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1. U l t r a s o und 7/19/2024 1

2. Wh a t i s So und ? M e c h a n i c a l a n d Lo n g i tu d i n a l w a v e s w a v e t h a t c a n tr a n s f e r a di s ta n c e u s i n g a m e d i a . Ca nn o t t r a v e l t h r o u g h V a c u u m . 2 7/19/2024

3. Wh a t i s Ultr a s o und ? 3 U l tr a s o un d i s a m e c h a n i c a l , l o n g it u d i n a l wave with a frequency exceeding the upper limit of human hearing, which is 20,000 Hz or 20 kHz. T y p i c a l l y a t 2 – 2 M h z. 7/19/2024

4. Hearing and Voicing Ranges T he human ear can detect sounds with frequencies between 20 Hz and 20,000 Hz. I nfrasound   Sound with frequencies below the human  hearing range   ultrasound sound with frequencies above the human  hearing range   is called . Humans are also able to produce sound by speaking. The range of frequencies that you can produce is your  voicing range  and for humans, this is from 85 Hz to 1,100 Hz. 7/19/2024 4

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6. B a s i c U lt r a so u n d P h ysics Velocity 6 Frequency Amplitude Wavelength 7/19/2024

7. Velocity 7 Speed at which a sound wave travels through a medium(cm/sec) Determined by density and stiffness of media S l o w es t i n a i r / g a s F a s t es t i n s o l i d s A v e r a g e s p e e d o f u l t r a s o u n d i n bo d y i s 1540m/sec 7/19/2024

8. Velocity N e a r F i e l d I m a g i n g 8 F a r F i e l d I m a g i n g T i ssu e s c l o s e r a p p e a r o n t o p a n d f a s t e r t h e w a v e s return T is s u e s f u r t h e r a p p e a r a t t h e bo tt o m & slo w e r t h e w a ves r e t u rn 7/19/2024

9. Frequency 9 N u m b e r o f c yc l e s p e r s e co nd Un i t s a r e H e r tz Ultrasound imaging frequency range 2-20Mhz 7/19/2024

10. Frequency Higher the freq Lower the penetration and Higher t h e r e so l u t i o n Low the freq higher the penetration and lower the resolution 10 7/19/2024

11. Wavelength D i st a n c e o v e r w h i c h o n e c yc l e o c c u r s 11 7/19/2024

12. V e l o cit y ( v ) , F r e q u e n c y ( ƒ ) , & W a v e l e n g th ( λ ) 12 G i v en a c o n s t a nt v e l o c i t y , a s f r e qu e nc y i n c r e a s e s w a v e l e n g t h d e c r e a s e s V = ƒ λ 7/19/2024

13. A m pli t u d e 13 The strength/intensity of a sound wave at any g i v e n ti m e R e p r e s e n t e d a s he i g h t o f t h e w a v e Decreases with increasing depth 7/19/2024

14. A m pli t u d e D e fi n e s t h e B r i g h t n e ss o f t h e i m a g e 14 I r re s p e c t i v e o f t h e F r e q t h e A m p r e m a i n s c o n s t a n t The Higher the Amp the brighter the image and the l o w er t h e m o re d a r k e r t h e i m a g e s R e t u r n i n g W a ves 7/19/2024

15. H o w U l tr a s o und W o r k s … 15 H o w d o e s a n u l tr a s o un d m a c h i ne m a k e a n i m a g e ? 7/19/2024

16. Applications Training for Service – Ravindran Padmanabhan 14 P i e z o e l e c tr i c E f f e c t o f Ultr a s o und 1 . E l e c tri c a l E n erg y c o n vert e d t o S o u n d waves 2 . T h e S o u n d w a ves a re ref l e c t ed b y ti s s ue s 3 . Ref le c t ed S o u n d w a ves a r e c o n ver t ed t o e le c t r i c a l s i g n a l s a n d lat e r t o I m a g e 7/19/2024 16

