2. US exam for thyroid gland
• High-resolution ultrasonography (USG) is the most sensitive
imaging modality available for examination of the thyroid
gland and associated abnormalities.
Normal Anatomy
• The thyroid gland is a butterfly-shaped organ located in the
midline of the anterior neck.
• It has two elongated lateral lobes (right and left), and is
connected by the isthmus
Normal thyroid lobe dimensions are:
• The length of the lateral lobes is approximately 4–5 cm, with
the transverse and antero-posterior diameter of the lateral
lobes being approximately 2 cm
• the thickness of the isthmus being less than 0.5 cm
3. The parenchymal echogenicity of a normal thyroid
gland is:
• homogeneous and higher than the overlying strap muscles
of the neck.
On a cross-sectional image
• common carotid arteries and the internal jugular veins are
typically visualized laterally adjacent to both thyroid
lobes
• The esophagus is usually located to the left of the trachea.
The parathyroid glands lie close to the deep surface of the
thyroid gland but are generally unseen on US when they
are normal.
• Some level lymph nodes can be seen adjacent to the
lower poles.
4. • Normal transverse US of thyroid gland. Cross-sectional US shows
normal thyroid glands and surrounding structures.
• Both thyroid glands show homogeneous parenchymal echogenicity
higher than anterior strap muscles.
• Both CCAs run laterally adjacent to both thyroid lobes and infrahyoid
strap muscles overlie thyroid gland.
• Both SCM muscles are located antero-laterally and longus colli
muscles are seen postero laterally to thyroid gland.
• US = ultrasonography, SCM = sternocleidomastoid muscle, CCA =
common carotid artery, IJV = internal jugular vein,Ant. Strap m =
anterior strap muscle, Longus Colli m = longus colli muscle
5. Indications
1. To confirm presence of a thyroid nodule when physical
examination is equivocal.
2. To characterize a thyroid nodule(s), i.e. to measure the
dimensions accurately and to identify internal structure and
vascularization.
3. To differentiate between benign and malignant thyroid
masses, based on their sonographic appearance.
4. To differentiate between thyroid nodules and other cervical
masses like lymphadenopathy, thyroglossal cyst and cystic
hygroma.
6. 5. To evaluate diffuse changes in thyroid parenchyma.
6. To detect post-operative residual or recurrent tumor in
thyroid bed or metastases to neck lymph nodes.
7. To screen high risk patients for thyroid malignancy like
patients with history of familial thyroid cancer, multiple
endocrine neoplasia (MEN) type II and irradiated neck in
childhood.
8. To guide diagnostic (FNA cytology/biopsy) and
therapeutic interventional procedures.
7. Technique
1- All patients are examined in supine position with
hyperextended neck,
2- a high frequency linear-array transducer (7-15 MHz) is
used which provides adequate penetration
3- A high resolution image. Scanning is done both in
a) Transverse plane
b) Longitudinal plane.
4- Real time imaging of thyroid lesions is performed using
both
a) Gray-scale technique
b) Color Doppler technique.
8. 5- The imaging characteristics of a mass (viz. location, size,
shape, margins, echogenicity, contents and vascular pattern)
should be identified.
6- Fine needle aspiration (FNA) biopsy should be suggested
to the referring physician if required
Normal thyroid gland. (a) Gray scale
ultrasound, transverse scan showing
normal thyroid anatomy
9. Thyroid gland is a highly vascular structure supplied by
superior and inferior thyroid arteries. So
Color and power Doppler ultrasound (US)
It is done to
1. Evaluate vascularity of the thyroid gland
2. Evaluate focal masses of the thyroid gland
10. (b) Arterial vascularization of the thyroid
gland. On color Doppler, the inferior thyroid artery (arrow) is
seen,
(c) Blood flow pattern in normal thyroid gland. On spectral
display, a low resistance flow with a high peak systolic velocity
is obtained
11. Diseases of Thyroid Gland
• The incidence of all thyroid diseases is higher in females
than in males.
• Nodular thyroid disease is the most common cause of
thyroid enlargement.
Majority of patients with thyroid disease present with
• Midline neck swelling, occasionally causing dysphagia
and hoarseness of voice.
Broadly the thyroid diseases are classified into three
categories:
(i) Benign thyroid masses
(ii) Malignant tumors of thyroid gland, and
(iii) Diffuse thyroid enlargement.
12. Thyroid Nodule(s)
• The incidence and development of nodules correlate
directly with age of the patient and is regarded as a part of
normal maturation process of the thyroid gland.
• The incidence of thyroid nodules is very high on USG,
ranging from 50% to 70%.
• Thyroid cancer accounts for less than 7% cases
• The most common cause of benign thyroid nodule is
nodular hyperplasia.
Benign Tumors
• Thyroid adenomas are other common benign neoplasms
of thyroid that are mostly solitary but may also develop as
a part of multi nodular masses.
13. The most reliable criterion for benignity of the nodule on
ultrasound are
1. Iso-or hyper-echogenicity of the thyroid nodule in
conjunction with a spongiform appearance
2. “Ring down” or “comet-tail” artifact or sign is typical of
benign cystic colloid nodule
3. size <1 cm, width > length, presence of hypoechoic halo
around the nodule (fibrous capsule or compressed thyroid
tissue) and coarse/curvilinear calcification are less specific
but may be useful ancillary signs.
4. Perinodular flow or spoke-and-wheel-like appearance of
vessels on color Doppler examination, However, this flow
pattern may also be seen in thyroid malignancy. A complete
avascular nodule is very unlikely to be malignant.
14. Benign thyroid adenoma in a 42-year-old female patient. Transverse gray-
scale ultrasound neck
(a) shows a large well circumscribed oval shaped (width>length), hyperechoic
nodule in a thyroid lobe. The lesion has slight heterogeneous appearance due to
presence of few tiny cystic spaces/clefts. A thin, hypoechoic capsule (arrow) is
noted peripherally.
(b) Color Doppler image (b) demonstrates both central and peripheral vascularity
with characteristic “spoke-and-wheel-like” appearance
15.
16.
17. Malignant tumors of the thyroid are classified
as:
1. Papillary carcinoma (60-80%),
2. Follicular carcinoma (20-25%),
3. Medullary carcinoma (4-5%),
4. Anaplastic carcinoma (3-10%),
5. Lymphoma (5%) and metastases.
The overall sensitivity of thyroid ultrasound for diagnosing
a malignant nodule is 83.3%.
18. Features predictive of malignant nodules includes:
1. Presence of microcalcifications (<2 mm)
2. Local invasion
3. Lymph node metastases
4. Marked hypoechogenicity
5. Irregular margins
6. Solid composition
7. Absence of a hypoechoic halo around the nodule
8. Size >1 cm, taller-than-wide-shape
9. An intra nodular vascularity
• Multiplicity of the nodule is not an indicator of benignity.
• The incidence of malignancy is same in solitary nodules as it is
in multiple nodules.
• Interval growth of nodules is a non-specific characteristic.
19. Microcalcifications are most commonly found in
1. Papillary carcinoma
2. Medullary carcinoma thyroid and in their
metastases(lymph node or hepatic).
Micro calcifications appear as
• punctuate hyperechoic foci with or without posterior
acoustic shadowing.
• Rarely, microcalcifications can be found in follicular and
anaplastic thyroid carcinomas and certain benign lesions
like follicular adenoma, multinodular goitre and
Hashimoto’s thyroiditis.
20. Local invasion of adjacent structures and metastases to
regional cervical lymph nodes are highly specific signs of
thyroid malignancy.
