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A-Mode Area RatioIn
the early 1950’s, Dr. Wild discovered what he then called the A-scan area
ratio (A-mode area ratio) to enable classification of soft tissue
abnormalities.
Using a biological comparison technique he developed this discovery for
objectively diagnosing and detecting breast cancer.
In
his original experiment in 1949 to measure intestinal wall thickness with 15
megacycle pulse-echo ultrasound, he examined a fresh operative human gastric
specimen containing a gastric cancer.
Ultrasonic measurement of the specimen revealed a denser, more rigid
section of stomach wall which proved to be infiltrated with tumor cells.
Publication of results of this experiment opened the field of soft-tissue
pulse-echo ultrasound histological diagnosis. [Dr. Wild published the findings
of his experiment in the February 1950 issue of SURGERY, but because most
current digitized databases do not cover publications from this earlier period,
his historic discoveries and numerous
“firsts” in the field of diagnostic ultrasound are frequently
overlooked in database literature searches.] This
initial observation of differential sonic return by cancerous tissue was
followed by a series of experiments in which ultrasonic echoing of various fresh
soft tissues using time/volume graphic presentation of data were made.
At the sonic frequency levels (15 megacycles) used in Dr. Wild’s
studies, high levels of natural contrast were seen to exist between sonic energy
return of tumors compared to surrounding tissue of origin, resulting in positive
and negative contrast:
negative, if the tumor was benign; and positive, when malignant.
Initially, graphs of tumorous breast tissue, when compared with normal
comparative breast tissue were analyzed and subjectively interpreted.
Dr. Wild saw the need for a possible numerical, objective, index
of comparison to replace laborious subjective visual graphical
interpretation of comparison between normal tissue A-mode graphs and tumorous
tissue A-mode graphs.
This
search for a possible numerical index by Dr, Wild led to the A-scan area
ratio discovery.
The A-scan area ratio proved to be a relative value index number
predictive of breast tumor benignity or malignancy.
It was calculated by comparing the areas subtended under pairs of breast
A-mode graph traces to a base line and computing the ratio. In
a series of 117 clinical cases [Dr. Wild’s findings are published with J.M.
Reid in the Proceedings of the National Electronics Conference, Chicago, IL,
1956], the predictive value of the A-scan area ratio index number for
determining benignity or malignancy of a breast tumor was compared with
post-operative pathological diagnostic examination for tumor type, and found
statistically significant:
the A-scan area ratio number correctly characterized 98% of the malignant
tumors and 90% of the benign tumors in this series of breast tumor cases,
confirming the accuracy of Dr. Wild’s ultrasonically-based, objective,
numerical assessment of breast tumors.
Further occasional breast lump studies resulted in similar statistical
diagnostic accuracy in diagnosing breast pathology.
In 1963, Dr. Wild was able to demonstrate the feasibility of rapid ultrasonic clinical interrogation of the glandular breast with instantaneous readout based on comparative A-mode integral electronic processing (echometry). Modern
computing capabilities make it possible to develop objective, instantaneous,
automatic area-ratio readout for detecting and diagnosing tumors.
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Last modified: January 14, 2003 |