Portable 3D/4D Ultrasound Diagnostic Imaging System

The rapid diagnosis of invisible internal injury in an austere and hostile front-line operational environment remains a challenge for (Canadian Forces) medical and search and rescue personnel. The availability of a portable 4D-ultrasound imaging system with a single probe, providing high image resolution and deep penetration, is considered by (civilian) medical practitioners and their military health services counterparts as exceedingly helpful, if not essential in supporting triage and medical decisions to save lives. However, portable and easy-to-use 4D non-invasive medical imaging systems are not yet commercially available, primarily because of unresolved major technological and engineering challenges. Available portable ultrasound systems only provide 2D images, requiring a medical professional to mentally integrate multiple images to develop a 3D impression of the scanned objects. This practice is time-consuming, inefficient, and requires a highly skilled operator to administer the scanning procedure. Defence R&D Canada (DRDC) is developing a Portable 3D/4D Ultrasound Diagnostic Imaging System (PUDIS) to address the abovementioned challenges. Our proposed approach to address the conventional 2D ultrasound imaging limitations is to implement 3D adaptive beamformers in portable 4D ultrasound imaging systems, that can improve image resolution for low frequency planar array probes. Along these lines, DRDC has allocated significant investments to develop an advanced, fully-digital 4D (3D-spatial + 1D-temporal) ultrasound imaging technology for improving image resolution and facilitating auto-diagnostic applications to detect non-visible internal injuries, based on the volumetric imaging outputs provided by a 4D ultrasound imaging system that includes: • A 32x32 sensor planar array ultrasound probe with a fully digital data acquisition peripheral; • A portable ultrasound computing architecture consisting of a cluster of DSPs and CPUs; • Adaptive 3D beamforming algorithms with volumetric visualization, including fusion and automated segmentation capabilities; and • The implementation of a decision-support process to provide automated diagnostic capabilities for non-invasively detecting internal injuries and facilitate image guided surgery. 1.0 INTRODUCTION The fully digital 3-Dimensional (3D)/ (4D: 3D + time) Ultrasound System Technology, presented in this paper, consists of a set of adaptive ultrasound beamformers [1-4] that have been discussed in detail in [3,6]. The aim with this signal processing structure is to address the fundamental image resolution problems of current ultrasound systems [6-8] and to provide suggestions for its implementation into existing 2D and/or 3D ultrasound systems as well as develop a complete stand-alone 3D ultrasound solution. This development has Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE APR 2010 2. REPORT TYPE N/A 3. DATES COVERED 4. TITLE AND SUBTITLE Portable 3D/4D Ultrasound Diagnostic Imaging System 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Defence R&D Canada Toronto 1133 Sheppard Ave West, P.O. Box 2000 Toronto, Ontario M3K 2C9 CANADA 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release, distribution unlimited 13. SUPPLEMENTARY NOTES See also ADA564622. Use of Advanced Technologies and New Procedures in Medical Field Operations (Utilisation de technologies avancees et de procedures nouvelles dans les operations sanitaires). RTO-MP-HFM-182 14. ABSTRACT The rapid diagnosis of invisible internal injury in an austere and hostile front-line operational environment remains a challenge for (Canadian Forces) medical and search and rescue personnel. The availability of a portable 4D-ultrasound imaging system with a single probe, providing high image resolution and deep penetration, is considered by (civilian) medical practitioners and their military health services counterparts as exceedingly helpful, if not essential in supporting triage and medical decisions to save lives. However, portable and easy-to-use 4D non-invasive medical imaging systems are not yet commercially available, primarily because of unresolved major technological and engineering challenges. Available portable ultrasound systems only provide 2D images, requiring a medical professional to mentally integrate multiple images to develop a 3D impression of the scanned objects. This practice is time-consuming, inefficient, and requires a highly skilled operator to administer the scanning procedure. Defence R&D Canada (DRDC) is developing a Portable 3D/4D Ultrasound Diagnostic Imaging System (PUDIS) to address the above-mentioned challenges. Our proposed approach to address the conventional 2D ultrasound imaging limitations is to implement 3D adaptive beamformers in portable 4D ultrasound imaging systems, that can improve image resolution for low frequency planar array probes. Along these lines, DRDC has allocated significant investments to develop an advanced, fully-digital 4D (3D-spatial + 1D-temporal) ultrasound imaging technology for improving image resolution and facilitating auto-diagnostic applications to detect non-visible internal injuries, based on the volumetric imaging outputs provided by a 4D ultrasound imaging system that includes: A 32x32 sensor planar array ultrasound probe with a fully digital data acquisition peripheral; A portable ultrasound computing architecture consisting of a cluster of DSPs and CPUs; Adaptive 3D beamforming algorithms with volumetric visualization, including fusion and automated segmentation capabilities; and The implementation of a decision-support process to provide automated diagnostic capabilities for non-invasively detecting internal injuries and facilitate image guided surgery. