Smartphone Laser Speckle Perfusion Imaging Science Fair

ISEF Category: Biomedical Engineering

Subcategory: Biomedical Sensors and Imaging  ·  Difficulty: Advanced  ·  Setup: Home Setup  ·  Time: 1 to 2 Months

The Hook

Blood flow in your fingertips changes the instant you put your hand in cold water. Doctors check it by feeling pulses, which is subjective. Laser speckle contrast imaging measures it as a number, in real time, with no contact. A 3-dollar laser diode and your phone camera are enough to demonstrate the same idea hospitals use for surgical flap monitoring.

What Is It?

Laser speckle is the grainy pattern you see when coherent laser light scatters off a rough surface. When the surface contains moving blood, the speckle blurs in proportion to flow.

Laser speckle contrast imaging (LSCI) computes the local contrast of speckle patterns. Higher contrast equals less flow; lower contrast equals more flow. A simple Python script reads frames from the phone and produces a flow map.

The Allen test temporarily occludes one of the two arteries supplying the hand. Cold-pressor tests trigger vasoconstriction. Both maneuvers produce known, predictable changes in blood flow that you can use to validate the imaging pipeline.

Why This Is a Good Topic

LSCI is an active clinical research area and the budget version is striking. You will learn coherent imaging, contrast statistics, and clinical-validation tests.

Research Questions

• How does exposure time change speckle contrast?
• What is the effect of cold-pressor test duration on measured contrast?
• Does the Allen test produce expected vasoconstriction patterns?
• To what extent does skin tone affect raw contrast?
• Which region of interest gives the cleanest flow signal?
• How does ambient light contaminate the contrast?
• What is the effect of laser angle on flow map quality?

Basic Materials

• 3 dollar laser diode (class 2 or below).
• Phone with manual-exposure app.
• Tripod.
• 3D-printed mount and aperture.
• Ice water bath for cold-pressor test.
• Pulse oximeter for cross-check.
• Laser-safety eyewear and informed-consent template.

Advanced Materials

• Calibrated laser source.
• Motion phantom with adjustable flow.
• Pulse oximeter with PPG output.
• Clinical mentor.

Software & Tools

• Python (NumPy and OpenCV): Implements speckle contrast computation.
• scikit-image: Provides reference contrast functions.
• Matplotlib: Plots contrast time series.
• FFmpeg: Standardizes video preprocessing.

Experiment Steps

1. Document laser safety class and eyewear use.
2. Lock laser geometry, exposure, and ROI.
3. Calibrate contrast against a known motion phantom.
4. Run cold-pressor and Allen tests in randomized order.
5. Compute contrast time series.
6. Compare flow changes to pulse-oximeter trends and published patterns.

Common Pitfalls

• Skipping laser-safety review.
• Letting ambient light vary between maneuvers.
• Treating contrast as an absolute flow value.
• Mixing exposure settings across trials.
• Reporting one subject as a study.

What Makes This Competitive

A competitive entry documents laser safety (class 2 or below, eyewear), calibrates contrast against a known motion phantom, runs randomized maneuver orders within subjects, and reports agreement with pulse oximetry. Audit fairness across skin tones.

Project Variations

• Apply LSCI to wrist or forehead instead of fingertip.
• Combine with thermal imaging for a fusion flow map.
• Test the rig on a porcine ear (with appropriate ethics).

Learn More

• PubMed: Search laser speckle contrast imaging review.
• NIH PubMed Central: Open-access skin perfusion papers.
• OpenCV documentation: Free imaging tutorials.
• ANSI Z136 laser safety overview.
• MIT OpenCourseWare: Course 6.815 Computational Photography.