Positron Emission Tomography (PET) and Single-Photon Emission Computerized tomography (SPECT), pose unique challenges when considering pediatric patient populations. Because both modalities require prolonged acquisition times, often ranging from 20 min to over an hour, minimizing patient motion is critical to prevent motion-related image quality degradation and ensuring diagnostic accuracy. While pharmacological sedation may avoid both problems, it carries inherent clinical risks, operational bottlenecks and comes with increased healthcare costs to society. In this paper, we assess the role of evidence-based, non-pharmacological strategies chronologically across the pediatric patient’s journey in the nuclear medicine department. By combining pre-visit psychological preparation, camera familiarization, optimized intravenous (IV) cannulation protocols, tailored physical and modality-specific positioning, and positive aftercare reinforcement, the nuclear medicine staff can optimize diagnostic image quality while prioritizing pediatric patient comfort and safety.

Actinium-225 (225Ac) has emerged as a pivotal alpha-emitter in modern radiopharmaceutical therapy, offering potent cytotoxicity with the potential for precise tumour targeting. Accurate, patient-specific image-based dosimetry for 225Ac is essential to optimize therapeutic efficacy while minimizing radiation-induced toxicity. Establishing a robust dosimetry workflow is particularly challenging due to the complex decay chain, low administered activity, limited count statistics, and the indirect measurement of daughter gamma emissions. Clinical single-photon emission computed tomography/computed tomography protocols with harmonized acquisition parameters, combined with robust volume-of-interest segmentation, artificial intelligence (AI)-driven image processing, and voxel-level analysis, enable reliable time-activity curve generation and absorbed-dose calculation, while reduced mixed-model approaches improve workflow efficiency, reproducibility, and patient-centred implementation. Cadmium zinc telluride-based gamma cameras further enhance quantitative accuracy, enabling rapid whole-body imaging and precise activity measurement, supporting patient-friendly dosimetry. Complementing these advances, the cerium-134/lanthanum-134 positron emission tomography in vivo generator provides a unique theranostic platform to noninvasively monitor 225Ac progeny redistribution, evaluate alpha-decay recoil, and study tracer internalization, particularly for internalizing vectors. Together, these technological and methodological innovations establish a mechanistically informed framework for individualized 225Ac dosimetry in targeted alpha therapy, supporting optimized treatment planning and precise response assessment. Continued standardization and validation of imaging, reconstruction, and dosimetry workflows will be critical to translate these approaches into reproducible, patient-specific clinical care.

A patient with metastasized prostate adenocarcinoma underwent 18F-PSMA-11 PET/CT restaging following 177Lu-PSMA-617 treatment and rising PSA-level. The maximum intensity projection image (right-side of the figure) demonstrated an intense homogenous tracer uptake throughout the bone marrow containing skeleton, whereas CT images showed specific bone metastases but no diffuse involvement, and previously known lymph node and liver metastases exhibited significantly reduced or absent uptake (see also left-side of the image, 18F-PSMA-11 MIP prior to 177Lu-PSMA-617 therapy). None of the patients that underwent imaging with the same tracer-batch demonstrated similar findings excluding free 18F as a potential cause for the imaging findings. Furthermore, the patient did not suffer from any bone marrow disorder previously reported to present with diffuse bone marrow uptake on PSMA-targeting PET/CT imaging [1, 2]. Of interest, the patient had received recombinant human erythropoietin, 100 µg of Aranesp, 24 h prior to imaging to treat his renal failure associated anemia. At this dose, Aranesp reaches a nanomolar concentration in the bone marrow resulting in stimulation of the Tissue Protective Receptor on endothelial cells leading to the creation of a massive systemic reservoir of PSMA-positive neovasculature that outcompetes PSMA-expressing prostate carcinoma lesions for radiotracer availability [3, 4]. This may explain the diffuse marrow uptake and the decreased visibility of known metastases [4]. The effect of erythropoietin on bone marrow mobilization and neovascularization can persist for 7–10 days [5]. This should be taken into consideration in order to avoid erroneous interpretation of 18F-PMSA-11 PET/CT imaging and unnecessary bone marrow toxicity of 177Lu-PSMA-617 treatment.

