Alternative Nuclear Imaging Tools for Infection Imaging

Purpose of Review Cardiovascular infections are serious disease associated with high morbidity and mortality. Their diagnosis is challenging, requiring a proper management for a prompt recognition of the clinical manifestations, and a multidisciplinary approach involving cardiologists, cardiothoracic surgeons, infectious diseases specialist, imagers, and microbiologists. Imaging plays a central role in the diagnostic workout, including molecular imaging techniques. In this setting, two different strategies might be used to image infections: the first is based on the use of agents targeting the microorganism responsible for the infection. Alternatively, we can target the components of the pathophysiological changes of the inflammatory process and/or the host response to the infectious pathogen can be considered. Understanding the strength and limitations of each strategy is crucial to select the most appropriate imaging tool. Recent Findings Currently, multislice computed tomography (MSCT) and nuclear imaging (F-18-fluorodeoxyglucose positron emission tomography/computed tomography, and leucocyte scintigraphy) are part of the diagnostic strategies. The main role of nuclear medicine imaging (PET/CT and SPECT/CT) is the confirmation of valve/CIED involvement and/or associated perivalvular infection and the detection of distant septic embolism. Proper patients' preparation, imaging acquisition, and reconstruction as well as imaging reading are crucial to maximize the diagnostic information. In this manuscript, we described the use of molecular imaging techniques, in particular WBC imaging, in patients with infective endocarditis, cardiovascular implantable electronic device infections, and infections of composite aortic graft, underlying the strength and limitations of such approached as compared to the other imaging modalities

Prosthetic Valve Endocarditis

Prosthetic valve infective endocarditis (PVE) is associated with high morbidity and mortality. With the increasing number of prostheses implanted every year, the incidence of PVE is expected to rise. The diagnosis of PVE is challenging as blood cultures are often negative and the sensitivity of echocardiography is suboptimal in the presence of prosthetic valves. In 2015, the European Society of Cardiology introduced 18F-fluorodeoxyglucose–positron emission tomography/computed tomography (FDG-PET/CT) as a major criterion for the diagnosis of PVE, based on its ability to identify valve infection and to detect septic emboli. In addition, FDG-PET/CT can detect PVE portal of entry, which may lead to change in management. This chapter will discuss the epidemiology and clinical presentations of PVE. In addition, the role of FDG-PET/CT in PVE as well as optimal imaging protocols will be reviewed.</p

What to Trust, PSA or [Ga-68]Ga-PSMA-11:Learn from Experience

Brain metastases from prostate cancer typically occur in the more advanced stages of the disease. Clinically, the early diagnosis of visceral disease is crucial, impacting on patient's management and prognosis. Although magnetic resonance imaging (MRI) is the modality of choice for the detection of brain metastases, it is not routinely performed in the surveillance of prostate cancer patients unless neurological manifestations appear. Prostate-specific membrane antigen (PSMA) is a glycoprotein, a membrane-bound metallopeptidase, overexpressed in more than 90% of prostate cancer cells. This molecular target is a suitable tissue biomarker for prostate cancer functional imaging. We present a case of a 73-year gentleman diagnosed with prostate adenocarcinoma and surgically treated (pT3bN1Mx, Gleason Score of 9) in February 2016. Subsequently, he underwent androgen deprivation therapy because of the occurrence of a bone metastasis. Between 2016 and January 2019 PSA levels were maintained under control. Starting from September 2019, it progressively raised up to 0.85 ng/mL with a doubling time of 3.3 months. Therefore, he performed a [Ga-68]Ga-PSMA-11 PET/CT which showed a focal radiopharmaceutical uptake in the right temporal lobe corresponding to the presence of a rounded cystic lesion on brain MRI. The subsequent excisional biopsy diagnosed a prostate adenocarcinoma metastasis. PSMA expression has been reported in brain parenchyma after ischemic strokes and in some brain tumors including gliomas, meningiomas, and neurofibromas. In our case, the lack of symptoms and the relatively low PSA level raised questions about the nature of the lesion, posing the differential diagnosis between brain metastases and primary brain tumor. Finally, our case shows the capability of [Ga-68]Ga-PSMA-11 PET/CT to detect metachronous distant brain metastases in a low biochemical recurrent asymptomatic prostate cancer patient, indicating that proper acquisition - from the vertex to thigh - should be always considered, regardless of the PSA level

[¹⁸F]FMCH PET/CT biomarkers and similarity analysis to refine the definition of oligometastatic prostate cancer

Background:The role of image-derived biomarkers in recurrent oligometastatic Prostate Cancer (PCa) is unexplored. This paper aimed to evaluate [18F]FMCH PET/CT radiomic analysis in patients with recurrent PCa after primary radical therapy. Specifically, we tested intra-patient lesions similarity in oligometastatic and plurimetastatic PCa, comparing the two most used definitions of oligometastatic disease.Methods:PCa patients eligible for [18F]FMCH PET/CT presenting biochemical failure after first-line curative treat-ments were invited to participate in this prospective observational trial. PET/CT images of 92 patients were visually and quantitatively analyzed. Each patient was classified as oligometastatic or plurimetastatic according to the total number of detected lesions (up to 3 and up to 5 or &gt; 3 and &gt; 5, respectively). Univariate and intra-patient lesions’ similarity analysis were performed.Results: [18F]FMCH PET/CT identified 370 lesions, anatomically classified as regional lymph nodes and distant metastases. Thirty-eight and 54 patients were designed oligometastatic and plurimetastatic, respectively, using a 3-lesion threshold. The number of oligometastic scaled up to 60 patients (thus 32 plurimetastatic patients) with a 5-lesion threshold. Similarity analysis showed high lesions’ heterogeneity. Grouping patients according to the number of metastases, patients with oligometastatic PCa defined with a 5-lesion threshold presented lesions heterogene-ity comparable to plurimetastic patients. Lesions within patients having a limited tumor burden as defined by three lesions were characterized by less heterogeneity.Conclusions:We found a comparable heterogeneity between patients with up to five lesions and plurimetastic patients, while patients with up to three lesions were less heterogeneous than plurimetastatic patients, featuring dif-ferent cells phenotypes in the two groups. Our results supported the use of a 3-lesion threshold to define oligometa-static PCa

