Benefits of Hybrid SPECT/CT for 111In-Oxine- and Tc-99m-Hexamethylpropylene Amine Oxime-Labeled Leukocyte Imaging

89Zr-leukocyte labelling for cell trafficking: in vitro and preclinical investigations

BACKGROUND

The non-invasive imaging of leukocyte trafficking to assess inflammatory areas and monitor immunotherapy is currently generating great interest. There is a need to develop more robust cell labelling and imaging approaches to track living cells. Positron emission tomography (PET), a highly sensitive molecular imaging technique, allows precise signals to be produced from radiolabelled moieties. Here, we developed a novel leukocyte labelling approach with the PET radioisotope zirconium-89 (89Zr, half-life of 78.4 h). Experiments were carried out using human leukocytes, freshly isolated from whole human blood.

RESULTS

The 89Zr-leukocyte labelling efficiency ranged from 46 to 87% after 30-60 min. Radioactivity concentrations of labelled cells were up to 0.28 MBq/1 million cells. Systemically administered 89Zr-labelled leukocytes produced high-contrast murine PET images at 1 h-5 days post injection. Murine biodistribution data showed that cells primarily distributed to the lung, liver, and spleen at 1 h post injection, and are then gradually trafficked to liver and spleen over 5 days. Histological analysis demonstrated that exogenously 89Zr-labelled human leukocytes were present in the lung, liver, and spleen at 1 h post injection. However, intravenously injected free [89Zr]Zr4+ ion showed retention only in the bone with no radioactivity in the lung at 5 days post injection, which implied good stability of radiolabelled leukocytes in vivo.

CONCLUSIONS

Our study presents a stable and generic radiolabelling technique to track leukocytes with PET imaging and shows great potential for further applications in inflammatory cell and other types of cell trafficking studies.

From Pixels to Pathology: Employing Computer Vision to Decode Chest Diseases in Medical Images

Radiology has been a pioneer in the healthcare industry's digital transformation, incorporating digital imaging systems like picture archiving and communication system (PACS) and teleradiology over the past thirty years. This shift has reshaped radiology services, positioning the field at a crucial junction for potential evolution into an integrated diagnostic service through artificial intelligence and machine learning. These technologies offer advanced tools for radiology's transformation. The radiology community has advanced computer-aided diagnosis (CAD) tools using machine learning techniques, notably deep learning convolutional neural networks (CNNs), for medical image pattern recognition. However, the integration of CAD tools into clinical practice has been hindered by challenges in workflow integration, unclear business models, and limited clinical benefits, despite development dating back to the 1990s. This comprehensive review focuses on detecting chest-related diseases through techniques like chest X-rays (CXRs), magnetic resonance imaging (MRI), nuclear medicine, and computed tomography (CT) scans. It examines the utilization of computer-aided programs by researchers for disease detection, addressing key areas: the role of computer-aided programs in disease detection advancement, recent developments in MRI, CXR, radioactive tracers, and CT scans for chest disease identification, research gaps for more effective development, and the incorporation of machine learning programs into diagnostic tools.

Theranostic chimeric antigen receptor (CAR)-T cells: Insight into recent trends and challenges in solid tumors

Cell therapy has reached significant milestones in various life-threatening diseases, including cancer. Cell therapy using fluorescent and radiolabeled chimeric antigen receptor (CAR)-T cell is a successful strategy for diagnosing or treating malignancies. Since cell therapy approaches have different results in cancers, the success of hematological cancers has yet to transfer to solid tumor therapy, leading to more casualties. Therefore, there are many areas for improvement in the cell therapy platform. Understanding the therapeutic barriers associated with solid cancers through cell tracking and molecular imaging may provide a platform for effectively delivering CAR-T cells into solid tumors. This review describes CAR-T cells' role in treating solid and non-solid tumors and recent advances. Furthermore, we discuss the main obstacles, mechanism of action, novel strategies and solutions to overcome the challenges from molecular imaging and cell tracking perspectives.

