© imperial college londonpage 1 detecting gold nanoparticles in electron microscope images john...
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© Imperial College LondonPage 1
Detecting gold nanoparticles in electron
microscope images
John Cupitt, Exp. Med. & Tox.
16 November 2009
© Imperial College LondonPage 2
Technique
Use gold nanoparticles to label receptors, signalling proteins and lipids
Use up to three particle sizes to label different features
Image sections of cell membrane with transmission electron microscopy
Particle positions reveal information about membrane function
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TEM imaging of cell membrane fragments
Then fix lightly, label with gold particles, fix securely, stain, dry and image with TEM
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Problem
Gold nanoparticles are in the 3 – 15nm range, as few as 100 atoms
Image sections of cell membrane ~2000nm across containing several hundred particles
Particles therefore appear rather small: 4 - 12 pixels across
Standard blob detectors are designed for larger features and have poor accuracy at this scale
Only 50% accuracy with most systems
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Characteristics
Approximately Gaussian profile7 – 13 pixels acrossApproximately circularAmong the darkest objects in the image
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Our new detector
Gaussian ring divided into octants, convolve with each octant, take minimum response, compare to centre average
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Results
On the test image, with a little tuning, we get 99+% accuracySearching the whole 2,500 x 2,500 pixel image takes about 2 secondsNeed to test on more images, add some better tuning
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Credits
Nicolas Robidoux, Department of Mathematics and Computer Science, Laurentian University, designed the detector with help from Chantal Racette, an undergraduate studentThe NIH/NIGMS Center for the Spatiotemporal Modeling of Cell Signaling provided images and the gold standard, as well as funding for Chantal Racette's work.
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