Emerging trends in ultrasound imaging
Elastography
The
elastography technique in ultrasound is a feature that assesses the elasticity
profile of organs and tissues. It is very effective in distinguishing the
cancerous cells from the benign ones. This is because cancerous cells have a
lower elasticity profile than normal cells. As a result, the malignant cells
are easily quantified and this, combined with the 3D feature in an ultrasound
system, facilitates three-dimensional images where benign and malignant cells
are clearly distinguished. Therefore, given the accurate quantification and
coordinates of the malignant cells, biopsy rates are considerably reduced in
benign patients. Much research has been conducted globally to determine the
effectiveness of elastography on breast, thyroid, and liver pathologies.
Thyroid cancer, especially in nodules with undetermined cytology, has also been
efficiently determined by elastography. Additionally, it has proven to be a
success in detecting breast cancers of all types including the soft cancers
such as ductal carcinoma and mucinous cancers and also in detecting hepatic
fibrosis, leading to a reduction in the number of liver biopsies. There are
three types of elastography techniques available from different manufacturers
and they are as follows:
- Static elastography – In order to quantify the elasticity profile of benign and malignant cells, they must be subjected to initial compression so that the ultrasound machine can analyze and calculate the differences in elasticity of the cells. In static elastography the ultrasound technician must apply an external (manual) compression. The disadvantage of such a system is that the data it produces is not reproducible.
- Pulse elastography – This technique is similar to the static elastography technique mentioned above with the only difference being that the ultrasound machine in itself is capable for providing the initial compression, without the need for an operator’s intervention, following which the tissue characteristics are quantified. Unlike the previous technique, results are reproducible in pulse elastography.
- Transient elastography – In this technique, the ultrasound machine itself generates a mechanical wave with a uniform magnitude at every pulse such that the elasticity quantification of benign and malignant cells is very accurate. Transient elastography is also reproducible and it is the most advanced form of elastography currently available in the market.
According
to Business Insights’ assessment, it will take at least another four to six
years for elastography ultrasound to stabilize and gain full acceptance. While
elastography may be an advanced feature, it is currently in its nascent stage.
Although it may be an effective tool for determining and quantifying cancerous
cells, it needs to undergo further extensive study to fully substantiate its
effectiveness. This is because the characteristics of malignant cells are
unique to different organs and the physiological make-up of such organs also
differs among people globally. Collating elastography data from research
facilities all over the world can be a very complex process and Business
Insights recommends that ultrasound manufacturers form strategic partnerships
with research organizations and ultrasound associations in order to enhance the
accuracy of elastography evaluations.
Ultrasonic transducers and miniaturization techniques
Ultrasound
transducers with piezoelectric crystals have been bulky and were considered
unsuitable for use in intracardiac, transesophageal, and transthoracic
ultrasound scans. Such demerits have resulted in the advent of silicon
ultrasound transducers. Built using silicon wafers based on an integrated
circuit (IC) fabrication process, these transducer probes yield a higher image
resolution and allow the transducer to acquire the volume data instead of the
ultrasound equipment. Business Insights expects an increase in the adoption of
this technology as many patients will benefit from volumetric real time
imaging. This is because the ultrasound operator need not manipulate the probe
in different angles to acquire a clear image of the pathological area under
diagnosis and there is a reduction in the number of false positive diagnoses.
As a result, the need for a secondary diagnosis with another modality such as
an MRI or CT is eliminated in certain cases. This is an important reason that
will continue to drive the adoption of ultrasound systems with volumetric
imaging.
High intensity focused ultrasound (HIFU)
HIFU
is a newly developed technology for therapeutic purposes, especially for the
treatment of cancer and other pathologies, whereby high intensity waves causing
heat are used to destroy malignant and pathological tissues without harming the
normal ones. One of the growing applications of HIFU in the last few years is
in the treatment of prostate cancer, uterine fibroids, and hyperparathyroidism.
