RPS 415 - Technical innovations in vascular imaging

Author Block: S. Gruendemann, T. Frenzel, J. Lohrke, J. Boyken, G. Jost, M. Berger, H-F. Ulbrich, H. Pietsch; Berlin/DE
Purpose: Gadoquatrane is a tetrameric extracellular macrocyclic gadolinium-based contrast agent (GBCA) with a T1 relaxivity of 11.8 L/(mmol Gd*s) at 1.41 T in human plasma, which has been submitted for regulatory approval in several countries. This study evaluated its stability in comparison with approved macrocyclic GBCAs in vitro and in vivo.
Methods or Background: All assays were conducted at equimolar Gd concentrations. Dissociation kinetics were measured for gadoquatrane, gadoteridol, gadobutrol, gadoterate, and gadopiclenol at pH 1.2 and 37°C using a complexometric assay. Stability in human plasma at pH 7.4 and 37°C was analyzed by ion exchange chromatography with ICP-MS. Rats received a single injection of gadoquatrane, gadobutrol, or gadopiclenol (0.6 mmol Gd/kg; human equivalent 0.1 mmol Gd/kg), and Gd distribution in bone was quantified by laser ablation ICP-MS one week later.
Results or Findings: At pH 1.2, dissociation half-lives were 28.6 days (gadoquatrane), 14.2 days (gadopiclenol), 2.7 days (gadoterate), 14.1 h (gadobutrol), and 2.2 h (gadoteridol). After 15 days in plasma (pH 7.4), no detectable Gd release was observed for gadoquatrane or gadoterate, while gadobutrol, gadoteridol, and gadopiclenol released 0.12%, 0.20%, and 0.20%, respectively. In rats, bone marrow Gd levels were similar across compounds (2.3-3.0 nmol/g). In epiphysis, concentrations were 1.2 nmol/g for gadoquatrane and gadobutrol, and 2.2 nmol/g for gadopiclenol. In diaphysis, levels were 0.5, 1.0, and 2.7 nmol/g, respectively. Elemental imaging showed lowest Gd in mineralized bone for gadoquatrane (<1 nmol/g) compared to gadobutrol and gadopiclenol.
Conclusion: Gadoquatrane demonstrated the highest kinetic inertness under acidic conditions and no measurable Gd release under physiological conditions in plasma. Its high stability was supported by very low Gd concentrations in mineralized bone in rats.
Limitations: These preclinical data do not allow direct conclusions regarding safety in humans.
Funding for this study: None
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Author Block: G. Jost, J. Boyken, J. Lohrke, S. Gruendemann, H. Pietsch; Berlin/DE
Purpose: There is ongoing scientific research on the presence of gadolinium (Gd) in bones after administration of Gd-based contrast agents (GBCAs). Gadoquatrane is a novel, macrocyclic GBCA with significantly higher r1-relaxivity, enabling MRI at reduced Gd dose. Gadoquatrane is in clinical development and was recently investigated in phase III studies at a dose of 0.04 mmol Gd/kg. Our study evaluates the presence of Gd in rat femurs compared to standard doses of gadopiclenol and gadobutrol.
Methods or Background: Rats (Wistar-Han, n=40 per GBCA) received a single intravenous injection of gadoquatrane (0.24 mmolGd/kg), gadopiclenol (0.3 mmolGd/kg) or gadobutrol (0.6 mmolGd/kg), representing human doses of 0.04, 0.05 and 0.1 mmol Gd/kg, respectively. After a treatment-free period of 1,4,22 and 52 weeks the Gd concentrations of the dissected femur (n=10 rats) were measured by inductively coupled plasma mass spectrometry (ICP-MS) and laser-ablation ICP-MS imaging (LA-ICP-MS).
Results or Findings: The Gd concentrations in bone epiphysis and diaphysis were comparable after administration of gadobutrol and gadopiclenol, whereas 2-to 6-fold lower concentrations were observed after injection of gadoquatrane. All GBCAs showed a limited Gd wash-out over the one-year follow up. In bone diaphysis the Gd concentration (geometric mean in nmol/g) after 1 and 52 weeks was 0.2±1.4 and 0.2±1.3 (gadoquatrane), 1.0±1.9 and 0.6±1.9 (gadopiclenol), 0.6±1.8 and 0.5±1.2 (gadobutrol). LA-ICP-MS imaging revealed different Gd distribution patterns. A local accumulation of Gd in the cortical bone was present after injection of gadopiclenol, which was barely visible after injection of gadobutrol. No local accumulation was detected for gadoquatrane.
Conclusion: The presence and distribution of Gd in the rat femur after a single injection of human equivalent clinical Gd doses differ among the three GBCAs. For gadoquatrane considerably lower Gd concentrations without local accumulations were detected.
