Search Results (61)

Several animal models of Alzheimer’s disease have been developed and tested for diagnostic and treatment purposes. [¹¹C]PIB is the gold-standard radiotracer for the detection of Aβ plaque deposits, a hallmark of the disease. This study aimed to evaluate the in vivo detection of Aβ plaques using [¹¹C]PIB microPET imaging across different animal models of Alzheimer’s disease. The study included 3xTg-AD transgenic mice, TgF344-AD transgenic rats and Aβ injection-based rat model. The results showed an age-related increase in [¹¹C]PIB uptake in 3xTg-AD mice, particularly in the midbrain and thalamus. In TgF344-AD rats, differences were also observed compared to WT controls, with the highest values observed in the hippocampus and cortex. In the injection-based model, inoculated rats showed greater uptake in the injection site than SHAM animals. Across all microPET studies, [¹¹C]PIB uptake was consistently higher in females than in their male counterparts. These findings support the value of transgenic and Aβ injection-based models in preclinical research on Aβ plaque deposition and highlight the importance of considering species, model type, sex, and age in experimental design. Full article

Background and Objectives: This study was designed to evaluate the potential cardioprotective effect of Exenatide against doxorubicin (DOX)-induced myocardial injury in rats by assessing scintigraphic alterations together with oxidative stress and inflammation. Materials and Methods: This study included 28 adult male Wistar albino rats that were randomized to 4 groups (n = 7): control, Exenatide alone, DOX (receiving DOX (18 mg/kg, i.p) on days 5–7; Exenatide + DOX (treated with Exenatide together with the DOX). On day 8, ECG, 99mTc-PYP scintigraphy, and biochemical parameters were evaluated. Results: DOX caused ECG abnormalities—bradycardia, significant QT prolongation, and elevated ST-segment amplitude—along with increased myocardial PYP uptake. Exenatide + DOX group significantly improved ECG changes. Biochemically, DOX markedly increased cardiac injury biomarkers (cTnT, CK, CK-MB), hepatic and renal injury markers (ALT, AST, LDH, BUN, creatinine), SIRT-1 level, inflammatory marker (NF-κB, TNF-α, IL-6, NO) and oxidative stress indicators (MDA, TOS), while decreasing antioxidant defenses (GSH, TAS, Nrf2). Exenatide co-treatment significantly attenuated all DOX-induced changes. Conclusions: Exenatide markedly attenuates DOX-induced cardiotoxicity by improving electrical conduction, reducing myocardial radiotracer uptake, and restoring oxidative–inflammatory balance through partial recovery of the SIRT-1/Nrf2/NF-κB pathway. Full article

Background/Objectives: Fibroblast activation protein (FAP), which is abundantly expressed in cancer-associated fibroblasts (CAFs) across various epithelial malignancies, has emerged as a promising target for molecular imaging and radionuclide therapy. Although several reviews have addressed FAP-targeted diagnostics, a comprehensive synthesis integrating molecular biology, diagnostic performance, and early therapeutic development remains limited. This review summarises the current evidence on radionuclide-labelled FAP inhibitors (FAPIs), with particular emphasis on their diagnostic utility, emerging therapeutic applications, and the structural features that shape their biological behaviour. Methods: A structured literature search was conducted across PubMed, Scopus, and Web of Science, focusing on FAPI-based imaging and therapy. Results: Diagnostic studies consistently demonstrate high tumour-to-background contrast for [⁶⁸Ga]Ga and [¹⁸F]-labelled FAPI radiotracers, particularly in tumours with prominent stromal components such as pancreatic, colorectal, breast, and head and neck cancers. FAPI PET/CT often surpasses [¹⁸F]FDG in lesion conspicuity in the brain, liver, and peritoneum. Therapeutic evidence shows encouraging tumour retention and safety profiles for agents such as [¹⁷⁷Lu]Lu-FAP-2286 and [⁹⁰Y]Y-FAPI-46, while α-emitting radiotracers (e.g., [²²⁵Ac]Ac-FAPI-04) demonstrate potent antitumor effects in preclinical models. Conclusions: Radiolabelled FAPI radiotracers hold significant potential as dual diagnostic and therapeutic agents, particularly for desmoplastic tumours with high CAF content. Nonetheless, clinical evidence remains in its early stages, and substantial questions persist regarding dosimetry, intertumoral variability in FAP expression, and optimal ligand selection for therapy. Continued development of next-generation FAPI constructs, along with well-designed prospective trials, will be crucial in defining the future role of FAPI-based theranostics in oncology. Full article

