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The coronary artery calcium score (CACS) measures the buildup of calcium on the coronary artery wall and has been shown to be an important predictor of the risk of coronary artery diseases (CAD). Currently CACS is measured using CT, though the relatively high cost and high radiation dose has limited its adoption as a routine screening procedure. Digital Chest Tomosynthesis (DCT), a low dose and low cost alternative to CT, and has been shown to achieve 90% of sensitivity of CT in lung disease screening. However commercial DCT requires long scanning time and cannot be adapted for high resolution gated cardiac imaging, necessary for CACS. The stationary DCT system (s- DCT), developed in our lab, has the potential to significantly shorten the scanning time and enables high resolution cardiac gated imaging. Here we report the preliminary results of using s-DCT to estimate the CACS. A phantom heart model was developed and scanned by the s-DCT system and a clinical CT in a phantom model with realistic coronary calcifications. The adapted fan-beam volume reconstruction (AFVR) method, developed specifically for stationary tomosynthesis systems, is used to obtain high resolution tomosynthesis images. A trained cardiologist segmented out the calcifications and the CACS was obtained. We observed a strong correlation between the tomosynthesis derived CACS and CT CACS (r2 = 0.88). Our results shows s-DCT imaging has the potential to estimate CACS, thus providing a possible low cost and low dose imaging protocol for screening and monitoring CAD.

We have developed a clinically ready first generation stationary breast tomosynthesis system (s-DBT). In the s-DBT system, focal spot blur associated with x-ray source motion is completely eliminated, allowing for rapid acquisition of projection images over a larger angular span without changing the acquisition time. In the phantom studies the 1st generation s‐DBT system has demonstrated 30% higher spatial resolution than the corresponding continuous motion DBT systems. The system is currently being evaluated for its diagnostic performance in 100 patient clinical evaluation against FFDM. Initial results indicate that the s­‐DBT system can produce increased lesion conspicuity and comparable MC visibility. However due to x­‐ray flux limitations, certain large size patients have to be excluded. Recent studies have shown that increasing the angular span beyond 30° can be beneficial for enhanced depth resolution. We report the preliminary characterization of the 2nd generation s-­DBT system with a new CNT x-­ray source array, increased tube flux and a larger angular span. Increasing x‐ray tube flux allows for a larger patient population and dual energy imaging. Results indicate that the system delivers more than twice the flux, allowing for imaging of all size patients with acquisition time of 2­‐4 seconds. A 7° increase in angular span over 1st generation decreased the ASF by 37%. Additionally, the 2nd generation s‐DBT system utilizing a specific AFVR reconstruction method resulted in a 92% increase in the in plane resolution over CM DBT system, and a 37% increase in spatial resolution over the 1st generation s-‐DBT system.

Digital tomosynthesis is a type of limited angle tomography that allows 3D information to be reconstructed from a set of x-ray projection images taken at various angles using an x-ray tube, a mechanical arm to rotate the tube about the object, and a digital detector. Tomosynthesis reconstruction requires the precise location of the detector with respect to each x-ray source, forcing all current clinical tomosynthesis systems to use a physically coupled source and detector so the geometry is always known and is always the same. This limits the imaging geometries and its large size is impractical for mobile or field operations. To counter this, we have developed a free form tomosynthesis with a decoupled, free-moving source and detector that uses a novel optical method for accurate and real-time geometry calibration to allow for manual, hand-held tomosynthesis and even CT imaging. We accomplish this by using a camera, attached to the source, to track the motion of the source relative to the detector. Attached to the detector is an optical pattern and the image captured by the camera is then used to determine the relative camera/pattern position and orientation by analyzing the pattern distortion and calculating the source positions for each projection, necessary for 3D reconstruction. This allows for portable imaging in the field and also as an inexpensive upgrade to existing 2D systems, such as in developing countries, to provide 3D image data. Here we report the first feasibility demonstrations of free form digital tomosynthesis systems using the method.

