The MANCHESTER handbook of ppt

The
MANCHESTER
handbook of
ULTRASOUND TECHNIQUES
THE MANCHESTER HANDBOOK OF ULTRASOUND
TECHNIQUES
‘The most important part of a stethoscope is the bit between the ear-pieces.’
- Samuel Oram, consultant cardiologist and describer of Holt-Oram syndrome
A beginner’s guide and vade-mecum for first and second year specialist registrars in diagnostic
radiology.
Written and edited by:
Brennan Wilson, Consultant Paediatric Radiologist, Manchester Children’s Hospitals
Hari Mamtora, Consultant Radiologist, Hope Hospital, Salford
Jane Hawnaur, Senior Lecturer and Consultant Radiologist, Manchester Royal Infirmary
Note to readers, wherever you are:
This booklet is a joint effort. We want it to be as good as possible. We expect to have to make several
revisions of the book, and all constructive comments, drawing our attention to inaccuracies and
omissions etc., will be gratefully received.
Brennan Wilson
Department of Radiology
Royal Manchester Children’s Hospital
Pendlebury
Manchester M27 4HA
Tel: (0161) 794 4696 (switch)
(0161) 727 2204 (direct)
(0161) 727 2460 (fax)
email:
Introduction
This handbook is designed for
first and second year specialist registrars in radiology
. It assumes a

basic understanding of ultrasound physics and technology, and the rudiments of cross-sectional
anatomy, and is designed to help you from that background towards the practical business of working
an ultrasound machine. You will find a summary of the main controls of an ultrasound machine, and
points of anatomy where these are directly relevant to orientating yourself within a given image.
Pathology is mentioned where it is relevant to how an image is taken. However, this is not meant to
replace a textbook of any of these subjects.
So far, the booklet reflects the collected experience of the three editors with valued comments from
some colleagues and current SpRs (notably Ralph Jackson). However, it is admittedly still experimental
and would obviously benefit from as many constructive comments as possible. We do not know of
another such handbook being available, and we realise that we may have committed omissions and
errors of fact, and we have also almost certainly failed to realise some of the things that SpRs find
difficult to grasp at first. With that in mind:
• It is printed on one side of the paper only, in order to encourage you to add your own notes. We
would very much like to collect as many of the booklets as possible at the end of the year, in order
to be able to use these comments to re-edit the book. We will be glad to make arrangements to give
the originals back to you if you like.
• Please feel free to send any comments you have to me - anonymously if you like - or to the
electronic comment board for the registrars at www.smuht.man.ac.uk/radio.
We honestly want to use the readers of this book as a resource for improving it year by year.
Remember, the success of the teaching for the junior SpRs depends on you yourselves!
BW
Contents
1 Principles of ultrasound scanning
2 Gynaecology and obstetrics
3 Hepatobiliary imaging
4 Renal tract
5 Lower limb venous duplex imaging and colour Doppler of the neck
6 Small parts
Chapter 1: Principles of ultrasound scanning
Approach to the patient

The same professional courtesy is expected in the ultrasound examination room as anywhere else in
medicine.
• Greet your patient by name, introduce yourself, shake hands, smile, and make eye contact.
• Most patients will understand what ultrasound is but you should be ready to explain it to patients
with poor understanding (e.g. children) or if you are going to perform a more complicated
procedure, e.g. an ultrasound-guided interventional procedure.
• Protect the patient’s clothing with paper and warn them about the cold US gel. Respect the patient’s
modesty and be alert to any signs of tenderness as you apply the transducer.
• Avoid discussing one patient in front of another.
• You may make a serious diagnosis in the patient’s presence in the ultrasound room. Ensure that you
understand local and national guidelines on communicating bad news to patients, and be honest,
courteous and sympathetic.
Approach to the ultrasound machine
• Stand or sit comfortably in front of the machine so that you can reach the patient without bending
sideways unnecessarily.
• Check that the appropriate transducer is connected and that the system is set up for the type of
examination you wish to perform, e.g. 3.5 MHz sector probe and abdominal protocol.
• Use sufficient acoustic coupling gel, especially in hairy patients.
• Hold the transducer with the tips of your right thumb and fingers. This is important as it allows you
to roll the probe around its long axis.
• Arrange the transducer wire so that its weight does not drag on the hand holding the probe. You may
want to untangle it or loop it around the back of your neck.
• If necessary, rest your right forearm or elbow on the patient’s couch or a convenient part of his
body. Ask his permission first.
General principles of ultrasound imaging
• Make sure you are familiar with the machine before you start.
• Unlike the situation with plain radiography, in ultrasound there is no-one else to adjust the settings
of the machine to produce an excellent image. The machine settings should be adjusted to suit
you
.

• Each ultrasound image should be optimised to illustrate a particular clinical sign. Don’t try to show
too much on a single image - take two if each will show one particular finding more clearly.
• Remember that what you see is a tomogram. If you are examining any organ with a definite volume,
you need to sweep across the plane of the scan all the way from one side of the organ to the other to
make sure you have missed nothing. Then you need to repeat the sweep in at least one other plane.
You find the other planes by rotating the probe or approaching the organ from another angle.
• Get into the habit of sweeping smoothly through an organ at a steady rate. Then tubular structures
within the organ such as blood vessels will appear to move steadily along their courses, whereas
rounded structures such as masses will be easy to notice as they flash into view and out again.
• Label and hard-copy standard views of normal organs examined. Obtain views in several planes,
labelled and annotated with measurements if appropriate. Take extra views to show any abnormal
findings. Your colleagues may have to use these images for future comparisons, so try to include as
much visual information as you can on the hard copy record of your examination.
• Many abdominal organs may be obscured by bowel gas. One way round this problem is to press
firmly against the bowel for a few minutes, and literally squeeze the bowel out of the way (the
graded compression technique
). Ask your patient’s permission before you do it, and desist if you
are requested.
Ultrasound machine settings and their meanings
The parameters preset on the machine will enable you to start scanning but use the following
information to help you understand the controls and modify settings to obtain the best diagnostic image
in individual patients. Images are viewed from the patient’s right for longitudinal scans, and from the
patient’s feet for transaxial scans.
•
Transducer frequency
is the frequency of the signal emitted. On some modern machines this can
be selected electronically from a range within the same transducer: however, nowadays most
transducers are still single-frequency only and you will have to toggle between transducers or plug a
new one in to the socket on the front or side of the machine.
High frequency probes

