2. How do Bioengineers use light?
● Diagnose diseases & disorders
● Measure material properties
● Identify biological & material
surface structures
● Irradiate samples
● Chemically & thermally alter
samples
○ Initiate chemical reactions
○ Destroy ablation
○ Surgery
3. Biophotonics & Radiology
Other courses:
Bioelectricity
Biomolecular and Nanobiotechnology
Computational Nueroscience
Physical Electronics (ECE)
Introduction to Digital Processing (ECE)
Introduction to Signal Processing (ECE)
Light and Modern Optics (Phys)
Scanning and Transmission Electron
Microscopy and Microanalysis (Phys)
Interested in Radiology?
Bachelors in Radiological Science
Department of Health Sciences
Earn CT and MRI certificates
Dr. Gang Yao
BE 4770
Biomedical Optics
249 AEB
Dr. Shinghua Ding
BE 4570
Fluorescent Imaging
324E Dalton
Dr. Ping Yu
BE 4420
Intro Biomed Imaging
220 Physics Building
4. Light microscopy
● Invention largely attributed
to Zacharias Janssen in 1590
● Antonie van Leeuwenhoek
(1632–1723) is credited with
bringing the microscope to
the attention of biologists
● first to observe and describe single-
celled organisms, which he originally
referred to as animalcules,
● observations of muscle fibers,
bacteria, spermatozoa, and blood
flow in capillaries
5. The Great Debate: Particle or Wave?
Pierre Gassendi
1660
• First proposed
light was a particle
Christian Huygens
1678
• light is a wave
• speed of light is
finite
Sir Isaac Newton
1666 - 1675
• Light was made up
of different colors
• “Corpuscles” were
weightless particles
• Could explain
reflection
Young & Fresnel
1803
• double slit
experiments
• diffraction patterns
of light explainable
by waves
James Maxwell
1862
• Unified electric
fields and
magnetism
• Light is a form of
electromagnetism
Albert Einstein
1905
• Proposed wave-
particle duality
• Photoelectric
effect
6. Wave-Particle Duality
● Light is in small “packets” called photons
● Are massless, but have momentum and
energy
● Newton’s Law was incomplete
● Einstein came up with the equation:
○ E2
= P2
c2
+ m2
c4
1905
8. Measurements of Light
Intensity Polarization Coherence
measure of the intensity of
electromagnetic radiation. It is
defined as power per unit solid angle
property of waves that can oscillate
with more than one orientation
two waves sources are coherent if
they have a constant phase
difference and fixed frequency
9. Properties of Light
Diffraction Reflection Refraction
various phenomena which occur
when a wave encounters an
obstacle or a slit
change in direction of a wavefront at
an interface between two different
media
change in direction of a wave due to
a change in its transmission
medium.
11. Lasers
● Foundation was photoelectric effect
● Preceded by MASER (microwave) in
1953 by Charles Hard Townes
● LASER (Light Amplification by
Stimulated Emission of Radiation)
developed by Gordon Gould in 1959
● Three properties of Laser Light
● 4 classes of lasers based on
dangerousness
12. Applications of Lasers
● Cosmetic: removing tattoos,
scars, stretch marks,
sunspots, wrinkles,
birthmarks, and hairs
● Surgery: Laser scalpel,
Laser-Assisted in situ
Keratomileusis (LASIK),
dentistry
● Tissue ablation and tumor
removal
● Low-level laser therapy
(LLLT) for wound healing
13. Fluorescence
● Incandescence is light from heat (light bulb)
● Luminescence is "cold light"
● Fluorescence is a type of Luminescence
● Bioluminescence is traditionally chemiluminescence.
● Some organisms and minerals have natural fluorescence
● Particles that emit fluorescence are called fluorophores
● Used for labeling and detection of a biomolecules
● Helps us Identify cellular structures
● Can be either dyes or proteins (green fluorescent protein
GFP)
● Can insert DNA to code for fluorescent proteins
● Used in conjunction with light microscopy
14. Pulse Oximetry
● Invented in 1972
● non-invasive method for monitoring a
person's O2
saturation and heart rate
● uses 660nm and 910nm light
● Oxygenated (HbO2) and Deoxygenated
blood (Hb) absorb light differently
15. Magnetic Resonance Imaging
● Uses oscillating magnetic field applied at the
appropriate resonant frequency
● Rely on detecting a radio frequency signal emitted by
excited hydrogen atoms in the body (present in any
tissue containing water molecules)
● Contrast between different tissues is determined by the
rate at which excited atoms return to the equilibrium
state
● Used for neuroimaging (FMRI), cardiovascular,
oncology, liver and gastrointestinal, musculoskeletal
● May require contrasting agents taken intravenously
● Huge market for making devices that don’t contain
metal
16. X-ray computed (axial) tomography (CT/CAT
scan)
● Developed in 1952 by Herman Carr
● computer-processed x-rays to produce
tomographic images (virtual 'slices') of specific
areas of the scanned object
● able to image bone, soft tissue and blood vessels
all at the same time
● Compared to MRI:
○ costs less than MRI, higher resolution but poor
soft tissue resolution, less versatile, uses radiation,
faster
● Suited for bone injuries, lung and chest imaging,
cancer detection. Widely used on Emergency
Room patients, Where MRI is more for ligament
and tendon injury, spinal cord injury, brain
tumors.
17. Thermal Imaging
● Pricipally Black Body
Radiation, first described
by Balfour Stewart 1858
● Uses infrared light to
measure body temperature
● Common for measuring
healing process,
inflammation burn
imaging, fevers, early
breast cancer detection
18. Not just Light
● Pressure waves (sound)
○ Transducers
○ Piezoelectric
materials
○ photoacoustics
● Electrons & Neutrons
● Largely used in material
characterization
○ SEM, TEM, XPS
19. Ultrasound
● Oscillating sound pressure wave with a
frequency greater than the upper limit of
the human hearing range.
● performs very poorly when there is a gas
between the transducer and the organ of
interest
● Cheap, easy to use, provides live images,
good for soft tissue imaging
● Can determine tissue elasticity
● Difficult to Image bone
