1. Biomedical Engineering Medical Imaging
BTY100-Lec# 6.1
Biomedical Engineering
Medical Imaging

2. OUTLINE Introduction to Biomedical Engineering Medical Imaging:
X-Ray Radiography
CAT Scan
Ultrasonography

3. Biomedical Engineering
is the application of engineering principles and design concepts to medicine and biology for healthcare purposes
It combines the design and problem solving skills of engineering with medical and biological sciences to advance:
healthcare treatment, including diagnosis, monitoring, and therapy

4. Biomedical Engineering
Includes:
Medical imaging
Implants
Bionics

5. Medical Imaging
is the technique of creating visual representations of the interior of a body for clinical analysis and medical intervention.
seeks to reveal internal structures hidden by the skin and bones, to diagnose and treat disease.
Commonly used techniques:
X-ray radiography, CT Scan, Medical ultrasound etc.

6. X-ray Radiography
is an imaging technique that uses electromagnetic radiation other than visible light, especially X-rays, to view the internal structure of the human body.
Basic Principle:
an x-ray beam is passed through a patient to a piece of film or a radiation detector, producing an image.
Different soft tissues allow different penetration of x-rays: depending on tissue density; the denser the tissue, the whiter the image
Lung: Less dense, more x-rays pass through-Black image.
Femur: Thick bone, lesser X-rays pass through: Whiter image

7. X-ray Radiography
To create the image, a heterogeneous beam of X-rays is produced by an X-ray generator and is projected toward the object.
A certain amount of X-ray is absorbed by the object, which is dependent on the particular density and composition of that object.
The X-rays that pass through the object are captured behind the object by a detector.
The detector can then provide a superimposed 2D representation of all the object's internal structures.

8. COMPONENTS X-ray generator :
X-rays are produced by an electron beam (emitted from heated cathode filament) that is accelerated to a high speed and strikes a target.
The electrons are then focused and accelerated by an electrical field towards an angled anode target.
The point where the electron beam strikes the target is called the focal spot.
Most of the kinetic energy contained in the electron beam is converted to heat, but around 1% of the energy is converted into X-ray photons.

9. COMPONENTS
Image detection system: a range of detectors have been used to collect images including:
Photographic film

10. Image detection system
Scintillator Detector:
X-rays not absorbed by the target strike, a layer of scintillating material that converts them into visible light photons.
These photons then strike an array of photodiodes which converts them into electrons that can activate the pixels in a layer of amorphous silicon.
The activated pixels generate electronic data that a computer can convert into a high-quality image of the target, which is then displayed on a computer monitor

12. Two forms of radiographic images
Projection radiography : are often used to determine the type and extent of a fracture.
With the use of radio-opaque contrast media, such as barium, they can also be used to visualize the structure of the stomach and intestines

13. Two forms of radiographic images
Fluoroscopy: produces real-time images of internal structures of the body in a similar fashion to radiography.
employs a constant input of x-rays, at a lower dose rate and real time image is produced using TV camera.
used in image-guided procedures when constant feedback during a procedure is required.

15. Tomography 
refers to imaging by sections or sectioning, through the use of any kind of penetrating wave.

16. Computed Tomography Scanning
Basic Principle: uses computer-processed x-rays to produce tomographic images (virtual 'slices') of specific areas of the scanned object.

17. Working CT Scan A CT scanner looks like a big, square doughnut.
Inside the covers of the CT scanner is a rotating frame which has an x-ray tube mounted on one side and the detector mounted on the opposite side.
A fan beam of x-ray is created as the rotating frame spins the x-ray tube and detector around the patient.
As the x-ray tube and detector make this 360° rotation, the detector takes numerous snapshots.
Typically, in one 360° lap, about 1,000 profiles are sampled.
Profiles are then superimposed to generate a 3-D images.

18. CT Scan
Advantages:
High-contrast resolution: differences between tissues that differ in physical density by less than 1% can be distinguished
Data from a single CT imaging procedure can be viewed as images in different axial planes. This is referred to as multi-planar reformatted imaging
Disadvantage:
Uses high ionizing radiations hence dosage must be properly monitored.

19. ULTRASONOGRAPHY
Ultrasound is an oscillating sound wave with a frequency greater than the upper limit of the human hearing range(20 kilohertz).
Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz.
These sound waves are reflected by tissue to varying degrees to produce images

20. ULTRASONOGRAPHY
commonly associated with imaging the fetus in pregnant women.
Other important uses include imaging the abdominal organs, heart, breast, muscles, tendons, arteries and veins.

21. Working Ultrasound images (sonograms) are made:
by sending a pulse of ultrasound into tissue using an ultrasound transducer (probe).
The sound reflects and echoes off parts of the tissue
this echo is recorded and displayed as an image to the operator.

22. COMPONENTS A basic ultrasound machine has the following parts:
Transducer probe - probe that sends and receives the sound waves
Central processing unit (CPU) - computer that does all of the calculations and contains the electrical power supplies for itself and the transducer probe
Transducer pulse controls - changes the amplitude, frequency and duration of the pulses emitted from the transducer probe
Display - displays the image from the ultrasound data processed by the CPU

24. Ultrasonography Advantages: Disadvantage
It is very safe to use and does not cause any adverse effects.
It is also relatively inexpensive and quick to perform.
The real time moving image obtained can be used to guide drainage and biopsy procedures. 
Disadvantage
that it can not capture detailed images.

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