Glomerular filtration rate (GFR) is a key indicator of renal function. Traditional methods for GFR measurement have limitations including invasiveness, low spatial resolution, and lengthy protocols. Positron emission tomography (PET) radiotracers have emerged as promising tools for non-invasive, accurate, and dynamic renal function assessment. Objectives: This systematic literature review evaluates the clinical utility, and current evidence surrounding PET radiotracers used for GFR measurement in humans, emphasizing advances over conventional renal imaging modalities. Methods: A systematic literature search was conducted in PubMed, Web of Science, and Scopus, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, from database inception to November 2024. The search identified studies evaluating PET-based measurement of glomerular filtration rate (GFR) and renal perfusion. Inclusion criteria encompassed human studies using PET radiotracers (e.g., ⁶⁸Ga, ¹⁸F) with comparisons to reference standards (estimated GFR or serum creatinine). Two authors independently screened titles/abstracts, extracted data, and assessed bias using Quality Assessment of Diagnostic Accuracy Studies tool (QUADAS-2). Exclusions included animal studies, reviews, and non-English articles. Results: Eleven studies met inclusion criteria, with ⁶⁸Ga-EDTA showing the highest validation against reference standards such as ⁵¹Cr-EDTA plasma clearance, demonstrating strong correlation. PET imaging offered superior spatial–temporal resolution, enabling accurate split renal function assessment and quantitative analysis of both filtration and perfusion. ⁶⁸Ga-somatostatin analogues exhibited moderate correlations between renal SUV and estimated GFR, with post-PRRT uptake changes indicating early nephrotoxicity. Among novel tracers, ⁶⁸Ga-FAPI showed a strong inverse SUV–GFR relationship, reflecting renal fibrosis and suggesting potential as a chronic kidney disease (CKD) biomarker but requires further clinical validation. Limitations across studies include small sample sizes, retrospective designs, and variability in reference standards. Conclusions: PET radiotracers, particularly ⁶⁸Ga-EDTA, represent a significant advancement for non-invasive, quantitative GFR measurement with improved precision and renal anatomical detail compared to traditional methods. Future prospective, large-scale human studies with standardized protocols are needed to establish these PET tracers as routine clinical tools in nephrology. Integration of hybrid PET/MRI and novel tracer development may further enhance renal diagnostic capabilities. Full article

Background: Meta-analyses on the prevalence and clinical significance of breast incidental uptake (BIU) at PET/CT are available only for [¹⁸F]FDG, showing that BIU is rare but malignant in a substantial proportion of cases. This study aimed to update the pooled prevalence and malignancy risk of BIU using different PET radiotracers, expanding [¹⁸F]FDG-based evidence. Methods: A comprehensive literature search of studies on BIU was carried out in two bibliographic databases, and the literature was screened up to 25 May 2025. Only original articles reporting BIU were selected. A proportion meta-analysis was conducted on a patient-based analysis using a random-effects model to estimate pooled prevalence, malignancy rate, and histological distribution. Results: In total, 29 studies were included in the systematic review and meta-analysis. PET/CT was performed using [¹⁸F]FDG (n = 25), radiolabeled somatostatin analogues (SSAs) (n = 3), or [¹⁸F]fluorocholine (n = 1). The pooled prevalence of BIU was 0.5% for [¹⁸F]FDG PET/CT, 3.4% for SSA PET/CT, and 2.6% for [¹⁸F]fluorocholine. The pooled malignancy rate among BIUs (female patients) was 33.5% for [¹⁸F]FDG, 86.4% for SSA, and 70% for [¹⁸F]fluorocholine PET/CT. Histological data were mainly available for [¹⁸F]FDG PET/CT, showing ductal carcinoma as the most frequent malignant histotype (pooled value 42.2%) and fibroadenoma (pooled value 14.8%) as the most frequent benign histotype. Conclusions: Similar to the case for [¹⁸F]FDG, BIU using other PET radiopharmaceuticals is uncommon but often malignant. Therefore, BIU should prompt dedicated breast imaging and, when indicated, histopathological confirmation. Further well-designed studies are needed to clarify the clinical impact of BIU detection and the prevalence and clinical significance of BIU using tracers other than [¹⁸F]FDG. Full article

