Technique enables simultaneous imaging and laser surgery without mechanical scanning.
Two Tools in One
BY LAURA S. MARSHALLMANAGING EDITOR
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, LosAngeles (UCLA), researchers have developed technology that could lead to tinierprobes that can perform both endoscopicimaging and laser microsurgery at thesame time.
The technique, called “spectrally encoded confocal microscopy and microsurgery” – SECOMM for short – useslight for both functions. And it’s the firstof its kind that does not require mechanical scanning for either.
Mechanical scanning is useful becauseit enables acquisition of multidimensionalimages. But it has its downsides in endoscopy.
“Fluctuations in mechanical scanning
introduce image noise and artifacts,” said
recent PhD graduate Kevin Kin-Man Tsia,
But SECOMM doesn’t have that prob-
lem.
How it works
“The heart of SECOMM,” Tsia said, “is
an optical diffractive component: a two-
dimensional spatial disperser which dif-
fracts the different wavelengths of incident
light into 2-D space, creating a 1:1 map
between 2-D spatial coordinates and the
optical wavelengths.”
He said the 2-D spatial disperser deliv-
ers broadband light for imaging and wave-
length-tunable light for laser surgery. Two
optical diffractive elements make this hap-
pen: 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,”
Tsia said.
The disperser transforms an incident
broadband light beam from a supercontin-
uum pulse laser or an incoherent broad-
band light source into a 2-D spatial spec-
tral 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 confocalmicroscope,” Tsia noted, “as the apertureof the fiber that captures the reflectionfrom the sample rejects the scattered lightfrom out-of-focus axial planes.”
Folding the 1-D spectral data into a 2-Dmatrix that represents the image allows fordigital reconstruction of the sample’simage.
Tsia said that a high-power wavelength-tunable laser beam will follow the same
With the SECOMM method, a fiber combiner takes a broadband light source (for imaging) and combines itwith a wavelength-tunable continuous-wave laser followed by a fiber amplifier (for laser ablation). The 2-Dspatial disperser generates a “spectral shower,” and the spatial information about the sample is encoded intothe spectrum of the back-reflected spectral shower. The optical circulator routes the back-reflected spectralshower to the spectrometer. Images courtesy of Kevin Kin-Man Tsia.
UCLA researchers Dr. Kevin Kin-Man Tsia, left,professor Bahram Jalali, center, and Dr. KeisukeGoda have developed an endoscope-compatiblesingle-fiber-based device capable of simultaneousimaging and high-precision laser microsurgery.
It’s Two, Two,