Full field digital mammography (FFDM) has been the gold standard for mammography. It detects the presence, distribution, and morphology of microcalcifications (MCs), helping predict malignancy. Digital breast tomosynthesis (DBT) has overcome some limitations of FFDM such as poor sensitivity, specificity, and positive predictive values, due to superimposition of tissue, especially in dense breasts. Current DBT systems move an x-ray tube in either continuous (CM), or step-and-shoot motion (SSM). These systems are less effective than FFDM in MC detection due to lower spatial resolution. Motion of the x-ray source and system mechanical instability cause image blur. The image quality is further affected by patient motion due to the relatively long scan time. We developed a stationary DBT (s-DBT) system using a carbon nanotube (CNT) X-ray source array. The CNT array is electronically controlled, rapidly acquiring projection images over a large angular span, with zero tube motion. No source motion, coupled with a large angular span, results in improved in-plane and depth resolution. Using physical phantoms and human specimens, this system demonstrated higher spatial resolution than CM DBT. The objective of this study is to compare the diagnostic clinical performance of s-DBT to that of FFDM. Under UNC’s IRB regulations, 100 patients with breast lesions are being recruited and imaged with both modalities. A reader study will compare the diagnostic accuracy of the modalities. We have successfully imaged the first 30 patients. Initial results indicate that s-DBT alone produces comparable MC sharpness, and increased lesion conspicuity compared to FFDM.

Chest tomosynthesis is a low-dose 3-D imaging modality that has been shown to have comparable sensitivity as CT in detecting lung nodules and other lung pathologies. We have recently demonstrated the feasibility of stationary chest tomosynthesis (s-DCT) using a distributed CNT X-ray source array. The technology allows acquisition of tomographic projections without moving the X-ray source. The electronically controlled CNT x-ray source also enables physiologically gated imaging, which will minimize image blur due to the patient’s respiration motion. In this paper, we investigate the feasibility of prospective gated chest tomosynthesis using a bench-top s-DCT system with a CNT source array, a high- speed at panel detector and realistic patient respiratory signals captured using a pressure sensor. Tomosynthesis images of inflated pig lungs placed inside an anthropomorphic chest phantom were acquired at different respiration rate, with and without gating for image quality comparison. Metal beads of 2 mm diameter were placed on the pig lung for quantitative measure of the image quality. Without gating, the beads were blurred to 3:75 mm during a 3 s tomosynthesis acquisition. When gated to the end of the inhalation and exhalation phase the detected bead size reduced to 2:25 mm, much closer to the actual bead size. With gating the observed airway edges are sharper and there are more visible structural details in the lung. Our results demonstrated the feasibility of prospective gating in the s-DCT, which substantially reduces image blur associated with lung motion.

Digital breast tomosynthesis (DBT) provides 3D images which remove tissue overlapping and enables better cancer detection. Stationary DBT (s-DBT) uses a fixed X-ray source array to eliminate image blur associated with the x-ray tube motion and provides better image quality as well as faster scanning speed. For limited angle tomography, it is known that iterative reconstructions generally produces better images with fewer artifacts. However classical iterative tomosynthesis reconstruction methods are considerably slower than the filtered back-projection (FBP) reconstruction. The linear x-ray source array used in s-DBT enables a computationally more efficient volume reconstruction using adapted fan beam slice sampling, which transforms the 3-D cone beam reconstruction to a series of 2-D fan beam slice reconstructions. In this paper, we report the first results of the adapted fan-beam volume reconstruction (AFVR) for the s-DBT system currently undergoing clinical trial at UNC, using a simultaneous algebraic reconstruction technique (SART). An analytic breast phantom is used to quantitatively analyze the performance of the AFVR. Image quality of a CIRS biopsy phantom reconstructed using the AFVR method are compared to that using FBP algorithm with a commercial package. Our results show a significant reduction in memory usage and an order of magnitude speed increase in reconstructing speed using AFVR compared to that of classical 3-D cone beam reconstruction. We also observed that images reconstructed by AFVR with SART had a better sharpness and contrast compared to that using FBP. Preliminary results on patient images demonstrates the improved detectability of the s-DBT system over the mammography. By utilizing parallel computing with graphics processing unit (GPU), it is expected that the AFVR method will enable iterative reconstruction technique to be practical for clinical applications.

