Fibroblast Activation Protein-Directed Imaging Outperforms 18F-FDG PET/CT in Malignant Mesothelioma: A Prospective, Single-Center, Observational Trial.

The fibroblast activation protein (FAP) is highly expressed in tumor and stromal cells of mesothelioma and thus is an interesting imaging and therapeutic target. Previous data on PET imaging with radiolabeled FAP inhibitors (FAPIs) suggest high potential for superior tumor detection. Here, we report the data of a large malignant pleural mesothelioma cohort within a 68Ga-FAPI46 PET observational trial (NCT04571086). Methods: Of 43 eligible patients with suspected or proven malignant mesothelioma, 41 could be included in the data analysis of the 68Ga-FAPI46 PET observational trial. All patients underwent 68Ga-FAPI46 PET/CT, contrast-enhanced CT, and 18F-FDG PET/CT. The primary study endpoint was the association of 68Ga-FAPI46 PET uptake intensity and histopathologic FAP expression. Furthermore, secondary endpoints were detection rate and sensitivity, specificity, and positive and negative predictive values as compared with 18F-FDG PET/CT. Datasets were interpreted by 2 masked readers. Results: The primary endpoint was met, and the association between 68Ga-FAPI46 SUVmax or SUVpeak and histopathologic FAP expression was significant (SUVmax: r = 0.49, P = 0.037; SUVpeak: r = 0.51, P = 0.030).68Ga-FAPI46 and 18F-FDG showed similar sensitivity by histopathologic validation on a per-patient (100.0% vs. 97.3%) and per region (98.0% vs. 95.9%) basis. Per-region analysis revealed higher 68Ga-FAPI46 than 18F-FDG specificity (81.1% vs. 36.8%) and positive predictive value (87.5% vs. 66.2%). Conclusion: We confirm an association of 68Ga-FAPI46 uptake and histopathologic FAP expression in mesothelioma patients. Additionally, we report high sensitivity and superior specificity and positive predictive value for 68Ga-FAPI46 versus 18F-FDG.

Dose-Response Relationship in Patients with Liver Metastases from Neuroendocrine Neoplasms Undergoing Radioembolization with 90Y Glass Microspheres.

The benefit of multicompartment dosimetry in the radioembolization of neuroendocrine neoplasms is not firmly established. We retrospectively assessed its potential with patient outcome. Methods: Forty-three patients were eligible. The association of mean absorbed dose (MAD) for tumors and treatment response was tested per lesion with a receiver operating characteristic curve analysis, and the association of MAD with progression-free survival (PFS) and overall survival was tested per patient using uni- and multivariate Cox regression analyses. Results: The area under the curve for treatment response based on MAD was 0.79 (cutoff, 196.6 Gy; P < 0.0001). For global PFS, grade (grade 2 vs. 1: hazard ratio [HR], 2.51; P = 0.042; grade 3 vs. 1: HR, 62.44; P < 0.001), tumor origin (HR, 6.58; P < 0.001), and MAD (HR, 0.998; P = 0.003) were significant. For overall survival, no prognostic parameters were significant. Conclusion: In line with prior publications, a MAD of more than 200 Gy seemed to favor treatment response. MAD was also associated with PFS and may be of interest for radioembolization planning for neuroendocrine neoplasm patients.

Body composition impacts outcome of bronchoscopic lung volume reduction in patients with severe emphysema: a fully automated CT-based analysis.

Chronic Obstructive Pulmonary Disease (COPD) is characterized by progressive and irreversible airflow limitation, with individual body composition influencing disease severity. Severe emphysema worsens symptoms through hyperinflation, which can be relieved by bronchoscopic lung volume reduction (BLVR). To investigate how body composition, assessed through CT scans, impacts outcomes in emphysema patients undergoing BLVR. Fully automated CT-based body composition analysis (BCA) was performed in patients with end-stage emphysema receiving BLVR with valves. Post-interventional muscle and adipose tissues were quantified, body size-adjusted, and compared to baseline parameters. Between January 2015 and December 2022, 300 patients with severe emphysema underwent endobronchial valve treatment. Significant improvements were seen in outcome parameters, which were defined as changes in pulmonary function, physical performance, and quality of life (QoL) post-treatment. Muscle volume remained stable (1.632 vs. 1.635 for muscle bone adjusted ratio (BAR) at baseline and after 6 months respectively), while bone adjusted adipose tissue volumes, especially total and pericardial adipose tissue, showed significant increase (2.86 vs. 3.00 and 0.16 vs. 0.17, respectively). Moderate to strong correlations between bone adjusted muscle volume and weaker correlations between adipose tissue volumes and outcome parameters (pulmonary function, QoL and physical performance) were observed. Particularly after 6-month, bone adjusted muscle volume changes positively corresponded to improved outcomes (ΔForced expiratory volume in 1 s [FEV1], r = 0.440; ΔInspiratory vital capacity [IVC], r = 0.397; Δ6Minute walking distance [6MWD], r = 0.509 and ΔCOPD assessment test [CAT], r = -0.324; all p < 0.001). Group stratification by bone adjusted muscle volume changes revealed that groups with substantial muscle gain experienced a greater clinical benefit in pulmonary function improvements, QoL and physical performance (ΔFEV1%, 5.5 vs. 39.5; ΔIVC%, 4.3 vs. 28.4; Δ6MWDm, 14 vs. 110; ΔCATpts, -2 vs. -3.5 for groups with ΔMuscle, BAR% < -10 vs. > 10, respectively). BCA results among patients divided by the minimal clinically important difference for forced expiratory volume of the first second (FEV1) showed significant differences in bone-adjusted muscle and intramuscular adipose tissue (IMAT) volumes and their respective changes after 6 months (ΔMuscle, BAR% -5 vs. 3.4 and ΔIMAT, BAR% -0.62 vs. 0.60 for groups with ΔFEV1 ≤ 100 mL vs > 100 mL). Altered body composition, especially increased muscle volume, is associated with functional improvements in BLVR-treated patients.

