Partial Volume Compensated Reconstruction of Three-dimensional Mass Shapes in Mammographic Images

Accurately reconstructing the three-dimensional mass shapes in mammographic images is important for classifying the abnormality into malignant or benign. In this paper, a partial volume compensated reconstruction technique for mass shapes is presented. The two-dimensional shapes of the masses are first automatically segmented using a region growing approach. The 3D mass shapes are then iteratively refined according to an algebraic reconstruction technique. Partial volume estimation is applied on the boundary to get a smoother 3D shape. Evaluation results show that the proposed algorithm improves the accuracy of the mass reconstruction

The Role Of Tissue Sound Speed As A Surrogate Marker Of Breast Density

Breast density is one of the strongest predictors of breast cancer risk as women with the densest breasts have a three- to five-fold increase in risk compared to women with the least dense breasts. Breast density is currently measured by using mammography, the current gold standard for breast imaging. There are many shortcomings to using mammography to measure breast density, including the use of ionizing radiation. Ultrasound tomography (UST) does not use ionizing radiation and can create tomographic breast sound speed images. These sound speed images are useful because breast density is proportional to sound speed. The purpose of this work was to assess the ability of UST to measure breast density and its ability to measure changes in breast density over short periods of time. A cohort of 251 patients was examined using both UST and mammography. Many different associations were found between the UST density measurement, the volume averaged sound speed, and the mammographic percent density. Additional associations were found between many other UST and mammographic imaging characteristics. UST density was found to correlate with various patient characteristics in a similar manner to mammographic density. Additionally, UST was used to examine the effects of tamoxifen on breast density. Tamoxifen has been shown to reduce mammographic density and breast cancer risk for some women. Preliminary data for 52 patients has shown promising results so far. UST density has decreased for approximately a similar percentage of patients as has been measured for mammographic density. These changes have been measured over short time frames that could not be achieved using mammography. These results show that UST\u27s ability to measure breast density is consistent with mammography, the current standard of care. UST has the potential to become a safe and effective device that can be used to reliably assess breast density and serial changes in breast density

2D AND 3D breast elastography with a combined ultrasound/digital tomosynthesis mammography system

Ultrasound elastography is a novel imaging method which acts as a surrogate to manual palpation to evaluate elastic properties of tissue. In this dissertation, elastography was conducted through a mammographic paddle in conjunction with a combined ultrasound/digital tomosynthesis mammography system to improve breast lesion characterization. Imaging through a mammographic paddle may adversely affect ultrasound image quality by reducing spatial resolution, increasing attenuation, and decreasing contrast. Thus, appropriate paddle choice is essential to create high quality through-paddle ultrasound images and strain images. Sonographic image quality through mammographic paddles of varying materials and thicknesses was compared with direct-contact (no paddle) image quality. TPX plastic paddles ≤ 2.5 mm thick performed best; when employed in vivo, 83% of cases produced image quality as good or better than their direct-contact analogues. Through-paddle 2D elastography was conducted through the best paddle using a 1D ultrasound transducer at 7.5 MHz and performance was compared with freehand elastography. For small strain step sizes (< 0.5%), through-paddle elastography produced correlation coefficients and strain SNR comparable to freehand elastography. Ultimately, the aim of elastography is to acquire high quality strain estimates in 3D to fully characterize tissue. Thus, data acquisition techniques were extended to a small 3D volume. Compared with its 2D analogue, 3D elastography created higher correlation coefficients for strain step sizes ≥ 1% and at least 35% improvement in strain SNR for all step sizes. These early successes indicate that through-paddle elastography can create high quality elastograms which might aid in breast lesion characterization. Next, through-paddle elastography was performed in 20 human subjects with varying breast masses. This dissertation introduced the elasticity characteristic “differential correlation coefficient,” which exploits the severe decorrelation observed in cysts under compression to differentiate cystic and solid masses. When applied in a clinical setting, this characteristic demonstrated potential to reduce the malignancy rating of a complicated cyst, changing management options from biopsy to imaging follow-up. Additional elastographic appearances of breast masses were evaluated, including lesion size, stiffness, margin regularity, and boundary flow. These studies suggest that elastography has potential to improve characterization of breast masses beyond x-ray tomography and sonography alone.NIH RO1-CA91713 and R21- CA109440http://deepblue.lib.umich.edu/bitstream/2027.42/107472/1/Booi_dissertation_FINAL.pdf-1Description of Booi_dissertation_FINAL.pdf : R.C. Booi, Ph.D. Thesi