have a better
longitudinal resolution but less penetrating power through tissues, and are typically used for
children and small organs or ones close to the transducer face.
Low frequency probes
can be used
to penetrate deep into large areas such as adult abdomens but at the cost of a somewhat lower
resolution.
•
Transmit power
is the level of power delivered into the body, given on a logarithmic scale. Use the
lowest transmit power necessary for diagnosis. If you need to increase the transmit power to see far
into the image, consider choosing a transducer at a lower frequency instead.
•
Gain
is the amplification applied to the returning signal. It needs to be set so that the signals in the
area of interest are all contained within the grey scale on the screen. Common mistakes here are to
allow the back of the image to become too dark, e.g. when examining the back of a large liver, or to
allow structures seen behind a fluid cavity (for example, the adnexae behind the urinary bladder) to
become too bright in the acoustic enhancement.
•
Receive gain
is the overall amplification applied, and has the effect of changing the brightness of
the whole image.
•
Time gain compensation (gain curve, swept gain)
: This compensates for acoustic loss in the
deeper tissues from absorption, scatter and reflection of the US beam. The aim is to show structures
of the same acoustic strength as echoes of equal amplitude, whatever their depth. On most modern
machines, the control is presented as a column of slides, each of which governs the amplification
(gain) at a specific depth within the image, starting from the transducer face at the top. A good deal

of swept gain compensation is built into the machine so it is often convenient to start with the slides
in a vertical stack, but be ready to adjust them as necessary.
•
Transmit zone (focal depth)
: This is the depth at which the ultrasound beam is at its narrowest
after passing through the
near zone
and before fanning out into the
far zone
. Thus, the lateral
resolution of the image is greatest here. Position it at or just behind the area of interest. Multiple
focal zones are applicable to large static structures, but may cause a drop in frame rate, which can
make any movement while scanning appear intrusive.
•
RES (regional expansion selection)
: This facility is available on Acuson machines and produces a
magnified image in a selected area of interest with increased frame rate and spatial resolution. Keep
the RES box in proportion to the sector: e.g., a long and narrow box gives a larger expanded image.
You can alter the transmit zone on the expanded image, but not the depth.
•
Log compression ( dynamic range)
: This is the range in acoustic power (in decibels) between the
faintest and the strongest signals that can be displayed on the screen. Many machines have a default
setting of 48-55 dB. Increasing the dynamic range produces a greyer, flatter image. Decreasing it
increases the apparent ‘contrast’ in the image and emphasises small changes in signal strength - this
can be helpful where abnormalities are very close to the same shade of grey as the surrounding
tissue, for example metastases in the liver or masses in the testis. However, it also increases the
visual ‘noise’ on the image.
Controls best left alone to start with
•

Preprocessing
is the computer enhancement applied to the returning raw data before it is
reformatted into an image.
•
Persistence (frame averaging)
: The number of frames which are mathematically added to produce
each image. Higher persistence tends to suppress noise but can cause motion artefacts.
•
Postprocessing
is computer enhancement applied to the reformatted image, for example by
compressing some parts of the grey-scale selectively. Unlike the gain and dynamic range controls, it
does not affect the overall quantity of information on the image.
Common artefacts
•
Reverberation
. Echoes are transmitted to and fro between the transducer and an interface in the
patient, e.g. in the fat of the anterior abdominal wall, or gas filled bowel. This produces a ‘ghost’ of
the interface responsible at twice the depth, and may be mistaken for pathology. Try looking from a
different angle to see what happens to the suspicious echo.
•
Acoustic shadowing
. A user-friendly artefact which allows identification of calculi as strongly
reflective structures which do not allow passage of ultrasound energy beyond them. A dark shadow
is seen behind a strong echo. Gas in bowel or lung generally produces a less intense acoustic
shadowing, or bright ‘comet-tail’ artefacts.
•
Acoustic enhancement
. Passage of ultrasound through a tissue which is less attenuating than usual
produces a relative increase in echo amplitude distal to the area, a so called ‘bright-up’. This can
help to differentiate fluid-containing cysts from other hyporeflective but solid masses. Remember to

adjust the gain if you are looking at structures behind a fluid collection, e.g. behind the bladder.
Troubleshooting
If your image is poor, a list of possible causes to check through might include:
• Machine-related causes: poorly adjusted settings of the depth or overall gain, focusing, transducer
transmission frequency, etc.
• Technique-related causes: poor contact against the skin, inappropriate acoustic window chosen, etc.
• Patient-related causes: image degradation by interposition of obesity, bowel gas, bone, ectopic
calcification etc. Try reducing the frequency of the transducer, perhaps as far as 2.5 MHz, to
penetrate obesity; reduce the dynamic range, increase persistence to reduce the noise. Some very
modern machines offer
harmonic imaging
which may help to overcome poor signal quality.
• Do the best you can, but recommend alternative imaging, e.g. CT, if appropriate.
Chapter 2: Transabdominal pelvic ultrasound for
gynaecology and obstetrics
GYNAECOLOGICAL APPLICATIONS
Indications
• Pelvic pain or swelling
• disturbance of the bladder or bowel function
• Change in menstrual pattern (dysmenorrhoea, menorrhagia, abnormal bleeding)
• Amenorrhoea or infertility
Preparation
• Ask the patient to drink two pints (one litre) of fluid one hour before her appointment, to fill her
bladder.
• Ask about relevant symptoms, the patient’s menstrual cycle, date of her last period, prior
pregnancies, contraceptive use, and use of hormone replacement therapy, as appropriate.
• With the patient supine, expose the entire abdomen from the xiphisternum to the symphysis pubis.
Protect the patient’s clothing with paper.
• For a patient of average build, a 3.5-4 MHz phased array transducer is appropriate. Other patients
may require a lower frequency, e.g. 2.5 MHz.

