conclusion: Routine 68Ga-DOTATATE PET/CT can be used to identify CNMs in 3% of patients with metastatic NETs. CNMs do not confer added cardiovascular or mortality risk. A distinguishing feature of CNMs is their high degree of DOTATATE uptake compared with focal myocardial inflammation.

The active papillary muscle sign in 18F-FDG PET/CT cardiac sarcoidosis exams and its relationship with myocardial suppression

OBJECTIVE

Papillary muscle (PM) activity may demonstrate true active cardiac sarcoidosis (CS) or mimic CS in 18FDG-PET/CT if adequate myocardial suppression (MS) is not achieved. We aim to examine whether PM uptake can be used as a marker of failed MS and measure the rate of PM activity presence in active CS with different dietary preparations.

MATERIALS AND METHODS

We retrospectively reviewed PET/CTs obtained with three different dietary preparations. Diet-A: 24-h ketogenic diet with overnight fasting (n = 94); Diet-B: 18-h fasting (n = 44); and Diet-C: 72-h daytime ketogenic diet with 3-day overnight fasting (n = 98). Each case was evaluated regarding CS diagnosis (negative, positive, and indeterminant) and presence of PM activity. MaxSUV was measured from bloodpool, liver, and the most suppressed normal myocardium. Linear mixed-effects models were used to compare these factors between those with PM activity and those without.

RESULTS

PM activity was markedly lower in the Diet-C group compared with others: Diet-C: 6 (6.1%), Diet-A: 36 (38.3%), and Diet-B: 26 (59.1%) (p < 0.001). MyocardiumMaxSUV was higher, and MyocardiummaxSUV/BloodpoolmaxSUV, MyocardiummaxSUV/LivermaxSUV ratios were significantly higher in the cases with PM activity (p < 0.001). Among cases that used Diet-C and had PM activity, 66.7% were positive and 16.7% were indeterminate. If Diet-A or Diet-B was used, those with PM activity had a higher proportion of indeterminate cases (Diet-A: 61.1%, Diet-B: 61.5%) than positive cases (Diet-A: 36.1%, Diet-B: 38.5%).

CONCLUSION

Lack of PM activity can be a sign of appropriate MS. PM activity is less common with a specific dietary preparation (72-h daytime ketogenic diet with 3-day overnight fasting), and if it is present with this particular preparation, the likelihood that the case being true active CS might be higher than the other traditional dietary preparations.

Robustness of [18F]FDG PET/CT radiomic analysis in the setting of drug-induced cardiotoxicity

BACKGROUND AND OBJECTIVES

Standardization of radiomic data acquisition protocols is still at a very early stage, revealing a strong need to work towards the definition of uniform image processing methodologies The aim of this study is to identify sources of variability in radiomic data derived from image discretization and resampling methodologies prior to image feature extraction. Furthermore, to identify robust potential image-based biomarkers for the early detection of cardiotoxicity.

METHODS

Image post-acquisition processing, interpolation, and volume of interest (VOI) segmentation were performed. Four experiments were conducted to assess the reliability in terms of the intraclass correlation coefficient (ICC) of the radiomic features and the effects of the variation of voxel size and gray level discretization. Statistical analysis was performed separating the patients according to cardiotoxicity diagnosis. Differences of texture features were studied with Mann-Whitney U test. P-values <0.05 after multiple testing correction were considered statistically significant. Additionally, a non-supervised k-Means clustering algorithm was evaluated.

RESULTS

The effect of the variation in the voxel size demonstrated a non-dependency relationship with the values of the radiomic features, regardless of the chosen discretization method. The median ICC values were 0.306 and 0.872 for absolute agreement and consistency, respectively, when varying the discretization bin number. The median ICC values were 0.678 and 0.878 for absolute agreement and consistency, respectively, when varying the discretization bin size. A total of 16 first order, 6 Gray Level Co-occurrence Matrix (GLCM), 4 Gray Level Dependence Matrix (GLDM) and 4 Gray Level Run Length Matrix (GLRLM) features demonstrated statistically significant differences between the diagnosis groups for interim scans (P<0.05) for the fixed bin size (FBS) discretization methodology. However, no statistically significant differences between diagnostic groups were found for the fixed bin number (FBN) discretization methodology. Two clusters based on the radiomic features were identified.

CONCLUSIONS

Gray level discretization has a major impact on the repeatability of the radiomic features. The selection of the optimal processing methodology has led to the identification of texture-based patterns for the differentiation of early cardiac damage profiles.

Extinction of Lipomatous Hypertrophy of the Interatrial Septum FDG Uptake With Propranolol Premedication

ABSTRACT

Lipomatous hypertrophy of the interatrial septum is a rare lesion of the heart. CT and cardiac MR are often sufficient to determine the benign lipomatous nature of the tumor and can avoid the need for histological confirmation. Lipomatous hypertrophy of the interatrial septum contains variable amounts of brown adipose tissue, resulting in different degrees of 18 F-FDG uptake in PET. We report the case of a patient with an interatrial lesion suspected of malignancy, discovered on CT and failing cardiac MR, with initial 18 F-FDG uptake. Final characterization was made thanks to 18 F-FDG PET with β-blocker premedication, avoiding an invasive procedure.

