日本超音波医学会 第15回関西地方会 特別講演
The Use of US Contrast in the Diagnosis of Neoplastic Diseases
Robert F. Mattrey, M.D.
Professor of Radiology University of California, San Diego
座長 別府 慎太郎(大阪大学保健学科)
The latest generation agents are bubble-based and hold great promise
in solid organ gray-scale imaging.
Experience with agents limited to Doppler imaging has shown
that these agents increase the ability to visualize previously undetected flow,
but do not contribute significant additional data.
The newer agents that can alter tissue echogenicity on gray-scale promise
to add not only image contrast to aid in detection
but significant perfusion data to aid in characterization.
Further, these agents lend themselves
to the use of unique ultrasound instrumentation techniques
that have been shown to further increase tissue contrast
and improve vascular imaging.
The angiographic visualization of tumor microcirculation should aid
in tumor characterization.
This is possible with the use of robust and elastic microbubble
and high resolution harmonic imaging.
The tortuous vessels become evident.
Liver lesions enhance with a triple phase pattern
as bubbles traversed the arterial and portal venous systems
and finally accumulate in liver parenchyma.
During the arterial phase shimmering enhancement
of the tumor's vascular portions occurs
relative to the surrounding liver and areas of necrosis.
As the blood reaches the portal vein,
the liver parenchyma gradually enhances as the tumor vasculature
washes out until the parenchymal phase when the entire tumor becomes hypoech
oic relative to the enhanced liver.
It is not yet clear whether the parenchymal enhancement
when vessels are devoid of echoes is due to the entrapment of bubbles
in the sinusoids or the RE cells.
Because of the high blood volume of the liver and kidney
and the lower blood volume of tumors,
it is possible to employ techniques more sensitive to differences
in blood volume such as flash-echo, bubble extinction, acoustic stimulation,
or transient response imaging.
All these techniques are similar in principle,
although the latter 2 employ color Doppler techniques.
Tumors outside the liver enhance dramatically
in conparison to the less vascularized tissues such as muscle.
The arterial phase shows the most dramatic contrast effect.
With high resolution harmonic imaging,
the microvasculature and the blood supply to the lesion become apparent.
In summary, ultrasound contrast agents, particularly when combined
with contrast specific instrumentation
have the potential to significantly expand the role
of sonography in cancer detection and characterization.