• They occur more frequently in medullary carcinoma
(50% cases) than papillary carcinoma (40% cases).
21. The most common pattern of vascularity in thyroid
malignancy is
• Marked intrinsic hyper vascularity.
On color Doppler examination
1. More flow is demonstrated in the central portion of the
tumor than in the surrounding thyroid parenchyma
[Figure 6].
2. Increased vascularity with distortion of sinus fat is seen
within the metastatic lymph nodes.
3. Thyroid lymphomas are hypo-vascular with chaotic
vessels; however, neck vessel encasement may be
present
22.
23. Diffuse Thyroid Diseases
• The common conditions that present as diffuse
enlargement of the thyroid gland include multinodular
goitre, Hashimoto’s(lymphocytic) thyroiditis,
de-Quervain’s subacute thyroiditis and Graves’ disease.
• The sonographic features of these processes may be
similar but they have different biochemical profile and
clinical presentations. Hence, in these conditions,
ultrasound findings should be viewed in relation to
clinical and biochemical status of the patient.
24. Multinodular goitre (MNG)
• It is the commonest cause of diffuse asymmetric
enlargement of the thyroid gland.
• Females between 35-50 years of age are most commonly
affected.
Histologically
• Colloid [Figure 7] or adenomatous [Figure 8] form of
MNG is common.
The ultrasound diagnosis rests on the finding of
• Multiple nodules within a diffusely enlarged gland.
• A diffusely enlarged thyroid gland with multiple nodules
of similar US appearance and with no normal intervening
parenchyma is highly suggestive of benignity, thereby
making FNA biopsy unnecessary
25. • Most of the nodules are iso-or hyper-echoic in nature;
when enlarged provide heterogeneous echo pattern to the
gland.
These goitrous nodules often undergo degenerative
changes that correspond to their USG appearances:
• Cystic degeneration gives anechoic appearance to the
nodule,
• Hemorrhage or infection within the cyst is seen as
moving internal echoes/septations,
• Colloidal degeneration produces comet-tail artifact, while
dystrophic calcification is often course or curvilinear.
26. • The assessment of nodule vascularity is very useful in
differentiating MNG from multifocal carcinoma.
• Nodule with intrinsic vascularity and other features of malignancy
can be targeted for biopsy, in preference to other nodules
27.
28. Graves’ disease (thyrotoxicosis)
• It is an autoimmune disease characterized by
thyrotoxicosis.
• Females between 20 and 50 years are most commonly
affected. On gray-scale USG, thyroid is diffusely
enlarged (2-3 times its normal size), hypoechoic and
heterogeneous.
• Color flow imaging reveals a spectacular “thyroid
inferno” with marked hyper vascularity
29. Hashimoto’s thyroiditis(chronic lymphocytic
thyroiditis)
• It is an autoimmune disorder leading to destruction of the
gland and hypothyroidism.
• It occurs predominantly in females over 40 years of age.
• Painless, diffuse enlargement of thyroid gland is the most
common clinical presentation.
Clinically
• Hashimoto’s thyroiditis may present with formation of
goitre with or without disturbance of thyroid function.
• Children with hypothyroidism usually have growth
failure and delayed puberty.
30. The characteristic US appearance [Figures 9 and
10] is:
• focal or diffuse glandular enlargement with coarse,
heterogeneous and hypoechoic parenchymal echo pattern.
• Presence of multiple discrete hypoechoic micronodules
(1-6mm size) is strongly suggestive of chronic thyroiditis.
• Fine echogenic fibrous septae may produce a pseudolobulated
appearance of the parenchyma.
Color Doppler may demonstrate slight to
• markedly increased vascularity of the thyroid parenchyma.
• Increased vascularity seems to be associated with
hypothyroidism, likely due to trophic stimulation of
thyroid-stimulating hormone.
34. Doppler ultrasound techniques requires an
understanding of three key components:
1. The capabilities and limitations of doppler
ultrasound
2. The different parameters which contribute to the
flow display
3. Blood flow in arteries and veins.
35. BASIC PRINCIPLES
• Ultrasound images of flow, whether color flow or
spectral Doppler, are essentially obtained from
measurements of movement.
In ultrasound scanners
• a series of pulses is transmitted to detect movement of blood.
• Echoes from stationary tissue are the same from pulse to pulse.
• Echoes from moving scatterers exhibit slight differences in the
time for the signal to be returned to the receiver (Figure 1).
• These differences can be measured as a direct time difference
or, more usually, in terms of a phase shift from which the
`Doppler frequency' is obtained (Figure 2).
• They are then processed to produce either a color flow display
or a Doppler sonogram.
36.
37.
38. • As can be seen from Figures 1 and 2, there has to be motion in the
direction of the beam;
• If the flow is perpendicular to the beam, there is no relative motion
from pulse to pulse.
The size of the doppler signal is dependent on:
1. Blood velocity: as velocity increases, so does the Doppler
frequency;
2. Ultrasound frequency: higher ultrasound frequencies give
increased Doppler frequency. As in B-mode, lower ultrasound
frequencies have better penetration. The choice of frequency is a
compromise between better sensitivity to flow or better penetration
3. The angle of insonation: the Doppler frequency increases as the
Doppler ultrasound beam becomes more aligned to the flow
direction (the angle between the beam and the direction of flow
becomes smaller).
• This is of the utmost importance in the use of Doppler
ultrasound. The implications are illustrated schematically in
Figure 3.
39.
40. Continuous Wave and Pulsed Wave
Continuous wave systems use:
• continuous transmission and reception of ultrasound
(Figure 4).
Doppler signals :
1. Obtained from all vessels in the path of the ultrasound
beam (until the ultrasound beam becomes sufficiently
attenuated due to depth).
2. It is unable to determine the specific location of velocities
within the beam and cannot be used to produce color flow
images.
41.
42. ULTRASOUND FLOW MODES
1- Color-flow mode
• Color-flow Doppler provides an immediately qualitative
evaluation of the blood flow of different organs and
tissues.
• The vascularity of a structure is estimated subjectively
considering the extension of a tissue with colored pixels
during a continuous real time exam.
• Different than Spectral mode, Color-flow mode is a
simple, rapid and functional method of evaluation,
which has been applied for farm practical purposes
43. The current Doppler equipment offer two different modes of
color-flow imaging:
1. Color-flow
2. Spectral mode
3. Power / energy / amplitude flow
• The classic color-flow mode use two distinct colors, usually
variations of red and blue colors, to represent the vascular
blood perfusion of a structure.
• Also, colored pixels indicate the blood red cells direction in
relation to the transducer.
• By convection, red colored spots indicate blood flow moving
toward to the transducer, while blue colored spots represent
blood-red cells moving away from the probe.
• Additionally, the intensity of the colored pixels suggests the
velocity of blood flow ranging from dark to bright tonalities
for slower and faster velocities, respectively.
44.
45. 2- Spectral mode
• In the spectral mode, blood flow velocity variations are
represented as a graphic wave form called spectrum
(Figure 4).
• The spectrum provides maximum velocities values as
Peak systolic (PSV), End diastolic (EDV) and Time-
average maximum (TAMV) velocities.
• PSV is the maximum point along the length of the
spectrum, while EDV is the ending point of the cardiac
cycle.
• TAMV is the maximum velocity values average.
46.