Background/Objective: Acute and chronic pain affect millions of individuals, yet there are currently no molecular imaging tools to directly assess pain-related mechanisms in the central nervous system (CNS). The voltage-gated sodium channel Na_V1.8 plays a pivotal role in neuropathic pain by increasing the excitability of nociceptive neurons following nerve injury or inflammation. In this work, we aimed to develop a novel positron emission tomography (PET) imaging probe for Na_V1.8 to facilitate noninvasive quantification of this target in the CNS and thereby advance our understanding of pain neurobiology. Methods: We selected the compound suzetrigine, a U.S. FDA-approved, highly selective non-opioid Na_V1.8 inhibitor, as the first candidate for a Na_V1.8-targeted PET tracer. The compound was first assessed using in silico docking and CNS multiparameter optimization (MPO) analysis to evaluate target binding and predicted brain penetrability. Radiolabeling was accomplished by O-methylation with [¹¹C]methyl iodide to yield [¹¹C]suzetrigine without structural modification. The tracer was then evaluated using in vitro binding assays, including autoradiography and saturation binding on rat brain tissues, to determine binding parameters (K_D, B_max), and using in vivo PET imaging in rats to assess brain uptake, time–activity curves (TACs), and tracer behavior under baseline and pretreatment conditions. Pretreatment was performed with unlabeled suzetrigine, the P-glycoprotein (P-gp) inhibitor verapamil, and the heterologous Na_V1.8 inhibitor A-803467. Results: In silico docking demonstrated favorable binding of suzetrigine to the Na_V1.8 active site, and the calculated CNS MPO score (>3.5) suggested adequate brain penetration. Radiochemical synthesis of [¹¹C]suzetrigine via O-methylation yielded a high decay-corrected radiochemical yield (19.2 ± 2.7%, n = 3), excellent purity (>98%, n = 3), and moderate molar activity (62.9 ± 51.8 MBq/nmol, n = 3). Autoradiography on rat brain tissue confirmed saturable and selective binding of [¹¹C]suzetrigine to Na_V1.8. Saturation binding assays revealed a B_max = 93 fmol/mg and a K_D = 0.1 nM, supporting the imageability of Na_V1.8 in the brain using this tracer. In vivo PET imaging in rats demonstrated rapid and sufficient brain uptake but revealed unexpected tracer behavior: signal intensity markedly increased following pretreatment with either unlabeled suzetrigine or the P-gp inhibitor verapamil, and showed a slight increase after pretreatment with the heterologous Na_V1.8 inhibitor A-803467. Detailed analysis of PET images, TACs, and normalized area-under-curve (AUC) values indicated that these atypical uptake patterns were primarily attributable to P-gp-mediated effects, although additional factors may also contribute. Conclusions: [¹¹C]Suzetrigine exhibits high affinity, good brain uptake, and selective target engagement in vitro, supporting its potential as a first-in-class Na_V1.8-PET tracer. However, in vivo performance is confounded by P-gp-mediated efflux and possibly other mechanisms that limit accurate quantification of Na_V1.8 in the living brain. These findings underscore the critical role of efflux transporters in CNS radiotracer development and highlight the need for design strategies that mitigate P-gp interaction when targeting ion channels in the brain. Future studies will include imaging under constant P-gp inhibition, arterial blood sampling for radiometabolite analysis and full kinetic modeling, and evaluation in non-human primates to assess translational feasibility. Full article