Anatomic and Functional Imaging of Immunoglobulin G4-related Disease and Its Mimics

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is an immune-mediated fibrosclerosing disease with tumefactive lesions infiltrated by IgG4-positive plasma cells. Initially described as autoimmune pancreatitis, IgG4-RD is now recognized as a discrete entity and is found to affect virtually any organ in the body. Common extrapancreatic sites include the biliary tree, salivary glands, periorbital tissue, lungs, kidneys, lymph nodes, aorta, retroperitoneum, and thyroid gland. Diagnosis-which relies on histopathologic, serologic, and radiologic features-can be challenging with the disease underdiagnosed, as IgG4-RD often mimics malignancy, infectious processes, or other immune-mediated conditions. Patients may present with signs of compression of nearby structures due to mass effect or with organ failure when the disease is left untreated. The clinical course is complex, with single- or multiorgan involvement and metachronous or synchronous occurrence of lesions. IgG4-RD responds well to glucocorticoid therapy, disease-modifying antirheumatic drugs, and B-cell-depleting biologic agents; prompt diagnosis is important to avoid delay in treatment and unnecessary pharmacologic or surgical intervention. While imaging features may not be specific for IgG4-RD, functional whole-body imaging with fluorine 18-fluorodeoxyglucose PET/CT is a useful adjunct for localizing extrapancreatic sites for biopsy, monitoring therapeutic response, and demonstrating disease relapse. The authors describe the pancreatic and extrapancreatic sites of involvement in IgG4-RD, with imaging features and patterns to aid in distinguishing IgG4-RD from its mimics through a multimodality approach with emphasis on functional imaging evaluation. ^©RSNA, 2023 Quiz questions in the supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

Expert review for clinical and translational imaging actionable imaging findings in the daily PET/CT scenario

Background and aim

The American College of Radiology (ACR) defines "actionable findings" the ones requiring a special communication between radiologists and referring clinicians, suggesting to organize their categorization in a three-degree scale on the basis of the risk for the patient to develop complications. These cases may fall in a grey-zone communication between different care figures with the risk of being underestimated or even not being considered at all. In this paper, our aim is to adapt the ACR categorization to the most frequent actionable findings encountered when reporting PET/CT images in a Nuclear Medicine Department, describing the most frequent and relevant imaging features and presenting the modalities of communication and the related clinical interventions that can be modulated by the prognostic severity of the clinical cases.

Materials and methods

We performed a descriptive, observational and critical analysis of the most relevant literature on the topic of "actionable findings", in particular, starting from the reports of the ACR Actionable Reporting Work Group, we categorised and described, in a narrative review, the most relevant "actionable findings" encountered in the Nuclear Medicine PET/CT daily practice.

Results

To the best of our knowledge, to date there are no clear indications on this selective PET/CT topic, considering that the current recommendations target mainly radiologists and assume a certain level of radiological expertise. We resumed and classified the main imaging conditions under the term of "actionable findings" according to the corresponding anatomical districts, and we described their most relevant imaging features (independently of PET avidity or not). Furthermore, a different communication timing and strategy was suggested on the basis of the findings' urgency.

Conclusion

A systematic categorization of the actionable imaging findings according to their prognostic severity may help the reporting physician to choose how and when to communicate with the referring clinician or to identify cases requiring a prompt clinical evaluation. Effective communication is a critical component of diagnostic imaging: timely receipt of the information is more important than the method of delivery.

FDG-PET findings associated with various medical procedures and treatments

[¹⁸F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a well-established modality with high sensitivity for the diagnosis and staging of oncologic patients. FDG is taken up by the glucose transporter of the cell membrane and becomes trapped within the cell. In addition to malignant neoplasms, active inflammatory lesions and some kinds of benign tumors also accumulate FDG. Moreover, the degree of uptake into normal organs and tissues depends on various physiological conditions, which is affected by various medical procedures, treatments, and drugs. To avoid misleading interpretations, it is important to recognize possible situations of unexpected abnormal accumulation that mimic tumor lesions. In this review, we present various FDG findings associated with surgical or medical procedures and treatments. Some findings reflect the expected physiological reaction to treatment, and some show inflammation due to prior procedures. Occasionally, FDG-PET visualizes other disorders that are unrelated to the malignancy, which may be associated with the adverse effects of certain drugs that the patient is taking. Careful review of medical records and detailed interviews of patients are thus necessary.

Metabolic activity of the left and right atria are differentially altered in patients with atrial fibrillation and LV dysfunction

BACKGROUND

Alterations in atrial metabolism may play a role in the perpetuation of atrial fibrillation (AF). This study sought to compare 18F-fluorodeoxyglucose (FDG) uptake on PET, in patients with LV dysfunction versus those without AF.

METHODS

Seventy-two patients who underwent myocardial viability assessment were evaluated. AF patients (36) had persistent or permanent AF based on history and ECG. Patients without AF (36) were matched to AF patients based on sex, diabetes, age, and LVEF. Maximum and mean FDG Standard Uptake Values (SUV) in the left atrial (LA) wall and right atrial (RA) wall were measured. Tissue-to-blood ratios (TBR) were calculated as atrial wall to blood-pool activity. Atrial volumes were measured by echocardiography.

RESULTS

Maximum and mean FDG SUV and TBRs were significantly increased in the RA (but not the LA) of patients with AF compared to those without (P < 0.01). When accounting for changes in atrial volume, the presence of AF remained a significant predictor of higher RAMAX, but not RAMEAN FDG uptake.

CONCLUSION

In patients with LV dysfunction from ischemic cardiomyopathy, LA and RA glucose metabolism are differentially altered in those with persistent atrial fibrillation. Further investigations should elucidate the temporal relationship between AF and glucose metabolic changes, as a potential target for therapy.

