If you care about precision medicine, then you care about medical devices. And, in today’s MedTech climate, if you care about medical devices, then it is an exciting time to care about ablation platforms. Ablation techniques are minimally invasive, which make them the most viable option for a range of conditions, from targeting difficult-to-access cancers to managing chronic pain or hypertension through selective nerve deactivation. Yet, even with all this potential, ablation modalities are typically not first-line treatments because patient-to-patient variability reduces procedure repeatability. This is exactly where a device that can be tailored to the specific condition of the patient can lead to better procedural outcomes and ultimately benefit the patient. More importantly, this opens the door to make ablation modalities more routine for applications that are near or within sensitive organs.
For the most part, current systems designs do not incorporate our latest understanding of the biophysics; in fact, they are largely based on ablation systems that were developed decades ago. This knowledge, coupled with new sensing technologies, computational-based algorithms, and improved imaging capabilities, provides an opportunity to develop patient-specific ablation devices that could unleash the use of ablation modalities.
Efficacy of any ablation modality is often defined as achieving the needed ablation size in the desired location, with minimal collateral damage to healthy surrounding tissue. In interventional oncology, this means ablating the cancerous lesion with the needed margin. In neuromodulation applications such as renal denervation, it means precisely ablating the nerves in the wall of the renal artery.
While the ablation size and location are common desired parameters, the anatomical location is an important factor since the relevant tissue properties may (and often do) significantly vary. For example, from an electromagnetic and thermal point of view, the properties of lung and liver are significantly different from each other. The surrounding anatomy is another important factor, as an ablation lesion within an organ’s parenchyma is governed by different constraints than if it is near bone anatomy or near other sensitive organs. This means that one cannot take an ablation system and just use it for another indication with only some minor modifications. There also is inter-patient variability — for example, the location of the tumor within an organ varies between patients and that could mean that the same ablation algorithm could lead to different outcomes.
What is surprising is that most ablation systems are largely the same, even across indications. Of course, there are some variations on the size of the probes and some differences in algorithms. But mainly, most ablation devices are based on simple impedance or temperature end points, along with a few parameters, such as power level and duration of treatment with coarse adjustment settings.
These limitations in system design have made ablations therapies operator dependent — relegating the efficacy of the therapy to the skill and experience of the clinician performing the procedure. Thus many practitioners believe in the utility of ablation, but often are hesitant about using it for treatment in sensitive regions such as the lung or pancreas. Even in applications in which ablation techniques are often used, such as liver cancer, there is a lot of uncertainty about best practices. From personal experience, I’ve spoken with many doctors who have described experiencing difficulty with basic aspects of the therapy, such as patient-to-patient variability impacting one’s ability to discern when an ablation procedure is complete.
Opportunities for future systems
As a first step, we need to utilize our increased understanding of ablation biophysics in designing future systems. As an example, let’s look at thermal based ablations. There is a lot that can be leveraged from the field of hyperthermia in which the concept of thermal dose, temperature-time relationship, and impact on cell viability, is critical to therapy efficacy. As the figure below shows, once exposure temperatures reach above 45°C, cell survival rates significantly decrease.