A microscopic oxygen transport model for ultra-high dose rate radiotherapy in vivo: The impact of physiological conditions on FLASH effect

Objective: To evaluate, in patients who underwent Fallopian-tube sterilization by hysteroscopic insertion of an Essure (R) device, the feasibility and accuracy of three-dimensional (3D) transvaginal sonography (TVS) to check the position of the device and 3D hysterosalpingo-foam sonography (3D-HyFoSy) using contrast-enhanced gel foam to assess consequent tubal occlusion. Methods: This was a prospective multicenter study conducted from June 2012 to July 2014 in four Italian centers, which included 50 women who underwent hysteroscopic Essure microinsert placement in a total of 95 Fallopian tubes. Placement of the microinserts was performed in an outpatient setting following standard procedure recommendations. All patients underwent transvaginal 3D-HyFoSy and hysterosalpingography (HSG) approximately 12-14 weeks after the procedure. The position of the devices was first checked on 3D-TVS and classified according to specific criteria (Positions A, B, C and D). Then, 3D-HyFoSy with ExEm (R) gel foam as the ultrasound contrast agent was performed to confirm tubal occlusion by the absence of contrast agent within the tubes and/or around the ovaries. To evaluate the feasibility of 3D-HyFoSy, consecutive volume acquisitions were performed while injecting the gel foam. After sonographic evaluation, women underwent HSG to assess the success of sterilization, as standard methodology. Side effects and pain evoked during and after 3D-HyFoSy and HSG were evaluated using a numeric pain rating scale. Results: On 3D-TVS, 10 devices (10.5%) were in Position A, two (2.1%) in Position B, 59 (62.1%) in Position C and 24 (25.3%) in Position D. During 3D-HyFoSy, tubal occlusion was observed in 89 of 95 tubes (93.7%). In the six cases in which the passage of the contrast was observed, one device (16.7%) was in Position B, one device (16.7%) in Position D and four devices (66.7%) were found to lie in Position C. Tubal patency was confirmed at HSG with a concordance rate of 100%. The mean pain score associated with 3D-HyFoSy was significantly lower than that on HSG. Conclusions: 3D-TVS with HyFoSy allows accurate assessment of the position of Essure microinserts and tubal occlusion. It can be considered a safe, reliable, non-invasive alternative to HSG. Copyright (c) 2017 ISUOG. Published by John Wiley & Sons Ltd.