KEYWORDS: 3D modeling, Bone, Image segmentation, Signal attenuation, Acoustic waves, Tissues, Data modeling, Voxels, 3D image processing, Wave propagation, 3D image reconstruction, Ultrasound tomography, Ultrasound transmission tomography, Breast cancer
Evidence for Biot slow wave data in 3D ultrasound tomographic (3D UT) data from an orthopedic scan is shown by segmentation interior to Bone. Previous results have shown the quantitative accuracy of the 3D ultrasound volography method for ligaments, cartilage, tendons, skin, fat, muscle, etc. Interior to bone the SOS values are lower than expected. It is known that a slow compressional wave is predicted by Johnson-Biot theory which has speed of sound (SOS) values independently measured which are similar to our values based on segmentation for trabecular bone matrix interior to bone. Values for marrow are determined from segmentation and are commensurate with literature values as well. Concepts from algebraic topology are applied to the tomographic data (the first homotopy group of the N-torus, where N is the number of receiver elements in the array) and a quantitative comparison of the data redundancy with 2D algorithms is carried out. The use of algebraic topology gives a suitable context in which to understand phase unwrapping issues and leads to constraints on the distance between the data acquisition (DA) data levels and the frequencies used in the reconstruction. The data redundancy comparison applies to any 3D vs 2D comparison, e.g. 3D UT compared with MRI and shows the much larger size of the information contributing to a single voxel in the 3D vs 2D as long as the 3D model for wave propagation is used. The implications of this are discussed. Validation of attenuation variation with frequency is shown.
In this work, we introduce the first realistic digital phantoms for prostate ultrasound and photoacoustic (PA) imaging in the male pelvic region. Our model encompasses surrounding tissues or organs around the prostate, including fat, bones (including femoral heads), muscles, urinary bladder, rectum, anal canal, penile bulb, neurovascular bundles, and seminal vesicles. Each digital phantom set contains five parameters: speed of sound, density, acoustic attenuation, optical absorption, and reduced optical scattering. The anatomical structures were derived from open-source computed tomography (CT) and magnetic resonance imaging (MRI) data from the Gold Atlas Project. The acoustic parameters, including the speed of sound and attenuation of the prostate, were obtained from an ex vivo prostate study utilizing the QTscan ultrasound tomography (UST) platform at the National Institutes of Health. All other parameters were acquired from the literature. By employing atlas data from four pelvises and UST images of 62 ex vivo prostate specimens, we generated 248 sets of digital phantoms. Additionally, we demonstrate a practical application, showcasing the identification of the effective insonification window for prostate UST. The developed digital phantoms are made open source and can be found at https://github.com/ywu115/Prostate-digital-phantoms. They can be leveraged for imaging device design, image formation studies, image reconstruction validation, and diagnostic and treatment planning for numerous prostate studies using ultrasound and PA imaging. Since the digital phantoms cover the entire male pelvic region, they can potentially be extended to other applications, such as bladder cancer imaging, cyst detection in seminal vesicles, hernias, and treatment planning for point-of-care ultrasound.
Prostate ultrasound imaging has utilized B-mode, however recent success in 3D ultrasound tomography (3D-UT) in the presence of bone, indicate using it to augment other potentially harmful or expensive modalities in clinic. Several fresh whole prostates were excised/inserted into bespoke polyacrylamide gel phantoms within 30 minutes of prostatectomy and scanned in the QT imaging scanner. The speed of sound (SOS) map resulting from the 3D-UT was used to create the refraction corrected reflection image compounded over 360 degrees resulting in sub-mm resolution. Several lesions were correlated with rigid transformations via anatomic landmarks with clinical MRI and H&E stained whole sections by experts in MRI and whole sectioning. Lesions were pointed out all 3 modalities and compared for multiple lesions indicating proof of concept of unique visibility of prostate lesions in 3D-UT (also volography) ex-vivo.
3D ultrasound tomography (3D-UT, or volography) gives heretofore unavailable resolution and accuracy in the 3D measurement of fibroglandular tissue in breast. The correct segmentation of the fibroglandular tissue requires an accurate high resolution speed of sound map which 3D UT (volography) produces and a robust segmentation algorithm. Our threshold based and Fuzzy C-means based algorithms have been compared and validated visually and with phantoms, and we show the effect of a row/column of dropouts on our reconstructions is minimal and indicate a variation of the volume of fibroglandular tissue in a variety of physiological situations for a select set of cases out of a larger 48 case cohort. We isolate glandular from ductal and structural tissue.
Mammographic quantitative breast density (QBD), the ratio of fibroglandular tissue to whole breast volume, is known to be important for risk assessment for breast cancer. Most methods are based on 2D projections, though some use MRI. We show two methods for determining QBD from 3D ultrasound tomographic (UT) images, their equivalence and superiority over other methods of estimation. False assignments to breast density can occur if projection methods are used. A sigmoidal function is fit using a log likelihood maximization and the QBD from MRI images is compared with QBD as calculated from 3D UT showing strong correlation.
