Organ-specific ultrasound imaging
Overview
The
ultrasound segment has been undergoing an evolutionary phase over the past five
to seven years. Apart from mainly being used for primary diagnosis, innovations
in ultrasound are also applicable to secondary diagnosis, on a par with other
advanced imaging equipment for secondary diagnosis such as MRI and CT. The
primary driver for such ultrasound innovations applicable to secondary
diagnosis is its non-hazardous nature, since no radiation source is utilized.
Dedicated ultrasound has evolved for diagnosing specific organs such as the
breast, liver, abdomen, prostate, thyroid, kidney, ureter, bladder, testicle,
and ovary. Different types of organ-specific ultrasound imaging are listed
below.
Thyroid imaging
Thyroid
ultrasound is used for diagnosing thyroid pathologies and parathyroid glands
mainly to distinguish cysts from tumors. Other functionalities include
evaluation of nodular and endemic goiter, inflammations, palpation anomalies,
thyroid medullary carcinoma, papillary carcinoma, Sipple’s syndrome (multiple
endocrine neoplasia II), hypothyroidism, and hyperthyroidism. A color Doppler
is utilized for detecting abnormal vascularity of the thyroid gland and
prominent ultrasound manufacturers offer customized linear probes for such
scanning. These linear probes operate at a frequency ranging from 3.5MHz to
7.5MHz. Fine needle aspiration (FNA) is performed on patients diagnosed with
malignancy in the thyroid gland and it is helpful in the determination of a
carcinoma’s recurrence. Globally, there is an increasing incidence of thyroid
nodules among senior citizens of more than 60 years of age. Thyroid ultrasound
is used to help in performing biopsies. However, even after the application of
a thyroid ultrasound, physicians may find it hard to recommend the appropriate
biopsy required owing to factors such as gland size, composition, and
echogenicity. This is due to the lack of any global standards that govern
accurate prognosis of thyroid biopsy.
Extensive
research is being performed globally in order to understand the symptoms and
causes of thyroid pathologies and how a thyroid ultrasound can contribute to
better diagnosis. The American Association of Clinical Endocrinologists (AACE)
and the American Institute of Ultrasound in Medicine (AIUM) are working toward
establishing standards for effective diagnosis of thyroid pathologies using
ultrasound. In order to streamline the process, so that all ultrasound
technicians will have a standardized set of protocols, the AACE and AIUM have
developed the Endocrine Certification in Neck Ultrasound (ECNU) program,
through which endocrinologists will need to undergo a specific number of hours
of training, pass a written exam, and provide case-study reports from a
real-time thyroid ultrasound examination. In addition to such initiatives,
medical research universities are conducting studies to test the efficacy of
thyroid ultrasound, with an objective to not only enhance diagnosis but also
improve interventional procedures.
The
Endocrinology Department at the Chinese PLA General Hospital has conducted
research using thyroid ultrasound to examine calcification patterns in thyroid
nodules to detect and predict malignancy. However, the study concluded that
determination of microcalcifications alone does not confirm malignancy.
Researchers at the John Hopkins University School of Medicine determined the
effectiveness of thyroid ultrasound in the preoperative evaluation of cervical
lymph nodes in patients with predictable thyroid FNA biopsy. At the San
Francisco Medical Center based at the University of California, researchers
concluded that thyroid ultrasound accompanied by FNA is more effective than
executing invasive thyroid biopsy. The medical center also recommended
technology upgrades to thyroid ultrasound so that the number of interventional
procedures can be reduced. The University of Toronto conducted a study on the
effectiveness and benefits of thyroid ultrasound for long-term diagnosis of
patients suffering from thyroid cancer. The study concluded that thyroid
ultrasound scans combined with tumor-markers helped in predicting cancer
recurrence. The Thomas Jefferson University, based in Philadelphia, conducted a
research study that concluded incision length can be appropriately determined
using thyroid ultrasound for minimally invasive surgeries.
While
much research is being performed on pathologies associated with specific
organs, developments in this ultrasound sector are in the nascent stage and
require the cooperation of medical research universities, ultrasound
manufacturers, endocrinology associations, and operating technicians. Business
Insights predicts that it will take another seven to 10 years for thyroid
ultrasound equipment to create its niche market where its thyroid specific
functionalities are not available in other ultrasound systems.
