Technical Keynote Session 2

Image Quality’s Effect on Real-time Ultrasound

By Meghan Richey

Real-time ultrasound has become the standard for collecting phenotypic measurements for external fat, intramuscular fat and ribeye area. To ensure the quality of this data, the Ultrasound Guidelines Council (UGC) categorizes ultrasound images using a seven-point scoring system based on image quality. It accepts only those with scores 1-5 for use in national cattle evaluations (NCE).

“If this image quality scoring system is able to differentiate images according to the accuracy with which they can be interpreted, then it stands to reason that an inherent and currently unaccounted for bias is introduced when multiple image quality scores are represented within a contemporary group,” said University of Nebraska professor Matt Spangler at the 2009 Beef Improvement Federation (BIF) symposium May 1 in Sacramento, Calif. Spangler presented data from a study aiming to determine the factors that have the largest influence on the absolute values of the bias between ultrasound predictions and carcass values, including rib fat, percentage of intramuscular fat and ribeye area.

For ultrasound ribeye area and rib fat, the study found that image quality was not a significant source of variation contributing to bias between the ultrasound predictions and carcass value, Spangler said. Ribeye area predictions were affected more by the technician interpreting the ultrasound and the individual animal, accounting for 32% of the variation. Intramuscular fat was most affected by the particular ultrasound machine and its software, the interpreting technician and the individual animal, accounting for 52.43% of the variation.

“Previous studies have shown that the skill level of the image-collecting technician, as well as the interpreting technician, can influence prediction bias,” Spangler said. “Individual animals also create unique sources of variation that can create differences in prediction bias, such as hide thickness and extreme values for ether-extracted fat percentage that may fall outside of the values used to develop the ultrasound software models.”

Ultimately, study results suggested that including multiple image quality scores within a single contemporary group does not yield unaccounted for bias. The 1-7 scoring system is best used as quality control in filtering out unusable data and as a teaching tool.

Editor’s Note: This summary was written under contract or by staff of Angus Productions Inc. (API). To request reprint rights contact Shauna Rose Hermel, editor, at 816-383-5270. PowerPoints are posted with permission of the presenter and may not be reproduced in whole or in part without the express permission of the presenter.

The 41st BIF Research Symposium and Annual Meeting was hosted by the California Beef Cattle Improvement Association and the California Cattlemen's Association. For more information, visit www.bifconference.com or www.calcattlemen.org/bif2009.html.