Introduction: The ESMO and ECIO-ESOI consensus guidelines vary in their recommendations regarding the use of ¹⁸F-Fluorodeoxyglucose ([¹⁸F]FDG) PET/CT in the follow-up after thermal ablation in patients with colorectal liver metastases. This is partly because studies providing data on long-term benefits of [¹⁸F]FDG PET/CT are lacking. Therefore, a simulation model was developed to examine how follow-up with [¹⁸F]FDG PET/CT impacts treatment planning, health and cost outcomes. Methods: For an illustrative Dutch cohort, lifetime health and cost outcomes were simulated to assess the cost-effectiveness of performing a single additional [¹⁸F]FDG PET/CT. Patients followed a standard surveillance schedule consisting of three-monthly serum CEA and contrast-enhanced CT, plus [¹⁸F]FDG PET/CT 3–4 months after thermal ablation. Therapy could be repeated downstream the care pathway. Quality-of-life and survival estimates were based on disease stage and age. Costs were determined from a healthcare perspective incorporating costs related to diagnostics and treatments. The Consolidated Health Economic Evaluation Reporting Standards were followed. Results: Health benefits of additional [¹⁸F]FDG PET/CT were negligible, incremental QALYs < 0.001, whereas costs increased by €1,277, mainly due to the additional imaging. This lack of health benefits can be explained by the small subset of simulated patients (<5 %) in whom [¹⁸F]FDG PET/CT affected treatment planning. Discussion: Additional [¹⁸F]FDG PET/CT 3–4 months after thermal ablation is unlikely to be cost-effective. More research is needed to determine if using [¹⁸F]FDG PET/CT in subgroups of patients, or at alternative time points, is cost-effective. This requires collecting more (extensive) follow-up data across multiple centres to reflect heterogeneity between hospitals’ clinical practices.

The appropriate use criteria (AUC) documents are intended to aid medical practitioners in the appropriate use of imaging technology in specific clinical scenarios based on rigorous appraisal of the available published evidence. The purpose of this document is to summarize the appropriate use of PET/CT with ¹⁸F-FDG in the initial staging of malignant disease. A multidisciplinary expert panel convened to appraise an independently performed systematic review and develop the AUC for initial staging of head and neck cancer, lung cancer, breast cancer, esophageal cancer, colorectal cancer, pancreatic cancer, melanoma, lymphoma, myeloma, and sarcoma with an appropriateness score for each clinical scenario established by using a modified Delphi process (Table 1). The full document including the methodology details, discussion of evidence, appendices, and the supplemental material can be accessed at https://snmmi.org/Web/Clinical-Practice/Appropriate-Use-Criteria/Articles/Appropriate_Use_Criteria_for_18F-FDG_PET_CT_for_Initial_Staging_of_Malignant_Disease.

Background: Prior studies show that short-term treatment using tyrosine kinase inhibitors (TKIs) can reinduce radioiodine uptake and warrant ¹³¹I therapy in radioiodine-refractory differentiated thyroid cancer (RAI-R DTC). We aim to evaluate the potential of standard-of-care TKI lenvatinib to reinduce clinically meaningful radioiodine retention. Methods: Nine RAI-R DTC patients starting lenvatinib treatment for progressive advanced or metastatic disease, were included and underwent rhTSH-stimulated ¹²⁴I dosimetric procedures at baseline, week 6 (N=7) and week 12 (N=8). At all timepoints, the fraction of patients eligible for ¹³¹I therapy with a maximal activity of 7.4 GBq was assessed. Patients were considered eligible if at least one target lesion showed an expected mean absorbed dose ≥20 Gy. In total, 23 target lesions were segmented on¹²⁴I PET/CT images and their volumes estimated using low-dose CT images. Lesion size-specific recovery correction was applied to the measured mean activity concentration at each timepoint. Tumor dosimetry was performed using a mono-exponential fit and S-values from an internal dosimetry program for diagnostic nuclear medicine based on the ICRP adult reference voxel phantoms (IDAC-Dose2.1). Mean absorbed lesion dose per administered activity (LDpA), 24h-uptake and residence time in target lesions were compared between time points. Results: By our definition, none of the patients were found eligible for ¹³¹I therapy at any timepoint. Lenvatinib-induced partial response was observed in 59% and 75% of target lesions at week 6 and 12, respectively. Median LDpA was 0.08 (IQR: 0.04-0.17), 0.18 (0.08-0.36) and 0.17 (0.09-0.37) Gy/GBq for week 0, 6 and 12, respectively (p=0.08). The 24h-uptake and residence time were comparable between timepoints (p>0.22). Conclusion: Redifferentiation of RAI-R DTC to reinduce radioiodine uptake to a level that warrants ¹³¹I therapy may not be established by short-term lenvatinib treatment. Multi-targeted TKIs may not be as potent as selective TKIs in reinducing clinically meaningful radioiodine retention.

