[Optoacoustic imaging]. / Optoakustische Bildgebung.

CLINICAL/METHODICAL ISSUE: Imaging modalities play an increasing role in today's medical diagnostics. Among them, ultrasound (US) is one the most widespread techniques although it has relatively poor soft tissue contrast. Furthermore, US is poorly suited as a modality for molecular imaging (MI). STANDARD RADIOLOGICAL METHODS: Methods such as Doppler and contrast-enhanced US (CEUS) allow functional imaging of the vasculature; however, ultrasound-based MI remains limited to the vascular network due to the size of available contrast agents. METHODICAL INNOVATIONS: Optoacoustic imaging combines the benefits of optics (high contrast) with those of acoustics (low scattering and high resolution). In this technique, signals are generated in tissue with high contrast depending on the local optical absorption coefficient and detected with an acoustic procedure. PERFORMANCE: Optoacoustic imaging can intrinsically be scaled in terms of resolution and is therefore usable in various applications from in vitro microscopy, to preclinical small animal imaging up to clinical imaging. With a resolution in the range of clinical ultrasound systems (100-400 µm), highly scattering tissue can be imaged up to several centimeters in depth. ACHIEVEMENTS: In contrast to conventional ultrasound imaging, optoacoustic techniques are highly suitable for MI. Various contrast agents as well as different technical implementations of the approach have already been preclinically evaluated. The technique is currently close to being transferred to clinical implementation and the first studies have already been started. PRACTICAL RECOMMENDATIONS: Clinical studies are ongoing with respect to early diagnosis of breast cancer and arthritis. Furthermore, the suitability of the technique for skin imaging is currently being investigated.

[Ultrasound hard tissue detection for registration in orthopedics and traumatology]. / Ultraschall-Hartgewebedetektion zur Registrierung in der Orthopädie und Traumatologie.

The application of x-ray diagnostics for intraoperative navigation and for registration of hard tissue structures is restrained due to high radiation loads and the not given real time ability. Previous approaches with conventional ultrasonic imaging are only interactively applicable due to the high information content of soft tissue optimised B-mode-images. A pure image processing does not allow an automatic identification of individual structures, so that this must be done by the physician. To decrease the high expense of time, this report presents a concept for an adapted chain of rf-signal processing as well as an ultrasonic system for the contrast-enhanced representation of tissue borders. The system permits an exact measurement of the body geometry, which is demonstrated by determining the position of the pelvis entry plane.

[Ultrasound control of thermal tissue therapy]. / Ultraschall-Kontrolle Thermischer Tumor Therapien.

As alternatives to surgical resection and/or supportive to radio- or chemo-therapy of tumors and metastases minimal invasive interstitial thermal treatment procedures by which the tissue is heated up locally to temperatures up to 100 degrees C are used. However beside nuclear magnetic resonance tomography there is no economical, by routine applicable procedure for non invasive therapy control at present disposal. In this work the possibility of non invasive control of thermal therapies by means of temporal and spectral analysis of radio frequency ultrasound signals are evaluated. Two different ultrasonic procedures, the first beeing based on the analysis of local modifications in the time of flight of the ultrasound signal for determination of the temperature distribution in the tissue, the second beeing based on the physical attenuation characteristics of biological tissue and their dependence on the tissue structure are proposed and evaluated for therapy control. With in vitro experiments the possibilities and limitations of both procedures and preliminary results of a prototype control system are demonstrated.