Aspects of Spectral Doppler imaging
Physics of Medical Ultrasound and Instrumentation
Task 3 Assignment: Requirements
Length: 2000 words
Value: 20%
Topic: Aspects of Spectral Doppler imaging
INTRODUCTION
In addition to these assignment requirements, refer also to the SON4000 Unit Guide located in Moodle for
further information on this assignment.
The purpose of this assignment is to assess your understanding of spectral Doppler imaging. In particular,
two important aspects of it will be considered, namely,
A. The measurement of blood flow velocity and the way in which the blood flow direction is specified
and handled. The definition of the Doppler angle and the reasons for limitations to its range.
B. The concept of aliasing and data sampling issues. The appearance of aliasing and the means by
which it is controlled.
To provide you with as much information as possible about our expectations in the writing of formal
submissions, instructions and guidance are given below about content, structure and layout and
referencing. This will help you in the preparation of your submissions.
In the questions below, an approximate word length is given for guidance only. You will notice that the
suggested word lengths in questions 1, 2 and 3 do not add up to 2000, the nominal word length of this
assignment. This is to allow for some calculations that form part of questions 2 and 3.
CONTENT
1. The Spectral Doppler Display (650 words approximately)
Give an account of the mode of spectral Doppler imaging including:
State the purpose of the spectral Doppler imaging mode.
The overall spectral Doppler display incorporates two main components, a B-mode image and a
Doppler spectrum. Obtain an image of a typical spectral Doppler display including the B-mode image
and the Doppler spectrum (properly citing your source reference) and include it as a figure and then
answer the following questions about it. Number your answers to correspond with the following
question numbers.
1. What is the purpose of the B-mode image?
2. Name the scales on the vertical and horizontal axes of the Doppler spectrum including their units.
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3. Draw and label the scan line on the B-mode image.
4. Label the sample volume on the B-mode image and explain clearly what it is used for and how it
works.
5. Explain the difference between the sample volume as indicated on the B-mode image and the
range gate. Define the range gate in doing so.
6. Label the Doppler angle cursor and explain how it is used.
7. Explain the meaning of the Doppler spectrum and how it is used.
8. Find and include as a separate figure another image showing spectral broadening on the Doppler
spectrum. Explain what spectral broadening is and give two possible causes of spectral broadening.
2. Blood Flow Velocity Measurement (600 words approximately)
Draw a labelled diagram showing the patient’s surface, a linear transducer, a scan line approximately
perpendicular to the patient’s surface and a blood vessel at an angle to the surface consistent with a
Doppler angle of approximately 120 ˚. On this diagram, show the blood flow velocity vector and the
Doppler angle. Give a written definition of the Doppler angle based on this diagram. Is there a blood flow
velocity component towards or away from the transducer? (Only one of these is correct.)
If the sonographer has set the Doppler angle cursor to be accurately in line with the blood vessel, what will
the value of the ‘SV Angle’ on the display be? (It will not be 120˚.)
Calculate the blood flow velocity obtained for this case if the Doppler shift frequency measured by the
system was 1.558 kHz and the transducer frequency was 5 MHz.
Describe some of the vascular blood flow issues that may arise when aligning the Doppler angle cursor on
the monitor with the presumed blood flow direction, for example speed change, eddy flow, velocity profile
etc. Explain how these arise and draw diagrams to support your explanations.
3. Aliasing (600 words approximately)
Explain the Doppler shifts involved (there is more than one), in diagnostic ultrasound, when blood flow is
moving towards the transmitter.
Given a blood flow velocity of 55 cm/s, a Doppler angle of 52˚, and a transducer frequency of 7 MHz,
calculate the Doppler shift frequency that would be found under the given conditions. If the pulse
repetition frequency is 5.9 kHz, state the Nyquist limit frequency. Can spectral Doppler imaging be carried
out without aliasing in the present case? Explain why or why not.
If aliasing did occur, draw a diagram describing its appearance in spectral Doppler imaging.
Give three possible methods for alleviating aliasing artefacts (excluding base-line shifting).
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STRUCTURE AND LAYOUT
General
Assignments are to be written in a professional, formally structured, yet straightforward style. They are
also to be written in such a way as to demonstrate clearly your understanding of the material. As would be
expected when reporting formally to a professional body, a high standard of presentation is required. Do
not use sketches or colloquial language.
Structure
The assignment is to have a title, date, student name and number. It will be divided into standard sections,
with section headings: Introduction, appropriate intermediate sections to break up the subject matter into
logical components, Conclusion and References.
Introduction
The introduction will contain some history and background to the subject matter in question citing several
references from the standard literature and highlighting any difficulties or complications involved.
References should include a number of journal references from the professional literature and perhaps
some text book references. You are not required to go into excessive detail on the contents of such journal
articles, particularly if it is highly technical and mathematical, but you should be able to summarise the key
results and make an informed comment on them in a few sentences.
Tables and Figures
Tables
Data must be included in the form of properly labelled tables each with a suitable caption. Tables are
always numbered and labelled as Table 1, Table 2 etc. For tables, the table number and caption go on top
of the table.
Figures
Images, diagrams, graphs and charts must be included as properly numbered and captioned figures. All
diagrams, plots, graphs, images and so on are labelled and numbered as figures and nothing else. You do
not have Graph 1, Image 2 etc. For figures, the figure number and caption go below the figure. Units must
be included. Full understanding cannot be demonstrated without showing units.
DO NOT use figures taken from the unit Module notes. Search the literature and find your own figures.
