Seminars in nuclear medicine最新文献

Conventional tracers for renography are Tc-99m-MAG3 (mercaptoacetyltriglycine) and Tc-99m-DTPA (diethyltriaminepentaacetic acid). Others are Tc-99m-sestamibi, Ga-68-EDTA (ethylenediaminetetraacetic acid) and FDG (F-18-fluorodeoxyglucose), the last mentioned because it is not recognised by tubular sodium glucose cotransporter 2 and therefore enters urine. Renography is routinely performed under furosemide challenge, administered 15 min before, at the same time as or 20 min after tracer administration. The renogram comprises 3 phases: perfusion, rising and declining phases. Perfusion phase is important for renal transplants but, in general, not for native kidneys. Measurement of renal perfusion is a separate issue. Split function is measured from the relative gradients of the second phases but optimally from Patlak-Rutland graphical analysis. The third phase - whether present or not - informs on urinary drainage from hydronephrotic kidneys with suspected outflow tract obstruction. Features of obstruction are prolonged parenchymal transit time (PTT), progressively rising renogram and impaired function. PTT is prolonged in obstruction because of increased intratubular pressure and increased fluid reabsorption. It is measured by deconvolution analysis using a region over the left ventricle for blood pool. Judgement by eye is, however, preferable, especially if the contralateral kidney is normal for comparison. Another cause of prolonged PTT is tubular injury which allows increased water and solute reabsorption from tubular lumen. Symmetrical rising renograms are typically seen. Tc-99m-MAG3 secretion into tubular lumen is mediated by multidrug resistance (MDR) transporters so the renogram is exposed to the effects of MDR inhibitors such as chemotherapeutics. Ga-68-has great potential as renographic agent, especially in renal transplant management.

Background/aim: Fibroblast activation protein inhibitor (FAPI) PET has shown promising diagnostic performance across various cancers. However, uptake in nonmalignant conditions has also been reported, as highlighted in the authors' previous systematic review from 2022. This updated systematic review summarizes the accumulated evidence on nonmalignant FAPI PET findings, both pitfalls in cancer diagnostic and emerging novel FAPI PET scan indications.

Materials and methods: A systematic search of PubMed, Embase, and Web of Science was conducted on May 2, 2025. Peer-reviewed English-language studies involving human subjects and using FAPI tracers, specifically targeting FAP, were included. Studies published between April 2022 and May 2025 reporting nonmalignant FAPI PET/CT findings were added to those from the previous 2022 review. Findings were analyzed on a per-lesion basis and grouped by anatomical region.

Results: In total, 380 studies reporting 8,230 nonmalignant FAPI PET findings were included. Most studies originated from China (70%), and 63% were case reports or case series. Although 69% of subjects were scanned due to "cancer", a clear increase in nonmalignant scan indications was observed. The search identified common pitfalls for cancer diagnostics, including FAPI uptake in infectious and inflammatory diseases, fibrosis, and benign neoplasms, but also emerging nonmalignant FAPI PET indications, including interstitial lung disease, cardiac conditions, and arthritis.

Conclusion: This review provides, to the best of our knowledge, the most comprehensive summary of nonmalignant FAPI PET findings to date. It may serve as a valuable reference for researchers and clinicians interpreting FAPI PET.

The contemporary scope of nuclear nephrology extends from non-imaging techniques for glomerular filtration rate calculation through dynamic renal scintigraphy and cortical imaging with planar or single photon emission computed tomography (SPECT) approaches to emerging applications in positron emission tomography (PET) renography and theranostics-based renal toxicity risk assessment. Artificial intelligence (AI) shares a long history with nuclear nephrology that started with expert systems and statistical machine learning (ML) approaches, transitioned through feed forward neural networks (FFNN), landed with convolutional neural networks (CNNs) and deep learning (DL), and has emerging opportunities across the gamut of generative AI like large language models (LLMs), diffusion models, generative adversarial networks (GANs) and multimodal models like vision language models (VLMs). A range of AI tools across the nuclear nephrology ecosystem describe bespoke AI algorithms, commercial AI products, embedded AI tools from vendors, general-purpose and cross-domain AI frameworks. Applications in clinical workflow, research and development, and imaging are explored, highlighting the potential of AI in detection, classification, segmentation, prediction, data analysis and image enhancement. Emerging AI opportunities from generative AI, LLMs, VLMs, and segmentation foundation models such as the SAM, offer exciting multi-modal, few-shot learning that may re-imagine nuclear nephrology. There remains the need for considerable development and validation for widespread clinical utility of AI opportunities, and the need for consideration of ethical limitations and social justice.

Prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) has recently emerged as a promising molecular imaging tool for renal cell carcinoma (RCC), particularly for the clear-cell subtype (ccRCC). Unlike its expression in prostate cancer, PSMA in ccRCC is localised mainly to the endothelial cells of tumour-associated neovasculature, where it reflects angiogenic activity driven by the VHL-HIF-VEGF axis. This biological substrate provides the rationale for using PSMA-targeted imaging as a surrogate of angiogenesis and as a potential predictive biomarker in systemic therapy. Evidence from retrospective and prospective studies demonstrates high diagnostic accuracy of PSMA PET/CT in ccRCC, with detection rates exceeding 80-90%, outperforming conventional imaging and [¹⁸F]FDG PET/CT, particularly in metastatic disease. Quantitative PET-derived parameters, including SUVmax and heterogeneity indices, have shown correlation with VEGFR-2, PDGFR-β, and HIF-2α expression and may serve as predictors of response to tyrosine kinase inhibitors and immunotherapy combinations. PSMA-guided metastasis-directed therapy has also shown encouraging control rates in oligometastatic settings. Beyond its diagnostic role, PSMA PET offers a foundation for theragnostic applications. Early clinical experience with [¹⁷⁷Lu]Lu-PSMA radioligands and ongoing trials such as RENALUT and PRadR are exploring the feasibility of radioligand therapy targeting PSMA-positive ccRCC neovasculature. Although biological and kinetic barriers persist, PSMA-based imaging and therapy represent a feasible, rapidly translatable platform that bridges diagnosis and targeted treatment, marking a pivotal step towards personalised, imaging-guided management of advanced ccRCC.

Accurate response assessment in well-differentiated grade 1/2 neuroendocrine tumors (NETs) remains a major clinical challenge. Conventional size-based radiographic criteria such as Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 often fail to capture the slow, indolent nature of NETs. In these tumors, meaningful survival benefits, particularly after peptide receptor radionuclide therapy (PRRT) with [¹⁷⁷Lu]Lu-DOTATATE, occur without significant tumor shrinkage, while treatment-related necrotic or inflammatory changes can mimic progression. Several modified anatomical criteria, including Choi and mRECIST, have attempted to address these limitations, but results have been inconsistent and largely retrospective. Somatostatin receptor (SSTR)-PET/CT with [⁶⁸Ga]Ga-labeled analogues offers the opportunity to quantify biological response at the molecular level, reflecting alterations in receptor density and viable tumor burden. The Response Evaluation Criteria in Neuroendocrine Tumors (RECIN), developed from a post-hoc analysis of the phase II LuCAP trial, integrates semi-quantitative SSTR-PET parameters with conventional CT metrics. Using the summed SULpeak of up to five of the hottest lesions (up to two per organ), RECIN defines molecular partial response as a ≥25% reduction in summed SULpeak, while maintaining RECIST safeguards for progression. Applied to the prospective LuCAP trial dataset, RECIN identified additional responders, detected response earlier, and predicted progression-free survival more accurately than RECIST. By harmonizing biological and morphological information, RECIN provides a practical and reproducible framework tailored to the indolent, receptor-driven biology of NETs. Prospective multicenter validation, and correlation with longer term outcomes are needed to establish RECIN as standardized response criteria for PRRT as well as other treatment modalities for well-differentiated NETs.

Dynamic renal scintigraphy (DRS) has been in routine practice since late 70's and it shows kidney perfusion, concentration function and allows the evaluation of excretion function. The radiopharmaceuticals used for this procedure are excreted either via glomerular filtration or by tubular extraction. Either way DRS allows the nuclear medicine physician to quantify renal functions. There are many parameters introduced for clinical practice and described in detail in nuclear medicine guidelines. This paper aims to recall and underline the importance of these parameters and use of these parameters in advancing clinical research. Nuclear medicine has been working in close relation with basic research, its close collaboration with radiopharmacy provides development of new radiopharmaceuticals for kidney imaging, in addition, technological and software innovation enables us to perform faster acquisitions with lower doses and enables better resolution images. Still, processing and quantification in renal analysis is complicated for average nuclear medicine physicians. Recent advances in artificial intelligence have the potential to overcome this problem. With the help of such algorithms renal scintigraphies have the potential to enlighten clinical problems.

Fibroblast activation proteins (FAPs) are highly expressed in cancer-associated fibroblasts within the tumor microenvironment. Radiolabeled FAP inhibitors (FAPIs) either with 68Ga and 18F can assess the tumor stroma, thus offering a complementary perspective to other imaging modalities. Herein, we aimed to summarize current evidence on FAPI-based imaging in renal cell carcinoma (RCC) and bladder cancer (BC). Moreover, we addressed some perspectives about the utility of FAPI as a theragnostic agents in these urogenital cancers. Across the studies, emerged that FAP expression correlates with tumor aggressiveness, immune evasion, and poor prognosis in both RCC and BC. Indeed, clinical experiences demonstrate that FAPI PET achieves higher tumor-to-background ratios and improved detection of metastatic lesions, mainly peritoneal carcinomatosis and hepatic metastases, as compared with [¹⁸F]FDG. However, urinary excretion limits primary tumor assessment of FAPI like FDG imaging. Early trials of FAPI-based radioligand therapies, including [¹⁷⁷Lu]FAPI-2286, show promising safety and preliminary efficacy. Based on the current premises, FAPI seems a promising agent for genitourinary oncology, requiring further assessment through prospective studies.

