3D ultrasound-based instrument for non-invasive measurement of Amniotic Fluid Volume

Abstract

A hand-held 3D ultrasound instrument is disclosed which is used to non-invasively and automatically measure amniotic fluid volume in the uterus requiring a minimum of operator intervention. Using a 2D image-processing algorithm, the instrument gives automatic feedback to the user about where to acquire the 3D image set. The user acquires one or more 3D data sets covering all of the amniotic fluid in the uterus and this data is then processed using an optimized 3D algorithm to output the total amniotic fluid volume corrected for any fetal head brain volume contributions.

Description

[0001]The following applications are incorporated by reference as if fully set forth herein: U.S. application Ser. No. 11 / 119,355 filed Apr. 29, 2005; Ser. No. 11 / 362,368 filed Feb. 26, 2006; Ser. No. 11 / 680,380 filed Feb. 28, 2007 and Ser. No. 11 / 925,654 filed Oct. 26, 2007.FIELD OF THE INVENTION[0002]This invention pertains to the field of obstetrics, particularly to ultrasound-based non-invasive obstetric measurements.BACKGROUND OF THE INVENTION[0003]Measurement of the amount of Amniotic Fluid (AF) volume is critical for assessing the kidney and lung function of a fetus and also for assessing the placental function of the mother. Amniotic fluid volume is also a key measure to diagnose conditions such as polyhydramnios (too much AF) and oligohydramnios (too little AF). Polyhydramnios and oligohydramnios are diagnosed in about 7-8% of all pregnancies and these conditions are of concern because they may lead to birth defects or to delivery complications. The amniotic fluid volume is...

AI Technical Summary

Benefits of technology

The invention is a system and method for using a handheld 3D ultrasound device to acquire and measure the volume of amniotic fluid in a uterus. The system uses a plurality of automated processes to locate and measure the fluid without relying on pre-conceived models of the fluid's shape. The user moves the device around the abdomen and uses 2D image processing to locate the fluid and acquire the necessary data. The data is then stored in the device or transferred to a computer for further analysis. The system can also acquire multiple 3D data sets from different anatomical sites and fuse them into a single 3D mosaic image for a more complete view of the uterus and amniotic fluid volumes. Overall, the invention provides a reliable and automated way to measure amniotic fluid volume in uteri, which can aid in the diagnosis and management of pregnant women.

Problems solved by technology

Polyhydramnios and oligohydramnios are diagnosed in about 7-8% of all pregnancies and these conditions are of concern because they may lead to birth defects or to delivery complications.

Even though the AFI measure is routinely used, studies have shown a very poor correlation of the AFI with the true AF volume (Sepulveda W, Flack N J, Fisk N M., “Direct volume measurement at midtrimester amnioinfusion in relation to ultrasonographic indexes of amniotic fluid volume,” Am J Obstet Gynecol April; 170(4): 1160-3, 1994).

This technique is the accepted gold standard for AF volume measurement; however, it is an invasive and cumbersome method and is not routinely used.

This technique is obviously dependent on observer experience and has not been found to be very good or consistent at diagnosing oligo- or poly-hydramnios.

However, the Segiv et al. method is interactive in nature and the identification of amniotic fluid volume is very observer dependent.

Moreover, the system described is not a dedicated device for amniotic fluid volume assessment.

Amniotic fluid pockets having shapes not consistent with the Grover et al. bladder model introduces analytical errors.

Moreover, the bladder volume instrument does not allow for the possibility of more than one amniotic fluid pocket in one image scan.

Therefore, the amniotic fluid volume measurements made by the Grover et al. system may not be correct or accurate.

None of the currently used methods for AF volume estimation are ideal.

This assumption conflicts with the observation that the received ultrasound signals are usually non-stationary and depth-dependent.

Since the algorithm is implemented in the frequency domain, the error introduced in PSF will leak across the spatial domain.

As a result, the performance of Wiener filtering is not ideal.

First, if the bottle has been stored upright the gel will fall to the bottom of the bottle, and vigorous shaking is required to get the gel back to the bottle tip, especially if the gel is cold.

This motion can be particularly irritating to sonographers, who routinely suffer from wrist and arm pain from ultrasound scanning.

Second, the bottle tip is a two-way valve: squeezing the bottle releases gel at the tip, but releasing the bottle sucks air back into the bottle and into the gel.

The presence of air bubbles in the gel may detract from its performance as a coupling medium.

Third, there is no standard application amount: inexperienced users such as Diagnostic Ultrasound customers have to make an educated guess about how much gel to use.

Fourth, when the squeeze bottle is nearly empty it is next to impossible to coax the final 5-10% of gel into the bottle's tip for dispensing.

Finally, although refilling the bottle from a central source is not a particularly difficult task, it is non-sterile and potentially messy.

However, pads do not mold to the skin or transducer surface as well as the more liquefied coupling gels and therefore may not provide ideal coupling when used alone, especially on dry, hairy, curved, or wrinkled surfaces.

Sontac pads suffer from the additional disadvantage that they are thin and easily damaged by moderate pressure from the ultrasound transducer.

Relating to cannula insertion, unsuccessful insertion and / or removal of a cannula, a needle, or other similar devices into vascular tissue may cause vascular wall damage that may lead to serious complications or even death.

The motion and force required to disengage the cannula from the guidance system may, however, contribute to a vessel wall injury, which may result in extravasation.

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