Background: Colorectal cancer is highly prevalent. The stromal tumour microenvironment significantly influences tumour behaviour, and cancer-associated fibroblasts (CAFs), as major component of tumour stroma, are increasingly studied. Specifically, CAF-marker fibroblast activation protein (FAP) is gaining interest as tracer for imaging using radiolabelled FAP-inhibitor (FAPI). We describe patterns of FAP-expression, and associations to intratumoural stroma amount, establishing a biological background and potential future reference to pathology assessment.

Materials and methods: Archival histological material from 125 stage-II/III CRC patients was collected. Haematoxylin-and-eosin staining was performed to determine the tumour-stroma ratio (TSR), indicating stromal percentages in primary tumours, lymph nodes (LNs) and biopsies. On immunohistochemistry stains, FAP-expression was semiquantitatively scored as little-no, heterogeneous, or moderate-high expression. Correlation of TSR and FAP-expression with Chi-square testing was assessed. Other patterns were also described, e.g. tumour epithelial FAP-expression.

Results: In total, 93 patients (40 stage-III colon [CC], 53 stage-II/III RC) were included. Correlation between 41 (44 %) stroma-high CRC (18/40 CC, 45 %; 23/53 RC, 43 %) with high FAP-expression was not significant (P = 0.428 CRC; P = 0.470 CC; P = 0.615 RC). The majority of CRC had any FAP-expression (78 CRC, 84 %), mostly the invasive front, and in most associated LN metastases (87 % CRC tumour-positive LN). However, FAP-expression was often heterogeneous, even staining healthy colon and lymphoid tissue.

Conclusions: CRCs and LN metastases generally express FAP, but levels vary significantly between and within tumours and have no direct correlation with TSR. Care has to be taken translating FAPI-PET/CT results with e.g. disease extent and activity, emphasizing the importance of multidisciplinary approach.

Objective
Metastatic castration-resistant prostate cancer (mCRPC) is a heterogeneous disease with varying survival outcomes. This study investigated whether baseline PSMA PET/CT parameters are associated with survival and treatment response.

Methods
Sixty mCRPC patients underwent [18F]PSMA-1007 PET/CT before treatment with androgen receptor-targeted agents (ARTAs) or chemotherapy. Intensity-based parameters, volumetric parameters, metastatic sites and DmaxVox (distance between the two outermost voxels) from baseline PSMA PET/CT were collected, as well as age, Gleason score and laboratory parameters. Cox regression analysis evaluated their prognostic value for overall survival (OS). Additionally, a preliminary lesion-level analysis was done (n = 241 lesions) with lesion location and twelve radiomic features selected from previous literature. Logistic regression evaluated their association with PSMA PET/CT-based lesion progression after 3–4 months of treatment.

Results
Total tumour volume (PSMA-TV) (HR = 1.41 per doubling [1.17–1.70]), total lesion uptake (TL-PSMA) (HR = 1.40 per doubling [1.16–1.69]) and DmaxVox (HR = 1.31 per 10 cm increase [1.07–1.62]) were prognostic for OS, each independent of baseline PSA level (HR = 0.82 per doubling [0.68–0.98]), haemoglobin level (HR = 0.68 per mmol/L increase [0.49–0.95]) and line of treatment. On lesion-level, location (prostate vs bone OR = 0.23 [0.06–0.83]) and SUVmean (OR = 1.72 per doubling [1.08–2.75]) were independent prognostic markers for lesion progression, morphological and texture-based radiomic features were not.