47. 1- Color flow characteristics
1. Overall view of flow in a region
2. Limited flow information
3. Poor temporal resolution/flow dynamics (frame rate can
be low when scanning deep)
4. Color flow map (different color maps)
5. Direction information
6. Velocity information (high velocity and low velocity)
7. Turbulent flows
2- Spectral Doppler characteristics
1. Examines flow at one site
2. Detailed analysis of distribution of flow
3. Good temporal resolution - can examine flow waveform
4. Allows calculations of velocity and indices
48. 3- Power / energy / amplitude flow characteristics
1. Sensitive to low flows
2. No directional information in some modes
3. Very poor temporal resolution
4. Susceptible to noise
49. FACTORS AFFECTING THE COLOR FLOW IMAGE
The main factors include:
1. Power and gain
2. Frequency selection
3. Velocity scale / pulse repetition frequency
4. Region of interest
5. Focus
FACTORS AFFECTING THE SPECTRAL DOPPLER
1. Power and gain
2. Velocity scale / pulse repetition frequency
3. Gate size
50. Flow waveform shape: indices of measurement
• Many different indices have been used to describe the
shape of flow waveforms in a quantitative way (Figure
14).
• In general, they are a compromise between simplicity and
the amount of information obtained.
Commonly used indices are:
1. Systolic / diastolic ratio: (S/D);
2. Resistance index: (S-D) / D, also called Pourcelot's
index;
3. Pulsatility index: (S-D) / Vm.
53. • Ultrasonography is an imaging modality widely used
to evaluate venous diseases of the lower extremities.
• It is important to understand the normal venous
anatomy of the lower extremities, which has:
1. Deep vessels
2. Superficial vessels
3. Perforating vessels
in order to determine the pathophysiology of venous
disease.
54. • The venous system of the lower extremities is classified
into three groups according to the relationship to the
muscular fascia that surrounds the calf and leg muscles.
1- The Deep Veins
• it lie beneath the muscular fascia and drain the lower
extremity muscles
2- The Superficial Veins
• It lies above the muscular fascia and drain the cutaneous
microcirculation
3- The Perforating Veins
• It penetrate the muscular fascia and connect the
superficial and deep veins
55. 1. The deep vein (femoral vein, arrows),
2. Superficial vein (great saphenous vein, open arrows),
3. Perforating vein (femoral canal perforator, arrowheads)
of the thigh.
56. General Considerations for the US
Examination of Veins
• In contrast to arteries, veins have a weaker muscular layer
with less elastic walls, and therefore completely collapse
when the vein is compressed by the transducer (Fig. 2A).
• The compressibility of veins and pulsation of the arteries
can be a way to discriminate them in US.
• In addition, veins have valves that play an important role
in preventing reflux of the venous flow (Fig. 2B).
The normal flow
is directed from distal to proximal and from superficial to
deep. Usually, vascular flow is not seen on gray scale US,
and the venous lumen presents as anechoic.
57. • venous flow sometimes presents as echogenic, which can
reflect red blood cell aggregation and should not be confused
with thrombosis.
• This phenomenon is found especially frequently in conditions
of slow venous flow.
• Continuous observation without transducer movement or
identifying the compressibility of the lumen can be helpful to
differentiate this condition from true thrombosis.
• The selection of a transducer for evaluating the lower
extremity veins is a trade-off between resolution and beam
penetration.
• Generally, a frequency of 5 MHz or greater is recommended,
but sometimes a lower-frequency transducer is required for
deep penetration views in obese, edematous, or muscular
patients.
58. 1- Deep Veins
Anatomy
• The major deep veins of the lower extremities follow the
course of the corresponding arteries.
• The deep venous system of the calf (leg muscles) includes
1. The anterior tibial
2. Posterior tibial
3. Peroneal veins.
• In the calf, these deep veins present as pairs on both sides of
the artery.
The posterior tibial vein
• It lies behind the tibia and joins the popliteal vein at the
posterior knee.
• It Receives blood from the medial and lateral plantar vein and
drains the posterior compartment of the leg and plantar surface
of the foot.
59. The anterior tibial vein
• It runs along the anterior compartment of the leg just above the
interosseous membrane between the tibia and the fibula, and joins the
posterior tibial vein to form the tibioperoneal trunk and popliteal
vein.
The peroneal vein
• Runs along the posteromedial aspect of the fibula and joins the
posterior tibial vein.
The popliteal vein
• It is formed by the junction of the anterior and posterior tibial veins at
the lower aspect of the posterior knee.
• It ascends along the posterior aspect of the knee and the distal aspect
of the anteromedial thigh.
• It is located medial to the artery in the lower knee, superficial to the
artery at the posterior knee, and to the lateral side above the knee.
• The term superficial femoral vein is no longer recommended,
because this vein is not a superficial vein, but rather a deep vein
60.
61.
62. Technique
Indications
1. Blockages to blood flow (such as clots)
2. Narrowing of vessels
3. Tumors and congenital vascular malformations
4. Reduced or absent blood flow to various organs, such as
the testes or ovary
5. Increased blood flow, which may be a sign of infection
63. Technique for deep veins
Patient Position
1. The patient Lie in a supine or semi-Fowler position.
2. The reverse Trendelenburg position, if possible, is also
recommended, as it facilitates venous filling in the lower
extremities and makes the veins dilate.
3. External rotation of the hip and slight flexion of the knee helps to
decrease muscle tension and is good both for exposing the deep
veins in the medial thigh, posterior knee, and calf, and for the
compression maneuver
Technique
1. Veins drain blood in the distal-to-proximal direction to the right
side of the heart.
2. It is convenient to examine the deep veins from a proximal to distal
direction because the proximal veins are larger in diameter and easy
to detect.
3. At the level of the inguinal ligament, in the transverse view, the
examiner can see the common femoral vein on the medial side of
the artery.
64. 4. Information about the flow pattern of the vein can be
assessed in the longitudinal view with Doppler US.
5. Following the common femoral vein, it bifurcates into
the deep femoral vein and the femoral vein (Fig. 4C).
6. In the more distal part of the medial thigh, only the
femoral vein is visible (Fig. 4D).
7. When the transducer approaches the popliteal fossa of
the posterior knee, the popliteal vein is visible.
8. The popliteal vein is superficial to the popliteal artery at
the posterior knee (Fig. 4E).
65. 9. Duplicated femoral veins or popliteal veins can be seen.
10. Because a duplicated venous segment may result in
false-negative results, both lumens should be carefully
examined (Supplementary Fig. 1)
11. Manual vein compression is recommended every 3-4
cm.
12. When tracing the popliteal vein downward, two
posteriorly branching veins are found in the calf from
the posteromedial approach.
13. The vein along the tibia is the posterior tibial vein, and
the vein along the posteromedial aspect of the fibula is
the peroneal vein.
66. 14. The cortical shadow of the tibia and fibula can be used as a
bony landmark.
15. The paired veins are present on both sides of the artery (Fig.
4F).
16. After stretching the patient’s leg, the anterior tibial vein can
be visualized from an anterolateral approach (Fig. 5).
17. Just above the echogenic interosseous membrane between the
tibia and the fibula, the anterior tibial artery and vein can be
found.
18. If the posterior tibial vein cannot be traced in the proximal to
distal direction, it is helpful to trace the vein upward from the
posterior to the medial malleolus, where this vein is located
more superficially.
19. If the popliteal and calf veins are not visualized well in the
supine-based position, the prone or decubitus position
67. • Demonstration of side-by-side transverse ultrasonography
(noncompression and compression views)
A. Patient position and schematic
representation of the transducer
locations are shown here
68. B. The common femoral vein is seen at the level of the inguinal
ligament on the medial side of the common femoral artery, which is
round and pulsatile. The vein collapses upon compression (arrows).
69. C. Upon following the common femoral vein downward, it
bifurcates into the deep femoral vein (open arrows) and the
femoral vein (arrows).