Elexacaftor/tezacaftor/ivacaftor influences body composition in adults with cystic fibrosis: a fully automated CT-based analysis.

A poor nutritional status is associated with worse pulmonary function and survival in people with cystic fibrosis (pwCF). CF transmembrane conductance regulator modulators can improve pulmonary function and body weight, but more data is needed to evaluate its effects on body composition. In this retrospective study, a pre-trained deep-learning network was used to perform a fully automated body composition analysis on chest CTs from 66 adult pwCF before and after receiving elexacaftor/tezacaftor/ivacaftor (ETI) therapy. Muscle and adipose tissues were quantified and divided by bone volume to obtain body size-adjusted ratios. After receiving ETI therapy, marked increases were observed in all adipose tissue ratios among pwCF, including the total adipose tissue ratio (+ 46.21%, p < 0.001). In contrast, only small, but statistically significant increases of the muscle ratio were measured in the overall study population (+ 1.63%, p = 0.008). Study participants who were initially categorized as underweight experienced more pronounced effects on total adipose tissue ratio (p = 0.002), while gains in muscle ratio were equally distributed across BMI categories (p = 0.832). Our findings suggest that ETI therapy primarily affects adipose tissues, not muscle tissue, in adults with CF. These effects are primarily observed among pwCF who were initially underweight. Our findings may have implications for the future nutritional management of pwCF.

AI-Assisted X-ray Fracture Detection in Residency Training: Evaluation in Pediatric and Adult Trauma Patients.

Background: This study aimed to evaluate the impact of an AI-assisted fracture detection program on radiology residents' performance in pediatric and adult trauma patients and assess its implications for residency training. Methods: This study, conducted retrospectively, included 200 radiographs from participants aged 1 to 95 years (mean age: 40.7 ± 24.5 years), encompassing various body regions. Among these, 50% (100/200) displayed at least one fracture, totaling one hundred thirty-five fractures, assessed by four radiology residents with different experience levels. A machine learning algorithm was employed for fracture detection, and the ground truth was established by consensus among two experienced senior radiologists. Fracture detection accuracy, reporting time, and confidence were evaluated with and without AI support. Results: Radiology residents' sensitivity for fracture detection improved significantly with AI support (58% without AI vs. 77% with AI, p < 0.001), while specificity showed minor improvements (77% without AI vs. 79% with AI, p = 0.0653). AI stand-alone performance achieved a sensitivity of 93% with a specificity of 77%. AI support for fracture detection significantly reduced interpretation time for radiology residents by an average of approximately 2.6 s (p = 0.0156) and increased resident confidence in the findings (p = 0.0013). Conclusion: AI support significantly enhanced fracture detection sensitivity among radiology residents, particularly benefiting less experienced radiologists. It does not compromise specificity and reduces interpretation time, contributing to improved efficiency. This study underscores AI's potential in radiology, emphasizing its role in training and interpretation improvement.

Impact of CT and MRI in the diagnostic workup of malignant triton tumour-a monocentric analysis and review of the literature.

