About Real Time Tomography

Real Time Tomography provides state-of-the-art imaging solutions. We are recognized as leaders in advanced image processing and real-time image reconstruction for digital x-ray and tomosynthesis. Real Time Tomography is headquartered outside of Philadelphia, Pennsylvania.

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RTT Technical Papers & Posters

The following are technical papers and posters in which Real Time Tomography was an author or co-author.

Xue Susan Bai, MD, Alice S. Ha, MD, Susan Ng, MS, Katelyn Nye, BS, John M. Sabol, PhD, ePoster_3, Society of Skeletal Radiology Annual Meeting, 2015.

Presentation showing an application of Real Time Tomography's advanced reconstructions to body tomosynthesis images.

Andrew Tucker, Xin Qian, Emily Gidcumb, Derrek Spronk, Frank Sprange, Johnny Kuo, Susan Ng, Jianping Lu, Otto Zhou. Proceedings SPIE Medical Imaging 2012. Orlando, FL. February 2012.

Johnny Kuo, Peter A. Ringer, Steven G. Fallows, Predrag R. Bakic, Andrew D. A. Maidment, Susan Ng.Proc. SPIE 7961, Medical Imaging 2011: Physics of Medical Imaging, 796116 (March 16, 2011); doi:10.1117/12.878910

Dynamic Reconstruction and Rendering (DRR) is a fast and flexible tomosynthesis image reconstruction and display implementation. By leveraging the computational efficiency gains afforded by off-the-shelf GPU hardware, tomosynthesis reconstruction can be performed on demand at real-time, user-interactive frame rates. Dynamic multiplanar reconstructions allow the user to adjust reconstruction and display parameters interactively, including axial sampling, slice location, plane tilt, magnification, and filter selection. Reconstruction on-demand allows tomosynthesis images to be viewed as true three-dimensional data rather than just a stack of two-dimensional images. The speed and dynamic rendering capabilities of DRR can improve diagnostic accuracy and lead to more efficient clinical workflows.

P. Bakic, P. Ringer, J. Kuo, S.Ng and A.Maidment. Proceedings 10th International Workshop, IWDM 2010. Girona, Catalonia, Spain. June 16-18, 2010.

The geometric accuracy of a digital breast tomosynthesis (DBT) reconstruction algorithm was assessed using an anthropomorphic software breast phantom with simulated fiducial markers. The locations of the fiducial markers were measured from supersampled images reconstructed to sub-pixel precision. The measured locations were compared with the known ground truth positions of the simulated markers. The fiducial markers simulate small, attenuating objects within the software phantom. Using reconstructed images with resolution of 0.115 mm, and a total of twelve fiducial markers at three different depths, we determined an average difference of 0.105 mm (st. dev. 0.086 mm) between the estimated and true marker locations.

P. Bakic, S. Ng,P. Ringer, A.K. Carton, E. Conant, A. Maidment. Proceedings SPIE Medical Imaging 2010. San Diego, CA. February 2010.

Research methods were developed to determine whether regions of adipose and dense tissues in tomosynthesis images are correctly identified to reconstruct images which better preserve gray scale and edge information and to detemine the geometric accuracy of tomosynthesis image reconstruction algorithms.

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RTT Cited Papers & Posters

The following are technical papers and posters in which Real Time Tomography's products were used in the study or analysis.  

Raymond J. Acciavatti, William Mannherz, Margaret Nolan, Andrew D. A. Maidment. Proc. SPIE 10132, Medical Imaging 2017: Physics of Medical Imaging, 1013223 (March 9, 2017); doi:10.1117/12.2253986