70. D. Only the femoral vein (arrows) is visible in the more distal part of
the medial thigh.
E. When the transducer approaches the popliteal fossa in the posterior knee, the
popliteal vein (arrows) becomes visible.
71. F. Tracing the popliteal vein downward from the posteromedial
approach shows two posteriorly branching veins in the calf.
The vein along the tibia (T) is the posterior tibial vein (arrows) and the
vein along the fibula (F) is the peroneal vein (open arrows).
The veins are present on both sides of the artery.
72. Ultrasonographic findings of the anterior tibial
vein.
A. Stretching of the patient’s leg permits
approach to the anterior tibial vein from
the anterior side.
73. B. Above the interosseous membrane (arrowheads) between the tibia (T)
and the fibula (F), the anterior tibial vein (arrows) and artery (open arrows)
are visible.
The sonic window is demonstrated through computed tomography
venography.
74. 2- Superficial Veins
Anatomy
• The two major superficial veins of the lower extremities
are the great saphenous vein (GSV) and small saphenous
vein (SSV).
• The GSV begins in the medial marginal vein of the
dorsum of the foot, ascends anteriorly to the medial
malleolus, and passes posteromedially to the knee.
• The vein then ascends medially in the thigh to perforate
the muscular fascia and join the common femoral vein at
the sapheno femoral junction, a few centimeters distal to
the inguinal ligament.
75. • The SSV arises from the dorsal pedal arch and ascends
posterolaterally from behind the lateral malleolus.
• It ascends along the middle of the calf and ends in the
popliteal vein in the posterior knee.
• The popliteal vein before it penetrates the muscular
fascia, it may branch out a cranial extension that goes
upward to join the GSV through the posterior thigh
circumflex vein (the vein of Giacomini)
76. Technique
Patient Position
1. The superficial veins should be evaluated with the patient in
the erect position, as the supine position may underestimate
or miss the reflux of the venous flow
2. The reverse Trendelenburg position can be used if an erect
position is impossible.
3. The examined leg should be in a non-weightbearing position.
Technique
1. The saphenofemoral junction is visible on the anteromedial
surface of the common femoral vein in the transverse view.
2. A longitudinal view of the saphenofemoral junction (Fig. 7B)
is useful for assessing reflux of the terminal valve with the
help of Doppler US (Supplementary Fig. 2).
77. 3. Normally, the terminal valve at the saphenofemoral
junction prevents backward flow into the GSV.
4. After a provocation test, such as the Valsalva maneuver,
retrograde flow in the proximal GSV persisting for more
than 0.5 seconds is defined as pathologic reflux.
5. There is an echogenic fascia surrounding the GSV that
is bordered deeply by the muscular fascia and
superficially by the saphenous fascia.
6. This saphenous compartment is readily visualized on
US and is described as having an “Egyptian eye”
appearance (Fig. 7C).
78. 7. The saphenous compartment is also visible at the knee
level, above the tibia and medial gastrocnemius (Fig.
7D). Unfortunately, however, there are many variations
in the relationship of the fascial compartment to the
GSV.
8. Sometimes there is a large tributary outside of the
saphenous compartment, while the distal GSV is
hypoplastic or even absent.
9. The SSV is visible at the middle of the gastrocnemius
belly in the fascial trunk (Fig. 8).
10. In tracing the SSV upward, it enters into the popliteal
vein.
79. 11. The longitudinal view of the saphenopopliteal
junction, like the saphenofemoral junction of
the GSV, is useful for assessing insufficiency of
the SSV.
12. In the saphenopopliteal junction, calf squeezing
augments the venous flow at first, followed by
retrograde flow. As described above, however,
there are many anatomical variations in this
region, and the saphenopopliteal junction may
be absent or rudimentary.
80. Ultrasonographic findings of the great
saphenous vein (GSV).
A. Patient position (standing) and
schematic representation of the
transducer locations are shown
here
81. B. Longitudinal view of the saphenofemoral junction and the corresponding
sonic window in computed tomography venography based on transducer
location are demonstrated.
In most cases, a terminal valve (arrows) near the saphenofemoral junction
prevents backward flow into the great saphenous vein. CFV, common
femoral vein.
82. C. Examination of the GSV shows the echogenic fascia surrounding the GSV,
which is bordered deeply by the muscular fascia (arrows) and superficially by
the saphenous fascia (arrowheads). This saphenous
compartment is readily visualized on ultrasonography and is described as
having an “Egyptian eye” appearance.
D. Transverse ultrasonography examination at the level of the knee shows the
saphenous compartment (arrowheads) overlying the tibia (T) and the muscle
fascia of the medial gastrocnemius (G).
83. 3- Perforating Veins
Anatomy
• The perforating veins connect the deep veins with the
superficial veins and direct the flow from the
superficial to the deep system.
• There are numerous perforators in the leg.
• perforators are named after their locations.
• Major groups classify perforators according to their
longitudinal location as ankle, leg, knee, and thigh
perforators.
• Subgroups indicate side (i.e., anterior, posterior,
medial, and lateral perforators).
• Thus, the complete name of the perforator is a
combination of the level and side (i.e., the medial leg
perforator or the anterior thigh perforator).
84. A. Patient position and schematic
representation of the transducer locations
are shown here.
Ultrasonographic findings of the
small saphenous vein (SSV).
85. B. In the transverse view of the posterior calf, the SSV is seen
in the middle of the gastrocnemius (G) belly in the fascial
trunk (arrowheads).
86. C. Longitudinal ultrasound view and the corresponding sonic window in computed
tomography venography based on transducer location are demonstrated.
The SSV joins the popliteal vein (Pop V) through the saphenopopliteal junction.
However, many variations are noted in this region, and the saphenopopliteal
junction can be absent or hypoplastic.
87. Technique
• The perforating veins are not clearly visible on US.
• However, when there is a flow disturbance in the deep or
superficial veins or in the case of perforator insufficiency,
the perforating veins can be dilated and are readily visible
as a penetrating structure through the muscular fascia
(Fig. 10A).
• In the case of varicose veins caused by perforating vein
insufficiency, it is important to localize the refluxing
point in order to correct it.
88. • The medial thigh and leg perforators are clinically the
most important.
The medial leg perforator includes:
1. The posterior tibial perforator
2. The paratibial perforator.
The posterior tibial perforator,
• known as the Cockett perforator, connects the posterior
accessory GSV with the posterior tibial vein in the distal
calf.
The paratibial perforator
• connects the GSV or its tributaries with the posterior
tibial vein. The proximal paratibial perforator was
previously called the Boyd perforator.
89. In the thigh
• the perforating vein of the femoral canal,
previously called the Hunterian (proximal thigh)
or Dodd (distal thigh) perforator, connects the
GSV with the femoral vein or the proximal
popliteal vein.
• Insufficiency of these perforators may cause
medial thigh and calf varicosities, even in the
absence of saphenofemoral reflux (Fig. 10B).
