1. Pegasus Lectures, Inc. Volume II Companion Presentation Frank Miele Pegasus Lectures, Inc. Ultrasound Physics & Instrumentation 4 th Edition

2. Pegasus Lectures, Inc. This presentation is the sole property of Pegasus Lectures, Inc. No part of this presentation may be copied or used for any purpose other than as part of the partnership program as described in the license agreement. Materials within this presentation may not be used in any part or form outside of the partnership program. Failure to follow the license agreement is a violation of Federal Copyright Law. All Copyright Laws Apply. License Agreement

3. Pegasus Lectures, Inc. Volume II Outline  Chapter 7: Doppler  Chapter 8: Artifacts  Chapter 9: Bioeffects  Chapter 10: Contrast and Harmonics  Chapter 11: Quality Assurance  Level 2  Chapter 12: Fluid Dynamics  Chapter 13: Hemodynamics

4. Pegasus Lectures, Inc. Equipment Testing Many devices have been created to test system performance. System tests are desired to make certain that there has been no degradation in system performance over time.  The most likely part of the system to break or “degrade” is the transducer  Getting repeatable test results takes careful preparation and great system knowledge  Doppler performance testing presents many exceptionally difficult challenges.  The best way to guard against system degradation is to be vigilant and have regular system maintenance

5. Pegasus Lectures, Inc. Doppler Testing Doppler testing presents extraordinary challenges since mimicking the properties of blood in a consistent fashion is extremely difficult. As a result, many different types of Doppler phantoms have been created. The most notable are:  Flow phantoms  String phantoms  Vibrating Plate (sensitivity) phantoms

6. Pegasus Lectures, Inc. Doppler Flow Phantoms (General Design) A Doppler flow phantom is very complex and in it simplest form consists of:  an imaging face  a medium  a flow conduit  a pump  a blood mimicking fluid  reservoir Pump and Fluid Reservoir Fluid Conduit Imaging Face Fig. 1: (Pg 697)

7. Pegasus Lectures, Inc. This flow phantom can be used for:  Directional Discrimination  Flow velocity  Sensitivity (varying depth)  Maximum penetration  Location of flow Fig. 2: (Pg 698) Doppler Flow Phantoms (Discrimination Device)

8. Pegasus Lectures, Inc. This device is used to produce the fluid flow and can be used in conjunction with flow phantoms such as the discrimination device shown in the previous slide. Fig. 3: (Pg 699) Flow Phantom (Controller)

9. Pegasus Lectures, Inc. Fig. 4: (Pg 699) Blood Mimicking Fluid The greatest difficulty with Doppler flow phantoms is producing a fluid with stable reflective properties over long periods of time. Some companies have recognized this problem and now sell blood mimicking fluids. Fig. 5: (Pg 700)

10. Pegasus Lectures, Inc. This flow phantom produces a known volumetric flow with laminar flow profiles in the center stream of the flow conduit. A second Doppler sensitivity phantom can be included within the box. The sensitivity phantom has a diving vessel with a variable speed constant velocity flow. Fig. 7: (Pg 701) Flow Phantom (Calibrated Flow Volume)

11. Pegasus Lectures, Inc. Fig. 9: (Pg 703) String Phantoms A string phantom uses controlled movement of a string via a motor to create reproducible velocities.

12. Pegasus Lectures, Inc. Fig. 10: (Pg 704) String Phantoms Notice in the upper left hand corner the velocity profile created by the moving string. This type of phantom was designed to test:  peak velocity accuracy  gate depth accuracy  spectral broadening

13. Pegasus Lectures, Inc. Fig. 13: (Pg 706) Vibrating Plate Doppler Phantom Creates a Doppler signal by phase modulation of the ultrasound beam through very small vibrations of a target plate.

14. Pegasus Lectures, Inc. Imaging Testing Many phantoms have been created to test various aspects of 2-D and now 3-D imaging characteristics and the various types of resolution. Some of the aspects that can be tested with the various phantoms include:  Detail resolution (lateral, axial, and elevation)  Sensitivity  Contrast resolution  The dead zone (area close to the transducer dominated by reverberation)  Dimensional measurement accuracy (depth, diameter, area, volume, etc.)

