1. ULTRASOUND SCANNING

2. Introduction to Ultrasound

3. Ultrasound Scanning Physics
Characterized by sound waves of high frequency
Higher than the range of human hearing
Sound waves are measured in Hertz (Hz)
Diagnostic U/S = 1-20 MHz
Sound waves are produced by a transducer

4. Instrumentation - Ultrasound ProbesC

5. Transducers/Probes Sector scanner Linear scanner Curvi-linear scanner
Fan-shaped beam
Small surface required for contact
Cardiac imaging
Linear scanner
Rectanglular beam
Large contact area required
Curvi-linear scanner
Smaller scan head
Wider field of view

6. Indications As a compliment to abdominal radiographs
To determine the origin of an abdominal mass
Spleen, Liver
To facilitate fine needle aspiration/cystocentesis
To evaluate organ parenchyma
To rule in/out intestinal obstruction (foreign body)
***If clinical signs or history indicate abdominal ultrasound, then it should be performed even if radiographs are normal!!!

7. Indications for USG Indications: abdomen, OBG,& Gynec.
Abdomen: Liver- Size, configuration, texture and contour.
To R/o ascites, abscess, cystic disease etc.
Growth – Primary and secondaries.
Jaundice: Viral
Obstructive – Calculi, growth and annular pancreas.

8. Renal US Kidney: size and trauma. Congenital: Agenesis
Calculi (Radiolucent)
Hydronephrosis.
Infections and abscess.
Tumors

9. Pancreas Pancreas: Infections – calcification, duct dilatation
Complications of pancreatitis.
Pseudo cyst and abscess.
Spleen:
Splenomegaly- Fever and abscess.
Portal hypertension
RTA – Splenic injury

10. Abdominal US Abdominal mass, Lymphadenopathy G.I tract: Mass
Obstruction
Volvulus
Worms
Omental secondaries

11. OBG OBG: Missed abortion Ectopic pregnancy 5th week – Gestation sac
6th week - Fetal pole
Cardiac activity
12th week – Head (BPD)
18-20 week- Fetal anomaly scan.
Placenta: Praevia and abruption.
Hydramnios, twins, molar pregnancy.
Position of fetus - Cephalic, breech.
Gestational age: BPD, HC, AC and FL

12. Gynec Gynec: Uterus – Size, congenital anomaly (Bifid, septate etc)
Mass – Fibroids and growth.
Infertility.
Ovaries: Ovulation, mass – cysts and growth.
P.I.D: Free fluid in POD.

13. Why do you need both X-ray and USG?
Examples
Prostatic adenocarcinoma seen on ultrasound
Has it spread to the lumbar vertebrae?
Coughing patient with mitral regurgitation on echocardiogram
Does the patient have pulmonary edema?
Enlarged liver on radiographs
Can get a guided FNA with ultrasound

14. Mirror Image Artifact

15. Comet Tails

16. Artifacts Acoustic shadowing Acoustic enhancement
U/S beam does not pass through an object because of reflection or absorption
Black area beyond the surface of the reflector
Examples: cystic calculi, bones
Acoustic enhancement
Hyperintense (bright) regions below objects of low U/S beam attenuation
AKA Through transmission
Examples: cyst or urinary bladder

17. Acoustic Shadowing

20. Acoustic Enhancement

21. Artifacts Refraction:
Occurs when the sound wave reaches two tissues of differing acoustic impedances
U/S beam reaching the second tissue changes direction
May cause an organ to be improperly displayed

22. Ultrasound-Guided FNA/ Biopsies
Routinely aspirate:
Liver (masses and diffuse disease)
Spleen (nodules and diffuse disease)
Gastrointestinal masses
Enlarged lymph nodes
Enlarged prostate
Pulmonary/ mediastinal masses (usually don’t biopsy due to risk of pneumothorax
Occasionally aspirate:
Kidneys (esp. if enlarged)
Pancreas
Urinary bladder masses
Never aspirate:
Adrenal glands
Gall bladder

23. Ultrasound-Guided FNA/Biopsies
Non-aspiration Technique
22g 1.5in needle
10 cc syringe
Short jabs into organ
Spray onto slide, smear, and check abdomen for hemorrhage

24. DOPPLER

25. Waves from stationary and moving sources

26. Doppler Effect
Shift in perceived frequency when either source or listener are moving relative to one another
Familiar occurrence in audible sounds
Also occurs in medical ultrasound

27. Please note: the ‘squishing’ of the wave-fronts in the middle diagram and the stretching in the lower diagram are exaggerated. Realistically the Doppler shifts are so small in ultrasound you would hardly see any difference in the wave-fronts compared to the unshifted one on top. These are artists’ diagrams.

28. Doppler shift
Doppler shift is the difference between the transmitted and received frequencies.
Transmitted and received frequencies are in the MHz range
Doppler shift frequencies often in audible range

29. Scattering from blood Source of signals for flow imaging:
Red blood cells
Much smaller than l
Rayleigh scatterers
Scattering increases with frequency
Scattering increases with number of targets
Double the number of scatterers, scattered intensity doubles!

30. Cosine Function h
cos q = a/h q a
cos 2o = 0.999 a h a
cos 60o = 0.5 h

31. The frequency of the Doppler shift is proportional to the cosine of the Doppler angle
Angle formed by the ultrasound beam and the direction of flow
Doppler frequency varies with the cosine of the angle.
Cosine = 1 for 0o
Cosine = ½ for 60o
Cosine = 0 for 90o
For angles between 0 and 10o, cosine is close to 1.
The larger the angle (up to 90o), the smaller the cosine

32. Angle Correct Error

33. Range (depth) selection done by a procedure called “gating”
Gating +beam dimensions, define “sample volume”

34. Duplex Mode (Duplex Doppler)
B-mode imaging + Doppler

36. THANK YOU