Iterative regularization for constrained minimization formulations of nonlinear inverse problems

In this paper we study the formulation of inverse problems as constrained minimization problems and their iterative solution by gradient or Newton type methods. We carry out a convergence analysis in the sense of regularization methods and discuss applicability to the problem of identifying the spatially varying diffusivity in an elliptic PDE from different sets of observations. Among these is a novel hybrid imaging technology known as impedance acoustic tomography, for which we provide numerical experiments.

Adapting Imaging Protocols for PET-CT and PET-MRI for Immunotherapy Monitoring

Hybrid imaging with positron emission tomography (PET) in combination with computer tomography (CT) is a well-established diagnostic tool in oncological staging and restaging. The combination of PET with magnetic resonance imaging (MRI) as a clinical scanner was introduced approximately 10 years ago. Although MRI provides superb soft tissue contrast and functional information without the radiation exposure of CT, PET-MRI is not as widely introduced in oncologic imaging as PET-CT. One reason for this hesitancy lies in the relatively long acquisition times for a PET-MRI scan, if the full diagnostic potential of MRI is exploited. In this review, we discuss the possible advantages of combined imaging protocols of PET-CT and PET-MRI, within the context of staging and restaging of patients under immunotherapy, in order to achieve “multi-hybrid imaging” in one single patient visit.

Intraoperative Guidance Using Hyperspectral Imaging: A Review for Surgeons

Hyperspectral imaging (HSI) is a novel optical imaging modality, which has recently found diverse applications in the medical field. HSI is a hybrid imaging modality, combining a digital photographic camera with a spectrographic unit, and it allows for a contactless and non-destructive biochemical analysis of living tissue. HSI provides quantitative and qualitative information of the tissue composition at molecular level in a contrast-free manner, hence making it possible to objectively discriminate between different tissue types and between healthy and pathological tissue. Over the last two decades, HSI has been increasingly used in the medical field, and only recently it has found an application in the operating room. In the last few years, several research groups have used this imaging modality as an intraoperative guidance tool within different surgical disciplines. Despite its great potential, HSI still remains far from being routinely used in the daily surgical practice, since it is still largely unknown to most of the surgical community. The aim of this study is to provide clinical surgeons with an overview of the capabilities, current limitations, and future directions of HSI for intraoperative guidance.

Radiotheranostics is here to help

The COVID-19 pandemic did not diminish interest in radiotheranostics. However, the demand for visualization of pathological processes using cross-sectional and hybrid imaging (CT, MRI, SPECT, and PET) is increased. Over the past 15 months, the world has seen an exponential increase in investment in new radiopharmaceuticals for radiotheranostics. The list of antibodies and ligands labeled with "medical" radioactive isotopes is expanding as the molecular mechanisms of regulation and implementation of metabolic processes become clearer. The range of diagnostic and therapeutic radioactive isotopes is also expanding, ultimately increasing the range and availability of radiotherapy in nuclear medicine centers worldwide. It is necessary to unite the efforts of physicists, radiopharmacists, chemists, biologists, doctors, and mathematicians to develop radio technology. Usage and improvement of personalized dosimetry for planning radionuclide therapy is also a priority. For example, the International Foundation Oncidium helps with information and exchange of experience, while the international diagnostic study NOBLE increases the availability and reduces the cost of PSMA receptor scintigraphy. An association for the development of theranostics was created to intensify the integration renewal of nuclear medicine.