15. Pegasus Lectures, Inc. Detail Resolution Testing By placing the transducer on a different “face” different aspects of detail resolution can be tested. Face A Face B  From Face “A”, Lateral resolution would be tested.  From Face “B”, Axial Resolution would be tested. Fig. 15: (Pg 708)

16. Pegasus Lectures, Inc. Multi-purpose Tissue/Cyst Phantom The multi-purpose tissue cyst phantom can be used to test many different aspects of the ultrasound system including:  Dead Zone  Detail resolution (lateral and axial)  Depth accuracy  Measurement accuracy  Contrast resolution  Penetration

17. Pegasus Lectures, Inc. Multi-purpose Tissue/Cyst Phantom

18. Pegasus Lectures, Inc. AIUM 100 mm Test Object This phantom can be used for testing detail resolution, depth accuracy, the dead zone, and penetration.  Dead Zone  Detail resolution (lateral and axial)  Depth accuracy  Measurement accuracy This test object can be purchased in different configurations for more accurate measurements.  Can purchase with or without fluid to present a velocity similar to soft tissue  Can purchase with a built in thermometer for accurate propagation velocity calculations

19. Pegasus Lectures, Inc. Tissue Equivalent Phantom With tissue mimicking material the phantom can also be used for penetration tests, since the tissue mimicking material has attenuation properties similar to tissue. Scan of Tissue Phantom

20. Pegasus Lectures, Inc. Scans of a Cyst Phantom High frequency scans of a cyst phantom Depth = 4 cmDepth = 6 cm

21. Pegasus Lectures, Inc. Focal Zone Banding This image was created by “splicing” eight different acoustic lines together per display line. Notice the “brighter” region and horizontal “lines” across the image where the foci are placed. These striations are caused by the “seams” between each of the lines which have been pasted together.

22. Pegasus Lectures, Inc. Fig. 16: (Pg 709) ATS Multipurpose Phantom This phantom can be used for:  Dead zone (ring down)  Vertical measurement accuracy  Horizontal measurement accuracy  Sensitivity/Penetration  Focal Zone  Axial and Lateral Resolution  Image uniformity  Gray scale & displayed dynamic range

23. Pegasus Lectures, Inc. Fig. 17: (Pg 709) Curved Linear Image of the ATS Multipurpose Phantom

24. Pegasus Lectures, Inc. Fig. 18: (Pg 710) CIRS Model 040 Phantom This phantom can be used for:  Image uniformity  Axial and Lateral resolution  Depth calibration  Dead zone (ring down)  Registration within two different backgrounds of 0.5 and 0.7 dB/cm/MHz

25. Pegasus Lectures, Inc. Fig. 19a: (Pg 711) Fig. 19b: (Pg 711) Images of the CIRS Phantom Image of a cystic structure and a mass in the CIRS Model 040 Phantom Image of various pin groups in the CIRS Model 040 Phantom

26. Pegasus Lectures, Inc. Fig. 20: (Pg 711) ATS Model 538 Beam Profile and Slice Thickness (elevation) Phantom Fig. 21: (Pg 712)

27. Pegasus Lectures, Inc. Fig. 23a: (Pg 713) (CIRS Model 047) Gray Scale Phantom This aspect of the phantom can be used for testing depth accuracy as seen in this longitudinal view.

28. Pegasus Lectures, Inc. Fig. 23b: (Pg 713) (CIRS Model 047) Gray Scale Phantom Contrast Resolution Notice that the cysts and mass with the greatest contrast (anechoic, -9 dB, and +9 dB) are the most readily visible and that the cyst and mass with the least contrast (-3 dB and +3 dB) are virtually imperceptible.