Conclusion
Baseline PSMA PET/CT scans have prognostic value in mCRPC patients and can potentially aid in treatment decision-making. DmaxVox can serve as a simpler alternative to PSMA-TV when automated segmentation software is not available. When combined with PSMA-TV, lower PSA levels indicated worse OS, which may be a marker of tumour dedifferentiation. Further research is needed to validate these models in larger patient cohorts.

Systematic literature reviews (SLRs) are fundamental for aggregating published evidence, identifying knowledge gaps and informing health economic evaluations, especially in the field of novel diagnostics where randomised controlled trials are commonly absent [1]. The global publishing output within the field of novel diagnostics is increasing rapidly owing to increasing efforts towards precision medicine. Simultaneously, the global publishing output within the field of health economics is increasing rapidly owing to increasing efforts towards value-based healthcare and present budget constraints. The number of publications focussing on the health economic impact of diagnostics almost doubled from 86,244 in 2010 to 152,404 in 2025 (PubMed search using MeSH terms ‘Diagnostic Techniques and Procedures’ and ‘Health Care Economics and Organizations’). Consequently, the workload of performing SLRs is increasing as the number of articles that requires screening grows larger. The average time to complete an SLR is over 15 months, while the proportion of truly relevant articles for data extraction may be as low as 1% of the total search results [2]. The high workload may reduce researchers’ willingness to conduct an SLR or may lead to search strategies that are too narrow when prioritising time constraints over review quality. Moreover, it may render an SLR outdated by the time it is published.

To plan optimal management in a patient with breast cancer (BC), accurate baseline staging and early detection and staging of recurrence are necessary.1-3 Representatives from the European Association of Nuclear Medicine (EANM) and the Society of Nuclear Medicine and Molecular Imaging (SNMMI) recently published the joint European-American guidelines on the role of 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography ([18F]FDG-PET/CT) in no special type (NST) BC, endorsed by several other imaging and clinical societies: the American College of Radiology (ACR), European Society of Surgical Oncology, European Society for Radiotherapy and Oncology (ESTRO), European Society of Breast Imaging, European Society of Radiology, and European Society of Breast Cancer Specialists (EUSOMA).1 Considering the low [18F]FDG-avidity in invasive lobular carcinoma (ILC), the EANM-SNMMI guidelines focused on NST BC. Guidelines from clinical societies such as the American National Comprehensive Cancer Network (NCCN),4 European Society for Medical Oncology (ESMO),5-7 and Advanced Breast Cancer (ABC) international consensus guidelines8 also evaluate imaging techniques, but they include all histological subtypes of BC. There is a lack of consistency in the optimal utilization of [18F]FDG-PET/CT among published guidelines. This manuscript summarizes available evidence, emphasizes the value of [18F]FDG-PET/CT for staging and restaging of patients with BC, and highlights agreements and discrepancies among international guidelines.

Background
The second most common breast cancer subtype is invasive lobular cancer (ILC). Its locoregional staging is challenging, even when using breast MRI. Different non-[18F]FDG PET tracers have been explored in these patients, and promising results were reported with [18F]FACBC. Nevertheless, no publications directly comparing breast MRI and [18F]FACBC PET are available.

Aim
To compare the performance of prone [18F]FACBC PET/CT and breast MRI for assessing disease extent in the breast and for depicting lymph node metastases in patients with locally advanced ILC.

Methods
Retrospective selection of case series of patients with proven locally advanced luminal-like ILC, who underwent both breast MRI and prone [18F]FACBC PET/CT, according to the local clinical standards.

Results
Eight patients were included. [18F]FACBC PET/CT performed similarly to MRI in T-staging and outperformed MRI in N-staging, especially outside axillary level I/II. [18F]FACBC uptake in the index breast lesion was on average 9 times higher than the breast background. Among the 6 patients submitted to surgery, [18F]FACBC provided the correct T&N staging in 5 patients, confirmed by pathology.

Conclusion
This initial descriptive case series suggests that prone [18F]FACBC PET/CT could be a valuable imaging tool for both local and regional staging of low-grade luminal-like ILC. A larger prospective clinical trial is needed to further evaluate this potential application.

Purpose
The value of integrating clinical variables, radiomics, and tumor-derived cell-free DNA (cfDNA) for the prediction of survival and response to chemoradiation of patients with resectable esophageal adenocarcinoma is not yet known. Our aim was to investigate if radiomics and cfDNA metrics combined with clinical variables can improve personalized predictions.