• Check the adequacy of bladder filling - the bladder fundus should extend to the fundus of the uterus.
An overdistended bladder is unpleasant for the patient and displaces structures away from the US
probe. Ask the patient to void a little to reduce overdistension.
ROUTINE EXAMINATION:
Sagittal and parasagittal views of uterus, cervix and vagina.
• Sweep through the full length of the uterine body, cervix and vagina from side to side. The normal
uterus has a fairly homogeneous medium reflectivity, with brighter echoes from the
endometrium
and endometrial cavity.
• Image a midline sagittal view of the uterus and measure length from fundus to external os.
• Approximate
uterine lengths
are:
• Premenarchal girls vary with age, usually less than 2.5 cm, with the cervix the widest part.
• Women of reproductive age 6-8 cm with corpus length twice that of the cervix. Uterine
size is 1-2cm larger in multiparous compared with nulliparous women and 1-2cm smaller
in post-menopausal women.
• The uterus can be
tilted
in any direction so angle the probe if the uterus lies oblique to the midline
of the patient. A uterus may be
anteflexed
(anteverted) (fundus pointing towards anterior abdominal
wall)or
retroflexed
retroverted (pointing towards sacrum). It may have to be measured in two
portions.
• Image a
zoomed sagittal view of the uterus
showing the bright central echoes representing the

endometrium plus any tissue in the endometrial cavity. The double layer thickness of bright echoes
in the AP direction may measure up to 15 mm during the menstrual cycle, but should not exceed
5mm after the menopause.
•
Intrauterine contraceptive devices
produce strong acoustic reflections and acoustic shadowing
from within the uterine cavity.
Transverse views of uterus, cervix, parametrium and vaginal vault
• Sweep through the
uterine body, cervix and upper vagina
from top to bottom. Image a cross-
section of the uterine fundus. Note the orientation of the fundus on the sagittal view and angle your
transducer accordingly to obtain a section at right angles to the long axis, anteverted or retroverted.
• Measure AP and transverse diameters (approximately 4 cm AP x 5 cm transverse in reproductive
years).
Transverse and longitudinal views of adnexae
• Scan right and left adnexae carefully from the uterus out to the pelvic walls.
• Assess the size, shape and position of the
ovaries
. These usually lie on the pelvic wall, at or above
the level of the uterine fundus, on the back of the broad ligament. They are normally ovoid in shape,
with mid-level reflectivity and small cystic areas representing developing follicles (in the
reproductive age group). If you have difficulty finding the ovaries, use the internal iliac vessels as a
guide, the ovaries usually lying medial to the vein. Other favourite hiding places are the pouch of
Douglas, behind or above the uterine fundus or adjacent to the cervix. You may need to angle
obliquely through the bladder from the far side to obtain clear views of the ovaries.
• The dominant (ovum-producing)
follicle
may measure up to 25mm in diameter, but should regress
in the luteal phase of the menstrual cycle.

•
Ovarian volumes
: Volume is estimated by multiplying the anteroposterior, transverse and
longitudinal diameters and dividing by 2.
• In
childhood
, size varies with age. Follicles may be seen up to age four from maternal
transplacental ovarian stimulation; premenarchal follicles may start to appear from age 8.
• In the
reproductive years
, volumes vary from 6-14 cm
3
.
• In
post-menopausal
women, volumes vary from 1-4 cm
3
. They have no obvious follicles
and may be more difficult to see. They should not exceed about 8 cm
3
in volume and
obvious asymmetry in size should be considered abnormal.
• The broad ligament also contains the
fallopian tubes
(normally invisible)
, uterine
and
ovarian
vessels
and

supporting ligaments
.
• The important objective in this circumstance is to
exclude ovarian enlargement
or an
adnexal
mass
, e.g. hydrosalpinx, cysts, free fluid, remembering to check for masses displaced up out of the
pelvis.
• Image longitudinal views of the right and left
kidneys
(q.v.) to exclude renal tract abnormality, such
as hydronephrosis or congenital anomaly. Review the retroperitoneum, liver, and peritoneal spaces
if appropriate.
ENDOVAGINAL ULTRASOUND
In endovaginal US the transducer is closer to the organs of interest, allowing higher frequency (5-7.5
MHz) transducers to be used, and higher spatial resolution images to be obtained. The disadvantage is
the small range of the probe, so that endovaginal US does not give the same wide view of the pelvis,
renal tracts and retroperitoneal regions as transabdominal US; the two techniques are complementary.
EVUS overcomes the difficulty of scanning obese women or those who cannot achieve adequate
bladder filling for transabdominal US. The technique may be inappropriate for young girls or elderly
women with vaginal stenosis.
• Explain the technique to the patient (can be likened to a vaginal speculum examination / smear test)
and obtain her verbal consent to perform the examination.
• Male radiologists should have an escort in the room.
Technique:
• The patient should empty her bladder immediately prior to the endovaginal scan.
• While she is doing so, connect the transducer, and recall the endovaginal scanning set up.
• Cover the transducer face with US gel, cover the transducer with a condom secured with tape,
exclude air from the end and apply KY gel to the outside.

• Cover the patient's thighs with paper and ensure that no-one can come into the room unexpectedly.
• Show the patient the transducer. The patient lies supine with her bottom raised on pillows and her
knees bent
• Ask her to relax while you insert the transducer gently. Manoeuvre the transducer to visualise the
organs in the anterior part of the pelvis.
ROUTINE EXAMINATION
1.
Sagittal and parasagittal views
: (Sagittal / oblique relative to uterus)
The
orientation
differs from that of a transabdominal ultrasound scan. In a transabdominal scan, the
central ultrasound pulse travels in an antero-posterior direction through the bladder and the cephalic
end of the uterus appears on the left of the image. In transvaginal scanning, the incident beam travels in
a cephalocaudal direction and the cervix appears at the top of the image, with the corpus of the uterus
below it. In a true sagittal scan, the (empty) bladder can be seen on the ventral (anterior) side.
• With the transducer tip at the external os of the cervix, sweep through the uterus from side to side in
a sagittal plane. Orientate the probe along the long axis of the uterus and examine the endometrium
(hyperintense to myometrium). Measure the AP thickness.
2. Trans-pelvic views:
(Coronal /oblique relative to uterus)
•
Orientation
: Turn the marker on the transducer head to the patient’s right. The cervix still appears
at the top of the image, with the body of the uterus below it. However, now the lateral relations of
the uterus come into view instead of the bladder.
• Sweep up and down and side to side, examining the uterus.
• Relocate the tip of the endovaginal probe in the vaginal fornix and examine the right and left
adnexae in AP-pelvic and trans-pelvic planes.
OBSTETRIC SCANNING.

