Safe and accurate diagnosis without blood removal

Commercialization of Cardiovascular OCT
Hiroshi Ogawa ( h_ogawa@kodai-co.com , +81-90-1507-5961 )KODAI Co., Ltd Yokohama, Japan (URL http://kodai-co.com )ABSTRACTRESULTSThe one-dimensional image information to be obtained by OCT can beapproximated by the finite discrete frequency spectrum, that is, theimage information can be obtained by measuring the phase andamplitude of the reflected wave at each discrete frequency. As a resultof simulating a new OCT incorporating spread-spectrum
communication technology, which is well known in the communication
field as a high-sensitivity measurement method, It was confirmed thatthe new method is effective in improving sensitivity and suppressing
background noise generated due to light scattering in the living body.
A Bessel beam is used to further improve depth, resolution, andsharpness. Compared to the Gaussian beam, the Bessel beam cangenerate a longer beam with a small diameter, reduce the effective
attenuation of the beam, have a self-regeneration function, and also
have a scattering noise suppression function, so the depth ofpenetration long observation is possible. The superiority of the Bessel
beam is clarified in the paper. [2]Concluding, by combining the new OCT and Bessel beam, it ispossible to provide a cardiovascular OCT that can observe theperivascular membrane without removing blood. Since this combination
has a high depth of invasion and high resolution, it can be expected tocontribute to many medical fields such as cancer diagnosis andophthalmic diagnosis.

New method OCT (M-FD-OCT)
Sensitivity: 150dB-200dB (current SS-OCT: 100dB)
Dynamic range: 150dB-200dB (current SS-OCT: 60dB)
The observable depth is determined by the dynamic range.
New method OCT depth> 3 X SS-OCT depth
Bessel beamSignificant reduction of beam attenuation in blood: ≈ 8dB/mm or LessResolution

Conventional
OCT
Ultrasonicecho

The depth of penetration of
the new OCT has increased
significantly compared to thecurrent OCT.

New method OCT(M-FD-OCT+Bessel Beam)
Confocal microscope

Penetration Depth

Phase contrast
microscope

Table 1. New Cardiovascular OCT vs. Conventional OCT/IVUS

METHODS
A coherent carrier is used to generate a two-phase phase-modulated
picosecond pulse of M-series code, branching, irradiating the tissue
with one to obtain a reflected signal, frequency-converting the other,and illuminating the mirror. The reflected wave is generated as areference wave. If the optical path difference between the reflectedsignal and the reference wave is within the pulse width, two-wave
interference occurs. The two-wave interference signal is detected, andthe IQ signal of this interference signal is extracted to obtain thediscrete spectrum. This is the frequency spectrum of the onedimensional image signal. A spectrum can be similarly obtained at aplurality of optical frequencies having a frequency difference that is an
integral multiple of the base frequency determined by the pulse width.
One-dimensional image information can be obtained by synthesizingthese spectra. By changing the optical path length of the reference
wave, it is possible to obtain a one-dimensional entire image of thetarget range.
The block diagram of the system is shown below.

Conventional OCT

New OCT (M-FD-OCT)

Fig.1 Block diagram of New OCT (M-FD-OCT)

CONCLUSIONS
M-sequence DPSK modulated Pulse

We use a Bessel beam instead of the traditional Gaussian beam toirradiate the Tissue. For cardiovascular OCT, we will develop and use avery small Bessel beam generator with a diameter of 1 mm or less at
the tip of the catheter.
The Bessel beam has features such as being able to maintain a narrow
beam over a long distance, being able to regenerate the beam behindan obstacle on the beam and suppressing effective loss.

a narrow beam over a long distanceregenerate the beamFig.2 Comparison of Gaussian beam and Bessel beamThe newly proposed OCT (M-FD-OCT) uses a pulse train signal
phase-modulated with pseudo-noise that has autocorrelation, and cangreatly improve the signal-to-noise ratio due to the range gatefunction and correlation gain. Furthermore, by using an opticalamplifier, a high-sensitivity OCT that can capture reflected signals
below the very weak shot noise is realized. Further, the signal-tonoise ratio can be improved optically by using the Bessel beam.
Therefore, it was found that an image with a depth of 4-6 times that of
the conventional OCT (SS-OCT + Gaussian beam) can be observed.
The new OCT provides a cardiovascular OCT that does not require
blood removal and can observe the epivascular membrane. Since noblood removal is required, there is less risk for the patient and theequipment is easier to handle. In addition, since the resolution ishigher than that of IVUS, which is currently the mainstream, highly
accurate diagnosis and treatment are possible.
Since the new OCT has a high degree of invasion and highresolution, it enables non-invasive diagnosis in many medical fields
such as diagnosis of cancer progression and ophthalmology. Evenduring tumor resection surgery, the resected part can be monitored
and accurate and safe surgery can be performed. Furthermore, it ispossible to replace one part in the field of X-ray diagnosis, and there
is a possibility that the risk of exposure can be eliminated.

REFERENCES
1. D. Sakota and S. Takatani, “Quantitative analysis of optical properties of flowing blood using a photon-cell interactive Monte Carlo code: effects of red
blood cells’ orientation on light scattering”, Journal of Biomedical Optics 17(5), 057007 (May 2012)
2. A. Curatolo, et al. “Quantifying the influence of Bessel beams on image quality in OCT” Sci. Rep. 6, 23483; doi: 10.1038/srep23483 (2016).
3. M. Friebel, et al, “Influence of oxygen saturation on the optical scattering properties of human red blood cells in the spectral range 250 to 2000 nm”, J.
of Biomedical Optics, 14(3), 034001 (2009)