Methods and Materials
A cohort of 111 patients with resectable esophageal adenocarcinoma from 2 centers treated with neoadjuvant chemoradiation therapy was used for exploratory retrospective analyses. Models combining the clinical variables of the SOURCE survival model with radiomic features and cfDNA were built using elastic net regression and internally validated using 5-fold cross-validation. Model performance for overall survival (OS) and time to progression (TTP) were evaluated with the C-index and the area under the curve for pathologic complete response.

Results
The best-performing baseline models for OS and TTP were based on the combination of SOURCE-cfDNA that reached a C-index of 0.55 and 0.59 compared with 0.44 to 0.45 with SOURCE alone. The addition of restaging positron emission tomography radiomics to SOURCE was the most promising addition for predicting OS (C-index: 0.65) and TTP (C-index: 0.60). Baseline risk stratification was achieved for OS and TTP by combining SOURCE with radiomics or cfDNA, log-rank P < .01. The best-performing combination model for the prediction of pathologic complete response reached an area under the curve of 0.61 compared with 0.47 with SOURCE variables alone.

Conclusions
The addition of radiomics and cfDNA can improve the performance of an established survival model. External validity needs to be further assessed in future studies together with the optimization of radiomic pipelines.

Purpose: Nipple discharge is the third most common breast-related complaint. It is recommended to exclude malignancy in pathologic nipple discharge (PND). Mammography and ultrasound are the first-line conventional diagnostic (CD) imaging. Although magnetic resonance is often used as a complementary modality, molecular breast imaging (MBI) with Tc-99m sestamibi may be a suitable alternative. Considering the lack of information on this subject and its clinical importance, this study aimed to evaluate the role of MBI in ruling out malignancy in patients with PND and negative/indeterminate CD. Patients and Methods: Retrospective cohort single-center study including all patients with PND evaluated by CD and MBI between 2012 and 2020. Pathology was considered the gold standard. Follow-up was used when pathology was not available. Results: Of the 96 cases of PND included, 78 were benign, and 18 (20%) corresponded to breast cancer (BC). Although CD and MBI were concordant in the BIRADS classification in 81% (78/96), half of BC were detected by MBI only. BC was located directly behind the nipple in a minority of patients (11%), meaning that MBI could significantly prevent futile central ductal excision. MBI presented higher sensitivity (83% vs. 33%) and negative predictive value (96% vs. 86%) than CD alone, with similar specificity (89% vs. 92%) and positive predictive value (63% vs. 50%). The area under the curve of MBI and CD was 0,86 (P-value<0.001 [95% CI: 0.75-0.97]) and 0.63 (P-value=0.091 [95% CI: 0.47-0.79]), respectively. Conclusions: MBI showed good diagnostic accuracy for detecting BC in patients with PND with negative/indeterminate findings on CD imaging.

Purpose: This study investigated whether radiomic features extracted from [18F]FDG-PET scans acquired before and two weeks after neoadjuvant treatment, and their variation, provided prognostic parameters in locally advanced cervical cancer (LACC) patients treated with neoadjuvant chemo-radiotherapy (CRT) followed by radical surgery. Methods: We retrospectively included LACC patients referred to our Institution from 2010 to 2016. [18F]FDG-PET/CT was performed before neoadjuvant CRT (baseline) and two weeks after the start of treatment (early). Radiomic features were extracted after semi-automatic delineation of the primary tumour, on baseline and early PET images. Delta radiomics were calculated as the relative differences between baseline and early features. We performed 5-fold cross-validation stratified for recurrence and cancer-specific death, integrating dimensionality reduction of the radiomic features and variable hunting with importance within the folds. After supervised feature selection, radiomic models with the best-performing features for each timepoint, as well as clinical models and combined clinico-radiomic models, were built. Model performances are presented as C-indices, for prediction of recurrence/progression (disease-free survival, DFS) and cancer-specific death (overall survival, OS). Results: 95 patients were included. With a median follow-up of 76.0 months (95% CI: 59.5–82.1), 31.6% of patients had recurrence/progression and 20.0% died of disease. None of the models could predict DFS (C-indices ≤ 0.72). Model performances for OS yielded slightly better results, with mean C-indices of 0.75 for both the radiomic and combined model based on early features, 0.79 and 0.78 for the radiomic and combined model derived from delta features, and 0.76 for the clinical models. Conclusion: [18F]FDG-PET early and delta radiomic features could not predict DFS in patients with LACC treated with neoadjuvant CRT followed by radical surgery. Although slightly improved performances for the radiomic and combined models were observed in the prediction of OS compared to the clinical model, the added value of these parameters and their inclusion in the clinical practice seems to be limited.