The following guidelines apply to transabdominal scanning in patients undergoing routine examination
during pregnancy. Record the first day of the patient's last menstrual period (LMP), and ask about
previous pregnancies.
First trimester:
• The patient will need to have a full bladder as for gynaecological pelvic US.
• Scan the uterus and locate the gestation sac:
• Signs of
early pregnancy
include bulkiness of the uterus, loss of the midline echo, and the presence
of a small gestation sac. A gestation sac is not normally visible until 5-6 weeks after the first day of
the last menstrual period (LMP). Measure mean sac diameter and state whether the yolk sac is
visible to provide an estimate of gestation if no fetus is seen.
• Identify
fetus
:
• A
fetal pole
, and
fetal heart motion
become visible at 7-8 weeks.
• From 8-9 weeks, measure the
crown-rump length
(head to buttocks) from which
gestational age can be estimated.
• The
head
and
body
becomes distinguishable at about 10 weeks.
• The

biparietal diameter
(BPD) measurement of the fetal cranium is used to assess
gestational age from about 12 weeks.
• Document the
number of embryos
seen and if there are twins, determine whether monochorionic or
dichorionic.
• Record the presence or absence of
fetal heart activity
• Review the uterus and adnexae for abnormality.
Second and third trimester
• To
measure the BPD
, the fetal cranium must be scanned transversely, at right angles to the midline.
The measurement should be taken at the widest axis of the cranium, usually at the level of the
thalami, below the level of the lateral ventricles. Signs that the correct position has been achieved
include:
• Visualisation of the
thalami
(paired triangles / diamond),
• Visualisation of the
third ventricle
(between thalami) or
cavum septum pellucidum
(parallel anterior parasagittal echoes).
• The cranium and
cerebral hemispheres
should be of equal size and shape on either side of
the midline, producing a symmetrical ovoid cross-section.
• Measure from the leading edge of the proximal skull echoes to the leading edge of the distal skull

echoes, perpendicular to the midline echo.
• Use of the BPD for estimation of fetal age is appropriate up to 28 weeks.
Head circumference
,
measured at the same level, is an alternative method which can be used if the head shape is
abnormal, for example in breech presentation when the head is frequently dolichocephalic.
• If the fetal head cannot be assessed, the
femoral length
is an alternative method for estimating fetal
age.
After about 24 weeks, the
abdominal circumference
can be used to assess fetal growth, and is more
sensitive to intrauterine growth retardation than the BPD.
• The correct level, through the maximum liver area, should show a fairly rounded trunk, with the
junction of umbilical vein and left portal vein visible in the liver and cross-sections of the aorta,
spine and stomach.
• The section should be perpendicular to the long axis of the fetus for accurate measurements.
The position of the
placenta
can be determined from about 14 weeks gestation and is usually anterior in
the uterine cavity.
• The lower segment of the uterus is not fully developed until 32 weeks and a diagnosis of placenta
praevia should not be made before this stage.
• The fetal
spine
is visible from about 15weeks and should be carefully assessed in coronal, sagittal
and transverse planes to identify defects and meningocoeles.
• The
cerebellum

and
cisterna magna
should also be assessed in cases of suspected neural tube
defect; spina bifida is almost always associated with an Arnold Chiari type II malformation.
• The fetal
stomach
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Chapter 3: hepatobiliary imaging
Indications
• Jaundice, upper abdominal pain, dyspepsia, cachexia, some causes of anaemia, organomegaly
Liver
Parenchyma
:
• Turning the patient half-way towards his left allows the liver to slide downwards and into view
better.
• As with almost all upper abdominal organs, ask the patient to hold his breath if he can. This
depresses the diaphragm and pushes the organs further into view. Remember to allow the patient to
breathe again after five to ten seconds.
• Sweep horizontally through the liver. To do this, place the probe against the upper abdomen,
orientated sagittally in the right anterior axillary line. Check that you can see the extreme right-hand
edge of the liver. Adjust the controls as necessary (particularly the depth, as the liver is the largest
internal organ). Then sweep steadily towards the left until you reach the far edge of the left lobe of
the liver. This may be as far away as the left mid-clavicular line.
• Now sweep vertically through the liver. Place the probe orientated axially under the right-hand side
of the ribs, angle it upwards, and check that you can see the top of the liver. Now sweep all the way
down to the bottom, including the Riedel’s lobe if there is one.
• You may need to do two sweeps in each direction, particularly the vertical sweep, to make sure that
you have seen the whole organ each time.

• In some subjects, particularly obese ones, the liver may be completely covered by the lowermost
ribs. A view of part of the right lobe may be obtained by looking between pairs of ribs on the right:
you must rotate the probe so that its plane lies along the intercostal space. It is usually impossible to
see the whole liver this way.
• Learn to describe the major lobes and segments of the liver.
Hepatic veins
These (usually three) run obliquely upwards from the right, middle and left parts of the liver substance
to their common origin at the very upper end of the IVC.
• Place the probe, orientated axially, under the xiphisternum. Tilt it cranially until you can see the
junction of the IVC and the right atrium. You should now be able to see the courses of all three
hepatic veins running into the IVC.
Gallbladder
This almost always lies against the underside of the right lobe of the liver, and always lateral to the
portal vein. Occasionally it may be intrahepatic, and enfolded underneath by liver parenchyma. It is
seldom far from the inferior surface of the liver. Occasionally, too, especially in older people, it may be
ptotic and lie further down towards the right iliac fossa.
• Ensure that the patient is fasted.
• With the probe orientated sagittally, run it sideways from the right-hand edge of the liver along the
inferior surface of the liver towards the portal vein until the gallbladder comes into view.
• Sweep vertically and horizontally through the whole of the gallbladder.
• Be careful to distinguish between acoustic shadows caused by gallstones from shadows caused by
nearby gas-filled bowel loops (especially the duodenal cap). The latter shadows may be ‘dirty’ and
contain echogenic streaks. Turning the patient this way and that may help to sort them out, and
being careful to sweep through the whole of the gallbladder from mouth to fundus.
Cystic duct
This runs from the neck of the gallbladder (medial side) posteromedially towards the common bile duct.
The easiest part to recognise is the corkscrew-shaped spiral valve of Heister at the top end.
Portal tract
• With the probe turned sagittally, sweep along the right lobe of the liver till you see part of the
portal vein