29. Pegasus Lectures, Inc. Fig. 25: (Pg 715) CIRS Ultrasound Calibration Phantom The large and small eggs are used for volume measurements and contrast. The wire targets are used to measure linear and curved dimensions. The wires can also be used to determine image uniformity and depth of penetration.

30. Pegasus Lectures, Inc. Fig. 26: (Pg 716) Needle Biopsy (Breast) Phantom The breast phantom can be used to practice aspirating and biopsying. The cysts can be aspirated once, and each solid mass can be biopsied multiple times.

31. Pegasus Lectures, Inc. Fig. 27: (Pg 716) Image of the Breast Phantom MassCystic Structure

32. Pegasus Lectures, Inc. Fig. 29: (Pg 717) CIRS Fetal Phantom The anatomy is based on published biometric data at normal fetal growth rates of gestational age 21 weeks. This enables assessment of composite measurement techniques and biometric analysis programs. The phantom can also be used for 3D reconstructions and surface renderings.

33. Pegasus Lectures, Inc. Fig. 30 & 31: (Pg 718) Interventional Arterial Phantoms The ultrasound catheter is placed in the center hole so as to image the surrounding cavities or rods of varying acoustic contrast.

34. Pegasus Lectures, Inc. Fig. 32: (Pg 719) ONDA HIFU Phantom (Clear Phantom Gels) HIFU (High Intensity Focused Ultrasound) imaging intentionally produces high intensities so as to cause bioeffect lesions. These clear gel phantoms produce lesions of the same position, size, and shape as those produced in real tissue.

35. Pegasus Lectures, Inc. Q & A Statistics There are a series of statistical measures used to determine the “quality” of a test. To validate a test, the test is compared against another test referred to as the “Gold Standard”. To make sense, the statistical measures must start with an assumption about the gold standard: The Golden Rule: For the purposes of the statistical indices, the assumption is that the gold standard is perfect.

36. Pegasus Lectures, Inc. The plus sign next to the Comparison Test implies that the test was positive for disease. When the Test is Positive for Disease Fig. 33: (Pg 724)

37. Pegasus Lectures, Inc. Fig. 34: (Pg 724) When the Test is Negative for Disease The minus sign next to the Comparison Test implies that the test was negative for disease.

38. Pegasus Lectures, Inc. Fig. 35: (Pg 724) When the Gold Standard is Positive for Disease The plus sign below the gold standard implies that the gold standard was positive for disease. Since the gold standard is assumed to be perfect, everyone below the plus sign of the gold standard is assumed to truly have disease.

39. Pegasus Lectures, Inc. Fig. 36: (Pg 721) When the Gold Standard is Negative for Disease The minus sign below the gold standard implies that the gold standard was negative for disease. Since the gold standard is assumed to be perfect, everyone below the minus sign of the gold standard is assumed to truly not have disease.

40. Pegasus Lectures, Inc. Putting the Pieces Together According to the Golden Rule Remember that the gold standard is presumed to be perfect, and hence the definition of truth. When the comparison test matches the gold standard, it is considered to be “TRUE”. When the comparison test does not match the gold standard, the test is considered to be “FALSE”. True Positive (TP): implies that the test correctly predicts that there is disease (the test predicts disease when the gold standard predicts disease). True Negative (TN): implies that the test correctly predicts that there is no disease (the test predicts no disease when the gold standard predicts no disease). False Positive (FP): implies that the test incorrectly predicts there is disease (the test predicts disease when the gold standard does not). False Negative (FN): implies that the test incorrectly predicts that there is no disease (the test predicts no disease when the gold standard predicts disease).