Micro-CT is a high-resolution volumetric imaging tool that provides imaging evaluations for many preclinical applications. However, the relatively high cumulative radiation dose from micro-CT scans could lead to detrimental influence on the experimental outcomes or even the damages of specimens. Interior micro-computed tomography (micro- CT) produces exact tomographic images of an interior region-of-interest (ROI) embedded within an object from truncated projection data. It holds promises for many biomedical applications with significantly reduced radiation doses. Here, we present our first implementation of an interior micro-CT system using a carbon nanotube (CNT) field-emission microfocus x-ray source. The system has two modes – interior micro-CT mode and global micro-CT mode, which is realized with a detachable x-ray beam collimator at the source side. The interior mode has an effective field-of-view (FOV) of about 10mm in diameter, while for the global mode the FOV is about 40mm in diameter. We acquired CT data in these two modes from a mouse-sized phantom, and compared the reconstructed image qualities and the associated radiation exposures. Interior ROI reconstruction was achieved by using our in-house developed reconstruction algorithm. Overall, interior micro-CT demonstrated comparable image quality to the conventional global micro-CT. Radiation doses measured by an ion chamber show that interior micro-CT yielded significant dose reduction (up to 83%).

Digital chest tomosynthesis (DCT) is a 3D imaging modality which has been shown to approach the diagnostic capability of CT, but uses only one-tenth the radiation dose of CT. One limitation of current commercial DCT is the mechanical motion of the x-ray source which prolongs image acquisition time and introduces motion blurring in images. By using a carbon nanotube (CNT) x-ray source array, we have developed a stationary digital chest tomosynthesis (s- DCT) system which can acquire tomosynthesis images without mechanical motion, thus enhancing the image quality. The low dose and high quality 3D image makes the s-DCT system a viable imaging tool for monitoring cystic fibrosis (CF) patients. The low dose is especially important in pediatric patients who are both more radiosensitive and have a longer lifespan for radiation symptoms to develop. The purpose of this research is to evaluate the feasibility of using s-DCT as a faster, lower dose means for diagnosis and monitoring of CF in pediatric patients. We have created an imaging phantom by injecting a gelatinous mucus substitute into porcine lungs and imaging the lungs from within an anthropomorphic hollow chest phantom in order to mimic the human conditions of a CF patient in the laboratory setting. We have found that our s-DCT images show evidence of mucus plugging in the lungs and provide a clear picture of the airways in the lung, allowing for the possibility of using s- DCT to supplement or replace CT as the imaging modality for CF patients.

Digital chest tomosynthesis (DCT) provides superior image quality and depth information for thoracic imaging at relatively low dose, though the presence of strong photon scatter degrades the image quality. In most chest radiography, anti-scatter grids are used. However, the grid also blocks a large fraction of the primary beam photons requiring a significantly higher imaging dose for patients. Previously, we have proposed an efficient low dose scatter correction technique using a primary beam sampling apparatus. We implemented the technique in stationary digital breast tomosynthesis, and found the method to be efficient in correcting patient-specific scatter with only 3% increase in dose. In this paper we reported the feasibility study of applying the same technique to chest tomosynthesis. This investigation was performed utilizing phantom and cadaver subjects. The method involves an initial tomosynthesis scan of the object. A lead plate with an array of holes, or primary sampling apparatus (PSA), was placed above the object. A second tomosynthesis scan was performed to measure the primary (scatter-free) transmission. This PSA data was used with the full-field projections to compute the scatter, which was then interpolated to full-field scatter maps unique to each projection angle. Full-field projection images were scatter corrected prior to reconstruction. Projections and reconstruction slices were evaluated and the correction method was found to be effective at improving image quality and practical for clinical implementation.

