Can I put even more effort into this workout session? Are the soldiers completely exhausted, or can they manage for another hour before they have to eat? How is the muscle mass developing in the patient in the intensive care unit?
To answer these questions, information on several physiological parameters will be useful. In this project, we have investigated whether ultrasound measurements of muscles can provide useful and robust information about physiological status.
Ultrasound imaging is widely used to make the correct diagnosis both in hospitals and in the primary health care service. Instead of analyzing images, we investigated the possibility of using one-dimensional ultrasound signal, that e.g. can be transmitted and recorded by a small and simple ultrasound sensor. Such a sensor sends and receives ultrasonic pulses that carry information about the condition of, for example, a muscle group.
In our experiments 10 healthy volunteers performed an exhausting exercise session on an exercise bike, while ultrasound data was collected before, during and after the session. The analysis show that there is a change in the signal over time, but the results are so far not conclusive. Further analysis is therefore required to conclude if and how such monitoring best can be done.
Today, it is possible to develop cheap and miniaturized sensors that, in combination with modern battery technology and wireless communication, can be attached to the body as a fully portable meter. We see that micromachined ultrasound transducers can be suited for medical sensors or in combination with sports and fitness electronics. By sending real-time results to a sports watch or to medical monitoring equipment, physiological changes can be detected, for example during a training session or in patients who are bedridden over time.
In the qualification project we performed a proof-of-concept experiment where healthy volunteers underwent an exhausting exercise session and ultrasound data collected from their muscles before, during and after the session was compared. The results so far are inconclusive, but a further analysis of the extensive dataset is needed to conclude whether monitoring of the glycogen status in muscles using ultrasound is possible. If the method proofs viable, we believe it to be further applicable in assessing muscle atrophy in ICU patients, and nutrition and hydration status in frail patients.
We see micromachined ultrasound transducers (PMUTs) as suited for use as medical ultrasound sensors for patient monitoring, and find that the design flexibility and possibility of large batch fabrication of such devices, can make them applicable to many different clinical settings and available at low cost.
Assessment and monitoring of physiological status can be beneficial for several user groups, both within patient care, military, sports medicine and recreation. We believe that a miniaturized ultrasound sensor collecting a 1D data stream can be capable of real time continuous monitoring and aim at performing proof-of-concept experiments in this qualification project to assess the technological potential with muscle monitoring as a use-case.
Initial experiments performed at SINTEF have shown that through ultrasound measurements of muscles during strenuous exercise, a difference in acoustic signal related to the physiological status (glycogen and hydration status) can be detected. Partial agreement in the results from ultrasound image analysis and the analysis of 1D data from an emulated single-element ultrasound sensor has been shown, but more extensive experiments are needed to assess the potential of the methodology and further develop and improve the analytic methods that can enable automatic and robust measurements.
SINTEF has a portfolio of patents on piezoelectric micromachined ultrasound transducers (PMUTs), and are currently developing sensors both for air and water/tissue applications. The PMUT technology platform can be a game-changer within wearable sensors for patient monitoring, where cardiac/ respiration monitoring, bladder filling, or muscle assessment all are possible applications.
Three main tasks will be included in this qualification project:
- Perform experiments on several individuals, where skeletal muscles are imaged with ultrasound before, during and after exercise. 2D and 1D data will be analyzed and compared.
- Assess market potential for an ultrasound system with a 1D data stream in patient monitoring.
- Assess how the PMUT technology can be used in various applications within patient monitoring.