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18. NUMBER OF PAGES 22 19a. NAME OF RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Portable 3D/4D Ultrasound Diagnostic Imaging System 27 2 RTO-MP-HFM-182 received grant support from the Defence R&D Canada (DRDC) and from the European Commission IST Program (i.e. ADUMS project: EC-IST-2001-34088). To fully exploit the advantages of the present fully digital adaptive ultrasound technology, its implementation in a commercial ultrasound system requires that the system has a fully digital design configuration consisting of A/DC and D/AC peripherals that have the capability to digitize the ultrasound probe time series, to optimally shape the transmitted ultrasound pulses through a D/A peripheral and to integrate linear and/or planar phase array ultrasound probes. Thus, the digital ultrasound 3D beamforming technology of this paper, can replace the conventional (i.e. time delay) beamforming structure of ultrasound systems with an adaptive beamforming processing configuration. The results of this development [1,2,6] demonstrate that adaptive beamformers improve significantly (at very low cost) the image resolution capabilities of an ultrasound imaging system by providing a performance improvement equivalent to a deployed ultrasound probe with double aperture size . Furthermore, the portability and the low cost characteristics of the present 3D adaptive ultrasound technology can offer the options to medical practitioners and family physicians to have access of diagnostic imaging systems readily available on a daily basis. As a result, a digital PC-based ultrasound technology can adjust the signal processing configuration of ultrasound devices to move them away from the traditional hardware and implementation software requirements and to be able to accommodate the processing requirements of the "traditional" linear array 2D scans as well as the advanced matrix-arrays performing volumetric scans. In summary, a digital PC-based ultrasound imaging technology can provide flexible cost-to-image quality adjustments. The resulting systems can be upgraded on a continuous base at very low cost by means of software and hardware improvements by exploiting the continuous upgrades and CPU performance improvements of the PC architectures. Thus, to maintain a reasonable image quality, a large number of detector elements are required, and the computational load is directly related to the size of 2-D array (i.e. planar array ultrasound probe) used to acquire the RF time series for beamforming. The ability to image volumes, instead of slices is the motivation for using a 3-D beamformer. Currently to generate an ultrasound volume, a number of slices are collected. These slices are then used to synthesize a 3D volume. Another approach is to use 2-D array probes to generate 3D ultrasound volumes, but to counter the increased processing load brought on by the 2-D probe the resolution in one of the directions (x or y) is compromised. As stated above, the core of the system design presented here is the efficient implementation of 3D beamforming that greatly simplifies the beamformer processing. This implementation makes it possible to map the processing onto a parallel computing architecture like the multi-node cluster described later. The beamforming algorithm is implemented on the processing cluster along with a versatile data control unit that controls all signal transmission and reception form the complete 3D/4D Ultrasound system. An additional complication is that in ultrasound imaging systems the angular resolution provided by conventional beamformers is determined by the length of the aperture L, and by the frequency of the received signals [1,2,6]. Since the operating frequency is usually fixed, only the aperture length can be eventually increased by a higher number of elements, thus leading to more complex hardware and software implementations. The alternative is to employ an adaptive beamforming method. Adaptive beamformers are designed to maximize signal detection, while minimizing the beam-width, and suppressing the side-lobes Portable 3D/4D Ultrasound Diagnostic Imaging System RTO-MP-HFM-182 27 3 [1,2,3]. The convergence time of the specific method adopted allows for real-time imaging [6]. The method uses a combination of the Sub-Aperture pre-processing scheme [4] and a space-time statistic [3,4] to reduce the degrees of freedom required by the algorithm. 2.0 THE BEAMFORMING PROCESS IN 3D/4D ULTRASOUND SYSTEMS 2.1 Conventional 3D Beamformer Consider the beamforming process for an N x M detector array with K time samples collected, the data collected is given by K k M m N n t x k nm    1 , 1 , , 1 ), (    . (1) The time domain focused beamformer outputs implemented in the frequency domain, the beam-time series obtained from the beamformer,   ) , , , ( ) , , , ( R B A f B IFFT R B A t b i j  , is given by (2), where the parameters are defined in Figure 1.