Brushite calcium phosphate cements (bCPCs) are promising synthetic bone substitutes due to their bioactivity, osteoconductivity, and controlled degradation. However, their clinical use is limited by poor handling, low mechanical strength, and insufficient antimicrobial capability. This study explores the incorporation of α-tricalcium phosphate (α-TCP) and silk fibroin (SF) to enhance bCPC performance and enable localized antibiotic delivery using tetracycline (TC). Adding α-TCP improved compressive strength (up to 2.65 MPa), while SF in liquid or fiber form reinforced the matrix. The inclusion of TC and SF extended setting times (4–7 min initial; 7–30 min final) and maintained injectability (up to 50 %). Drug release studies showed a 10 % burst in the first 24 h, with a sustained release of 77 % over 14 days. These multifunctional bCPCs offer injectable, resorbable, and antibacterial properties, making them suitable for non-load-bearing bone repair applications.

Purpose: This study aims to systematically review and perform a meta-analysis to compare the diagnostic performance of fibroblast activation protein inhibitors (FAPI) radiopharmaceuticals and 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) in gynaecological cancers. Methods: A comprehensive search of PubMed/MEDLINE and EMBASE was conducted and updated to October 25, 2024, to identify clinical studies evaluating FAPI and [¹⁸F]FDG PET/CT or PET/MR in patients with gynaecological cancer. Quality was assessed using the QUADAS-2 tool (Quality Assessment of Diagnostic Accuracy Studies). Per-lesion pooled estimates of sensitivity, specificity, positive predictive value, and negative predictive value were calculated with 95% confidence intervals. Results: Ten studies were included for qualitative assessment and five studies focusing on ovarian cancer were included in the meta-analysis. The detection rates of primary cervical cancer ranged from 96 to 100% for both radiopharmaceuticals. For the primary tumour in ovarian cancer, the pooled sensitivities of ⁶⁸Ga-FAPI and [¹⁸F]FDG were 95% and 92%, and the pooled specificities were 81% for both radiopharmaceuticals. Nodal metastases detection was higher with ⁶⁸Ga-FAPI compared with [¹⁸F]FDG in cervical cancer. Similarly, in ovarian cancer the estimated pooled sensitivities of ⁶⁸Ga-FAPI and [¹⁸F]FDG were 97% and 88%, and the pooled specificities were 83% and 41%, respectively. At peritoneal metastases analysis in ovarian cancer, the pooled sensitivities of ⁶⁸Ga-FAPI and [¹⁸F]FDG were 97% and 70%, and the pooled specificities were 93% and 88%, respectively. At the visual assessment of peritoneal cancer scores, such as peritoneal cancer index, ⁶⁸Ga-FAPI detected a greater tumour burden compared with [¹⁸F]FDG. A comparative analysis of the PET semiquantitative parameters was also performed. Conclusion: Despite limited literature data, radiopharmaceuticals based on FAPIs are a promising alternative to [¹⁸F]FDG for imaging gynaecological cancers, in particular for the detection of nodal metastases in cervical and ovarian cancers, as well as for detecting peritoneal metastases in ovarian cancers. Larger prospective studies are needed to confirm these results and promote the inclusion of FAPI radiopharmaceuticals in clinical practice. Clinical trial number: Not applicable.