17. 15 P uls e - Ec ho M e tho d Ultrasound transducer produces “ p u l s e s ” o f u l t r a s o u n d w a v e s T h e s e w a v e s tr a v e l w i th i n the b o d y a n d interact w i th v a r i o u s t i s s u e s T h e r e f l e ct e d w a v e s r e t u r n to t h e tr a n s d u c e r and are processed by the ultrasound machine An i m a g e w h i c h r e p r e s e n ts t h e s e r e f l e c t i o ns i s f s o T r a i r nin g m f o r S e er v i d ce – R o a vin d n r a n P t a d m h a n e a b h a n m o n i t o r 7/19/2024 17

18. Reflection – – – O c c urs a t a bo un d a r y b e t w een 2 a d j a c ent t i s s u e s o r media The a mo unt o f r efl e c ti o n d epen d s o n d i f f e r e n ce s i n a co u s ti c i m p e d a n c e ( z ) bet w een med i a The ult ra s o und i ma g e i s f o rme d f r o m r efl ec t ed echoes Transducer Z = D e ns i t y x V e l oc i ty 19 7/19/2024

19. Scattering • • • R e d i r e c ti o n o f s o und i n s e v er a l d i r e c t i o n s Caused by interaction with small reflector or rough surface O n ly po r t i o n o f s o und w a v e r eturns to t r a n s d u c er 22 7/19/2024

20. N o t a l l t he s o und w a v e i s r e f l e c t ed , s o m e c o n t i n u es d e ep e r i n t o t he b o d y T hes e w a v es w i l l r ef le c t f r o m d e e p e r ti ss ue structures Transducer T r a n s m i s s i o n 23 7/19/2024

21. T he d e ep e r t he w a v e t r a v e l s i n t he b o d y , t h e w e a k e r i t b ec o mes T he a m p l i t ud e o f t h e w a v e d e c r e a s es w i t h i n c r e a s i n g d e p t h Attenuation 24 7/19/2024

22. G o a l o f a n U lt r a s o und S y s t e m 25 T h e u l t i m a te g o a l o f a n y u l tr a s o u n d s y s t e m i s to m a k e l i k e t i s s u e s l o o k a l i k e a n d un l i k e tissues look different. 7/19/2024

23. Acoustic Impedance R es o l v i ng c a p a b i l it y o f t he s y s t em a xi a l / l a t e r a l r e s o l uti o n s p a ti a l r e s o l u t i o n c o ntr a s t r e s o l u t i o n temporal resolution Beamformation s end a n d r e c ei v e P r o c es s i n g P o w er a bi l i ty to c a ptu r e , p r e se r v e a nd d i s pl a y t he i n f o r ma t i o n 26 Accomplishing this goal depends upon... 7/19/2024

24. A c o u s t i c Im pe d a nc e 27 • • • • The product of the tissue’s density and the sound velocity w i t h i n the t i ss ue Amp l i tu d e o f r eturni ng e c ho i s p r o p o r ti o na l t o the d i f f e r en c e i n a co u s t i c i mpe d a nce bet w e en the t w o t i s s u e s Velocities: Soft tissues = 1400-1600m/sec – Bone = 4080 – Air = 330 Thus, when an ultrasound beam encounters two regions of very different acoustic impedances, the beam is reflected or absorbed Cannot penetrate E x a m p le : so ft t issu e – b o n e i n t e r f a c e 7/19/2024

25. T y pe s o f R e s o lu t i o n Axial Resolution specifies how close together two objects can b e a l o n g t h e ax i s o f t he be a m , y e t s t i l l b e d ete c t ed a s t w o s e p a r a t e o b j ec t s f r eq u enc y ( w a v e l e n g t h) a f f e c t s a x i a l r es o l u t i o n 30 7/19/2024

26. T y pe s o f R e s o luti o n La t e r a l R e s o l ut i o n t h e a bi l i t y t o r es o l v e t w o a d j a c e n t o b j ec t s t h a t a r e p e r p e n d i cu l a r t o t he b e a m a x i s a s s ep a r a t e o b j ec t s be a m w i d t h a f f e c t s l a t e r a l r es o l u t i o n 31 7/19/2024