Microbeam radiation therapy (MRT) uses an array of high-dose, narrow (~100 μm) beams separated by a fraction of a millimeter to treat various radio-resistant, deep-seated tumors. MRT has been shown to spare normal tissue up to 1000 Gy of entrance dose while still being highly tumoricidal. Current methods of tumor localization for our MRT treatments require MRI and X-ray imaging with subject motion and image registration that contribute to the measurement error. The purpose of this study is to develop a novel form of imaging to quickly and accurately assist in high resolution target positioning for MRT treatments using X-ray fluorescence (XRF). The key to this method is using the microbeam to both treat and image. High Z contrast media is injected into the phantom or blood pool of the subject prior to imaging. Using a collimated spectrum analyzer, the region of interest is scanned through the MRT beam and the fluorescence signal is recorded for each slice. The signal can be processed to show vascular differences in the tissue and isolate tumor regions. Using the radiation therapy source as the imaging source, repositioning and registration errors are eliminated. A phantom study showed that a spatial resolution of a fraction of microbeam width can be achieved by precision translation of the mouse stage. Preliminary results from an animal study showed accurate iodine profusion, confirmed by CT. The proposed image guidance method, using XRF to locate and ablate tumors, can be used as a fast and accurate MRT treatment planning system.

We have recently demonstrated the feasibility of stationary digital chest tomosynthesis (s-DCT) using a dis- tributed carbon nanotube x-ray source array. The technology has the potential to increase the imaging resolution and speed by eliminating source motion. In addition, the flexibility in the spatial configuration of the individual sources allows new tomosynthesis imaging geometries beyond the linear scanning mode used in the conventional systems. In this paper, we report the preliminary results on the effects of the tomosynthesis imaging geometry on the image quality. The study was performed using a bench-top s-DCT system consisting of a CNT x-ray source array and a flat-panel detector. System MTF and ASF are used as quantitative measurement of the in-plane and in-depth resolution. In this study geometries with the x-ray sources arranged in linear, square, rectangular and circular configurations were investigated using comparable imaging doses. Anthropomorphic chest phantom images were acquired and reconstructed for image quality assessment. It is found that wider angular coverage results in better in-depth resolution, while the angular span has little impact on the in-plane resolution in the linear geometry. 2D source array imaging geometry leads to a more isotropic in-plane resolution, and better in-depth resolution compared to 1D linear imaging geometry with comparable angular coverage.

Current digital breast tomosynthesis (DBT) systems have been shown to have diminished microcalcification (MC) visibility compared to 2D mammography systems. Rotating gantry DBT systems require mechanical motion of the X-ray source which causes motion blurring of the focal spot, thus reducing spatial resolution. We have developed a stationary DBT (s-DBT) technology that uses a carbon nanotube (CNT) based X-ray source array in order to acquire all the projections images without any mechanical motion. It is capable of producing full tomosynthesis datasets with zero motion blur. It has been shown to have significantly higher spatial resolution than continuous motion DBT systems. An s-DBT system also allows for a wider angular span without increasing the acquisition time. A larger angular span covers a larger portion of the Fourier domain, thus decreasing the tissue overlap. In this study, we compare tomosynthesis imaging of MCs, in lumpectomy specimens, between an s-DBT system and a rotating gantry DBT system. Results show that s-DBT produces better MC sharpness and reduced tissue overlap compared to continuous motion DBT systems.

Stationary Digital Breast Tomosynthesis (sDBT) is a carbon nanotube based breast imaging device with fast data acquisition and decent projection resolution to provide three dimensional (3-D) volume information. To- mosynthesis 3-D image reconstruction is faced with the challenges of the cone beam geometry and the incomplete and nonsymmetric sampling due to the sparse views and limited view angle. Among all available reconstruction methods, statistical iterative method exhibits particular promising since it relies on an accurate physical and statistical model with prior knowledge. In this paper, we present the application of an edge-preserved regularizer to our previously proposed precomputed backprojection based penalized-likelihood (PPL) reconstruction. By using the edge-preserved regularizer, our experiments show that through tuning several parameters, resolution can be retained while noise is reduced significantly. Compared to other conventional noise reduction techniques in image reconstruction, less resolution is lost in order to gain certain noise reduction, which may benefit the research of low dose tomosynthesis.