OBJECTIVES: Malignant triton tumours (MTTs) are rare but aggressive subtypes of malignant peripheral nerve sheath tumours (MPNSTs) with a high recurrence rate and 5-year survival of 14%. Systematic imaging data on MTTs are scarce and mainly based on single case reports. Therefore, we aimed to identify typical CT and MRI features to improve early diagnosis rates of this uncommon entity. METHODS: A systematic review on literature published until December 2022 on imaging characteristics of MTTs was performed. Based on that, we conducted a retrospective, monocentric analysis of patients with histopathologically proven MTTs from our department. Explorative data analysis was performed. RESULTS: Initially, 29 studies on 34 patients (31.42 ± 22.6 years, 12 female) were evaluated: Literature described primary MTTs as huge, lobulated tumours (108 ± 99.3 mm) with central necrosis (56% [19/34]), low T1w (81% [17/21]), high T2w signal (90% [19/21]) and inhomogeneous enhancement on MRI (54% [7/13]). Analysis of 16 patients (48.9 ± 13.8 years; 9 female) from our institution revealed comparable results: primary MTTs showed large, lobulated masses (118 mm ± 64.9) with necrotic areas (92% [11/12]). MRI revealed low T1w (100% [7/7]), high T2w signal (100% [7/7]) and inhomogeneous enhancement (86% [6/7]). Local recurrences and soft-tissue metastases mimicked these features, while nonsoft-tissue metastases appeared unspecific. CONCLUSIONS: MTTs show characteristic features on CT and MRI. However, these do not allow a reliable differentiation between MTTs and other MPNSTs based on imaging alone. Therefore, additional histopathological analysis is required. ADVANCES IN KNOWLEDGE: This largest published systematic analysis on MTT imaging revealed typical but unspecific imaging features that do not allow a reliable, imaging-based differentiation between MTTs and other MPNSTs. Hence, additional histopathological analysis remains essential.

The importance of educational tools and a new software solution for visualizing and quantifying report correction in radiology training.

A novel software, DiffTool, was developed in-house to keep track of changes made by board-certified radiologists to preliminary reports created by residents and evaluate its impact on radiological hands-on training. Before (t0) and after (t2-4) the deployment of the software, 18 residents (median age: 29 years; 33% female) completed a standardized questionnaire on professional training. At t2-4 the participants were also requested to respond to three additional questions to evaluate the software. Responses were recorded via a six-point Likert scale ranging from 1 ("strongly agree") to 6 ("strongly disagree"). Prior to the release of the software, 39% (7/18) of the residents strongly agreed with the statement that they manually tracked changes made by board-certified radiologists to each of their radiological reports while 61% were less inclined to agree with that statement. At t2-4, 61% (11/18) stated that they used DiffTool to track differences. Furthermore, we observed an increase from 33% (6/18) to 44% (8/18) of residents who agreed to the statement "I profit from every corrected report". The DiffTool was well accepted among residents with a regular user base of 72% (13/18), while 78% (14/18) considered it a relevant improvement to their training. The results of this study demonstrate the importance of providing a time-efficient way to analyze changes made to preliminary reports as an additive for professional training.

Fibroblast Activation Protein α-Directed Imaging and Therapy of Solitary Fibrous Tumor.

Fibroblast activation protein α (FAPα) is expressed at high levels in several types of tumors. Here, we report the expression pattern of FAPα in solitary fibrous tumor (SFT) and its potential use as a radiotheranostic target. Methods: We analyzed FAPα messenger RNA and protein expression in biopsy samples from SFT patients using immunohistochemistry and multiplexed immunofluorescence. Tracer uptake and detection efficacy were assessed in patients undergoing clinical 68Ga-FAPα inhibitor (FAPI)-46 PET,18F-FDG PET, and contrast-enhanced CT. 90Y-FAPI-46 radioligand therapy was offered to eligible patients with progressive SFT. Results: Among 813 patients and 126 tumor entities analyzed from the prospective observational MASTER program of the German Cancer Consortium, SFT (n = 34) had the highest median FAPα messenger RNA expression. Protein expression was confirmed in tumor biopsies from 29 of 38 SFT patients (76%) in an independent cohort. Most cases showed intermediate to high FAPα expression by immunohistochemistry (24/38 samples, 63%), which was located primarily on the tumor cell surface. Nineteen patients who underwent 68Ga-FAPI-46 PET imaging demonstrated significantly increased tumor uptake, with an SUVmax of 13.2 (interquartile range [IQR], 10.2), and an improved mean detection efficacy of 94.5% (SEM, 4.2%), as compared with 18F-FDG PET (SUVmax, 3.2 [IQR, 3.1]; detection efficacy, 77.3% [SEM, 5.5%]). Eleven patients received a total of 34 cycles (median, 3 cycles [IQR, 2 cycles]) of 90Y-FAPI-46 radioligand therapy, which resulted in disease control in 9 patients (82%). Median progression-free survival was 227 d (IQR, 220 d). Conclusion: FAPα is highly expressed by SFT and may serve as a target for imaging and therapy. Further studies are warranted to define the role of FAPα-directed theranostics in the care of SFT patients.

Changes in tumor-to-blood ratio as a prognostic marker for progression-free survival and overall survival in neuroendocrine tumor patients undergoing PRRT.