as it runs in from the inferior surface. To see the length of the main part of the portal
vein within the liver, you rotate the probe anti-clockwise from the sagittal so that the plane of
insonation points roughly at the right shoulder, and then tilt it to face medially towards the aorta. In
most people this works when the probe is touching the skin in the mid-clavicular line. With a little
practice, you will learn to put the probe straight down on the patient to show the length of the portal
vein.
• Follow the portal vein down to its origin at the junction of the splenic and superior mesenteric veins,
where there is a slight bulge.
• Of the other two main vessels running through the porta hepatis, the
common bile duct
(CBD) lies
anterolateral and the hepatic artery anteromedial to the portal vein. Thus, when looking in from the
anterolateral side, it is the CBD which appears above the portal vein on the image.
• The tributaries of the CBD (the intrahepatic bile ducts) can be distinguished from the branches of
the portal vein because they generally have brightly echogenic walls.
• If there is not too much bowel gas, you should be able to follow the CBD carefully down through
the head of the pancreas to where it turns towards the medial side of the duodenum. If you can see
two tubes running inferiorly through the right-hand side of the head of the pancreas, the more
posterior one is usually the
pancreatico-duodenal artery
.
• The
hepatic artery
lies more medial to the portal vein. In some people, especially young ones, it
may wind between the portal vein and the CBD. You may be able to follow it back to the coeliac
axis.
Pancreas
The pancreas is generally less bright than the liver in children, but by middle age has as a rule become
brighter than the liver.
• It lies directly behind the gastric antrum or transverse colon which may obscure it. The best way

round this is often to lay the patient on his back, place the probe high over the cartilaginous
xiphisternum with it turned into the axial plane, and aim downwards round the back of the bowel.
• You should see it as a wide inverted ‘U’-shaped curve with the leg on the patient’s left (the tail)
longer than the right. It lies just inferior to the splenic vein, and the head and neck wrap around the
echogenic pad of fat that characteristically surrounds the origin of the superior mesenteric artery.
• The tail runs superiorly and backwards round the vertebral bodies towards the left axilla, so you will
need to turn the probe anticlockwise until it points at the left axilla to see the whole length of the
organ. The tail is generally larger in young people than older ones.
• Sweep up and down across the pancreas, being sure not to miss the uncinate process or the tail.
• You may also be able to see the tail by turning the patient on to his right shoulder and looking at it
through the spleen.
Spleen
This is almost always covered by the lower left ribs, and may lie under the mid-axillary line or some
way in front of it.
• Turn the patient to his right. Align the probe along the intercostal spaces. You may have to explore
the ninth, tenth and eleventh spaces.
• The spleen appears as a curved or kidney-shaped organ of even mid-grey texture. Oddly, the spleen
may absorb very little ultrasound energy so you may have to flatten out the swept gain control in
order to make it appear uniform from front to back.
• You may have limited scope for sweeping across it because of the small acoustic window between
the ribs.
• Asking the patient to hold his breath may help by pushing the spleen down into view, or may make
matters worse by expanding a layer of impenetrable inflated lung between the body wall and the
surface of the spleen.
• The splenic artery and vein run deep from the middle of the deep surface in this view. Find the
splenic hilum if you need to differentiate the spleen from an enlarged left lobe of the liver.
Chapter 4: Renal tract imaging
KIDNEY
Technique
• Scan in the

longitudinal
and
transverse
planes with the patient lying ideally in the anterior oblique
or lateral position.
• Obtain
coronal
image by placing the probe in the flank/rib region, moving the probe posteriorly
until the full kidney is in view.
• If the kidney is in a high position intercostal scanning would be necessary, rotating the probe to
obtain the coronal image free of rib artefacts, and obtain sequential images through the kidney in the
transverse plane.
• Scanning is facilitated by using the
liver as a window
on the right.
• On the left difficulties may arise because of the gastric fundal gas. Identify the
spleen
and use it as
a window to access the left kidney moving the probe intercostally until the whole kidney is
visualised.
• Scanning in the
prone
position is cumbersome in the frail and elderly but ideal in children in whom
is ensures an easy and consistent approach for follow up measurement of renal size.
Anatomy
The normal adult kidney measures between 8 cm and 13 cm in length. Ultrasound size reflects the true
measurement whilst the radiographic size carries a magnification factor of up to 30%.
• There is a dense linear peripheral echo from the
renal capsule
. The renal

parenchyma
consists of
intermediate echoes from the cortex surrounding the hypoechoic renal
pyramids
in the medulla
• central dense echo complex from the
renal sinus fat
and
calyces
• focal echo densities may be seen within the renal pyramids due to reflections from the
arcuate
vessels
.
•
Renal sizes
in adults: usually about 13 cm long and 5 cm wide.
• To get the renal
length
, make sure that both poles of the kidney are shown on the same
image, and the image is as long as it can be.
• To get the
width
and
depth
, you need to find a cross-section of the kidney through its
hilum which is as small as it can be. Then measure the dimension from the renal hilum to
the back of the kidney, and the maximum dimension at right-angles to this.
•
Parenchymal thickness
usually 2.5 cm

• In
children
, the kidneys grow steadily with the height of the child. However, the lengths at any
given age are rather variable. It is particularly important to measure the lengths of the kidneys every
time they are examined as follow-up can be used to check on normal growth.
• The
renal volume
can be calculated from the formula V=d
1
x d
2
x d
3
x 0.523, where d
1
, d
2
and d
3
are the three measurements mutually at right-angles.
Pitfalls and abnormalities
•
Hydronephrosis
. Separation of sinus echoes may be due to causes other than hydronephrosis:
• normal variant in association with an extrarenal pelvis
• Associated with a distended bladder especially in children
• parapelvic cyst
• reflux rather than obstruction
Pseudotumour
Tumours in the kidney may be mimicked by:

• Prominent
column of Bertin
representing cortex between pyramids, unduly large as a normal
variant especially in the kidneys with renal duplication or bifid renal pelvis. The echogenicity
within the column is identical to that of the adjacent cortex and there is no distortion of the adjacent
calyceal echoes.
• Mass “ effect” due to
hypertrophy
of a portion of the kidney due to scarring elsewhere
•
Absent kidney
in the renal fossa should instigate search for ectopic pelvic kidney ; alternatively it
may be atrophic or congenitally absent.
URETER
• Normal
ureters
are difficult to see because of small calibre and retroperitoneal location.
• Intramural portion of the distal ureters are usually visualised terminating as two small projections in
the
trigone
on both sides of the mid line of the posterior bladder wall.
• intermittent jets of urine within the bladder lumen near the trigone are visualised normally on
ultrasound.
BLADDER/PROSTATE/SEMINAL VESICLES
• Longitudinal and transverse imaging rocking probe side to side to cover the full lumen of the
bladder, paying particular attention to side walls on the transverse images and the dome and bladder
base on the longitudinal images.
• The
bladder wall
thickness should be 3 mm when distended and 5 mm in the empty state - less in

children.
• Angling caudally in the mid line behind the pubic bone in the transverse plane enables visualisation
of the
seminal vesicles
which appear as a moustache shaped sonolucent structures.
• The
prostate
lies inferior to the bladder and normally exhibits homogeneous intermediate texture
•
Zonal anatomy
and
capsule
are

not demonstrated on transabdominal scanning. (Transrectal
ultrasound in the radial and longitudinal planes is the best ultrasound technique for parenchymal
assessment and biopsy guidance.)
•
Prostate volume
is normally less than 20 cc (20 grams - since specific gravity of prostate is equal to
1, and direct translation to grams can be made). It is naturally much smaller in pre-pubertal boys.
• The
prostatic volume
is calculated by using the formula for an ellipse i.e. length x width x height x
0.5
• use the same formula for estimation of bladder volume. This correlates roughly with measured
voided volume.
Chapter 5: Lower limb venous duplex and colour Doppler
imaging
Indications

