Tomosynthesis Scanner Research Articles

Online Calibration of a Linear Micro Tomosynthesis Scanner.

In a linear tomosynthesis scanner designed for imaging histologic samples of several centimeters size at 10 µm resolution, the mechanical instability of the scanning stage (±10 µm) exceeded the resolution of the image system, making it necessary to determine the trajectory of the stage for each scan to avoid blurring and artifacts in the images that would arise from the errors in the geometric information used in 3D reconstruction. We present a method for online calibration by attaching a layer of randomly dispersed micro glass beads or calcium particles to the bottom of the sample stage. The method was based on a parametric representation of the rigid body motion of the sample stage-marker layer assembly. The marker layer was easy to produce and proven effective in the calibration procedure.

Multifocal calcific periarthritis with distinctive clinical and radiological features in patients with CD73 deficiency.

Arterial calcification due to deficiency of CD73 (ACDC) is a hereditary autosomal recessive ectopic mineralization syndrome caused by loss-of-function mutations in the ecto-5'-nucleotidase gene. Periarticular calcification has been reported but the clinical characterization of arthritis as well as the microstructure and chemical composition of periarticular calcifications and SF crystals has not been systematically investigated. Eight ACDC patients underwent extensive rheumatological and radiological evaluation over a period of 11 years. Periarticular and synovial biopsies were obtained from four patients. Characterization of crystal composition was evaluated by compensated polarized light microscopy, Alizarin Red staining for synovial fluid along with X-ray diffraction and X-ray micro tomosynthesis scanner for periarticular calcification. Arthritis in ACDC patients has a clinical presentation of mixed erosive-degenerative joint changes with a median onset of articular symptoms at 17 years of age and progresses over time to the development of fixed deformities and functional limitations of small peripheral joints with, eventually, larger joint and distinct axial involvement later in life. We have identified calcium pyrophosphate and calcium hydroxyapatite (CHA) crystals in SF specimens and determined that CHA crystals are the principal component of periarticular calcifications. This is the largest study in ACDC patients to describe erosive peripheral arthropathy and axial enthesopathic calcifications over a period of 11 years and the first to identify the composition of periarticular calcifications and SF crystals. ACDC should be considered among the genetic causes of early-onset OA, as musculoskeletal disease signs may often precede vascular symptoms.

Evaluating attenuation correction strategies in a dedicated, single-gantry breast PET-tomosynthesis scanner

We are developing a dedicated, combined breast positron emission tomography (PET)-tomosynthesis scanner. Both the PET and digital breast tomosynthesis (DBT) scanners are integrated in a single gantry to provide spatially co-registered 3D PET-tomosynthesis images. The DBT image will be used to identify the breast boundary and breast density to improve the quantitative accuracy of the PET image. This paper explores PET attenuation correction (AC) strategies that can be performed with the combined breast PET-DBT scanner to obtain more accurate, quantitative high-resolution 3D PET images. The PET detector is comprised of a 32 × 32 array of 1.5 × 1.5 × 15 mm3 LYSO crystals. The PET scanner utilizes two detector heads separated by either 9 or 11 cm, with each detector head having a 4 × 2 arrangement of PET detectors. GEANT4 Application for Tomographic Emission simulations were performed using an anthropomorphic breast phantom with heterogeneous attenuation under clinical DBT-compression. FDG-avid lesions, each 5 mm in diameter with 8:1 uptake, were simulated at four locations within the breast. Simulations were performed with a scan time of 2 min. PET AC was performed using the actual breast simulation model as well as DBT reconstructed volumetric images to derive the breast outline. In addition to using the known breast density as defined by the breast model, we also modeled it as uniform patient-independent soft-tissue, and as a uniform patient-specific material derived from breast tissue composition. Measured absolute lesion uptake was used to evaluate the quantitative accuracy of performing AC using the various strategies. This study demonstrates that AC is necessary to obtain a closer estimate of the true lesion uptake and background activity in the breast. The DBT image dataset assists in measuring lesion uptake with low bias by facilitating accurate breast delineation as well as providing accurate information related to the breast tissue composition. While both the uniform soft-tissue and patient-specific material approaches provides a close estimate to the ground truth, <5% bias can be achieved by using a uniform patient-specific material to define the attenuation map.

Characterization of a multi-pinhole molecular breast tomosynthesis scanner

In recent years, breast imaging using radiolabelled molecules has attracted significant interest. Our group has proposed a multi-pinhole molecular breast tomosynthesis (MP-MBT) scanner to obtain 3D functional molecular breast images at high resolutions. After conducting extensive optimisation studies using simulations, we here present a first prototype of MP-MBT and evaluate its performance using physical phantoms. The MP-MBT design is based on two opposing gamma cameras that can image a lightly compressed pendant breast. Each gamma camera consists of a 250 × 150 mm2 detector equipped with a collimator with multiple pinholes focusing on a line. The NaI(Tl) gamma detector is a customised design with 3.5 mm intrinsic spatial resolution and high spatial linearity near the edges due to a novel light-guide geometry and the use of square PMTs. A volume-of-interest is scanned by translating the collimator and gamma detector together in a sequence that optimises count yield from the scan region. Derenzo phantom images showed that the system can reach 3.5 mm resolution for a clinically realistic 99mTc activity concentration in an 11-minute scan, while in breast phantoms the smallest spheres visible were 6 mm in diameter for the same scan time. To conclude, the experimental results of the novel MP-MBT scanner showed that the setup had sub-centimetre breast tumour detection capability which might facilitate 3D molecular breast cancer imaging in the future.

