The MANCHESTER handbook of ppt

ROUTINE EXAMINATION: Sagittal and parasagittal views of uterus, cervix and vagina.. • Image a midline sagittal view of the uterus and measure length from fundus to external os.. Transver

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, 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 severalrevisions of the book, and all constructive comments, drawing our attention to inaccuracies and

omissions etc., will be gratefully received

Brennan WilsonDepartment of RadiologyRoyal Manchester Children’s Hospital

PendleburyManchester M27 4HATel: (0161) 794 4696 (switch)(0161) 727 2204 (direct)(0161) 727 2460 (fax)email: Brennan.Wilson@man.ac.uk

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, 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 order

to 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 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

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 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 patientswith 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’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 youunderstand 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 bendingsideways unnecessarily

• Check that the appropriate transducer is connected and that the system is set up for the type ofexamination 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 maywant 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 hisbody 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 showtoo 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 (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 thepatient’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 mosttransducers 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 lowerresolution

• 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 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 the

area 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 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 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 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 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 a

magnified 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 the

faintest 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 the

patient, 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 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 acousticshadowing, 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 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

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, transducertransmission 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, ectopiccalcification 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 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 herbladder

• 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 patientsmay 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 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 Uterinesize 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 exceed5mm 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 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 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 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 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 cm3

• In post-menopausal women, volumes vary from 1-4 cm3 They have no obvious folliclesand 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 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 (5-7.5MHz) 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 herknees bent

• Ask her to relax while you insert the transducer gently Manoeuvre the transducer to visualise theorgans 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 cephalicend 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 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 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 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 leftadnexae 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 skullechoes, 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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