3D inverse scattering ultrasound tomography (3D UT) is quantitative and not subject to artifacts from 2D algorithms and data and does not require contrast agents or ionizing radiation. However, it is time consuming, so it is important to have timing results for 3D inverse scattering reconstructions of the whole breast with 3D algorithms and full 3D data and in the clinically relevant context of a diverse population of dense, heterogeneously dense and fatty breasts. The adaptive algorithm uses different reconstruction frequencies and iteration counts for different breasts. We compare a computational complexity count with the observed fit of reconstruction times vs breast size that and show performance comparable to published TFLOP performance for nVidia cards. We show a reconstruction time of 24 minutes for an average size breast and show substantial speed up with more efficient nVidia cards. These numbers indicate clinical viability for 3D transmission ultrasound even in the clinical setting with diverse demographics in low income areas. The cohort of 23 cases of different types of breasts were reconstructed on two P6000's and compared with the same data reconstructed on two RTX6000's with 24GB on-board memory and some optimization of the CUDA code. The resulting speed up is better than linear with increasing computation time, indicating increasing efficiency with computational complexity, larger breasts. Image quality is also affected, since increasing iteration and frequency counts give generally better images as long as overconvergence is avoided. These results further validate the 3D Quantitative UT as clinically viable, especially for underserved populations.
Muscular Dystrophy (Duchenne) and osteoarthritis are important diseases requiring quantitative tissue measurement for accurate monitoring. MRI with Dixon Sequences, Nakagami statistics, elastography and radiography have been used in semi-quantitative modes to infer myopathy, articular cartilage damage, and exercise induced muscle damage. We establish the high resolution quantitative accuracy of transmission ultrasound imaging using both fresh and cadaver knee tissue. The use of fresh tissue obviates the possibility that cadaverous tissue has different speed of sound (SOS) values due to fixation. We show also that the fixation procedure changes the SOS values by about 0.1% to 0.4% fibroglandular tissue, fat and skin. The use of multiple transverse sections at varying distances from the tibiofemoral space ameliorates bias. Using a 6 mm diameter ROI at 20 successive levels, the SOS measured for the Vastus medialis was 1573 m/s with a 95% CI of +/-1.8 m/s. The average standard deviation (SD) for the ROI’s altogether was 25.9 m/s. The accepted SOS value for muscle from the IT’IS Foundation, Zurich, is 1588.4, SD = 21.6 m/s. Similar results for 6 mm diameter ROI’s in fat at successive transverse sections yields an average of 1438.7 m/s, the ROI SD’s averaged 20.5 m/s. The IT’IS values are 1440 m/s with SD 21.4 m/s. Cartilage gives similar agreement: literature value is 1660 m/s, and we measure 1655.4 m/s (SD 14.6) in 4 mm diameter ROI. We show regions that have no MR response yet are quantitatively imaged in 3D transmission ultrasound.
The ability to conduct ‘partial field of view’ scans in QT ultrasound transmission ultrasound is investigated. The standard tomographic data acquisition is typically conducted in a full 360 degree aperture, which may limit the possibility of real time intervention and/or patient positioning for medical imaging. Transmission ultrasound has many advantages over other imaging modalities such as, it does not emit ionizing radiation, does not require contrast agent, etc. A partial field of view data acquisition in this context is therefore attractive. Three scenarios are investigated: breast, whole body, and orthopedic imaging. A full suite of 180 views at 2 degree intervals and 192 mm in the vertical direction was collected from the QT ultrasound™ scanner in the orthopedic and whole body scenarios. The vertical extent of the breast image varied with breast size. Subsequent reconstructions were carried out with a subset of the views incorporated. The contiguous sector of missing angles varied from 8, 16, 32, 40, 60 and 92 degrees. The difference between the corresponding images was quantitatively and qualitatively analyzed and compared. It was found that a large lacuna (gap) of contiguous data did not significantly (clinically) degrade image quality, and the quantitative values, where relevant. The open acquisition scenario allows us to carry out medical intervention as well as potentially decrease patient anxiety. The quantitative nature of the degradation is noted and correlated with the missing sector angles for clinical scenarios, and the implications discussed.
There is a need to provide better imaging methods for infants as there are few good options. CT can provide reasonable image quality with limited soft tissue contrast at a cost of large radiation dose. MRI can provide better soft tissue contrast, but the small size of an infant produces poor signal to noise and thus long scan times. Both types require anesthesia, which carries a substantial mortality risk for young patients and especially sick ones. Ultrasound imaging has been principally relegated to relatively simple applications in in orthopedics and diagnostics due to the inability to achieve high resolution at depth in complex structures. Quantitative Transmission (QT) Ultrasound relies on low frequency information which has greater penetrating power and 3D Inverse Scattering to produce high resolution and contrast at substantial depth. We built a prototype device for imaging small animals and tested the performance on 7-10lb piglets to simulate the conditions necessary to scan a newborn infant human. Image acquisition was entirely conventional with the currently available QT ultrasound breast imagers, but reconstruction required significant modification to deal with the additional complexity. We report on the changes in methods as well as the preliminary performance of the system in this configuration.