Background: Somatostatin receptors (SSTRs), especially subtype 2 (SSTR2), are increasingly recognized as valuable molecular targets in the imaging of chronic inflammatory and immune-mediated diseases. Their expression on activated immune and stromal cells enables specific, non-invasive detection of inflammatory activity using radio-labeled somatostatin analogs. Objective: This review aims to summarize current evidence on SSTR-targeted imaging across a range of chronic inflammatory and immune-mediated diseases, compare its diagnostic value with 18F-FDG PET/CT, and discuss biological mechanisms, clinical applications, and remaining challenges. Methods: A literature-based narrative review was conducted, integrating preclinical studies, clinical trials, and comparative imaging research involving SSTR PET/SPECT tracers such as 68Ga-DOTATATE, 68Ga-DOTANOC, 99ᵐTc-HYNIC-TOC, and 111In-pentetreotide in diseases including vasculitis, sarcoidosis, autoimmune myocarditis, rheumatoid arthritis, and thyroid-associated ophthalmopathy. Results: SSTR-targeted imaging has shown promising specificity for inflammatory lesions and provides favorable lesion-to-background contrast, particularly in tissues with high physiological FDG uptake such as the myocardium and brain. In vasculitis and sarcoidosis, SSTR-targeted tracers may complement FDG PET by improving diagnostic confidence and inter-observer consistency in selected small studies. Mechanistically, SSTR2 expression is closely associated with cytokine-driven immune activation, predominantly involving M1 macrophages. However, current evidence remains limited by heterogeneous receptor expression, variable myocardial uptake, and the lack of standardized imaging protocols. Conclusions: SSTR-targeted molecular imaging represents a biologically grounded and clinically promising complementary approach for assessing immune-mediated inflammation. Future developments in tracer design, quantitative standardization, and multicenter clinical validation are warranted to establish its role in precision diagnostics.

Tumor-associated macrophages (TAMs) are pivotal immune cells within the tumor stroma, whose dynamic alterations significantly impact tumor progression and therapeutic responses. Conventional methods for TAM detection, such as biopsy, are invasive and incapable of whole-body dynamic monitoring. In contrast, positron emission tomography (PET) and single-photon emission computed tomography (SPECT) offer a non-invasive imaging approach by targeting TAM-specific biomarkers like CD206, TSPO, and CCR2. This review comprehensively summarizes the advancements in TAM-targeted imaging probes, including cell surface markers, metabolic/functional markers, and multifunctional nanoprobe, while assessing their potential in tumor immune surveillance and tumor targeting therapeutic applications. While current probes, including 68Ga-NOTA-anti-CD206 and 64Cu-Macrin, have exhibited high specificity and theragnostic potential in preclinical and early clinical trials, challenges such as target heterogeneity, off-target effects, and clinical translation persist. Moving forward, the advancement of multi-target probes, optimization of pharmacokinetics, and incorporation of multimodal imaging technologies are anticipated to further enhance the impact of TAM-targeted imaging in precision medicine and tumor immunotherapy, fostering the refinement of personalized treatment strategies and improving patient outcomes.

In non-small cell lung carcinoma (NSCLC) carcinoma, the CT-part of the FDG PET/CT examination is of primary importance for T (tumor)-status assessment, while information derived from the primary tumor on the FDG-part of the examination may provide additional information on N- (lymph node) status. FDG PET/CT imaging was shown to have an overall sensitivity of 85% and a specificity of 84% for identifying LN involvement in NSCLC. Parameters that may predict the presence and quantify the risk of LN-involvement in NSCLC missed on FDG PET/CT imaging are tumor size and its increase over time, tumor differentiation degree, the number of days elapsed from the time of initial diagnosis, an adenocarcinoma subtype, a central versus peripheral location of the primary tumor and a solid versus mixed solid-ground glass radiologic character. Nomograms incorporating several of these variables have been published and made available for clinical usage. Furthermore, FDG PET/CT imaging was shown to have an overall higher sensitivity for identifying extra-thoracic metastases than convential morphological imaging and this especially for bone and adrenal lesions. In small cell lung carcinoma (SCLC), limited available data have shown FDG PET/CT imaging to be systematically more accurate for staging purposes when compared to conventional staging and to lead to a change in disease stage (limited versus extensive disease) in up to 15% of SCLC-patients.

Prostate-specific membrane antigen (PSMA) has been previously shown to be over-expressed on newly formed vessels of a wide variety of solid tumors other than prostate carcinoma. Accordingly, the potential role of PSMA-targeted positron emitting tomography for staging, restaging and prediction of response to PSMA-targeted treatment modalities, including 177Lu-PSMA-617, in other solid tumor types is being explored. Results derived from currently available studies on the role of PSMA-targeted imaging in solid tumors other than prostate carcinoma are encouraging with amongst others evidence of improved diagnostic accuracy in patients suffering from clear cell renal cell carcinoma and adenoid cystic adenocarcinoma of the salivary gland when compared to standard of care imaging, leading to a change in patient management in a significant number of patients. Furthermore, in hepatocellular carcinoma and glioblastoma, the comparable diagnostic accuracy of PSMA-targeted PET imaging when compared to contrast-enhanced CT and MRI suggest a potential use of PSMA-targeted PET when findings derived from morphological imaging are doubtful. Also, high PSMA-targeted PET-ligand uptake has been identified in iodine refractory thyroid carcinoma lesions as well as in triple negative breast carcinoma, suggesting a potential role for PSMA-targeted therapy in these patient populations. Thus far published results warrant, however, confirmation by larger prospective studies additionally assessing the longitudinal impact on patient outcomes.