Calibration of Robotic Manipulator Systems for Cone-Beam Tomography Imaging

Image reconstruction of tomographic data relies on the precise knowledge of the geometric properties of the scan system. Common tomography systems, such as rotational tomography, C-arm systems, helical scanners, or tomosynthesis scanners, generally use motions described by a few rotational or linear motion axes. We are interested in applications in nondestructive testing, where objects might have large aspect ratios and complex shapes. For these problems, more complex scan trajectories are required, which can be achieved with robotic manipulator systems that have several linear or rotational degrees of freedom. For the geometric calibration of our system, instead of using an approach that scans a calibrated phantom with markers at a known relative position, we propose an approach that uses one (or several) markers with unknown relative positions. The fiducial marker is then moved by a known amount along one degree of freedom, thus tracing out a “virtual” phantom. Using the assumed spacial locations of the markers together with the locations of the markers on the imaging plane, we use a nonlinear optimization method to estimate the orientation of the linear and rotational manipulator axes, the detector and source location, and the detector orientation.

Design and development of a phantom for tomosynthesis with potential for automated analysis via the cloud.

This paper describes Development of a Phantom for Tomosynthesis with Potential for Automated Analysis via the Cloud. Several studies are underway to investigate the effectiveness of Tomosynthesis Mammographic Image Screening, including the large TMIST project as funded by the National Cancer Institute https://www.cancer.gov/about-cancer/treatment/clinical-trials/nci-supported/tmist. The development of the phantom described in this paper follows initiatives from the FDA, the AAPM TG245 task group, and European Reference Organization (EUREF) for Quality Assured Breast Screening and Diagnostic Services Committee report noting, that no formal endorsement nor recommendation for use has been sought, or granted by any of these groups. This paper reports on the possibility of using this newly developed Tomosynthesis Phantom for Quality Assurance, field testing of image performance, including remote monitoring of DBT system performance, e.g., via transmission over the cloud. The phantom includes tests for: phantom positioning and alignment (important for remote analysis), scan geometry (x and y), chest wall offset, scan slice width and Slice Sensitivity Profile (SSP(z)) slice geometry (slice width), scan slice incrementation (z), z axis geometry bead, low contrast detectability using low contrast spheres, spatial resolution via Point Spread Function (PSF), Image uniformity, Signal to Noise Ratio (SNR), and Contrast to Noise Ratio (CNR) via readings over an Aluminum square. The phantom is designed for use with automated analysis via transmission of images over the cloud and the analysis package includes test of positioning accuracy (roll, pitch, and yaw). Data are shown from several commercial Tomosynthesis Scanners including Fuji, GE, Hologic, IMS‐Giotti, and Siemens; however, the focus of this paper is on phantom design, and not in general aimed at direct commercial comparisons, and wherever possible the identity of the data is anonymized. Results of automated analysis of the phantom are shown, and it is demonstrated that reliable analysis of such a phantom can be achieved remotely, including transmission of data through the cloud.

Mathematical observer for 3D radiographic scanner design

• A statistical framework for assessing scanner performance on lesion detectability. • Model observers for evaluating clinical relevant designs through imaging chain. • Enable anatomical considerations to detailed design of 3D radiographic scanner. In the engineering processes of medical 3D radiographic scanner, detailed design elaborates each aspect of the device with complete descriptions, which may include operating parameters as well as the scanner specifications. For assessing the developments mathematically and objectively, task-based approaches are advocated for the optimization of image quality through the scanner design and imaging parameters. In this paper, we present a framework for assessing tomosynthesis scanner performance in lung lesion signal detectability through imaging parameters such as projection frames, lesion depths and anatomical background by using Hotelling observer (HO). Moreover, a channelized Hotelling observer (CHO) with efficient choices of non-linear iterative partial least squares (NIPALS) channels is implemented to reduce the large data dimensionality for computations. Area under the receiver operating characteristic curve (AUC) is computed as an objective figure-of-merit for the performance measurement that described the entire imaging chain. The presented framework is validated with our laboratory x-ray scanner and an anthropomorphic chest phantom. In our result, the performance is evaluated as functions of AUC to the imaging parameters. Performance map shows 5 mm lung lesion detectability is worsened with cardiac projection-overlapping. Scanner performance is highly related to anatomical structures at the image background. The developed framework has presented its value on assess tomosynthesis scanner performance through anthropomorphic phantom imaging. It can be an objective method for determining scanner detailed design and imaging parameters.