• diagnosis of
deep vein thrombosis
•
insufficiency
due to valvular incompetence
• pre-operative
saphenous vein mapping
prior to bypass surgery
SCANNING TECHNIQUE
Equipment
• High resolution grey scale ultrasound machine
• Colour Doppler reduces scan times significantly
• Spectral Doppler assessment for velocity measurements
• Frequency - 7.5 megahertz linear array vascular probe
• Low velocity setting to detect venous flow

• Sequential systematic examination commencing at the femoral vein in the groin moving the probe
caudally in the transverse plane in 3 - 4 cm steps
• Ensure you apply minimal probe pressure on the skin as veins/venous flow are easily obliterated.
• Scan common femoral and superficial femoral veins transversely in colour Doppler mode as well as
grey scale with the patient in the supine position
• Particular attention to sapheno-femoral junction and bifurcation of superficial/profunda femoris
veins
• Look for intraluminal thrombi and presence of valves
• Compression by probe pressure sweeping the thigh as far as the adductor canal. In the leg examine
in supine position along medial as well as lateral aspects in the transverse plane
• Switch to longitudinal plane and spectral Doppler. Test for flow augmentation by distal limb
compression
• Popliteal and calf veins examine in the decubitus or prone position
Pitfalls

• High frequency of femoral vein duplication up to 46%, thrombus may potentially be missed if it lies
in a duplicated vein
• Detection of small femoral vein may suggest the presence of a duplication
• As the superficial femoral vein approaches the adductor canal in distal one third of the thigh, it lies
more deeply and may become difficult to visualise. A lower frequency, either 5 megahertz or 3.5
megahertz probe may be necessary to evaluate this area especially if the limb is swollen.
• Estimation of calf veins is more time consuming and often not undertaken routinely. Posterior tibial
veins lie more medially usually paired 3 - 4 in number.
• Peroneal veins lie on the lateral side of the calf.
• Anterior tibial veins may be more difficult to identify on routine examination.
Diagnostic criteria
• Sight of intraluminal thrombus provides definitive diagnosis. Acute clot may be anechoic or
hyperechoic.
• A thrombosed vein is thickened and not compressible. Failure to completely compress vein walls
on probe pressure suggests acute or chronic DVT. Poor compressibility occasionally seen in normal
veins at the adductor hiatus.
• Absence of spontaneous flow or loss of phasicity of flow with respiration suggests proximal
thrombus or venous compression.
• Audible and visible augmentation of flow on spectral Doppler by compression of limb distally is a
sign of normal flow. Failure to detect augmentation is consistent with distal obstruction
CAROTID DUPLEX SCANNING
Examination technique
• Patient lies supine with a pillow placed behind the shoulders and the neck extended over the edge of
the pillow. Some patients may be unable to lie flat - examination can then be performed with the
head of the couch raised 45
o
or alternatively assessment can be undertaken in a chair.
• Use a 7.5 Megahertz small footprint vascular probe using
sternomastoid
muscle as a window.

Commence scanning at the root of the neck and ascend transversely in a postero-lateral position to
the bifurcation and beyond in the transverse plane. The
common carotid artery
is round becoming
larger and ovoid in the bulb region prior to bifurcation.
• Repeat scanning in the longitudinal plane noting the presence of any plaques or intimal thickening
and switching to
colour Doppler
to check vessel patency or alterations of flow haemodynamics.
Once abnormal areas are identified more precise measurements made by switching to
spectral
Doppler
.
• Optimal visualisation of the carotid artery and
bifurcation
requires scanning antero-laterally or
postero-laterally with the head straight; sometimes
rotating the patient’s head
contralaterally will
help.
• All arteries exhibit thin
intimal reflection
and denser outline of the
adventitia
with intervening
hyperechoic area representing the
media
.
• The
internal carotid artery

is larger and lies postero-laterally with no branches in the neck, whilst
the
external carotid artery
is more medial and smaller in calibre.
• Colour Doppler shows forward flow in the common carotid and internal carotid arteries whilst a
small amount of
reverse flow
is noted in the jugular bulb normally.
•
Spectral Doppler
shows continuous flow in systole and diastole in the low resistance internal
carotid artery system whilst the external carotid shows characteristic sharp systolic pattern with
reversed flow in diastole due to the high pressure in the external carotid system
Spectral Doppler measurements: technique
• Localise areas of disease and ensure insonation angle is 60
°
or less.
• Determine the area of sampling: choose a site either at or immediately distal to the stenosis. Note
that the signal may be extremely poor if sampling requires scanning through heavily calcified
arterial wall.
• Sample from the centre of the lumen with as small a gate size as possible.
Plaque characteristics
• Note the extent and thickness of the plaque, its composition and surface characteristics such as
irregularity or ulceration.
•
Carotid plaque
is often eccentric and longitudinal scanning does not provide a true picture;
measurement of percentage reduction in diameter and percentage reduction in area of lumen is best
obtained on the transverse images.
•

Peak systolic velocity
in internal carotid artery is the most reliable Doppler parameter. Velocity
does not increase with minor degrees of stenosis until the stenosis reaches 50% (see table).
•
Diastolic velocity
remains normal with arterial stenosis of less than 60%. Beyond this diastolic
velocity increases in proportion to the narrowing.
•
Velocity ratios
. Measurements of carotid velocity may be affected by hypertension, pulse rate,
cardiac output, arterial compliance and cardiovalvular disease. Systolic and diastolic measurements
are influenced by contralateral carotid obstruction. Velocity ratios are used to obviate these effects.
•
Systolic ICA/CCA ratio
- see table below. Peak velocity in ICA at or beyond a stenosis is divided
by a common carotid artery velocity proximal to the stenosis. If systolic ratio is greater than 1.8 it
indicates a greater than 60% reduction of ICA diameter; a ratio greater than 3.7 indicates greater
than 80% ICA stenosis.
•
End Diastolic Ratio
The diastolic velocity in a stenotic area is divided by the end diastolic velocity
in the normal portion of common carotid artery. If this figure is greater than 5.5% it predicts 90%
or greater diameter reduction.
VELOCITIES AND RATIOS IN CAROTID ARTERIES
Diameter
stenosis
(%)
Peak-systolic
velocity
(cm/sec)