BACKGROUND: In patients with nonischemic cardiomyopathy and no late gadolinium enhancement (LGE) on cardiac magnetic resonance, risk prediction for the occurrence of sustained ventricular arrhythmias (VA) is challenging. Global and regional sympathetic denervation has been associated with VA in patients with ischemic cardiomyopathy. Its prognostic relevance in nonischemic cardiomyopathy is unknown. METHODS: Consecutive patients from the Leiden Nonischemic Cardiomyopathy Study who underwent programmed electrical stimulation, LGE-cardiac magnetic resonance, and 123-iodine meta-iodobenzylguanidine imaging between 2011 and 2019 were included. The presence of LGE and global and regional sympathetic denervation on 123-iodine meta-iodobenzylguanidine were evaluated, and patients were followed for the occurrence of VA. Global denervation was assessed using the heart-to-mediastinum ratio. Regional denervation was evaluated by calculating the number of denervated segments (DS), the ratio of DS, the summed defect score, and the weighted denervation size. RESULTS: Of 75 included patients (median age 63 years [25th-75th interquartile range (IQR) 54-68], 79% male, left ventricular ejection fraction 36% [IQR, 27-44], 37% inducible for VA), 35 had no LGE. During 4.5±1.6 years of mean follow-up, VA occurred in 8 of 35 (23%) patients without LGE and in 18 of 40 (45%) patients with LGE. Among patients without LGE, those with VA had greater regional sympathetic denervation (median number of DS 8 [IQR, 7-10] versus 2 [IQR, 1-5], P=0.004; median ratio of DS 0.5 [IQR, 0.5-0.7] versus 0.2 [IQR, 0.1-0.4], P=0.007; median defect score 36 [IQR, 30-41] versus 18 [IQR, 14-24], P=0.01; median weighted denervation size 47 [IQR, 38-54] versus 22 [IQR, 14-30]; P=0.01). In bivariate analysis, the number of DS (hazard ratio, 1.25 [95% CI, 1.06-1.46]; P=0.006) was associated with the occurrence of VA in patients without LGE. Denervation of ≥7 segments identified patients without LGE at risk for VA (area under the curve, 0.83; sensitivity, 88%; specificity, 89%). Among patients with LGE, the innervation state was not associated with VA during follow-up. CONCLUSIONS: In patients with nonischemic cardiomyopathy without LGE the extent of regional denervation may contribute to risk stratification for VA.

Purpose
Prostate-specific membrane antigen (PSMA) expression has been observed in a subset of soft tissue sarcomas, mainly in the neovascular endothelial cells. This feasibility study aimed to evaluate PSMA expression and PSMA PET/CT imaging in metastatic soft tissue sarcoma, providing important insights for potential future exploration of PSMA-targeted radioligand therapy.

Methods
This prospective single-center study included adult patients with metastatic soft tissue sarcoma, with measurable disease (lesion diameter > 1 cm), available biopsy/resection material, ECOG/WHO performance status of 0–2 and either no prior systemic treatment, progressive disease during/after treatment, or stable disease/partial response with the last dose > 8 weeks prior. Immunohistochemical PSMA staining was performed on previously obtained biopsy or resection material. In case of high PSMA expression, a [18F]-JK-PSMA-7 PET/CT scan evaluated tracer uptake, with adequate uptake defined as SUVmax > 8.

Results
Of 25 included patients, 11 (44%) had high PSMA expression: 4/11 leiomyosarcomas, 3/4 dedifferentiated liposarcomas, 2/5 undifferentiated pleomorphic sarcomas, 1/2 myxofibrosarcomas and 1/1 malignant peripheral nerve sheath tumour. Five of 11 patients agreed to a [18F]-JK-PSMA-7 PET/CT, of which 3 had lesions that showed adequate tracer uptake (SUVmax 10.7–16.7). However, uptake across all metastatic lesions was highly heterogeneous (median SUVmax = 3.8; range 0.5–16.7), indicating that these patients are unlikely to benefit sufficiently from PSMA-targeted therapy. The study was therefore terminated prematurely.

Conclusion
PSMA expression and PSMA tracer uptake in metastatic soft tissue sarcoma were highly heterogeneous. A deeper understanding of PSMA biology and improved patient selection criteria are essential for future application of PSMA-targeted radioligand therapy in this disease.