Prostate-specific membrane antigen (PSMA), a transmembrane glycoprotein, was shown to be expressed 100–1000 fold higher in prostate adenocarcinoma as compared to normal prostate epithelium. Given the enzymatic function of PSMA with the presence of an internalization triggering motif, various Glu-urea-Lys-based inhibitors have been developed and, amongst others, radiolabeled with positron emitters for targeted positron emission tomography imaging such as 68Ga-PSMA-HBED-CC Glu-urea-Lys(Ahx) as well as with beta and alpha-emitting radioisotopes for targeted therapy, e.g., 177Lu-PSMA-617. In this paper, we review and discuss the potential implications for targeted imaging and therapy of altered PSMA-glycosylation, of PSMA-driven activation of the P13K/Akt/mTOR, of the evolution over time and the relationship with androgen signaling and changes in DNA methylation of PSMA, and of androgen deprivation therapy (ADT) in prostate carcinoma.

Positron emission tomography (PET) using radiolabeled prostate-specific membrane antigen targeting PET-imaging agents has been increasingly used over the past decade for imaging and directing prostate carcinoma treatment. Here, we summarize the available literature data on radiomics and machine learning using these imaging agents in prostate carcinoma. Gleason scores derived from biopsy and after resection are discordant in a large number of prostate carcinoma patients. Available studies suggest that radiomics and machine learning applied to PSMA-radioligand avid primary prostate carcinoma might be better performing than biopsy-based Gleason-scoring and could serve as an alternative for non-invasive GS characterization. Furthermore, it may allow for the prediction of biochemical recurrence with a net benefit for clinical utilization. Machine learning based on PET/CT radiomics features was also shown to be able to differentiate benign from malignant increased tracer uptake on PSMA-targeting radioligand PET/CT examinations, thus paving the way for a fully automated image reading in nuclear medicine. As for prediction to treatment outcome following 177Lu-PSMA therapy and overall survival, a limited number of studies have reported promising results on radiomics and machine learning applied to PSMA-targeting radioligand PET/CT images for this purpose. Its added value to clinical parameters warrants further exploration in larger datasets of patients.

Introduction: Cervical cancer lesions, like most solid tumors, grow large, and outgrow their blood supply which leads to hypoxia. Hypoxia has been shown to upregulate the presence and functions of cancer associated fibroblasts (CAFs) which results in increased aggressiveness. Hypoxia inducible factor-1α (HIF-1α) is a well-studied marker of hypoxia. PET imaging of gynecological cancers with 68Ga-FAPI has been documented. We aimed to utilize 68Ga-FAPI PET as a surrogate tracer of hypoxia and we correlated the imaging findings with immunohistochemical analysis of HIF-1α expression.

Here, we report on the added value of principal component analysis applied to a dataset of texture features derived from 39 solitary pulmonary lung nodule (SPN) lesions for the purpose of differentiating benign from malignant lesions, as compared to the use of SUVmax alone. Texture features were derived using the LIFEx software. The eight best-performing first-, second-, and higher-order features for separating benign from malignant nodules, in addition to SUVmax (MaximumGreyLevelSUVbwIBSI184IY), were included for PCA. Two principal components (PCs) were retained, of which the contributions to the total variance were, respectively, 87.6% and 10.8%. When included in a logistic binomial regression analysis, including age and gender as covariates, both PCs proved to be significant predictors for the underlying benign or malignant character of the lesions under study (p = 0.009 for the first PC and 0.020 for the second PC). As opposed to SUVmax alone, which allowed for the accurate classification of 69% of the lesions, the regression model including both PCs allowed for the accurate classification of 77% of the lesions. PCs derived from PCA applied on selected texture features may allow for more accurate characterization of SPN when compared to SUVmax alone.