End-diastolic
velocity
(cm/sec)
Systolic
velocity
ratio
Diastolic
velocity
ratio
0
1 - 39
40 - 59
60 - 79
80 - 99
<110
<110
<130
>130
>250
< 40
< 40
< 40
> 40
>100
<1.8
<1.8
<1.8
>1.8
>3.7
<2.4

<2.4
<2.4
>2.4
>5.5
Chapter 6: Small parts
General points
• Reset the machine for high resolution and reduced depth. This generally means choosing a probe
with a high frequency and a small near-field artefact, and setting a short focal depth. Linear arrays
often have smaller near-field artefacts than mechanical probes. Reduce the depth of the image
displayed (i.e., enlarge it).
• If you do not have a probe with a short enough focal length, try using a
stand-off
. An ordinary bag
of saline for intravenous infusion will do well. Apply ultrasound gel to the skin, place the bag
carefully on top being sure to squeeze out any air bubbles trapped between the skin and the bag, put
more gel on top of the bag, and place the probe against the bag. You can often get the patient or a
nurse to hold the bag in place. In this way you may place the area of interest beyond the near-field
artefact and in the focal zone.
• Use
small movements
of the transducer head. It is easy to miss a small structure completely if you
go too fast.
Thyroid
• The
lateral lobes
lie on either side of the trachea just above the sternal notch. They have bulbous
lower ends and taper superiorly. They are normally uniformly moderately echogenic. They are
connected by the
isthmus
close to the lower ends, and you can often see the pyramidal lobe sticking

up from this (typically just to the left of the midline) with the end of the thyroglossal ligament
attached to it.
• The
inferior parathyroids
may be just visible as small rounded hypoechogenic dots just behind the
lower ends of the thyroid glands. Commonly neither, or only one, is visible, depending partly upon
the equipment you are using. The
superior parathyroids
are more variable in position, lying
anywhere behind the upper half of the thyroid gland, and are less commonly seen.
• As with any solid organ, sweep through it from above down and from side to side.
• Complete the examination by checking the local lymph nodes, which lie along the carotid chain on
each side behind the lateral lobes.
Thymus
This usually only needs to be examined in babies in the first eighteen months of life, when it may be
necessary to find the cause of a superior mediastinal mass; and occasionally in adults with
immunodeficiency or myasthenia gravis.
• Choose a probe with a small footprint and place it, angled downwards, in the suprasternal notch.
The thymus should appear as a uniformly echo-poor mass enveloping the arch of the aorta, SVC and
other structures. The normal thymus is soft: any suggestion that it is displacing surrounding organs
may be because it is infiltrated with something, e.g. lymphoma.
Scrotum
• Lay the patient flat and support the scrotum by folding a small towel or a large piece of tissue-paper
into a strip and using it as a sling under the scrotum. The patient can hold the ends of the sling in
place. Make sure that casual visitors cannot wander into the consulting-room during the
examination.
• The parenchyma of the testes has uniform medium echogenicity, but like the spleen it has the
curious property of absorbing less ultrasound energy than other tissues. Thus you may have to
flatten out the swept gain settings to prevent the back of the testes from being over-insonated.
• Sweep through each testis and its adnexae in axial and sagittal planes.

• Measure the long and short axes of each testis for comparison.
• Masses in the testis can be difficult to make out because of lack of contrast. Look for the fan-shaped
echogenic fibres of the
rete testis
radiating into the testis from a point on the middle of the posterior
wall. If you have colour or power Doppler, you will see the branches of the
testicular artery
following them out into the parenchyma. Check that none of theses structures is displaced.
• Colour and power Doppler have also been advocated for detection of relative ischaemia in
torsion
of the testis. However, using this method confidently requires experience and familiarity with the
performance of a particular machine.
• Running in a slightly wavy course up the back of the testis you should see the echo-poor
epidydimis
.
• At the upper end, you ought to see the
pampiniform plexus
as a cluster of echolucent dots or curls.
• You may be able to follow the vas and the testicular vessels up the inguinal canal to the
external
inguinal ring
, which is marked by the external iliac vessels emerging into the thigh as the femoral
vessels.
HIPS
Detection of effusions of the hip joint
Ultrasound is the technique of choice. Remember that the iliofemoral ligament forms part of the joint
capsule and inserts into the linea aspera on the front of the femoral neck, but the thinner, less echogenic
synovial membrane underneath it is reflected back up the femoral neck to attach at the margins of the
articular surface. The layers, counting out from the femur, are thus: periosteum and synovial membrane;
joint space proper; outer layer of synovial membrane; and joint capsule (iliofemoral ligament).

• Lay the patient flat. You can usually ask him or her to expose the skin over the hip by pulling up one
side of his or her pants rather than removing them. Align the probe slightly obliquely so that it lies
along the femoral neck and you can see the lateral edge of the acetabulum, the labrum and the broad
echogenic anterior band of the
iliofemoral ligament
. Note that the front of the femur appears flat
from this perspective, as the angle at the femoral neck does not come into the image.
• In a good subject, you should be able to see all the layers in front of the femoral neck forming the
anterior pouch of the joint space.
• Measure the anteroposterior depth of the joint space proper and compare with the other side. If you
do see an effusion, consider immediate discussion with the clinician over whether it should be
aspirated.
Assessment of dysplasia of the acetabulum
This is indicated in neonates and young infants. It is surprisingly tricky to do, and depends upon
accurate placement of the probe across the hip joint.
• Ask the mother or carer to turn the baby on his side.
• Find a true coronal view through the hip joint that shows
1. The iliac bone where it reaches the triradiate cartilage at the base of the acetabulum; and
2. The labrum including its base which is made of echo-poor hyaline cartilage at this age, and
its echogenic, fibrocartilaginous tip.
• The probe must now be rotated so that the iliac wing appears to run in a straight line across the
image away from the joint. Thus, it must not run either ‘uphill’ towards the iliac crest or ‘downhill’
towards the gluteal fossa.
• Standard observations and measurements can now be made on the image.
Infant brain
Much of the brain can be seen by ultrasound through the anterior fontanelle until it closes, normally
some time in the second six months of life.
• Choose a probe with a small footprint, a high frequency (typically 5-7.5 MHz depending on the size
of the head) and a wide angle of arc.
• Find a true