Conclusion
Your conclusion should include key numerical results along with a summary of the contents of the report.
Mention any technical difficulties or assumptions involved in the report.
Style
Marks will be lost for incorrect spelling and grammar. Do not use dot points or note form. Use
grammatically correct and complete sentences. You can use properly enumerated complete sentences
occasionally and where appropriate.
Do not use direct quotation. In arts, direct quotation is essential, in science, it is virtually never used.
(Perhaps an insightful statement by Einstein or someone of that calibre might, on rare occasions, justify a
brief direct quotation but not otherwise.)
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Numeracy and quantification
Because this is a physics assignment, you are expected to be numerate. A physicist will not just say “… the
spatial resolution is significantly higher with this method” or even worse, “… the spatial resolution is
unparalleled”!! He would always say, where possible, “… the achievable spatial resolution is xxx mm at yyy
MHz in zzz mode” or similar. You will be expected to quantify your text by quoting typical numerical values
often through this assignment to demonstrate sound knowledge.
REFERENCING
While you may include references to the module notes and text books, this exercise is designed to bring
about wider reading on the topic and to assess your ability to study and assess the existing state of
knowledge in the given field, therefore, your submission must include reference to a minimum of six
journal references, that is, references to the peer reviewed scientific journals.
The following guidelines must be followed. References cited must include no less than six peer reviewed
‘journal’ references, that is, they must be taken from some of the hundreds of professional journals
available using the library databases. Relevant articles may be found by searching databases like Medline,
Inspec and Compendex via the Monash University Library website. Medline has a clinical bias while Inspec
and Compendex have more of an emphasis on physics.
In citing references, websites, such as may be obtained by a Google search for example, are not
considered sound in academic work and are little used in scientific literature because they are not subject
to the stringent peer review process of journal articles. Websites may be written by anybody including
totally unqualified people and may be, and often are, full of errors. If a Google search locates a reference
to a professional journal, the proper journal reference must be given, not the website.
References to the module notes and to listed references, while they can, of course, be used, will be
considered insufficient in themselves because they do not show evidence of wider reading in the scientific
literature, an essential part of this unit. Reading of the scientific literature is also essential if future
developments in the technology are to be followed and understood – one of the purposes of this course.
References to web sites are not entirely prohibited, and may be used very sparingly. This may be
necessary, for example, if referring to unpublished manufacturer’s data. If used, the date on which the site
was accessed must be stated using the correct format.
Be wary of manufacturers’ websites. They contain language such as ‘superlative performance in any clinical
circumstance’, ‘enhanced performance is attained through …’, ‘exceptional imaging performance over a
variety of clinical applications’, state-of-the-art’ and many other phrases such as these. These phrases are
for marketing purposes and are totally meaningless. They do not explain specifically in what respect
performance is enhanced, they provide no quantitative data to back up the statements and they are never
negative. Do not use phrases such as these in your reports.
Correct formats must be used for all referencing down to the last full stop, comma and italicisation. The
formats are described in the library website
http://www.lib.monash.edu.au/tutorials/citing/harvard.html or
http://www.lib.monash.edu.au/tutorials/citing/vancouver.html or
Either the Harvard system (author, date) or the Vancouver system (numeric) must be used. Either is
acceptable. The Harvard system is generally preferable for large documents such as books or theses in
which the reference list may run to twenty pages or more. If the numeric system were used in this case,
the entire reference list would have to be scanned to discover whether a particular reference is present
whereas in the Harvard system, the references are in alphabetical order of first author making it easy to
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search for a required reference. On the other hand, for short documents like research papers, the
Vancouver system, which has the references in numerical order through the document, is very convenient.
Do not rely on ‘EndNote’ to format your reference list. Without setting up the appropriate referencing
style, its reference list formatting will almost certainly be incorrect.
Information for assignment submission online
Please ensure that your assignment is adequately referenced. The following web site will assist you:
http://www.lib.monash.edu.au/tutorials/citing/harvard.html
Ensure that you read widely and ensure that any web sites you use are appropriate.
Instructions:
1. Submit the assignment to Turnitin before submitting to the University for grading. Do not include a
cover sheet, or repeat the assignment questions in your submission to Turnitin, as they will come up
as a match.
2. Record the ‘similarity index’ from the front page of the Turnitin originality report (that shows the level
of matching) at the start of your assignment. Do not submit the originality report.
3. The assignment cannot be submitted to the University for grading if the similarity index is more
than 15% (not including references). Please note; the assessor has access to the full originality
report(s). If the similarity is greater than 15%, then the assignment must be resubmitted to Turnitin
after it has been amended. Note; it takes up to 24 hours for Turnitin to process a submission.
Assignment submission deadlines for grading will not be extended because Turnitin requirements
have not been met.
4. The Faculty expectation is that only one submission to Turnitin should be required at postgraduate
level. If the similarity index is still greater than 15% after two submissions to Turnitin, the student
must contact the assessor for advice and not submit the assignment for grading.
5. Once you have obtained a satisfactory similarity index from Turnitin, submit your assignment to the
proper designated assignment dropbox for grading.
6. There is no need to include a submission cover sheet as the first page of your assignment when you
submit for grading. This has been replaced by students accepting a submission statement as part of
the Moodle submission process.
7. Place your name and student number together with the page number as either the header or footer
on each page.
8. Include a word count.
9. You must retain a copy of all work submitted.
DO NOT EXCEED A FILE SIZE OF 8 Mb. You will need to compress your images into JPEG format or similar.
