ObjectiveThe purpose of this prospective multicenter study was to assess the safety and technical feasibility of volumetric Magnetic Resonance-guided High Intensity Focused Ultrasound (MR-HIFU) ablation for treatment of patients with symptomatic uterine fibroids.MethodsThirty-three patients with 36 fibroids were treated with volumetric MR-HIFU ablation. Treatment capability and technical feasibility were assessed by comparison of the Non-Perfused Volumes (NPVs) with MR thermal dose predicted treatment volumes. Safety was determined by evaluation of complications or adverse events and unintended lesions. Secondary endpoints were pain and discomfort scores, recovery time and length of hospital stay.ResultsThe mean NPV calculated as a percentage of the total fibroid volume was 21.7%. Correlation between the predicted treatment volumes and NPVs was found to be very strong, with a correlation coefficient r of 0.87. All patients tolerated the treatment well and were treated on an outpatient basis. No serious adverse events were reported and recovery time to normal activities was 2.3 ± 1.8 days.ConclusionThis prospective multicenter study proved that volumetric MR-HIFU is safe and technically feasible for the treatment of symptomatic uterine fibroids.Key Points• Magnetic-resonance-guided high intensity focused ultrasound allows non-invasive treatment of uterine fibroids.• Volumetric feedback ablation is a novel technology that allows larger treatment volumes• MR-guided ultrasound ablation of uterine fibroids appears safe using volumetric feedback

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SiO 2 -like thin films were deposited at low temperatures ͑Ͻ50°C͒ by atmospheric-pressure plasma-enhanced chemical vapor deposition using a pin-to-plate-type dielectric barrier discharge with a gas mixture containing hexamethyldisilazane ͑HMDS͒/Ar/O 2 . The deposition rate increased with increasing concentration of HMDS in the gas mixture. However, a powdery film with Si-OH bonding, high roughness, and low transmittance was obtained, which was attributed to the enhanced homogeneous reaction with increasing HMDS. The increase in O 2 flow rate at a fixed HMDS flow rate increased the reaction rate of the remaining HMDS on the substrate surface, which resulted in an increase in deposition rate until the remaining HMDS had completely reacted. An increase in the oxygen flow rate also increased the surface roughness and decreased the optical transmittance slightly, possibly due to the formation of small SiO 2 particles in the gas phase during the dissociation of the gas mixture under high-oxygen-percentage conditions. At the optimum condition of HMDS ͑15 sccm͒/O 2 ͑300 sccm͒/Ar ͑2 slm͒, smooth SiO 2 -like thin films with a transmittance Ͼ95% could be obtained with a deposition rate of approximately 21 nm/min.

Silicon oxide thin films were deposited using a modified, pin-to-plate, dielectric barrier discharge system with polydimethylsiloxane ͑PDMS͒, bubbled by He/O 2 gas mixtures at atmospheric pressure and a temperature of less than 50°C. Increasing PDMS flow rate in the gas mixture increased the deposition rate, but also increased the surface roughness due to the formation of particles in the gas phase as a result of increased PDMS and silanol groups, leading to incomplete decomposition or oxidation of PDMS. The increase in the ratio of oxygen flow rate to PDMS flow rate decreased the surface roughness with increasing deposition rate due to the efficient oxidation of PDMS. However, when the oxygen flow rate was raised above 1 slm, due to the increased oxidation of PDMS in the gas phase and the decreased PDMS dissociation by the decreased plasma density, the surface roughness was again increased with decreasing deposition rate. At the gas mixture of 9 slm PDMS/He and 1 slm oxygen, a smooth, SiO 2 -like thin film was obtained at a deposition rate of 12 nm/min.