Background/Objectives: Biology-guided radiotherapy (BgRT) is a novel technology utilizing PET radiotracer emissions to deliver image-guided adaptive RT. 18F-Fluorodeoxyglucose ([¹⁸F]FDG) is the most common PET radiotracer but has background in the liver and brain because it is taken up by viable tumor cells as well as inflammatory cells. Fibroblast activation protein (FAP) is overexpressed in cancer-associated fibroblasts with minimal expression in normal tissues. FAP inhibitors (FAPIs) bind to FAP, and a FAPI labeled with Gallium-68 (68Ga) is a novel radiotracer with high tumor selectivity. Multiple studies have compared [⁶⁸Ga]Ga-FAPI-04 vs. [¹⁸F]FDG for diagnostic imaging, but [⁶⁸Ga]Ga-FAPI-04 vs. [¹⁸F]FDG have never been compared in terms of their utility for BgRT. Purpose: This study was designed to assess the utility of [⁶⁸Ga]Ga-FAPI-04 vs. [¹⁸F]FDG for BgRT used to treat pancreatic, liver, lung, head and neck, and cervical cancers. Methods: A radiation oncologist specializing in each cancer contoured the gross tumor volume (GTV) on [¹⁸F]FDG PET-CT and [⁶⁸Ga]Ga-FAPI-04 PET-CT images. Auto-contours were generated using an auto-threshold of 40% of the maximum Standardized Uptake Value (SUV). The suitability of [⁶⁸Ga]Ga-FAPI-04 vs. [¹⁸F]FDG for BgRT was evaluated by comparing Normalized Net Activity Concentration (NNA) and Normalized Target Signal (NTS) for each cancer. Results: NNA and NTS for [⁶⁸Ga]Ga-FAPI-04 and [¹⁸F]FDG met the requirements for [¹⁸F]FDG-guided BgRT (NNA > 5.0 kBq/mL, NTS > 2.7) for all disease sites. NNAFAPI was significantly greater than NNAFDG for pancreatic, H&N, and cervical cancer. NTSFAPI was significantly greater than NTSFDG for pancreatic, liver, and lung cancer. Conclusions: [⁶⁸Ga]Ga-FAPI-04 is a novel radiotracer for BgRT and has the greatest potential impact in the treatment of pancreatic cancer. Full article

Radionuclide molecular imaging of epidermal growth factor receptor (EGFR) expression might permit the selection of patients for EGFR-targeting therapies. Designed ankyrin repeat protein (DARPin) E01 with a high affinity to the ectodomain III of the EGFR is a possible EGFR imaging probe. The goal of this study was to evaluate the potential of radiolabeled DARPin E01 for in vivo imaging of EGFR. DARPin E01 containing the (HE)₃-tag was site-specifically labeled with a residualizing ^99mTc (using ^99mTc]Tc(CO)₃). Two methods providing non-residualizing ¹²³I labels, direct electrophilic radioiodination and indirect radioiodination using [¹²³I]I-para-iodobenzoate (PIB), were tested. [^99mTc]Tc-(HE)₃-E01 and [¹²³I]I-(HE)₃-E01-PIB preserved specific binding to EGFR-expressing cells and affinity in the single-digit nanomolar range. Direct labeling with ¹²³I resulted in a substantial loss of binding. In vitro cellular processing studies showed that both [^99mTc]Tc-(HE)₃-E01 and [¹²³I]I-(HE)₃-E01-PIB had rapid binding and relatively slow internalization. Evaluation of [^99mTc]Tc-(HE)₃-E01 biodistribution in normal CD1 mice showed that its hepatic uptake was non-saturable, suggesting that this tracer does not bind to murine EGFR. A side-by-side comparison of biodistribution and tumor targeting of [^99mTc]Tc-(HE)₃-E01 and [¹²³I]I-(HE)₃-E01-PIB was performed in Nu/j mice bearing EGFR-positive A-431 and EGFR-negative Ramos human cancer xenografts. Both radiolabeled DARPins demonstrated EGFR-specific tumor uptake. However, [¹²³I]I-(HE)₃-E01-PIB had appreciably lower uptake in normal organs compared to [^99mTc]Tc-(HE)₃-E01, which provided significantly (p < 0.05) higher tumor-to-organ ratios. Gamma-camera imaging confirmed that [¹²³I]I-(HE)₃-E01-PIB demonstrated a higher imaging contrast in preclinical models than [^99mTc]Tc-(HE)₃-E01. In conclusion, DARPin (HE)₃-E01 labeled using a non-residualizing [¹²³I]I-para-iodobenzoate (PIB) label is the preferred radiotracer for in vivo imaging of EGFR expression in cancer. Full article

