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 diagnosticradiology.

Written and edited by:Brennan Wilson, Consultant Paediatric Radiologist, Manchester Children’s Hospitals

Hari Mamtora, Consultant Radiologist, Hope Hospital, SalfordJane 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 andomissions etc., will be gratefully received.

Brennan WilsonDepartment of Radiology

Royal Manchester Children’s HospitalPendlebury

Manchester M27 4HATel: (0161) 794 4696 (switch)

(0161) 727 2204 (direct)(0161) 727 2460 (fax)

email: Brennan.Wilson@man.ac.uk

Introduction

This handbook is designed for first and second year specialist registrars in radiology. It assumes abasic understanding of ultrasound physics and technology, and the rudiments of cross-sectionalanatomy, and is designed to help you from that background towards the practical business of workingan ultrasound machine. You will find a summary of the main controls of an ultrasound machine, andpoints 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 toreplace a textbook of any of these subjects.

So far, the booklet reflects the collected experience of the three editors with valued comments fromsome colleagues and current SpRs (notably Ralph Jackson). However, it is admittedly still experimentaland would obviously benefit from as many constructive comments as possible. We do not know ofanother such handbook being available, and we realise that we may have committed omissions anderrors of fact, and we have also almost certainly failed to realise some of the things that SpRs finddifficult 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. Wewould very much like to collect as many of the booklets as possible at the end of the year, in orderto be able to use these comments to re-edit the book. We will be glad to make arrangements to givethe originals back to you if you like.

• Please feel free to send any comments you have to me - anonymously if you like - or to theelectronic 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 scanning2 Gynaecology and obstetrics3 Hepatobiliary imaging4 Renal tract5 Lower limb venous duplex imaging and colour Doppler of the neck6 Small parts

Chapter 1: Principles of ultrasound scanning

Approach to the patientThe same professional courtesy is expected in the ultrasound examination room as anywhere else inmedicine.• 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 complicatedprocedure, 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’smodesty 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 tomake 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 structureswithin the organ such as blood vessels will appear to move steadily along their courses, whereasrounded 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 abnormalfindings. Your colleagues may have to use these images for future comparisons, so try to include asmuch 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 pressfirmly against the bowel for a few minutes, and literally squeeze the bowel out of the way (thegraded compression technique). Ask your patient’s permission before you do it, and desist if youare requested.

Ultrasound machine settings and their meanings

The parameters preset on the machine will enable you to start scanning but use the followinginformation to help you understand the controls and modify settings to obtain the best diagnostic imagein individual patients. Images are viewed from the patient’s right for longitudinal scans, and from thepatient’s feet for transaxial scans.

• Transducer frequency is the frequency of the signal emitted. On some modern machines this canbe selected electronically from a range within the same transducer: however, nowadays mosttransducers are still single-frequency only and you will have to toggle between transducers or plug anew one in to the socket on the front or side of the machine. High frequency probes have a betterlongitudinal resolution but less penetrating power through tissues, and are typically used forchildren and small organs or ones close to the transducer face. Low frequency probes can be usedto penetrate deep into large areas such as adult abdomens but at the cost of a somewhat lowerresolution.

• Transmit power is the level of power delivered into the body, given on a logarithmic scale. Use thelowest transmit power necessary for diagnosis. If you need to increase the transmit power to see farinto 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 thearea of interest are all contained within the grey scale on the screen. Common mistakes here are toallow the back of the image to become too dark, e.g. when examining the back of a large liver, or toallow structures seen behind a fluid cavity (for example, the adnexae behind the urinary bladder) tobecome too bright in the acoustic enhancement.

• Receive gain is the overall amplification applied, and has the effect of changing the brightness ofthe whole image.

• Time gain compensation (gain curve, swept gain): This compensates for acoustic loss in thedeeper tissues from absorption, scatter and reflection of the US beam. The aim is to show structuresof the same acoustic strength as echoes of equal amplitude, whatever their depth. On most modernmachines, 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 dealof swept gain compensation is built into the machine so it is often convenient to start with the slidesin 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 narrowestafter passing through the near zone and before fanning out into the far zone. Thus, the lateralresolution of the image is greatest here. Position it at or just behind the area of interest. Multiplefocal zones are applicable to large static structures, but may cause a drop in frame rate, which canmake any movement while scanning appear intrusive.