Sonographic characterization and surveillance of paravaginal smooth muscle tumor of uncertain malignant potential

Sonographic characterization and surveillance of paravaginal smooth muscle tumor of uncertain malignant potential. (A1) Transvaginal ultrasound with probe placed over the right vaginal wall, showing a well-defined round mass with regular contours, a mostly hypoechoic and heterogeneous echotexture, and edge shadowing, deep to the right distal third of the right vagina. (A2) Multifrequency linear probe (9-14 MHz) placed over the right labium majus revealing hyperechoic striations (arrows on A1-A2) and central flow (arrowheads on A2). (B1) Resected solid white-tan mass of bland consistency. (B2) Hematoxylin-eosin microscopy (40X) showing fusiform cells, with mild to moderate atypia. (C1) Repeat transvaginal ultrasound six-years later showing a recurrent solid oval-shaped mass with regular contour, a mostly hypoechoic heterogeneous echotexture, and an anechoic area inside the solid mass (asterisk on C2) that could represent a focus of necrosis.

18F-FDG PET/CT helps rule out malignancy in lipomatous hypertrophy of the interatrial septum with atypical MRI manifestations, to avoid unnecessary surgical treatment

Lipomatous hypertrophy of the interatrial septum (LHIS) is a rare benign heart disease characterized by excessive deposition of adipose tissue in the atrial septum with sparing fossa ovalis, which demonstrates a characteristic hourglass/dumbbell configuration. We reported a case of LHIS with inhomogenous characteristic on CMR and persistently no FDG uptake on 18F-FDG PET-CT, which is contrary to a few previous cases. This single case report suggests that in case LHIS present in-homogenous characteristic on CMR, metabolic PET imaging could be used as a complementary imaging model to decrease the concern of lipomatous neoplasms, thereby avoid unnecessary surgical therapy.

Percutaneous ultrasound-guided core needle biopsy for the diagnosis of cardiac tumors: Optimizing the treatment strategy for patients with intermural and pericardial cardiac tumors

Objective

The aims of this study are to investigate the clinical value and practical safety of ultrasound-guided percutaneous core needle biopsy on diagnosing cardiac tumor and to discuss the treatment strategy for cardiac intermural and pericardial tumors.

Methods

The clinical data were retrospectively collected for patients with intermural and pericardial cardiac tumors. The patients were divided into groups of surgical resection, surgical resection after obtaining pathological tissue by PUS-CNB, and/or radiotherapy according to the treatment modality. Ultrasound-guided aspiration biopsy was divided into cardiac tumor biopsy and extracardiac lesion biopsy according to patient conditions. The surgical time was recorded, and the safety and clinical application value of PUS-CNB for the diagnosis of cardiac tumors were evaluated in terms of complications and satisfaction with pathological sampling.

Results

A total of 18 patient cases were collected, and PUS-CNB of cardiac tumors was performed in 8 cases, with sampling times averaging 15.6 ± 3.0 min. Four cases of cardiac tumors combined with extracardiac tumors were biopsied, with puncture times averaging 13.0 ± 2.9 min. All 12 biopsied patients had no postoperative complications. Except for 1 failed biopsy, the biopsies were successful and the pathological results were consistent with the clinical diagnosis with a satisfaction rate of 91.7%. Except for two cases of surgical resection, the rest were considered for conservative treatment. Surgical resection and/or biopsy were performed in six cases, and two cases were aggravated after surgery. The final pathology of all 17 cardiac tumors was malignant.

Conclusion

PUS-CNB is safe and effective, providing a simple and undemanding method for accurate diagnosis of cardiac intermural and pericardial tumors while avoiding unnecessary open-heart surgery.

Pitfalls in Oncologic Imaging of the Pericardium on CT and PET/CT

In the oncologic setting, misinterpretation of fluid in pericardial recesses as mediastinal adenopathy or benign pericardial findings as malignant can lead to inaccurate staging and inappropriate management. Knowledge of normal pericardial anatomy, imaging features to differentiate fluid in pericardial sinuses and recesses from mediastinal adenopathy and potential pitfalls in imaging of the pericardium on CT and PET/CT is important to avoid misinterpretation.

Role of 18F-FDG PET/CT imaging in cardiac and pericardial masses

BACKGROUND

Considering the few reported cardiac masses, PET/CT in the imaging workup of cardiac masses is not well established. This retrospective study analyzed the role of 18F-FDG PET/CT imaging in cardiac/pericardial masses.

METHODS AND RESULTS

Fifty-nine patients with newly diagnosed cardiac/pericardial masses who underwent PET/CT and transthoracic echocardiography (TTE) were recruited. Echocardiographic and PET/CT characteristics were evaluated for predictive value in differentiating malignant and non-malignant lesions using histologic confirmation as the gold standard. The McNemar test was used to test the differences in sensitivity between PET/CT and TTE. 18F-FDG PET/CT had higher sensitivity in determining the malignancy of cardiac/pericardial masses compared to TTE (sensitivity, 96.6% vs 72.4%, P = .039). However, when pericardial masses were excluded from the analysis, the difference in sensitivity between the two was not statistically significant (sensitivity, 95.6% vs 78.3%, P = .219). 18F-FDG PET/CT identified two malignant pericardial masses missed on TTE, changed the diagnostic orientation of TTE in 15 patients, and found seven patients with extracardiac lesions in 29 malignant patients.

CONCLUSIONS

PET/CT was an effective additional image modality in patients with suspected malignant cardiac mass for further confirmation and to screen for potential metastasis.

Diffuse Linear Pattern of Pericardial FDG Activity in Pericardial Metastasis From Squamous Cell Lung Carcinoma

ABSTRACT

Pericardial metastasis usually shows focal pericardial FDG activity. Diffuse linear pattern of pericardial FDG activity is uncommon. We present a case of pericardial metastasis from squamous cell lung carcinoma showing diffuse linear pericardial FDG activity mimicking tuberculous pericarditis.