Our previous work analyzed the Defrise phantom as a test object for evaluating image quality in digital breast tomosynthesis (DBT). The phantom is assembled from multiple plastic plates, which are arranged to form a square wave. In our previous work, there was no explicit analysis of how image quality varies with the thickness of the plates. To investigate this concept, a modified design of the phantom is now considered. For this purpose, each rectangular plate was laser-cut at an angle, creating a slope along which thickness varies continuously. The phantom was imaged using a clinical DBT system, and the relative modulation of the plastic-air separations was calculated in the reconstruction. In addition, a theoretical model was developed to determine whether modulation can be optimized by modifying the x-ray tube trajectory. It is demonstrated that modulation is dependent on the orientation of the frequency. Modulation is within detectable limits over a broad range of phantom thicknesses if frequency is parallel with the tube travel direction. Conversely, there is marked loss of modulation if frequency is oriented along the posteroanterior direction. In particular, as distance from the chest wall increases, there is a smaller range of thicknesses over which modulation is within detectable limits. Theoretical modeling suggests that this anisotropy is minimized by introducing tube motion along the posteroanterior direction. In conclusion, this paper demonstrates that the Defrise phantom is a tool for analyzing the limits of resolution in DBT systems. 

William S. Ferris, Trevor L. Vent, Tristan D. Maidment, Raymond J. Acciavatti, David E. Wurtele, Andrew D. A. Maidment. Proc. SPIE 10132, Medical Imaging 2017: Physics of Medical Imaging, 101324C (March 9, 2017); doi:10.1117/12.2255301

A method for geometric calibration of a next-generation tomosynthesis (NGT) system is proposed and tested. The NGT system incorporates additional geometric movements between projections over conventional DBT. These movements require precise geometric calibration to support magnification DBT and isotropic SR. A phantom was created to project small tungsten-carbide ball bearings (BB’s) onto the detector at four different magnifications. Using a bandpass filter and template matching, a MATLAB program was written to identify the centroid locations of each BB projection on the images. An optimization algorithm calculated an effective location for the source and detector that mathematically projected the BB’s onto the same locations on the detector as found on the projection images. The average distance between the BB projections on the image and the mathematically computed projections was 0.11 mm. The effective locations for the source and detector were encoded in the DICOM file for each projection; these were then used by the reconstruction algorithm. Tomographic image reconstructions were performed for three acquisition modes of the NGT system; these successfully demonstrated isotropic SR, magnified SR, and oblique reconstruction.

Lucas R. Borges, Igor Guerrero, Predrag R. Bakic, Alessando Voi, Andrew D. A. Maidment, Marcelo A. C. Vieira. IEEE Transactions on Medical Imaging, Volume: PP, Issue: 99, 10.1109/TMI.2017.2715826

This work proposes a new method of simulating dose reduction in digital breast tomosynthesis (DBT), starting from a clinical image acquired with a standard radiation dose. It considers both signal-dependent quantum and signal-independent electronic noise. Furthermore, the method accounts for pixel crosstalk, which causes the noise to be frequency-dependent, thus increasing the simulation accuracy. For an objective assessment, simulated and real images were compared in terms of noise standard deviation, signal-to-noise ratio (SNR) and normalized noise power spectrum (NNPS). A two-alternative forced-choice (2-AFC) study investigated the similarity between the noise strength of low-dose simulated and real images. Six experienced medical physics specialists participated on the study, with a total of 2,160 readings. Objective assessment showed no relevant trends with the simulated noise. The relative error in the standard deviation of the simulated noise was less than 2% for every projection angle. The relative error of the SNR was less than 1.5%, and the NNPS of the simulated images had errors less than 2.5%. The 2-AFC human observer experiment yielded no statistically significant difference (p=0.84) in the perceived noise strength between simulated and real images. Furthermore, the observer study also allowed the estimation of a dose difference at which the observer perceived a just-noticeable difference (JND) in noise levels. The estimated JND value indicated that a change of 17% in the current-time product was sufficient to cause a noticeable difference in noise levels. The observed high accuracy, along with the flexible calibration, make this method an attractive tool for clinical image-based simulations of dose reduction.

