Laws of Thermodynamics Gibb’s Free Energy Applications of Ultrasound X-Ray imaging 14.12.11

Laws of Thermodynamics First law of thermodynamics: Law of conservation of energy Heat and work are forms of energy transfer. While energy is invariably conserved, the internal energy of a closed system changes as heat and work are transferred in or out of it. Second law of thermodynamics: Law of entropy The entropy of the universe tends to increase The entropy of any isolated system not in thermal equilibrium almost always increases. Isolated systems spontaneously evolve towards thermal equilibrium -- the state of maximum entropy of the system -- in a process known as "thermalization".

Third law of thermodynamics: The entropy of a system approaches a constant value as the temperature approaches zero. The entropy of a system at absolute zero is typically zero. Specifically, the entropy of a pure crystalline substance at absolute zero temperature is zero. Look at the video titled: Gibb’s free energy

Medical Applications of Ultrasound Ultrasound waves are very high frequency waves with short wavelengths. So they can be focused on small areas Ultrasonic flow meter Diathermy (Lithotripsy) Ultrasound imaging

Ultrasonic flow meter Ultrasound waves can be used to measure motion within a body One device for obtaining such measurements is the ultrasonic flow meter which produces ultrasonic waves that are scattered by blood cells flowing in the blood vessels The frequency of the scattered sound is altered by the Doppler effect depending on whether the blood is flowing away or towards the transducer The velocity of blood flow is obtained by comparing the incident frequency with the frequency of the scattered ultrasound

Diathermy and Lithotripsy Within the tissue the mechanical energy in the ultrasonic wave is coverted to heat With sufficient amount of ultrasonic energy, it is possible to heat selected parts of a patient’s body more efficiently and evenly then can be done with conventional IR lamps This treatment called diathermy, is used to relieve pain and promote heating of injuries Also used to destroy kidney and gall stones, technique called lithotripsy

Ultrasound imaging Ultrasound imaging is based on the same principle as the sonar used by bats and dolphins It involves the transmission of high frequency waves Ultrasound waves are aimed through a body part. It interacts with matter and can be absorbed, transmitted or reflected Sound waves bouncing against various tissues (echoes) can be used to identify how far away the object is (depth in the body), how large it is and how dense it is Conversion of echoes into electrical impulses by a transducer which are displayed as a pattern on an oscilloscope screen

Ultrasound imaging Soft tissue is mainly water with some solids added. Therefore, the wave propagation velocity varies little between different types of soft tissue, and is only slightly above that of water Table shows the sound velocity, mass density of various biological and non biological substances

Ultrasound imaging Because ultrasound waves cannot penetrate bone or air, they are especially useful in imaging soft tissues and fluid filled spaces Ultrasound is good in imaging a number of soft organ tissues such as heart, pelvis and reproductive organs, kidneys, liver, gall bladder, eye, thyroid, blood vessels and fetus

X-ray Imaging To make an X-ray image of human or animal bones, short X-ray pulses illuminate the body or limb, with radiographic film placed under or behind it As the X-rays pass through the hand, for instance they are weakened by the different density of tissues they encounter. Bone is very dense and absorbs or attenuates X-ray energy

X-ray Imaging Any bones that are present absorb most of the X-ray photons This is because bones have a higher electron density than soft tissues. Note that bones contain a high percentage of calcium (20 electrons per atom), potassium (19 electrons per atom) magnesium (12 electrons per atom), and phosphorus (15 electrons per atom). It is these differences in absorption and the corresponding varying exposure level of the film that creates the image that can show broken bones, clogged blood vessels, cancerous tissues and other abnormalities

X-ray Imaging The X-rays that pass through the flesh leave a latent image in the photographic film. When the film is developed, the parts of the image corresponding to higher X-ray exposure are dark, leaving a white shadow of bones on the film.

& BooksGood Websites http://www.physicsclassroom.com/ http://highered.mcgraw-hill.com/sites/0072495855/student_view0/ Books: Human Physiology: From Cells to Systems By Lauralee Sherwood Fundamentals of Human Physiology By Lauralee Sherwood

Good Books Biophysics An Introduction to Med. Biophysics by Prakash Books Available at CAMP, NUST Advanced Biophysics by S. K. Agarwal Basic Biophysics –For Biologist- by M.Daniel