Side Effects of Oncologic Treatment in the Chest: Manifestations at FDG PET/CT

Fluorodeoxyglucose (FDG) PET/CT is a vital imaging technique used for staging, assessing treatment response, and restaging following completion of therapy in patients who are undergoing or have completed oncologic treatment. A variety of adverse effects from chemotherapy, targeted therapy, immunotherapy, and radiation therapy are commonly encountered in oncologic patients. It is important to be aware of the manifestations of these adverse effects seen on FDG PET/CT images to avoid misinterpreting these findings as disease progression. Furthermore, early identification of these complications is important, as it may significantly affect patient management and even lead to a change in treatment strategy. The authors focus on the FDG PET/CT manifestations of a broad spectrum of oncologic therapy-related adverse effects in the thorax, as well as some treatment-related changes that may potentially mimic malignancy. Online supplemental material is available for this article. ^©RSNA, 2021.

An image processing tool for the detection of anthracycline-induced cardiotoxicity by evaluating the myocardial metabolic activity in [18F]FDG PET/CT

Purpose

Chemotherapy-induced cardiotoxicity is one of the main complications during and after cancer treatment. While echocardiography is the most used technique in clinical practice to evaluate left ventricular (LV) dysfunction, a multimodal approach is preferred for the early detection of anthracycline-induced cardiotoxicity. In this paper, an image processing tool allowing the qualitative and quantitative analysis of myocardial metabolic activity by [¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography computed tomography (PET/CT) images, acquired routinely during and after cancer treatment, is presented.

Methods

The methodology is based on cardiac single photon emission computed tomography image processing protocols used in clinical practice. LV polar maps are created, and quantitative regional values are calculated. The tool was validated in a study group of 24 patients with Hodgkin or non-Hodgkin lymphoma (HL and NHL, respectively) treated with anthracyclines. Staging, interim and end-of-treatment [¹⁸F]FDG PET/CT images were acquired and the presented tool was used to extract the quantitative metrics of LV metabolic activity.

Results

Results show an overall increase of metabolic activity in the interim PET image acquired while on treatment compared to staging PET, which then decreased in the end-of-treatment scan. Positive correlation coefficients between staging and interim scans, and negative correlation coefficients between interim and end-of-treatment scans also support this finding. Metabolic changes occur predominantly in the septal region.

Conclusion

The proposed methodology and presented software solution provides the capability to assess quantitatively myocardial metabolism acquired by routine [¹⁸F]FDG PET/CT scanning during cancer treatment for evaluating anthracycline-induced cardiotoxicity. The [¹⁸F]FDG PET/CT septal-lateral uptake ratio is proposed as a new quantitative measure of myocardial metabolism.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11548-021-02508-9

Diffuse 18F-FDG PET/CT Uptake of the Bilateral Atrial Walls in Atrioventricular Nodal Re-entrant Tachycardia

ABSTRACT

An 84-year-old man was referred for the evaluation of a suspected gastrointestinal neoplasia. 18F-FDG PET/CT scan was performed showing, in addition to the physiological myocardial FDG uptake in the left ventricular wall, an unusual diffuse FDG uptake of the bilateral atrial walls. During his visit to the nuclear medicine unit, the patient became unwell, and an ECG was performed, suggestive of an atrioventricular nodal re-entrant tachycardia. Our case highlights the importance of including supraventricular arrhythmia such as atrioventricular nodal re-entrant tachycardia in the differential diagnosis of atrial FDG uptake.

Myocardial Glucose Metabolism Is Increased in Newly Diagnosed Lung Adenocarcinoma

BACKGROUND

Cardiac metabolism alterations may be involved in abnormalities of cancer patients' cardiovascular system. This study aimed to explore whether left ventricular myocardial glucose metabolism is altered and its related factors in newly diagnosed patients with lung adenocarcinoma (LAD) who underwent fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT).

METHODS

From our 18F-FDG PET/CT imaging database, 171 patients with newly diagnosed LAD and 43 nononcologic subjects with matched age and sex were retrospectively analyzed. The included patients underwent conventional 18F-FDG PET/CT imaging with a >12-h fasting before 18F-FDG administration. The standardized uptake values (SUVs) of the left ventricular (LV) myocardium, arterial wall, epicardial adipose tissue (EAT), spleen, and bone marrow were separately measured. Laboratory parameters and echocardiographic results were collected as well. LAD patients were divided into 2 groups based on the 95th percentile of LV maximal SUV (SUVmax) obtained from the 43 nononcologic subjects. Univariate analysis and multiple logistic regression analysis were used to identify significant factors.

RESULTS

Higher LV SUVmax was found (3.8 [2.4, 7.7] vs. 3.0 [2.0, 5.4], p = 0.052) in LAD than that in nononcologic patients, whereas no significant differences of 18F-FDG uptake were found in the arterial wall, EAT, spleen, or bone marrow between LAD patients and controls. The maximum diameter (Dmax) of the LAD lesion, SUVmax of spleen, and SUVmax of EAT were related to LV SUVmax in LAD.

CONCLUSIONS

Myocardial glucose metabolism is increased in patients with newly diagnosed LAD. Dmax of LAD lesion, spleen activity, and EAT activity contribute to the increased LV activity in LAD.