• RES (regional expansion selection): This facility is available on Acuson machines and produces amagnified image in a selected area of interest with increased frame rate and spatial resolution. Keepthe 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 thefaintest and the strongest signals that can be displayed on the screen. Many machines have a defaultsetting of 48-55 dB. Increasing the dynamic range produces a greyer, flatter image. Decreasing itincreases the apparent ‘contrast’ in the image and emphasises small changes in signal strength - thiscan be helpful where abnormalities are very close to the same shade of grey as the surroundingtissue, for example metastases in the liver or masses in the testis. However, it also increases thevisual ‘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, itdoes 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 thepatient, e.g. in the fat of the anterior abdominal wall, or gas filled bowel. This produces a ‘ghost’ ofthe interface responsible at twice the depth, and may be mistaken for pathology. Try looking from adifferent angle to see what happens to the suspicious echo.

• Acoustic shadowing. A user-friendly artefact which allows identification of calculi as stronglyreflective structures which do not allow passage of ultrasound energy beyond them. A dark shadowis seen behind a strong echo. Gas in bowel or lung generally produces a less intense acousticshadowing, or bright ‘comet-tail’ artefacts.

• Acoustic enhancement. Passage of ultrasound through a tissue which is less attenuating than usualproduces a relative increase in echo amplitude distal to the area, a so called ‘bright-up’. This canhelp to differentiate fluid-containing cysts from other hyporeflective but solid masses. Remember toadjust the gain if you are looking at structures behind a fluid collection, e.g. behind the bladder.

TroubleshootingIf 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, topenetrate obesity; reduce the dynamic range, increase persistence to reduce the noise. Some verymodern 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 forgynaecology 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 USprobe. 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 endometriumand 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 smallerin post-menopausal women.

• The uterus can be tilted in any direction so angle the probe if the uterus lies oblique to the midlineof the patient. A uterus may be anteflexed (anteverted) (fundus pointing towards anterior abdominalwall)or retroflexed retroverted (pointing towards sacrum). It may have to be measured in twoportions.

• Image a zoomed sagittal view of the uterus showing the bright central echoes representing theendometrium plus any tissue in the endometrial cavity. The double layer thickness of bright echoesin the AP direction may measure up to 15 mm during the menstrual cycle, but should not exceed5mm after the menopause.

• Intrauterine contraceptive devices produce strong acoustic reflections and acoustic shadowingfrom 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 yourtransducer 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 reproductiveyears).

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 abovethe 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 thereproductive age group). If you have difficulty finding the ovaries, use the internal iliac vessels as aguide, the ovaries usually lying medial to the vein. Other favourite hiding places are the pouch ofDouglas, behind or above the uterine fundus or adjacent to the cervix. You may need to angleobliquely 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 regressin the luteal phase of the menstrual cycle.

• Ovarian volumes: Volume is estimated by multiplying the anteroposterior, transverse andlongitudinal diameters and dividing by 2.

• In childhood, size varies with age. Follicles may be seen up to age four from maternaltransplacental ovarian stimulation; premenarchal follicles may start to appear from age 8.

• In the reproductive years, volumes vary from 6-14 cm3.• In post-menopausal women, volumes vary from 1-4 cm3. They have no obvious follicles

and may be more difficult to see. They should not exceed about 8 cm3 in volume andobvious asymmetry in size should be considered abnormal.

• The broad ligament also contains the fallopian tubes (normally invisible), uterine and ovarianvessels and supporting ligaments.

• The important objective in this circumstance is to exclude ovarian enlargement or an adnexalmass, e.g. hydrosalpinx, cysts, free fluid, remembering to check for masses displaced up out of thepelvis.

• Image longitudinal views of the right and left kidneys (q.v.) to exclude renal tract abnormality, suchas hydronephrosis or congenital anomaly. Review the retroperitoneum, liver, and peritoneal spacesif appropriate.

ENDOVAGINAL ULTRASOUND

In endovaginal US the transducer is closer to the organs of interest, allowing higher frequency (5-7.5MHz) transducers to be used, and higher spatial resolution images to be obtained. The disadvantage isthe 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 adequatebladder filling for transabdominal US. The technique may be inappropriate for young girls or elderlywomen 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, thecentral ultrasound pulse travels in an antero-posterior direction through the bladder and the cephalicend of the uterus appears on the left of the image. In transvaginal scanning, the incident beam travels ina cephalocaudal direction and the cervix appears at the top of the image, with the corpus of the uterusbelow 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 ina 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 ofthe 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 examinationduring pregnancy. Record the first day of the patient's last menstrual period (LMP), and ask aboutprevious 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 ofthe last menstrual period (LMP). Measure mean sac diameter and state whether the yolk sac isvisible 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 thethalami, below the level of the lateral ventricles. Signs that the correct position has been achievedinclude:

• 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 isabnormal, 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 fetalage.