BACKGROUND: Historically, patient selection for peptide receptor radionuclide therapy (PRRT) has been performed by virtue of somatostatin receptor scintigraphy (SRS). In recent years, somatostatin receptor positron emission tomography (SSTR-PET) has gradually replaced SRS because of its improved diagnostic capacity, creating an unmet need for SSTR-PET-based selection criteria for PRRT. Tumor-to-blood ratio (TBR) measurements have shown high correlation with the net influx rate Ki, reflecting the tumor somatostatin receptor expression, to a higher degree than standardized uptake value (SUV) measurements. TBR may therefore predict treatment response to PRRT. In addition, changes in semiquantitative SSTR-PET parameters have been shown to predate morphological changes, making them a suitable metric for response assessment. METHODS: The institutional database of the Department of Nuclear Medicine (University Hospital Essen) was searched for NET patients undergoing ≥ 2 PRRT cycles with available baseline and follow-up SSTR-PET. Two blinded independent readers reported the occurrence of new lesions quantified tumor uptake of up to nine lesions per patient using SUV and TBR. The association between baseline TBR and changes in uptake/occurrence of new lesions with progression-free survival (PFS) and overall survival (OS) was tested by use of a Cox regression model and log-rank test. RESULTS: Patients with baseline TBR in the 1st quartile had a shorter PFS (14.4 months) than those in the 3rd (23.7 months; p = 0.03) and 4th (24.1 months; p = 0.02) quartile. Similarly, these patients had significantly shorter OS (32.5 months) than those with baseline TBR in the 2nd (41.8 months; p = 0.03), 3rd (69.2 months; p < 0.01), and 4th (42.7 months; p = 0.03) quartile. Baseline to follow-up increases in TBR were independently associated with shorter PFS when accounting for prognostic markers, e.g., RECIST response (hazard ratio = 2.91 [95%CI = 1.54-5.50]; p = 0.01). This was confirmed with regard to OS (hazard ratio = 1.64 [95%CI = 1.03-2.62]; p = 0.04). Changes in SUVmean were not associated with PFS or OS. CONCLUSIONS: Baseline TBR as well as changes in TBR were significantly associated with PFS and OS and may improve patient selection and morphological response assessment. Future trials need to assess the role of TBR for therapy monitoring also during PRRT and prospectively explore TBR as a predictive marker for patient selection.

68Ga-Labeled Fibroblast Activation Protein Inhibitor (68Ga-FAPI) PET for Pancreatic Adenocarcinoma: Data from the 68Ga-FAPI PET Observational Trial.

The fibroblast activation protein (FAP) is highly expressed on carcinoma-associated fibroblasts in the stroma of pancreatic cancer and thus is a promising target for imaging and therapy. Preliminary data on PET imaging with radiolabeled FAP inhibitors (FAPIs) demonstrate superior tumor detection. Here we assess the accuracy of FAP-directed PET in patients with pancreatic cancer. Methods: Of 64 patients with suspected or proven pancreatic cancer, 62 (97%) were included in the data analysis of the 68Ga-FAPI PET observational trial (NCT04571086). All of these patients underwent contrast-enhanced CT, and 38 patients additionally underwent 18F-FDG PET. The primary study endpoint was the association of 68Ga-FAPI PET uptake intensity and histopathologic FAP expression. Secondary endpoints were detection rate, diagnostic performance, interreader reproducibility, and change in management. Datasets were interpreted by 2 masked readers. Results: The primary endpoint was met: The association between 68Ga-FAPI SUVmax and histopathologic FAP expression was significant (Spearman r, 0.48; P = 0.04). For histopathology-validated lesions, 68Ga-FAPI PET showed high sensitivity and positive predictive values (PPVs) on per-patient (sensitivity, 100%; PPV, 96.3%) and per-region (sensitivity, 100%; PPV, 97.0%) bases. In a head-to-head comparison versus 18F-FDG or contrast-enhanced CT, 68Ga-FAPI detected more tumor on a per-lesion (84.7% vs. 46.5% vs. 52.9%), per-patient (97.4% vs. 73.7% vs. 92.1%), or per-region (32.6% vs. 18.8% vs. 23.7%) basis, respectively. 68Ga-FAPI PET readers showed substantial overall agreement on the basis of the Fleiss κ: primary κ, 0.77 (range, 0.66-0.88). Minor and major changes in clinical management occurred in 5 patients (8.4%) after 68Ga-FAPI PET. Conclusion: We confirmed an association of 68Ga-FAPI PET SUVmax and histopathologic FAP expression in pancreatic cancer patients. Additionally, we found high detection rate and diagnostic accuracy, superior to those of 18F-FDG PET/CT. 68Ga-FAPI might become a powerful diagnostic tool for pancreatic cancer work-up.

