For pregnancy detection, the instruments determine if amniotic fluid is present by detecting an echo from the interface between the interior of the far side of the uterus and amniotic fluid. The PREG-ALERT PRO® displays echoes as “spikes” on a TV-like screen. Travel time is displayed in equivalent units of distance. The SONO-GRADER® displays the words “Pregnant” or “Not Pregnant” along with the calibrated scale. The PREG-TONE® and PREG-TONE II PLUS® indicate the pregnancy status by an audible tone. These instruments use an electronic “window” to place upper and lower time limits for accepting a returning echo as valid indication of pregnancy.
For backfat measurement, valid echoes are produced by the interface between fat and the tissue layer separating fat layers and also the interface between the bottom layer and loin muscle. The LEAN-MEATER®automatically determines how many fat layers exist and displays that number along with the total depth including skin. The LEAN-MEATER is not designed to measure loin depth.
The PREG-ALERT PRO and SONO-GRADER visually display all valid echoes from all layers comprising skin, fat and loin muscle.
The SONO-GRADER has several options for making loin muscle measurements at the 10th rib. In all cases, the instrument subtracts the total fat measured at P2. It should be noted that there are numerous factors that can cause variations in readings from time to time even when using the same method; there is no unvarying “absolute”. A “standard” is only that which the user chooses to call a standard. Therefore, provision is made for altering the speed of sound factor individually for fat and loin tissues. This permits the user to adjust the readings to track those of any method the user chooses to use as a “standard”.