41. Pegasus Lectures, Inc. Interpreting the Comparison Table When the comparison test matches the gold standard, the result is considered true, if it does not match it is considered false. Comparison Test correctly predicted disease (FN)(TN) + _ + _ Gold Standard (TP)(FP) incorrectly predicted disease correctly predicted no disease incorrectly predicted no disease

42. Pegasus Lectures, Inc. Since under the “Gold Standard,” the plus sign indicates that the gold standard was positive for disease, the number of tested patients in the population that truly have disease equals: Patients with Disease Comparison Test correctly predicted disease (FN)(TN) + _ + _ Gold Standard (TP)(FP) incorrectly predicted disease correctly predicted no disease incorrectly predicted no disease

43. Pegasus Lectures, Inc. Patients without Disease Since under the “Gold Standard,” the minus sign indicates that the gold standard was negative for disease, the number of tested patients in the population that truly do not have disease equals: Comparison Test correctly predicted disease (FN)(TN) + _ + _ Gold Standard (TP)(FP) incorrectly predicted disease correctly predicted no disease incorrectly predicted no disease

44. Pegasus Lectures, Inc. When the Test is Positive Since next to the “Comparison Test,” the plus sign indicates that the test was positive for disease, the number of tested patients in the population that the test predicts to have disease equals: Comparison Test correctly predicted disease (FN)(TN) + _ + _ Gold Standard (TP)(FP) incorrectly predicted disease correctly predicted no disease incorrectly predicted no disease

45. Pegasus Lectures, Inc. When the Test is Negative Since next to the “Comparison Test,” the negative sign indicates that the test was negative for disease, the number of tested patients in the population that the test predicts do not have disease equals: Comparison Test correctly predicted disease (FN)(TN) + _ + _ Gold Standard (TP)(FP) incorrectly predicted disease correctly predicted no disease incorrectly predicted no disease

46. Pegasus Lectures, Inc. Sensitivity The ability of a test to detect disease. (How many times the test correctly said there was disease divided by the total number of times there was disease.) Comparison Test correctly predicted disease (FN)(TN) + _ + _ Gold Standard (TP) (FP) incorrectly predicted disease correctly predicted no disease incorrectly predicted no disease

47. Pegasus Lectures, Inc. Specificity The ability of a test to detect the absence of disease. (How many times the test correctly said there was no disease divided by the total number of times there was no disease.) Comparison Test correctly predicted disease (FN)(TN) + _ + _ Gold Standard (TP)(FP) incorrectly predicted disease correctly predicted no disease incorrectly predicted no disease

48. Pegasus Lectures, Inc. Accuracy The percentage of times the test is correct. (The number of times the test was correct divided by the total number of tests.) Comparison Test correctly predicted disease (FN)(TN) + _ + _ Gold Standard (TP)(FP) incorrectly predicted disease correctly predicted no disease incorrectly predicted no disease

49. Pegasus Lectures, Inc. Positive Predictive Value The percentage of times the test was correct when it predicted the presence of disease. (How many times the test correctly predicted the presence of disease divided by the total number of times the test predicted that there was disease.) Comparison Test correctly predicted disease (FN)(TN) + _ + _ Gold Standard (TP)(FP) incorrectly predicted disease correctly predicted no disease incorrectly predicted no disease

50. Pegasus Lectures, Inc. Negative Predictive Value The percentage of times the test was correct when it predicted the absence of disease. (How many times the test correctly predicted the absence of disease divided by the total number of times the test predicted that there was no disease.) Comparison Test correctly predicted disease (FN)(TN) + _ + _ Gold Standard (TP)(FP) incorrectly predicted disease correctly predicted no disease incorrectly predicted no disease

51. Pegasus Lectures, Inc. The “Perfect” Test Referenced to the gold standard, a perfect test would be: The sensitivity, specificity, accuracy, positive predictive value, and the negative predictive value would all be 100%. Comparison Test (FN)(TN) + _ + _ Gold Standard (TP)(FP) 0 0 X Y

52. Pegasus Lectures, Inc. Real World Understanding In reality, the statistical measures are only as meaningful as the gold standard is accurate. In essence:  There is no guarantee that the gold standard is always correct  A “good” match to a good standard means a good test  A “good” match to a bad standard means a bad test  A “bad” match to a good standard means a bad test  A “bad” match to a bad standard doesn’t tell you much In other words: If the gold standard is “no good”, the statistical measures will not necessarily mean much.

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