The effect of scatter and glare on image quality in contrast-enhanced breast imaging using an a-Si/CsI(TI) full-field flat panel detector.

The purpose of this study is to evaluate the performance of an antiscatter grid and its potential benefit on image quality for a full-field digital mammography (FFDM) detector geometry at energies typical for temporal subtraction contrast-enhanced (CE) breast imaging. The signal intensities from primary, scatter, and glare were quantified in images acquired with an a-Si/CsI(T1) FFDM detector using a Rh target and a 0.27 mm Cu filter at tube voltages ranging from 35 to 49 kV. Measurements were obtained at the center of the irradiation region of 20-80 mm thick breast-equivalent phantoms. The phantoms were imaged with and without an antiscatter grid. Based on these data, the performance of the antiscatter grid was determined by calculating the primary and scatter transmission factors (T(P) and T(S)) and Bucky factors (Bf). In addition, glare-to-primary ratios (GPRs) and scatter-to-primary ratios (SPRs) were quantified. The effect of the antiscatter grid on the signal-difference-to-noise ratio (SDNR) was also assessed. It was found that T(P) increases with kV but does not depend on the phantom thickness; T(P) values between 0.81 and 0.84 were measured. T(S) increases with kV and phantom thickness; T(S) values between 0.13 and 0.21 were measured. Bf decreases with kV and increases with phantom thickness; Bf ranges from 1.4 to 2.1. GPR is nearly constant, varying from 0.10 to 0.11. SPR without an antiscatter grid (SPR-) ranges from 0.35 to 1.34. SPR- decreases by approximately 9% from 35 to 49 kV for a given phantom thickness and is 3.5 times larger for an 80 mm thick breast-equivalent phantom than for a 20 mm thick breast-equivalent phantom. SPR with an antiscatter grid (SPR+) ranges from 0.06 to 0.31. SPR+ increases by approximately 23% from 35 to 49 kV for a given phantom thickness; SPR+ is four times larger for an 80 mm breast-equivalent phantom than for a 20 mm breast-equivalent phantom. When imaging a 25 mm PMMA plate at the same mean glandular dose with and without an antiscatter grid, the SDNR is 4% greater with a grid than without. For an 75 mm PMMA plate, the SDNR is 20% greater with a grid. In conclusion, at the higher x-ray energy range used for CE-DM and CE-DBT, an antiscatter grid significantly reduces SPR and improves SDNR. These effects are most pronounced for thick breasts.

Three-dimensional motion measurements using feature tracking.

Feature tracking was developed to efficiently compute motion measurements from volumetric ultrasound images. Prior studies have demonstrated the motion magnitude accuracy and computation speed of feature tracking. However, the previous feature tracking implementations were limited by performance of their calculations in rectilinear coordinates. Also, the previous feature tracking approaches did not fully explore the three dimensional (3- D) nature of volumetric image analysis or utilize the 3-D directional information from the tracking calculations. This study presents an improved feature tracking method which achieves further computation speed gains by performing all calculations in the native spherical coordinates of the 3-D ultrasound image. The novel method utilizes a statistical analysis of tracked directions of motion to achieve better rejection of false tracking matches. Results from in vitro tracking of a speckle target show that the new feature tracking method is significantly faster than correlation search and can accurately determine target motion magnitude and 3-D direction.

Interactive volume rendering of real-time three-dimensional ultrasound images.

Real-time, three-dimensional (RT3D) ultrasound allows video frame rate volumetric imaging. The ability to acquire full three-dimensional (3-D) image data in real-time is particularly helpful for applications such as cardiac imaging, which require visualization of complex and dynamic 3-D anatomy. Volume rendering provides a method for intuitive graphical display of the 3-D image data, but capturing the RT3D echo data and performing the necessary processing to generate a volumetric image in real time poses a significant technical challenge. We present a data capture and rendering implementation that uses off-the-shelf components to real-time volume render RT3D ultrasound images. Our approach allowed live, interactive volume rendering of RT3D ultrasound scans.

Real-time three-dimensional echocardiography to construct clinically ready, load-independent indices of myocardial contractile performance.

BACKGROUND: Real-time 3-dimensional echocardiography (RT3DE) reliably determines intracardiac chamber volumes without left ventricular (LV) geometric assumptions, yet clinical assessment of contractile performance is often on the basis of potentially inaccurate, load-dependent indices such as ejection fraction. METHODS: In 6 chronically instrumented dogs, RT3DE estimated LV volumes at various loading conditions. Preload recruitable stroke work and end-systolic pressure-volume relationships were constructed. RT3DE-derived indices were compared with similar relationships determined by sonomicrometry. RESULTS: Highly linear preload recruitable stroke work and end-systolic pressure-volume relationships were constructed by RT3DE and sonomicrometry. Mean preload recruitable stroke work slopes correlated between methods, but volume intercepts differed as a result of geometric assumptions of sonomicrometry. Conversely, RT3DE-derived end-systolic pressure-volume relationships did not correlate well with sonomicrometry. CONCLUSIONS: These data are unique in reporting load-independent measures of LV performance using RT3DE. These techniques would strengthen evaluation of LV function after myocardial ischemia or cardiac operation, in which frequent changes in ventricular geometry or loading conditions confound functional assessment by more traditional methods.

Heart to Heart: a computerized decision aid for assessment of coronary heart disease risk and the impact of risk-reduction interventions for primary prevention.

Heart to Heart is a computer-based decision aid for patients and providers that provides personalized, evidence-based information about coronary heart disease (CHD) risk and potential risk-reducing interventions. To develop Heart to Heart, the authors used Framing-ham risk equations and systematic reviews of risk-reducing interventions. The Web version was programmed using PHP: Hypertext Processor, a Web-based programming language, and has separate interfaces for providers and patients. The authors subsequently developed a modified version for personal digital assistants. Heart to Heart uses information about a patient's CHD risk factors (age, gender, total and high-density lipoprotein cholesterol levels, diabetes, smoking, systolic blood pressure, and left ventricular hypertrophy) to calculate risk of total CHD events over 5 or 10 years. Patients and providers can then examine the effect of introducing one or more risk-reducing interventions (aspirin, lipid-lowering drug therapy, antihypertensive medication, or smoking cessation) on the patient's CHD risk. Future research will be directed to determining whether Heart to Heart can improve utilization of effective CHD risk-reducing interventions.