92. Indications for pelvic sonography
Indications for pelvic sonography include but are not limited
to:
1. Evaluation of pelvic pain
2. Evaluation of pelvic masses
3. Evaluation of endocrine abnormalities, including polycystic
ovaries
4. Evaluation of dysmenorrhea (painful menses)
5. Evaluation of amenorrhea
6. Evaluation of abnormal bleeding
7. Evaluation of delayed menses
8. Follow-up of a previously detected abnormality
9. Evaluation, monitoring, and/or treatment of infertility patients
10. Evaluation in the presence of a limited clinical examination
of the pelvis
93. Methods of Examination :
1- Trans abdominal examination
• Convex 3 MHz probe
• Full Bladder ( ? …. )
• Sagittal and transverse scan
2- Trans Vaginal examination TV
• Endo cavitary 5-7 MHz probe
• Empty Bladder ( Organs in focus & More comfortable to
patient )
• Orientation : Sagittal & Coronal ( rotation 90
• degree counter clockwise )
94. UTERUS
It is pear shaped organ formed of ;
1. Body
2. Fundus is the wide superior portion of the body of the
uterus
3. Cervix ; relatively narrowed segment open distally into
the vagina ( External os ) and communicate with uterine
cavity ( Internal os ) at the level of UB angle
95. • Transvaginal ultrasound of the uterus. Note the
uterine fundus (F), uterine body—upper 2/3 of the
uterus (B), isthmus— junction between the body of
the uterus and cervix (I) and cervix (C) lower 1/3 of
the uterus
96. In examining the uterus, the following should be
evaluated:
(1) the uterine size, shape, and orientation;
(2) the endometrium;
(3) the myometrium;
(4) the cervix.
97. Uterine Layer :
1- The Myometrium
which are anterior and posterior muscular layer ;
2- The Endometrium
is the mucosal lining of the uterine cavity ( two layer ) The
thickness and echogensity are hormonal dependent
3-Serosa
The outer surface cover with serosa (Peritoneal cover )
98. Uterine Positions
AVF
• Anteverted AnteflexidVersion ; relation of cervix with
vagina
• Flexion ; relation of the body with the cervix
• The fundus directed anterior
RVF
• Retrverted Retroflexed
• The uterus rotate posterior
• The fundus tilt posterior ( normal variant in 20% of
females )
100. • Transabdominal ultrasound of the uterus. Note the
urinary bladder, uterus, abdominal wall muscles and
Pouch of Douglas
101. • Transabdominal ultrasound of the ovary. Identify
urinary bladder, abdominal wall, ovary, uterus and
broad ligament/fallopian tube
102. Uterine Size
Infantile 2-3 cm length
Nulliparous maximum 8 cm
length
Multiparous 1-2 cm increase in
size /preg.
Postmenopausal atrophic , calcified
atrophic
endometrium
not exceed 8 mm
103. Endometrial Thickness (Hormonal Dependent)
1- Menstrual Phase :
• Shaded Endometrium with residual Thin echogenic line’
2- Early Prolifrative
• Progesteron Dependant 6-8 mm thickness ( Both layer)
3- Late Proliferative :
• Pre ovulatory phase More thick 7-12 mmHypoechoic( Edema )
4- Secretory Phase :
• Ostrogen Dependant Hyper echoic ( Increase Mucus Glands )
• Thickness 8-14 mm
105. OVARIES
• Oval shaped intra peritoneal
organs
• Size 2-3 cm
• Present on each side of the
uterus showed some of
follicles ( the size and
number are hormonal
dependent )
• Ovarian Arteries are branches
of the aorta at level just distal
to renal arteries
106. dimensional evaluation of the ovary
• The best, most careful dimensional evaluation of the
ovary is by volume calculation, by applying the ellipsoid
formula:
length × width × thickness / 2.
• The ovarian volume is relatively stable until 5 years of
age, when progressive proportional growth is seen. In
adult women, the ovary generally measures 3 × 2 × 1 cm.
• The ovarian volume varies from 2–3 ml in children to 4–
5 ml in adolescents and 6–8 ml in adults.
• At menopause, the mean volume is reduced to about
3.7 ml, and the ovaries are difcult to see, even on
transvaginal examination.
107. Folliculometery
• It mean assessment of follicular
maturation and rupture ( Ovulation )
• Repeated examinations well done
starting from 8thday of cycle
• Normal follicular maturation 18-24 mm
at 12th-16th day of menstruation with
endometrium show late proliferative
phase (8-12 mm )
Sign of ovulation ;
1. Disappearance of follicle ,
2. Has outline
3. Size regress with minimal fluid
delineate the ovary or pouch of
Douglas
108. US Technique
Trans Abdominal pelvic
US
Trans Vaginal
Pelvic US
Pt position supine Supine in
lithotomy position
Probe used convex 3 MHZ Endocavitary
convex 5-7 MHZ
Field of view Wide deep field of view Limited field of
view
Preparation Full bladder required Empty Bladder
Resolution &
Details
ovaries , endometrium
has low resolution
Greater resolution
and details
Part
evaluation
Examined RVF uterus
and obese patient is
difficult
Better evaluation
109. Us uterus evaluation
• The overall uterine length is evaluated in a sagittal view from the
fundus to the cervix (to the external os, if it can be identified).
• The depth of the uterus (anteroposterior dimension) is measured in
the same sagittal view from its anterior to posterior walls,
perpendicular to the length.
• The maximum width is measured in the transverse or coronal view.
• If volume measurements of the uterine corpus are performed, the
cervical component should be excluded from the uterine length
measurement.
• Abnormalities of the uterus should be documented.
• The myometrium and cervix should be evaluated for contour
changes, echogenicity, masses, and cysts.
• Masses that may require follow up or intervention should be
measured in at least 2 dimensions, acknowledging that it is not
usually necessary to measure all uterine fibroids.
• The size and location of clinically relevant fibroids should be
documented.
110. • The endometrium should be analyzed for thickness, focal
abnormalities, echogenicity, and the presence of fluid or
masses in the cavity.
• The thickest part of the endometrium should be measured
perpendicular to its longitudinal plane in the
anteroposterior diameter from echogenic to echogenic
border (Figure 1).
• The adjacent hypoechoic myometrium and fluid in the
cavity should be excluded (Figure 2).
• Assessment of the endometrium should allow for
variations expected with phases of the menstrual cycle
and with hormonal supplementation.5–7 It should be
reported if the endometrium is not adequately seen in its
entirety or is poorly defined.
111.
112.
113. Adnexa, Including Ovaries and Fallopian Tubes
• When evaluating the adnexa, an attempt should be made
to identify the ovaries first, since they can serve as a
major point of reference for assessing the presence of
adnexal pathology.
• The ovarian size may be determined by measuring the
ovary in 3 dimensions (width, length, and depth) on
views obtained in 2 orthogonal planes.
• The ovaries may not be identifiable in some patients, this
occurs most frequently before puberty, after menopause,
or in the presence of a large leiomyomatous uterus.
• The adnexal region should be surveyed for abnormalities,
particularly masses and dilated tubular structures.
114. Uterine disorders
I- Congenital anomalies
Precautions for uterine congenital anomalies
evaluation
1. Combination of both TV US and HSG are required for
assessment of anomalies
2. Anomalies responsible for primary infertility or abortion
detected in early pregnancy
3. 3D us ( Multi planner capability ) and pelvic MRI may be
required for assessment of uterine anomalies
115. 1- Uterine Aplasia ; Absent
2- Uterine Hypoplasia ; Infantile uterus ( 2-3 cm )
3- The arcuate uterus
• the uterine fundus displays a concave contour towards
the uterine cavity.
• the fundus dips into the cavity and may form a small
septation.
116. 4- Bicornuate uterus
• A bicornuate uterus or bicornate uterus, commonly referred
to as a "heart-shaped" uterus,
5- Uterine septum
• A uterine septum is a form of a congenital malformation where
the uterine cavity is partitioned by a longitudinal septum
117. 6- Unicornuate uterus
• the uterus is formed from one only
of the paired Müllerian ducts
while the other Müllerian duct
does not develop or only in a
rudimentary fashion.
