Arterial blood pressure waveform monitor

Team
Joohyun Seo SM ’14 and Sabino Pietrangelo SM ’13, graduate students, Department of Electrical Engineering and Computer Science
Hae-Seung Lee, Advanced Television and Signal Processing Professor of Electrical Engineering; director, Center for Integrated Circuits and Systems
Charles Sodini, Clarence J. LeBel Professor of Electrical Engineering; co-director, Medical Electronic Device Realization Center

Size
Portable ultrasound monitor: 14.7 cm × 13.2 cm; transducer: 2.5 cm × 5 cm × 5 cm

Purpose
Use ultrasound to take a comprehensive measurement of blood pressure at the carotid artery.

How it works
When arterial blood pressure (ABP) is measured at an ambulatory clinic, it’s usually recorded as two numbers. The higher of the two represents the pressure in the arteries when the heart muscle contracts; the lower marks the pressure when the muscle rests between heartbeats. In reality, of course, there are many data points in between these “systolic” peaks and “diastolic” lows. This monitor is designed to capture the pressure waveform (i.e., the blood pressure as a function of time). The device collects the data noninvasively, without squeezing or blocking the artery, by using ultrasound to continuously measure the artery’s cross-sectional area and elasticity.

Status
In 2015 the device was tested on nine healthy subjects, and the results of the clinical study—validating the potential of the approach—were published. The next step is to make the measurements insensitive to mispositioning of the transducer, which would lower the level of skill required to operate it. Its creators are also considering miniaturization of the components for implementation as a wearable device.

The big picture
The use of a portable ABP waveform monitoring device—less expensive and less risky than the current practice of measuring ABP at central circulatory sites through arterial catheterization—could improve routine monitoring of hypertensive patients. The massive new data sets it could provide to researchers would also open the door to greater understanding of cardiovascular disease and other health conditions.

Miniaturized, biopsy-implantable chemical sensor

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Team
Michael Cima, David H. Koch Professor in Engineering in the Department of Materials Science; investigator at the Koch Institute for Integrative Cancer Research
Vincent Liu SM ’09, PD ’14, PhD ’14, MIT postdoc (former)
Christophoros Vassiliou ’04, MNG ’06, PhD ’13, MIT postdoc (former)

Size
2.2 mm in diameter; 6 mm in length

Purpose
Provide ongoing information about cancerous tissue’s chemical response to treatment.

How it works
The sensor is designed for long-term implantation in a tumor by means of a biopsy needle, in order to collect longitudinal data related to two biomarkers: pH and dissolved oxygen. The data are actionable. For example, decreased acidity of cancerous tissue is an indication that chemotherapy is working; and low-oxygen levels can signal the need to increase radiation therapy. The sensor is filled with responsive nuclear magnetic resonance contrast agents for chemical sensitivity, similar to those used in magnetic resonance imaging (MRI). The device contains onboard circuitry and sends its data wirelessly to an external reader device, on which it relies as a power source through a magnetic process called mutual inductance.

Status
In July 2015 the team published a paper in the journal Lab on a Chip summarizing its work on the sensor; currently, it is engaged in building a clinically acceptable reader device.

The big picture
As an alternative to MRI, the sensor could enable less expensive and more frequent measurements. Real-time data help doctors make nimble adjustments to therapies and drug dosages, rather than waiting months for an indication of whether treatments are working. The data also help them see past misleading symptoms such as inflammation, which can make tumors falsely appear to grow. The bottom line for cancer patients is a shot at better outcomes with fewer unnecessary side effects.

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