Two Tools in One It’s Two, Two,
Technique enables simultaneous imaging and laser surgery without mechanical scanning.
BY LAURA S. MARSHALL
If a surgeon is about to use a probe in the brain, the patient is sure to want hat probe to be as small as possible.
And three University of California, Los
Angeles (UCLA), researchers have developed technology that could lead to tinier
probes that can perform both endoscopic
imaging and laser microsurgery at the
The technique, called “spectrally encoded confocal microscopy and microsurgery” – SECOMM for short – uses
light for both functions. And it’s the first
of its kind that does not require mechanical scanning for either.
Mechanical scanning is useful because
it enables acquisition of multidimensional
images. But it has its downsides in endoscopy.
“Fluctuations in mechanical scanning
introduce image noise and artifacts,” said
recent PhD graduate Kevin Kin-Man Tsia,
now an assistant professor in the department of electrical and electronic engineering at the University of Hong Kong. He
added that endoscopic probes using micro-
electromechanical systems (MEMS) scanners are similarly limited. And MEMS
scanners in miniaturized endoscopic
probes require a large probe size, up to ;1
cm, which limits their usefulness in clinical settings.
But SECOMM doesn’t have that problem.
UCLA researchers Dr. Kevin Kin-Man Tsia, left,
professor Bahram Jalali, center, and Dr. Keisuke
Goda have developed an endoscope-compatible
single-fiber-based device capable of simultaneous
imaging and high-precision laser microsurgery.
With the SECOMM method, a fiber combiner takes a broadband light source (for imaging) and combines it
with a wavelength-tunable continuous-wave laser followed by a fiber amplifier (for laser ablation). The 2-D
spatial disperser generates a “spectral shower,” and the spatial information about the sample is encoded into
the spectrum of the back-reflected spectral shower. The optical circulator routes the back-reflected spectral
shower to the spectrometer. Images courtesy of Kevin Kin-Man Tsia.
How it works
“The heart of SECOMM,” Tsia said, “is
an optical diffractive component: a two-dimensional spatial disperser which diffracts the different wavelengths of incident
light into 2-D space, creating a 1:1 map
between 2-D spatial coordinates and the
He said the 2-D spatial disperser delivers broadband light for imaging and wavelength-tunable light for laser surgery. Two
optical diffractive elements make this happen: a virtually imaged phase array (VIPA)
and a diffraction grating. The figure below,
left illustrates the SECOMM design.
“Both the broadband light and high-power tunable laser are coupled into the
same single fiber and the same 2-D spatial
disperser to perform simultaneous imaging
and high-precision laser microsurgery,”
The disperser transforms an incident
broadband light beam from a supercontin-uum pulse laser or an incoherent broadband light source into a 2-D spatial spectral pattern resembling a spectral shower,
which is used to illuminate the sample.
The sample’s 2-D spatial information is
encoded into the back-reflected “spectral
shower,” which is transmitted back to the
“nondispersed” – but image-encoded –
beam by the same 2-D spatial disperser.
The single-mode fiber re-collects the
beam, allowing transmission of 2-D
images of the sample, and a spectrometer
detects the image-encoded spectrum.
“Such imaging is essentially a confocal
microscope,” Tsia noted, “as the aperture
of the fiber that captures the reflection
from the sample rejects the scattered light
from out-of-focus axial planes.”
Folding the 1-D spectral data into a 2-D
matrix that represents the image allows for
digital reconstruction of the sample’s
Tsia said that a high-power wavelength-tunable laser beam will follow the same