Tristan D. Maidment, Trevor L. Vent, William S. Ferris, David E. Wurtle, Raymond J. Acciavatti, Andrew D. A. Maidment, Proc. SPIE 10132, Medical Imaging 2017: Physics of Medical Imaging, 1013222 (March 9, 2017); doi:10.1117/12.2255564

Computed super-resolution (SR) is a method of reconstructing images with pixels that are smaller than the detector element size; superior spatial resolution is achieved through the elimination of aliasing and alteration of the sampling function imposed by the reconstructed pixel aperture. By comparison, magnification mammography is a method of projection imaging that uses geometric magnification to increase spatial resolution. This study explores the development and application of magnification digital breast tomosynthesis (MDBT). Four different acquisition geometries are compared in terms of various image metrics. High-contrast spatial resolution was measured in various axes using a lead star pattern. A modified Defrise phantom was used to determine the low-frequency spatial resolution. An anthropomorphic phantom was used to simulate clinical imaging. Each experiment was conducted at three different magnifications: contact (1.04x), MAG1 (1.3x), and MAG2 (1.6x). All images were taken on our next generation tomosynthesis system, an in-house solution designed to optimize SR. It is demonstrated that both computed SR and MDBT (MAG1 and MAG2) provide improved spatial resolution over non-SR contact imaging. To achieve the highest resolution, SR and MDBT should be combined. However, MDBT is adversely affected by patient motion at higher magnifications. In addition, MDBT requires more radiation dose and delays diagnosis, since MDBT would be conducted upon recall. By comparison, SR can be conducted with the original screening data. In conclusion, this study demonstrates that computed SR and MDBT are both viable methods of imaging the breast. 

Trevor L. Vent, Raymond J. Acciavatti, Young Joon Kwon, Andrew D. A. Maidment. Proc. SPIE 9783, Medical Imaging 2016: Physics of Medical Imaging, 978303 (March 22, 2016); doi:10.1117/12.2216260

Multiplanar reconstruction (MPR) in digital breast tomosynthesis (DBT) allows tomographic images to be portrayed in various orientations. We have conducted research to determine the resolution of tomosynthesis MPR. We built a phantom that houses a star test pattern to measure resolution. This phantom provides three rotational degrees of freedom. The design consists of two hemispheres with longitudinal and latitudinal grooves that reference angular increments. When joined together, the hemispheres form a dome that sits inside a cylindrical encasement. The cylindrical encasement contains reference notches to match the longitudinal and latitudinal grooves that guide the phantom’s rotations. With this design, any orientation of the star-pattern can be analyzed. Images of the star-pattern were acquired using a DBT mammography system at the Hospital of the University of Pennsylvania. Images taken were reconstructed and analyzed by two different methods. First, the maximum visible frequency (in line pairs per millimeter) of the star test pattern was measured. Then, the contrast was calculated at a fixed spatial frequency. These analyses confirm that resolution decreases with tilt relative to the breast support. They also confirm that resolution in tomosynthesis MPR is dependent on object orientation. Current results verify that the existence of super-resolution depends on the orientation of the frequency; the direction parallel to x-ray tube motion shows super-resolution. In conclusion, this study demonstrates that the direction of the spatial frequency relative to the motion of the x-ray tube is a determinant of resolution in MPR for DBT.

Andria Hadjipanteli, Premkumar Elangovan, Alistair Mackenzie, Padraig T Looney, Kevin Wells, David R Dance and Kenneth C Young, Physics in Medicine & Biology, Volume 62, Number 3, 7 February 2017.

Digital breast tomosynthesis (DBT) is under consideration to replace or to be used in combination with 2D-mammography in breast screening. The aim of this study was the comparison of the detection of microcalcification clusters by human observers in simulated breast images using 2D-mammography, narrow angle (15°/15 projections) and wide angle (50°/25 projections) DBT. The effects of the cluster height in the breast and the dose to the breast on calcification detection were also tested. Simulated images of 6 cm thick compressed breasts were produced with and without microcalcification clusters inserted, using a set of image modelling tools for 2D-mammography and DBT. Image processing and reconstruction were performed using commercial software. A series of 4-alternative forced choice (4AFC) experiments was conducted for signal detection with the microcalcification clusters as targets. Threshold detectable calcification diameter was found for each imaging modality with standard dose: 2D-mammography: 2D-mammography (165  ±  9 µm), narrow angle DBT (211  ±  11 µm) and wide angle DBT (257  ±  14 µm). Statistically significant differences were found when using different doses, but different geometries had a greater effect. No differences were found between the threshold detectable calcification diameters at different heights in the breast. Calcification clusters may have a lower detectability using DBT than 2D imaging.