Proceedings Virtual Imaging Trials in Medicine 2024

This submission comprises the proceedings of the 1st Virtual Imaging Trials in Medicine conference, organized by Duke University on April 22-24, 2024. The listed authors serve as the program directors for this conference. The VITM conference is a pioneering summit uniting experts from academia, industry and government in the fields of medical imaging and therapy to explore the transformative potential of in silico virtual trials and digital twins in revolutionizing healthcare. The proceedings are categorized by the respective days of the conference: Monday presentations, Tuesday presentations, Wednesday presentations, followed by the abstracts for the posters presented on Monday and Tuesday

Innovative Acoustic Reflection Imaging Techniques And Application To Clinical Breast Tomography

Conventional ultrasound techniques use beam-formed, constant sound speed ray models for fast image reconstruction. However, these techniques are inadequate for the emerging new field of ultrasound tomography (UST). We present a new technique for reconstruction of reflection images from UST data. We have extended the planar Kirchhoff migration method used in geophysics, and combined it with sound speed and attenuation data obtained from the transmission signals to create reflection ultrasound images that are corrected for refractive and attenuative effects. The resulting techniques were applied to simulated numerical phantom data, physical phantom data and in-vivo breast data obtained with an experimental ring transducer prototype. Additionally, the ring transducer was customized to test compatibility with an existing ultrasound workstation. We were able to obtain independently recorded radio-frequency (RF) data for individual transmit-receive pair combinations for all 128 transducers. The signal data was then successfully reconstructed into reflection data using the Kirchhoff migration techniques. The results from the use of sound speed and attenuation corrections lead to significant improvements in image quality, particularly in dense tissues where the refractive and scattering effects are the greatest. The procedure was applied to a variety of breast densities and masses of different natures. The resulting reflection images successfully resolved boundaries and textures. The reflection characteristics of tomographic ultrasound maintain an indispensible position in the quantification of proper mass identification. The results of this project indicate the clinical significance of the invocation of properly compensated Kirchhoff based reconstruction method with the use of sound speed and attenuation parameters for the visualization and classification of masses and tissue

Innovative Acoustic Reflection Imaging Techniques And Application To Clinical Breast Tomography

Conventional ultrasound techniques use beam-formed, constant sound speed ray models for fast image reconstruction. However, these techniques are inadequate for the emerging new field of ultrasound tomography (UST). We present a new technique for reconstruction of reflection images from UST data. We have extended the planar Kirchhoff migration method used in geophysics, and combined it with sound speed and attenuation data obtained from the transmission signals to create reflection ultrasound images that are corrected for refractive and attenuative effects. The resulting techniques were applied to simulated numerical phantom data, physical phantom data and in-vivo breast data obtained with an experimental ring transducer prototype. Additionally, the ring transducer was customized to test compatibility with an existing ultrasound workstation. We were able to obtain independently recorded radio-frequency (RF) data for individual transmit-receive pair combinations for all 128 transducers. The signal data was then successfully reconstructed into reflection data using the Kirchhoff migration techniques. The results from the use of sound speed and attenuation corrections lead to significant improvements in image quality, particularly in dense tissues where the refractive and scattering effects are the greatest. The procedure was applied to a variety of breast densities and masses of different natures. The resulting reflection images successfully resolved boundaries and textures. The reflection characteristics of tomographic ultrasound maintain an indispensible position in the quantification of proper mass identification. The results of this project indicate the clinical significance of the invocation of properly compensated Kirchhoff based reconstruction method with the use of sound speed and attenuation parameters for the visualization and classification of masses and tissue