Limitations and Pitfalls of FDG-PET/CT in Infection and Inflammation

White blood cells activated by either a pathogen or as part of a systemic inflammatory disease are characterized by high energy consumption and are therefore taking up the glucose analogue PET tracer FDG avidly. It is therefore not surprising that a steadily growing body of research and clinical reports now supports the use of FDG PET/CT to diagnose a wide range of patients with non-oncological diseases. However, using FDG PET/CT in patients with infectious or inflammatory diseases has some limitations and potential pitfalls that are not necessarily as pronounced in oncology FDG PET/CT. Some of these limitations are of a general nature and related to the laborious acquisition of PET images in patients that are often acutely ill, whereas others are more disease-specific and related to the particular metabolism in some of the organs most commonly affected by infections or inflammatory disease. Both inflammatory and infectious diseases are characterized by a more diffuse and less pathognomonic pattern of FDG uptake than oncology FDG PET/CT and the affected organs also typically have some physiological FDG uptake. In addition, patients referred to PET/CT with suspected infection or inflammation are rarely treatment naïve and may have received varying doses of antibiotics, corticosteroids or other immune-modulating drugs at the time of their examination. Combined, this results in a higher rate of false positive FDG findings and also in some cases a lower sensitivity to detect active disease. In this review, we therefore discuss the limitations and pitfalls of FDG PET/CT to diagnose infections and inflammation taking these issues into consideration. Our review encompasses the most commonly encountered inflammatory and infectious diseases in head and neck, in the cardiovascular system, in the abdominal organs and in the musculoskeletal system. Finally, new developments in the field of PET/CT that may help overcome some of these limitations are briefly highlighted.

18F-FDG PET/CT in Infective Endocarditis on Papillary Muscles: A Case Report

ABSTRACT

Infective endocarditis is a serious, potentially life-threatening condition. The valve leaflets and annulus are the most commonly affected sites, but involvement of the papillary muscles is extremely rare. We present the case of a 69-year-old woman who had infective endocarditis only involving the papillary muscle on 18F-FDG PET/CT.

Series of myocardial FDG uptake requiring considerations of myocardial abnormalities in FDG-PET/CT

Distinct from cardiac PET performed with preparation to control physiological FDG uptake in the myocardium, standard FDG-PET/CT performed with 4-6 h of fasting will show variation in myocardial FDG uptake. For this reason, important signs of myocardial and pericardial abnormality revealed by myocardial FDG uptake tend to be overlooked. However, recognition of possible underlying disease will support further patient management to avoid complications due to the disease. This review demonstrates the mechanism of FDG uptake in the myocardium, discusses the factors affecting uptake, and provides notable image findings that may suggest underlying disease.

Myocardial Metastasis of Tongue Cancer: A Rare Localization

Patient: Male, 72-year-old

Final Diagnosis: Metastatic squamous cell carcinoma

Symptoms: None

Medication:—

Clinical Procedure: —

Specialty: Cardiology

Atrial Metastasis From Sarcomatoid Renal Cell Carcinoma: Integration Between 18F-FDG PET/CT and Cardiac 3-Dimensional Volume Rendering

We describe the case of a 54-year-old woman, previously submitted to nephrectomy for sarcomatoid renal cell carcinoma and treated with antibiotics because of central venous catheter infection. An F-FDG PET/CT scan was obtained that demonstrated bone and lymph node metastases and also disclosed an irregular area of highly increased uptake (SUVmax 19.4) in the right atrium. Clinical data did not suggest a relapsed infection. A contrast-enhanced CT examination of the heart enabled the diagnosis of intra-atrial metastasis. Furthermore, integration between PET and cardiac 3-dimensional volume rendering proved useful for defining the anatomical relationships between atrial metastasis and large vessels.

Primary Atrial Undifferentiated Sarcoma Found on FDG PET/CT Mimicking Cardiac Myxoma

A 52-year-old man had shortness of breath and chest discomfort for 2 months. Chest CT and MRI showed a mass in the left atrium attached to the mitral annulus without obvious enhancement. Initial diagnosis was suspected of myxoma. Preoperative FDG PET/CT demonstrated the corresponding lesion with abnormal FDG uptake, indicating a malignancy. Finally, histopathologic examination revealed primary undifferentiated sarcoma.

Late gadolinium enhancement location assessed by magnetic resonance and arrhythmogenic risk in hypertrophic cardiomyopathy

INTRODUCTION AND OBJECTIVES

Late gadolinium enhancement (LGE) extent has emerged as a predictor of sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM), however little is known about the arrhythmogenic relevance of its specific location in the left ventricle. Our aim was to analyze the influence of LGE location on the occurrence of ventricular arrhythmias (VA) and SCD in patients with HCM.

METHODS

We performed a retrospective analysis of clinical and Holter records of HCM patients who underwent cardiac magnetic resonance at our center. LGE extent and distribution were assessed using the American Heart Association 17-segment model. VA was defined as non-sustained or sustained ventricular tachycardia, ventricular fibrillation or SCD.

RESULTS

Sixty-one patients (age 57.0±16.7 years) were included and VA occurred in 24.6% (n=15). Patients with VA showed greater LGE extent than those without (7.40±5.3 vs. 3.52±3.0 segments, p=0.007). Analyzing the distribution of LGE, a set of arrhythmogenic segments (apex/basal inferior/basal anterolateral/mid inferoseptal) was found. The extent of LGE involvement in these segments was also greater in patients with VA (2.07±1.03 vs. 0.65±0.71 segments, p<0.001; area under the curve 0.861 for VA) and this difference remained significant after adjustment for potentially confounding variables.

CONCLUSIONS

The extent of LGE involvement of a set of segments with an apparent relation to cardiac areas of increased mechanical stress was significantly and independently associated with the occurrence of VA, suggesting that not only the extent but also the location of LGE is important for the assessment of SCD risk in HCM patients.

Rare Case of Cardiac Metastasis in a Patient with Cutaneous Squamous Cell Carcinoma of Foot Detected on 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography

Cutaneous squamous cell carcinoma (SCC) metastasizes most commonly to the regional lymph nodes and lungs. Metastasis to heart, although described in literature, is a very rare phenomenon. We present the ¹⁸F-fluorodeoxyglucose positron emission tomography–computed tomography findings in a 50-year-old woman who was a biopsy-proven case of SCC left foot, showing cardiac metastasis in addition to lymph nodes, lungs, and skeletal metastases.

