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OBJECTIVES The present study investigates outcomes one month after implanting pigs with a novel mitral valved stent. METHODS A novel nitinol stent custom designed for this study included a bovine pericardial valve. Six pigs received a valved stent into the mitral position by means of the transapical implantation technique. Afterwards, haemodynamic stability and valve function were assessed, immediately after implantation (n = 6), 4 weeks (n = 4) and 8 weeks (n = 1) thereafter using transoesophageal echocardiography (TEE), ventriculography and cardiac computed tomography (CT). Four of 6 surviving pigs were sacrificed at 4 weeks after implantation and one at 8 weeks thereafter. RESULTS Optimal deployment and positioning were obtained in all but one animal. This animal died of unrecognized imperfect valved stent positioning after 4 days. The average mean gradient across the new valves and the left ventricular outflow tract (LVOT) were small. Mild regurgitation developed after valved stent deployment in one of six animals just after 1 h, and in none thereafter. All animals exhibited normal haemodynamics after mitral valved stent implantation, and stability was maintained throughout the monitoring period. Migration, embolization and paravalvular leakage were not evident in the remaining animals after 4 and 8 weeks. Gross evaluation revealed that 50–70% of the atrial element was covered by tissue growth at 4 weeks/8 weeks. CONCLUSIONS This study demonstrates adequate deployment and anchorage of a unique, repositionable mitral valved stent. A good valve function was revealed in animals observed for 4 weeks and in one pig after 8 weeks. [ABSTRACT FROM AUTHOR]

Background: Online adaptive MR-guided radiotherapy allows for the reduction of safety margins in dose escalated treatment of rectal tumors. With the use of smaller margins, precise tumor delineation becomes more critical. In the present study we investigated the impact of rectal ultrasound gel filling on interobserver variability in delineation of primary rectal tumor volumes., Methods: Six patients with locally advanced rectal cancer were scanned on a 1.5 T MRI-Linac without (MRI&#95;e) and with application of 100 cc of ultrasound gel transanally (MRI&#95;f). Eight international radiation oncologists expert in the treatment of gastrointestinal cancers delineated the gross tumor volume (GTV) on both MRI scans. MRI&#95;f scans were provided to the participating centers after MRI&#95;e scans had been returned. Interobserver variability was analyzed by either comparing the observers' delineations with a reference delineation (approach 1) and by building all possible pairs between observers (approach 2). Dice Similarity Index (DICE) and 95 % Hausdorff-Distance (95 %HD) were calculated., Results: Rectal ultrasound gel filling was well tolerated by all patients. Overall, interobserver agreement was superior in MRI&#95;f scans based on median DICE (0.81 vs 0.74, p < 0.005 for approach 1 and 0.76 vs 0.64, p < 0.0001 for approach 2) and 95 %HD (6.9 mm vs 4.2 mm for approach 1, p = 0.04 and 8.9 mm vs 6.1 mm, p = 0.04 for approach 2). Delineated median tumor volumes and inter-quartile ranges were 26.99 cc [18.01-50.34 cc] in MRI&#95;e and 44.20 [19.72-61.59 cc] in MRI&#95;f scans respectively, p = 0.012., Conclusions: Although limited by the small number of patients, in this study the application of rectal ultrasound gel resulted in higher interobserver agreement in rectal GTV delineation. The endorectal gel filling might be a useful tool for future dose escalation strategies., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The Department of Radiation Oncology Tübingen (SB, CG, DT, DZ) receives within the frame of research agreements financial and technical support as well as sponsoring for travels and scientific symposia from: Elekta AB (Stockholm, Sweden), Philips GmbH, Siemens, PTW Freiburg Physikalisch-Technische Werkstätten Dr. Pychlau GmbH. SB: Honoraria for talks by Elekta. AT: Travel and speaking funding by Elekta. from Elekta. PBR is supported by an NIH/NCI grant (K08CA255574), the Memorial Sloan Kettering Cancer Center, an NIH Loan Repayment Program (LRP) award. PBR and RS are supported in part by a National Institutes of Health/National Cancer Institute (NIH/NCI) Memorial Sloan Kettering Cancer Center (MSK) Support Grant (P30 CA008748)., (© 2022 The Author(s).)