[18F]-Fludeoxyglucose Positron Emission Tomography/Computed Tomography with Radiomics Analysis in Patients Undergoing Aortic In-Situ Reconstruction with Cryopreserved Allografts

The aim of this study was to evaluate the effectiveness of positron emission tomography/computed tomography with [18F]-fludeoxyglucose (FDG-PET/CT) and radiomics analysis in detecting differences between the native aorta and the abdominal aortic allograft after the total eradication of infection in patients undergoing infected graft removal and in situ reconstruction with cryopreserved allografts

Role of Multimodal Imaging in Patients With Suspected Infections After the Bentall Procedure

Purpose: This study aimed to assess the diagnostic performances of multimodal imaging [i.e., white blood cell single-photon emission computed tomography/CT ((99m)Tc-HMPAO-WBC SPECT/CT) and 18-fluoride-fluorodeoxyglucose positron emission tomography/CT ([(18)F]FDG PET/CT)] in patients with suspected infection after the Bentall procedure, proposing new specific diagnostic criteria for the diagnosis. Methods: Between January 2009 and December 2019, we selected within a cardiovascular infections registry, 76 surgically treated patients (27 women and 49 men, median 66 years, and range 29–83 years). All the patients underwent molecular imaging for a suspected infection after the replacement of the aortic valve and ascending aorta according to the Bentall procedure. We analyzed 98 scans including 49 (99m)Tc-WBC and 49 [(18)F]FDG PET/CT. A total of 22 patients with very early/early suspected infection (<3 months after surgery) were imaged with both the techniques. Positive imaging was classified according to the anatomical site of increased uptake: to the aortic valve (AV), to both the AV and AV tube graft (AVTG) or to the TG, to surrounding tissue, and/or to extracardiac sites (embolic events or other sites of concomitant infection). Standard clinical workup included in all the patients having echocardiography/CT, blood culture, and the Duke criteria. Pretest probability and positive/negative likelihood ratio were calculated. Sensitivity and specificity of (99m)Tc labeled hexamethylpropylene amine oxime-WBC SPECT/CT ((99m)Tc-HMPAO-WBC SPECT/CT) and [(18)F]FDG PET/CT imaging were calculated by using microbiology (n = 35) or clinical follow-up (n = 41) as final diagnosis. (99m)Tc-HMPAO-WBC scintigraphy and [(18)F]FDG PET/CT findings were compared with 95% CIs by using the McNemar test to those of echocardiography/CT, blood culture, and the Duke criteria. Results: Sensitivity, specificity, and accuracy of (99m)Tc-HMPAO-WBC were 86, 92, and 88%, respectively, with a slightly higher sensitivity for tube graft infection (TGI) as compared to isolated AV and combined AVTG. Overall, sensitivity, specificity, and accuracy of [(18)F]FDG PET/CT were 97, 73, and 90%, respectively. In 22 patients with suspected very early and early postsurgical infections, the two imaging modalities were concordant in 17 cases [10 true positive (TP) and 7 true negative (TN)]. [(18)F]FDG PET/CT presented a higher sensitivity than (99m)Tc-HMPAO-WBC scan. (99m)Tc-HMPAO-WBC scan correctly classified as negative three false-positive (FP) PET/CT findings. Conclusion: Our findings supported the use of (99m)Tc-HMPAO-WBC SPECT/CT and [(18)F]FDG PET/CT in patients with suspicion infection after the Bentall procedure early in the course of the disease onset to confirm the diagnosis and provide a comprehensive assessment of disease burden through the proposed criteria

Advance texture analysis: a new step in imaging of IE

[18F]FDG-PET/CT has been recently introduced in the diagnostic algorithm for the diagnosis of infective endocarditis (IE). [18F]FDG PET/CT positivity at the valve site, which is a major criteria of the 2015 ESC criteria, is generally characterized by visual analysis. The advantage of semiquantitative assessment is still matter of discussion. In this study we aim to apply advanced texture features analysis, which application has been mainly focused on cancer imaging, to IE

Role of Multimodal Imaging in Patients With Suspected Infections After the Bentall Procedure

Purpose: This study aimed to assess the diagnostic performances of multimodal imaging [i.e., white blood cell single-photon emission computed tomography/CT (Tc-99m-HMPAO-WBC SPECT/CT) and 18-fluoride-fluorodeoxyglucose positron emission tomography/CT ([F-18]FDG PET/CT)] in patients with suspected infection after the Bentall procedure, proposing new specific diagnostic criteria for the diagnosis.Methods: Between January 2009 and December 2019, we selected within a cardiovascular infections registry, 76 surgically treated patients (27 women and 49 men, median 66 years, and range 29-83 years). All the patients underwent molecular imaging for a suspected infection after the replacement of the aortic valve and ascending aorta according to the Bentall procedure. We analyzed 98 scans including 49 Tc-99m-WBC and 49 [F-18]FDG PET/CT. A total of 22 patients with very early/early suspected infection (</p