Hybrid Positron Emission Tomography Imaging Research Articles

Sinonasal mucosal melanoma treatment response assessment to immune checkpoint inhibitors using hybrid positron emission tomography imaging

The purpose of this retrospective study was to investigate response of sinonasal mucosal melanoma (SMM) patients to treatment with immune checkpoint inhibitors (ICI), using hybrid PET imaging. Fifteen SMM patients underwent hybrid PET imaging before and three months after initiation of ICI. The disease-specific survival (DSS) was calculated. Quantitative PET parameters of the primary tumor and their association with DSS and therapy response were investigated. Nine of the fifteen (60%) patients responded to ICI therapy. Patients with therapy response depicted on hybrid PET imaging had better DSS than those without (p = 0.0058). Quantitative PET parameters of the initial PET harbored no association with DSS or therapy response. However, these findings lack of sufficient statistical power and must be interpreted with caution. The first restaging PET-imaging after ICI initiation can help stratify patients with regard to DSS.

Whole-body hybrid positron emission tomography imaging yields clinically relevant information in the staging and restaging of sinonasal tumors.

BackgroundWhole‐body hybrid positron emission tomography (PET) imaging is increasingly used for sinonasal tumors. However, only empirical data exist on the additional, clinically relevant information derived from these techniques.MethodsThis study included 96 regionalized magnetic resonance imaging (MRI) of the sinonasal tract/neck and separate hybrid FDG‐PET/CT or FDG‐PET/MRI in 74 patients. Additional radiological information (ARI) obtained from each hybrid examination was analyzed and its clinically relevance was determined. Clinically relevant information (CRI) was categorized with regard to primary tumor site, regional lymph node metastases, distant metastases, second primary tumors, and non‐neoplastic findings.ResultsA total of 45/96 (46.9%) hybrid PET examinations revealed ARI. CRI was found in 32/96 (33.3%) examinations and concerned the primary tumor site (6.1%), regional lymph node metastases (4.1%), distant metastases (14.3%), second primary tumors (7.3%), and non‐neoplastic findings (5.1%).ConclusionsHybrid PET imaging yields additional radiological information translating into clinically relevant information in a substantial proportion of patients with sinonasal tumors.

Novel positron emission tomography tracers for imaging of rheumatoid arthritis.

Positron emission tomography (PET) is a nuclear imaging modality that relies on visualization of molecular targets in tissues, which is nowadays combined with a structural imaging modality such as computed tomography (CT) or Magnetic Resonance Imaging (MRI) and referred to as hybrid PET imaging. This technique allows to image specific immunological targets in rheumatoid arthritis (RA). Moreover, quantification of the PET signal enables highly sensitive monitoring of therapeutic effects on the molecular target. PET may also aid in stratification of the immuno-phenotype at baseline in order to develop personalized therapy. In this systematic review we will provide an overview of novel PET tracers, investigated in the context of RA, either pre-clinically, or clinically, that specifically visualize immune cells or stromal cells, as well as other factors and processes that contribute to pathology. The potential of these tracers in RA diagnosis, disease monitoring, and prediction of treatment outcome will be discussed. In addition, novel PET tracers established within the field of oncology that may be of use in RA will also be reviewed in order to expand the future opportunities of PET imaging in RA.

Hybrid positron emission tomography imaging for initial staging of sinonasal tumors: Total lesion glycolysis as prognosticator of treatment response.

To assess hybrid positron emission tomography (PET) imaging in the initial staging and outcome prediction of sinonasal malignancies. Retrospective study on patients with sinonasal malignancies undergoing hybrid PET imaging for initial staging. Complete remission (CR) was achieved in 45 of 65 patients (69.2%). Overall sensitivity for detection of primaries using 18F-fluoro-deoxy-d-glucose PET (FDG-PET) was 95.4%, for lymph node metastases 100% and distant metastases (DM) 100%. On univariate analysis, PET parameter total lesion glycolysis (TLG) was associated with achieving CR after primary treatment (176.8 ± 157.2 vs 83.7 ± 110.8, P = .03). Multivariate logistic regression demonstrated that TLG adjusted for the T classification best predicted achievement of CR. Hybrid PET imaging yields an excellent sensitivity in detecting primary tumors, lymph node metastases and DM in sinonasal malignancies. TLG of the primary tumor is an independent prognostic factor for achieving CR after initial treatment.

Imaging residual inflammatory cardiovascular risk.

Targeting residual cardiovascular risk in primary and secondary prevention, would allow deployment of novel therapeutic agents, facilitating precision medicine. For example, lowering vascular inflammation is a promising strategy to reduce the residual inflammatory cardiovascular risk in patients already receiving optimal medical therapy, but prescribing novel anti-inflammatory treatments will be problematic due to the lack of specific companion diagnostic tests, to guide their targeted use in clinical practice. Currently available tests for the detection of coronary inflammation are either non-specific for the cardiovascular system (e.g. plasma biomarkers) or expensive and not readily available (e.g. hybrid positron emission tomography imaging). Recent technological advancements in coronary computed tomography angiography (CCTA) allow non-invasive detection of high-risk plaque features (positive remodelling, spotty calcification, low attenuation plaque, and napkin-ring sign) and help identify the vulnerable patient, but they provide only indirectly information about coronary inflammation. Perivascular fat attenuation index (FAI), a novel method for assessing coronary inflammation by analysing routine CCTA, captures changes in the perivascular adipose tissue composition driven by inflammatory signals coming from the inflamed coronary artery, by analysing the three-dimensional gradients of perivascular attenuation, followed by adjustments for technical, anatomical, and biological factors. By detecting vascular inflammation, perivascular FAI enhances cardiovascular risk discrimination which could aid more cost-effective deployment of novel therapeutic agents. In this article, we present the existing non-invasive modalities for the detection of coronary inflammation and provide a practical guide for their use in clinical practice.

