Recent applications of a single quadrupole mass spectrometer in 11C, 18F and radiometal chemistry

Unlocking the Hidden Depths: Multi-Modal Integration of Imaging Mass Spectrometry-Based and Molecular Imaging Techniques

Multimodal imaging (MMI) has emerged as a powerful tool in clinical research, combining different imaging modes to acquire comprehensive information and enabling scientists and surgeons to study tissue identification, localization, metabolic activity, and molecular discovery, thus aiding in disease progression analysis. While multimodal instruments are gaining popularity, challenges such as non-standardized characteristics, custom software, inadequate commercial support, and integration issues with other instruments need to be addressed. The field of multimodal imaging or multiplexed imaging allows for simultaneous signal reproduction from multiple imaging strategies. Intraoperatively, MMI can be integrated into frameless stereotactic surgery. Recent developments in medical imaging modalities such as magnetic resonance imaging (MRI), and Positron Emission Topography (PET) have brought new perspectives to multimodal imaging, enabling early cancer detection, molecular tracking, and real-time progression monitoring. Despite the evidence supporting the role of MMI in surgical decision-making, there is a need for comprehensive studies to validate and perform integration at the intersection of multiple imaging technologies. They were integrating mass spectrometry-based technologies (e.g., imaging mass spectrometry (IMS), imaging mass cytometry (IMC), and Ion mobility mass spectrometry ((IM-IM) with medical imaging modalities, offering promising avenues for molecular discovery and clinical applications. This review emphasizes the potential of multi-omics approaches in tissue mapping using MMI integrated into desorption electrospray ionization (DESI) and matrix-assisted laser desorption ionization (MALDI), allowing for sequential analyses of the same section. By addressing existing knowledge gaps, this review encourages future research endeavors toward multi-omics approaches, providing a roadmap for future research and enhancing the value of MMI in molecular pathology for diagnosis.

Development and Validation of a PET/SPECT Radiopharmaceutical in Oncology

In oncology, biomarker research aimed to provide insights on cancer biology via positron emission tomography (PET) and single photon emission tomography (SPECT) imaging has seen an incredible growth in the past two decades. Despite the increased number of publications on PET/SPECT radiopharmaceuticals, the field lacked standardization of in vitro and in vivo parameters necessary for the characterization of any radiotracer. Through the efforts of the World Molecular Imaging Society Education Committee, this white paper lays down validation studies that are essential to chemically and biologically characterize new radiopharmaceuticals derived from small molecules, peptides or proteins. Finally, a brief overview of the steps toward translation is also presented.Herein, we discuss the following: Chemistry and radiochemistry metrics to establish the identity of the imaging agent. In vitro and in vivo studies to examine the radiotracer's mechanism of action, which includes target specificity, pharmacokinetics and in vivo metabolism.

Rapid screening of nine unradiolabeled candidate compounds as PET brain imaging agents using cassette-wave microdosing and LC-MS/MS

The R&D of PET imaging agents is a complex system engineering, simplifying screening steps and increasing screening efficiency have become popular issues. The purpose of this study is to develop a new screening procedure using cassette-wave microdosing and LC-MS/MS to enhance the screening throughput of unradiolabeled candidate compounds as PET imaging agents. Nine compounds were divided into 3 sets and made into 3 cassettes. Fifteen rats were randomly divided into 3 groups, and every animal received three intravenous bolus injections at three different time points; the doses were at microdose levels. This dosing approach takes advantage of temporal and spatial differences and is likened to an input wave; therefore, this approach was named cassette-wave microdosing. The samples of different brain regions such as the hypothalamus, striatum, hippocampus, cortex, cerebellum and the remainder of the brain were detected by LC-MS/MS analysis. The research potential of the compounds as PET imaging agents is evaluated in terms of brain biodistribution data. The screening method is rapid, highly efficient, reliable and reduces animal usage. Additionally, it can shorten the evaluation process of radiopharmaceuticals and enhance the screening throughput of PET radiopharmaceuticals without the use of radioactive agents.

Fluorine-18 Labeled Fluorofuranylnorprogesterone ([18F]FFNP) and Dihydrotestosterone ([18F]FDHT) Prepared by "Fluorination on Sep-Pak" Method

To further explore the scope of our recently developed “fluorination on Sep-Pak” method, we prepared two well-known positron emission tomography (PET) tracers 21-[¹⁸F]fluoro-16α,17α-[(R)-(1′-α-furylmethylidene)dioxy]-19-norpregn-4-ene-3,20-dione furanyl norprogesterone ([¹⁸F]FFNP) and 16β-[¹⁸F]fluoro-5α-dihydrotestosterone ([¹⁸F]FDHT). Following the “fluorination on Sep-Pak” method, over 70% elution efficiency was observed with 3 mg of triflate precursor of [¹⁸F]FFNP. The overall yield of [¹⁸F]FFNP was 64–72% (decay corrected) in 40 min synthesis time with a molar activity of 37–81 GBq/µmol (1000–2200 Ci/mmol). Slightly lower elution efficiency (~55%) was observed with the triflate precursor of [¹⁸F]FDHT. Fluorine-18 labeling, reduction, and deprotection to prepare [¹⁸F]FDHT were performed on Sep-Pak cartridges (PS-HCO₃ and Sep-Pak plus C-18). The overall yield of [¹⁸F]FDHT was 25–32% (decay corrected) in 70 min. The molar activity determined by using mass spectrometry was 63–148 GBq/µmol (1700–4000 Ci/mmol). Applying this quantitative measure of molar activity to in vitro assays [¹⁸F]FDHT exhibited high-affinity binding to androgen receptors (K_d~2.5 nM) providing biological validation of this method.