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THREE-DIMENSIONAL
ULTRASOUND (3DUS) IN GASTROENTEROLOGY,
BLADDER AND SMALL PARTS
By
Leandro Fernandez, MD
Director, [LEAV] Vascular and Advanced Sonography Laboratory, Instituto
Médico La Floresta.
Director, Department of Ultrasound at the Vista Alegre Private
Hospital.
Director, SonoImagen,
School
of Advanced Sonography affiliated to
Jefferson Ultrasound Research and Education Institute
INTRODUCTION
3DUS
is a recent technique in clinical practice, which has been mostly
used in Obstetrics and Gynecology. Although there is relatively
little experience in other areas, it is increasing day by day.
Unfortunately,
most people still tend to believe that 3DUS is only about getting
nice and amazing pictures of baby faces, legs or genitalia. It is
precisely this belief and lack of information what has driven us
to present to you a set of some different and updated applications
that have proved to be useful as well as a range of other feasible
and promising uses of this outstanding technology, not only in the
already known applications in Obstetrics and Gynecology, but also
in the rest of the medical specialties.
There
are different types of 3DUS:
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Vascular |
|
Volumetric |
|
Surface |
|
Multiplanar |
|
Niche
Mode (which we refer to as Echo-Tomography) |
|
VOCAL
(Virtual Organ Computer-aided Analysis) |
All
these techniques can be widely used in diagnostic ultrasonography
for Gastroenterology, Bladder and Small Parts, among other medical
areas.
3DUS IN GASTROENTEROLOGY
3DUS
is an excellent tool to observe the spatial distribution of the
liver vessels. Besides, the arterial, venous and portal components
can be clearly seen. We can therefore, explore focal or diffuse
disorders and TIPS (Transjugular Intrahepatic Porto-systemic Shunt)
when the Vascular 3DUS is used. With Multiplanar 3DUS it is possible
to see the point of insertion of that prosthesis.
This
technology also allows to view the Portal system accurately. By
rotating the image of the hepatic hilium, we can see hidden branches
of the portal vein.
Portal
hypertension is also well evaluated, because the 3DUS makes a spatial
reconstruction of the dilated collateral vessels, illustrating the
vascular abnormality in these cases. It is possible to differentiate
the shape and dichotomy of the portal system in a normal liver from
those in a cirrhotic liver where the porta is irregular.
Using echo-enhancers (contrast agents) we can depict the neovascularization
of liver tumors and create a 3D rendering which allows us to observe
the vascular pattern of the different neoplasms such as hepatocarcinoma,
metastasis or hemangioma.
The
Multiplanar, Niche Mode or Echo-Tomography and VOCAL are extremely
useful in Radiology, Internal Medicine or Surgery, because they
help us define the anatomical relationships, identify the hepatic
segments affected and do a precise follow-up of oncological patients.
The Echo-Tomography provides milimetric “cuts” of any structure,
defining the precise limits of a lesion or eventual tumoral invasion
to another segments or organs. The VOCAL is a very useful tool in
these cases, because it is able to automatically calculate the volume
of a tumor.
3DUS
allows us to perform a remarkably clear visualization of gallbladder
stones, and examine with great detail their shape and size. Also,
it is possible to detect the calculi localization within the biliary
tract. We can see the structures that are behind the stones that
we would not be able to see with 2DUS, due to the posterior acoustic
shadow it produces.
Another advantage is that with 3DUS we are able to get a very clear
picture of the choledocho duct going from the liver to the retro
pancreatic portion.
The
pancreas is seen with multiplanar presentation, with high definition
of all its structures, including the Wirsung’s duct.
We
can get an overall image of the spleen and focus on the vascularity
organization. It is possible to observe infarction areas inside
the parenchyma with 3DUS Power Doppler.
There
are data supporting the superior accuracy of 3DUS when compared
to 2DUS. Some authors demonstrated similar advantages when comparing
3DUS and 3DCT, in abdominal studies.
VIRTUAL CYSTOENDOSCOPY: 3DUS OF THE BLADDER
This
is a new application of 3DUS in urology. Combining the volumetric
and surface rendering, we are able to see with remarkable detail
the internal surface of this organ, thus detecting the presence
of tumors, polyps, stones or any other disorders of the wall, urethra,
etc.
The
same types of internal urethral meatus described with optical cystoendoscopy,
can be seen with the 3DUS virtual cystoendoscopy.
VOCAL
help us calculate the pre and post micturition volume more accurately
than when using 2DUS technology. Despite the undeniable advantages
that 3 DUS can offer, it is of course necessary to carry out many
more studies comparing optical against virtual cystoendoscopy, in
order to validate these findings.
3DUS
IN SMALL PARTS (THYROID, PARATHYROID AND TESTICLE)
The
assessment of the thyroid and parathyroid glands is properly achieved
with 3DUS. We can discriminate normal anatomical structures from
pathological ones. The Multiplanar presentation and Niche Mode (Echo-Tomography)
are quite useful to determine the extension -inside or outside the
organs-, of nodules, cysts or tumors.
The
evidence of neovascularization is better viewed with 3DUS and probably
can suggests malignant origin of a neoplasm. Allowing for the spatial
orientation and the number of vessels, it could be possible to determine
the degree of potential malignity in a given tumor.
The
volume measurement is better assessed with 3DUS and given this,
we can perform studies that follow growth in order to decide medical
or surgical treatment.
The
VOCAL makes it possible to obtain a proper after-treatment follow-up
of focal disorders in thyroid and parathyroid.
SCROTAL 3DUS
In
my opinion, this method is of great value when we study testicle
and epididymus. The inflammatory processes, tumoral diseases or
torsion conditions are very well assessed with 3DUS.
Other
relevant applications include:
The
Multiplanar presentation allows us to get a virtual coronal view
of the entire scrotum, the testicle or just a small structure. A
very exact differentiation of simple or complex cysts can be ascertained
using Surface rendering in combination with Volumetric 3DUS.
As
well as in thyroid, VOCAL makes it possible to obtain a proper
after-treatment follow-up of focal disorders in testicle.
CONCLUSIONS
Three-dimensional
ultrasound is a new and outstanding technique that opens a new vision
in diagnostic ultrasonography. It offers a more comprehensive image
of anatomical structures and pathological conditions and also permits
to observe the exact spatial relationships.
New
applications in Internal Medicine, Surgery and Radiology are daily
emerging, coming from the curiosity of many doctors from all over
the world and from the necessity to assess the human body in a accurate
and non-invasive approach.
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