Current and potential roles of immuno-PET/-SPECT in CAR T-cell therapy

Chimeric antigen receptor (CAR) T-cell therapies have evolved as breakthrough treatment options for the management of hematological malignancies and are also being developed as therapeutics for solid tumors. However, despite the impressive patient responses from CD19-directed CAR T-cell therapies, ~ 40%-60% of these patients' cancers eventually relapse, with variable prognosis. Such relapses may occur due to a combination of molecular resistance mechanisms, including antigen loss or mutations, T-cell exhaustion, and progression of the immunosuppressive tumor microenvironment. This class of therapeutics is also associated with certain unique toxicities, such as cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, and other "on-target, off-tumor" toxicities, as well as anaphylactic effects. Furthermore, manufacturing limitations and challenges associated with solid tumor infiltration have delayed extensive applications. The molecular imaging modalities of immunological positron emission tomography and single-photon emission computed tomography (immuno-PET/-SPECT) offer a target-specific and highly sensitive, quantitative, non-invasive platform for longitudinal detection of dynamic variations in target antigen expression in the body. Leveraging these imaging strategies as guidance tools for use with CAR T-cell therapies may enable the timely identification of resistance mechanisms and/or toxic events when they occur, permitting effective therapeutic interventions. In addition, the utilization of these approaches in tracking the CAR T-cell pharmacokinetics during product development and optimization may help to assess their efficacy and accordingly to predict treatment outcomes. In this review, we focus on current challenges and potential opportunities in the application of immuno-PET/-SPECT imaging strategies to address the challenges encountered with CAR T-cell therapies.

Application of Advanced Imaging Modalities in Veterinary Medicine: A Review

Veterinary anatomy has traditionally relied on detailed dissections to produce anatomical illustrations, but modern imaging modalities, now represent an enormous resource that allows for fast non-invasive visualizations in living animals for clinical and research purposes. In this review, advanced anatomical imaging modalities and their applications, safety issues, challenges, and future prospects of the techniques commonly employed for animal imaging would be highlighted. The quality of diagnostic imaging equipment in veterinary practice has greatly improved. Recent advances made in veterinary advanced imaging specifically about cross-sectional modalities (CT and MRI), nuclear medicine (PET, SPECT), and dual imaging modalities (PET/CT, PET/MR, and SPECT/CT) have become widely available, leading to greater demands and expectations from veterinary clients. These modalities allow for the creation of three-dimensional representations that can be of considerable value in the dissemination of clinical diagnosis and anatomical studies. Despite, the modern imaging modalities well established in developed countries across the globe, it is yet to remain in its infancy stage in veterinary practice in developing countries due to heavy initial investment and maintenance costs, lack of expert interpretation, a requirement of specialized technical staff and need of adjustable machines to accommodate the different range of animal sizes. Therefore, veterinarians should take advantage of these imaging techniques in designing future experiments by considering the availability of these varied imaging modalities and the creation of three-dimensional graphical representations of internal structures.

Feasibility study of 68Ga-labeled CAR T cells for in vivo tracking using micro-positron emission tomography imaging

Clinical tracking of chimeric antigen receptor (CAR) T cells in vivo by positron emission tomography (PET) imaging is an area of intense interest. But the long-lived positron emitter-labeled CAR T cells stay in the liver and spleen for days or even weeks. Thus, the excessive absorbed effective dose becomes a major biosafety issue leading it difficult for clinical translation. In this study we used ⁶⁸Ga, a commercially available short-lived positron emitter, to label CAR T cells for noninvasive cell tracking in vivo. CAR T cells could be tracked in vivo by ⁶⁸Ga-PET imaging for at least 6 h. We showed a significant correlation between the distribution of ⁸⁹Zr and ⁶⁸Ga-labeled CAR T cells in the same tissues (lungs, liver, and spleen). The distribution and homing behavior of CAR T cells at the early period is highly correlated with the long-term fate of CAR T cells in vivo. And the effective absorbed dose of ⁶⁸Ga-labeled CAR T cells is only one twenty-fourth of ⁸⁹Zr-labeled CAR T cells, which was safe for clinical translation. We conclude the feasibility of ⁶⁸Ga instead of ⁸⁹Zr directly labeling CAR T cells for noninvasive tracking of the cells in vivo at an early stage based on PET imaging. This method provides a potential solution to the emerging need for safe and practical PET tracer for cell tracking clinically.