Micro-beam radiation therapy (MRT) uses parallel planes of high dose narrow (10–100 um in width) radiation beams separated by a fraction of a millimeter to treat cancerous tumors. This experimental therapy method based on synchrotron radiation has been shown to spare normal tissue at up to 1000Gy of entrance dose while still being effective in tumor eradication and extending the lifetime of tumor-bearing small animal models. Motion during the treatment can result in significant movement of micro beam positions resulting in broader beam width and lower peak to valley dose ratio (PVDR), and thus can reduce the effectiveness of the MRT. Recently we have developed the first bench-top image guided MRT system for small animal treatment using a high powered carbon nanotube (CNT) x-ray source array. The CNT field emission x-ray source can be electronically synchronized to an external triggering signal to enable physiologically gated firing of x-ray radiation to minimize motion blurring. Here we report the results of phantom study of respiratory gated MRT. A simulation of mouse breathing was performed using a servo motor. Preliminary results show that without gating the micro beam full width at tenth maximum (FWTM) can increase by 70% and PVDR can decrease up to 50%. But with proper gating, both the beam width and PVDR changes can be negligible. Future experiments will involve irradiation of mouse models and comparing histology stains between the controls and the gated irradiation.

X-ray fluorescence molecular imaging (XFMI) can be a potential alternative to existing molecular imaging modalities providing high sensitivity and good spatial resolution. However, high sensitivity at a few tens of μg/mL can be reached only with monochromatic synchrotron x-rays; in typical laboratory setting using conventional x-ray sources XFMI has been reported to reach only about 10 mg/mL sensitivity. In this paper, we demonstrated the feasibility of simultaneously detecting x-ray fluorescence signals from a mouse-sized object containing iodine and indium solutions at 50 μg/mL concentration using a carbon nanotube (CNT) x-ray source. XFMI has the high potential to provide molecular imaging capability in small-animal models with high sensitivity, high spatial and temporal resolution, high multiplexing capacity, and at low radiation dose.

Carbon nanotube (CNT) micro-focus x-ray tubes have been demonstrated as a novel technology for in-vivo small animal imaging. It enables simultaneous respiratory and cardiac gated prospective CT imaging of free breathing animals with high temporal resolution. Operating the micro-focus CNT x-ray source at high power is required to achieve high temporal resolution. The thermal loading of the anode focal spot is a limiting factor in determining the maximum power of an x-ray tube. In this paper, we developed a reliable simulation model to quantitatively analyze the anode heat load of the CNT x-ray source operating in both DC and pulse modes. The anode temperature distribution is simulated using finite element analysis. The model is validated by comparing simulation results for the micro-focus x- ray tube with reported experimental results. We investigated the relationship between the maximum power and the effective focal spot size for CNT micro-CT system running in both DC and pulse modes. Our results show that when operating in pulse mode, the maximum power of the CNT x-ray source can be significantly higher than when operating in DC mode. In DC mode, we found that the maximum power scales non-linearly with the effective focal spot size as P(in W) = (0.25/ sin θ+1.6)f0.73 s (in μm), where 1/sin θ is the projection factor for a given anode angle θ. However, in pulse mode the maximum power linearly increases with the effective focal spot size asP(in W) = (0.20/ sin θ+0.35)fs(in μm), and is significantly higher than that in the DC mode. This implies that it is feasible to improve the micro-CT temporal resolution further without sacrificing the image quality. The simulation method developed here also enables us to analyze the thermal loading of the other CNT x-ray sources for other applications, such as the stationary digital breast tomosynthesis scanner and the CNT microbeam radiation therapy system.

