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Traditional Linear Accelerators
Published in W. P. M. Mayles, A. E. Nahum, J.-C. Rosenwald, Handbook of Radiotherapy Physics, 2021
The transmission waveguides in the microwave radiation system are filled with a dielectric gas. The most common gas for this purpose is sulphur hexafluoride (SF6). The gas pressure system is sealed but can be topped up from a pressurised cylinder of liquid gas, permanently installed in the linac. The sealed system usually operates with a pressure of around 25 psi.* A pressure relief valve is essential to ensure that the pressure does not exceed ~35 psi, which could damage the RF-vacuum ceramic windows. Because of minor leaks within the gas pressure system, the pressure should be checked daily and if necessary, topped up from the cylinder. Sulphur hexafluoride is not toxic but is a heavier-than-air asphyxiant. Precautions should therefore be taken if the cylinder leaks.
Percutaneous Transluminal Septal Myocardial Ablation in Hypertrophic Cardiomyopathy
Published in Srilakshmi M. Adhyapak, V. Rao Parachuri, Hypertrophic Cardiomyopathy, 2020
Anene C. Ukaigwe, Paul Sorajja
After this, through a 3 cc syringe, echo contrast is injected through the same OTW balloon under echocardiographic guidance. Any of the commercially available echo contrast agents can be used (e.g., Definity [Perflutren Lipid Microspheres], Lantheus Medical Imaging Billerica, MA; Optison [Perflutren Protein Type A microspheres] General Electric Company, CT; Lumason [sulfur hexafluoride lipid-type A microspheres], Bracco Diagnostics Inc., Monroe Township, NJ). The echo contrast should be diluted with saline to optimize myocardial opacification and minimize attenuation. The echocontrast should be injected slowly. Fast injections causes the echo contrast to fill the left ventricular cavity and may limit visualization. The echocardiogram is assessed to ensure that the target infarct area is the area of maximum flow acceleration in the LVOT in the area of SAM–septal contact. Other areas should be assessed to ensure that the non-target myocardium is not enhanced by echo contrast, especially the RV, papillary muscles, inferior wall, and anterior wall.
Pars plana vitrectomy for diabetic macular edema associated with posterior hyaloidal traction
Published in A Peyman MD Gholam, A Meffert MD Stephen, D Conway MD FACS Mandi, Chiasson Trisha, Vitreoretinal Surgical Techniques, 2019
Sophie J Bakri, Peter K Kaiser, Hilel Lewis
After removing the remaining vitreous, indirect ophthalmoscopy and scleral depression should be performed on the fluid-filled eye to identify any iatrogenic breaks. If a retinal break is identified, it should either be treated with one application of cryotherapy or encircled with three rows of endolaser treatment. A complete air–fluid exchange is then performed using the soft-tipped extrusion cannula and endoilluminator. This is followed by a gas–air exchange using a long-acting gas. We usually use nonexpansile concentrations of 10–20% sulfur hexafluoride (SF6) produced by mixing the gas with filtered air. If no iatrogenic breaks or macular holes are identified, an air–fluid exchange is not necessary. The patient is then asked to maintain a prone position for 7–14 days (in a phakic patient), or as necessary to tamponade the retinal breaks.
Changes in cardiac output, rhythm regularity, and symptom severity after electrical cardioversion of atrial fibrillation
Published in Scandinavian Cardiovascular Journal, 2023
Sofia Klavebäck, Helga Skúladóttir, Joakim Olbers, Jan Östergren, Frieder Braunschweig
CO was measured by a non-invasive inert gas rebreathing method (Innocor®, Innovision A/S, Odense, Denmark). A detailed description of this method has been published elsewhere [8]. In brief, patients inhaled a known volume of oxygen, 0.5% nitrous oxide (N2O), and 0.1% sulfur hexafluoride (SF6) over 5 breathing cycles. N2O and SF6 are inert gases out of which only N2O is soluble in blood allowing for determination of relative volumes of each gas in exhalation which approximates pulmonary blood flow and CO. Two measurements were performed after 5 min of rest in a sitting position (with 5 min in between for complete inert gas clearance) to establish a mean value. If the values differed >20% a third measurement was carried out. Values of CO, CI, volume of oxygen, volume of oxygen per kilogram, HR, SV, saturation, bolus dose, and maximal insoluble gas level were recorded. All tests were carried out by the same, experienced examiner.
Preparation of targeted theranostic red blood cell membranes-based nanobubbles for treatment of colon adenocarcinoma
Published in Expert Opinion on Drug Delivery, 2023
Tahoora Ghasemzadeh, Maliheh Hasannia, Khalil Abnous, Seyed Mohammad Taghdisi, Sirous Nekooei, Negar Nekooei, Mohammad Ramezani, Mona Alibolandi
Micro and nanobubbles (called MB and NB, respectively) are core–shell self-assembled nanoparticles comprising gas core and shell layer with various types of shell such as polymer, lipid, protein, and so on. In two recent decades, theranostic MB/NBs have been widely applied as innovative imaging and therapy approaches for cancer treatment while providing real-time monitoring of tumor physiology by their gaseous core as ultrasound contrast agents (UCAs) [15]. Perfluorocarbon and sulfur hexafluoride (SF6) gases have been widely implemented as UCAs due to their acceptable safety and lack of toxicity and poor water solubility. Stability of these inert gases in microbubbles coated with lipid could enhance their plasma circulation time, reduce their size distribution, and maintain their physical stability [16]. SonoVue is an FDA-approved UCA comprising microbubbles based on phospholipid, filled with SF6, offering pronounced characteristics such as low solubility, good safety, great echogenicity, prominent stability, and endurance against pressure [17].
Clinical analysis of high-intensity focused ultrasound (HIFU) combined with hysteroscopy-guided suction curettage (HGSC) in patients with cervical pregnancy
Published in International Journal of Hyperthermia, 2022
Yufu Huang, Xiaogang Zhu, Luying Wang, Mingzhu Ye, Min Xue, Xinliang Deng, Xin Sun
A JC-200 high-intensity focused therapeutic ultrasound system (Chongqing Haifu Medical Technology Co., Ltd., Chongqing, China) was used in HIFU ablation. Pre-operational preparation and HIFU ablation were performed as described below. In brief, after localization of the gestational sac by ultrasound scan, patients maintained a clear liquid diet for three days before the surgery. Before HIFU ablation, all patients took polyethylene glycol electrolyte solution (Wanhe Pharmaceutical Co., Ltd., Shenzhen, China) to clean their bowels. In the evening before the surgery and the next morning of the surgery, two times of enemas were performed. After being inserted with a urinary catheter, patients were placed in a prone position. The HIFU ablation was performed under general analgesia and sedation by giving patients of fentanyl (1 μg/kg, Renfu Co., Ltd., Jiangxi, China) and midazolam (0.02–0.03 mg/kg, Enhua Co., Ltd., Jiangsu, China) via intravenous injection. Sulfur hexafluoride micro-bubble (Bracco, Suisse, Italy) was used as an ultrasound contrast agent to localize the gestational sac and the surrounding blood supply. The treatment was stopped when the blood flow signal disappeared, and the grayscale changed. No apparent contrast agent perfusion was observed in the gestational sac tissue after HIFU treatment (Figure 2). After ablation, 500 ml of ice-cold saline was used to clean the patient’s bladder. After these procedures, all patients rested in a prone position in bed for 2 h. Antibiotics were given to patients for three days after the HIFU ablation to prevent surgical infections.