Medical Imaging

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Medical Imaging

  1. 1. ANNOUNCEMENTS First log submissions have now been graded. Those achieving full marks included: Logs within the word limit or less than 10% above. Overview of their understanding of the topics discussed and their own opinions – just simply what was taught. Clear evidence of having read material in addition to the slides – references etc. Clear evidence of having undertaken the practicals. Many also include a reflection / self learning / background reading section. Assignment progress section from now on. Tips:- include logs in a single word doc or better still use word press and publish online – be sure to reference sources to avoid copyright issues.
  2. 2. WEEK 4 PRACTICAL  If possible, bring along a pair of headphones.  Practical focuses on editing sound files using a program called Goldwave.
  3. 3. MEDICAL IMAGING AND BIOSIGNAL ACQUISITION Week 3
  4. 4. OVERVIEW  Healthcare Technologies encompass all IT solutions in healthcare ranging from software systems which support patient management to devices which support diagnosis and management of disease.  Today, we want to focus on those devices which are used for obtaining measurements from the human body to assist with detection or absence of disease.
  5. 5. HEALTHCARE TECHNOLOGY CATEGORIES  Human beings are very complex, consisting of muscle, bone, organs and transport vessels.  Healthcare technologies have emerged as a direct need for examining the human body to provide diagnosis and prognosis for a variety of different complex ailments.  Healthcare technologies can be used to examine the:  Nervous System  Cardiovascular System  Respiratory System  Skeletal System
  6. 6. CURRENT HEALTHCARE TECHNOLOGIES  What can we measure from the human body?  Physical Structure  Electrical Properties and Behaviors  Chemical Properties  Acoustics Note. We often want to look at things that are obvious on the outside of the body, like temperature. We look only at more invasive applications here.
  7. 7. PHYSICAL STRUCTURE  These are alterations observed in the physical structure of the body.  E.g. A broken bone or abnormal growth such as a tumor. http://upload.wikimedia.org/wikipedia/com mons/0/0e/Skeleton2.jpg
  8. 8. ELECTRICAL PROPERTIES AND BEHAVIORS http://4.bp.blogspot.com/_U3vE-zSyfog/SKO0hRTNLfI/AAAAAAAAAAo/7dVSorEwczI/s320/port_brain.jpg  Many of the body’s organs are controlled by OR generate electrical signals.  E.g. The brain and muscles, including the heart.  Changes observed in the typically produced signals often indicate changes to the physical / mechanical structure of the organs.
  9. 9. CHEMICAL PROPERTIES  When organs become damaged or experience shock or trauma they release chemicals into the body’s blood stream.  E.g. During a myocardial infarction (heart attack) the chemical troponin is released into the blood stream.  The presence of such chemicals or elevated concentrations of such chemicals can indicate potential problems with the body’s organs.
  10. 10. ACOUSTICS  The sounds generated by the body’s organs can be reveal problems.  Auscultation is the technical term given to listening to the internal sounds of the body, usually using a stethoscope.  Typically performed for examining the circulatory or respiratory system  i.e. heart or lungs.
  11. 11. PHYSICAL MEASUREMENTS  Many devices and techniques exist to measure the physical make up of the body.  Large portion of these devices are grouped under ‘medical imaging’.  Main purpose of these devices is to non-invasively produce images of internal aspects of the body:  Clinical rationale: examination, diagnosis, and prognosis.  Medical science: assist with the study and understanding of the anatomy.  Different Medical Imaging devices include:  X-ray  Magnetic Resonance Imaging (MRI)  Computed Axial Tomography (CAT) better known as CT  Ultrasound
  12. 12. X-RAY  Phrase coined in 1895 by a German Physicist.  Wilhelm Rontgen  Widely used approach which is based on the usage of electromagnetic radiation.  In diagnostic applications the X-rays are passed through the body and detected on a photographic plate or film.  More dense parts of the body absorb the x-rays while less dense parts of the body allow the x-rays to pass through.  This produces a shadow like image of the internal part of the body which has been x-rayed.
  13. 13. X-RAY  This approach can show up solid items such as bones or tumours.  Very cheap, fast and relatively safe.  Applications: Dentist, Broken bones, mammography  Organs / blood vessels can also be examined using contrast media to more effectively absorb the x-ray  Injected or swallowed. SOURCE http://www.davidlnelson.md/Xrays_normal_hand_PA.htm
  14. 14. X-RAY VIDEO DESCRIPTION http://video.about.com/orthopedics/How-Does-an-X- Ray-Work--.htm http://en.wikipedia.org/wiki/File:X-ray3.jpg
  15. 15. ARE X-RAYS SAFE?  X-rays can be harmful if exposed to for long periods.  Radiation sickness can occur  X-rays are a form of ionizing radiation. When normal light hits an atom, it can't change the atom in any significant way. But when an X-ray hits an atom, it can knock electrons off the atom to create an ion (electrically-charged atom)  Free electrons then collide with other atoms to create more ions.  An ion's electrical charge can lead to unnatural chemical reactions inside cells, such as the breaking of DNA chains, leading to mutations such as cancer.  Nevertheless, X-ray still safer than invasive surgery and therefore regarded as one of the most useful medical devices of all time.