A prototype stationary digital breast tomosynthesis (s-DBT) system has been developed by retrofitting a Hologic Selenia Dimension rotating gantry tomosynthesis scanner with a spatially distributed carbon nanotube (CNT) x-ray source array. The goal is to improve the system spatial resolution by removing the x-ray tube motion induced focal spot blurring. The CNT x-ray source array comprises 31 individually addressable x-ray beams covering 30° angular span. Each x-ray beam has a minimum focal spot size of 0.64×0.61mm (full-width-at-half-maximum), a stationary W anode operating up to 50kVp, and 1mm thick Al filter. The flux from each beam is regulated and varied using dedicated control electronics. The maximum tube current is determined by the heat load of the stationary anode and depends on the energy, pulse width and the focal spot size used. Stable operation at 28kVp, 27mA tube current, 250msec pulse width and 38mA tube current, 183msec pulse width per exposure was achieved with extended lifetime. The standard ACR phantom was imaged and analyzed to evaluate the image quality. The actual scanning speed depends on the number of views and the readout time of the x-ray detector. With the present detector, 6 second scanning time at either 15 views or 31 views can be achieved at 100mAs total imaging dose with a detector readout time of 240msec.

The stationary Digital Breast Tomosynthesis System (s-DBT) has the advantage over the conventional DBT systems as there is no motion blurring in the projection images associated with the x-ray source motion. We have developed a prototype s-DBT system by retrofitting a Hologic Selenia Dimensions rotating gantry tomosynthesis system with a distributed carbon nanotube (CNT) x-ray source array. The linear array consists of 31 x-ray generating focal spots distributed over a 30 degree angle. Each x-ray beam can be electronically activated allowing the flexibility and easy implementation of novel tomosynthesis scanning with different scanning parameters and configurations. Here we report the initial results of investigation on the imaging quality of the s-DBT system and its dependence on the acquisition parameters including the number of projections views, the total angular span of the projection views, the dose distribution between different projections, and the total dose. A mammography phantom is used to visually assess image quality. The modulation transfer function (MTF) of a line wire phantom is used to evaluate the system spatial resolution. For s-DBT the in-plan system resolution, as measured by the MTF, does not change for different configurations. This is in contrast to rotating gantry DBT systems, where the MTF degrades for increased angular span due to increased focal spot blurring associated with the x-ray source motion. The overall image quality factor, a composite measure of the signal difference to noise ratio (SdNR) for mass detection and the z-axis artifact spread function for microcalcification detection, is best for the configuration with a large angular span, an intermediate number of projection views, and an even dose distribution. These results suggest possible directions for further improvement of s-DBT systems for high quality breast cancer imaging.

We report the progress in development of carbon nanotube (CNT) field emission micro-focus x-ray tubes for dynamic small animal imaging with high spatial and temporal resolution. Extensive electron optics simulations were performed to study the focusing structure and optimize the tube design. 3D finite element analysis was used for modeling and simulating electron beam optics. A simple and intuitive model is developed to model the field emission properties of CNT cathodes. The dependence of focus spot size and the anode current on the gate extracting voltage, the focusing voltages, the gate mesh geometry, and other geometric parameters were studied. Several tubes were built according to the optimal design. The experimentally measured focus spot size and its dependence on the focus voltages were found to be in quantitative agreement with simulations.

We have previously reported the development of a dynamic micro-CT scanner with a stationary mouse bed using a compact carbon nanotube (CNT) field emission x-ray tube and preliminary results on its utility for prospectively gated cardiac imaging. In this paper we report the recent progress in improving the perf ormance characteristics of this scanner. Through optimization of the CNT cathode, the stable emission current has been increased. The output power of the CNT x-ray source has reached ~100W peak power at 100 P m focal spot size. The higher flux enables improvement of the x-ray energy spectrum to minimize the beam hardening effect and increasing the system temporal resolution by using shorter x-ray exposure time. The scanner’s temporal resoluti on has been increased to ~10 msec, which is sufficient for high-resolution micro-CT imaging of mouse heart and lung under free-breathing setting. The spatial resolution is maintained at 6.2 lp per mm at 10% system MTF. The nanotube micro-CT scanner’s application in mouse cardiac imaging has been demonstrated with high-resolution (80 P m and 15 msec) micro-CT of the mouse heart under free-breathing setting. Keywords: cardiac imaging, micro-CT, x-ray, carbon nanotube

