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Thứ Sáu, 11 tháng 7, 2014

Breast Ultrasound Screening, Dr. Jason Birnholz.


Screening mammography
Screening mammography seems to have followed a different trajectory, being a collection of separate local efforts continually fueled by an overwhelming barrage of popular media promotions. Like tainting a jury, this kind of public relations, though always well-intentioned, probably prevented an unbiased evaluation of the method itself.
In regard to studies supporting x-ray mammography, questions have been raised about the inherent validity of our most common tests for significance (i.e., Fisherian statistics) with many types of hypothesis-driven study designs. Dr. John Ioannidis made the case in a fascinating essay in 2005 that most published research findings are false.
The negative side has been met with several technical advances in x-ray mammography itself and a much deeper understanding of the molecular biology of breast cancer and the subdivision of "cancer" into subtypes with differing behaviors and drug sensitivities.
Dr. Nikola Biller-Andorno, PhD, and Dr. Peter Jüni shared their opinion that screening mammography should be discontinued in Switzerland in a recent issue of the New England Journal of Medicine (May 22, 2014, Vol. 370:21, pp. 1965-1967).
Noting that the first screening mammography trial was performed 50 years ago, Biller-Andorno and Jüni shared graphical representations of the real effect of mammography and how women perceive the effects, again emphasizing the potential bias of undocumented public thought in our interpretations of utilization studies or how we act on them.
Ultrasound and the breast
You must be wondering what, if anything, this has to do with ultrasound. It does relate -- perhaps more than you might think. One of the earliest papers on ultrasound was published by John Wild and John Reid in 1952 ("Further pilot echographic studies on the histologic structure of tumors of the living intact human breast"). This study used A-mode scanning to differentiate benign and malignant masses.
The notion of ultrasound screening was promoted in the 1980s by Dr. Elizabeth Kelly-Fry in Indianapolis and by my dear friend, the late Dr. Toshiji Kobayashi in Japan. For years I avoided this application, as I didn't think the equipment was ready.
One of the main problems ultrasound has always faced is that even a few clinical failures from technically premature use overshadow a lot of reliable uses in other applications. The other factor is that if you accept that diagnosis must be as early as possible, then you cannot beat x-ray detection of microcalcifications, which will precede the formation of a mass of abnormal cells.
I changed my mind, however, due to high-frequency, noise-suppressing equipment improvements in the past few years. Also, I had been finding a lot of advanced breast cancers with that equipment in referrals from alternate healthcare sources of patients who were fearful of MDs and who had not had any kind of surveillance other than some breast thermography, which I had thought had failed and disappeared in the 1970s.
Doing breast ultrasound is actually pretty easy. Cancers all arise in gland tissue that are the radially arranged reflective patches surrounding ducts. At higher frequencies and with noise suppression, cancers -- being more uniform in architecture -- are hypoechoic, improving inherent contrast against the parenchymal surround.
Automated breast ultrasound
Automated breast ultrasound systems (ABUS) are being promoted for screening. Seems reasonable, doesn't it? Actually, this may be the best ultrasound example I know of market-driven technology development in the absence of understanding of the clinical application.
Here's why: Detection of low-contrast targets is improved when they are moving. That has been known and studied forever. It's why that lonely sailor in the crow's nest scans the horizon instead of staring fixedly at it. Or, think of detecting a moving plane so far off that none of its features are evident. There is a sizeable collection of literature on contrast detection in static and moving images.
The automated systems have beautiful static displays, which seem to resemble the kind of images that mammographers, working with a static form of imaging, use daily. If you want to do breast nodule detection, forget automation, though, and have a human observer slide a transducer along radials from the nipple while watching the screen.
Most people who do breast ultrasound will tell you that is how you find lesions. When something has caught your eye, you go back and get static images of the nodule to document its location and features.

You could use your ABUS if you could page back and forth through the axis of the scan image set when you're reviewing the case, but that does not seem to be an efficient way for a clinic to utilize its personnel.

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