Mustafa Asili

A Small Implantable Antenna for MedRadio and ISM Bands

In this letter, we present a small implantable antenna for MedRadio (401-406 MHz) and ISM (433-434.8 MHz) bands. The antenna is designed to be implanted under the skin and therefore tested by using skin-mimicking gels. We found very good agreement between the simulated and measured return loss. The antenna provided reliable data telemetry up to 20 m when tested indoors.

Flexible Microwave Antenna Applicator for Chemo-Thermotherapy of the Breast

In this letter, we propose a flexible microwave antenna applicator to induce mild hyperthermia that can be used in conjunction with chemotherapy. The antennas used were designed and tested using in vitro gels that mimic the electrical properties of human breast skin, fat, fibroglandular, and muscle tissues. Experiments show that the applicator can provide up to a 3 ° C temperature increase within the breast to successfully achieve mild hyperthermia. The results obtained in this letter suggest that a cost-effective local hyperthermia treatment technology that can be widely used at local clinical cancer treatment centers is plausible without using expensive applicators and electromagnetic shielding rooms.

Flexible microwave antenna applicator for chemothermotherapy of the breast

In this study, a flexible microwave antenna applicator is presented for mild microwave hyperthermia. The antennas used in this study are designed for high dielectric medium-like skin and tested using tissue mimicking gels that mimic the dielectrical properties of the human breast. After the initial antenna design the applicator is fabricated embvedding the antennas in PDMS. Finaly, we have tested the applicator using masimu of 5W input power. The experiments sugges that the proposed applicator provides a considerable heating up to 4cm depth with 5W at 450 MHz.

The effect of temperature on the microwave dielectric properties of porcine liver, lung, and heart

Recently, Microwave (MW) ablation emerged as a new technology with potential to eliminate the problems associated with RF ablation. In contrast to RF ablation, MW ablation uses higher frequencies (915 MHz and 2.4 GHz) and work on an electromagnetic energy propagation principle. When the microwave power is turned on, an antenna on the MW probe radiates electromagnetic energy into the tissue creating the ablation zone. As a result, MW ablation can be used for many organs such as lung and bones with higher impedance values where RF ablation would fail. Although microwave ablation therapy offers unique advantages over conventional radio frequency ablation therapy such as reduced ablation time, larger ablation zones, elimination of ground pads etc., there are still major problems associated with the existing microwave ablation devices on the market. Current devices use either dipole or slot antennas to deposit electromagnetic energy into the tissue. Such antennas are known to be very narrow band. During the design process, these antennas are matched to the tissue impedance at the frequency of operation (existing devices work at 915 MHz or 2.4 GHz). However, as soon as the microwave power is turned on, the electrical properties of the tissue (dielectric constant - εr and conductivity - σ) change due to increased temperature in the tissue. As a result, the power transmission characteristics of the entire system deteriorate. In order to better understand the power transmission characteristics of ablation antennas, we studied the microwave electrical properties of porcine liver, lung, and heart using the Agilent 805070 E slim form probe, a fiber optic temperature probe, and a smooth surface heat source. We manipulated the temperature from 25 °C to 80 °C and measured the dielectric properties between 500 MHz and 20 GHz.

Ultrawideband microwave ablation therapy (UMAT)

Despite many advantages, there are major problems associated with the current microwave ablation systems. These problems are mainly due to the narrowband nature of the antennas used in these systems. Our data show that although at the start of the ablation procedure more than 90% of the power is transmitted into the tissue due to good antenna-to-tissue impedance matching, as the temperature increases in the tissue, power transmission efficiency drops down to as low as 20%. Such degradation in power delivery creates three major problems: (1) Most of the power is reflected back to the device causing extreme heating and creating unwanted ablation zones beyond the region of interest. Currently, this problem is addressed by cooling the antenna shaft which complicates the probe design and increases the cost. We discuss this issue in detail and provide references in the “background and significance” section. (2) More power from the generator is needed to create the desired ablation zone. Currently, the power levels are as high as 100Watts (W). Our preliminary data suggest that even 20W is enough to create the desired ablation zones with UMAT. (3) Unnecessary increase in ablation time. Total ablation time suffers because of the inefficient power delivery into the tissue.

Microwave mild-hyperthermia for the chemo-thermotherapy of the breast

According to statistics from the National Cancer Institute, an increasing rate of breast cancer in the US makes the treatment of cancers more important. Besides conventional treatments, chemotherapy (CT) and radiation therapy (RT), different techniques are also being used to increase the efficiency of CT and RT for breast cancer. Hyperthermia, also called thermotherapy, is an adjunctive therapy that can be paired with conventional treatments. This method exposes electromagnetic energy into the targeted tissue to raise the temperature up to 45 °C, which increases perfusion and drug delivery inside the cancerous cells. However, high input power, screening room requirements with long application time prevents hyperthermia from applying in all clinics. Therefore, mild hyperthermia is experimented to make the process more applicable for patients. In this study, the goal is to observe the effect of low input power on tissue temperature at different depths of the breast in shorter time compared to current systems. Tissue temperature can be increased by 2–3 °C using this method. This technique will be applied by using a flexible microwave (MW) antenna applicator, which consists of 9 microwave antennas integrated in a circular-shaped PDMS, that is designed and fabricated. So, it can be given a shape on the breast. The breast can also be heated homogeneously with the located multiple antennas on the applicator. The antennas on the applicator are powered through feeding circuit, then it is attached on the breast mimicking gel. After that, fiber optic temperature sensors are placed at the depth of the gels and just under the surface. Firstly, measurements are taken of the temperature increase at the depth of 1 cm with 1W power at 1.6 GHz without time limits. Then, gradually increased power up to 5W is applied at 1cm depth. Thereafter, the depth is increased and the measurements are repeated at 2.5cm and 4cm depths for all power levels again with a limited time to 10 minutes. We show that the proposed applicator is very efficient for mild-hyperthermia for chemo-thermotherapy of the breast.