Digital breast tomosynthesis is a new technique to improve the early detection of breast cancer by providing three-dimensional reconstruction volume of the object with limited-angle projection images. This paper investigated the image reconstruction with a standard biopsy training breast phantom using a novel multi-beam X-ray sources breast tomosynthesis system. Carbon nanotube technology based X-ray tubes were lined up along a parallel-imaging geometry to decrease the motion blur. Five representative reconstruction algorithms, including back projection (BP), filtered back projection (FBP), matrix inversion tomosynthesis (MITS), maximum likelihood expectation maximization (MLEM) and simultaneous algebraic reconstruction technique (SART), were investigated to evaluate the image reconstruction of the tomosynthesis system. Reconstructed images of the masses and micro-calcification clusters embedded in the phantom were studied. The evaluated multi-beam X-ray breast tomosynthesis system is able to generate three-dimensional information of the breast phantom with clearly-identified regions of the masses and calcifications. Future study will be done soon to further improve the imaging parameters' measurement and reconstruction.

As a new three-dimensional breast imaging technique, breast tomosynthesis allows the reconstruction of an arbitrary set of planes in the breast from a limited-angle series of x-ray projection images. The breast tomosynthesis technique has been demonstrated as promising to improve early breast cancer detection. This paper represents a preliminary phantom study and computer simulation results of different breast tomosynthesis reconstruction algorithms with a novel carbon nanotube based multi-beam x-ray source. Five representative tomosynthesis reconstruction algorithms, including back projection (BP), filtered back projection (FBP), matrix inversion tomosynthesis (MITS), maximum likelihood expectation maximization (MLEM), and simultaneous algebraic reconstruction technique (SART) were investigated. Tomosynthesis projection images of a phantom were acquired with the stationary multi-beam x-ray tomosynthesis system. Reconstruction results from different algorithms were studied. A computer simulation study was further done to investigate the sharpness of reconstructed in-plane structures and to see how effective each algorithm is at removing out-of-plane blur with parallel-imaging geometries. Datasets with 9 and 25 projection images of a defined 3D spherical object were simulated with a total view angle of 50 degrees. Results showed that the multi-beam x-ray system is capable to generate 3D tomosynthesis images with faster speed compared with current commercial prototype systems. With simulated parallel-imaging geometry, MITS and FBP showed edge enhancement in-plane performance. BP, FBP and MLEM performed better at out-of-plane structure removal with larger number of projection images.

A prototype physiologically gated micro-computed tomography (micro-CT) system based on a “eld emissionmicro-focus x-ray sour ce has been developed for in vivo imaging of small animal models. The novel x-raysource can generate radiation with a programmable waveform that can be readily synchronized and gated withnon-periodic physiological signals. The system performance is evaluated using phantoms and sacri“ced andanesthetized mouse models. Prospect ive respiratory-gated CT images of a nesthetized free-breathing mice arecollected using this scanner at 100msec temporal resolution and 10lp/mm of 10% system MTF.Keywords: micro-CT, in vivo imaging, respiratory gating, x-ray source, carbon nanotube 1. INTRODUCTION Micro-computed tomography (micro-CT) is an important tool in non-invasive screening of small animals suchas mice and rats for pre-c linical cancer studies. 1–3 Compared to clinical CT scanners, a much higher spatialresolution is needed in order to image the anatomy of small animals with research interest. Current commercialmicro-CT scanners oer the capability of imaging objects ex-vivo with high spatial resolution. Studies on lungand colon cancer models have shown that micro-CT is capable of sequentially tracking tumors of larger than2mm in diameter with high “delity. Small tumors are still hardly distinguishable from the normal tissue, whichis partially attributed to the motion-induced artifacts created by peristalsis, respiration and cardiac motion.The motion-induced artifacts can in principle be minimized by prospective gating where the image acquisition issynchronizedwith the physiological signals, as commonly done in clinical CT scanners. However, performing suchmeasurements on small animals is challenging because their physiological motions are at least ten times fasterthan those of human. Motion-induced artifacts blur the micro-CT image resulting in signi“cantly deterioratedspatial resolution than the nominal values.Several new designs have been considered for high-resolution CT imaging of live animals. One is to use ahigh power rotating anode x-ray source instead of a “xed-anode micro-focus x-ray tube.