After about 24 weeks, the abdominal circumference can be used to assess fetal growth, and is moresensitive to intrauterine growth retardation than the BPD.

Chapter 3: hepatobiliary imaging

Indications• Jaundice, upper abdominal pain, dyspepsia, cachexia, some causes of anaemia, organomegaly

LiverParenchyma:• 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 tobreathe 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-handedge of the liver. Adjust the controls as necessary (particularly the depth, as the liver is the largestinternal organ). Then sweep steadily towards the left until you reach the far edge of the left lobe ofthe 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 sideof the ribs, angle it upwards, and check that you can see the top of the liver. Now sweep all the waydown 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 thatyou have seen the whole organ each time.

• In some subjects, particularly obese ones, the liver may be completely covered by the lowermostribs. 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 tosee the whole liver this way.

• Learn to describe the major lobes and segments of the liver.

Hepatic veinsThese (usually three) run obliquely upwards from the right, middle and left parts of the liver substanceto 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 threehepatic veins running into the IVC.

GallbladderThis almost always lies against the underside of the right lobe of the liver, and always lateral to theportal vein. Occasionally it may be intrahepatic, and enfolded underneath by liver parenchyma. It isseldom far from the inferior surface of the liver. Occasionally, too, especially in older people, it may beptotic 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’ andcontain echogenic streaks. Turning the patient this way and that may help to sort them out, andbeing careful to sweep through the whole of the gallbladder from mouth to fundus.

Cystic ductThis 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 portalvein 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. Inmost people this works when the probe is touching the skin in the mid-clavicular line. With a littlepractice, you will learn to put the probe straight down on the patient to show the length of the portalvein.

• 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) liesanterolateral and the hepatic artery anteromedial to the portal vein. Thus, when looking in from theanterolateral 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 ofthe 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 throughthe head of the pancreas to where it turns towards the medial side of the duodenum. If you can seetwo tubes running inferiorly through the right-hand side of the head of the pancreas, the moreposterior one is usually the pancreatico-duodenal artery.

• The hepatic artery lies more medial to the portal vein. In some people, especially young ones, itmay wind between the portal vein and the CBD. You may be able to follow it back to the coeliacaxis.

PancreasThe pancreas is generally less bright than the liver in children, but by middle age has as a rule becomebrighter 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 cartilaginousxiphisternum 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 theechogenic 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 willneed to turn the probe anticlockwise until it points at the left axilla to see the whole length of theorgan. 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.

SpleenThis is almost always covered by the lower left ribs, and may lie under the mid-axillary line or someway 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 inorder to make it appear uniform from front to back.

• You may have limited scope for sweeping across it because of the small acoustic window betweenthe ribs.

• Asking the patient to hold his breath may help by pushing the spleen down into view, or may makematters worse by expanding a layer of impenetrable inflated lung between the body wall and thesurface of the spleen.

• The splenic artery and vein run deep from the middle of the deep surface in this view. Find thesplenic 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 thetransverse 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 isvisualised.

• Scanning in the prone position is cumbersome in the frail and elderly but ideal in children in whomis ensures an easy and consistent approach for follow up measurement of renal size.

AnatomyThe normal adult kidney measures between 8 cm and 13 cm in length. Ultrasound size reflects the truemeasurement 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 sameimage, 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 itshilum which is as small as it can be. Then measure the dimension from the renal hilum tothe 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 everytime they are examined as follow-up can be used to check on normal growth.

• The renal volume can be calculated from the formula V=d1 x d2 x d3 x 0.523, where d1, d2 and d3

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 echogenicitywithin the column is identical to that of the adjacent cortex and there is no distortion of the adjacentcalyceal 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 thebladder, paying particular attention to side walls on the transverse images and the dome and bladderbase on the longitudinal images.

• The bladder wall thickness should be 3 mm when distended and 5 mm in the empty state - less inchildren.

• Angling caudally in the mid line behind the pubic bone in the transverse plane enables visualisationof 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 parenchymalassessment and biopsy guidance.)

• Prostate volume is normally less than 20 cc (20 grams - since specific gravity of prostate is equal to1, 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 x0.5

• use the same formula for estimation of bladder volume. This correlates roughly with measuredvoided volume.