Patient specific 3D tissue mimicking gels

According to The National Center for Biotechnology Information (NCBI), patient specific modeling (PSM) is gaining attention from research groups because of its improvements in medical diagnosis and that it can predict what therapies and surgical procedures are needed for individual patients. Patient specific modeling takes a patients CT or MRI data and develops it into a computational patient specific model. One important aspect of designing medical devices that utilize microwave and electromagnetic fields is the in vitro testing stage where a gel that mimic the human tissues is used. Currently, generic tissue mimicking gels have been used for testing medical devices and not PSM gels.

Adjustable zone microwave ablation

According to The National Cancer Institute, over 1.6 million people will be diagnosed with cancer in the United States in 2015. Of those diagnosed, more than 50% of patients experience liver metastasis. Only 30% of patients with liver metastasis tumors will have disease amenable to surgical resection due to high surgical risk or unfavorable anatomy. One successful treatment technique for the removal of tumors formed in the liver has been Radio Frequency (RF) ablation in the last two decades. Recently, microwave (MW) ablation emerged as a new technology with potential to eliminate the problems associated with RF ablation. Some of the problems associated with RF ablation include high power requirements (up to 200W), the use of ground pads and associated skin burns, and the small zone of ablation (∼mm). In contrast to RF ablation, MW ablation uses higher frequencies (915 MHz and 2.4 GHz) and work on an electromagnetic energy propagation principle. When the microwave power is turned on, an antenna on the MW probe radiates electromagnetic energy into the tissue creating the ablation zone. As a result, besides the heart, MW ablation can be used for many organs such as lung and bones with higher impedance values where RF ablation would fail. Despite many advantages, there are still major problems associated with the current MW ablation systems. These problems are mainly due to the narrowband nature of the antennas used in these systems.

Conformal antenna applicator for mild hyperthermia of the breast

Summary form only given. According to statistics from the National Cancer Institute, an increasing rate of breast cancer in the US makes the treatment of cancers more important. Besides conventional treatments, chemotherapy (CT) and radiation therapy (RT), different techniques are also being used to increase the efficiency of CT and RT for breast cancer. Hyperthermia, also called thermotherapy, is an adjunctive therapy that can be paired with conventional treatments. This method exposes electromagnetic energy into the targeted tissue to raise the temperature up to 45 °C, which increases perfusion and drug delivery inside the cancerous cells. However, high input power and screening room requirements with long application time prevents hyperthermia from being applied in all clinics. Therefore, mild hyperthermia is experimented to make the process more applicable for patients. In this study, the goal is to observe the effect of low input power on tissue temperature at different depths of the breast with a shorter application time compared to current systems. Tissue temperature can be increased by 2-3 °C using this method. This technique will be applied by using a flexible microwave antenna applicator, which consists of 9 microwave antennas integrated in a circular-shaped PDMS, that is designed and fabricated. The breast can also be heated homogeneously with the located multiple antennas on the applicator. Six of the antennas are powered by an amplifier with a power divider, then it is attached on the breast mimicking gel. After that, fiber optic temperature sensors are placed at the depth of the gels and just under the surface. Measurements are taken of the temperature increase at the depth of 1 cm, with 1W power, at 450 Mhz without time limits while gradually increasing the power up to 5W. Thereafter, the depth is increased and the measurements are repeated at 2.5cm and 4cm depths for all power levels again with a limited time of 10 minutes. Design of the flexible microwave antenna applicator and test results will be presented.

Lab-on-a-chip: Continuous glucose monitoring antenna sensors

The development of a reliable continuous glucose monitoring technology, which would lessen the complications associated with diabetes through optimal glycemic control, is a key to improving the quality of lives of patients living with the disease. In recent years, considerable progress has been made in developing implantable biosensors that can continually monitor glucose levels. These biosensors rely on the interstitial fluid within the dermis to measure the interstitial glucose (IG) levels. However, to be truly beneficial, the implanted sensor must be able to function properly for an extended period of time. The biosensors developed thus far can only remain functional up several weeks after their implantation in the body. Contributing factors for this loss of functionality include the degradation and fouling of the sensor, and the changes in the tissue surrounding the sensor such as fibrosis and inflammation. While researchers explore potential solutions to improve the current implantable biosensors, there is an urgent need to investigate alternative technologies. Unless a reliable technology for long-term glucose monitoring is developed, continuous glucose monitoring is expected to remain problematic, and patients will continue to face the life-threatening complications associated with poor glycemic control. In order to provide a potential solution to this problem, in this study, we propose a lab-on-chip antenna sensor for continuous monitoring of the glucose concentration in the interstitial fluid. Unlike biosensors that require direct contact with the interstitial fluid in order to trigger necessary chemical reactions to operate, the new sensor works on an electromagnetic energy propagation principle. Thus, it does not need direct interface with the interstitial fluid and can be fabricated using biocompatible materials allowing it to remain functional in the body for years.