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Testing of Doppler Ultrasound Systems
Linköping University, Department of Biomedical Engineering, Physiological Measurements. Linköping University, The Institute of Technology.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Blood and tissue velocities are measured and analyzed in cardiac, vascular, and other applications of diagnostic ultrasound. Errors in system performance might give invalid measurements.

We developed two moving string test targets and a rotating cylinder phantom (Doppler phantoms) to characterize Doppler ultrasound systems. These phantoms were initially used to measure such variables as sample volume dimensions, location of the sample volume, and the performance of the spectral analysis. Later, specific tests were designed and performed to detect errors in signal processing, causing time delays and inaccurate velocity estimation in all Doppler modes.

In cardiac motion pattern even time delays as short as 30 ms may have clinical relevance. These delays can be obtained with echocardiography by using flow and tissue Doppler and M-mode techniques together with external signals (e.g., electrocardiography (ECG) and phonocardiography). If one or more of these signals are asynchronous in relation to the other signals, an incorrect definition of cardiac time intervals may occur. To determine if such time delays in signal processing are a serious problem, we tested four commercial ultrasound systems. We used the Doppler string phantom and the rotating cylinder phantom to obtain test signals. We found time delays of up to 90 ms in one system, whereas delays were mostly short in the other systems. Further, the time delays varied relative to system settings. In two-dimensional (2D) Doppler the delays were closely related to frame rate.

To determine the accuracy in velocity calibration, we tested the same four ultrasound systems using the Doppler phantoms to obtain test signals for flow (PW) and tissue (T-PW) pulse Doppler and for continuous wave (CW) Doppler. The ultrasound systems were tested with settings and transducers commonly used in cardiac applications. In two systems, the observed errors were mostly close to zero, whereas one system systematically overestimated velocity by an average of 4.6%. The detected errors are mostly negliable in clinical practice but might be significant in certain cases and research applications.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2009. , 55 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1284
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-51213ISBN: 978-91-7393-498-5 (print)OAI: oai:DiVA.org:liu-51213DiVA: diva2:274466
Public defence
2009-11-20, Gamla Vårdskolans aula, ingång 21, Centrallasarettet, Västerås, Västerås, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2009-10-29 Created: 2009-10-21 Last updated: 2009-10-29Bibliographically approved
List of papers
1. Evaluating doppler devices using a moving string test target
Open this publication in new window or tab >>Evaluating doppler devices using a moving string test target
1982 (English)In: Journal of Clinical Ultrasound, ISSN 0091-2751, E-ISSN 1097-0096, Vol. 10, no 1, 25-30 p.Article in journal (Refereed) Published
Abstract [en]

Two moving string test targets have been developed and used to characterize ultrasound Doppler instrumentation. The characteristics investigated were sample volume size and location. The tests were performed on a combined echo/Doppler instrument and on an annular array system. The procedures can be carried out routinely in the clinical laboratory to ensure that the instrument is working properly or as an aid for correct interpretation of acquired data.

Place, publisher, year, edition, pages
Wiley InterScience, 1982
Keyword
Quality assurance, Doppler, string target, Ultrasound test phantom, Pulsed Doppler, Duplex ultrasound
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-51090 (URN)10.1002/jcu.1870100106 (DOI)
Available from: 2009-10-16 Created: 2009-10-16 Last updated: 2017-12-12Bibliographically approved
2. Time delays in ultrasound systems can result in fallacious measurements.
Open this publication in new window or tab >>Time delays in ultrasound systems can result in fallacious measurements.
Show others...
2002 (English)In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 28, 259-263 p.Article in journal (Refereed) Published
Abstract [en]

Even short time delays (less than 30 ms) in cardiac motion pattern may have clinical relevance. These delays can be measured with echocardiography, using techniques such as flow and tissue Doppler and M-mode together with external signals (e.g., ECG and phonocardiography). If one or more of these signals are delayed in relation to the other signals (asynchronous), an incorrect definition of cardiac time intervals can occur, the consequence of which is invalid measurement. To determine if this time delay in signal processing is a problem, we tested three common ultrasound (US) systems using the ECG as the reference signal. We used a digital ECG simulator and a Doppler string phantom to obtain test signals for flow and tissue pulsed Doppler, M-mode, phonocardiography, auxiliary and ECG signals. We found long time delays of up to 90 ms in one system, whereas delays were mostly short in the two other systems. The time delays varied relative to system settings. Consequently, to avoid these errors, precise knowledge of the characteristics of the system being used is essential.

Federation for Ultrasound in Medicine & Biology.

Keyword
Ultrasound system, Doppler, Time delay, Doppler phantom, Echocardiography
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26694 (URN)11283 (Local ID)11283 (Archive number)11283 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13Bibliographically approved
3. Accuracy of spectral Doppler flow and tissue velocity measurements in ultrasound systems
Open this publication in new window or tab >>Accuracy of spectral Doppler flow and tissue velocity measurements in ultrasound systems
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2004 (English)In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 30, no 1, 127-132 p.Article in journal (Refereed) Published
Abstract [en]

Blood and tissue velocity are measured and analysed in cardiac, vascular and other applications of diagnostic ultrasound (US). An error in system calibration is a potential risk for misinterpretation of the measurements. To determine the accuracy in velocity calibration, we tested three common commercial US systems using a Doppler string phantom. We tested pulsed and continuous-wave Doppler modes for velocities relevant to both cardiac blood flow and tissue-velocity estimation. The US systems were tested with settings and transducers commonly used in cardiac applications. One system consistently overestimated velocity by about 5%, whereas the other two systems were quite accurate in velocity estimation. These findings emphasize the importance of continuous quality control of US equipment.

Keyword
Ultrasound system, Doppler, Velocity, Accuracy, Doppler phantom, Calibration, Echocardiography
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-22168 (URN)10.1016/j.ultrasmedbio.2003.08.020 (DOI)1295 (Local ID)1295 (Archive number)1295 (OAI)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13Bibliographically approved
4. A Rotating Cylinder Phantom for Flow and Tissue Color Doppler Testing
Open this publication in new window or tab >>A Rotating Cylinder Phantom for Flow and Tissue Color Doppler Testing
2009 (English)In: Ultrasound in Medicine and Biology, ISSN 0301-5629, E-ISSN 1879-291X, Vol. 35, no 11, 1892-1898 p.Article in journal (Refereed) Published
Abstract [en]

Ultrasound Doppler using two-dimensional (2D) techniques is commonly used to study blood flow and myocardial tissue motion. This use includes measurement of velocity and time intervals, often in relation to the electrocardiogram (ECG) signal. 2D Doppler is frequently considered a real-time technique but in reality the acquisition time can be as long as 200 ms per image. We have developed a test-phantom using a rotating cylinder to simulate blood flow and tissue motion in a whole sector or space angle to evaluate velocity and timing characteristics.The phantom can produce constant velocities for velocity testing, as well as accelerating movement for testing the timing characteristics of ultrasound systems. Our investigation shows that the cylinder phantom is especially suitable for timing measurements in 2D Doppler imaging and that time delays between the Dopplersignals and the ECG signal exist in the tested ultrasound system.

Place, publisher, year, edition, pages
Elsevier, 2009
Keyword
Doppler phantom, Time delay, Color Doppler, Tissue Doppler, Echocardiography
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-51372 (URN)10.1016/j.ultrasmedbio.2009.06.1095 (DOI)000278012000013 ()
Available from: 2009-10-29 Created: 2009-10-29 Last updated: 2017-12-12Bibliographically approved

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