Background: B7-H3, an immunoregulatory protein of the B7 family, has been associated with both anti-cancer immunity and tumor promotion, with its expression commonly correlated with poor prognosis. Although it is frequently expressed across cancers, its heterogeneity may limit the effectiveness of B7-H3-targeted therapies. Consequently, a sensitive and non-invasive method is needed to assess B7-H3 expression for patient selection and stratification. Single-domain antibody fragments (sdAbs) offer a promising platform for developing such a diagnostic tool. Methods: To generate B7-H3 sdAbs, two Ilamas were immunized with the recombinant human B7-H3 protein. Positive clones were selected through Phage biopanning and characterized for thermal stability, binding specificity, and affinity to human and murine B7-H3 proteins. Selected sdAbs were radiolabeled with Technetium-99m (^99mTc) and evaluated for B7-H3 detection in two xenograft tumor models using micro-SPECT/CT imaging and dissection studies. Results: Sixteen purified sdAbs bound specifically to recombinant B7-H3 proteins and cells expressing native B7-H3 antigens, with nanomolar affinities. The four best-performing sdAbs bound promiscuously to tested mouse and human B7-H3 isoforms. Lead sdAb C51 labeled with ^99mTc displayed specific accumulation across two human B7-H3⁺ tumor models, achieving high contrast with a tumor-to-blood ratio of up to 10 ± 3.16, and a tumor uptake of up to 4.96 ± 1.4%IA/g at 1.5 h post injection. Conclusions: The lead sdAb enabled rapid, specific, and non-invasive imaging of human B7-H3⁺ tumors. Its isoform promiscuity supports broad applicability across cancers expressing different human B7-H3 isoforms. These results support further development for clinical translation to enable patient selection and improved B7-H3-targeted therapies. Full article

P-Glycoprotein (P-gp, also known as MDR1 or ABCB1) is an ATP-binding cassette (ABC) transporter that actively effluxes a wide range of structurally and functionally diverse molecules, playing a crucial role in drug absorption, distribution, and excretion. P-gp is highly expressed at key biological barriers, such as the blood–brain barrier (BBB), intestine, liver, and kidneys, and it serves as a gatekeeper against xenobiotics and therapeutics. Its dysregulation is involved in multidrug resistance (MDR), epilepsy, cancer, infectious diseases, and neurodegenerative disorders. Several small molecules were synthesized using SAfIR and SAR, and, among them, [¹⁸F]MC225 showed the most promising results for in vivo human studies, with appropriate pharmacodynamics and pharmacokinetics profiles for in vivo use. [¹⁸F]MC225 is currently being employed in PHASE II human trials at the UMC Groningen, the Netherlands, in patients diagnosed with AD, PD and MCI, as well as PHASE II human trials at the Policlinico Gemelli in Rome Italy to diagnose P-gp resistant depression. Preliminary studies show that [¹⁸F]MC225 radiotracer is behaving according to the initial predictions, that is, it accurately diagnoses the aforementioned pathologies, more so than previously developed small molecules for the same goal. Full article

Parkinson’s disease (PD) is a neurodegenerative disorder marked by the progressive loss of dopaminergic neurons in the nigrostriatal pathway. The dopamine active transporter (DAT), a key protein involved in dopamine reuptake, serves as a selective biomarker for dopaminergic terminals in the striatum. DAT binding has been extensively studied using in vivo imaging techniques such as Single-Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET). To support the design of new radiotracers targeting DAT, we employ Quantitative Structure–Activity Relationship (QSAR) analysis on a structurally diverse dataset composed of 57 compounds with known affinity constants for DAT. The best-performing QSAR model includes four molecular descriptors and demonstrates robust statistical performance: R² = 0.7554, Q²_LOO = 0.6800, and external R² = 0.7090. These values indicate strong predictive capability and model stability. The predicted compounds are evaluated using a docking methodology to check the correct coupling and interactions with the DAT. The proposed approach—combining QSAR modeling and docking—offers a valuable strategy for screening and optimizing potential PET/SPECT radiotracers, ultimately aiding in the neuroimaging and early diagnosis of Parkinson’s disease. Full article

Objective: Traditional imaging modalities for the planning of Gamma Knife radiosurgery (GKRS) are non-specific and do not accurately delineate intracranial neoplasms. This study aimed to evaluate the utility of positron emission tomography (PET) for the planning of GKRS for intracranial neoplasms (ICNs) and the post-GKRS applications of PET for patient care. Methods: PubMed, Scopus, and ScienceDirect were searched in order to assemble relevant studies regarding the uses of PET in conjunction with GKRS for ICN treatment. PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines were followed to identify relevant studies on the use of PET in conjunction with GKRS. Particular emphasis was placed on review articles and medical research investigating tumor delineation and post-operative care. Relevant studies were selected and assessed based on quality measures, including study design, sample size, and significance. Inclusion and exclusion criteria were used to examine the yield of the initial search (n = 105). After a secondary review, the included results were identified (n = 50). Results: This study revealed that PET imaging is highly accurate for the planning of GKRS. In fact, many cases indicate that it is more specific than traditional imaging modalities. PET is also capable of complementing traditional imaging techniques through combination imaging. This showed significant efficacy for the planning of GKRS for ICNs. Conclusions: While PET shows a multitude of applications for the treatment of ICNs with GKRS, further research is necessary to assemble a complete set of clinical guidelines for treatment specifications. Importantly, future studies need a greater standardization of methods and expanded trials with a multitude of radiotracers. Full article

