Seminars in nuclear medicine最新文献

Nuclear medicine infection imaging has traditionally relied on semantic visual interpretation supported by simple semi-quantitative indices. While effective, this paradigm is limited by observer dependence, restricted sensitivity to subtle or diffuse disease, and difficulty in standardising interpretation across centres. Advances in quantitative imaging, radiomics and artificial intelligence (AI) are reshaping this landscape. These complementary domains, collectively conceptualised as computomics, extend infection imaging from qualitative pattern recognition toward objective, reproducible and data-driven characterisation of disease. Quantitative imaging converts tracer distribution into measurable biological metrics, ranging from simple region-of-interest count ratios to standardised uptake values and kinetic parameters. Radiomics builds on this foundation by extracting high-dimensional features describing intensity, shape, texture and spatial heterogeneity, revealing image information not appreciable to the human eye. AI, through machine learning and deep learning approaches, integrates quantitative and radiomic data with clinical variables to automate segmentation, enhance reconstruction, support classification, and enable predictive modelling. Together, these tools offer potential to improve differentiation of infection from sterile inflammation, quantify disease burden, monitor therapy response, and standardise interpretation in complex scenarios. Quantitative accuracy and radiomic stability remain highly dependent on acquisition, reconstruction and processing parameters. AI-driven image enhancement and denoising may improve visual appearance while altering voxel statistics, with downstream effects on quantitative metrics and texture features. Variability in feature definitions, segmentation methods and analysis pipelines further limits reproducibility. Consequently, harmonisation, standardisation, transparent validation and physics-informed AI models are essential.

Pre-clinical nuclear medicine occupies a distinctive position in biomedical research, simultaneously driving radioligand discovery for diagnostic imaging and targeted radionuclide therapy while serving as a cross-disciplinary tool for investigating drug development, physiology, disease mechanisms and treatment response. These dual roles place significant ethical, operational and environmental demands on animal-based research. Although the classical 3Rs (replace, reduce and refine) remain foundational, rapid advances in theranostics, molecular targeting, high-content imaging and artificial intelligence have outpaced the traditional framework. Emerging capabilities such as in-silico biodistribution modelling, digital twins, ultra-low-dose AI-enhanced imaging, automated radiochemistry, distributed data analytics and alternative biological platforms now provide realistic opportunities to displace, minimise or ethically enhance in-vivo research. A modernised, dynamic framework is proposed comprising six inter-connected principles: replace, reduce, refine, re-engineer, revolutionise and re-imagine. Together, these 6Rs better reflect the contemporary scientific, technological and societal context of pre-clinical nuclear medicine. AI and digital methods augment the classical 3Rs, re-engineer research pipelines, generate measurable "12E" outcomes (enhanced, efficient, effective, ethical, environmental, economical, evidence-driven, equitable, evolutionary, empowered, enduring and elastic) and revolutionise translational capability. The 6R model provides a future-ready ethical and operational architecture for pre-clinical nuclear medicine, aligning radioligand development and mechanistic imaging research with modern principles of sustainability, transparency, computational innovation and animal welfare.

Diuretic renography remains central to evaluating suspected urinary tract obstruction in children, yet interpretation varies across centers. Modern pediatric practice benefits from standardized acquisition and analysis, including harmonized hydration, furosemide timing, and drainage parameters such as half-time (T½), normalized residual activity (NORA), and parenchymal transit time (PTT). Diuretic renography in children, including its indications, practical patient preparation and acquisition protocols, and interpretive framework linked to clinical decision points are discussed. Key protocol choices (F-15, F-0, F + 20/30), bladder management, minimization of sedation, and motion control are also reviewed, and pitfalls described at the end. Consistent technique-adequate hydration, standardized furosemide dosing, dynamic acquisition with post-void/post-upright positioning/delayed images, and quantitative assessment-improves reproducibility and reduces equivocal studies. NORA complements T½ by accounting for kidney size and residual activity; PTT helps separate obstructive from non-obstructive delay and may predict outcomes after pyeloplasty. Special populations (infants, neurogenic bladder, post-operative states) require tailored protocols and cautious interpretation of quantitative parameters. A practical, physiology-based approach to pediatric diuretic renography reduces variability and aligns imaging with urologic management. Standardized technique and transparent reporting of drainage metrics (T½, NORA, PTT) should be performed widely to optimize care and facilitate multi-center research.