  16. 16. COMPUTED (AXIAL) TOMOGRAPHY  A major drawback of X-Ray is that it can only represent the internal system on one axis at a time .  CAT scan or CT scan overcomes this drawback by capturing a series of 2D X-ray images which are processed to provide 3D projections.  CT used to separate anatomical structures at different depths.  The computer varies the intensity of the X-rays in order to scan each type of tissue with the optimum power.  Especially good for scanning bone structure!  Contrast materials are used to allow the viewing of some structures like vessels.  Images are typically rendered on a computer.
  17. 17. CT SCAN  CT uses x-rays but instead of passing the x- rays through the body from one angle the x- rays are passed into the body from numerous locations and angles.  With the aid of a special computer the resulting patterns can be captured and pieced together to form a cross-sectional image of inside the body.  This technique can also produce 3d images.  Excessive exposure to x-rays does produce a risk to the patient’s health.  This applies to both conventional x-ray machines and CT scans. Source http://www.radiology-equipment.com/instrumentpics/ACFFA27.jpg
  18. 18. CT SCAN – OVERCOMING THE 2D PERSPECTIVE Source: http://health.howstuffworks.com/cat-scan1.htm
  19. 19. CT SCAN VIDEO DESCRIPTION http://video.about.com/orthopedics/CAT-Scans.htm http://www.youtube.com/watch?v=Tx-0emi4m8s Source: http://health.howstuffworks.com/cat-scan2.htm
  20. 20. MAGNETIC RESONANCE IMAGING (MRI)  MRI works in a different way from X-ray.  This technique relies on a strong magnetic field (effectively a large magnet) and radio waves.  No metals allowed in an MRI room.  Small metal object such as paperclips or pens can be lethal!  Magnetic coding on Credit cards wiped!  Cardiac pacemakers!  Orthopaedics are typically ok  These waves can pass through the body and produce an image which represents a 2d slice of the body.  MRI can generate cross-sectional images in any plane.  These 2d slices can then be put together to produce a 3d image of what ever organ is under investigation.
  21. 21. MRI VIDEO DESCRIPTION  http://video.about.com/orthopedics/MRI.htm  http://www.youtube.com/watch?v=ctwXQ5xK4PU&NR=1
  22. 22. MRI (2)  Useful in the diagnosis of neurological, musculoskeletal, cardiovascular, and oncological (tumors) diseases.  An advantage of MRI over X-ray is that there is no reliance between soft and hard tissue so non-solid parts of the body can be imaged  E.g. the brain  Unlike CT, the entire scanner does not need to be rotated.  A further advantage is that MRI is deemed not to be as harmful.  Pregnant women not scanned.  Because MRI scanners consist of a large magnet, this approach is not always suitable to people who have some sort of metal inside their body.  For example, a pace maker  http://www.youtube.com/watch?v=_lBxYtkh4ts&feature=related
  23. 23. MRI (3)  MRI can cause claustrophobia.  MRI machines are VERY noisy. (http://www.youtube.com/watch?v=8oI9YnhPNcQ&NR=1)  Similar dbs to a jet engine.  Ear plugs and headphones usually worn.  Patient must remain VERY still during the examination.  20 – 90 minutes in duration.  Any movement requires the section to be rescanned.  Orthopedic implants can cause artifact if present in the area being scanned.  MRI machines are very expensive, therefore examination is expensive.
  24. 24. MRI (4) Source: http://en.wikipedia.org/wiki/ Magnetic_resonance_imaging Source: http://health.howstuffworks.com/mri5.htm Source:://health.howstuffworks.com/mri-pictures1.htm
  25. 25. MRI VS X-RAY VS CT SCAN  Xray more clearly shows the difference between soft and hard tissue.  MRI more clearly shows a better contrast between different types of soft tissue.  MRI contains no radiation (no known biological harm)  Noisy though and patients have to remain very still.  Patients with pacemakers cant be scanned using MRI.  Very obese people cannot be scanned in an MRI machine.  X-ray contains a minimal amount of radiation.  CT scan contains a considerable amount of radiation. Requires injection prior to SCANS.
