Ultrasound-Based Absolute Scatterer Concentration Measurement Technique: Image Volume Estimation from Scatter Spread Function Extracted From the Image

Technology

The Inventors have developed a technique to measure the absolute concentration of scatterers in a material by using only the ultrasound image acquired by linearly scanning a disk single element transducer. Specifically, the width of a beam produced by the transducer can be estimated from the spreading of individual scatterers included in the sample. The beam widths can then be mapped as a function of the axial position of the transducer and used to estimate the image volume. If the concentration is calculated for each frame of images, these concentrations can be combined to produce a final concentration of the sample. This technique is mainly for materials with low concentration of scatterers where, on average, there is less than one scatter per resolution cell and therefore individual scatterers can be distinguished in the image. The ability to measure absolute concentration in this low range of concentration is especially significant because other established concentration measurement instruments such as a hemocytometer, coulter counter, etc. are not accurate due to the issue of small sampling volume. The reduction to practice has been carried out for linearly scanned disk single imagining only, but extension to array imaging is also possible. 

Problem Addressed

Ultrasound-based measurement of absolute concentration of scatterers has a wide range of potential applications, such as in microbiology, cell culture, and blood work. When a material is dilute and a scatterer size is similar to the wavelength produced by ultrasound, individual scatterers can be distinguished in an ultrasound image. A variety of techniques have been developed for estimating concentration based on overall backscatter energy and assumptions about the geometry of an ultrasound scan. The actual shape of an ultrasound beam may vary significantly based on the medium being imaged, the interface between an ultrasound transducer and the scan volume, and a variety of other factors. However, current techniques measuring concentration based on backscatter have avoided precise quantification of image volume in favor of generalized assumptions about the shape of the ultrasound beam and the scan geometry. There remains a need for an ultrasound-based concentration measurement technique where both the scatterer count and the scan volume are measured concurrently to provide absolute concentration. 

Advantages

• Allows for an accurate absolute concentration measurement of scatterers nondestructively (since the sample does not have to be disposed)
• Allows for a larger sampling sampling volume and therefore results in a more accurate measurement
• Can be used as a tabletop or a portable device for particle counting and concentration measurement