Electrode Displacement Strain Imaging for Monitoring Radio-Frequency Ablation

Abstracts OPT1-016 Disinfection and Hygiene Practice in Medical Ultrasound: WFUMB Survey Results Jocelyne Basseal,1 Susan Campbell Westerway2 1 Australasian Society for Ultrasound in Medicine (ASUM), Australia, 2 WFUMB Council, ASUM and Charles Sturt University, Australia Objectives: As ultrasound technology rapidly evolves and is used more frequently in every area of medical diagnosis and treatment, it is overlooked as a potential vector in the transmission of a health care associated infection. Methods: A survey on the disinfection and hygiene practice in medical ultrasound was disseminated via WFUMB to its 6 member federations and associated ultrasound societies globally. Questions related to transducer disinfection, transducer cover usage, environmental cleaning and basic hygiene practices. Open ended questions provided an opportunity for respondents to discuss further issues with the ultrasound unit. Results: A total of 1029 responses were obtained, of which 67% comprised of sonographers and the remainder from specialist areas. Alcohol based wipes were used by 30% of respondents to clean external transducers and 12% of respondents to clean intracavity transducers. A total of 71% of respondents used transducer covers every time to scan open wounds, 61% when blood and bodily fluids were present and 76% for an interventional procedure. Open ended responses indicated that a large case load hindered the time required for cleaning and clear guidelines would be beneficial. Conclusions: Global survey results indicate that users do not comply with basic disinfection practice and there is a gap in knowledge on basic infection control education within the ultrasound unit. As the infectious status of a patient is not often disclosed prior to an ultrasound examination, training on recommended cleaning and disinfection of ultrasound equipment is imperative to mitigate the risk of potential infection. OPT1-017 Electrode Displacement Strain Imaging for Monitoring Radio-Frequency Ablation Wan-Hsin Hsieh, Meng-Han Tsai, Jo-Ping Lee, Hui-Hsin Lu Department of Image-guided Therapeutic Technology, Bio-IT Technology Division, Industrial Technology Research Institute, Taiwan Objectives: Percutaneous radiofrequency ablation (RFA) is a minimally invasive treatment to thermally destroy tumors, and the success of RFA is highly dependent on adequate ablation zone monitoring. Ultrasound-based electrode-displacement strain imaging is an emerging technique to delineate ablation boundaries, in which the electrode displacement is driven by an external stepper motor and an associated control system. In order to embed this imaging technique in RFA procedures with the least alterations of the RFA system, we conducted this feasibility study to carry out the electrode displacement by miniaturized electronics. Methods: In our implementation, tiny vibration motors commonly used for vibration alerting in communication devices is attached to the handle of ablation electrodes to drive submillimeter displacements of the electrode, which result in localized tissue deformation within the ablation zone that provides the mechanical stimuli required for strain imaging. Agar phantoms embedded with ablated meatball inclusion in vitro (2.5 cm in diameter) is used in experiments. Initial and displaced ultrasound backscattered signals are obtained and analyzed by one-

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dimensional cross-correlation to measure tissue displacement for imaging tissue strains. Results: Electrode-displacement strain imaging implemented with vibration motors can visualize the ablated meatball inclusion similar to that with the use of external stepper motor systems, in terms of sensitivity and accuracy of ablation boundaries. Conclusions: The implementation of electrode-displacement strain imaging for ablation monitoring with vibration motors is feasible and reliable.

OPT1-018 Preparation of Phase-Change Nanodroplets and an Experimental Study Shiyu Zhang Department of Ultrasonography, Nanfang Hospital, Southern Medical University, Guangzhou, China Objectives: To investigate the vaporization threshold of perfluoropentane encapsulated lipids nanodroplets and their feasibilities in assessing radio-frequency ablation margins in vitro. Methods: The nanodroplets with lipids shell and perfluoropentane (PFP) kemel was prepared by a Homogenization/emulsion method of which the size and zeta potential were measured by dynamic light scattering instrument (DLS). The phase change of perfluoropentane (PFP) nanodroplets (PFPNDs) stimulated by temperature rise was observed with the inverted optical microscope and ultrasonography. Echo intensity of bubbles generation from nanodroplets was calculated at different temperature points to plot the temperature-intensity curve. The temperature at the margins of hyperechogenicity zones generated from radiofrequency ablation (RFA) under ultrasonic guidance in tissue-mimicking phantom were measured with a thermocouple probe. Results: The mean diameter of PFPNDs was 479.9618.8nm. A few bubbles were observed at 50 C for PFPNDs with the inverted optical microscope, while a mass of bubbles generated rapidly from PFPNDs at 60 C, partly coalesced and ruptured ,and most of them ruptured at a higher temperature. No bubbles were observed in the Control group. With the ultrasonography, weak echo intensity of bubbles generated from PFPND at 50 C was detected. And when temperature rose to 60 C for PFPNDs or higher, the echo intensity reached peak value. Echo intensity in the Control group was not enhanced. The hyperechogenicity zones in the tissue-mimicking phantom dispersed with PFPNDs presented as elliptic shape along with the RFA needle, and the mean temperature at margin was 60.4 C. Little hyperechogenicity zones irregularly occurred in the Control group. Conclusions: The prepared PFPNDs can vaporize at given temperature. PFPNDs, with the vaporization threshold closed to the temperature threshold of tissues coagulative necrosis caused by RFA, is potential to assess the radiofrequency ablation margins in real time.

Poster Session PPT1-001 A Pilot on Radiographers’ Audit at Ultrasound: What Is the Passing Score? Rafidah Abu Bakar, Chin Chin Ooi, Irene Ai Linn Wong, Simin Denise Lau, Sally Hsueh Er Lee Department of Diagnostic Radiology, Singapore General Hospital, Singapore