Biomedical imagery in the 21st century-

a student’s guide through an a student’s guide through an information revolution.information revolution.

Information overload, or how to filter out bad input.

• Gauging today’s technology we must include the cumulative scientific history.– Biomedical Illustration, Camera Obscura,

Electromagnetic Spectrum, radiology, microscopy, The Kodakto name a few.

• What enables biomedical telecom- munications?– Graphic Arts, Optical Science, Motion Media,

Computer science/application.• Bioinformatics.

– Radiology, fundus photography, digital capture…» Sophisticated human interpretation.» Pattern recognition

OOpphthalmichthalmic pphotohotoggrarapphhyy• One branch of biomedical One branch of biomedical

photography.photography.Inclusive of one organ in human Inclusive of one organ in human physiologyphysiology..

– Incorporates insitu Incorporates insitu documentation of fundic documentation of fundic view human eye.view human eye.• Evolving technologies now utilize Evolving technologies now utilize nonnon

graphic arts and sciences emulsions graphic arts and sciences emulsions for optomechanical, computerized for optomechanical, computerized instrumentation.instrumentation.

– Including false color formats.Including false color formats.

Career springboard• Why immerse in such a

rapidly changing field?– Large numbers of

vacancies each calendar year.

• Positions throughout the US.

– Compensation rates of more cumbersome medical careers.

– Vast growth potential.

Future directions in ophthalmic imagery:

• Optical coherence tom- ography

• Ultrasound• Scanning lasers• Adaptive Optics

Photography 101• Origination of ophthalmic Origination of ophthalmic

photography:photography:• Illustration

– Possible subjective – Uses media of paper, colored

writing instruments, reflected light.

• Photography (writing w/light)– Sensitized film emulsion

» Implies precise reproduction– Chemical development– Exposure = illumination x time– Sensitometers:

densitometry/opacity» Uses several media formats

and display types, most notable reflected light (prints), transmitted illumination (slide/monitor).

– Biomedical photography

• Biologic likeness/ documentation of pre, post and insitu clinical changes, treatments, injuries…

– Research, microscopy, botany, zoology…

• Highly accurate reproduction of color flesh, anatomy, dye stains, chemical luminescence.

• Imagery used for treatment, education.

– Ophthalmic photography• Angiography-rapid

sequence of pictures /sketches of circulation over time.

• Slit lamp photography-high magnification of the ocular anterior chamber utilizing biomicro-scopy(optical sectioning) techniques

• Retinal mapping-documenting posterior/retinal area of human eye with precisely overlapped images. Often in stereo sequence.

• Imagery used for treatment, education.

The language of photography

-began 160 years ago.• The language of light.– Capturing

biomedical images demands understanding of photographic science:

• Light• Time• Sensitized

emulsions L.Nillson

Tradition of Photography

Daguerre 1839-plates of silver or silver copper.Talbot 1853

Light

Camera Silver Halide Crystals

The Science of Photography

• Can be divided into several separate, though somewhat interdependent, branches, each of which can be assigned to a special field of chemistry or physics. Thus, the preparation of the light-sensitive layer is essentially a colloidal chemical operation. The action of light upon this sensitive layer is a photo-chemical process involving secondary physical and chemical processes.

Writing with Light• What composes light?

– How do you measure light?• Camera Systems

– 35mm Camera• Single-lens Reflex (SLR)

• Lenses– A lens does what?

• Lens characteristics: focal length, aperture/f-stops

Writing with Light• Shutter speed• Aperture, or f-stop

– Combining aperture settings with shutter speeds.

– Choosing an appropriate aperture/shutter speed combination.

• Film emulsions/CCD chip– Film speed and CCD speed– Resolving power

• Filters

Fundamentals

• The camera is mechanically, similar instrument as the eye. Composed of somewhat simple parts and principals.

• By controlling shutter speed-duration of time light strikes the film-we create a latent image.

Fundamentals• To calculate

exposure time, we factor film speed-or now the chip’s sensitivity to light.

• Lenses provide for focusing the Electro-Magnetic Spectrum wavelengths/rays of light.

Light=energy, energy we can see - we can

sense.• Energy is in transit.• Photography stores light, stores time.?• Any camera, or system is in a way a black box.• An optical system funnels the light to the black box.

Wavelengths• The

Electromagnetic Spectrum

• Light is the source– Composed of

radiant energy.

Response/reproductionObjective/subjective

• Film designed around reproducing image responsive to human visual system.

• Eye responsive to narrow portion of energy spectrum.– Eye capable of sensing

more variation of green than any other visible color.

• Cameras allow a controlled amount of illumination to film. Some have a connected flash.– 3 basics: focus, aperture, shutter speed.

• Camera uses lenses, filters, apertures or numeric values (combinations of sum).

• Fundus cameras have an amazing built in (axial) flash. An output control of illumination.

Ophthalmology and optometry

• The role of an ophthalmic photographer is support of the clinician and his patients.– Valued technician Valued technician

knows most tangents knows most tangents associated with their associated with their specialty. They then specialty. They then become sought out become sought out by clinician!by clinician!