Pub Date : 2023-07-03DOI: 10.1109/JERM.2023.3285049
Jacob T. Pawlik;Nikolas D. Barrera;Eugene J. Yoon;James C. Booth;Christian J. Long;Nathan D. Orloff;Ellis Meng;Angela C. Stelson
Parylene C is a widely used dielectric barrier in implantable medical devices because it conforms well to surfaces and insulates against biological environments. However, multiple studies have shown that moisture can intrude into Parylene C films through defects and intrinsic diffusion, leading to delamination and device failure. While many studies have tested device integrity in vitro, few have isolated the influence of specific degradation mechanisms on device failure. Here, we use a broadband impedance technique called Microwave Microfluidic Spectroscopy (MMS) to measure fluid permeation in targeted regions of Parylene C films that are free of defects and have optimal adhesion to the substrate. We found no changes in the broadband S-parameters from 100 MHz–110 GHz for Parylene C coated coplanar waveguides soaked in water or phosphate buffered saline at 20 °C or 37 °C for two months. Furthermore, there was no delamination induced by fluid soaking. Our study helps to clear debate about the influence of water and ion diffusion on Parylene C device lifetime and inform better fabrication of Parylene C coatings for implantable devices.
{"title":"The Influence of Intrinsic Water and Ion Permeation on the Dielectric Properties of Parylene C Films","authors":"Jacob T. Pawlik;Nikolas D. Barrera;Eugene J. Yoon;James C. Booth;Christian J. Long;Nathan D. Orloff;Ellis Meng;Angela C. Stelson","doi":"10.1109/JERM.2023.3285049","DOIUrl":"10.1109/JERM.2023.3285049","url":null,"abstract":"Parylene C is a widely used dielectric barrier in implantable medical devices because it conforms well to surfaces and insulates against biological environments. However, multiple studies have shown that moisture can intrude into Parylene C films through defects and intrinsic diffusion, leading to delamination and device failure. While many studies have tested device integrity in vitro, few have isolated the influence of specific degradation mechanisms on device failure. Here, we use a broadband impedance technique called Microwave Microfluidic Spectroscopy (MMS) to measure fluid permeation in targeted regions of Parylene C films that are free of defects and have optimal adhesion to the substrate. We found no changes in the broadband S-parameters from 100 MHz–110 GHz for Parylene C coated coplanar waveguides soaked in water or phosphate buffered saline at 20 °C or 37 °C for two months. Furthermore, there was no delamination induced by fluid soaking. Our study helps to clear debate about the influence of water and ion diffusion on Parylene C device lifetime and inform better fabrication of Parylene C coatings for implantable devices.","PeriodicalId":29955,"journal":{"name":"IEEE Journal of Electromagnetics RF and Microwaves in Medicine and Biology","volume":"7 4","pages":"328-335"},"PeriodicalIF":3.2,"publicationDate":"2023-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72592318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.1109/JERM.2023.3289155
Peter M. Asbeck;Sravya Alluri;Vincent Leung;Shaghayegh Abbasi;Milan T. Makale
Pulse stimulation of peripheral nerves (PNS) is extensively used in the diagnosis of nerve abnormalities and can be applied for pain mitigation and to promote nerve regrowth. Nerve stimulation via magnetic pulses can provide advantages over conventional electrical stimulation; it obviates the need for electrode contact with the skin and is typically less painful. This work contributes to the development of compact and portable systems for magnetic PNS (M-PNS). To date, M-PNS has largely employed pulse generation systems developed for repetitive transcranial magnetic stimulation (rTMS). A new circuit is demonstrated to generate pulsed magnetic fields that increases induced electric (E) field intensities over those attainable in conventional rTMS systems. The resultant E-field has a shortened duration. The required external voltage input is below 300 V. A compact circuit implementation produced peak E-fields of 280 V/m at 1.5 cm distance from the magnetic coil, in 23 μs pulses (while 70-280 μs pulses are typically used for rTMS). Although threshold E fields for neural excitation increase with shorter pulse widths, neural excitation is demonstrated in human subjects via ulnar nerve stimulation and electromyography. This circuit technique may facilitate greater feasibility and flexibility in the design of miniaturized and portable PNS medical devices.