The challenge of ultrasound tomography in the presence of high impedance contrast is well known. We have successfully used full 3D transmission inverse scattering and refraction corrected reflection tomography to create 3D high-resolution images of the human breast. However, these tissues do not encompass the high contrast that occurs in orthopaedics scenarios, such as the human knee, where cranial and trabecular bone are present. Even though the high contrast of the bone is problematic for model based iterative reconstruction methods, we successfully image the tissue near, and in, the Femur-Tibia (F-T) space using an adapted QT Ultrasound Scanner and adapted inverse scattering algorithm.
We show preliminary reconstructions of a cadaver knee that indicates that we can quantitatively and accurately image proximal soft tissue structures. We give correlations between MR images and QT Ultrasound transmission images that show correlation with known structures: besides the femur, tibia, and fibula, we see the condyle structures (medial and lateral), medial and lateral menisci internal to the F-T space, collateral ligaments, infrapatellar fat pad (Hoffa’s pad), patellar ligament, and various ligaments, tendons and musculature in the leg above and below the knee.
We establish that a substantially different reconstruction protocol (than that of the breast) for 3D inverse scattering is required to obtain these images and we discuss the implications of these changes. These preliminary results show that high resolution of clinically relevant tissue is feasible with ultrasound tomography even within the F-T space.
KEYWORDS: Breast imaging, Reconstruction algorithms, 3D image processing, Ultrasound tomography, Inverse scattering, Ultrasonography, Image resolution, 3D metrology, Spatial resolution, Breast
There has been a great deal of research into ultrasound tomography for breast imaging over the past 35 years. Few successful attempts have been made to reconstruct high-resolution images using transmission ultrasound. To this end, advances have been made in 2D and 3D algorithms that utilize either time of arrival or full wave data to reconstruct images with high spatial and contrast resolution suitable for clinical interpretation. The highest resolution and quantitative accuracy result from inverse scattering applied to full wave data in 3D. However, this has been prohibitively computationally expensive, meaning that full inverse scattering ultrasound tomography has not been considered clinically viable. Here we show the results of applying a nonlinear inverse scattering algorithm to 3D data in a clinically useful time frame. This method yields Quantitative Transmission (QT) ultrasound images with high spatial and contrast resolution. We reconstruct sound speeds for various 2D and 3D phantoms and verify these values with independent measurements. The data are fully 3D as is the reconstruction algorithm, with no 2D approximations. We show that 2D reconstruction algorithms can introduce artifacts into the QT breast image which are avoided by using a full 3D algorithm and data. We show high resolution gross and microscopic anatomic correlations comparing cadaveric breast QT images with MRI to establish imaging capability and accuracy. Finally, we show reconstructions of data from volunteers, as well as an objective visual grading analysis to confirm clinical imaging capability and accuracy.
KEYWORDS: Breast, Signal attenuation, Ultrasonography, Mammography, Tissues, Refraction, Magnetic resonance imaging, Water, Nipple, Algorithm development
Reflection ultrasound (US) has been utilized as an adjunct imaging modality for over 30 years. TechniScan, Inc. has
developed unique, transmission and concomitant reflection algorithms which are used to reconstruct images from data
gathered during a tomographic breast scanning process called Warm Bath Ultrasound (WBU™). The transmission
algorithm yields high resolution, 3D, attenuation and speed of sound (SOS) images. The reflection algorithm is based
on canonical ray tracing utilizing refraction correction via the SOS and attenuation reconstructions. The refraction
correction reflection algorithm allows 360 degree compounding resulting in the reflection image. The requisite data are
collected when scanning the entire breast in a 33° C water bath, on average in 8 minutes. This presentation explains how
the data are collected and processed by the 3D transmission and reflection imaging mode algorithms. The processing is
carried out using two NVIDIA® Tesla™ GPU processors, accessing data on a 4-TeraByte RAID. The WBU™ images are
displayed in a DICOM viewer that allows registration of all three modalities. Several representative cases are presented
to demonstrate potential diagnostic capability including: a cyst, fibroadenoma, and a carcinoma. WBU™ images (SOS,
attenuation, and reflection modalities) are shown along with their respective mammograms and standard ultrasound images. In addition, anatomical studies are shown comparing WBU™ images and MRI images of a cadaver breast. This innovative technology is designed to provide additional tools in the armamentarium for diagnosis of breast disease.
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