إعداد : أ. بلسم فهد صوفي 1 Ultrasound in Medicine Ch.3 Ultrasound pictures of the body

إعداد : أ. بلسم فهد صوفي2 -Are based on the principal of sonar. -The pulses frequency is ranging between (1-5) MHz. -Its average intensity of few m watts/cm 2. -Its mechanical work: -The types : -1- A-Scan (Pulsed scan). -2- B-Scan (2-d view). -3- M-Scan (Motion scan) -4- Doppler effect.

إعداد : أ. بلسم فهد صوفي3 First: A-Scan (Pulsed scan)  It’s used to obtain the diagnostic information about the depth of the structure in the body by : Measuring the time required to receive the echoes from the various from the body.  The transducer is fixed.

إعداد : أ. بلسم فهد صوفي4

5  The bases of use US in Medicine is: The partial reflection of sound at the surface between two media that have different acoustical properties.  The amount of reflection depend on: 1- The difference in the acoustical impedances of the two media The orientation of the surface with respect to the beam.

إعداد : أ. بلسم فهد صوفي6 Problems of ultrasound echos ’ detection :  1-The echoes are very small signals, why?  2-The resolution : is the ability  2-The resolution : is the ability of the equipment to detect separate echoes from two objects close together.   In general, structures smaller than the wave length cannot be resolved. Since :   λ = v/ƒ  better resolution  If the ƒ sound has λ and allows better resolution than ƒ sound. The absorption The absorption. Small echoes weak reflection and the absorption of the soundly tissue.

إعداد : أ. بلسم فهد صوفي7 Fig. (4.2): Weak echoes from deep structures can fee electronically amplified to make them more visible, (a) the transmitted pulse T produces a weak echo R on the CRT. (b) the amount of amplification Increases with time (or distance), (c) The amplification Increases the size of the echo.

إعداد : أ. بلسم فهد صوفي8 Medical Application of A – Scan 1- Detection of Brain tumors (echoencephalography) A tumor on one side of the brain tends to shift the midline toward the other side The abnormal case : If a shift was > 3 mm,,, adult > 2 mm,,, children

إعداد : أ. بلسم فهد صوفي ophthalmology (daises in the eye). We usually use ƒ up to 20 MHz in the eye ? For 2 reasons : 1- better resolution 1- to obtain better resolution,,, since there is no bone to absorb most of the energy. absorption is not significant 2- The absorption is not significant,,, because the eye is small. The US can provide information about deeper regions of the eye the deeper regions of the eye like : Tumors, foreign bodies, and detachment of the retina.

إعداد : أ. بلسم فهد صوفي10 Second : B – Scan (Two-Dimensional View)   Is used: 1-To obtain two dimensional views of parts of the body. 2-To provide information about the internal structure of the body. 3-In diagnostic studies of (the eye, liver, breast, heart, and fetus). 4-To detect pregnancy as early as the fifth week and can provide information about (the size, location, and change with time) of a fetus.   Has the same principle of A-Scan except the transducer is moved.   Each echo produces a dot on the oscilloscope.  provide more information less risk  In many cases B-scans can provide more information than x-ray and they present less risk.

إعداد : أ. بلسم فهد صوفي11

إعداد : أ. بلسم فهد صوفي12  in:  large echoes appear brighter than weak echoes in: Grey – scale display  ,where the brightness is directly proportional to the size of the echo.   Its advantage : is successful in detecting tumors such as liver tumors.

إعداد : أ. بلسم فهد صوفي13 M – Scan (Motion Scan)  It  It combines certain features of the A-scan and the B- scan. The transducer is held stationary. the echoes appear as a dots.

إعداد : أ. بلسم فهد صوفي14   The places where the heart can be probed are quite limited because of poor ultrasound transmission through lung tissue and bone.

إعداد : أ. بلسم فهد صوفي15 Medical Application of M – scan : .  mitral valves.   Provide the information about the rate of closing and opening (motion) of the mitral valve is 72 mm/sec.   But in the abnormality case called mitral stenosis (a narrowing of the valve opening). The slope is reduced

إعداد : أ. بلسم فهد صوفي16 The Doppler Effect   Δf = f - f = ± f(u/v)   Where:   Δf is the frequency change due to the motion of the source or the listener.   f is the frequency of the sound source.   v is the velocity of sound.   u is the velocity of source or listener, and is the frequency change.

إعداد : أ. بلسم فهد صوفي17 Medical Application of Doppler effect 1- Measurement the velocity of blood.   Is used to measure the velocity of moving objects or fluids within the body such as the blood. This method to measuring blood flow doesn’t require surgery to implant measuring devices. Red blood cells in the arteries.

إعداد : أ. بلسم فهد صوفي18 2- Measurement of fetal heart rate.   is used to detect motion of the fetal heart.