Chapter 5: Lower limb venous duplex and colour Dopplerimaging

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 liesin 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 3.5megahertz 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 tibialveins 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 normalveins at the adductor hiatus.

• Absence of spontaneous flow or loss of phasicity of flow with respiration suggests proximalthrombus or venous compression.

• Audible and visible augmentation of flow on spectral Doppler by compression of limb distally is asign 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 thehead of the couch raised 45o 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 tothe bifurcation and beyond in the transverse plane. The common carotid artery is round becominglarger and ovoid in the bulb region prior to bifurcation.

• Repeat scanning in the longitudinal plane noting the presence of any plaques or intimal thickeningand 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 spectralDoppler.

• Optimal visualisation of the carotid artery and bifurcation requires scanning antero-laterally orpostero-laterally with the head straight; sometimes rotating the patient’s head contralaterally willhelp.

• All arteries exhibit thin intimal reflection and denser outline of the adventitia with interveninghyperechoic area representing the media.

• The internal carotid artery is larger and lies postero-laterally with no branches in the neck, whilstthe external carotid artery is more medial and smaller in calibre.

• Colour Doppler shows forward flow in the common carotid and internal carotid arteries whilst asmall amount of reverse flow is noted in the jugular bulb normally.

• Spectral Doppler shows continuous flow in systole and diastole in the low resistance internalcarotid artery system whilst the external carotid shows characteristic sharp systolic pattern withreversed 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 calcifiedarterial 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 bestobtained on the transverse images.

• Peak systolic velocity in internal carotid artery is the most reliable Doppler parameter. Velocitydoes 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 diastolicvelocity 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 measurementsare 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 dividedby a common carotid artery velocity proximal to the stenosis. If systolic ratio is greater than 1.8 itindicates a greater than 60% reduction of ICA diameter; a ratio greater than 3.7 indicates greaterthan 80% ICA stenosis.

• End Diastolic Ratio The diastolic velocity in a stenotic area is divided by the end diastolic velocityin 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

Diameterstenosis(%)

Peak-systolicvelocity (cm/sec)

End-diastolicvelocity (cm/sec)

Systolicvelocityratio

Diastolicvelocity ratio

0 1 - 3940 - 5960 - 7980 - 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 arraysoften have smaller near-field artefacts than mechanical probes. Reduce the depth of the imagedisplayed (i.e., enlarge it).

• If you do not have a probe with a short enough focal length, try using a stand-off. An ordinary bagof saline for intravenous infusion will do well. Apply ultrasound gel to the skin, place the bagcarefully on top being sure to squeeze out any air bubbles trapped between the skin and the bag, putmore gel on top of the bag, and place the probe against the bag. You can often get the patient or anurse to hold the bag in place. In this way you may place the area of interest beyond the near-fieldartefact and in the focal zone.

• Use small movements of the transducer head. It is easy to miss a small structure completely if yougo 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 areconnected by the isthmus close to the lower ends, and you can often see the pyramidal lobe stickingup from this (typically just to the left of the midline) with the end of the thyroglossal ligamentattached to it.

• The inferior parathyroids may be just visible as small rounded hypoechogenic dots just behind thelower ends of the thyroid glands. Commonly neither, or only one, is visible, depending partly uponthe equipment you are using. The superior parathyroids are more variable in position, lyinganywhere 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.

ThymusThis usually only needs to be examined in babies in the first eighteen months of life, when it may benecessary to find the cause of a superior mediastinal mass; and occasionally in adults withimmunodeficiency 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 andother structures. The normal thymus is soft: any suggestion that it is displacing surrounding organsmay 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 inplace. Make sure that casual visitors cannot wander into the consulting-room during theexamination.

• The parenchyma of the testes has uniform medium echogenicity, but like the spleen it has thecurious property of absorbing less ultrasound energy than other tissues. Thus you may have toflatten 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 posteriorwall. If you have colour or power Doppler, you will see the branches of the testicular arteryfollowing 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 torsionof the testis. However, using this method confidently requires experience and familiarity with theperformance of a particular machine.

• Running in a slightly wavy course up the back of the testis you should see the echo-poorepidydimis.

• 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 femoralvessels.

HIPS

Detection of effusions of the hip jointUltrasound is the technique of choice. Remember that the iliofemoral ligament forms part of the jointcapsule and inserts into the linea aspera on the front of the femoral neck, but the thinner, less echogenicsynovial membrane underneath it is reflected back up the femoral neck to attach at the margins of thearticular 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 liesalong the femoral neck and you can see the lateral edge of the acetabulum, the labrum and the broadechogenic anterior band of the iliofemoral ligament. Note that the front of the femur appears flatfrom 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 theanterior pouch of the joint space.