18F-fluorodeoxyglucose positron emission tomography/computed tomography imaging review of benign lesions of the thorax

2-deoxy-2-(Fluorine-18) fluoro-D-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) has been used exclusively to diagnose malignancies. However, increased ¹⁸F-FDG uptake is not always limited to malignant lesions. This imaging review demonstrates the physiological ¹⁸F-FDG uptake of normal structures in the thorax and illustrates many benign pathological lesions with standardized uptake value >2.5. These various conditions can be broadly categorized into three groups: infective lesions, active granulomatous diseases such as sarcoidosis, noninfectious/inflammatory, or proliferative conditions such as radiation pneumonitis, postlung transplant lymphoproliferative disorders, occupational pleuropulmonary complications, and postsurgical conditions, all of which can demonstrate varying degrees of ¹⁸F-FDG uptake on PET/CT based upon the degree of inflammatory activity. Familiarity of false-positive findings improves the PET/CT evaluation accuracy of benign lesions of the thorax. Radiation exposure and surgical history correlation along with imaging cross check evaluation of radiographs and magnetic resonance images for the anatomic location remains the mainstay of PET/CT characterization of positive findings.

Myocardial 18F-FDG Uptake Pattern for Cardiovascular Risk Stratification in Patients Undergoing Oncologic PET/CT

Objective: Positron emission tomography/computed tomography with ¹⁸F-fluorodeoxy-glucose (¹⁸F-FDG-PET/CT) has become the standard staging modality in various tumor entities. Cancer patients frequently receive cardio-toxic therapies. However, routine cardiovascular assessment in oncologic patients is not performed in current clinical practice. Accordingly, this study sought to assess whether myocardial ¹⁸F-FDG uptake patterns of patients undergoing oncologic PET/CT can be used for cardiovascular risk stratification. Methods: Myocardial ¹⁸F-FDG uptake pattern was assessed in 302 patients undergoing both oncologic whole-body ¹⁸F-FDG-PET/CT and myocardial perfusion imaging by single-photon emission computed tomography (SPECT-MPI) within a six-month period. Primary outcomes were myocardial ¹⁸F-FDG uptake pattern, impaired myocardial perfusion, ongoing ischemia, myocardial scar, and left ventricular ejection fraction. Results: Among all patients, 109 (36.1%) displayed no myocardial ¹⁸F-FDG uptake, 77 (25.5%) showed diffuse myocardial ¹⁸F-FDG uptake, 24 (7.9%) showed focal ¹⁸F-FDG uptake, and 92 (30.5%) had a focal on diffuse myocardial ¹⁸F-FDG uptake pattern. In contrast to the other uptake patterns, focal myocardial ¹⁸F-FDG uptake was predominantly observed in patients with myocardial abnormalities (i.e., abnormal perfusion, impaired LVEF, myocardial ischemia, or scar). Accordingly, a multivariate logistic regression identified focal myocardial ¹⁸F-FDG uptake as a strong predictor of abnormal myocardial function/perfusion (odds ratio (OR) 5.32, 95% confidence interval (CI) 1.73–16.34, p = 0.003). Similarly, focal myocardial ¹⁸F-FDG uptake was an independent predictor of ongoing ischemia and myocardial scar (OR 4.17, 95% CI 1.53–11.4, p = 0.005 and OR 3.78, 95% CI 1.47–9.69, p = 0.006, respectively). Conclusions: Focal myocardial ¹⁸F-FDG uptake seen on oncologic PET/CT indicates a significantly increased risk for multiple myocardial abnormalities. Obtaining and taking this information into account will help to stratify patients according to risk and will reduce unnecessary cardiovascular complications in cancer patients.

Plasma DNA as a "liquid biopsy" incompletely complements tumor biopsy for identification of mutations in a case series of four patients with oligometastatic breast cancer

PURPOSE

Circulating tumor DNA in plasma may present a minimally invasive opportunity to identify tumor-derived mutations to inform selection of targeted therapies for individual patients, particularly in cases of oligometastatic disease where biopsy of multiple tumors is impractical. To assess the utility of plasma DNA as a "liquid biopsy" for precision oncology, we tested whether sequencing of plasma DNA is a reliable surrogate for sequencing of tumor DNA to identify targetable genetic alterations.

METHODS

Blood and biopsies of 1-3 tumors were obtained from 4 evaluable patients with advanced breast cancer. One patient provided samples from an additional 7 tumors post-mortem. DNA extracted from plasma, tumor tissues, and buffy coat of blood were used for probe-directed capture of all exons in 149 cancer-related genes and massively parallel sequencing. Somatic mutations in DNA from plasma and tumors were identified by comparison to buffy coat DNA.

RESULTS

Sequencing of plasma DNA identified 27.94 ± 11.81% (mean ± SD) of mutations detected in a tumor(s) from the same patient; such mutations tended to be present at high allelic frequency. The majority of mutations found in plasma DNA were not found in tumor samples. Mutations were also found in plasma that matched clinically undetectable tumors found post-mortem.

CONCLUSIONS

The incomplete overlap of genetic alteration profiles of plasma and tumors warrants caution in the sole reliance of plasma DNA to identify therapeutically targetable alterations in patients and indicates that analysis of plasma DNA complements, but does not replace, tumor DNA profiling.

TRIAL REGISTRATION

Subjects were prospectively enrolled in trial NCT01836640 (registered April 22, 2013).