Current use of percutaneous image-guided tumor ablation for the therapy of liver tumors: lessons learned from the registry of the German Society for Interventional Radiology and Minimally Invasive Therapy (DeGIR) 2018-2022.

OBJECTIVES: Percutaneous image-guided tumor ablation of liver malignancies has become an indispensable therapeutic procedure. The aim of this evaluation of the prospectively managed multinational registry of the voluntary German Society for Interventional Radiology and Minimally Invasive Therapy (DeGIR) was to analyze its use, technical success, and complications in clinical practice. MATERIALS AND METHODS: All liver tumor ablations from 2018 to 2022 were included. Technical success was defined as complete ablation of the tumor with an ablative margin. RESULTS: A total of 7228 liver tumor ablations from 136 centers in Germany and Austria were analyzed. In total, 31.4% (2268/7228) of patients were female. Median age was 67 years (IQR 58-74 years). Microwave ablation (MWA) was performed in 65.1% (4703/7228), and radiofrequency ablation (RFA) in 32.7% (2361/7228). Of 5229 cases with reported tumor etiology, 60.3% (3152/5229) of ablations were performed for liver metastases and 37.3% (1950/5229) for hepatocellular carcinoma. The median lesion diameter was 19 mm (IQR 12-27 mm). In total, 91.8% (6636/7228) of ablations were technically successful. The rate of technically successful ablations was significantly higher in MWA (93.9%, 4417/4703) than in RFA (87.3%, 2061/2361) (p < 0.0001). The total complication rate was 3.0% (214/7228) and was significantly higher in MWA (4.0%, 189/4703) than in RFA (0.9%, 21/2361, p < 0.0001). Additional needle track ablation did not increase the rate of major complications significantly (24.8% (33/133) vs. 28.4% (23/81), p = 0.56)). CONCLUSION: MWA is the most frequent ablation method. Percutaneous image-guided liver tumor ablations have a high technical success rate, which is higher for MWA than RFA. The complication rate is generally low but is higher for MWA than RFA. CLINICAL RELEVANCE STATEMENT: Percutaneous image-guided liver ablation using microwave ablation and radiofrequency ablation are effective therapeutic procedures with low complication rates for the treatment of primary and secondary liver malignancies. KEY POINTS: • Percutaneous image-guided liver tumor ablations have a high technical success rate, which is higher for microwave ablation than radiofrequency ablation. • Microwave ablation is the most frequent ablation method ahead of radiofrequency ablation. • The complication rate is generally low but is higher for microwave ablation than radiofrequency ablation.

BOA: A CT-Based Body and Organ Analysis for Radiologists at the Point of Care.

PURPOSE: The study aimed to develop the open-source body and organ analysis (BOA), a comprehensive computed tomography (CT) image segmentation algorithm with a focus on workflow integration. METHODS: The BOA combines 2 segmentation algorithms: body composition analysis (BCA) and TotalSegmentator. The BCA was trained with the nnU-Net framework using a dataset including 300 CT examinations. The CTs were manually annotated with 11 semantic body regions: subcutaneous tissue, muscle, bone, abdominal cavity, thoracic cavity, glands, mediastinum, pericardium, breast implant, brain, and spinal cord. The models were trained using 5-fold cross-validation, and at inference time, an ensemble was used. Afterward, the segmentation efficiency was evaluated on a separate test set comprising 60 CT scans. In a postprocessing step, a tissue segmentation (muscle, subcutaneous adipose tissue, visceral adipose tissue, intermuscular adipose tissue, epicardial adipose tissue, and paracardial adipose tissue) is created by subclassifying the body regions. The BOA combines this algorithm and the open-source segmentation software TotalSegmentator to have an all-in-one comprehensive selection of segmentations. In addition, it integrates into clinical workflows as a DICOM node-triggered service using the open-source Orthanc research PACS (Picture Archiving and Communication System) server to make the automated segmentation algorithms available to clinicians. The BCA model's performance was evaluated using the Sørensen-Dice score. Finally, the segmentations from the 3 different tools (BCA, TotalSegmentator, and BOA) were compared by assessing the overall percentage of the segmented human body on a separate cohort of 150 whole-body CT scans. RESULTS: The results showed that the BCA outperformed the previous publication, achieving a higher Sørensen-Dice score for the previously existing classes, including subcutaneous tissue (0.971 vs 0.962), muscle (0.959 vs 0.933), abdominal cavity (0.983 vs 0.973), thoracic cavity (0.982 vs 0.965), bone (0.961 vs 0.942), and an overall good segmentation efficiency for newly introduced classes: brain (0.985), breast implant (0.943), glands (0.766), mediastinum (0.880), pericardium (0.964), and spinal cord (0.896). All in all, it achieved a 0.935 average Sørensen-Dice score, which is comparable to the one of the TotalSegmentator (0.94). The TotalSegmentator had a mean voxel body coverage of 31% ± 6%, whereas BCA had a coverage of 75% ± 6% and BOA achieved 93% ± 2%. CONCLUSIONS: The open-source BOA merges different segmentation algorithms with a focus on workflow integration through DICOM node integration, offering a comprehensive body segmentation in CT images with a high coverage of the body volume.