Clinical applications of PET/MRI: current status and future perspectives.

Fully integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) scanners have been available for a few years. Since then, the number of scanner installations and published studies have been growing. While feasibility of integrated PET/MRI has been demonstrated for many clinical and preclinical imaging applications, now those applications where PET/MRI provides a clear benefit in comparison to the established reference standards need to be identified. The current data show that those particular applications demanding multiparametric imaging capabilities, high soft tissue contrast and/or lower radiation dose seem to benefit from this novel hybrid modality. Promising results have been obtained in whole-body cancer staging in non-small cell lung cancer and multiparametric tumor imaging. Furthermore, integrated PET/MRI appears to have added value in oncologic applications requiring high soft tissue contrast such as assessment of liver metastases of neuroendocrine tumors or prostate cancer imaging. Potential benefit of integrated PET/MRI has also been demonstrated for cardiac (i.e., myocardial viability, cardiac sarcoidosis) and brain (i.e., glioma grading, Alzheimer's disease) imaging, where MRI is the predominant modality. The lower radiation dose compared to PET/computed tomography will be particularly valuable in the imaging of young patients with potentially curable diseases.However, further clinical studies and technical innovation on scanner hard- and software are needed. Also, agreements on adequate refunding of PET/MRI examinations need to be reached. Finally, the translation of new PET tracers from preclinical evaluation into clinical applications is expected to foster the entire field of hybrid PET imaging, including PET/MRI.

Preoperative Imaging of Charcot Neuroarthropathy in Diabetic Patients: Comparison of Ring PET, Hybrid PET, and Magnetic Resonance Imaging

The treatment of Charcot neuroarthropathy in the feet of diabetic patients has undergone fundamental changes in the last few years. Formerly, treatment was almost exclusively limited to nonoperative measures; since the late 1990s, however, current practice has shifted to early, stage-appropriate surgical therapy. The objective of this prospective study was to investigate the value of two types of positron emission tomography (PET) in the preoperative evaluation of diabetic patients with Charcot foot deformities. Ring [(18)F]FDG (2-fluoro-2-deoxy-glucose) and hybrid PET were compared to magnetic resonance imaging (MRI). MRI, ring PET, and hybrid PET imaging were used as part of the preoperative evaluation of 16 patients with type II diabetes mellitus. The diagnosis of Charcot neuropathy of the foot requiring operative treatment had been made on the basis of clinical and radiographic criteria. Of 39 Charcot lesions confirmed at surgery, 37 were detected by ring PET, 30 by hybrid PET, and 31 by MRI. PET (ring or hybrid) can be used in the evaluation of patients with metal implants that would compromise the accuracy of MRI. Another advantage of PET is its ability to distinguish between inflammatory and infectious soft-tissue lesions, and between osteomyelitis and Charcot neuroarthropathy. The differentiation between Charcot neuroarthropathy and florid osteomyelitis provides the surgeon with important additional information that often is unavailable from MRI. Because it provides important additional data, ring PET may be preferable to radiography and MRI in the preoperative evaluation of patients with Charcot neuroarthropathy of the foot. Hybrid PET, because of its poorer resolution compared to ring PET, appears less suitable for routine clinical application.

Optimization of septal spacing in hybrid PET using estimation task performance

Hybrid PET imaging, a low cost alternative to dedicated PET, is now commonly used in many clinics. The major factors that limit image quality of hybrid positron emission tomography (PET) systems are a limited count-rate capability, and a low coincidence fraction (i.e., trues to singles ratio). Axial collimation or slats are typically used to reduce single (unpaired) photons from impinging on the detector face. Unfortunately, axial collimation also prevents a number of true coincidences from being detected. In this study, we have used a multi-parameter estimation task to study quantitation performance resulting from projection data obtained using a triple-head system with different levels of axial collimator septal spacing. Specifically, the task is the estimation of amplitude (A) and size (R) of a three-dimensional Gaussian function embedded in a uniform cylindrical background. To evaluate task performance, the bias and variance of maximum-likelihood estimates of the parameters are studied by forming an approximate joint probability density function for the estimates. It was observed that as projection data noise increases; joint PDFs of the estimates become more skewed, with a larger difference between the variance of estimates and their minimum variance bound (Cramer-Rao bound). Estimator performance varied as a function of lesion location, which was expected since coincidence sensitivity for rotating hybrid PET systems with axial collimation is position dependent. In general, results showed that approximately 2.0-cm septal spacing provided projection data with the best overall estimator performance for lesions located within the central 20-cm axial field-of-view.