advanced topics in biomedical engineering

ADVANCED TOPICS IN BIOMEDICAL ENGINEERING

By: Dr. Sohail Khalid

Electromagnetic Wave Based Biomedical Applications

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Presentation Intent

Introduction

Electromagnetic Spectrum

Electromagnetic waves based biomedical applications

RF sensors for biomedical applications

General discussion on current and future research

Brain storming on new ideas

Question answers

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INTRODUCTION

Hybrid research environment

Biology and Engineering Biomedical Engineering

Scope of biomedical engineering

EM Wave propagation

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ELECTROMAGNETIC SEPECTRUM

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Electromagnetic Waves Based Biomedical Applications

X-rays

Computer Tomography (CT) Scan

Magnetic Resonance Imagining (MRI)

Positron emission Tomography (PET) Scan

Ultrasound Imaging

Doppler ultrasonography

Sonar communication

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X-rays

X-rays are generated from firing high speed electrons from cathode onto anode in a tube.

Patient is placed between X-ray tube and silver halide film

X-rays passed through the body are absorbed in direct proportion to tissue density

X-rays penetrating the body strike the silver halide film and turn it dark

The more x-rays that penetrate, the darker the area inscribed on the film

Bones & metal absorb or reflect X-rays in less amount so film is “lighter” or “more white”

Soft tissues allow more X-rays to penetrate so film is “darker”

Visualizing tissues of similar density can be enhanced using “contrast agents”

Contrast agents: dense fluids containing elements of high atomic number (barium, iodine)

Contrast agents absorbs more photons than the surrounding tissue so appears lighter

These contrast agents can be injected, swallowed, or given by enema

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electron beam generator

tungsten target metal

resultant X-ray beam

silver halide film

X-rays

X-ray View of a Gunshot

Wound (Bullet has

split into fragments)

X-rays

Classic X-ray view of “Lung Infiltrates” caused by Pneumonia.

Notice the increased “whiteness” close to the sternum

X-rays

X-ray view of broken ribs in an infant ….

……caused by child abuse. Specifically, by holding the baby by the chest and shaking him

violently.

X-rays


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The scanner device incorporates a moving table & a revolving X-ray tube

The table moves the patient back and forth through the revolving X-ray emissions

The X-ray emitter moves (revolves) in a 360 degree arc around the patient

Instead of film, the CT scanner collects emitted X-rays via a collector

This collector is called a SCINTILLATOR

Scintillator transforms X-ray’s into a proportionally strong electric current

The electric current is then converted into a number of images (“slices”)

Contrast dyes may be used for image enhancement

Tool of choice for most stroke cases

Normal CT scan (abdominal slice)


CT scan of ischemic stroke (gold arrow)


CT scan of Subdural Hematoma (Green Arrow)


Purple area

denotes

destruction of

normal brain

tissue which is

colored green

CT scan color enhancement


3-dimensional modeling using CT scan


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Magnetic nuclei are abundant in the human body (H,C,Na,P,K) and spin randomly

Since most of the body is H2O, the Hydrogen nucleus is especially prevalent

Patient is placed in a static magnetic field

Magnetized protons (spinning H nuclei) in the patient align in this field like compass needles

Radio frequency (RF) pulses then bombard the magnetized nuclei causing them to flip around

The nuclei absorb the RF energy and enter an excited state

When the magnet is turned off, excited nuclei return to normal state & give off RF energy

The energy given off reflect the number of protons in a “slice” of tissue

Different tissues absorb & give off different amounts of RF energy (different resonances)

The RF energy given off is picked up by the receiver coil & transformed into images

MRI offers the greatest “contrast” in tissue imaging technology (knee, ankle diagnosis)

cost: about $1450 - $2000

time: 30 minutes - 2 hours, depending on the type of study being doneOpen MRI

Closed (traditional) MRI scanner


Normal ACL

(note “darker” region indicating normality)

Grade 3 ACL tear

(note “lighter” region where the “darker” region used

to be. This indicates tissue disruption and

associated fluid buildup)


MRI view of the

same Ischemic

Stroke seen in

slide 15


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Positron Emission Tomography (PET) Scan

Device measures metabolism via the decay ofradioactive tracers in tissues with higher than normalmetabolic activity (such as cancer)

Patient is injected with FluorDeoxyGlucose/Oxygen 15.