While the heating phenomenon is the underlying principle of HIFU, parameters
such as the magnitude of heat generated, the type of transducer employed, and
the probe design for specific targeting vary according to the application. In
other words, no single HIFU system can be used for the treatment of all
pathologies. HIFU is tissue specific and each HIFU-enabled application is
unique in terms of functionality and design.
The
therapeutic and non-hazardous benefits of HIFU have initiated organ-specific
research programs globally. Many clinical trials are being conducted by
research universities to determine the therapeutic effects of HIFU on organs
such as the bladder, kidney, pancreas, liver, and prostate. Although HIFU is
currently employed for the treatment of prostate cancer, it has not been as
effective as other therapeutic options and physicians still need to rely on
alternative methods such as radiotherapy and radical prostatectomy. Certain
areas where HIFU has been ineffective include lymph nodes, the brain, and
lungs.
The
therapeutic benefits of HIFU are also driving multiple research studies for
liver treatment applications. The Oxford Research Group in the UK, for example,
has performed extensive clinical trials to increase the efficiency of treatment
of liver lesions using HIFU. Other research entities in the UK are conducting
studies using HIFU for the treatment of kidney and pancreatic cancers in
patients where other forms of treatment have been rendered ineffective. Chinese
companies such as Mindray and Sonoscape are at the forefront of ultrasound
technology that encompasses improved portability and efficiency. Therefore, the
Chinese ultrasound manufactures are forming strategic associations with medical
research groups to conduct clinical trials using HIFU. The efficacy of HIFU
treatment in cancers of the liver, bladder, and pancreas is also being
determined in China by means of clinical trails. Globally, medical research
groups based in the UK and China have the largest sets of controlled data
pertaining to HIFU applications, followed by France, the US, and Germany.
Business Insights estimates that it will take another seven to eight years
before HIFU applications attain reasonable standardization for tissue-specific
cancer treatments. The collaboration of ultrasound companies with research
groups is also expected to increase over the next decade because HIFU clinical
trials are very complex and it is difficult for ultrasound companies to conduct
their own trials. Such associations will ensure HIFU technological advances.
Contrast-enhanced ultrasound (CEUS)
CEUS
utilizes an external substance known as contrast media, such as gas-filled
microbubbles with a lipid monolayer, in order to enhance visualization. Once the
contrast media is injected into the body toward the area of the targeted organ,
the echogenicity difference between the contrast media and the targeted tissue
becomes easy to distinguish. Since the medium is injected directly through the
body’s vascular pathways, CEUS is ideal for evaluation of blood flow in real
time with better resolution in comparison with other methods. Another area
where CEUS is highly preferred over conventional methods is orthopedics,
especially in the evaluation of arthritis, because physicians need to
distinguish the blood flow in and around the pathological area under
assessment.
Research
is also being conducted to determine the effectiveness of CEUS diagnosis on
specific organs. Studies have concluded that CEUS diagnosis of liver disease,
for example, is better than that diagnosed by CT, MRI or positron emission
tomography (PET), and it is useful for evaluation of liver graft parenchyma
perfusion, liver transplantation, and liver infarctions. It facilitates easy
interventional procedures on certain cases, enhances 3D viewing, and is capable
of determining stenosis and thrombosis. CEUS is also effective for imaging
portal and hepatic veins and hepatic arteries. There are dedicated contrast
medium manufacturing companies and, based on an assessment of the vast amount
of research that takes place in the CEUS segment, specific contrast media are
predicted to emerge for organ-specific applications.
Nerve block detection
Ultrasound
has given new dimensions to regional anesthesia by assisting nerve block
procedures. It not only helps in the visualization of peripheral nerves but it
is also capable of assessing the adequacy of the anesthetic agent. Real-time
visualization of the needle toward the target nerve reduces the risk of needle
entry into the spinal canal in addition to having other significant
applications in anesthesiology. Vendors are hopeful of offering these
technologies in the form of portable, wall-mountable, and hand carried systems.
These are expected to gain acceptance in the US and Europe.
