Attachable Micro-endoscopy System to Conventional Microscope for

Live Mouse Organ Imaging using 4f Configuration

Yoon Sung Bae

1,2

, Jae Young Kim

and Jun Ki Kim

1,2

Biomedical Engineering Research Center, Asan Institute for Life Science, Asan Medical Center, Seoul, Korea

University of Ulsan, College of Medicine, 88, Olympic-ro, 43-gil, Songpagu, Seoul, Korea

Research Institute for Skin Imaging, Korea University Medical Center, Guro2-dong, Guro-gu, Seoul, Korea

Keywords: Micro-endoscopy, Confocal Endoscope, Confocal Endoscopy, GRIN Lens.

Abstract: The Micro-endoscopic technology combined with optical imaging system is essential for minimally invasive

optical diagnosis and treatment in small animal disease models. Thus, the high resolution optical probe is

required to achieve high resolution imaging. However, the optical imaging system requires highly precise and

advanced technologies which are the main reasons for increasing system cost. Advancements in micro-optics

and fiber optics technology have paved way in supporting compatibility among optical components. By

providing compatibility between endoscopic system and existing conventional imaging equipment such as

macro- or micro-scope, we could achieve in not only carrying out the high quality micro-endoscopic image

procedure, but also reducing prices of the imaging system. The proposed system could be widely useful in the

field of further biological study of animal disease model.

1 INTRODUCTION

For the basic biology and preclinical study, the

experimental animal study is widely accepted for

secure confirmation the biological hypothesis.

However, the observation methods for in vivo

monitoring inside of the experimental animal are

very limited. Micro-endoscopic technology makes it

possible to visualize the inner cells and organs in

small animal with in-vivo and minimal invasively.

As the technology of the optical fiber and micro-

optics are developed, it has become essential

equipment for optical imaging diagnosis and

treatment in small animal disease models.

Recent advancement in micro-optics and fiber optics,

the miniaturized optical endoscopy probe, such as

GRIN lens assembly or fiber-bundles is utilized in

the micro-endoscope. In addition to the technology,

the high-resolution optical microscopy system is

also required for micro-endoscopes to achieve high-

quality imaging.

One of the widely used micro-endoscopy imaging

system is the confocal endoscope which enables us

high-contrast and high-resolution, real-time imaging

by taking advantage of the confocal system.

Comparing with other commercial devices from

Karl Stortz, Mauna Kea Technologis and Olympus,

the confocal endomicroscopy has higher resolution

and enables minimum invasive. At the same time,

the confocal fluorescence system allows optical

sectioning of thick tissues. However, its highly

precise micro-optical imaging system results in

increasing system cost. Besides, conventional

imaging microscopy from Leica, Zeiss and Olympus

etc. has limited working space and this is major

reason why the experimental mouse study could not

extend their applications into in vivo or live status.

In this work, the attachable micro-endoscopy system

is assembled based on commercialized confocal

fluorescence microscope by attaching the additional

optical components consist of 4f optical system,

which relays the light path from the microscope to

the endoscopy probe maintaining the optical

properties of the microscope. That expands the

capability of the microscope, not only in-vitro, but

also in-vivo imaging as well. The micro-sized triplet

GRIN(Graded-Index) lens probe is utilized to be

inserted into the body of the small animal placed on

motorized translation stage. The colon and pancreas

cells of mice are visualized by using the

implemented system for further biological study of

animal disease model.

Bae Y., Kim J. and Kim J.

Attachable Micro-endoscopy System to Conventional Microscope for Live Mouse Organ Imaging using 4f Conﬁguration.

DOI: 10.5220/0006101001370140

In Proceedings of the 5th International Conference on Photonics, Optics and Laser Technology (PHOTOPTICS 2017), pages 137-140

ISBN: 978-989-758-223-3

137

Figure 1: Illustration of the attachable micro-endoscopic system. (a) Junction part. (b) Relay optics part. (c) Endoscope

holding part.

2 DESIGN OF ATTACHABLE

MICRO-ENDOSCOPE SYSTEM

2.1 System Configuration

Fig. 1. shows the schematic illustration of the

attachable micro-endoscopy system which consists

of three parts, which are junction, relay optics and

endoscope holding part.

Junction part depicted in Fig. 1. (a) connects the

microscope to the endoscope for transmission of

lights between the microscope and the endoscope

probe. It is designed to be installed to the nosepiece

of the microscope and rotated for compatibility of

both upright and inverted microscope. The mounting

adapter in the junction part is designed to accept the

various threads of major microscope manufactures

such as Leica, Zeiss, nikon and Olympus upright /

inverted microscope etc.

The illumination light from the microscope is

reflected by the mirror in the junction part and

passes through the relay part. Then the relay part

delivers the light to the endoscope probe as shown in

Fig. 1.(b).

The delivered light is focused on the endoscope

probe by the additional objective lens inside the

endoscope holding part, shown in Fig. 1. (c).