sagittal
image passing through the
cingulate gyrus
on one side or the other,
the corpus
callosum
, and beneath this in succession the
cavum septi pellucidi
, the
third ventricle
, the
aqueduct
, the
fourth ventricle
and the
foramen of Magendie
with the
vermis of the cerebellum
behind it. If you can see a faint white streak running obliquely through the forebrain, this may be the
falx
caught at a slight angle. Gentle rotation of the probe into the true sagittal plane should eliminate
it.
• Of all the hollow structures on this view, the third ventricle is the narrowest from side to side.
Partial volume effects may mean that it is difficult to see or appears to contain echogenic material.
This can be checked later on the coronal view. The
connexus of the thalamus
is prominent at this
age, passing through the middle of it.
• You now need to tilt the probe one way and then the other to see each
side of the brain

in turn.
However, you have to be careful to rock the probe using its own point as a fulcrum, rather than
sweeping the point of the probe across the surface, as you will lose the image if the probe head
wanders away from the acoustic window formed by the fontanelle. This entails a surprisingly large
movement of the wrist, and may take a little practice.
• Find each
lateral ventricle
in turn, including the anterior and temporal horns at the front of the
body, and the occipital horn behind. The body and occipital horns stick out from the midline a little
further than the anterior horn, so you will have to rotate the probe to get the whole ventricle on to
one image. The
choroid plexus
forms a highly echogenic, worm-like strip winding from the
temporal horns round to the foramina of Monroe, and should be symmetrical.
• Check the
periventricular area
lateral to each lateral ventricle.
• Now turn the probe into the
coronal plane
and look for the
foramina of Monroe
connecting the
underside of the lateral ventricles to the superomedial corners of the third ventricle. Note that the
whole of the lateral ventricles lie superior to the third ventricle as they pass over it (unless there is
absence of the corpus callosum). The fluid-filled viscus separating the two medial walls of the
anterior horns of the lateral ventricles above the third ventricle is the
cavum septi pellucidi
, which
is a constant finding for the first few months of life. The strip of choroid plexus in each lateral
ventricle passes down through the foramen of Monroe into the third ventricle, so a good landmark

for the foramina is where the choroid plexus disappears from the lateral ventricles as you sweep
forward.
• Measure

the
ventricular diameters
if there is any question of hydrocephalus. These are taken at the
level of the foramina of Monroe on a true coronal image. They are defined as the greatest horizontal
distance from the midline to the tip of the lateral ventricle on each side.
• Just behind the foramina of Monroe, the main structures you should be able to make out are: the
Sylvian fissure
entering from each side capped by the T-shaped
operculum
, the rounded
thalamus
forming the concavity on the inferomedial side of each lateral ventricle just behind the foramina of
Monroe, and the
periventricular area
on each side. The many capillaries running through this area
in premature and newborn babies produce the appearance of an echogenic ‘tuft’ radiating out from
each superolateral corner of the lateral ventricles. Further back are the
cerebellum,
which is
considerably more echogenic than the cerebrum, and the fourth ventricle, and further back yet
appear the bodies of the lateral ventricles with the bulkiest parts of the choroid plexuses running
through them. Behind this again, you should be able to see some of the occipital
visual cortex
.
•
Haemorrhage

after birth trauma etc. appears echogenic. It usually starts in the
caudothalamic
groove
on the floor of the anterior horn of the lateral ventricle. It can spread under the ependyma
causing the ventricle to appear outlined in white (
periventriculitis
). It may also burst through to
give
intraventricular haemorrhage
. Here it may be very obvious or it may hide against the side of
or within the choroid plexus. Check the symmetry of the choroid plexuses carefully.
•
Periventricular leukomalacia
appears as irregular white areas. The commonest place to see it is in
the area lateral to the bodies and anterior horns of the lateral ventricles where it must be
distinguished from the normal increased echogenicity.
Muscles and superficial tissues
The setup of the machine is particularly important, and you must ensure that you have a transducer of a
high enough frequency capable of imaging structures very close in to its face. For specialised
applications, transducers with frequencies as high as 10-15 MHz are available.
• With very high frequencies, you may be able to make out the
layers of the skin
(dermis and
epidermis) which are fixed together. The skin as a whole is attached to the
subcutaneous fat
but
this should be able to slide over the underlying structures - checking this is a good test for deep
fixation of a superficial lesion.
•
Fat

has a variable appearance at ultrasound. It may be echo-poor with only a few fibrous septa
showing, or it may be densely echogenic. Either way, the speed of ultrasound through fat is slightly
higher than through watery soft tissues, and this produces two effects:
• Fat layers appear slightly less thick at ultrasound than they really are, and this needs to be
borne in mind when doing biopsies through fat,
• Fat is stored in globules which are literally lens-shaped and distort the ultrasound passing
through them. This produces the notorious haziness of the image behind a layer of fat.
Reducing the transducer frequency or using harmonic imaging if it is available may reduce
this effect.
•
Muscles
show prominent longitudinal striations caused by interfascicular septa, and this can be used
to orientate the probe along the muscle. They are separated from each other by yet more prominent
fibrous septa.
•
Tendons
are generally densely echogenic and the tendon of each muscle extends into the muscle a
characteristic distance.
• The integrity of muscles and tendons can be checked by asking the patient to work them while you
are examining them.
•
Hyaline cartilage
is echo-poor (fibrocartilage is echo-dense) and easily seen. Some cartilages
which are often examined include the costal cartilages, the laryngeal cartilages and the unossified
parts of the child’s skeleton (hips, feet, patellae, etc.).
•
Blood vessels
may be seen as tubes containing no echoes, or a few echoes streaming along them.
They may be easily identified from surrounding soft tissues by using power or colour Doppler.
•

Cysts
are generally echo-free or echo-poor because of their fluid contents, though there are
exceptions such as cysts in the breast. Depending upon the suspected nature of the cyst in question,
you may have to search carefully for a
capsule
or a solid component.
Sebaceous cysts
usually have
echo-poor or echo-free contents and a well-defined capsule.
•
Lymph nodes
are normally echo-poor and classically bean-shaped. Colour Doppler may show the
feeding vessel entering the middle of the concave side, and under good conditions you may also see
fibrous septa running through the node from this point. There are no reliable normal values for the
sizes of superficial lymph nodes.