A Method for the Reduction of Blurring Due to Registration Error in Compound Ultrasound Images
The most intractable source of b lurring in cornpound B-mode images is the unknown highly variable sonic velocity along the many ray paths. Our objective was to investigate new image acquisition and processing methods to reduce the blurring effect of these errors. A scanner was constructed u sing a 5 MHz transducer with a 16 mm diameter and 70 mm focal d istance. Rectilinear scans are produced by translation, while the angle of incidence of a scan is changed by rotation of the transducer. The range of rotation was +/- 15 degrees and the angular increment was 1.0 degree. To simulate the refraction problem a variable thickness layer of fluid was inserted between the transducer and the object. Compound images produced with this apparatus are blurred due to refraction at the fluid layer interfaces. A method is reported here for producing a compound image with less blur by realigning the series of simple images, prior to compounding, using a cross c orrelation algorithm on selected t argets. Good results have been demonstrated on artificial phantoms. Further studies using excised human organs are under way, as is a more comprehensive analysis of the image processing algorithm.