Premkumar Elangovan, Andria Hadjipanteli, Alistair Mackenzie, David R. Dance, Kenneth C. Young and Kevin Wells. IWDM 2016: Breast Imaging pp 668-675.

Virtual clinical trials (VCTs) are increasingly being seen as a viable pre-clinical method for evaluation of imaging systems in breast cancer screening. The CR-UK funded OPTIMAM project is aimed at producing modelling tools for use in such VCTs. In the initial phase of the project, modelling tools were produced to simulate 2D-mammography and digital breast tomosynthesis (DBT) imaging systems. This paper elaborates on the new tools that have recently been developed for the current phase of the OPTIMAM project. These new additions to the framework include tools for simulating synthetic breast tissue, spiculated masses and variable-angle DBT systems. These tools are described in the paper along with the preliminary validation results. Four-alternative forced choice (4-AFC) type studies deploying these new tools are underway. The results of the ongoing 4AFC studies investigating minimum detectable contrast/size of masses/microcalcifications for different modalities and system designs are presented.

Lucas R. BorgesEmail authorIgor GuerreroPredrag R. BakicAndrew D. A. MaidmentHomero Schiabel, Marcelo C. Vieira, , IWDM 2016: Breast Imaging pp 343-350.

Clinical evaluation of dose reduction studies in x-ray breast imaging is problematic because it is difficult to justify imaging the same patient at a variety of radiation doses. One common alternative is to use simulation algorithms to manipulate a standard-dose exam to mimic reduced doses. Although there are several dose-reduction simulation methods for full-field digital mammography, the availability of similar methods for digital breast tomosynthesis (DBT) is limited. This work proposes a method for simulating dose reductions in DBT, based on the insertion of noise in a variance-stabilized domain. The proposed method has the advantage of performing signal-dependent noise injection without knowledge of the noiseless signal. We compared clinical low-dose DBT projections and reconstructed slices to simulated ones by means of power spectra, mean pixel values, and local standard deviations. The results of our simulations demonstrate low error (<5 %) between real and simulated images.

Alistair MackenzieEmail authorAndria HadjipanteliPremkumar ElangovanPadraig T. LooneyRebecca EaldenLucy M. WarrenDavid R. DanceKevin WellsKenneth C. Young, IWDM 2016: Breast Imaging pp 152-159

The aim of this study was to investigate the effect of dose on the detection of micro-calcification clusters in breast images using planar mammography and digital breast tomosynthesis (DBT). Planar and DBT images were created from mathematical models of breasts with and without inserted clusters of 5 identical calcifications. Regions of interest from the images were used in a series of 4-alternative forced choice human observer experiments using the clusters as targets. Three calcification diameters were used for each imaging condition. The threshold diameter required for micro-calcification detection was determined for a detection rate of 92.5 % at mean glandular doses of 1.25, 2.5, and 5 mGy. The measured threshold micro-calcification diameter was lower for planar mammography than for the DBT modality. The threshold micro-calcification diameter decreased with increasing dose for planar and DBT imaging. The image modality used had a larger effect on the threshold diameter than the dose change considered.

Hadjipanteli, A, Elangovan, P, Looney, PT, Mackenzie, A, Wells, K, Wells, K, Dance, DR and Young, KC (2016) Detection of microcalcification clusters by 2D-mammography and narrow and wide angle digital breast tomosynthesis In: Medical Imaging 2016: Physics of Medical Imaging, 2016-02-28 - 2016-03-02, San Diego, California, United States.

The aim of this study was to compare the detection of microcalcification clusters by human observers in breast images using 2D-mammography and narrow (15°/15 projections) and wide (50°/25 projections) angle digital breast tomosynthesis (DBT). Simulated microcalcification clusters with a range of microcalcification diameters (125 μm-275 μm) were inserted into 6 cm thick simulated compressed breasts. Breast images were produced with and without inserted microcalcification clusters using a set of image modelling tools, which were developed to represent clinical imaging by mammography and tomosynthesis. Commercially available software was used for image processing and image reconstruction. The images were then used in a series of 4-alternative forced choice (4AFC) human observer experiments conducted for signal detection with the microcalcification clusters as targets. The minimum detectable calcification diameter was found for each imaging modality: (i) 2D-mammography: 164±5 μm (ii) narrow angle DBT: 210±5 μm, (iii) wide angle DBT: 255±4 μm. A statistically significant difference was found between the minimum detectable calcification diameters that can be detected by the three imaging modalities. Furthermore, it was found that there was not a statistically significant difference between the results of the five observers that participated in this study. In conclusion, this study presents a method that quantifies the threshold diameter required for microcalcification detection, using high resolution, realistic images with observers, for the comparison of DBT geometries with 2D-mammography. 2Dmammography can visualise smaller detail diameter than both DBT imaging modalities and narrow-angle DBT can visualise a smaller detail diameter than wide-angle DBT.