Glucose bound to Fluorine 18 (radioactive)

Diseased organs & tissues process FDG at a higherrate than normal tissues making FDG concentrationhigher in diseased tissue

Positrons are emitted by FDG and collide withelectrons, emitting γ radiation

Radiation picked up by camera

Computer reconstructs the radioactivity into 3dimensional images of organ or area with higher thannormal FDP uptake

Takes about 2 hours

Results available to physician within 48 hours

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PET scan showing Alzheimers’s Disease


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PET Scan showing Non Hodgkins Lymphoma (Green Arrows) before &

after 6 months of chemotherapy


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Sound waves above 20 KHz are usually called as ultrasound waves. Sound waves propagate mechanical energy causing periodic vibration of particles in a continuous,

elastic medium. Sound waves cannot propagate in a vacuum since there are no particles of matter in the vacuum. The velocity of the sound in

Air: 331 m/sec; Water: 1430 m/sec Soft tissue: 1540 m/sec; Fat: 1450 m/sec

Ultrasound medical imaging: 2MHz to 10 MHz 2 MHz to 5 MHz frequencies are more common. 5 MHz ultrasound beam has a wavelength of 0.308 mm in soft tissue with a velocity of 1540

m/sec.

Ultrasound Imagining

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Ultrasound Imagining

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Doppler Ultrasonography

Doppler ultrasonography is a non-invasive diagnostic procedure that changes sound waves into an image that can be viewed on a monitor.

Doppler ultrasonography can detect the direction, velocity,and turbulence of blood flow.

It is frequently used to detect problems with heart values orto measure blood flow through the arteries.

Specifically, it is useful in the work up of stroke patients,in assessing blood flow in the abdomen or legs, and inviewing the heart to monitor carotid artery diseases.

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Sonar Communication

Communication using sound waves.

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RF sensors for biomedical

Non-invasive disease diagnose/healing

Microwave devices for disease diagnose

Electromagnetic therapy

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Electromagnetic and Oncology: The Future

Scientists are discovering breakthrough in treating cancerous tumours by using low-intensityelectromagnetic fields.

Patients taking part in the clinical trials were given a spoon-like antenna told hold in their mouths whichthen delivered the magnetic fields to their bodies.

A small number who were treated three times a week showed significant improvements. Some of the tumours shrank and others stopped growing, while healthy cells in the surrounding tissue

were unaffected. A number of patients with liver cancer took part in the trials, some of which saw a significant

improvement. In certain cases it affected the cancers ability to grow and in some cases the tumours began to shrink

while others stopped growing. The surrounding cancer cells were also unaffected by the treatment, which can be tolerated for long

periods This is just the beginning a long way to go….

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Terahertz Systems for Medical Imaging

A break through in exploiting electromagnetic waves has potentially opened the way for more advancedmedical diagnosis.

T-rays are already in use in airport security scanners, prototype medical scanning devices and inspectroscopy systems for materials analysis.

They can also sense molecules such as those present in cancerous tumors and living DNA, since everymolecule has its unique signature in the THz range, the journal Nature Photonics reports.

Or detect explosives or drugs, for gas pollution monitoring or non-destructive testing of semiconductorintegrated circuit chips, according to Agency for Science, Technology and Research (ASTAR), Singapore,and Imperial College London.

Current T-ray imaging devices are very expensive and operate at only a low output power, since creatingthe waves consumes large amounts of energy and needs to take place at very low temperatures.

Materials science researchers have made T-rays into a much stronger directional beam than waspreviously thought possible, at room-temperature conditions.

Research co-author Stefan Maier, a visiting scientist at ASTAR and professor of physics at ImperialCollege, said: “T-rays promise to revolutionize medical scanning to make it faster and more convenient,potentially relieving patients from the inconvenience of complicated diagnostic procedures and thestress of waiting for accurate results.”


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Facilitating Diagnoses of Heart Disease and Ear Infections

Tiny devices are being micro machined from silicon that may make diagnosing and treating coronary artery diseases easier.

The devices can be inserted into one-millimeter-diameter catheters to image the arteries of the heart in three dimensions at high resolution using high-frequency ultrasound waves.

The ability to integrate electronics on the same silicon chip is key for successful implementation of cost-effective, flexible catheter- based imaging arrays to reduce the number of cables and electronic interference noise.

The system boasts a more compact design and three-dimensional imaging capability for guiding cardiologists during interventions, such as those for completely blocked arteries. The technology also offers higher resolution than current intravascular ultrasound systems, which help diagnose vulnerable plaque, a leading cause of heart attacks.


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Improving Sense of Touch While using a cane can improve balance, wearing a glove with a vibrating fingertip might improve sense

of touch. Georgia Tech researchers are designing such a device which is capable of improving common sensory

and motor skill tasks, including two-point discrimination, single-point touch, texture discrimination and grasp tests.

The device uses an actuator made of a piezoelectric material to generate high-frequency vibration. The actuator is attached to the side of the fingertip so that the palm-side of the finger remains free and the individual wearing the glove can continue to manipulate objects.

This device may one day be used to assist individuals whose jobs require high-precision manual dexterity or those with medical conditions that reduce their sense of touch,” said Jun Ueda, an assistant professor in the Woodruff School of Mechanical Engineering at Georgia Tech.

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Brain storming on new ideas

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