Cardiac Tumors

Cardiac tumors (CTs) are extremely rare, with an incidence of approximately 0.02% in autopsy series. Primary tumors of the heart are far less common than metastatic tumors. CTs usually present with any possible clinical combination of heart failure, arrhythmias, or embolism. Echocardiography remains the first diagnostic approach when suspecting a CT which, on the other side, frequently appears unexpectedly during an echocardiographic examination. Yet, cardiac tomography and especially magnetic resonance imaging may offer several adjunctive opportunities in the diagnosis of CTs. Early and exact diagnosis is crucial for the following therapy and outcome of CTs.

Pericardial Sarcoma: "Invisible" on Radiology

Primary pericardial tumour is an extremely rare disease and an aggressive carcinoma. Its main presenting symptoms are a large recurrent hemorrhagic pericardial effusion. Imaging is the significant tool in the evaluation of pericardial lesions and of tumours. We report the case of a 17-year-old patient with recurrent hemorrhagic pericardial effusion who was diagnosed with primary pericardial fibrosarcoma. However, multiple radiological examinations, including computed tomography and fludeoxyglucose/positron emission tomography-computed tomography (^[18F] FDG/PET-CT) suggested the presence of fluid and no sign of tumour. Actually, when a patient presents with recurrent hemorrhagic pericardial effusions, pericardial tumours must be taken into account as part of the differential diagnosis.

Evaluating Positron Emission Tomography-Based Functional Imaging Changes in the Heart After Chemo-Radiation for Patients With Lung Cancer

PURPOSE

Studies have noted a link between radiation dose to the heart and overall survival (OS) for patients with lung cancer treated with chemoradiation. The purpose of this study was to characterize pre- to posttreatment cardiac metabolic changes using fluorodeoxyglucose/positron emission tomography (FDG-PET) images and to evaluate whether changes in cardiac metabolism predict for OS.

METHODS AND MATERIALS

Thirty-nine patients enrolled in a functional avoidance prospective study who had undergone pre- and postchemoradiation FDG-PET imaging were evaluated. For each patient, the pretreatment and posttreatment PET/CTs were rigidly registered to the planning CT, dose, and structure set. PET-based metabolic dose-response was assessed by comparing pretreatment to posttreatment mean standardized uptake values (SUVmean) in the heart as a function of dose-bin. OS analysis was performed by comparing SUVmean changes for patients who were alive or had died at last follow-up and by using a multivariate model to assess whether pre- to posttreatment SUVmean changes were a predictor of OS.

RESULTS

The dose-response curve revealed increasing changes in SUV as a function of cardiac dose with an average SUVmean increase of 1.7% per 10 Gy. Patients were followed for a median of 437 days (range, 201-1131 days). SUVmean change was significantly predictive of OS on multivariate analysis with a hazard ratio of 0.541 (95% confidence intervals, 0.312-0.937). Patients alive at follow-up had an average increase of 17.2% in cardiac SUVmean while patients that died had an average decrease in SUVmean decrease of 13.5% (P = .048).

CONCLUSIONS

Our data demonstrated that posttreatment SUV changes in the heart were significant indicators of dose-response and predictors of OS. The present work is hypothesis generating and must be validated in an independent cohort. If validated, our data show the potential for cardiac metabolic changes to be an early predictor for clinical outcomes.

Intracardiac melanoma metastases on 18F-FDG PET-CT-a case report and review of literature with imaging features

Cutaneous malignant melanoma is one of the few malignancies that can metastasize to the heart. It is important not to miss cardiac metastases on imaging as they are often clinically asymptomatic, but if present and undiagnosed could lead to significant cardiac compromise, arrhythmias, congestive heart failure, cardiac tamponade or transient ischaemic attacks.

Identifying intracardiac metastases on imaging often requires a multimodality approach as they can evade detection due to cardiac motion artefact; be confused with intracardiac thrombus, or be misinterpreted as a normal/anatomical finding.

We present an interesting case report of asymptomatic intracardiac melanoma metastases, initially identified on staging 18-fludeoxyglucose positron emission tomography-CT and eventually confirmed on cardiac MRI. The latter was able to differentiate myocardial metastases from tumour thrombus. We also review the relevant literature.

PET/CT Findings of a Patient with Cardiac Metastasis of Subungual Malign Melanoma

A 58-year old patient with a history of subungual malign melanoma was referred to our department for a ¹⁸F-FDG positron emission tomography (PET)/computed tomography (CT) whole body scan. An unexpected ¹⁸F-FDG uptake in left ventricule which mimicked either trombus or physiological papillary muscle was detected. Filling defect of intravenous contrast in CT images was also demonstrated in left ventricule cavity. Magnetic resonance imaging scan confirmed cardiac mass with metastatic features of malign melanoma in left ventricule.

Effects of a Ketogenic Diet on [18F]FDG-PET Imaging in a Mouse Model of Lung Cancer

PURPOSE

Myocardial uptake can hamper visualization of lung tumors, atherosclerotic plaques, and inflammatory diseases in 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) studies because it leads to spillover in adjacent structures. Several preparatory pre-imaging protocols (including dietary restrictions and drugs) have been proposed to decrease physiological [¹⁸F]FDG uptake by the heart, although their effect on tumor glucose metabolism remains largely unknown. The objective of this study was to assess the effects of a ketogenic diet (as an alternative protocol to fasting) on tumor glucose metabolism assessed by [¹⁸F]FDG positron emission tomography (PET) in a mouse model of lung cancer.

PROCEDURES

PET scans were performed 60 min after injection of 18.5 MBq of [¹⁸F]FDG. PET data were collected for 45 min, and an x-ray computed tomograph (CT) image was acquired after the PET scan. A PET/CT study was obtained for each mouse after fasting and after the ketogenic diet. Quantitative data were obtained from regions of interest in the left ventricular myocardium and lung tumor.