Lia Morra, PhD, Daniela Sacchetto, MSc, Manuela Durando, MD, Silvano Agliozzo, PhD, Luca Alessandro Carbonaro, MD, Silvia Delsanto, PhD, Barbara Pesce, MD, Diego Persano, PhD, Giovanna Mariscotti, MD, Vincenzo Marra, MD, Paolo Fonio, MD, Alberto Bert, PhD. Radiology, Volume 227, Issue 1, October, 2015.

To evaluate a commercial tomosynthesis computer-aided detection (CAD) system in an independent, multicenter dataset.  This CAD system uses the Briona software to perform the reconstructions.

Marcelo A. C. Vieira, Helder C. R. de Oliveira, Polyana F. Nunes, Lucas R. Borges, Predrag R. Bakic, Bruno Barufaldi, Raymond J. Acciavatti, and Andrew D. A. Maidment. Proc. SPIE 9412, Medical Imaging 2015: Physics of Medical Imaging, 94122C (March 18, 2015); doi:10.1117/12.2082398

The main purpose of this work is to study the ability of denoising algorithms to reduce the radiation dose in Digital Breast Tomosynthesis (DBT) examinations. Clinical use of DBT is normally performed in “combo-mode”, in which, in addition to DBT projections, a 2D mammogram is taken with the standard radiation dose. As a result, patients have been exposed to radiation doses higher than used in digital mammography. Thus, efforts to reduce the radiation dose in DBT examinations are of great interest. However, a decrease in dose leads to an increased quantum noise level, and related decrease in image quality. This work is aimed at addressing this problem by the use of denoising techniques, which could allow for dose reduction while keeping the image quality acceptable. We have studied two “state of the art” denoising techniques for filtering the quantum noise due to the reduced dose in DBT projections: Non-local Means (NLM) and Block-matching 3D (BM3D). We acquired DBT projections at different dose levels of an anthropomorphic physical breast phantom with inserted simulated microcalcifications. Then, we found the optimal filtering parameters where the denoising algorithms are capable of recovering the quality from the DBT images acquired with the standard radiation dose. Results using objective image quality assessment metrics showed that BM3D algorithm achieved better noise adjustment (mean difference in peak signal to noise ratio < 0.1dB) and less blurring (mean difference in image sharpness ~ 6%) than the NLM for the projections acquired with lower radiation doses. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

André A. Bindilatti, Marcelo A. C. Vieira , Predrag R. Bakic , Andrew D. A. Maidment and Nelson D. A. Mascarenhas, Proceedings of XI Workshop de Visão Computacional ‐ October 05th‐07th, 2015

In paper we propose a new version of the non-local means (NLM) algorithm intended to reduce Poisson noise in Digital Breast Tomosynthesis (DBT). DBT is a novel medical imaging modality for breast cancer screening in which a limited number of low-dose projections are acquired as the X-ray tube moves over an arc. With the objective of achieving an appropriate level of image quality by reducing Poisson noise while preserving details in DBT images, we are proposing an alternative approach for the original NLM algorithm, in which the similarity measure between patches is performed considering stochastic distances and the estimation of a noise-free image using an iterative method. Results showed that this approach improved the performance of an algorithm previous proposed in the literature, called Stochastic Poisson NLM, when applied to a set of synthetic DBT images generated by a realistic 3D anthropomorphic software breast phantom based on a breast anatomy and imaging simulation pipeline.