Current Applications for Nuclear Medicine Imaging in Pulmonary Disease

Purpose of Review

The main goal of the article is to familiarize the reader with commonly and uncommonly used nuclear medicine procedures that can significantly contribute to improved patient care. The article presents examples of specific modality utilization in the chest including assessment of lung ventilation and perfusion, imaging options for broad range of infectious and inflammatory processes, and selected aspects of oncologic imaging. In addition, rapidly developing new techniques utilizing molecular imaging are discussed.

Recent Findings

The article describes nuclear medicine imaging modalities including gamma camera, SPECT, PET, and hybrid imaging (SPECT/CT, PET/CT, and PET/MR) in the context of established and emerging clinical applications. Areas of potential future development in nuclear medicine are discussed with emphasis on molecular imaging and implementation of new targeted tracers used in diagnostics and therapeutics (theranostics).

Summary

Nuclear medicine and molecular imaging provide many unique and novel options for the diagnosis and treatment of pulmonary diseases. This article reviews current applications for nuclear medicine and molecular imaging and selected future applications for radiopharmaceuticals and targeted molecular imaging techniques.

Relevance of immune cell and tumor microenvironment imaging in the new era of immunotherapy

Tumor-infiltrating immune cells play a key role against cancer. However, malignant cells are able to evade the immune response and establish a very complex balance in which different immune subtypes may drive tumor progression, metastatization and resistance to therapy. New immunotherapeutic approaches aim at restoring the natural balance and increase immune response against cancer by different mechanisms. The complexity of these interactions and the heterogeneity of immune cell subpopulations are a real challenge when trying to develop new immunotherapeutics and evaluate or predict their efficacy in vivo. To this purpose, molecular imaging can offer non-invasive diagnostic tools like radiopharmaceuticals, contrast agents or fluorescent dyes. These agents can be useful for preclinical and clinical purposes and can overcome [18F]FDG limitations in discriminating between true-progression and pseudo-progression. This review provides a comprehensive overview of immune cells involved in microenvironment, available immunotherapies and imaging agents to highlight the importance of new therapeutic biomarkers and their in vivo evaluation to improve the management of cancer patients.

Two decades of SPECT/CT - the coming of age of a technology: An updated review of literature evidence

PURPOSE

Single-photon emission computed tomography (SPECT) combined with computed tomography (CT) was introduced as a hybrid SPECT/CT imaging modality two decades ago. The main advantage of SPECT/CT is the increased specificity achieved through a more precise localization and characterization of functional findings. The improved diagnostic accuracy is also associated with greater diagnostic confidence and better inter-specialty communication.

METHODS

This review presents a critical assessment of the relevant literature published so far on the role of SPECT/CT in a variety of clinical conditions. It also includes an update on the established evidence demonstrating both the advantages and limitations of this modality.

CONCLUSIONS

For the majority of applications, SPECT/CT should be a routine imaging technique, fully integrated into the clinical decision-making process, including oncology, endocrinology, orthopaedics, paediatrics, and cardiology. Large-scale prospective studies are lacking, however, on the use of SPECT/CT in certain clinical domains such as neurology and lung disorders. The review also presents data on the complementary role of SPECT/CT with other imaging modalities and a comparative analysis, where available.

Advances in PET Detection of the Antitumor T Cell Response

Positron emission tomography (PET) is a powerful noninvasive imaging technique able to measure distinct biological processes in vivo by administration of a radiolabeled probe. Whole-body measurements track the probe accumulation providing a means to measure biological changes such as metabolism, cell location, or tumor burden. PET can also be applied to both preclinical and clinical studies providing three-dimensional information. For immunotherapies (in particular understanding T cell responses), PET can be utilized for spatial and longitudinal tracking of T lymphocytes. Although PET has been utilized clinically for over 30 years, the recent development of additional PET radiotracers have dramatically expanded the use of PET to detect endogenous or adoptively transferred T cells in vivo. Novel probes have identified changes in T cell quantity, location, and function. This has enabled investigators to track T cells outside of the circulation and in hematopoietic organs such as spleen, lymph nodes, and bone marrow, or within tumors. In this review, we cover advances in PET detection of the antitumor T cell response and areas of focus for future studies.