{"title":"An Efficient Circuit for Pulsed Magnetic Neural Stimulation","authors":"Peter M. Asbeck;Sravya Alluri;Vincent Leung;Shaghayegh Abbasi;Milan T. Makale","doi":"10.1109/JERM.2023.3289155","DOIUrl":"https://doi.org/10.1109/JERM.2023.3289155","url":null,"abstract":"Pulse stimulation of peripheral nerves (PNS) is extensively used in the diagnosis of nerve abnormalities and can be applied for pain mitigation and to promote nerve regrowth. Nerve stimulation via magnetic pulses can provide advantages over conventional electrical stimulation; it obviates the need for electrode contact with the skin and is typically less painful. This work contributes to the development of compact and portable systems for magnetic PNS (M-PNS). To date, M-PNS has largely employed pulse generation systems developed for repetitive transcranial magnetic stimulation (rTMS). A new circuit is demonstrated to generate pulsed magnetic fields that increases induced electric (E) field intensities over those attainable in conventional rTMS systems. The resultant E-field has a shortened duration. The required external voltage input is below 300 V. A compact circuit implementation produced peak E-fields of 280 V/m at 1.5 cm distance from the magnetic coil, in 23 μs pulses (while 70-280 μs pulses are typically used for rTMS). Although threshold E fields for neural excitation increase with shorter pulse widths, neural excitation is demonstrated in human subjects via ulnar nerve stimulation and electromyography. This circuit technique may facilitate greater feasibility and flexibility in the design of miniaturized and portable PNS medical devices.","PeriodicalId":29955,"journal":{"name":"IEEE Journal of Electromagnetics RF and Microwaves in Medicine and Biology","volume":"7 3","pages":"258-265"},"PeriodicalIF":3.2,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50404732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In recent years, cerebrovascular disease has become one of the leading causes of death among Chinese residents. Early detection of brain disease is, therefore, of great significance in reducing the risks to life and health. Thermoacoustic imaging has emerged as a promising technique for detecting brain disease, which meets the requirements of high penetration depth and real-time imaging in transcranial imaging. However, the acoustic characteristics of the skull can significantly impact the propagation of thermoacoustic signals, leading to attenuation and apparent phase difference, resulting in poor quality of reconstructed image and location deviation of symptom points. In this study, a skull phase compensated method combined full waveform inversion for transcranial thermoacoustic imaging is proposed. The adaptive positioning of skull is realized firstly by improving the W-AIC algorithm in thermoacoustic imaging to solve the phase difference problem and FWI technology is applied for reconstructing the intracranial SoS distribution. Numerical simulation of a human brain model and actual human skull experiments further verify the feasibility of this method in improving the quality of thermoacoustic images, thereby providing a reliable theoretical basis for the clinical application of transcranial thermoacoustic imaging.
{"title":"Skull Phase Compensation Combined Full Waveform Inversion for Transcranial Thermoacoustic Imaging With a Real Human Skull Validated","authors":"Shuang-Li Liu;Xin Shang;Wan-Ting Peng;Wei-Jia Wan;Jin-Bao Zhang","doi":"10.1109/JERM.2023.3281057","DOIUrl":"10.1109/JERM.2023.3281057","url":null,"abstract":"In recent years, cerebrovascular disease has become one of the leading causes of death among Chinese residents. Early detection of brain disease is, therefore, of great significance in reducing the risks to life and health. Thermoacoustic imaging has emerged as a promising technique for detecting brain disease, which meets the requirements of high penetration depth and real-time imaging in transcranial imaging. However, the acoustic characteristics of the skull can significantly impact the propagation of thermoacoustic signals, leading to attenuation and apparent phase difference, resulting in poor quality of reconstructed image and location deviation of symptom points. In this study, a skull phase compensated method combined full waveform inversion for transcranial thermoacoustic imaging is proposed. The adaptive positioning of skull is realized firstly by improving the W-AIC algorithm in thermoacoustic imaging to solve the phase difference problem and FWI technology is applied for reconstructing the intracranial SoS distribution. Numerical simulation of a human brain model and actual human skull experiments further verify the feasibility of this method in improving the quality of thermoacoustic images, thereby providing a reliable theoretical basis for the clinical application of transcranial thermoacoustic imaging.","PeriodicalId":29955,"journal":{"name":"IEEE Journal of Electromagnetics RF and Microwaves in Medicine and Biology","volume":"7 4","pages":"313-319"},"PeriodicalIF":3.2,"publicationDate":"2023-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75290361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-07DOI: 10.1109/JERM.2023.3281726
Sen Bing;Khengdauliu Chawang;J.-C. Chiao
In this work, a planar microwave sensor based on a flexible polyimide substrate has been developed to distinguish if a skin lesion is malignant or benign. The sensor is a tuned loop resonator operating in the industrial, scientific, and medical (ISM) band at 2.465 GHz, providing a localized high-intensity electric field that penetrates into tissues with sufficient spatial and spectral resolutions. The loop resonator with a radius of 5.4 mm was tuned by a concentric metal pad to the desired resonant frequency with a sufficiently high quality factor of 98.7 and a reflection coefficient of $-$