Correlation of the apparent diffusion coefficient with the standardized uptake value in meningioma of the skull plane using [68]Ga-DOTATOC PET/MRI.

PURPOSE: To evaluate a correlation between an MRI-specific marker for cellular density [apparent diffusion coefficient (ADC)] and the expression of Somatostatin Receptors (SSTR) in patients with meningioma of the skull plane and orbital space. METHODS: 68 Ga-DOTATOC PET/MR imaging was performed in 60 Patients with suspected or diagnosed meningiomas of the skull base and eye socket. Analysis of ADC values succeeded in 32 patients. ADC values (ADC mean and ADC min ) were analyzed using a polygonal region of interest. Tracer-uptake of target lesions was assessed according to corresponding maximal (SUV max ) and mean (SUV mean ) values. Correlations between assessed parameters were evaluated using the Pearson correlation coefficient. RESULTS: One out of 32 patients (3%) was diagnosed with lymphoma by histopathological examination and therefore excluded from further analysis. Median ADC mean amounted to 822 × 10 -5  mm²/s -1 (95% CI: 570-1497) and median ADC min was 493 × 10 -5 mm 2 /s -1 (95% CI: 162-783). There were no significant correlations between SUV max and ADC min (r = 0.60; P  = 0.76) or ADC mean (r = -0.52; P  = 0.79), respectively. However, Pearson's test showed a weak, inverse but insignificant correlation between ADC mean and SUV mean (r = -0.33; P  = 0.07). CONCLUSION: The presented data displays no relevant correlations between increased SSTR expression and cellularity in patients with meningioma of the skull base. SSTR-PET and DWI thus may offer complementary information on tumor characteristics of meningioma.

DOTATOC PET/CT imaging of a typical carcinoid tumor in a human ex-vivo perfused lung lobe.

The use of Isolated lung perfusion (ILP), combined with medical imaging modalities such as positron emission tomography-computed tomography (PET/CT), provides real-time visualization of tumors in ventilated and perfused vital lung tissue. This experiment intends to show the feasibility and benefits of using ILP combined with PET/CT imaging. Following lung surgery on a 49-year-old male, his left lower lobectomy specimen, which held a typical carcinoid tumor, was preserved on normothermic ILP. Gallium-68-Edotreotide ([68Ga]-DOTATOC) was administered into the ILP circuit, and dynamic emission data from PET/CT was acquired. ILP was carried out for 120 minutes. Near physiologic gas exchange and glucose metabolism were preserved throughout the experiment. The time activity curves (TAC) of 5 different volumes of interest (VOI) showed notable differences in tracer uptake over time. The peripheral area of the carcinoid exhibited delayed but high somatostatin receptor agonist uptake compared to the surrounding parenchyma and the intrapulmonary artery. However, the central area of the carcinoid showed very low [68Ga]-DOTATOC uptake. This experiment demonstrates the potential of ILP combined with PET/CT for kinetic modeling in experimental nuclear medicine imaging. By providing visualization of tracer uptake in perfused lung tissue, this model could potentially improve our understanding of tumor physiology and molecular imaging.

Evaluation of [68Ga]-DOTATOC PET/MRI in Patients with Meningioma of the Subcranial and Intraorbital Space.

Meningiomas are known to express somatostatin receptor (SSTR) type 2 to a high degree. Therefore, radiolabeled somatostatin analogs, such as DOTATOC, have been introduced for PET imaging of meningiomas. However, the benefit of hybrid SSTR PET/MRI is still debated. Here, we report our experience with [68Ga]-DOTATOC PET/MRI. Methods: PET/MRI was performed in 60 patients with suspected or diagnosed meningiomas of the skull plane and eye socket. Acquired datasets were reported by 2 independent readers regarding local tumor extent and signal characteristics. Histopathologic results and follow-up imaging served as the reference standard. SUVs of target lesions were analyzed according to the corresponding maximal tracer uptake. The diagnostic accuracy of PET/MRI and conventional MRI was determined independently and compared with the reference standard. Results: In total, 60 target lesions were identified, with 54 considered to be meningiomas according to the reference standard. Sensitivity and specificity of PET/MRI versus MRI alone were 95% versus 96% and 75% versus 66%, respectively. The McNemar test was not able to distinguish any differences between PET/MRI and the reference standard or MRI and the reference standard. No differences were found between the 2 modalities with respect to local infiltration. Conclusion: SSTR PET/MRI and MRI yielded similar accuracy for the detection of meningiomas of the skull base and intraorbital space. Here, sequential low-dose SSTR PET/CT might be helpful for the planning of radioligand therapy or radiotherapy.