  26. 26. ULTRASOUND  Ultrasound imaging is a process where sound waves are sent into the body and the reflection of these sound waves is measured.  The technique relies on the principle that tissues of varying density will reflect sound waves in a different way.  In most cases a hand held device (transducer) is placed against the skin to transmit and measure the ultrasound waves.  A gel is used to ensure that this device makes a good mechanical contact with the skin. http://www.nlm.nih.gov/medlineplus/ency/imagepages/18058.htm
  27. 27. ULTRASOUND (2)  It is very effective for imaging soft tissues.  The patterns of reflection of the sound from within the body can be converted into images and be displayed on a monitor.  Although ultrasound relies on measuring acoustics these are not sounds that are actively generated by the body (i.e. they are merely passed through the body from an external source – a transducer).  Very safe procedure
  28. 28. ULTRASOUND (3) – DIFFERENT TYPES Source: http://news.bbc.co.uk/1/hi/health/3846525.stm  The ultrasound that we have described so far presents a 2d image, or "slice," of a 2d object (fetus, organ).  Two other types of ultrasound are currently in use  3D ultrasound imaging  In 3D Ultrasound, series of 2D images are acquired by moving the probes across the body surface or rotating inserted probes.  The two-dimensional scans are then processed digitally to produce 3D models  3-D imaging provides enhanced view of organs.  Particularly beneficial for early detection of cancerous and benign tumors, and for visualizing a fetus to assess its development.  http://www.youtube.com/watch?v=-MJLPGjbX6o
  29. 29. ULTRASOUND (4) – DIFFERENT TYPES  Doppler imaging  Based on Doppler effect  Visualizing blood flow in various organs or a fetus  Moving objects reflect ultrasound waves at different frequency.  Higher frequency if object moving towards the probes and lower freq. if object moving away from probe.  Variance in frequency is proportional to speed of object.  Doppler ultrasound most used to measure rate of blood flow through the heart and blood vessels.
  30. 30. BIOSIGNALS…
  31. 31. BIOSIGNAL ACQUISITION  As stated various organs and systems within the body can produce or rely on electrical impulses and electrical activity.  There are many such systems within the body. Here we focus on some of the most commonly measured.  These include: Electrocardiogram (ECG) Electroencephalogram (EEG) Electromyogram (EMG) Electrooculogram (EOG)
  32. 32. ELECTROCARDIOGRAM (ECG)  The ECG is the result of measuring the electrical activity of the heart as projected from inside the body onto the body’s surface.  The heart is essentially a collection of muscles which rely on an electrical signal to make them contract and push blood out.  These electrical signals are generated and travel to the surface of the body each time the heart beats.
  33. 33. ECG (2)  The ECG is measured by placing electrodes in contact with the skin. Several recording configurations exist but the most common is the 12 lead ECG.  This approach records 12 signals and a clinician will view these and look for changes in the waveforms which might signal abnormality.  ECGs can be recorded when the patient is at rest or when the patient is exercising to assess different effects of physical activity on the heart. Normal Abnormal
  34. 34. ECG (3) http://arrhythmiacenter.idsutcliffe.com/Pt%20Resources%20Dx%20of%20Arrhythmias.htm http://www.corscience.de/en/medical-engineering/oemodm-solutions/odm-products/24h-holter-2-lead.html http://www.mdconsult.com/das/stat/images/imng/0c039bbb2reduced_us.jpg http://rudylab.wustl.edu/overview/index.htm http://www.bioeng.auckland.ac.nz/physiome/movies/movies_display.php?type_id=4 http://www.ecglibrary.com/norm.html http://www.medcatalog.com http://homepages.cae.wisc.edu/~bme300/ecg_trainer_s09/images/12lead.jpg
  35. 35. millivolts (mV) millivolts (mV)
  36. 36. ELECTROENCEPHALOGRAM (EEG)  The EEG is a measurement of the brain’s electrical activity.  Brain cells communicate by producing small electrical impulses.  Similar to the heart, the brain produces electrical patterns which can be measured on the scalp.  The measurement process involves putting numerous (16 – 25) electrodes on the scalp  these can be part of a cap like structure.  Like in the ECG the resulting signals can be analysed to look for abnormal patterns in brain activity.  It should be noted that the signal produced and the origin of the signal is very different between the EEG and the ECG.
  37. 37. EEG  In deep sleep the EEG pattern produces large slow waves.  When relaxing the waves being faster.  When active the EEG is described as being very dense with a low voltage and a high frequency which produce a fast wave
  38. 38. EEG (2)  The auditory brainstem response is the recording of signals from the brain in response to a form of external audible stimulus. Temporal representation of the ABR signals show clear differences between the waveforms with and without a response.
  39. 39. EEG (3)  EEG is commonly used to detect:  Presence and type of seizures (epilepsy, convulsions)  Cause of confusion  Effects of head injury  Tumors  Infections  Degenerative Diseases  Brain activity in coma  Brain activity during sleep (narcolepsy)  As with the ECG the recording of EEG is VERY safe.