Limitations: Preclinical study
Funding for this study: None
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Author Block: F. Wegner¹, M. R. Meyer², V. Gesché³, P. Borm⁴, A. Dell¹, G. Männel¹, D. Wendt¹, T. Friedrich¹, M. M. Sieren¹; ¹Lübeck/DE, ²Duisburg/DE, ³Aachen/DE, ⁴Düsseldorf/DE
Purpose: Commercially available endovascular stents are typically manufactured from metals. Due to their ferromagnetic properties, these devices can cause significant imaging artefacts, potentially limiting follow-up assessments with MRI and posing challenges for future MRI-guided EVAR procedures. The aim of this study was to develop a non-metallic aortic stent graft and evaluate its imaging characteristics in MRI.
Methods or Background: The stent struts were printed in a Z-shaped configuration using a custom-built 3D-printer with PEEK polymer filaments. The printer employed a rotational principle to apply the polymer onto a tubular graft textile. The stent graft was placed via a tube of 20 mm in diameter in a 3D-printed aortic phantom (material: Vero/Agilus, Shore 70A). The phantom was filled with gadolinium-based contrast agent (dilution 1:200) and subsequently imaged using a clinical MRI-scanner. To evaluate potential stent artefacts, the SNRs inside the stent and outside the stent were calculated. The stent strut thickness displayed on MR-images was measured at six locations and averaged.
Results or Findings: The rotational printing process enabled a stable connection between the stent struts and the textile. The resulting stent measured 30 mm in outer diameter and 100 mm in length. The strut thickness was measured by a caliper to be 1.6 mm. After the placement in the phantom, the stent fully expanded and showed no macroscopic loss of integrity. The stent struts were clearly delineable in MRI with a measured strut thickness of 1.7 ± 0.1 mm. The SNR inside the stent was 86.4 and outside 88.1, indicating no relevant stent-induced artefacts.
Conclusion: A non-metallic stent graft can be successfully manufactured using a rotational 3D-printing process with PEEK polymer, enabling artefact-free stent imaging in MRI.
Limitations: Only static measurements have been performed.
Funding for this study: Federal Ministry of Education and Research (BMBF), grant number 13GW0608F
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Author Block: P. Elfers¹, K. Lüdtke-Buzug², A. Malhotra², J. Ackers², J. C. Engster², D. Melenberg², M. Ahlborg², T. Friedrich², F. Wegner¹; ¹Lübeck/DE, ²Luebeck/DE
Purpose: Magnetic Particle Imaging (MPI) is a preclinical imaging modality on the verge to first human studies. It is based on the real-time visualisation of magnetic nanoparticles (MNPs). MPI is particularly well suited for cardiovascular imaging and enables artefact-free imaging of stent lumina. To visualise stents during MPI-guided interventions and to prevent interferences during follow-up examinations, a bioresorbable coating is required that degrades after a defined period. The aim of this work was to develop a coating based on polylactic acid (PLA) and MNPs to make stents temporarily visible in MPI.
Methods or Background: Glass capillaries were coated with a PLA-MNP-mixture by dip-coating. The degradation of the coating was investigated in a static water bath experiment at 37 °C. For this purpose, each sample was stored individually in a glass vial filled with isotonic saline solution. Ten different exposure durations (one hour to 28 days) were investigated and the samples were removed for analysis at the respective time. Before and after the water bath, the samples were dried, weighed, their MPI signal was measured, and their morphology was examined by using micro-CT.
Results or Findings: A continuous mass reduction of the markers was observed after exposure to the water bath (approx. 6 % after one hour, approx. 90 % after 28 days). Micro-CT showed only a slight volume decrease, whereas cavities formed inside the markers with increasing exposure time. A detectable MPI signal was present throughout the entire observation period.
Conclusion: PLA seems to be a suitable polymer for degradable stent markers. The observed properties provide a promising basis for future applications of MPI in cardiovascular and periinterventional imaging.
Limitations: The samples were investigated under static conditions only. Flow experiments are required to transfer the results.
Funding for this study: This work was supported in part by the Clinician Scientist Program of the University of Lübeck under Grant CS10-2021. The Fraunhofer IMTE and this work are supported by the EU, the State Schleswig-Holstein, Germany, and by Internal Programs (Grants 12420002/LPWE1.1.1/1536, 12524009/LPW21L/2.2/262 and 139–600251).
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Author Block: P. Osztrogonacz, J. Csőre, A. Szentiványi, Á. Bérczi, A. Hüttl, C. Csobay-Novák; Budapest/HU
Purpose: During physician-modified endograft (PMEG) preparation, reloading the stent graft into its delivery sheath is a time-sensitive step. Traditionally, this is performed using the tourniquet (T) technique. At our quaternary aortic referral center, valve stent crimper (C) has emerged as a potential alternative, offering a controlled and possibly more reproducible method.
Our study aimed to compare the C and T techniques in terms of reloading time.
Methods or Background: A Medtronic Valiant 38x200mm thoracic stent graft was reloaded a total of 18 times in a bench-top setting using either the T-technique (n=9) or the C-technique (n=9). Reloading times were recorded in minutes. Statistical analysis was performed using the Mann–Whitney U test to compare reloading times between groups. Results are reported in median (interquartile ranges (IQR)).