Renal cell carcinoma (RCC) is a clinically heterogeneous malignancy with rising global incidence. Conventional imaging modalities such as CT and MRI provide primarily anatomical information but are limited in their ability to characterize tumors at the molecular level. Positron emission tomography/ computed tomography (PET/CT) imaging offers a promising alternative by enabling non-invasive molecular diagnostics. This review summarizes recent advances in PET-based imaging of RCC and highlights tracers with potential for future clinical application. Fluorodeoxyglucose (2-[¹⁸F]FDG) PET/CT, although well established in oncology, demonstrates limited sensitivity for primary RCC but may be useful for detecting distant metastases and local recurrence. Consequently, increasing attention has shifted toward more specific molecular tracers that may improve diagnostic performance. Among these, fibroblast activation protein inhibitor (FAPI)-based PET imaging has shown higher sensitivity than 2-[¹⁸F]FDG PET across several RCC subtypes, although current evidence remains restricted to small or early-phase studies. Sodium-18F-fluoride ([¹⁸F]NaF) PET/CT has demonstrated excellent detection rates for bone metastases in RCC, yet evidence is currently sparse. Furthermore, CD70-targeted immunoPET/CT-using tracers such as [⁶⁸Ga]Ga-NOTA-RCCB6-has shown high specificity for clear cell RCC (ccRCC) and superior performance compared with 2-[¹⁸F]FDG PET/CT in the identification of metastatic disease; however, broader clinical validation is still required. Carbonic anhydrase IX (CAIX)-targeted PET/CT provides high specificity for ccRCC, particularly in the detection of small lesions, staging, and post-immunotherapy follow-up. Emerging theranostic approaches employing [⁶⁸Ga]/[¹⁷⁷Lu]-labeled CAIX ligands may further enable integrated diagnostic and radionuclide therapeutic strategies. In conclusion, molecular imaging is increasingly recognized as a valuable tool in the diagnosis and management of RCC. Larger, multicenter studies are essential to define its role in routine clinical practice and to fully explore its potential in future theranostic applications.

Penile cancer is a rare malignancy predominantly of squamous cell histology, whose prognosis is strongly influenced by lymph node involvement. Conventional imaging methods such as CT, MRI, and ultrasound have limitations in assessing metastatic spread. [¹⁸F]FDG PET/CT, a metabolic imaging technique, has shown increasing value in the staging, restaging, and treatment monitoring of penile cancer. Evidence, although limited, demonstrates high sensitivity and specificity, particularly in detecting inguinal and pelvic lymph node metastases, outperforming conventional imaging in most cases. [¹⁸F]FDG PET/CT also aids in identifying distant metastases and distinguishing viable tumor tissue from post-treatment fibrosis. Preliminary data suggest a prognostic role of SUVmax values in correlating with tumor aggressiveness and survival outcomes. Current guidelines recommend its use mainly in patients with nodal involvement or inconclusive conventional imaging. Overall, [¹⁸F]FDG PET/CT represents a complementary tool that enhances staging accuracy, risk stratification, and treatment planning in penile cancer.

Esophageal squamous cell carcinoma (ESCC) exhibits heterogeneous responses to neoadjuvant therapy, necessitating early and accurate assessment. [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) PET/CT enables quantitative assessment of tumor glucose metabolism, correlating with pathological remission and long-term outcomes, while [¹⁸F] or [⁶⁸Ga]Ga-labeled fibroblast activation protein inhibitor (FAPI) PET/CT evaluates stromal metabolism, providing complementary information. Total-body PET/CT (uEXPLORER, United Imaging Healthcare Co.Ltd., Shanghai, China) with 194-cm long-axial field-of-view (LAFOV) offers long axial coverage, up to 68-fold higher sensitivity than conventional systems. It enables low-dose, rapid imaging, dynamic whole-body parametric imaging, and improves detection of small, low-uptake lesions as well as metastatic lesions in the distal upper or lower extremities in a single bed position. Delayed and dual-time imaging protocols, alone and/or combined with deep learning-based synthetic CT, further improve lesion detectability while minimizing radiation exposure. This narrative review summarizes evidence from conventional PET/CT studies, highlights the technical and clinical advantages of total-body PET/CT, and discusses its feasibility, quantitative capabilities, and potential to guide response-adapted management in ESCC based on our institutional experience.