Andrew D. A. Maidment, IWDM 2014: Breast Imaging pp 1-8

Validation of any imaging system is challenging due to the huge number of system parameters that should be evaluated. The ultimate metric of system performance is a clinical trial. However, the use of clinical trials is limited by cost and duration. We are strong proponents of a preclinical alternative, in the form of Virtual Clinical Trials (VCT), which model human anatomy, image acquisition, display and processing, and image analysis and interpretation. A complete VCT pipeline was envisioned by combining the breast anatomy and image acquisition simulation pipeline developed at the University of Pennsylvania, with the MeVIC image display and observation pipeline developed by researchers at Barco. Today an integrated virtual clinical trial design program, VCTdesigner, and a virtual clinical trial management program, VCTmanager, are freely available (www.VCTworld.org). The pipeline design is flexible and extensible, making it possible to add functionality easily and rapidly. It is our hope that by freely distributing the VCTmanager software, our field can standardize on this platform for running VCT.

Raymond J. Acciavatti and Andrew D. A. Maidment, Med. Phys. 40, 111912 (2013); http://dx.doi.org/10.1118/1.4819942; (19 pages)

In tomosynthesis, super-resolution has been demonstrated using reconstruction planes parallel to the detector.  Super-resolution allows for subpixel resolution relative to the detector.  The purpose of this work is to develop an analytical model that generates super-resolution to oblique reconstruction planes.

Raymond J. Acciavatti and Andrew D. A. Maidment. Med. Phys. 40, 111911 (2013); http://dx.doi.org/10.1118/1.4819941; (21 pages)

By convention, slices in a tomosynthesis reconstruction are created on planes parallel to the detector.  It has not been demonstrated that slices can be generated along oblique directions through the same volume, analogous to multiplanar reconstructions in computed tomography (CT).  The purpose of this work is to give a proof-of-principle justification for oblique reconstructions in tomosynthesis, which acquires projection images over smaller angular range than CT.

Andrew D. Maidment. dtic.mil. Mar 2013.

Contrast-enhanced digital breast tomosynthesis (CE-DBT) is a novel x-ray imaging technique that produces a 3D representation of the breast vasculature via an intravenous contrast agent. CE-DBT offers a combination of excellent spatial resolution and accurate functional information, suggesting a strong potential role in disease prognostication. We have developed an innovative technique for obtaining dynamic contrast-enhanced (DCE) images with high spatial and temporal resolution. We have demonstrated, in proof-ofprinciple, that 4D DCE-DBT is technically feasible and that the derived data accurately measures vascular dynamics. Previous contrast-enhanced DBT systems produced images at 2-3 fixed time points. Our novel acquisition technique is capable of producing perfusion images at 30-60 time points for the same radiation dose. The method is compatible with both temporal and dual-energy subtraction methods. Reconstruction is performed using one full set of sequentially-acquired images; however, unlike conventional DBT, the starting angle (and hence measurement time point) is arbitrary in our method. The resulting 4D data set consists of many time-resolved 3D functional measurements of tumor perfusion, offering the potential for superior lesion characterization and hence diagnostic accuracy.

Vieira, Marcelo Andrade da Costa Icon ; Bakic, Predrag R; Maidment, Andrew Douglas Arnold; Mascarenhas, Nelson Delfino d’Ávila. Workshop de Visão Computacional - WVC , IX, 2013, Rio de Janeiro.

Digital Breast Tomosynthesis (DBT) is a potential candidate to substitute digital mammography in breast cancer screening. In DBT, projection images are acquired with low levels of radiation, which significantly increases image noise. In this work, we evaluate the effect of a denoising filter, designed for digital mammography, on the reduction of quantum noise in DBT images. This filter is based on an adaptive Wiener filter and the Anscombe transformation, to reduce Poisson noise without significantly affecting image sharpness. Denoising was applied to a set of synthetic DBT images generated using a 3D anthropomorphic software breast phantom. Images without noise was also created to provide ground-truth information. In order to evaluate the denoising performance in different steps of the DBT imaging, filtering was applied separately to the projections (before reconstruction) and to the tomographic slices (after reconstruction). The performance of the filter was evaluated considering qualitative and quantitative analysis of the images before and after denoising.

