Microwave ablation (MWA) offers an established, cost-effective, minimally invasive therapy that can be used to treat cancer tumors, most times as an outpatient procedure. In general, MWA procedures are performed by using image guidance (typically CT and/or ultrasound) to insert a needle-like applicator, embedded with a microwave antenna, into a tumor and then energizing the antenna to heat and kill the tumor. In addition to being much less invasive and expensive than traditional treatments, it also provides a non-toxic, localized, and repeatable option. However, the fundamental technical problem to broader MWA clinical acceptance is that all currently available MWA systems can only produce a roughly spherical or ellipsoidal treatment zone centered on the tip of the applicator, which is not suitable for treating tumors with irregular shapes or those located near critical anatomy. It is therefore extremely difficult to reliably ensure the entire tumor is killed without also damaging adjacent critical anatomy. This limitation leaves doctors with a difficult choice of risking undertreatment and disease recurrence or risking overtreatment and damage to critical healthy anatomy that may cause pain or life-threatening complications.

In Phase I, our team developed a directional microwave ablation (MWA) applicator with an overall diameter of less than 14 gauge (2.1 mm). It does not need to be inserted directly into the center of a target tumor, but could instead be placed alongside it. This enables a faster procedure with less chance of complications or disease recurrence that could also be adapted for treatment of an expanded range of medical conditions beyond oncology. Alternatively, if our directional MWA applicator was inserted into the tumor, different generator power and time settings could be used for treating different sectors of the tumor, enabling the creation of irregular ablation zone shapes by rotating the applicator. Clinical value comes from the ability to produce a more targeted, consistent, and predictable ablation zone than any existing MWA system.

Our Phase I research activities consisted of a staged development approach to show technical proof of concept and to optimize the design of a directional MWA applicator suitable for clinical use. We began with computer model based simulation using finite element method (FEM) multi-physics software to test the feasibility of new design variants based on radiation pattern directionality and antenna impedance matching. We then developed methods and sourced materials to fabricate functional prototypes of the most promising designs. This design process was very iterative, and if the new design variants could be successfully constructed, the computer models were adjusted to include the actual material dimensions and measured material properties, where possible. Adjustable/tunable antenna parameters were further optimized using updated computer models. The final design candidates were evaluated and extensively characterized experimentally on the benchtop in ex vivo tissue to assess size and shape of ablation profiles as a function of applied power and ablation duration. Further, a pilot study was conducted in porcine liver in vivo. Based on ex vivo and pilot in vivo performance, ease of manufacturability, and durability, the best directional applicator was selected for more detailed evaluation in porcine liver in vivo evaluation ? the established animal model for pre-clinical evaluation of thermal ablation technologies ? including experiments designed specifically to test usability in clinical applications which critically depend on directionality.

The technical research and development accomplished during Phase I advanced new concepts and methods within the field and resulted in a new US provisional patent application titled ?Minimally Invasive Microwave Ablation Device? filed on May 24, 2019 (No. 62852671).

The results of the ex vivo and in vivo experimental testing and characterization of our new directional MWA applicator design, which demonstrate the clinical potential for this technology, are reported in a manuscript in preparation for submission to the Journal of Vascular and Interventional Radiology.

Thanks in large part to Phase I funding, Precision Microwave was successful in achieving several critical technical development milestones towards commercialization of our directional MWA technology. We were also able to make significant strides in further validating the clinical need for our technology and gain a better understanding of our prospective markets and commercialization path by sharing our Phase I results with prospective clinical and industry partners. We are now more confident than ever that our technology will solve a significant clinical need and once in the hands of doctors will evolve to provide minimally invasive treatment to wider range of patients than we could currently imagine.

Last Modified: 08/08/2019
Modified by: Austin Pfannenstiel