MICS - Synthetic Aperture Imaging
- 1. Synthetic Aperture Imaging Medical Imaging Computing Systems Lab Department of Electronic Engineering Interdisciplinary Program of Integrated Biotechnology Medical Solutions Institute Sogang University, Seoul, Korea Medical Imaging Computing System1 Lab s
- 2. Contents Introduction Method – Synthetic aperture imaging techniques – Evaluation metrics Result and discussion – Phantom study – In vivo study Conclusion Further works Medical Imaging Computing Systems Lab
- 3. Introduction Transmit beam Receive beam Tx/Rx beam One way dynamic focusing Two way dynamic focusing Fixed Tx focusing / Dynamic Rx focusing Dynamic Tx and Rx focusing Synthetic aperture imaging Medical Imaging Computing Systems Lab
- 4. Introduction Conventional imaging SA imaging Transmit focusing Receive focusing Low resolution images ∑ ∑ Reconstructed image Low resolution image High resolution image Medical Imaging Computing Systems Lab
- 5. Method : Synthetic Aperture Imaging Technique Single element transmit Defocusing BiPBF SA with a virtual Single element transmit Defocusing source (BiPBF) No decrease of acoustic No decrease of acoustic Advantage - power power Number of synthesize Low signal to noise Need for adjusting transmit Disadvantage ratio(SNR) beamforming beams need to be adjusted depending on depth Medical Imaging Computing Systems Lab
- 6. Method : SA with a Virtual Source Synthetic aperture imaging technique with a virtual source element – Regard transmit focal point as a virtual source – Spherical waves are propagated back and forth from the virtual source – Tx delay : – Rx delay : Transmit wave-fronts model with Principle of transmit synthetic two virtual source located at each focusing transmit focal point with the virtual source Medical Imaging Computing Systems Lab
- 7. Method : Evaluation Metrics Medical Imaging Computing Systems Lab
- 8. Result and Discussion : Phantom Study B-mode phantom images Multi-zone transmit focusing Conventional SA (M=64) (MZTF) Multi-Purpose Multi-Tissue Ultrasound Phantom (Model 040GSE) © CIRS Medical Imaging Computing Systems Lab
- 9. Result and Discussion : Phantom Study 6-dB lateral resolutions – 6-dB lateral resolutions at each wire target – Conventional and MZTF methods • Best lateral resolution at the each transmit focal depth • Broadened as imaging distance from the focal depth was increased – SA method • Uniform lateral resolution Medical Imaging Computing Systems Lab
- 10. Result and Discussion : Phantom Study SNR – SNR along the depth obtained from three methods – Conventional and MZTF methods • The high SNR was achieved only at the focal depth – SA method • Mean SNR value was improved Medical Imaging Computing Systems Lab
- 11. Result and Discussion : Phantom Study CNR, SNR Conventional MZTF SA CNR 3.1 3.4 3.4 SNRmean 15.3 dB 16.7 dB 23.6 dB – Higher CNR value in SA method than conventional method • Reduced speckle size in the SA method due to the enhanced lateral resolution → higher CNR ROI of CNR – CNR value was the same in SA method and MZTF method • ROI for CNR measurement was located at one of transmit focal depth Medical Imaging Computing Systems Lab
- 12. Result and Discussion : Phantom Study Penetration depth Filtered intensities of echo and noise signal used for measuring the penetration depth Visible ROI of penetration depth The penetration depth along the number of sub-aperture (M) of SA method Medical Imaging Computing Systems Lab
- 13. Result and Discussion : In-vivo study In-vivo data acquisition set-up – Patients were scanned in supine position by an experienced radiologist – The patients with benign and malignant tumors – Two sets of RF data from each patient were acquired sequentially for the conventional and SA imaging – Focus point • Conventional : adaptive • SA imaging : 40 mm Common improvement – Conspicuity and margin sharpness of the lesion is improved – Higher contrast resolution – Increase of resolution in deep portion Medical Imaging Computing Systems Lab
- 14. Result and Discussion : In-vivo study B-mode in-vivo images – Malignant infiltration ductal carcinoma • Edge shadowing artifacts has been dramatically reduced in the SA image (white arrows) • Resolution in deeper portion has decreased (white dotted box) Medical Imaging Computing Systems Lab
- 15. Conclusion Assessed conventional and SA image – Quantitative evaluation • SA images provided higher CNR and SNR values • SA images provided uniform improvement in image resolution at all points (two-way dynamic focusing) • SA images provided better penetration depth – Qualitative evaluation • SA images provided higher lesion conspicuity and global preference – Consistent result with both in-vivo and in-vitro data Medical Imaging Computing Systems Lab