Voxel-Based Dosimetry Predicts Hepatotoxicity in Hepatocellular Carcinoma Patients Undergoing Radioembolization with 90Y Glass Microspheres.

Personalized dosimetry holds promise to improve radioembolization treatment outcomes in hepatocellular carcinoma (HCC) patients. To this end, tolerance absorbed doses for nontumor liver tissue are assessed by calculating the mean absorbed dose to the whole nontumor liver tissue (AD-WNTLT), which may be limited by its neglect of nonuniform dose distribution. Thus, we analyzed whether voxel-based dosimetry could be more accurate in predicting hepatotoxicity in HCC patients undergoing radioembolization. Methods: In total, 176 HCC patients were available for this retrospective analysis; of these, 78 underwent partial- and 98 whole-liver treatment. Posttherapeutic changes in bilirubin were graded using the Common Terminology Criteria for Adverse Events. We performed voxel-based and multicompartment dosimetry using pretherapeutic 99mTc-labeled human serum albumin SPECT and contrast-enhanced CT/MRI and defined the following dosimetry parameters: AD-WNTLT; the nontumor liver tissue volume exposed to at least 20 Gy (V20), at least 30 Gy (V30), and at least 40 Gy (V40); and the threshold absorbed dose to the 20% (AD-20) and 30% (AD-30) of nontumor liver tissue with the lowest absorbed dose. Their impact on hepatotoxicity after 6 mo was analyzed using the area under the receiver-operating-characteristic curve; thresholds were identified using the Youden index. Results: The area under the curve for prediction of posttherapeutic grade 3+ increases in bilirubin was acceptable for V20 (0.77), V30 (0.78), and V40 (0.79), whereas it was low for AD-WNTLT (0.67). The predictive value could further be increased in the subanalysis of patients with whole-liver treatment, where a good discriminatory power was found for V20 (0.80), V30 (0.82), V40 (0.84), AD-20 (0.80), and AD-30 (0.82) and an acceptable discriminatory power was found for AD-WNTLT (0.63). The accuracies of V20 (P = 0.03), V30 (P = 0.009), V40 (P = 0.004), AD-20 (P = 0.04), and AD-30 (P = 0.02) were superior to that of AD-WNTLT but did not differ significantly from each other. The respective thresholds were 78% (V30), 72% (V40), and 43 Gy (AD-30). Statistical significance was not reached for partial-liver treatment. Conclusion: Voxel-based dosimetry may more accurately predict hepatotoxicity than multicompartment dosimetry in HCC patients undergoing radioembolization, which could enable dose escalation or deescalation with the intent to optimize treatment response. Our results indicate that a V40 of 72% may be particularly useful in whole-liver treatment. However, further research is warranted to validate these results.

Embolization of active arterial bleeding in COVID-19 patients: A multicenter study.

PURPOSE: The purpose of this study was to assess the efficacy of transarterial embolization in COVID-19 patients with an arterial bleeding and to investigate differences between various patient groups concerning survival. METHOD: We retrospectively reviewed COVID-19 patients undergoing transarterial embolization due to an arterial bleeding in a multicenter study from April 2020 to July 2022 and analyzed the technical success of embolization and survival rate. 30-day survival between various patient groups was analyzed. The Chi- square test and Fisher's exact test were used for testing association between the categorical variables. RESULTS: 53 COVID-19 patients (age: 57.3 ± 14.3 years, 37 male) received 66 angiographies due to an arterial bleeding. The initial embolization was technically successful in 98.1% (52/53). In 20.8% (11/53) of patients, additional embolization was necessary due to a new arterial bleeding. A majority of 58.5% (31/53) had a severe course of COVID-19 infection necessitating ECMO-therapy and 86.8% (46/53) of patients received anticoagulation. 30-day survival rate in patients with ECMO-therapy was significantly lower than without ECMO-therapy (45.2% vs. 86.4%, p = 0.004). Patients with anticoagulation did not have a lower 30-day survival rate than without anticoagulation (58.7% vs. 85.7%, p = 0.23). COVID-19 patients with ECMO-therapy developed more frequently a re-bleeding after embolization than non-ECMO-patients (32.3% vs. 4.5%, p = 0.02). CONCLUSIONS: Transarterial embolization is a feasible, safe, and effective procedure in COVID-19 patients with arterial bleeding. ECMO-patients have a lower 30-day survival rate than non-ECMO-patients and have an increased risk for re-bleeding. Treatment with anticoagulation could not be identified as a risk factor for higher mortality.

68Ga-FAPI PET/CT Interobserver Agreement on Tumor Assessment: An International Multicenter Prospective Study.

