1. Add for 2016
methylene blue
More radiology related and less cardiology related examples (GI??)

2. FRCR Part 1 Scientific Basis of Imaging
Optical Imaging
Mr John Saunderson, consultant medical physicist
CHH ext (76)1329
8/12/2015

3. FRCR Part 1 syllabus Scientific Basis of Imaging
4.22 Optical Imaging
Basic fluorescent imaging
Basic bioluminescent imaging
Difference between different optical imaging techniques
Penetration depths
Clinical applications
New subject for 2016 exam!

4. Basic fluorescent imaging

5. Fluorescent Imaging Administer dye Illuminate with excitation light
Into vessel to view flow, or
Into tissue for labelling (e.g. tumour)
Illuminate with excitation light
different dyes require different wavelengths
Source may be filtered white light or monochromatic laser
Observe fluorescence produced
may be visible to human eye
may require infrared camera to detect

6. Fluorescent Imaging

8. Light Sources

9. Imagers Usually CCD camera
May be direct view for surface or intraoperative procedures, or
Via endoscope

10. Benefits of Fluorescent Imaging
high contrast,
high sensitivity – can see extremely small concentrations
Gives molecular information: makes some (bio) chemistry spatially and temporally visible;
great tools for research: several possible imaging modes, most of which are unique;
cheap: the optical instrumentation and computing needed are quite simple;
easy to use: resembles classical staining.
Advantages over traditional stain include
Can see below surface
Can be useful to take image with and without excitation light.
A Review of Indocyanine Green Fluorescent Imaging in Surgery, JT Alander, et al, International Journal of Biomedical Imaging, Volume 2012, Article ID , 26 pages, doi: /2012/940585

11. Assessment of perfusion (intraoperative)
Endoscopic view

12. Examples of fluorescent dyes
Sodium fluorescein
Indocyanine green (ICG)

13. Sodium fluorescein
Blue light (490 nm) causes yellow-green light (525 nm) to be emitted
Main use ophthamology - angiography of retina and choroid
Dye injected intravenously
White light from a flash is passed through a blue excitation filter.
Unbound fluorescein fluoresce, emitting yellow-green light
A barrier filter blocks any reflected light so that the images capture only light emitted from the fluorescein.
Images are acquired for ten minutes depending on the pathology being imaged. The images are recorded digitally.

14. Fluoroscein Accidental Arterial Injection

15. Indocyanine green (ICG)
Sometimes used in ophthalmology
Growing use in surgery (ICGA = ICG angiography)
Excite with infrared (IR) light of nm
Causes IR light of nm to be emitted, so must be viewed using an IR camera
Infrared penetrates deeper than blue, so shows deeper lying blood vessels than fluoroscein
A Review of Indocyanine Green Fluorescent Imaging in Surgery, JT Alander, et al, International Journal of Biomedical Imaging, Volume 2012, Article ID , 26 pages, doi: /2012/940585

16. Indocyanine green angiography - rat

17. Assessment of perfusion (intraoperative)
Endoscopic view

18. Intraoperative fluorescence angiography for the evaluation of coronary artery bypass graft patency
allows confirmation of the location of the coronary arteries and assessment of bypass graft function during coronary artery bypass procedures.
System - a video camera and a laser diode
camera guided by a range-detector diode, is positioned a safe distance above the heart.
A small amount of ICG dye is then administered as a central venous injection.
This dye fluoresces when illuminated using laser energy and the images are recorded digitally.

19. Intraoperative Fluorescence Imaging System for On-Site Assessment of Off-Pump Coronary Artery Bypass Graft, K Waseda et al, JACC: Cardiovascular Imaging, vol 2 , no. 5, 2009

21. Molecular guided surgery
Zhu B, Sevick-Muraca EM. A review of performance of near-infrared fluorescence imaging devices used in clinical studies. Br J Radiol 2015;88:

22. Autofluorescence No dye used
Normal and tumour tissue which look the same under white light, may fluoresce differently under monochromatic light
e.g. blue light causes endobronchial lung cancer to glow green (tumour cells have less flavins, which absorb green light)

23. Figure 1. A, Autofluorescence imaging–negative (green) hyperplastic polyp.
B, Autofluorescence imaging–positive (dark purple) adenoma.
ASGE Technology Committee, Report on Emerging Technology - Autofluorescence imaging, Gastrointestinal Endoscopy Volume 73, No. 4 : 2011

24. Basic bioluminescent imaging

25. Basic bioluminescent imaging
A non-invasive imaging modality widely used in the field of pre-clinical oncology research.
Main chemical used is firefly luciferase
Chemical reaction - excitation light not needed
luciferin + ATP → luciferyl adenylate + PPi
luciferyl adenylate + O2 → oxyluciferin + AMP + light
Low amounts of light emitted
Too low for direct viewing
Sensitive camera needed
The luciferase gene can be cloned and spliced into target DNA of specific cells.

26. Penetration depths

27. > 1400nm Infrared B
IRA
Red
Orange
Yellow
Green
Blue/indigo/violet
Ultraviolet A
UVB
UVC
i.e. infrared penetrates deeper, etc.

28. Optical Radiation Safety (Not part of FRCR syllabus)
Control of Artificial Optical Radiation at Work Regulations 2010
Where there is a reasonably foreseeable risk to eyes or skin from optical radiation
Risk Assessment
Assess whether Exposure Limit Values (ELV) exceeded

32. MUST HAVE THE CORRECT EYEWEAR FOR PARTICULAR LASER DEVICE BEING USED
Laser safety classes
Class 1 – safety
Class 2 – blink reflex protects
Class 3R - blink reflex probably protects
Class 3B – direct beam or via mirror surface can damage eyes
Class 4 – even reflected beam from a matt surface could damage eyes. Might damage skin. Might cause fire.
MUST HAVE THE CORRECT EYEWEAR FOR PARTICULAR LASER DEVICE BEING USED
MHRA Guidance: Lasers, intense light source systems and LEDs, 2015

33. (Note, both above printed out and put in my filing cabinet under FRCR
Possible references
An introduction to molecular imaging in radiation oncology: A report by the AAPM Working Group on Molecular Imaging in Radiation Oncology (WGMIR)
Optical Biopsy: A New Frontier in Endoscopic Detection and Diagnosis
(Note, both above printed out and put in my filing cabinet under FRCR

34. End