Results or Findings: The C-group demonstrated significantly faster reloading times, with a median time of 3.98 minutes (3.27–5.23), compared to 11.48 minutes (8.82–17.35) in the T-group (p = .001). The C group also exhibited narrower variability, suggesting improved reproducibility.
Conclusion: The crimper-technique offers a faster and more consistent method for thoracic stent graft reloading when compared to the traditional tourniquet technique. Its use may improve procedural efficiency and reproducibility in complex endovascular aortic aneurysm repair.
Limitations: Bench-top design, single stent graft type assessed, sample size may not detect rare occurrences of infolding / device failure
Funding for this study: None.
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Author Block: Y. Lin, S. Xie; Beijing/CN
Purpose: To develop, externally test, and evaluate clinical acceptability of a deep learning (DL) segmentation model of pulmonary vessels for detecting chronic thromboembolic pulmonary hypertension (CTEPH) at CT pulmonary angiography (CTPA).
Methods or Background: A multicenter, retrospective study was conducted involving 621 consecutive patients who underwent right heart catheterization (RHC), including individuals with confirmed CTEPH, CTED, and normal controls. Among them, 503 patients were assigned to the model development and internal test cohort, and the remaining 118 formed the external validation cohort.
Using CTPA, the pulmonary vasculature was reconstructed via a DL method to separate arteries from veins and compute vascular volumes based on cross-sectional area (CSA) and tortuosity for each branch. Statistically significant features were selected to develop the segmentation model. Diagnostic performance was evaluated using AUC, and the correlation between predicted and actual mean pulmonary arterial pressure (mPAP) was assessed across two institutions.
Results or Findings: The CTEPH cohort in the training set showed significantly larger total vessel volume, large vessel volume, total arterial volume, and greater arterial and venous tortuosity compared to both the CTED and control cohorts (all P < 0.001). Seventeen features were selected to develop a segmentation model, which demonstrated excellent diagnostic performance for identifying CTEPH using RHC results as the gold standard. The model achieved high AUC values (0.96–0.99) in both the training and internal test sets, and maintained strong accuracy in external validation. Additionally, predicted mPAP showed good agreement with real mPAP across two institutions (R² = 0.91 and 0.77, respectively).
Conclusion: Automated quantification methods using CT imaging can provide a imaging marker for identification of CTEPH and CTED.
Limitations: The findings are limited by a small sample size and multiple comparisons, which increased the risk of false-positive results.
Funding for this study: Beijing Natural Science Foundation
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: This project was approved by the Ethics Committee of China-Japan Friendship Hospital

Author Block: J. Csőre¹, A. Crichton², E. Pomozi², M. Drake², P. Haddad², J. Lamichhane², A. B. Lumsden², T. L. Roy²; ¹Budapest/HU, ²Houston, TX/US
Purpose: Chronic limb-threatening ischemia (CLTI) is often linked to chronic kidney disease (CKD), making vascular imaging in this population challenging. Digital subtraction angiography (DSA) remains the diagnostic reference standard but is invasive and requires iodinated contrast. Quiescent Interval Single Shot (QISS) MRI is a newer non-contrast-enhanced method that mitigates these risks. This study aimed to determine whether QISS MRI identifies a greater number of patent arterial segments than DSA, and whether this advantage is most pronounced in patients with advanced CKD (stages 4/5).
Methods or Background: Patients with CLTI who underwent both QISS MRI and DSA were included. Popliteal and infrapopliteal arteries were classified as patent or occluded across three sub-segments (e.g., AT1=proximal, AT2=mid, AT3=distal). Two blinded reviewers independently evaluated all images. Participants were stratified by GFR into <30, 30-59, ≥60 mL/min/1.73 m² groups. Primary outcome was the proportion of patent arterial segments identified by QISS compared to DSA across these GFR categories. Secondary outcomes included TASC and infrapopliteal GLASS score changes between modalities.
Results or Findings: Among 57 patients (752 vessel segments), QISS MRI demonstrated a significantly higher proportion of patent segments compared to DSA (67.2% vs 57.3%, p<0.001). Differences were significant in the <30 and ≥60 GFR groups, but not in the 30-59 group. TASC and GLASS scores were significantly downgraded using QISS MRI (mean TASC 2.2 vs 2.3, p=0.049; GLASS 2.6 vs 2.2, p<0.001).
Conclusion: QISS MRI identifies more patent vessel segments than DSA, especially in patients with advanced renal dysfunction. As earlier studies using older non-contrast MR techniques have shown comparable outcomes in bypasses to arteries visible only on MRI but not on DSA after three years, these results further support incorporating QISS MRI into routine limb-salvage assessment protocols.
Limitations: Single-center design, modest sample size
Funding for this study: Jerold B. Katz Academy of Translational Science under project number 15790002 (recipient's name: Trisha Roy), the American Heart Association Transformational Award under project ID 17590004 (recipient's name: Trisha Roy), and the National Institutes of Health Research Project grant (R01) under award number R01HL174587 (recipient's name: Trisha Roy).
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: Study ID 15790002