Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-06-15
2004-05-04
Imam, Ali M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06730034
ABSTRACT:
TECHNICAL FIELD
The invention relates to the measurement of adipose tissue and lean tissue using ultrasonic methods, compositions and devices, particularly methods, compositions and devices that facilitate placement of ultrasonic probe(s) using external anatomic landmarks, such as the umbilicus, and improve the reproducibility of ultrasonic measurements of object layer thickness.
BACKGROUND
Objects often include layers of different compositions that are difficult to measure directly and accurately. In many cases, the object's interior can not be accessed to allow for direct measurement. It may be impractical to intrude the object's interior or, if even using non-invasive techniques, it may be difficult to position the probe for accurate measurements.
For measurements of biological specimens, the thickness of underlying layers are particularly inconvenient to measure. Many such measurements are preferably taken in vivo, which makes invasive techniques impractical. If non-invasive techniques are used, they are often susceptible to operator errors and can be quite costly, as in the case of expensive medical diagnostic equipment.
In the case of body adipose tissue layers, measurements with skin calipers and water immersion tanks can be used to assess body adipose tissue. Such techniques, however, have a number of drawbacks.
Skinfold calipers use the principle that the amount of subcutaneous adipose tissue correlates to percent body adipose tissue (American College of Sports Medicine, ACSM's guidelines for exercise testing and prescription, 53-63 (1995)). With a skinfold caliper measurement, after the skin is pinched by an operator without inducing pain to the subject, the thickness of the skinfold is measured with the caliper. Caliper measurements of skinfold thickness have been used with various equations developed to predict body density and percent body adipose tissue (American College of Sports Medicine, ACSM's guidelines for exercise testing and prescription, 53-63 (1995)). Most of these equations, however, are sex-specific or only apply to certain populations. Other equations to estimate body density and percent body adipose tissue have been developed using regression models that can take into account data from larger population based studies (Jackson, A. S., Pollock, M. L., Br J Nutr, 1978: 497-504 (1978)).
Even with these improvements, however, skinfold calipers are subject to several serious sources of errors. First, skinfold caliper measurements are heavily operator dependent. The force used to pull back the skin by the operator and the location of the measurement site may vary significantly between different operators, or the same operator, resulting in poor reproducibility of measurements. Second, even though skinfold caliper measurements are based on the assumption that subcutaneous adipose tissue thickness correlates to percent body adipose tissue, skinfold calipers cannot measure the thickness of subcutaneous adipose tissue directly. Skinfold caliper measurements, instead, provide an estimate of subcutaneous adipose tissue thickness which, in turn, is then used to estimate percent body adipose tissue. Thus, two approximations are used to estimate percent body adipose tissue. Third, skinfold caliper measurements may overestimate subcutaneous adipose tissue thickness. When the skinfold is pulled back for the measurement, adipose tissue from adjacent sites can be pulled toward the measurement site causing an artificial increase in the amount of subcutaneous adipose tissue present in the selected body region. This problem is exaggerated in subjects with very elastic soft-tissue. Fourth, the inaccuracies associated with skinfold caliper measurements have lead to the use of equations requiring measurements of 3 body sites, 4 body sites, and even 7 body sites (American College of Sports Medicine, ACSM's guidelines for exercise testing and prescription, 53-63 (1995)). However, even with these adjustments, the inherent inaccuracies of skinfold caliper measurements, most importantly the inability to measure subcutaneous adipose tissue thickness directly, cannot be completely compensated.
Hydrostatic weighing is commonly considered the gold standard for determining body density and estimating percent body adipose tissue. Hydrostatic weighing relies on Archimedes' principle. A body submerged in water is buoyed by a counterforce equal to the weight of the water that it displaced. Bone and muscle tissue are denser than water, while adipose tissue is less dense. Therefore, a person with low percent body adipose tissue will have higher body density and weighs more in water than a person with higher percent body adipose tissue and the same air weight. Conversely, a person with higher percent body adipose tissue for the same air weight will weigh less in water.
Although hydrostatic weighing is considered the gold standard for body adipose tissue determinations, it is subject to several sources of error. First, hydrostatic weighing requires estimation of pulmonary residual volume, which may vary significantly between individuals. Although pulmonary residual volume can be measured using pulmonary function tests, this adds extra time and expense to the procedure, which could decrease patient compliance. Second, hydrostatic weighing does not account for the variability in bone density known to exist between different individuals and races (American College of Sports Medicine, ACSM's guidelines for exercise testing and prescription, 53-63 (1995)). In patients with high bone density, hydrostatic weighing will underestimate percent body adipose tissue. Conversely, in osteoporotic patients, hydrostatic weighing may seriously overestimate percent body adipose tissue. Third, hydrostatic weighing requires large and expensive displacement chambers, and complete patient immersion in water. The technical requirements and the expense of hydrostatic weighing limit its use in frequent longitudinal measurements of percent body adipose tissue that are desirable in ambulatory patients undergoing a nutritional regimen or exercise induced adipose tissue reduction. Fourth, submersion of the head underwater may be difficult or anxiety provoking for some individuals.
Ultrasonic examination has been used by the inventors of the present invention for assessing subcutaneous fat and muscle layer thickness (see PCT application PCT/US97/18993). While the previous inventions addressed and improved probe interrogation and positioning, reproducibility of ultrasonic measurements of subcutaneous fat and muscle layer thickness could be further improved by reducing other types of operator induced errors in ultrasonic probe positioning.
For example, to measure a fat layer, the probe may be placed in the abdominal region, the supraclavicular region, the suprailiac region, or the thigh region. These regions are, however, often difficult to reproducibly locate and frequently include anatomical areas stretching over several square centimeters of potential interrogation sites, which leads to significant variability in ultrasonic probe placement. This can result in inaccurate repeat measurements if probe placement is not generally maintained over the original interrogation site.
The variability in probe placement and in resultant ultrasonic measurements is typically even greater when measurements are not performed by a trained operator or when self-measurements are obtained. This variability in probe position and alignment decreases the reproducibility of the ultrasonic measurements which is of particular importance when repeat measurements are obtained at different time intervals as a means of detecting a longitudinal change in physiologic parameters measured by ultrasound. Repeat measurements of subcutaneous fat thickness are, for example, critical for monitoring the effects of a diet. Repeat measurements of muscle layer thickness are important for monitoring the effects of a physical exercise program.
Consequently, the present inventors have recognized the need for methods and devices for
Lang Philipp
Mendlein John D.
Hale and Dorr LLP
Imam Ali M.
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