• Measure the anteroposterior depth of the joint space proper and compare with the other side. If youdo see an effusion, consider immediate discussion with the clinician over whether it should beaspirated.

Assessment of dysplasia of the acetabulumThis is indicated in neonates and young infants. It is surprisingly tricky to do, and depends uponaccurate 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; and2. 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 brainMuch of the brain can be seen by ultrasound through the anterior fontanelle until it closes, normallysome 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, theaqueduct, the fourth ventricle and the foramen of Magendie with the vermis of the cerebellumbehind it. If you can see a faint white streak running obliquely through the forebrain, this may be thefalx caught at a slight angle. Gentle rotation of the probe into the true sagittal plane should eliminateit.

• 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 thisage, 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 thansweeping 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 largemovement 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 thebody, and the occipital horn behind. The body and occipital horns stick out from the midline a littlefurther than the anterior horn, so you will have to rotate the probe to get the whole ventricle on toone image. The choroid plexus forms a highly echogenic, worm-like strip winding from thetemporal 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 thewhole of the lateral ventricles lie superior to the third ventricle as they pass over it (unless there isabsence of the corpus callosum). The fluid-filled viscus separating the two medial walls of theanterior horns of the lateral ventricles above the third ventricle is the cavum septi pellucidi, whichis a constant finding for the first few months of life. The strip of choroid plexus in each lateralventricle passes down through the foramen of Monroe into the third ventricle, so a good landmarkfor the foramina is where the choroid plexus disappears from the lateral ventricles as you sweepforward.

• Measure the ventricular diameters if there is any question of hydrocephalus. These are taken at thelevel of the foramina of Monroe on a true coronal image. They are defined as the greatest horizontaldistance 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: theSylvian fissure entering from each side capped by the T-shaped operculum, the rounded thalamusforming the concavity on the inferomedial side of each lateral ventricle just behind the foramina ofMonroe, and the periventricular area on each side. The many capillaries running through this areain premature and newborn babies produce the appearance of an echogenic ‘tuft’ radiating out fromeach superolateral corner of the lateral ventricles. Further back are the cerebellum, which isconsiderably more echogenic than the cerebrum, and the fourth ventricle, and further back yetappear the bodies of the lateral ventricles with the bulkiest parts of the choroid plexuses runningthrough 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 caudothalamicgroove on the floor of the anterior horn of the lateral ventricle. It can spread under the ependymacausing the ventricle to appear outlined in white (periventriculitis). It may also burst through togive intraventricular haemorrhage. Here it may be very obvious or it may hide against the side ofor 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 inthe area lateral to the bodies and anterior horns of the lateral ventricles where it must bedistinguished from the normal increased echogenicity.

Muscles and superficial tissuesThe setup of the machine is particularly important, and you must ensure that you have a transducer of ahigh enough frequency capable of imaging structures very close in to its face. For specialisedapplications, 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 butthis should be able to slide over the underlying structures - checking this is a good test for deepfixation of a superficial lesion.

• Fat has a variable appearance at ultrasound. It may be echo-poor with only a few fibrous septashowing, or it may be densely echogenic. Either way, the speed of ultrasound through fat is slightlyhigher 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 beborne in mind when doing biopsies through fat,

• Fat is stored in globules which are literally lens-shaped and distort the ultrasound passingthrough 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 reducethis effect.

• Muscles show prominent longitudinal striations caused by interfascicular septa, and this can be usedto orientate the probe along the muscle. They are separated from each other by yet more prominentfibrous septa.

• Tendons are generally densely echogenic and the tendon of each muscle extends into the muscle acharacteristic distance.

• The integrity of muscles and tendons can be checked by asking the patient to work them while youare examining them.

• Hyaline cartilage is echo-poor (fibrocartilage is echo-dense) and easily seen. Some cartilageswhich are often examined include the costal cartilages, the laryngeal cartilages and the unossifiedparts 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 areexceptions 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 haveecho-poor or echo-free contents and a well-defined capsule.

• Lymph nodes are normally echo-poor and classically bean-shaped. Colour Doppler may show thefeeding vessel entering the middle of the concave side, and under good conditions you may also seefibrous septa running through the node from this point. There are no reliable normal values for thesizes of superficial lymph nodes.