Combination of Digital Mammography with Semi-automated 3D Breast Ultrasound

Abstract

This paper describes work aimed at combining 3D ultrasound with full-field digital mammography via a semi-automatic prototype ultrasound scanning mechanism attached to the digital mammography system gantry. Initial efforts to obtain high x-ray and ultrasound image quality through a compression paddle are proving successful. Registration between the x-ray mammogram and ultrasound image volumes is quite promising when the breast is stably compressed. This prototype system takes advantage of many synergies between the co-registered digital mammography and pulse-echo ultrasound image data used for breast cancer detection and diagnosis. In addition, innovative combinations of advanced US and X-ray applications are being implemented and tested along with the basic modes. The basic and advanced applications are those that should provide relatively independent information about the breast tissues. Advanced applications include x-ray tomosynthesis, for 3D delineation of mammographic structures, and non-linear elasticity and 3D color flow imaging by ultrasound, for mechanical and physiological information unavailable from conventional, non-contrast x-ray and ultrasound imaging. IntroductionBreast ultrasound (US) is a valuable diagnostic adjunct to x-ray mammography for characterization of breast lesions such as cysts and solid masses, and evaluation of palpable masses that are obscured radiographically by dense breast tissue (1-3). Recently, there have been several studies suggesting the potential emerging role of ultrasound as a screening adjunct to x-ray mammography (4-9). For example in a study of 11,130 asymptomatic women, Kolb et al. (9) recently reported that the combined sensitivity of x-ray mammography and radiologist performed free-hand 3D breast ultrasound for women with dense breasts [BI-RADS (10) density category 4] improved to 94% from 48% for x-ray mammography alone. When mammographic findings indicate the need for follow up imaging with ultrasound, the specific regions in the breast requiring further interrogation must be anatomically identified for subsequent positioning and manipulation of an ultrasound probe. The critical step of accurately localizing the regions of interest however can be challenging to implement for a number of reasons. First, mammograms and sonograms are acquired with the patient in different positions -upright for the mammogram and supine for the US examination. This requires the sonographer to estimate the approximate 3D location of the region of interest from a 2D x-ray projection of a deformable breast. Second, US imaging is performed predominantly through free-hand manual manipulation of ultrasound probes in direct contact with the breast. The experience and skills of the operators may impact the accuracy of locating the region of interest. imaging locations and orientations and from a lower level of skill in detection and discrimination of lesions. Third, mammograms and sonograms may not be acquired on the same day. Therefore normal fibrocystic changes occurring over a period o...

Evaluating Thin Compression Paddles for Mammographically Compatible Ultrasound

“…The transducer carriage was springloaded to ensure constant contact with the paddle. Hardware and software were developed for both systems to semi-automatically drive the transducer across the compression paddle, as well as to communicate with the Logiq 9 ultrasound system to trigger image and data acquisition (Kapur et al 2004). …”

“…The preferred paddle would have an acoustic impedance that is well matched with both breast tissue (~1.5 kg/m 2 s) and the transducer lens to minimize reverberations and beam refraction. These properties are further discussed in Kapur et al (2004).…”

Spatial registration of temporally separated whole breast 3D ultrasound images

“…Other hardware and software interfaces developed to perform automated scanning, which included computer triggering of the Logiq-9 system for data acquisition, were discussed elsewhere. 33 The region of interest ͑ROI͒ was identified in the automated grayscale scans to guide a cardiac-gated Doppler scan that was performed over the ROI in a single sweep of the U.S. transducer. This study was performed on patients with cancers or with undiagnosed suspicious masses having sufficient blood flow to be visible in the freehand U.S. Doppler scan performed by the radiologist.…”

“…Our 3D U.S. system has been augmented with a motorized transducer carriage above a special compression plate developed in order to improve the coverage over the whole breast. [33][34][35][36][37][38] U.S. imaging, along with other coherent imaging systems, suffers from speckle noise caused by interference effects between overlapping echoes from randomly distributed structure scatterers that are too small to be resolved. Speckle degrades the signal-to-noise ratio of the image and this could lead to reduced performance in registration compared to most other imaging modalities.…”

Robot guidance of an ultrasound probe toward a 3D region of interest detected through X-ray mammography

“…To overcome these difficulties, Kapur et al proposed an imaging apparatus to combine MX and automated US scans [14], see Fig.3. A 2 degrees of freedom (DOFs) robotized probe holding framework is mounted on top of the compression paddle.…”