We developed a freehand method for ultrasound elastography, which can be applied during a routine sonographic examination with off-line calculation of strain images (elastograms). Forty-eight patients with 53 breast lesions were examined and, after biopsy or operation, histologic reports were available for all lesions. The correlation coefficient of time delay estimates was used as a quality criterion for the subsequent calculation of elastograms. Beyond the qualitative evaluation of elastograms, we suggested a semiquantitative approach. For that purpose, the elastogram of each lesion was normalized to an overall strain of 1% (i.e., the average strain in the image was set to 1%). After normalization, we determined mean strain values inside and outside of each lesion, respectively. Defining solid lesions as benign and malignant lesions except for fibrous mastopathy, we found significant difference in strain between solid lesions and their surrounding tissue. However, that result must not be misunderstood to suggest that it was possible to distinguish benign from malignant lesions in general. Still, we address the potential of ultrasound elastography to improve the detection and localization of breast lesions as well as their differential diagnosis. Besides, we developed a freehand applicator for further studies, which guarantees a homogeneous axial compression regardless of the experience of the examiner.

Intravascular ultrasound images are limited by a poor lateral resolution and elevated grating lobes. In this paper, two reconstruction algorithms are presented which succeed in improving the lateral resolution and reducing the grating lobes by means of the synthetic aperture focusing technique (SAFT). For the time domain reconstruction, appropriately time-delayed and weighted signals are summed up. The frequency domain reconstruction is based on the similarity of the recorded signals with chirp signals. The reconstruction results experimentally confirm that the frequency domain reconstruction creates a better lateral resolution and requires less computation time. However, the time domain reconstruction produces lower grating lobes and hence results in a better overall image quality.

Article Dreidimensionale Ultraschall-Elastographie der weiblichen Brust: in-vitro- und in-vivo-Ergebnisse was published on January 1, 1998 in the journal Biomedical Engineering / Biomedizinische Technik (volume 43, issue s1).

Article Dreidimensionale Simulation und Optimierung der Ultraschall-Mammographie was published on January 1, 1996 in the journal Biomedical Engineering / Biomedizinische Technik (volume 41, issue s1).