Bladder cancer (BC) poses significant diagnostic challenges for molecular imaging, as [¹⁸F]FDG PET/CT demonstrates not only intense urinary excretion that obscures pelvic lesions but also inherently limited diagnostic accuracy in differentiating tumor from inflammation and in detecting small or low-grade lesions. These shortcomings have spurred the development of non-FDG PET tracers aimed at improving lesion detectability and providing more tumor-specific information. Early-generation tracers such as [¹¹C]acetate, [¹¹C]/[¹⁸F]choline, [¹⁸F]fluciclovine, [¹¹C]methionine, as well as PSMA-targeted agents demonstrated feasibility for imaging primary and recurrent disease but offered modest sensitivity for nodal or distant metastases, restricting their clinical impact. In contrast, novel molecularly targeted agents, including fibroblast activation protein (FAP) inhibitors and Nectin-4-directed ligands, have emerged as promising tracers with high tumor-to-background ratios, less urinary clearance, and strong correlation with histopathologic markers. [⁶⁸Ga]FAPI PET has shown superior lesion detection and staging performance compared with [¹⁸F]FDG, while Nectin-4 PET offers potential for precision imaging and theranostic integration with antibody-drug conjugate therapies. Collectively, these advances signal a shift from conventional metabolic imaging toward receptor-targeted, biologically driven PET approaches that enable more accurate, personalized assessment of bladder cancer.

Infection of the nephro-urological system remains a common and clinically challenging problem, particularly in patients with atypical presentations, prior instrumentation, or underlying immunosuppression. Conventional anatomical imaging plays a central role in identifying obstruction, collections, and complications but is often limited in distinguishing active infection from sterile inflammation or post-interventional change. Nuclear medicine techniques provide complementary functional and molecular information that can clarify disease activity, define extent, and influence patient management. This review presents a practical, nuclear medicine-focused overview of imaging approaches for nephro-urological infection. Established techniques, including ⁹⁹ᵐTc-DMSA imaging, radiolabelled white blood cell scintigraphy, and ¹⁸F-FDG PET/CT, are discussed with emphasis on tracer biology, physiological renal handling, and common interpretive pitfalls. Clinical scenarios such as acute and chronic pyelonephritis, renal abscess, transplant infection, and device-related infection are used to illustrate appropriate tracer selection and integration with anatomical imaging. Special populations, including paediatric patients, immunocompromised individuals, and renal transplant recipients, are considered, alongside practical algorithms and teaching points aimed at improving clinical applicability. Emerging developments in bacteria-specific tracers, quantitative imaging, and hybrid modalities are also reviewed. By adopting a biologically informed and question-driven approach, nuclear medicine can play an increasingly important role in the diagnosis and management of nephro-urological infection.

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.

The concept of death by neurologic criteria (DNC), a medicolegal construct also known as "brain death", is over 50 years old. Ancillary examinations have a well-defined role in this diagnosis, principally when the clinical examination cannot be completely or safely performed. Radionuclide studies, which provide a combination of ease of performance and high accuracy, remain amongst the most recommended ancillary studies in current clinical guidelines. There are in fact 2 discrete categories of radionuclide studies, using hydrophilic or lipophilic radiopharmaceuticals (RPs), which have overlapping but discrete features, described in this review. Lipophilic RPs that provide both flow and parenchymal imaging are superior to hydrophilic RPs that provide only flow imaging. Various signs have been described in regard to interpretation of the radionuclide study and serve to encapsulate findings in a concise and clearly understood manner. The trident and empty skull signs, relevant to flow and parenchymal phases of radionuclide examinations, respectively, remain the key elements of interpretation and are both necessary and sufficient to make the diagnosis of DNC. The hot nose sign and the sagittal sinus sign are not sufficiently specific for this diagnosis, and do not have a place in the interpretation of DNC examinations. Because it operates in the medicolegal realm and requires rapid and definitive reporting, the nuclear medicine physician must be particularly familiar with methods and interpretation of scintigraphy as an ancillary examination in determination of death by neurologic criteria.

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.

Recent years have seen substantial advancements in renal positron emission tomography (PET) imaging. Targets for PET imaging include, but are not limited to, angiotensin receptors, norepinephrine transporters, and sodium-glucose cotransporters. All of those novel radiotracers inherit advantages of F18 radiochemistry, thereby allowing for higher clinical throughput or potentially increased diagnostic accuracy. The potential of such novel F18-labeled agents to yield imaging biomarkers, and their potential role for future renal molecular imaging, will be presented in the following article.