  40. 40. EEG (4) http://archlab.gmu.edu/people/cbaldwi4/ARG_People.html http://people.brandeis.edu/~sekuler/eegERP.html http://www.umsl.edu/~neurodyn/projects/eeg.html
  41. 41. BRAIN COMPUTER INTERFACES (BCI)  In recent years EEG has been used to acquire brain activity for the purposes of controlling machines.  Every time we move, think, feel or remember our brain fires electrical activity.  By placing electrodes on the surface of the scalp it is possible to capture some of this electrical activity.  Some of the electrical activity is distorted as it passes through the brain tissue and bone of the skull.  Implantable electrodes in also an option.  Rationale  Sensory OUTPUT BCI can be used to control some external device or prosthetic.  An MRI can help with profiling the activity.  Computer Screen  Artificial limb  Sensory INPUT BCI can be used to ‘feed’ signals INTO the brain (implant) to bypass some damaged section of it.  Allowing a blind person to see!
  42. 42. BCI (2) - APPLICATIONS  Controlling external device with you mind.  Controlling an onscreen mouse via mental commands to assist with communication.  Severely disabled persons.  Controlling an artificial limb.  Often requires training – ‘imagine’ closing your fist or moving your arm.
  43. 43. BCI – APPLICATIONS (2)  Sensory input from spectacle mounted cameras to allow sight for blind people.  To date, only limited sights can be restored.  Basic shapes represented as a series of dots.
  44. 44. ELECTROMYOGRAPHY (EMG) (1)  EMG is the discipline that deals with the detection, analysis, and use of the electrical signals that emanates from the muscles. In the words of De Luca (1997)  “…it provides easy access to physiological processes that cause the muscle to generate force, produce movement and accomplish functions which allow us to interact with the world around us”  The origin of these signals is similar in principle to that of the ECG as the heart is in effect a muscle.  Nerves cells (Motor neurons) connect to our muscles from the spinal cord.
  45. 45. ELECTROMYOGRAPHY (EMG) (2)  The technique can be used to study muscle function and activity.  The EMG can be recorded by placing needle electrodes in the muscle or by placing (gel) electrodes on the surface of the skin.  The former provides a more specific measurement whilst the latter provides a more general picture of the operation of the muscles in the area under interrogation.
  46. 46. EMG - APPLICATION Figure 2.2 Amplitude and Frequency spectrum of the EMG signal Figure 5.5 Screen shot of Animation Program http://www.hhdev.psu.edu/atl ab/EMG.jpg Figure 5.4 Screen shot of Analysis Program
  47. 47. ELECTROOCULOGRAM (EOG)  EOG is a technique for measuring the resting potentials of the retina.  Electrode pairs are placed either above and below the eye or to the left and right of it.  http://www.youtube.com/watch?v=jJ2BKq0fadQ
  48. 48. ACOUSTIC MEASUREMENTS (1)  Sounds emanating from various organs can be measured.  The two organs which are most commonly interrogated in this way are the lungs and the heart.  Sounds from these organs are typically measured using a stethoscope.  The classical stethoscope consists of a chestpiece which is placed against the body. http://www.waldosworld.org/gall ery04/stethoscope.jpg
  49. 49. ACOUSTIC MEASUREMENTS (2)  Vibrations are picked up by this chestpiece and transmitted along a hollow tube to a set of ear buds.  When auscultating (listening to) the heart, doctors listen for heart murmurs, gallops and heart rate.  When examining the lungs, doctors listen for wheezes or crackles.  More recently electronic stethoscopes have been invented which use a sensor inside the chest piece (in some cases a microphone).  Information from this sensor can be processed and enhanced before being transmitted to a headset.  Noise reduction / filtering and signal enhancement.  Digitized sounds can be stored and shared.
  50. 50. CHEMICAL PROPERTIES  Changes in the conditions of various organs and body systems can also be reflected in chemical changes.  For example if muscles are damaged i.e. if muscle tissue dies, enzymes can be released into the blood.  A particular case where this is used as a diagnostic test is in the case of cardiac patients.  The heart can be considered as a muscular organ, and when someone has a heart attack, this muscle releases various chemicals into the blood.  One such chemical is troponin-t (a protein). This is often used to diagnose if someone has had a a heart attack.  Takes time to conduct test thus why ECG is so important.
  51. 51. SUMMARY o We have studied (briefly) how various signals / images can be measured from the body. o Changes in these signals allow a specialist to make a diagnosis. o We have thought exclusively about diagnostic applications. o There also the reverse of this where we push signals into the body: o Therapeutic radiography o Implantable devices o Cardiac pacemakers, defibrillators, vascular pumps
  52. 52. NEXT WEEK  Lectures – running!  Medical data  Processing  PACS  Security  Tutorial and Practical Sessions  Use this time wisely to work on your assignment!  3 hours.  This is a really good opportunity to produce a draft of your assignment.  Visit the library, do a literature review etc…  This should ensure that everyone is able to submit a good piece of work in week 7.

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