RESULTS

Three days on a ketogenic diet decreased mean standard uptake value (SUVmean) in the myocardium (SUVmean 0.95 ± 0.36) more than one night of fasting (SUVmean 1.64 ± 0.93). Tumor uptake did not change under either dietary condition.

CONCLUSIONS

These results show that 3 days on high-fat diets prior to [¹⁸F]FDG-PET imaging does not change tumor glucose metabolism compared with one night of fasting, although high-fat diets suppress myocardial [¹⁸F]FDG uptake better than fasting.

Focal mass-like cardiac uptake on oncologic FDG PET/CT: Real lesion or atypical pattern of physiologic uptake?

BACKGROUND

Cardiac uptake on oncologic FDG PET/CT can be unpredictable. Focal or mass-like cardiac uptake not confined to normal pattern is a real challenge for interpretation due to great variability in physiologic uptake and rarity of either primary or metastatic cardiac neoplasms.

METHODS AND RESULTS

Eight patients with suspicious mass-like cardiac uptake on oncologic FDG PET/CT were retrospectively analyzed with correlation to cardiac workups including contrast CT, echocardiography, and repeat PET/CT. Four patients had real cardiac lesions or metastases. Focal uptake was benign and might represent papillary muscle in the other four. SUVmax ratio between the cardiac focus and surrounding background cardiac uptake was statistically higher in the true-positive group than that in the false-positive group. In addition, the patients with true-positive cardiac uptake had more diffuse distant metastases compared to those with false-positive cardiac uptake.

CONCLUSIONS

Focal suspicious cardiac uptake on oncology FDG PET/CT warranted further evaluation. SUVmax ratio between the cardiac focus and surrounding background cardiac uptake and status of distant metastases might help to differentiate malignant from benign nature of the focal cardiac uptake on FDG PET/CT. Focal uptake of the right ventricle on oncologic FDG PET/CT is more likely suggestive of a neoplasm.

The impact of infection and inflammation in oncologic 18F-FDG PET/CT imaging

Sites of infection and inflammation can be misleading in oncology PET/CT imaging because these areas commonly show ¹⁸F-FDG activity. Caution in the interpretation must be taken to avoid the misdiagnosis of malignancy. Utilization of both CT findings as well as patient history can help differentiate benign infectious and inflammatory processes from malignancy, although occasionally additional work-up may be required. This article discusses the mechanism of ¹⁸F-FDG uptake in infection and inflammation with illustrative examples.

Cardiovascular Manifestations of Erdheim-Chester's Disease: A Case Series

Erdheim-Chester Disease is a rare entity, classified as an inflammatory myeloid neoplasm, with an unknown incidence, occurring preferentially in men after 50 years of age. Classically, it has a multisystemic presentation, with the skeletal system being the most frequently affected (90% of the patients), followed by genitourinary involvement in 60% of cases and central nervous system in the pituitary and diabetes insipidus in 25% of the cases. Cardiovascular manifestations are present in more than half of the patients, with aortic infiltration and atrial pseudotumor being the most common forms.

Gastric lipomas: a case series and review of a rare tumor

The purpose of the study was to investigate and review the multimodality imaging findings of gastric lipomas. Seven patients with gastric lipomas identified by CT imaging at a single institution between 2003 and 2017 were retrospectively evaluated. Patient demographics, clinical presentation, non-invasive imaging, endoscopic, and pathological findings were recorded.The most common location for gastric lipoma was the gastric antrum (3/7). The mean lipoma size was 2.7 cm ± 0.8 cm. Six out of seven lipomas demonstrated homogenous fat attenuation with mean Hounsfield units (HU) between -80 and -120. A single lipoma measuring -50 HU demonstrated soft tissue septations. In addition to routine CT and MRI, gastric lipomas were diagnosed on the low-dose CT protocols such as coronary calcium scoring, renal stone, and positron emission tomography-CT (PET-CT). Our CT findings corroborate those reported previously. Soft tissue septations visualized in one lesion likely represented post-biopsy changes, adding this etiology to a differential which previously included only ulceration. Cases characterized by MRI are rare in the literature, and our study provides one such example. To our knowledge this study represents the first documentation of gastric lipomas on PET-CT and other low-dose CT imaging protocols.

Right Heart Mass in Transit with a Hemorrhagic Pericardial Effusion: A Diagnostic Dilemma

Metastatic disease to the heart is more often a post-mortem diagnosis due to non-specific symptoms and a low index of suspicion. Our case is a unique presentation of a rare case of cardiac metastasis from oropharyngeal cancer, which eluded echocardiographic diagnosis despite the presence of a hemorrhagic pericardial effusion. The cardiac metastasis, in fact, starts as pericardial seeding, as illustrated by the positron emission tomography (PET) imaging. The pericardial metastatic disease then becomes rapidly invasive into the cardiac chambers, hence presenting as a large mass on the echocardiogram and computed tomography (CT) scan of the chest. This is the first such case of pericardial metastasis from a squamous cell carcinoma of the tongue being reported and highlights the importance of an aggressive multimodality diagnostic approach in cases where such a clinical suspicion exists. While a two-dimensional (2D) echocardiogram is the most readily available modality, we recommend that this is complemented by the use of a three-dimensional (3D) echocardiogram, as well as metabolic and radiologic imaging with PET and CT scans.

PET/CT Evaluation of Cardiac Sarcoidosis

The increasing implementation of advanced cardiovascular imaging in the form of cardiac PET/CT has had a significant impact on the management of cardiac sarcoidosis, which continues to evolve. This review summarizes the role of PET/CT imaging in sarcoidosis with a specific focus on (1) indications, (2) patient preparation, (3) test performance, (4) study interpretation, (5) clinical relevance of findings, (6) comparison to alternative imaging modalities, and finally (7) introduction of areas of anticipated development and research.