7- Uterus didelphys
• the uterus is present as a paired organ as
the embryogenetic fusion of the mullerian
ducts failed to occur.
• As a result there is a double uterus with
two separate cervices, and often a double
vagina as well. Each uterus has a single
horn linked to the ipsilateral fallopian tube
that faces its ovary.
118. II – Myometrium disorders
Myoma ( Fibroid )
The Most common Benign tumor of uterus
US Findings :
• Texture : Heterogenous or Hypo echoic
• Outline :Well Defined
• Findings may be associated : Calcific foci & Calcific
outlines (Old age )
• Cystic Spaces ( cystic break Down )
119. Types of Myomas According to
localization :
1-Intra Mural
( Interstitial Myoma )
2- Sub Mucosal Myoma
Projected into the Cavity
120. 3- Sub Serosal Myoma
projected externally from the
peritoneal surface
121. II Endometrial Abnormality
Endometrial Hyperplasia
( Hormonal Dysfunction )
Endometrial Carcinoma
( Cancer Body )
Post Menopausal Post Menopausal
Symptoms: Bleeding Bleeding
Thickened hyper echoic
Endometrium more than 8 mm
Thickened hyper echoic
endometrium more than 8 mm or
may be heterogenous, polypoidal ,
poorly defined margin
122. III- Intra Uterine ( Contraceptive ) Devices
IUD
Normal IUD location Abnormal IUD Location
• Intra uterine echogenic line with
fundal
• loop distance not exceed 20 mm
1- Intra Uterine in low position
2- Perforation : apart of the loop
embedded in myometrium
3- Penetration : empty uterine
cavity ( Missed Loop ) Plain X-ray
required to identified intra
abdominal location
of loop or confirm missed loop
123. Ovarian Lesions
1-Follicle
2- Follicular cyst ;
Follicle failed to rupture increase in
size < 25 mm
3- Corpus Luteam
Cyst ;Unilateral cyst unilocular
thin wall ,the fertilized follicle
continue as corpus luteam of
pregnancy ( Max. size at 10 WKs
and resolved at 16 WKs )
124. 4-Hemorhagic Cyst ;
bleeding inside functional cyst become
hyper echoic , simulate solid mass ( But
casting posterior enhancement)
5- Ovarian hyper stimulation syndrome
iatrogenic on top of follicular induction .
The ovaries enlarged < 10 cm studded with
large follicles associated with ascites and
pleural effusion
6-Chocolate Ovarian Cyst :
associated with endometriosis . Repeated
menstrual bleeding of ectopic endometrium
forming turbid cyst simulate hemorrhagic
cyst
125. Polycystic Ovarian Disease ( PCO )
Bilateral enlarged ovaries with peripheral
multiple small follicles 5-8 mm
Hormonal disease ( increased androgen
and LH ) Lead to chronic anovulatory
cycle ( associated with male hair
distribution )
Dermoid Cyst - Cystic Teratoma –
( Embryonic Tumor )
Mixture of the 3 germ Layers
( ecto-meso - endoderm )
US show mixed cyst contain teeth , bone,
hairs- Multiple interfaces – fat-fluid
levels
126. Ovarian Tumors
1-Benign
e.g. Papillary Cystadenoma
2- Malignant
e.g. Papillary Cystadenocarcinoma
• Large cyst ( may reach • 30 cm )
• Thin septa
• Soft tissue papillary projections
• Partially defined out line Thick
wall
• thick irregular septa ,
• Irregular soft tissue papillary
projections
• may surrounded with pelvic
collection
128. Indications
Obstetrical ultrasound is a useful clinical test to:
1. Establish the presence of a living embryo/fetus
2. Estimate the age of the pregnancy
3. Diagnose congenital abnormalities of the fetus
4. Evaluate the position of the fetus
5. Evaluate the position of the placenta
6. Determine if there are multiple pregnancies
7. Determine the amount of amniotic fluid around the baby
8. Check for opening or shortening of the cervix
9. Assess fetal growth
10. Assess fetal well-being
129. General technique
PROBE MOVEMENTS
A- The abdominal probe
• There are four possible movements of this probe
1- Sliding
• By holding the probe longitudinally and sliding it from
side to side across the abdomen or slid up and down the
woman’s abdomen from the symphysis pubis tothe
umbilicus or vice versa
• a maneuver technique is useful for keeping a structure
that is being examined in the center of the screen.
130.
131. 2- Rotating
• This term describes rotation of the probe about a fixed
point. Its main use is that it allows a longitudinal section
to be obtained from a transverse section of an organ (or
vice versa) while keeping the organ in view.
132. 3- Angling
• This describes an alteration of the angle of the complete
probe surface relative to the woman’s skin surface .
• Its main use is for obtaining correct sections from slightly
oblique views.
133. 4- Dipping
• This describes pushing one end of the transducer into the
woman’s abdomen.
• It can be uncomfortable, so should be done as gently as
possible.
• Its main use is to bring structures of interest
• to lie at right angles to the sound beam
134. B- The vaginal probe
• Four movements are possible with the transvaginal probe,
but they are limited by the available space within the
vagina.
• All movements of transvaginal probes should be carried
out slowly and gently.
1- Sliding
This describes the movement of the probe along the length
of the vagina
2- Rotating
This describes a circular movement of the handle
of the probe
135. 3- Rocking
• This describes movement of the handle of the probe in an
anteroposterior plane such that the tip of the probe moves
in the opposite direction.
• This movement is used to image the true longitudinal
section of the uterus when its position is not axial. It is
also used to obtain true transverse sections of the uterus
when the uterus is anteverted.
4- Panning
• This is a photographic term that is borrowed to describe
movement of the handle of the probe in a horizontal plane
such that the tip of the probe moves in an opposite
direction.
137. CLASSIFICATION OF FETAL ULTRASOUND
EXAMINATIONS
A. Standard First Trimester Ultrasound Examination
A standard obstetrical ultrasound examination in the first
trimester includes evaluation of:
1. The presence of gestational sac(s)
2. Size of gestational sac(s)
3. Location of gestational sac(s)
4. Number of gestational sac(s).
138. When an embryo/fetus is detected
• It should be measured,
• The cardiac activity should be recorded by 2-D
video clip or M-mode.
• The routine use of pulsed Doppler ultrasound to
either document or “listen” to embryonic/fetal
cardiac activity is discouraged .
• The uterus, cervix, adnexa, and cul-de-sac region
should be examined.
139. B. Standard Second or Third Trimester Ultrasound
Examination
An obstetrical ultrasound in the second or third trimester
includes an evaluation of:
1. Fetal number,
2. Cardiac activity,
3. Presentation, amniotic fluid volume,
4. Placental position,
5. Fetal biometry,
6. Anatomic survey.
7. The maternal cervix and adnexa should be examined.
140. The first aim of any obstetric ultrasound examination is to
find the uterus.
1. The uterus lies centrally within the pelvis, posterior to the
bladder and cephalad to the vagina (Fig. 3.1).
2. It is usually anteverted and rotated slightly to the right
(dextrorotated).
141. FINDING THE UTERUS
Scanning the early pregnant pelvis can be performed using
transvaginal or abdominal probes
The transvaginal probe with frequencies of 7.0–12.0 MHz is
better in detecting early pregnancy because:
• The probe can be placed in close proximity to the organ of
interest, namely the uterus.
The gestation at which an intrauterine pregnancy can be
confirmed is dependent on
1. The position of the uterus
2. The presence of fibroids.
A sharply retroverted uterus or the presence of fibroids might
delay the ability to confirm a pregnancy for a further 7–10 days.