A stationary digital breast tomosynthesis (DBT) system using a carbon nanotube based multi-beam field emission x-ray (MBFEX) source has been designed. The purpose is to investigate the feasibility of reducing the total imaging time, simplifying the system design, and potentially improving the image quality comparing to the conventional DBT scanners. The MBFEX source consists of 25 individually programmable x-ray pixels which are evenly angular spaced covering a 48° field of view. The device acquires the projection images by electronically switching on and off the individual x-ray pixels without mechanical motion of either the x-ray source or the detector. The designs of the x-ray source and the imaging system are presented. Some preliminary results are discussed.

State-of-the-art tomographic imaging technique is based upon of simple serial imaging scheme. The tomographic scanners collect the projection images sequentially in the time domain, by a step-and-shoot process using a single-pixel x-ray source. The inefficient serial data collection scheme severely limits the data collection speed, which is critical for imaging of objects in rapid motion such as for diagnosis of cardiovascular diseases, CT fluoroscopy, and airport luggage inspection. Further improvement of the speed demands an increasingly high x-ray peak workload and gantry rotation speed, both of which have approached the engineering limits. Multiplexing technique, which has been widely adopted in communication devices and in certain analytical instruments, holds the promise to significantly increase the data throughput. It however, has not been applied to x-ray radiography, mainly due to limitations of the current x-ray source technology. Here we report a method for frequency multiplexing radiography (FMR) based on the frequency multiplexing principle and the carbon nanotube field emission x-ray technology. We show the feasibility of multiplexing radiography that enables simultaneous collection of multiple projection images. It has the potential to significantly increase the imaging speed for tomographic imaging without compromising the imaging quality.

We describe Sonic Infrared Imaging NDE for materials and structures. In this imaging technique, a short ultrasonic pulse is applied to the structure/material to cause heating of the defects, while an infrared camera images the time evolution of the heating effect to identify the defective areas in the target. The heating effect is astonishing. In this paper, we'll include our study of Sonic IR imaging NDE on aircraft structure specimens, automotive specimens, etc. for metals, composites, ceramics, addressing fatigue cracks, and delaminations/disbonds. Some fundamental issues related to Sonic IR imaging NDE are discussed in this paper as well.

To reveal the spatial pattern of localized prostate cancer distribution, a 3D statistical volumetric model, showing the probability map of prostate cancer distribution, together with the anatomical structure of the prostate, has been developed from 90 digitally-imaged surgical specimens. Through an enhanced virtual environment with various visualization modes, this master model permits for the first time an accurate characterization and understanding of prostate cancer distribution patterns. The construction of the statistical volumetric model is characterized by mapping all of the individual models onto a generic prostate site model, in which a self-organizing scheme is used to decompose a group of contours representing multifold tumors into localized tumor elements. Next crucial step of creating the master model is the development of an accurate multi- object and non-rigid registration/warping scheme incorporating various variations among these individual moles in true 3D. This is achieved with a multi-object based principle-axis alignment followed by an affine transform, and further fine-tuned by a thin-plate spline interpolation driven by the surface based deformable warping dynamics. Based on the accurately mapped tumor distribution, a standard finite normal mixture is used to model the cancer volumetric distribution statistics, whose parameters are estimated using both the K-means and expectation- maximization algorithms under the information theoretic criteria. Given the desired number of tissue samplings, the prostate needle biopsy site selection is optimized through a probabilistic self-organizing map thus achieving a maximum likelihood of cancer detection. We describe the details of our theory and methodology, and report our pilot results and evaluation of the effectiveness of the algorithm in characterizing prostate cancer distributions and optimizing needle biopsy techniques.

A new dry etching technique--development-free vapor photolithography was used to transfer pattern on silicon nitride film. Plasma enhanced chemical vapor deposition silicon nitride film and thin low pressure chemical vapor deposition silicon nitride film can be etched to get positive pattern. The difference of etching rate between exposed area and unexposed area was attributed to the concentration difference of accelerators which was realized through photochemical reaction. The reaction mechanism and other phenomena have also been discussed.