Biodistribution of adult derived human liver stem cells following intraportal infusion in a 17-year-old patient with glycogenosis type 1A

INTRODUCTION

Current treatment of inherited liver inborn errors of metabolism in children consists in appropriate diet and drugs and, for unstable patients, final orthotopic liver transplantation. Unfortunately, liver transplantation remains not easily available because of organ shortage and imposes inherent risks and lifelong immunosuppressive therapy. Therefore alternative treatments are required. Hepatocytes transplantation and its limitations led to consider innovative alternative such as transplantation of adult derived human liver stem cells (ADLHSC). These cells present high proliferative capacity, good resistance to cryopreservation and ability to differentiate into hepatocyte-like cells displaying mature hepatocyte functions.

AIM

Biodistribution of ADHLSC had never been assessed after infusion through the portal vein in patients. This information is required to determine the safety of the method.

METHODS

ADHLSC were efficiently labelled with 111-Indium DTPA radiotracer and SPECT imaging was used for the acquisition of whole body imaging to document short term biodistribution of ADHLSC.

RESULTS

Following infusion through the portal vein, ADHLSC diffused homogenously throughout the liver and remained strictly within the targeted organ. Images were acquired until 5 days after infusion. At that time, no signal was observed in any other organs except the liver. Urinary excretion of 111-Indium DTPA was also monitored.

CONCLUSION

For the first time, we documented the short term biodistribution of ADHLSC within the liver after infusion through the portal vein.

[SPECT/CT diagnostics for skeletal infections]

CLINICAL/METHODICAL ISSUE

Skeletal infections are often a diagnostic and clinical challenge.

STANDARD RADIOLOGICAL METHODS

Nuclear imaging modalities used in the diagnostic workup of acute and chronic skeletal infections include three-phase bone scintigraphy and scintigraphy with labelled leucocytes.

METHODICAL INNOVATIONS

The introduction of hybrid technologies, such as single photon emission computed tomography/computed tomography (SPECT/CT) has dramatically changed nuclear medical imaging of infections.

PERFORMANCE

In general SPECT/CT leads to a considerably more accurate diagnosis than planar or SPECT imaging.

ACHIEVEMENTS

Given the integrated acquisition of metabolic, functional and morphological information, SPECT/CT has increased in particular the specificity of three-phase skeletal scanning and scintigraphy with labeled leucocytes.

Tc-99m Labeled HMPAO white Blood Cell Scintigraphy in Pediatric Patients

OBJECTIVE

(99m)Tc labeled hexamethylpropylene amine oxime (HMPAO) white blood cell (WBC) scintigraphy is a frequently used option for acute infection, particularly in pediatric patients. This scintigraphy is applied to detect sites of infection/inflammation in patients with fever of unknown origin, to find and follow up osteomyelitis, and to detect suspicion of acute appendicitis. The aim of this retrospective study was to evaluate the value of (99m)Tc-HMPAO labeled WBC scintigraphy in pediatric patients.

MATERIAL AND METHODS

The study was conducted between January 2006 and December 2008 and included 13 patients (5 boys, 8 girls; mean age 6.9±6.2 years). Those patients who had suspicion of bone infection (n=7), fever of unknown origin (n=3), and suspicion of acute appendicitis (n=3) were evaluated retrospectively. (99m)Tc-HMPAO labeled WBC scintigraphy imaging was performed to all patients. Diagnosis was done according to operation and pathological results or clinical follow-up.

RESULTS

(99m)Tc-HMPAO labeled WBC scintigraphy has been found to be true positive in 6 cases, true negative in 6 cases, and false negative in one patient who had fewer unknown origin. The false negative case has been found to have encephalitis with MRI.

CONCLUSION

Leukocyte scintigraphy has been described as a useful diagnostic tool in the diagnosis of suspicion of bone infection, fever of unknown origin and suspicion of acute appendicitis. (99m)Tc-HMPAO labeled WBC scintigraphy is a rapid and very accurate method for detecting those pathologies. Our results showed that WBC scintigraphy might be reliably used for diagnosis of suspected bone infection and acute appendicitis, fever of unknown origin, and acute appendicitis, in pediatric patient population.

CONFLICT OF INTEREST

None declared.