Vieira, Marcelo Andrade da Costa Icon ; Bakic, Predrag R.; Maidment, Andrew Douglas Arnold, Proceedings of SPIE, Bellingham, v. 8668, 86680C, 2013

Individual projection images in Digital Breast Tomosynthesis (DBT) must be acquired with low levels of radiation, which significantly increases image noise. This work investigates the influence of a denoising algorithm and the Anscombe transformation on the reduction of quantum noise in DBT images. The Anscombe transformation is a variance-stabilizing transformation that converts the signal-dependent quantum noise to an approximately signalindependent Gaussian additive noise. Thus, this transformation allows for the use of conventional denoising algorithms, designed for additive Gaussian noise, on the reduction of quantum noise, by working on the image in the Anscombe domain. In this work, denoising was performed by an adaptive Wiener filter, previously developed for 2D mammography, which was applied to a set of synthetic DBT images generated using a 3D anthropomorphic software breast phantom. Ideal images without noise were also generated in order to provide a ground-truth reference. Denoising was applied separately to DBT projections and to the reconstructed slices. The relative improvement in image quality was assessed using objective image quality metrics, such as peak signal-to-noise ratio (PSNR) and mean structural similarity index (SSIM). Results suggest that denoising works better for tomosynthesis when using the Anscombe transformation and when denoising was applied to each projection image before reconstruction; in this case, an average increase of 9.1 dB in PSNR and 58.3% in SSIM measurements was observed. No significant improvement was observed by using the Anscombe transformation when denoising was applied to reconstructed images, suggesting that the reconstruction algorithm modifies the noise properties of the DBT images.

Andrew W. Tucker, Jianping Lu, and Otto Zhou. Med. Phys. 40, 031917 (2013); http://dx.doi.org/10.1118/1.4792296; (10 pages)

In principle, a stationary digital breast tomosynthesis (s-DBT) system has better image quality when compared to continuous motion DBT systems due to zero motion blur of the source.  The authors have developed a s-DBT system by using a linear carbon nanotube x-ray source array.  The purpose of the current study was to quantitatively evaluate the performance of the s-DBT system; and investigate the dependence of image quality on the system configuration parameters.

Acciavatti RJ. Maidment AD.; Med Phys. 2012 Dec;39(12):7518-39. doi: 10.1118/1.4757583

Digital breast tomosynthesis (DBT) is a 3D x-ray imaging modality in which tomographic sections of the breast are generated from a limited range of tube angles.  Because oblique x-ray incidence shifts the image of an object in subpixel detector element increments with each increasing projection angle, it is demonstrated that DBT is capable of super-resolution (i.e., subpixel resolution).

Acciavatti, Raymond J., dtic.mil, Jan 2012.

In tomosynthesis, a 3D image of the breast is generated from multiple x-ray projections. Although prior authors have modeled image quality in tomosynthesis, their work is limited in approximating the incident angle as normal to the detector. This research studies the consequences of carefully modeling the incident angle. From first principles, an analytical model of the transfer functions for oblique incidence is derived in individual projections. The anisotropy of the transfer functions over the detector area is then demonstrated, and a technique for optimizing detector thickness at various incident angles is developed. In addition to modeling the effect of non-normal incidence on transfer functions, it is shown that oblique incidence yields subpixel translational shifts in the image of the object with each projection angle. By calculating the reconstruction of a high frequency sine input, the potential for super-resolution (i.e., sub-pixel resolution) is established from this property. Superresolution is demonstrated in experimental images of bar patterns and select clinical examples of microcalcifications. The feasibility of super-resolution is also verified in a broad range of multi-planar reconstructions. Finally, from the analytical modeling of the sine input, the scan time which optimizes modulation in the reconstruction is calculated in systems with patient motion.

Raymond J. Acciavatti and Andrew D. A. Maidment. Proceedings SPIE Medical Imaging 2011. Orlando, FL. February 2011.

In this paper, a theoretical framework for super resolution (i.e. sub-pixel resolution) in digital breast tomosynthesis was developed.  Phantom and clinical tomosynthesis images were reconstructed using Real Time Tomography's Briona 3D image reconstruction software to demonstrate feasibility.

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