Lutetium-177 prostate-specific membrane antigen radioligands (177Lu-PSMA) are new therapeutic agents for the treatment of metastatic castration-resistant prostate cancer (mCRPC). We evaluated the prognostic value of circulating tumour DNA (ctDNA) profiling in patients with mCRPC starting treatment with 177Lu-PSMA I&T. Between January 2020 and October 2022, patients with late-stage mCRPC (n = 57) were enrolled in a single-centre observational cohort study. Genomic alterations in the AR gene, PI3K signalling pathway, TP53, and TMPRSS2-ERG were associated with progression-free survival (PFS) on Kaplan-Meier and multivariable Cox regression analyses. Median PFS of 3.84 mo (95% confidence interval [CI] 3.3-5.4) was observed, and 21/56 (37.5%) evaluable patients experienced a prostate-specific antigen response of ≥50% during treatment. Among 46 patients who provided a blood sample for profiling before 177Lu-PSMA treatment. ctDNA was detected in 39 (84.8%); higher ctDNA was correlated with shorter PFS. Genomic structural rearrangements in the AR gene (hazard ratio [HR] 9.74, 95% confidence interval [CI] 2.4-39.5; p = 0.001) and alterations in the PI3K signalling pathway (HR 3.58, 95% CI 1.41-9.08; p = 0.007) were independently associated with poor 177Lu-PSMA prognosis on multivariable Cox regression. Prospective evaluation of these associations in biomarker-driven trials is warranted. Patient summary:We examined cell-free DNA in blood samples from patients with advanced metastatic prostate cancer who started treatment with lutetium-177-PSMA, a new radioligand therapy. We found that patients with genetic alterations in the androgen receptor gene or PI3K pathway genes did not experience a lasting benefit from lutetium-177-PSMA.

Hypoxia leads to changes in tumor microenvironment (upregulated CAFs) with resultant aggressiveness. A key factor in the physiological response to hypoxia is hypoxia-inducible factor-1alpha (HIF-1α). [68Ga]Ga-FAPI PET imaging has been demonstrated in various cancer types. We hypothesized that [68Ga]Ga-FAPI PET may be used as an indirect tracer for mapping hypoxia by correlating the image findings to pathological analysis of HIF-1α expression. The [68Ga]Ga-FAPI PET/CT scans of women with cancer of the cervix were reviewed and the maximum and mean standardized uptake value (SUVmax and SUVmean) and FAPI tumor volume (FAPI-TV) were documented. Correlation analysis was performed between PET-derived parameters and immunohistochemical staining as well as between PET-derived parameters and the presence of metastasis. Ten women were included. All patients demonstrated tracer uptake in the primary site or region of the primary. All patients had lymph node metastases while only six patients had distant visceral or skeletal metastases. The mean SUVmax, SUVmean, and FAPI-TV was 18.89, 6.88, and 195.66 cm3, respectively. The average FAPI-TV for patients with additional sites of metastases was higher than those without. Immunohistochemistry revealed varying intensities of HIF-1α expression in all tested samples. There was a positive correlation between the presence of skeletal metastases and staining for HIF-1α (r=0.80;p=0.017). The presence of skeletal metastasis was correlated to the HIF-1⍺ staining (percentage distribution). Furthermore, the FAPI-TV was a better predictor of metastatic disease than the SUVmax.

225Ac-PSMA-617 has demonstrated good anti-tumor effect as a treatment option for metastatic castration-resistant prostate cancer (mCRPC) patients. No study has previously assessed treatment outcome and survival following 225Ac-PSMA-617 treatment of de novo metastatic hormone-sensitive prostate carcinoma (mHSPC) patients. Based on the potential side effects that are known and explained to the patients by the oncologist, some of the patients refused the standard treatment and are seeking alternative therapies. Thus, we report our preliminary findings in a retrospective series of 21 mHSPC patients that refused standard treatment options and were treated with 225Ac-PSMA-617. We retrospectively reviewed patients with histologically confirmed de novo treatment-naïve bone ± visceral mHSPC that were treated with 225Ac-PSMA-617 radioligand therapy (RLT). Inclusion criteria included an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2, treatment-naive bone ± visceral mHSPC, and patients refusal for ADT ± docetaxel, abiraterone acetate, or enzalutamide. We evaluated the response to treatment using prostate-specific antigen (PSA) response and the progression-free survival (PFS) and overall survival (OS) as well as the toxicities. Twenty-one mHSPC patients were included in this preliminary work. Following treatment, twenty patients (95