Expansion of the 4D XCAT Phantom Library with Anatomical Texture

<p>Computational phantoms are set to play an important role in imaging research. As medicine moves increasingly towards providing individualized, patient-specific care, it is imperative that simulations be completed on patient-specific anatomy, rather than a reference standard. To that end, there is need for a variety of realistic phantoms for clinical studies.</p><p> This work adds to the existing extended cardiac and torso (XCAT) adult phantom series (two phantoms based on visual human data) by building new models based on adult patient computed tomography (CT) image data. These CT datasets were obtained from Duke University's patient CT database. </p><p>Each image-set was segmented using in-house segmentation software, defining bony structures and large organs within the field of view. 3D non-uniform rational b-spline (NURBS) surfaces were fitted to the segmented data. Using the multi-channel large diffeomorphic deformation metric mapping (MC-LDDMM) network, a transform was calculated to morph an existing XCAT model to the segmented patient geometry. Fifty-eight adult XCAT models were added to the phantom library. </p><p>In addition to the expanding the XCAT library, the feasibility of incorporating texture was investigated. Currently, the XCAT phantom structures are assumed to be homogeneous. This can lead to unrealistic appearance when the phantoms are combined with imaging simulations, particularly in CT. The purpose of this project was to capture anatomical texture and test it in a simulated phantom. Image data from the aforementioned patient CT database served as the source of anatomical texture. </p><p>The images were de-noised using anisotropic diffusion. Next, several regions of interest (ROIs) were taken from the liver and lungs of CT images. Using the ROIs as a source of texture, a larger stochastic texture image-set was created using the Image Quilting algorithm. </p><p>The visual human adult male XCAT phantom was voxelized at the same resolution as the texture image. The voxels inside the liver were directly replaced by the corresponding voxels of texture. Similarly for the lung, the voxels between the existing lung bronchi/blood vessels and the lung wall were replaced by texture voxels. This procedure was performed using ten different patient CT image-sets as sources of texture. </p><p>To validate the similarity of the artificial textures to the source textures, reconstructions of the adult male XCAT phantom with added textures were compared to the clinical images via receiver operator characteristic (ROC) analysis, a two-sample t-test, equivalence test, and through comparing absolute differences between scores. </p><p>It was concluded that this framework provides a valuable tool in which anatomical texture can be incorporated into computational phantoms. It is anticipated that this step towards making many anatomically variable virtual models indicative of a patient populace and making these models more realistic will be useful in medical imaging research, especially for studies relating to image quality.</p>Thesi

Developments in PET-MRI for Radiotherapy Planning Applications

The hybridization of magnetic resonance imaging (MRI) and positron emission tomography (PET) provides the benefit of soft-tissue contrast and specific molecular information in a simultaneous acquisition. The applications of PET-MRI in radiotherapy are only starting to be realised. However, quantitative accuracy of PET relies on accurate attenuation correction (AC) of, not only the patient anatomy but also MRI hardware and current methods, which are prone to artefacts caused by dense materials. Quantitative accuracy of PET also relies on full characterization of patient motion during the scan. The simultaneity of PET-MRI makes it especially suited for motion correction. However, quality assurance (QA) procedures for such corrections are lacking. Therefore, a dynamic phantom that is PET and MR compatible is required. Additionally, respiratory motion characterization is needed for conformal radiotherapy of lung. 4D-CT can provide 3D motion characterization but suffers from poor soft-tissue contrast. In this thesis, I examine these problems, and present solutions in the form of improved MR-hardware AC techniques, a PET/MRI/CT-compatible tumour respiratory motion phantom for QA measurements, and a retrospective 4D-PET-MRI technique to characterise respiratory motion. Chapter 2 presents two techniques to improve upon current AC methods that use a standard helical CT scan for MRI hardware in PET-MRI. One technique uses a dual-energy computed tomography (DECT) scan to construct virtual monoenergetic image volumes and the other uses a tomotherapy linear accelerator to create CT images at megavoltage energies (1.0 MV) of the RF coil. The DECT-based technique reduced artefacts in the images translating to improved μ-maps. The MVCT-based technique provided further improvements in artefact reduction, resulting in artefact free μ-maps. This led to more AC of the breast coil. In chapter 3, I present a PET-MR-CT motion phantom for QA of motion-correction protocols. This phantom is used to evaluate a clinically available real-time dynamic MR images and a respiratory-triggered PET-MRI protocol. The results show the protocol to perform well under motion conditions. Additionally, the phantom provided a good model for performing QA of respiratory-triggered PET-MRI. Chapter 4 presents a 4D-PET/MRI technique, using MR sequences and PET acquisition methods currently available on hybrid PET/MRI systems. This technique is validated using the motion phantom presented in chapter 3 with three motion profiles. I conclude that our 4D-PET-MRI technique provides information to characterise tumour respiratory motion while using a clinically available pulse sequence and PET acquisition method