Purpose: Assessing renal perfusion in-vivo is challenging and quantitative information regarding renal hemodynamics is hardly incorporated in medical decision-making while abnormal renal hemodynamics might play a crucial role in the onset and progression of renal disease. Combining physiological stimuli with rubidium-82 positron emission tomography/computed tomography (⁸²Rb PET/CT) offers opportunities to test the kidney perfusion under various conditions. The aim of this study is: (1) to investigate the application of a one-tissue compartment model for measuring renal hemodynamics with dynamic ⁸²Rb PET/CT imaging, and (2) to evaluate whether dynamic PET/CT is sensitive to detect differences in renal hemodynamics in stress conditions compared to resting state. Methods: A one-tissue compartment model for the kidney was applied to cardiac ⁸²Rb PET/CT scans that were obtained for ischemia detection as part of clinical care. Retrospective data, collected from 17 patients undergoing dynamic myocardial ⁸²Rb PET/CT imaging in rest, were used to evaluate various CT-based volumes of interest (VOIs) of the kidney. Subsequently, retrospective data, collected from 10 patients (five impaired kidney functions and five controls) undergoing dynamic myocardial ⁸²Rb PET/CT imaging, were used to evaluate image-derived input functions (IDIFs), PET-based VOIs of the kidney, extraction fractions, and whether dynamic ⁸²Rb PET/CT can measure renal hemodynamics differences using the renal blood flow (RBF) values in rest and after exposure to adenosine pharmacological stress. Results: The delivery rate (K₁) values showed no significant (p = 0.14) difference between the mean standard deviation (SD) K₁ values using one CT-based VOI and the use of two, three, and four CT-based VOIs, respectively 2.01(0.32), 1.90(0.40), 1.93(0.39), and 1.94(0.40) mL/min/mL. The ratio between RBF in rest and RBF in pharmacological stress for the controls were overall significantly lower compared to the impaired kidney function group for both PET-based delineation methods (region growing and iso-contouring), with the smallest median interquartile range (IQR) of 0.40(0.28–0.66) and 0.96(0.62–1.15), respectively (p < 0.05). The K₁ of the impaired kidney function group were close to 1.0 mL/min/mL. Conclusions: This study demonstrated that obtaining renal K₁ and RBF values using ⁸²Rb PET/CT was feasible using a one-tissue compartment model. Applying iso-contouring as the PET-based VOI of the kidney and using AA as an IDIF is suggested for consideration in further studies. Dynamic ⁸²Rb PET/CT imaging showed significant differences in renal hemodynamics in rest compared to when exposed to adenosine. This indicates that dynamic ⁸²Rb PET/CT has potential to detect differences in renal hemodynamics in stress conditions compared to the resting state, and might be useful as a novel diagnostic tool for assessing renal perfusion.

Objective: This single-centre retrospective study aims to determine the incidence of therapy-induced surgical benefit in patients with non-metastatic gastrointestinal stromal tumour (GIST) treated with neoadjuvant tyrosine kinase inhibitors (TKI) and evaluate whether this can be predicted by radiological response criteria. Methods: Thirty-nine non-metastatic GIST patients were treated with neoadjuvant TKI treatment, followed by curative-intended surgery, and monitored using contrast-enhanced computed tomography (CE-CT). Surgical benefit was independently assessed by two surgical oncologists and was defined by de-escalation of surgical strategy or reduced surgical complexity. Radiological response between baseline and the last preoperative scan was determined through RECIST 1.1, Choi and volumetric criteria. Results: In this patient cohort, median neoadjuvant treatment interval was 8.3 (IQR, 3.9–10.6) months. Surgical benefit was gained in 22/39 patients. When comparing radiological criteria to findings on surgical benefit, accuracy, sensitivity, and specificity for RECIST 1.1 (90 %, 100.0 % and 82 %), Choi (64 %, 24 %, and 96 %) and volumetry (95 %, 100.0 %, and 91 %) were calculated. In 30/39 patients, temporal changes in tumour size over the course of treatment was assessed. Tumour volume reduced significantly in the surgical-benefit group compared to the non-benefit group (72 % vs. 25 %, p < 0.01) within three months. 14/19 surgical-benefit patients had an initial volume reduction above 66 %, after which volume reduced slightly with a median 3.1 % (IQR, 2.1–7.8 %) reduction. Conclusion: Surgical benefit after neoadjuvant treatment was achieved in 56 % of patients and was most accurately reflected by size-based response criteria. In patients with therapy-induced surgical benefit, nearly all treatment-induced volume reductions were achieved within three months.