142. A- Transvaginal Method
Patient Preparation
1. Empty bladder is a prerequisite.
Send the woman to the toilet before beginning a transvaginal
examination because even a small amount of urine in the bladder
can displace the organs of interest out of the field of view.
2. Apply a small amount of gel to the transducer tip and cover
the tip and shaft of the probe with a (non-spermicidal)
condom.
3. Apply a small amount of gel, or KY jelly, to the covered
probe to allow easier insertion into the vagina.
143. Technique
1.Hold the prepared probe with the mark or guide positioned to
produce a longitudinal view of the pelvis.
2.This usually means having the mark uppermost.
3.Insert the probe gently into the vagina.
4.The uterus will usually be visualized by panning the tip of the
probe slightly towards the woman’s right shoulder (to
compensate for dextrorotation) and then rocking the handle
posteriorly towards the perineum.
5.If you cannot find the uterus you might need to gently slide the
probe further into the vagina.
144. 6. By gently panning the probe to left and right, the
optimal longitudinal view of the uterine
7. cavity, endometrium and ‘cavity line’ will be obtained
(Fig. 3.2).
8. Do not rotate the probe simultaneously with panning
because this will alter your orientation.
9. To ensure that the view is truly longitudinal the entire
length of the cavity line should be visualized.
10. The ultrasound appearance of the endometrium will
vary depending on the stage of the menstrual cycle.
145.
146. Problems of transvaginal method
1. It is inappropriate in girls or women who have never
had sexual intercourse.
2. There is no evidence that gentle transvaginal scanning is
at all harmful but in certain situations the woman or her
doctor might want you to carry out an abdominal scan.
3. Poor positioning of the woman can reduce the
maneuverability of the probe within the vagina,
particularly rocking or panning movements. Bringing
the woman’s bottom right to the end of the couch will
improve access for rocking the probe.
4. Large and/or multiple fibroids will affect the quality of
transvaginal images
147. B- Abdominal Method
Patient Preparation
1- The woman must have a full bladder. This has three
effects:
a) It pushes the uterus out of the pelvis, thus removing it
from the acoustic shadow caused by the symphysis
pubis;
b) It provides an acoustic window through which the
pelvic organs can be visualized
c) It displaces the bowel superiorly, so preventing gas from
the bowel scattering the ultrasound beam.
148. Technique
2. To examine the pelvis adequately, a probe with a small
area of contact is needed. This is most commonly of the
sector type, but phased array, annular array and small
curvilinear probes are also appropriate.
3. Before you begin check that you are holding the probe
and/or that the left–right control is activated such that
the sector image on the monitor will display the
maternal bladder on the right of the screen and the
uterine fundus on the left.
4. Place the probe on the abdomen in the midline,
immediately superior to the symphysis pubis to obtain a
longitudinal section of the pelvis.
149. 5. The bladder should be seen on the right of the screen.
6. The vagina is usually immediately visualized as three bright
parallel lines posterior to the bladder
7. If only the lower part of the uterus is seen, rotate the probe
slightly towards the right side of the woman, to compensate
for the dextrorotation of the uterus.
8. The section should clearly demonstrate the uterine fundus.
9. If the uterine fundus cannot be adequately seen because the
bladder is insufficiently filled, the examination should be
postponed until this situation is rectified.
10. The cervical canal can be difficult to define in non-pregnant
women because of the angle at which it lies relative to the
sound beam
150. 11. The position of the internal os can be gauged as it lies
directly beneath the point at which the posterior wall of the
bladder appears to change direction (see Fig. 3.1).
12. The external os is not seen trans abdominally
13. Cross-sectional views of the uterus are obtained by rotating
the probe through 90° while keeping the cavity line in view.
14. Sliding the probe up and down the abdomen will produce
transverse sections of the uterus from fundus to cervix.
15. Oblique sections of the uterus, rather than transverse
sections, will be obtained if the angle of the probe on the
woman’s abdomen is not at 90° to the longitudinal axis of the
uterus or is altered during the examination.
Problems Abdominal method
● The fundus of the uterus will not be visualized unless the
bladder is filled sufficiently to cover it.
151.
152. Period of pregnancy
Clinically the period of pregnancy divided into three
stages:
• 1st trimester ( 1st 14 WKs )
• 2nd trimester ( 14-28 WKs )
• 3rd trimester ( 28- 40 WKs )
GESTATIONAL AGE ESTIMATION
1. Dating Based on Menstrual History
2. Dating Based on Ultrasound Findings
3. Dating Based on Clinical Examination
153. Dating Based on Menstrual History
Calculating the length of pregnancy
The most accurate way to calculate the length of pregnancy is by:
knowing the date of conception.
Delivery would then be expected to occur 38:40 weeks (266 days) later.
However, as most women are unaware of the date of conception,
the first day of the last menstrual period (LMP) is used to calculate the expected
date of delivery (EDD).
This is done by applying Naegele’s formula to the LMP as follows:
1. add 7 to the days
2. subtract 3 from the months
3. add 1 to the years.
For example, if the LMP is 13.4.04 then the EDD
is (13 + 7). (4 − 3). (04 + 1), that is 20.1.05.
154. GESTATIONAL AGE ESTIMATION
Dating Based on Ultrasound Findings
Transabdominal And Transvaginal Ultrasonography
1. Transvaginal route in early/late pregnancy: makes use of
a higher frequency( 5-7.5MHz)
2. Transabdominal route after 12 weeks gestation
3. The quality and interpretation of the image is subject to
the skill of the operator.
155. • Transvaginal ultrasound is typically used to evaluate early
first trimester pregnancy structures, such as the
gestational sac yolk sac embryo.
• Ultrasound biometric measurements determine
gestational age based on the assumption that the size of
the embryo or fetus is consistent with its age.
• Biological variation in size is less during the first
trimester than in the third trimester
• Ultrasound estimation of gestational age in the first
trimester is therefore more accurate than later in
pregnancy.
156. • First Trimester – Commonly performed at 9-12 weeks
• 2nd Commonly performed at 18-20 weeks
• 3rd Trimester Commonly performed at 36 weeks
First Trimester
The determination of gestational age in the first trimester
uses
1. The mean gestational sac diameter (MSD) and/or
2. The crown– rump length (CRL)
• The MSD is a commonly used, standardized, way to
estimate gestational age during early pregnancy.
• It is less reliable when the MSD exceeds 14 mm or when
the embryo can be identified.
• The growth of the MSD is approximately 1 mm per day.
• However CRL has lower inter-observer variability than
MSD, and may thus be better for dating a pregnancy
157. Yolk Sac
• When the yolk sac appears in the gestational sac it
provides confirmation of an intrauterine pregnancy and
may be initially visible as early as the start of the 5th
week or as late as the 6th week.
• It grows to a maximal size of 6 mm by 10 weeks and
gradually migrates to the periphery of the chorionic
cavity.
• At the end of the first trimester it becomes undetectable
158.
159. Gestational Sac ( GS )
The gestational sac is the fluid-filled structure that
surrounds the embryo
• Start to be visualized 4-5 WKs
• Healthy sac ; seen intact smooth regular out line, rounded
or oval shaped , Implanted in the uterine cavity mostly at
the fundus
• Yolk sac The yolk sac appears as a circular transonic mass
within the gestation sac and can first be identified
transvaginally at about 35 days, when it measures 3–4 mm
in diameter ( not exceed 6 mm at 10 weeks)
160.
161.
162.
163.
164. Uses of gestation sac measurements
● Confirmation of an intrauterine pregnancy.
● Calculation of gestational age before the embryo is visible.
● Diagnosis of miscarriage.