68Ga-fibroblast activation protein inhibitors (FAPIs) are promising radiotracers for cancer imaging, with emerging data in the recent years. Nonetheless, the interobserver agreement on 68Ga-FAPI PET/CT study interpretations in cancer patients remains poorly understood. Methods: 68Ga-FAPI PET/CT was performed on 50 patients with various tumor entities (sarcoma [n = 10], colorectal cancer [n = 10], pancreatic adenocarcinoma [n = 10], genitourinary cancer [n = 10], and other types of cancer [n = 10]). Fifteen masked observers reviewed and interpreted the images using a standardized approach for local, local nodal, and metastatic involvement. Observers were grouped by experience as having a low (<30 prior 68Ga-FAPI PET/CT studies; n = 5), intermediate (30-300 studies; n = 5), or high level of experience (>300 studies; n = 5). Two independent readers with a high level of experience and unmasked to clinical information, histopathology, tumor markers, and follow-up imaging (CT/MRI or PET/CT) served as the standard of reference (SOR). Observer groups were compared by overall agreement (percentage of patients matching SOR) and Fleiss κ with mean and corresponding 95% CI. We defined acceptable agreement as a κ value of at least 0.6 (substantial or higher) and acceptable accuracy as at least 80%. Results: Highly experienced observers agreed substantially on all categories (primary tumor: κ = 0.71; 95% CI, 0.71-0.71; local nodal involvement: κ = 0.62; 95% CI, 0.61-0.62; distant metastasis: κ = 0.75; 95% CI, 0.75-0.75), whereas observers with intermediate experience showed substantial agreement on primary tumor (κ = 0.73; 95% CI, 0.73-0.73) and distant metastasis (κ = 0.65; 95% CI, 0.65-0.65) but moderate agreement on local nodal stages (κ = 0.55; 95% CI, 0.55-0.55). Observers with low experience had moderate agreement on all categories (primary tumor: κ = 0.57; 95% CI, 0.57-0.58; local nodal involvement: κ = 0.51; 95% CI, 0.51-0.52; distant metastasis: κ = 0.54; 95% CI, 0.53-0.54). Compared with SOR, the accuracy for readers with high, intermediate, and low experience was 85%, 83%, and 78%, respectively. In summary, only highly experienced readers showed substantial agreement and a diagnostic accuracy of at least 80% in all categories. Conclusion: The interpretation of 68Ga-FAPI PET/CT for cancer imaging had substantial reproducibility and accuracy among highly experienced observers only, especially for local nodal and metastatic assessments. Therefore, for accurate interpretation of different tumor entities and pitfalls, we recommend training or experience with at least 300 representative scans for future clinical readers.

Individualized scan protocols for CT angiography: an animal study for contrast media or radiation dose optimization.

BACKGROUND: We investigated about optimization of contrast media (CM) dose or radiation dose in thoracoabdominal computed tomography angiography (CTA) by automated tube voltage selection (ATVS) system configuration and CM protocol adaption. METHODS: In six minipigs, CTA-optimized protocols were evaluated regarding objective (contrast-to-noise ratio, CNR) and subjective (6 criteria assessed by Likert scale) image quality. Scan parameters were automatically adapted by the ATVS system operating at 90-kV semi-mode and configured for standard, CM saving, or radiation dose saving (image task, quality settings). Injection protocols (dose, flow rate) were adapted manually. This approach was tested for normal and simulated obese conditions. RESULTS: Radiation exposure (volume-weighted CT dose index) for normal (obese) conditions was 2.4 ± 0.7 (5.0 ± 0.7) mGy (standard), 4.3 ± 1.1 (9.0 ± 1.3) mGy (CM reduced), and 1.7 ± 0.5 (3.5 ± 0.5) mGy (radiation reduced). The respective CM doses for normal (obese) settings were 210 (240) mgI/kg, 155 (177) mgI/kg, and 252 (288) mgI/kg. No significant differences in CNR (normal; obese) were observed between standard (17.8 ± 3.0; 19.2 ± 4.0), CM-reduced (18.2 ± 3.3; 20.5 ± 4.9), and radiation-saving CTAs (16.0 ± 3.4; 18.4 ± 4.1). Subjective analysis showed similar values for optimized and standard CTAs. Only the parameter diagnostic acceptability was significantly lower for radiation-saving CTA compared to the standard CTA. CONCLUSIONS: The CM dose (-26%) or radiation dose (-30%) for thoracoabdominal CTA can be reduced while maintaining objective and subjective image quality, demonstrating the feasibility of the personalization of CTA scan protocols. KEY POINTS: • Computed tomography angiography protocols could be adapted to individual patient requirements using an automated tube voltage selection system combined with adjusted contrast media injection. • Using an adapted automated tube voltage selection system, a contrast media dose reduction (-26%) or radiation dose reduction (-30%) could be possible.