International Workshop on Medical Ultrasound Tomography

3D Ultrasound Tomography for Breast Cancer Diagnosis at KIT: an Overview

Nov 3, 2017, 9:50 AM

20m

Lecture Hall

Oral Main Track Session 8: Clinical applications I

Speaker

Nicole Ruiter (Karlsruhe Institute of Technology)

Description

3D USCT emitting and receiving spherical wave fronts overcomes the limitations of 2D systems by offering a nearly isotropic 3D point spread function, a large depth of field, less loss of out-of-plane reflections and fast 3D data acquisition. Yet 3D devices for clinical practice require a more complex hard- and software due to the huge data rate, time-consuming image reconstruction, and large number of small transducers. The here reviewed KIT 3D USCT is a 3D prototype for clinical studies.

(2) Material and Methods

The KIT 3D USCT device is equipped with 2041 transducers on a semi elliptical aperture with 2.5 MHz center frequency and 50% bandwidth. The data acquisition is carried out by sequentially sending a frequency coded chirp with a single emitter and recording with all receivers. Rotational and translational movement of the aperture is applied. Up to 80 GB of raw data is digitized with 480 parallel channels at 12 Bit and 20 MHz sampling frequency. 3D synthetic aperture focusing technique (SAFT) is applied for reflectivity reconstruction. Sound speed and attenuation volumes are created using a straight ray based algebraic reconstruction technique. Parallel reconstruction on GPUs enables high resolution breast volumes in 16 minutes.

(3) Results

The point spread function for reflectivity imaging could be shown to be nearly isotropic in 3D and to have very low spatial variability (0.24 mm ± 0.05 mm). In a first pilot study ten patients with different lesions were imaged. Data acquisition could be carried out for all patients with an average imaging time of six minutes per breast. Speed of sound, attenuation and reflectivity volumes of each patient were derived from the raw data. Overlaid volumes of the modalities show qualitative and quantitative information at a glance. The results are promising as the breasts’ tissue structures and cancerous lesions could be identified in the USCT images. A larger clinical study with 200 patients was started.

(4) Discussion and Conclusion

We realized a sparse 3D USCT setup, resulting in homogeneous illumination, and nearly isotropic 3D PSF and applied it successfully in clinical studies. In the preliminary clinical results speed of sound was the most indicating modality for breast cancer. Yet, the spatial resolution of speed of sound and attenuation is currently limited by the ray based reconstruction algorithm. More complex reconstruction methods for transmission tomography leading to higher resolution are under test.