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ULTRASOUND

DEFINITION

• A type of imaging test to examine the internal organs using very high frequency sound waves.
• Ultrasound or ultrasonography is a medical imaging technique that uses high frequency sound waves and their echoes. The technique is similar to the echolocation used by bats, whales and dolphins, as well as SONAR used by submarines.: sound navigation and ranging

SOUND  

 Sound is a mechanical form of energy

Sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid.

AUDIBLE SOUND

20Hz – 20000Hz human hearing sound

Lower 20Hz- infrasound

Higher 20000Hz – ultrasound

IMPORTANT POINTS

DIAGNOSTIC ULTRASOUND – Diagnostic ultrasound uses 1-20MHz frequency.

Wavelength is the distance between successive wave crest.

AMPLITUDE – distance between peak and midpoint of the wave or highest point of the wave

Period is the time taken for one complete cycle and is equal to 1/f. – 1 PERIOD

Frequency is the number of occurrences of a repeating event per unit of time. – DAY

ECHO – The reflection from tissue is called echo, which form the image.

Velocity is inversely proportional to compressibility and it depend on temperature of the medium. Inversely Proportional : when one value decreases at the same rate that the other increases.

• Velocity higher in bone and lower in gas
• Frequency do not change, but change of velocity may occur due to change of wavelength.

SPECKLE – Interference of scattered echoes from different site is called speckle.

In abdomen imaging, strong echoes arise from gas bubbles. Kidney, pancreas, spleen, and liver constitutes complex tissues containing scattering sites, gives rise to speckled texture. Bladder, blood vessels and cysts (fluids) have no internal structure, hence no echoes and appear as black.

Higher the frequency, greater the attenuation

A velocity of 1540m/sec is used as an average for body tissues.

Higher frequencies are more attenuated than low frequencies, resulting in increased SPL. This will degrade image resolution.

HISTORY

1794 – lazzaro spallanzani discovered non-audible sound. Echolocation in bat

1877 – pierre curie discovered piezoelectric effect

1917 – langevin produced ultrasound device using piezoelectric.

1942 – karl dussik investigates ultrasound transmission of the brain.

1958 – Dr. ian Donald obs/gyn.

1980 – real time ultrasound possible

1986 – first 3d image of foetus.

1990 – 3D and 4D ultrasound emerge.

PHYSICS OF ULTRASOUND

• The ultrasound machine transmits high-frequency sound pulses into your body using a probe.
• The sound waves travel into your body and hit a boundary between tissues (e.g. between fluid and soft tissue, soft tissue and bone).
• Some of the sound waves get reflected back to the probe, while some travel on further until they reach another boundary and get reflected.
• The reflected waves are picked up by the probe and relayed to the machine.
• The machine calculates the distance from the probe to the tissue or organ (boundaries) using the speed of sound in tissue (1,540 m/s) and the time of the each echo’s return (usually on the order of millionths of a second).
• The machine displays the distances and intensities of the echoes on the screen, forming a two dimensional image.

PRINCIPLE OF ULTRASOUND/ physics of ultrasound in short

• USE high frequency sound waves and their echoes.
• transmits high-frequency (1 to 5 megahertz) sound pulses into your body using a probe.
• Some of the sound waves get reflected back to the probe, while some travel on further until they reach another boundary and get reflected.

TO BE CONTINUE IN PART -2

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so here I uploaded part -1 and part -2 is uploaded tomorrow so read it and understand it

to be continue in part -2

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A Belgian priest named George Lemaitre firstly suggested the idea of big bang theory in age 1920s.
The actual beginning of everything may not be explain by Big Bang Theory.

13.8 billion years ago, an explosion occurs because of every speck of energy dense into a very tiny point called singularity. This explosion was beyond the imagination.
After this explosion, all the matter spread in all over surrounding directions with very high speed approximate speed of light. The temperature at that time was 1000 trillion degree Celsius.

Events after big bang-

After Big Bang, in initial three lakh years, all the matter was in plasma state. After this, the protons and neutrons combine together and form nuclei and then a complete atom.

The first atom formed after Big Bang was Hydrogen atom and then Helium by hydrogen’s fusion, then higher atoms.

The atoms combine and form small terrestrial bodies then stars, planets, galaxies and our universe.

The estimated numbers of atoms in the present universe are approximately 10⁷⁸ – 10⁸².

Expansion of universe–

The expansion of universe is the main evidence for the existance of big bang. According to some theories, the universe is still expanding after big bang. It is predicted by the light coming from other galaxies that the galaxies are moving far away from our galaxy (milky way).

According to planck’s observations the rate of expansion of universe is 67km/sec/megaparsec. But according to present understandings of universe it is 9% faster rate then planck’s prediction.

During big bang, the infrared light form. But now we observe these rays as cosmic microwaves.

According to some theories there are other universe like our universe called multiverse.

Our universe form after big bang and expanding, but after some billion years it would be contracted and again a big bang occurs. This cycle would be happen continually, called oscillating universe.

If we see the stars in space, it means we see the past of stars because light can take thousand years reach to earth from these stars.

Experiment related to big bang–

Physicists create conditions of big bang by a gigantic machine called Large Hadron Collider (LHC). The LHC is an 27km long underground tunnel in ring shape.

It comprises superconducting magnets to accelerate the particle (protons and heavy ions) inside the tunnel.

In LHC, two particles accelerated close to the speed of light. The accelerated particles collide and produce extreme energy. By these conditions, physicists understand that how big bang creates the universe.

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Total number of bones in the body – 206
Smallest bone in the body – stapes
Longest bone in the body – Femur
Smallest long bone in the body – Malleus
Most slender long bone in the body – Fibula
Largest flat bone in the body – Hip bone
Largest sesamoid bone in the body – patella
Most actively growing area of long bone – Metaphysis
Most vascular area of a long bone – Metaphysis
Largest nutrient artery in the body – Nutrient artery of Tibia
Commonest site of osteomyelitis in a long bone – Metaphysis
All long bone of body lie vertically except – Clavicle
All the bones in the body are made up of both compact and spongy bone except – Inferior Nasal concha
Commonest site of bone marrow aspiration – Manubrium sternum in adult and iliac crest in children.
Most abundant cartilage in the body – Hyaline cartilage
Most durable cartilage in the body – Fibro cartilage
Commonest congenital anomaly due to defective endochondral Ossification – Achondroplasia
Most common site of accessory bones – Lambdoid suture of skull
All the long bones in the body follow low of Ossification except – Fibula
Commonest congenital anomaly due to defective membranous Ossification – Cleidocranial dysostosis
Largest hyaline cartilage in the body – Thyroid cartilage of larynx
Largest yellow elastic cartilage in the body – Cartilage of Ear auricle

The rings of Jupiter, Uranus, and Neptune are made of dust, very tiny pieces of rock, and ice. The rings of Saturn are made of large pieces of ice.

We don’t know for sure where these rings came from. In some cases, the rings have come from dust knocked off of the planets’ moons by meteorite bombardment, but some of them might have come from moons torn apart by the planet’s gravity, or they could have formed as the planets formed.

Saturn’s rings are the most magnificent; they are bright, wide, and colourful. Uranus has thirteen dark rings around it, and Neptune’s rings are also dark, but contain a few bright arcs.