SKGK – Session 23 – Topic: Medical Image (Answers) – Date: 28 April 2017
Answers of today’s session
1⃣ The binary representation of array of pixel elements of a two dimensional image is Digital image.
2⃣ 1. Fluoroscopy.
3⃣ The image whose intensity levels ranges from 0 to 255 is grayscale image.
4⃣ 1. RGB (Red, Green , Blue).
2. CYMK ( cye, yellow,magenta,black).
3. HSV (hue , saturation,values).
5⃣ Pixels are the smallest and functional unit of an image. They are also called as dots.
6⃣ The resolution can be enhanced using the image enhancement algorithms.
7⃣ The first medical imaging device is x ray invented after the invention of X rays by Wilhelm Conrad roentgen.
8⃣ 1. X ray .
1. It is mainly used for hard tissues .
2. It gives 2d image with poor resolution.
3. It may harm if long exposure.
1. It used for hard as well as soft tissue.
2. It gives 3D images with better resolution.
3. It may not harm the patient.
🔟 Modes of ultrasound —
1. 2D mode
2. M – or motion mode.
3. Tissue Doppler.
4. Colour Doppler.
5. Advanced 4D Doppler.
Yash Gajanan Tiknayat
Final year Biomedical
Have a great day.😊😊
An image may be defined as two dimensional light intensity function f(x, y) where x and y denote spatial co-ordinate and the amplitude or value of f at any point (x, y) is called intensity or grayscale or brightness of the image at that point.
When x, y and the amplitude values of f all are finite discrete quantities, we call the image digital image.
Basic devices used are X-Ray, CT, MRI, Ultrasound.
Gray level refers to a scalar measure of intensity that ranges from black to grays and finally to white.
1. RGB model— used for color monitor & color video camera
2. CMY model—used for color printing
3. HIS model—-used for color image processing
4. YIQ model—used for color picture transmission
A digital image is composed of a finite number of elements each of which has a particular location or value. These elements are referred to as pixels or image elements or picture elements.
Resolution is defined as the smallest number of discernible detail in an image. Spatial resolution is the smallest discernible detail in an image and gray level resolution refers to the smallest discernible change is gray level.
X-rays are the oldest and most commonly used medical imaging technique. X-rays were discovered in 1895 and first used to image human tissue in 1896. X-rays use ionizing radiation to produce images of a person’s internal structure by sending beams through the body. These are absorbed at different levels depending on the density of the tissue.
CT scans, MRIs, PET scans.
🌹 X-Rays: X-rays are the most common and widely available diagnostic imaging technique. Even if a patient may need a more sophisticated test, they will often receive an X-ray first. X-rays use radiation to produce images of the body. When the rays pass through the body, dense objects—such as bones—appear white on the film.
X-rays are typically used to view and diagnose bone disease, degeneration, fractures, dislocations, infections and tumors. Though often used to examine skeletal structures, an X-ray can also be used to look at other internal structures, such as organs. In this case, the patient may given barium sulfate or dye to make the organs stand out more clearly in the X-ray image.
During an X-ray, the part of the body that is being looked at will be placed between an X-ray machine and photographic film. The machine then sends electromagnetic waves (radiation) through the body, reflecting the patient’s internal structures on the exposed film. Although the amount of radiation used for an X-ray is not considered dangerous, doctors will take certain precautions if the patient is pregnant.
🌹 CT Scans: A computed tomography scan, or CT scan, is similar to an MRI in that it produces detailed, high-quality images of the body. The CT scan is a more sophisticated and powerful X-ray that takes a 360-degree image of internal organs, the spine and vertebrae. Contrast dyes are often injected into the blood to make structures within the body more visible on the CT scan.
A CT scan produces detailed images of organs, bones, soft tissue and blood vessels and can be used to more easily diagnose cancer, heart disease, appendicitis, musculoskeletal disorders, trauma and infectious diseases. A CT scanner looks like a large box with a tunnel in the center. The patient lies on a table that slides in and out of the tunnel, while the scanner rotates around the patient, producing cross-section images of the body.
The technologist performing the scan sits in a separate room with computers on which the images are displayed. The technologist can speak with the patient using speakers and microphones. A CT scan is more expensive than an X-ray and is not always available at small or rural hospitals.
Several modes of ultrasound are used in medical imaging. These are:
🌹 A-mode: A-mode (amplitude mode) is the simplest type of ultrasound. A single transducer scans a line through the body with the echoes plotted on screen as a function of depth. Therapeutic ultrasound aimed at a specific tumor or calculus is also A-mode, to allow for pinpoint accurate focus of the destructive wave energy.
🌹 B-mode or 2D mode: In B-mode (brightness mode) ultrasound, a linear array of transducers simultaneously scans a plane through the body that can be viewed as a two-dimensional image on screen. More commonly known as 2D mode now.
🌹 C-mode: A C-mode image is formed in a plane normal to a B-mode image. A gate that selects data from a specific depth from an A-mode line is used; then the transducer is moved in the 2D plane to sample the entire region at this fixed depth. When the transducer traverses the area in a spiral, an area of 100 cm2 can be scanned in around 10 seconds
🌹 M-mode: In M-mode (motion mode) ultrasound, pulses are emitted in quick succession – each time, either an A-mode or B-mode image is taken. Over time, this is analogous to recording a video in ultrasound. As the organ boundaries that produce reflections move relative to the probe, this can be used to determine the velocity of specific organ structures.
🌹 Doppler mode: This mode makes use of the Doppler effect in measuring and visualizing blood flow
🌹 Color Doppler: Velocity information is presented as a color-coded overlay on top of a B-mode image
🌹 Continuous wave (CW) Doppler: Doppler information is sampled along a line through the body, and all velocities detected at each time point are presented (on a time line)
🌹 Pulsed wave (PW) Doppler: Doppler information is sampled from only a small sample volume (defined in 2D image), and presented on a timeline
Duplex: a common name for the simultaneous presentation of 2D and (usually) PW Doppler information. (Using modern ultrasound machines, color Doppler is almost always also used; hence the alternative name Triplex.)
🌹 Pulse inversion mode: In this mode, two successive pulses with opposite sign are emitted and then subtracted from each other. This implies that any linearly responding constituent will disappear while gases with non-linear compressibility stand out. Pulse inversion may also be used in a similar manner as in Harmonic mode; see below:
🌹 Harmonic mode: In this mode a deep penetrating fundamental frequency is emitted into the body and a harmonic overtone is detected. This way noise and artifacts due to reverberation and aberration are greatly reduced. Some also believe that penetration depth can be gained with improved lateral resolution; however, this is not well documented.
S. Chandra Prakash,
B.Tech. Biomedical Engg (BVRIT),
Hyderabad, Telangana, India.
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