Emission light from the sample goes back through

the attachable micro-endoscopy system then, makes

the images of the sample by the microscope. In order

to compensate the imaging wobbling during

rotational sample scanning process, the wobble stage

is built in the holding part. The distance between

endoscope and objective lens can be controlled using

Obj. Lens Z stage in Fig. 1. (c).

2.2 4f System for Light Delivery

In order to deliver the lights between the microscope

and the probe of the endoscope, the 4f optical system

is constructed in the relay optics part as shown in

Fig. 2.

Figure 2: 4f optical relay system consists of two lens and

mirror.

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Figure 3: (a) Triplet sideview GRIN lens probe; The triplet GRIN probe consists of two imaging lens and relay lens with

micro-prism . (b) Micro-Endoscopy experimental setup combined with conventional confocal upright microscope.

It extends the beam path of the microscope to the

probe without loss of the lights power and changing

in the properties of the microscope. The system is

utilized two lenses with same focal length, f . Those

are distance 2 f each other and the objective mount

and objective lens are placed on the each sides of the

system apart from f . It is well-suited for beam

scanning microscopes such as confocal microscopes

in which the endoscopy is attached in our study. The

focal plane of the image is adjusted by translating

the axial position of the objective lens.

2.3 Endoscopy Probe and Complete

System

Triplet GRIN lens is used as the endoscopy probe in

this micro-endoscopy system, which is connected

the endoscope holding part. It should be noted that

the other types of endoscopy probe can be joined

this system such as flexible fiber-bundles. Fig. 3(a)

shows the triplet GRIN lens probe of side-view in

which angled mirror prism is adhered on the tip of

the imaging lens. The laser beam from the

microscope goes through the probe then, forms a

focal spot in front of the prism, which scans the

sample. The probe is inserted in the body of the

animal to scan the cells in the organ. The emission

light from the sample is collected by the probe and

goes back to the microscope.

There are several kinds of probe diameter from

0.35mm to 2.8mm. However, the probes of

0.35~1.0mm are mostly used for usual live mouse

imaging, since minimum invasiveness is very critical

in in vivo imaging. For the front-view probe, the

probe has no prism on the tip and this probe is more

appropriate for abdominal imaging for most organs.

Thus, front-view probe is more appropriate for

imaging most visceral organs such as liver, spleen,

kidney and so on,. For the gastrointestinal and

respiratory tracts such as colon, esophagus, trachea

and so on, side-view probe is more appropriate.

Thus, based on experimental purposes and directions,

proper probes types, diameter and length should be

chosen.

Fig. 3. (b) shows the attachable micro-endoscopy

system built on the commercialized upright confocal

microscope. The motorized translation stage is

utilized to place the sample animal and scan the

sample laterally. The micro probes are inserted into

probes hole and fixed on endoscope holder. The

complete micro-endoscopy combined with the

confocal microscopy is applied for in-vivo

fluorescence cellular imaging of internal organs in a

mouse. As a result, the experimental space has

enlarged and system costs are reduced.

3 EXPERIMENTAL RESULTS

The measured lateral and axial resolution of the

attachable micro-endoscopy system are 1μm and

10μm, respectively within 300μm of field of view,

Attachable Micro-endoscopy System to Conventional Microscope for Live Mouse Organ Imaging using 4f Conﬁguration

139

when diameter of 1mm probe is used. That shows

sufficiently high-resolution of the system for

application of cellular imaging of mouse. The

optical penetration depth of a GRIN probes is

limited to about 100μm in most organ tissue.

Fig. 4 shows the images of the cells in anesthetized

mouse organs taken by our system. We visualized

the mouse colon vasculature image after Acridine

Orange IV injection. Fig. 4. (a), and (b) are the

fluorescence image of mouse clone which clearly

shows the single cells in the organ. By inserting

front-view probe into live MIP+ mouse pancreas, the

pancreatic islets GFP cells are imaged. Fig. 4. (c),

and (d) are the in-vivo images of pancreatic islets

GFP cell and, blood vessel of the mouse,

respectively.

(a) (b)

Figure 4: (a), (b) In-vivo images of mouse colon walls. (c),

(d) In-vivo images of pancreatic islets GFP cell, and

blood vessel of mouse, respectively.

4 CONCLUSIONS

In this paper, we present attachable micro-

endoscopy system combined with conventional

optical microscope. It features the compatibility with

the most microscope manufactures’ standards. The

developed attachable micro-endoscope system is

equipped to the conventional commercialized

confocal microscope for in-vivo cellular imaging.

The colon and pancreas cells of mice are visualized

by using the implemented system for further

biological study of animal disease model.

ACKNOWLEDGEMENTS

This work was supported by the Basic Science

Research Program [2014R1A1A2057773,

2015K2A7A1035896] through the National

Research Foundation of Korea (NRF) funded by the

Ministry of Science, ICT & Future Planning and by

a grant (2015-641, 2015-646, 2016-7212) from the

Asan Institute for Life Science, Asan Medical

Center, Seoul, Korea.

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