Objectives: Prostate-specific membrane antigen (PSMA)-targeted radioligands are promising diagnostic tools for the targeted positron emission tomography (PET) imaging of prostate cancer (PCa). In present work, we aimed to develop a novel PSMA tracer to provide an additional option for prostate cancer diagnosis. Methods: Our team designed a new structure of the PSMA tracer and evaluated it with cellular experiments in vitro to preliminarily verify the targeting and specificity of ⁶⁸Ga-NOTA-GC-PSMA. PET/CT imaging of PSMA-positive xenograft-bearing models in vivo to further validate the in vivo specificity and targeting of the radiotracer. Pathological tissue sections from prostate cancer patients were compared with pathological immunohistochemistry and pathological tissue staining results by radioautography experiments to assess the targeting-PSMA of ⁶⁸Ga-NOTA-GC-PSMA on human prostate cancer pathological tissues. Results: The novel tracer showed high hydrophilicity and rapid clearance rate. Specific cell binding and micro-PET imaging experiments showed that ⁶⁸Ga-NOTA-GC-PSMA displayed a high specific LNCaP tumor cell uptake (1.70% ± 0.13% at 120 min) and tumor-to-muscle (T/M) and tumor-to-kidney (T/K) ratio (13.87 ± 11.20 and 0.20 ± 0.08 at 60 min, respectively). Conclusions: The novel tracer ⁶⁸Ga-NOTA-GC-PSMA is promising radionuclide imaging of PCa. Full article

Background: Cancer-associated fibroblasts (CAFs) are key contributors to the tumorigenic process, with fibroblast activation protein (FAP) overexpressed on CAFs in numerous epithelial carcinomas. FAP represents a promising target for tumor imaging and therapy. We aimed to develop a novel [¹⁸F]AlF-H₃RESCA-FAPI radiotracer with a high labeling yield at room temperature for positron emission tomography (PET) imaging of FAP-expressing tumors. Methods: The H₃RESCA-FAPI chelator was synthesized and radiolabeled with [¹⁸F]AlF. Its radiotracer binding affinity to FAP was assessed using surface plasmon resonance (SPR). Its in vitro stability, plasma clearance, and biodistribution were evaluated. PET imaging was performed in U87MG tumor-bearing mice, with a blocking study to assess tracer specificity. Results: The [¹⁸F]AlF-H₃RESCA-FAPI radiotracer demonstrated a high binding affinity to FAP (K_D < 10.09 pM) and favorable radiochemical yields (92.4 ± 2.4%) with >95% radiochemical purity. In vitro and in vivo studies showed good stability and rapid clearance from non-target tissues. PET imaging revealed specific tumor uptake, which was significantly reduced by co-injection with unlabeled DOTA-FAPI-04. Conclusions: [¹⁸F]AlF-H₃RESCA-FAPI is a promising radiotracer for PET imaging of FAP-expressing tumors. Further optimization of its pharmacokinetics could make it a potential candidate for clinical translation. Full article

The tumor microenvironment (TME) is a dynamic and complex medium that plays a central role in cancer progression, metastasis, and treatment resistance. Among the key elements of the TME, cancer-associated fibroblasts (CAFs) are particularly important for their ability to remodel the extracellular matrix, promote angiogenesis, and suppress anti-tumor immune responses. Fibroblast activation protein (FAP), predominantly expressed by CAFs, has emerged as a promising target in both cancer diagnostics and therapeutics. In nuclear medicine, targeting FAP offers new opportunities for non-invasive imaging using radiolabeled fibroblast activation protein inhibitors (FAPIs). These FAP-specific radiotracers have demonstrated excellent tumor detection properties compared to traditional radiopharmaceuticals such as [¹⁸F]FDG, especially in cancers with low metabolic activity, like liver and biliary tract tumors. The most recent FAPI derivatives not only enhance the accuracy of positron emission tomography (PET) imaging but also hold potential for theranostic applications by delivering targeted radionuclide therapies. This review examines the biological underpinnings of FAP in the TME, the design of FAPI-based imaging agents, and their evolving role in cancer diagnostics, highlighting the potential of FAP as a target for precision oncology. Full article