Breast imaging
Evaluation
of pathologies such as breast lump, biopsy of breast masses, marker-wire
placements, and breast cysts are done by the application of breast ultrasound.
Mammography is still one of the major procedures by which breast pathologies
are evaluated but, as noted with other procedures, mammography uses a
radioactive source for its application, and ultrasound manufacturers started
innovating ultrasound specifically to diagnose breast-related pathologies. The
adoption of breast ultrasound has been seen in western European countries owing
to their less stringent laws (in comparison with the US) on safety policies and
faster turnaround time to market. Europe’s adoption has been followed by the
US, where breast ultrasound machines are employed in equal measure to
mammography. Instead of performing multiple examinations on mammography alone,
physicians utilize breast ultrasound as a secondary diagnostic tool to gain
better understanding of breast related pathologies.
One
of the major drawbacks of mammography is that it is incapable of effective
diagnosis for women with large breast masses, and ultrasound offers better
contrast resolution than a mammogram to diagnose cyst formation in large breast
masses. Another advantage of ultrasound is its ability to detect
microcalcifications. However, the spatial resolution of ultrasound is not on a
par with the mammogram, so mammography proves to be a better choice of
diagnosis for women having smaller breast masses.
The
emergence of 3D/4D technology has influenced the adoption of breast ultrasound
because it eliminates the complex probe manipulations required with the
standard 2D visualization. Moreover, image acquisition is faster with 3D
technology and this benefits the productivity of the radiology department.
Measurement of tumor volume is accurate in 3D systems and conditions such as
duct papilomas and microlobulations are also determined. The 3D/4D feature
increases the accuracy of needle placement. 4D in particular is useful for
tumor detection when combined with the application of contrast media, FNA, cyst
aspiration, and core needle biopsy. In the US and Europe, many private
hospitals and clinics promote themselves as dedicated breast examination
centers. In these geographies, there are many government initiatives that
promote awareness for breast cancer and the significance of early diagnosis.
The last three to four years have witnessed a drastic rise in the number of
breast cancer diagnoses in the US and Europe by about 10–12%.
Most
major ultrasound manufacturers offer a 3D/4D feature in their product
portfolios, whereas only a few companies have the elastography features for
advanced tumor diagnosis. With the help of elastography, physicians can
identify lesions in the breast by quantifying the stiffness of the lesion. It
is a technology that is slowly gaining momentum over mammography at large
hospitals and research universities. Business Insights predicts that the
elastography technology will continue to evolve and within the next three to five
years all prominent manufacturers of ultrasound will offer elastography in
their product portfolio.
Liver imaging
Abdomen
ultrasound, as the name implies, is concerned with the evaluation and diagnosis
of kidney, liver, gallbladder, pancreas, and spleen. It is the primary
diagnostic procedure that is recommended for pathologies such as gallstones,
abdominal infection, enlarged spleen, ascites, liver cirrhosis, hepatitis B and
C, typhoid, and jaundice. In the last seven to eight years, pathologies associated
with the liver have been an area of significant interest in the medical
research field. In fact, the amount of research conducted on liver related
pathologies has been so high that prominent ultrasound companies have unveiled
liver-specific ultrasound equipment. Siemens, for example, introduced their
first liver specific ultrasound in 2008, and this is capable of analyzing and
quantifying specific sections of the liver. Siemens’ patented Acoustic
Radiation Force Impulse (ARFI) technology compresses liver tissues with
acoustic energy to determine the liver’s physiological make-up both
qualitatively and quantitatively without the need for biopsy.
The
application of CEUS is very effective in the characterization of focal liver
lesions (FLL). This is because CEUS has superior temporal resolution in
comparison with other ultrasound systems and is well suited for the evaluation
of hemangiomas, steatosis, and metastasis. There are specific contrast media
available for diagnosing different types of abdominal pathologies. Liver
specific contrast media also exist for determining parenchymal change and
metastases. Ultrasound manufacturers are also offering specially designed
probes that will acquire the best possible images depending on the patient’s
physiology.