ON-GOING PREGNANCY
The pregnancy can only be said to be ongoing
• when cardiac pulsations from the embryo can be
demonstrated within the gestation sac
167. MEASUREMENT OF CROWN–RUMP
LENGTH (CRL)
• (CRL) is the measurement of the length of human embryos and
fetuses from the top of the head (crown) to the bottom of the
buttocks (rump).
• It is typically determined from ultrasound imagery and can be
used to estimate gestational age
• As soon as the embryo can be seen the gestational age can be
estimated by measuring the crown–rump length.
• We use it to study fetal growth without the uncertainties caused
by the irregularities of the menstrual cycle.
• The biological variability of the crown–rump length is small
and growth is very rapid.
There are still a number of factors that can affect the size of
an early embryo, such as
1. Measurement errors,
2. Differences in growth rates between individuals,
3. Fetal sex and maternal conditions such as diabetes mellitus.
168. • A correctly performed measurement of CRL is the most
accurate means of estimating the gestational age.
• An optimal CRL image, accurately measured, is thus more
accurate than the biparietal diameter in dating a
pregnancy.
• However, accurate crown–rump measurements can be the most
difficult measurements to obtain during pregnancy.
• The ability correctly to establish gestational age by thismethod
depends solely on:
1. The operator obtaining a true, un flexed, longitudinal section
of the embryo or fetus, with the end-points of the crown and
rump clearly defined,
2. placing the callipers correctly on these defined end-points.
• Appreciation of the optimal CRL and correct calliper
placement only come with experience.
169. CRL Measuring Technique
1. First, find a longitudinal section of the uterus and
gestation sac.
2. Slide (if scanning abdominally) or pan (if scanning
transvaginally) the probe slowly to each side until
pulsations from the fetal heart can be seen.
3. Slowly rotate the probe, keeping these pulsations in
view, until the long axis of the fetus is obtained.Freeze
this image.
4. Measurements are taken from the top of the head
(crown) to the end of the trunk (rump) using the
onscreen calipers (Fig. 3.18
170.
171. • The very early embryo is un flexed.
• There are two main reasons why CRL measurements taken
between 5 and 7 weeks are inaccurate:
1. The full length of the embryo has not been obtained – this will
produce an underestimated CRL (Fig. 3.19A).
2. The end-points of the embryo have not been clearly identified
as separate from the closely
• adjacent yolk sac or the wall of the gestation sac and one or
both have been included in the measurement – this will
produce an overestimated CRL (Fig. 3.19B).
• The CRL should be measured from three different images and
the measurements should agree to within 3 mm in the embryo
and 5 mm in the fetus.
• Once the fetal spine can be easily identified, i.e. from about 9
weeks, this should be used as a guide in assessing true fetal
length.
• The aim is to examine the fetus with the full length of its spine
positioned directly anteriorly or posteriorly, thereby enabling
you to assess any degree of flexion.
172. Problems
• Any degree of flexion of the fetal spine will produce an
underestimate of the CRL when linear calipers are used (Fig. 3.19C).
• Should the fetal spine be lateral, the degree of flexion can be difficult
to estimate.
• When scanning transabdominally, alteration of the angle of the probe
relative to the maternal abdomen might bring the spine into a more
anterior, or posterior, position, thus making accurate measurement
possible.
When the fetus remains obstinately curled, you have four choices:
1. Sit and wait.
2. Measure the flexed length using onscreen nonlinear measuring
facilities (Fig. 3.20A).
3. Use the linear calipers to measure the parts of the fetal length that
are in straight sections, and then add them together (Fig. 3.20B).
4. Underestimate the CRL by using the linearcalipers along the flexed
length (see Fig. 3.19C).
• This is not to be recommended under anycircumstances.
173.
174.
175.
176.
177. Fetal Age Estimation in 2nd & 3rd Trimester
• Bi-parietal diameter (BPD) and head circumference (HC)
measurements
178. BPD:
• Greatest accuracy between 12-28 weeks
(better>14 wks.)
• The plane for measurement of head
circumference (HC) and bi-parietal
diameter (BPD)must include:
• Cavum septum pellucidum
• Thalamus
• Choroid plexus in the atrium of the lateral
ventricles.
• Measure outer table of the proximal skull
to the inner table of the distal
HC:
• Measure the longest AP length • (BPD +
OFD) X 1.62
179. Abdominal Circumference (AC)
• The abdominal circumference is taken with a transverse
image to include the stomach, portal vein and the spine in
a true transverse plane.
• The ribs may or may not be seen but must be symmetrical
if included.
• It should be a circle at 18-20 weeks and no compression
by external forces.
• It is best taken with the baby supine or lateral because if
the baby is prone then the rib shadows make it difficult to
check the correct level.
• The measurement must be taken around the waist on the
edge of the skin layer
180.
181. Composite Versus Single Biometry
Measurement
• Using multiple parameters is superior to using a
single & second trimester parameter.
• As more parameters are used, accuracy improves.
• Multiple parameters are also useful if any one
parameter is affected by a fetal
condition/syndrome, such as achondroplasia on
femur length.
182. Other Biometry
Measurement of the
1. transcerebellar diameter,
2. foot length,
3. clavicle length,
4. intra/interorbital diameters,
5. kidney length,
6. sacral length,
7. scapula length, as well as the length of other
8. long bones of the extremity have also been evaluated to
determine gestational age.
• Studies have not shown that these parameters improve the
assessment of gestational age beyond that achieved with standard
biometry, however they may be useful in clinical situations in
which traditional biometry is difficult to attain (such as
uteroplacental insufficiency) or when fetal abnormalities are
present
183. Signs of Fetal Maturity
• Identification of certain US findings suggest that a fetus has
reached the third trimester and may correlate with fetal lung
maturity and gestational age.
These parameters are
1. The epiphyseal ossification centres of the distal femur
2. Proximal tibia, and proximal humerus.
• The measurement of these ossification centers does not
precisely correlate with gestational age; however, their presence
may be helpful
• late in pregnancy when the gestational age is not known.
• • The presence of distal femoral epiphysis has a PPV of 96%
for indicating a pregnancy of at least 32 weeks,
• the proximal tibial epiphysis has a PPV of 83% for indicating a
pregnancy of at least 37 weeks, and the proximal humeral
epiphysis has a PPV of 100% for indicating a pregnancy of at
least 38 weeks
184. At the end
1. First-trimester crown-rump length is the best parameter
for determining gestational age and should be used
whenever appropriate.
2. If there is more than one first-trimester scan with a mean
sac diameter or crown-rump length measurement, the
earliest ultrasound with a crown rump length equivalent to
at least 7 weeks (or 10 mm) should be used to determine the
gestational age.
3. Between the 12th and 14th weeks, crown-rump length
and biparietal diameter are similar in accuracy.
It is recommended that crown-rump length be used up to
84 mm, and the biparietal diameter be used for
measurements > 84 mm.
185. 4. Although transvaginal ultrasound may better
visualize early embryonic structures than a
transabdominal approach, it is not more accurate in
determining gestational age.
Crown-rump length measurement from either
transabdominal or transvaginal ultrasound may be
used to determine gestational age.
186. 5. If a second- or third-trimester scan is used to determine
gestational age, a combination of multiple biometric
parameters (biparietal diameter, head circumference,
abdominal circumference, and femur length) should be used
to determine gestational age, rather than a single parameter.
6. When the assignment of gestational age is based on a
third-trimester ultrasound, it is difficult to confirm an
accurate due date. Follow-up of interval growth is
suggested 2 to 3 weeks following the ultrasound.