27. T y pe s o f R e s o luti o n 32 S p a t i a l R e s o l u tio n a l s o c a l l ed D e t a i l R es o l u t i o n t he c o mb i n a t i o n o f A X I A L a nd L A T E R A L resolution s o m e c us t o me r s m a y us e t h i s te r m 7/19/2024

28. T y pe s o f R e s o lu t i o n Contrast Resolution – t he a b i l i t y t o r e s o lv e t w o a d j a c e nt o b j e c t s o f s i m i l a r i n te ns i t y / r ef l ec t i v e p r o pe r ti es a s s e p a r a t e o b j e c t s 33 7/19/2024

29. T y pe s o f R e s o luti o n T e m p o r a l R e s o l u t i o n t h e a bi l i t y t o a c c u r a te l y l o c a t e t he p o s i t i o n o f mo v i ng s t r u c t u r e s a t p a r t i c u l a r i ns t a n t s i n t i me a l s o kn o w n a s f r a m e r a t e VERY IMPORTANT IN CARDIOLOGY 34 7/19/2024

30. W h a t d e term i n e s h o w f a r u l t r a s o u nd w a v es c a n t r a v e l ? 35 T he FR E Q U E N CY o f t h e t r a n s d u c e r T he H I G H E R t h e f r e q u en c y , t h e LE S S i t c a n penetrate T he L O W ER t h e f r e q u enc y , t h e D E E P ER i t c a n penetrate Attenuation is directly related to frequency The frequency of a transducer is labeled in Megahertz (MHz) 7/19/2024

31. F r e que n c y v s . R e s o lut i o n 36 T h e f r e q u e n c y a l s o a f f e c t s the Q U A L I T Y o f t h e u l t r a s o u n d i m a g e T h e H I G H ER t he f r eq u e n c y , t he B E T T ER t he resolution T h e L O W ER t h e f r e q u en c y , t he L E SS t h e resolution 7/19/2024

32. F r e que n c y v s . R e s o lut i o n 37 A 1 2 M H z tr a n s d u c e r h a s v e r y g o o d r e s o l u tio n , but c a nn o t p e n e tr a te v e r y d e e p i n to t h e b o d y A 3 M H z tr a n s d u c e r c a n p e ne tr a te d e e p i n to t h e b o d y , b u t t h e r e s o l u t i o n i s n o t a s g o o d a s t h e 1 2 M H z 7/19/2024

33. H o w i s a n i m a g e f o r m e d o n t h e m o n i t o r ? 38 T he a m p l i t u d e o f e a c h r e f l e c t ed w a v e i s r e p r es e n t ed b y a d o t The position of the dot represents the depth from w h i c h t he ec ho i s r e c e i v e d The brightness of the dot represents the strength o f t h e r e t u r n i n g e c ho These dots are combined to form a complete image 7/19/2024

34. P o s i t i o n o f R e f l e c t e d E c h o e s 39 H o w d o e s t he s y s t em k n o w t he d e p t h o f t he reflection? TIMING The system calculates how long it takes for the echo to return t o the tr a n s d u c er T he v el o c i t y i n ti s s u e i s a s s umed co n s t a nt a t 1540m / s ec V e l o c i t y = Di s t a nc e x T i me 2 7/19/2024

35. R e f l e c te d E c ho e s 40 S t r o n g R e f l e c t i o n s = W h i t e d o t s Pericardium, calcified structures,diaphragm W e a k er R ef l ec ti o n s = G r e y d o t s Myocardium, valve tissue, vessel walls,liver N o R e f l e c t i o n s = B l a c k d o t s Intra-cardiac cavities,gall bladder 7/19/2024

36. Transducer The transducer probe generates and receives sound waves using a principle called the  piezoelectric effect. In the probe, there are one or more quartz crystals called  piezoelectric crystals . When an electric current is applied to these crystals, they change shape rapidly. The rapid shape changes or vibrations, of the crystals produce sound waves that travel outward. Conversely, when sound or pressure waves hit the crystals, they emit electrical currents. Therefore, the same crystals can be used to send and receive sound waves.