Abstract Background FDG-PET/CT has a high negative predictive value to detect residual nodal disease in patients with locally advanced squamous cell head and neck cancer after completing concurrent chemoradiotherapy (CCRT). However, the positive predictive value remains suboptimal due to inflammation after radiotherapy, generating unnecessary further investigations and possibly even surgery. We report the results of a preplanned secondary end point of the ECLYPS study regarding the potential advantages of dual time point FDG-PET/CT imaging (DTPI) in this setting. Standardized dedicated head and neck FDG-PET/CT images were obtained 12 weeks after CCRT at 60 and 120 min after tracer administration. We performed a semiquantitative assessment of lymph nodes, and the retention index (RI) was explored to optimize diagnostic performance. The reference standard was histology, negative FDG-PET/CT at 1 year, or > 2 years of clinical follow-up. The time-dependent area under the receiver operator characteristics (AUROC) curves was calculated. Results In total, 102 subjects were eligible for analysis. SUV values increased in malignant nodes (median SUV1 = 2.6 vs. SUV2 = 2.7; P = 0.04) but not in benign nodes (median SUV1 = 1.8 vs. SUV2 = 1.7; P = 0.28). In benign nodes, RI was negative although highly variable (median RI = − 2.6; IQR 21.2), while in malignant nodes RI was positive (median RI = 12.3; IQR 37.2) and significantly higher (P = 0.018) compared to benign nodes. A combined threshold (SUV1 ≥ 2.2 + RI ≥ 3%) significantly reduced the amount of false-positive cases by 53% (P = 0.02) resulting in an increased specificity (90.8% vs. 80.5%) and PPV (52.9% vs. 37.0%), while sensitivity (60.0% vs. 66.7%) and NPV remained comparably high (92.9% vs. 93.3%). However, AUROC, as overall measure of benefit in diagnostic accuracy, did not significantly improve (P = 0.62). In HPV-related disease (n = 32), there was no significant difference between SUV1, SUV2, and RI in malignant and benign nodes, yet this subgroup was small. Conclusions DTPI did not improve the overall diagnostic accuracy of FDG-PET/CT to detect residual disease 12 weeks after chemoradiation. Due to differences in tracer kinetics between malignant and benign nodes, DTPI improved the specificity, but at the expense of a loss in sensitivity, albeit minimal. Since false negatives at the 12 weeks PET/CT are mainly due to minimal residual disease, DTPI is not able to significantly improve sensitivity, but repeat scanning at a later time (e.g. after 12 months) could possibly solve this problem. Further study is required in HPV-associated disease.

225Ac-PSMA-617, targeting the prostate-specific membrane antigen (PSMA), which is overexpressed on prostate cancer cells, has shown a remarkable therapeutic efficacy in heavily pretreated patients with metastatic castration-resistant prostate carcinoma (mCRPC). Here, we report on treatment outcome and survival using this novel treatment modality in a series of 53 patients with mCRPC directly after their androgen deprivation treatment (ADT). Methods: 225Ac-PSMA-617 was administered to 53 such patients. 68Ga-PSMA PET/CT was obtained at baseline, before every treatment cycle, and on follow-up to select patients for treatment, determine the activity to be administered, and assess their response. Serial prostate-specific antigen (PSA) measurements were obtained for response assessment. Results: The median age of the patients was 63.4 y (range, 45-83 y). In total, 167 cycles were administered (median, 3; range, 1-7). Forty-eight patients (91%) had a PSA decline of at least 50%, and 51 patients (96%) had any decline in PSA. 68Ga-PSMA PET findings became negative in 30 patients. In the multivariate analysis, a PSA decline of at least 50% proved predictive of both progression-free survival (PFS) and overall survival (OS), and platelet count also proved predictive for PFS. The median estimated OS was 9 mo for patients with a PSA decline of less than 50% but was not yet reached at the latest follow-up (55 mo) for patients with a PSA decline of 50% or more. The estimated median PFS was 22 mo for patients with a PSA decline of at least 50% and 4 mo for patients with a PSA decline of less than 50%. No severe hematotoxicity was noted, and only 3 patients had grade III-IV nephrotoxicity. The commonest toxicity seen was grade I-II xerostomia, observed in 81% of patients. Conclusion: In 91% of 53 patients with mCRPC, treatment with 225Ac-PSMA-617 immediately after ADT resulted in at least a 50% decrease in PSA level. Furthermore, a PSA decline of at least 50% proved the single most important factor predicting PFS and OS after 225Ac-PSMA-617 treatment. Of interest, median OS in patients with a PSA decline of at least 50% was not yet reached at the latest follow-up (55 mo). These favorable results suggest that it would be of major clinical relevance to perform a prospective randomized study comparing 225Ac-PSMA-617 with current standard-of-care treatment options such as enzalutamide, abiraterone acetate, and docetaxel after ADT.