Preoperative Systems for Computer Aided Diagnosis based on Image Registration: Applications to Breast Cancer and Atherosclerosis

Computer Aided Diagnosis (CAD) systems assist clinicians including radiologists and cardiologists to detect abnormalities and highlight conspicuous possible disease. Implementing a pre-operative CAD system contains a framework that accepts related technical as well as clinical parameters as input by analyzing the predefined method and demonstrates the prospective output. In this work we developed the Computer Aided Diagnostic System for biomedical imaging analysis of two applications on Breast Cancer and Atherosclerosis. The aim of the first CAD application is to optimize the registration strategy specifically for Breast Dynamic Infrared Imaging and to make it user-independent. Base on the fact that automated motion reduction in dynamic infrared imaging is on demand in clinical applications, since movement disarranges time-temperature series of each pixel, thus originating thermal artifacts that might bias the clinical decision. All previously proposed registration methods are feature based algorithms requiring manual intervention. We implemented and evaluated 3 different 3D time-series registration methods: 1. Linear affine, 2. Non-linear Bspline, 3. Demons applied to 12 datasets of healthy breast thermal images. The results are evaluated through normalized mutual information with average values of 0.70±0.03, 0.74±0.03 and 0.81±0.09 (out of 1) for Affine, BSpline and Demons registration, respectively, as well as breast boundary overlap and Jacobian determinant of the deformation field. The statistical analysis of the results showed that symmetric diffeomorphic Demons registration method outperforms also with the best breast alignment and non-negative Jacobian values which guarantee image similarity and anatomical consistency of the transformation, due to homologous forces enforcing the pixel geometric disparities to be shortened on all the frames. We propose Demons registration as an effective technique for time-series dynamic infrared registration, to stabilize the local temperature oscillation. The aim of the second implemented CAD application is to assess contribution of calcification in plaque vulnerability and wall rupture and to find its maximum resistance before break in image-based models of carotid artery stenting. The role of calcification inside fibroatheroma during carotid artery stenting operation is controversial in which cardiologists face two major problems during the placement: (i) “plaque protrusion” (i.e. elastic fibrous caps containing early calcifications that penetrate inside the stent); (ii) “plaque vulnerability” (i.e. stiff plaques with advanced calcifications that break the arterial wall or stent). Finite Element Analysis was used to simulate the balloon and stent expansion as a preoperative patient-specific virtual framework. A nonlinear static structural analysis was performed on 20 patients acquired using in vivo MDCT angiography. The Agatston Calcium score was obtained for each patient and subject-specific local Elastic Modulus (EM) was calculated. The in silico results showed that by imposing average ultimate external load of 1.1MPa and 2.3MPa on balloon and stent respectively, average ultimate stress of 55.7±41.2kPa and 171±41.2kPa are obtained on calcifications. The study reveals that a significant positive correlation (R=0.85, p<0.0001) exists on stent expansion between EM of calcification and ultimate stress as well as Plaque Wall Stress (PWS) (R=0.92, p<0.0001), comparing to Ca score that showed insignificant associations with ultimate stress (R=0.44, p=0.057) and PWS (R=0.38, p=0.103), suggesting minor impact of Ca score in plaque rupture. These average data are in good agreement with results obtained by other research groups and we believe this approach enriches the arsenal of tools available for pre-operative prediction of carotid artery stenting procedure in the presence of calcified plaques