Effects on image quality of a 2D antiscatter grid in x-ray digital breast tomosynthesis: Initial experience using the dual modality (x-ray and molecular) breast tomosynthesis scanner.

Radiation scattered from the breast in digital breast tomosynthesis (DBT) causes image degradation, including loss of contrast between cancerous and background tissue. Unlike in 2-dimensional (2D) mammography, an antiscatter grid cannot readily be used in DBT because changing alignment between the tube and detector during the scan would result in unacceptable loss of primary radiation. However, in the dual modality breast tomosynthesis (DMT) scanner, which combines DBT and molecular breast tomosynthesis, the tube and detector rotate around a common axis, thereby maintaining a fixed tube-detector alignment. This C-arm geometry raises the possibility of using a 2D (cellular) focused antiscatter grid. The purpose of this study is to assess change in image quality when using an antiscatter grid in the DBT portion of a DMT scan under conditions of fixed radiation dose. Two 2D focused prototype grids with 80 cm focal length were tested, one stack-laminated from copper (Cu) and one cast from a tungsten-polymer (W-poly). They were reciprocated using a motion scheme designed to maximize transmission of primary x-ray photons. Grid-in and grid-out scatter-to-primary ratios (SPRs) were measured for rectangular blocks of material simulating 30%, 50%, and 70% glandular tissue compositions. For assessment of changes in image quality through the addition of a grid, the Computerized Imaging Reference Systems, Inc., phantom Model 011A containing a set of 1 cm thick blocks simulating a range of glandular/adipose ratios from 0/100 to 100/0 was used. To simulate 6.5 and 8.5 cm thick compressed breasts, 1 cm thick slices of PMMA were added to the Model 011A phantom. DBT images were obtained with and without the grid, with exposure parameters fixed for a given compressed thickness. Signal-difference-to-noise ratios (SDNRs), contrast, and voxel value-based attenuation coefficients (μ) were measured for all blocks from reconstructed phantom images. For 4, 6, and 8 cm tissue-equivalent block phantom thicknesses, the inclusion of the W-poly grid reduced the SPR by factors of 5, 6, and 5.8, respectively. For the same thicknesses, the copper grid reduced the SPR by factors of 3.9, 4.5, and 4.9. For the 011A phantom, the W-poly grid raised the SDNR of the 70/30 block from 0.8, -0.32, and -0.72 to 0.9, 0.76, and 0.062 for the 4.5, 6.5, and 8.5 cm phantoms, respectively. It raised the SDNR of the 100/0 block from 3.78, 1.95, and 1.0 to 3.79, 3.67, and 3.25 for the 4.5, 6.5, and 8.5 cm phantoms, respectively. Inclusion of the W-poly grid improved the accuracy of image-based μ values for all block compositions. However, smearing of attenuation across slices due to limited angular sampling decreases the sensitivity of voxel values to changing composition compared to theoretical μ values. Under conditions of fixed radiation dose to the breast, use of a 2D focused grid increased contrast, SDNR, and accuracy of estimated attenuation for mass-simulating block compositions in all phantom thicknesses tested, with the degree of improvement depending upon material composition. A 2D antiscatter grid can be usefully incorporated in DBT systems that employ fully isocentric tube-detector rotation.

MO‐D‐201B‐01: Carbon Nanotube X‐Ray: Promises and Challenges

Purpose: To develop a carbon nanotube based field emission x‐ray technology for medical imaging and radiation therapy Method and Materials: Carbon nanotubes (CNTs) are used as the field emission “cold cathode”. The x‐ray tube current is generated by applying an external electrical field to extract the electrons from the CNTs. By varying the extraction electrical field, x‐ray radiation with programmable waveforms can be readily generated and gated with physiological signals. Spatially distributed x‐ray source arrays with one‐ and two‐ dimensionally distributed focal spots are constructed by using matrix addressable multi‐pixel CNT cathode. Switching, scanning, and regulating the x‐ray beams are achieved by specially designed gate control electronics. Results: Programmable and spatially distributed field emission x‐ray source arrays have been developed. After substantial R&amp;D efforts these x‐ray sources are now capable of delivering the spatial resolution, the x‐ray flux, and the energy required for medical imaging applications. Utilizing the rapid programmable capability of the CNT field emission source, a prospective respiratory and cardiac gated micro‐CT scanner has been developed that is capable of high‐resolution in vivo imaging of free‐breathing small animals. A proof‐of‐concept stationary digital breast tomosynthesis scanner with a distributed multi‐beam x‐ray source array has been demonstrated which collects project images without mechanical motion and has the potential to substantially reduce the scanning time and therefore motion blurs. Utilizing the capability of distributing the x‐ray power over a large focusing track instead of small spot on the anode, a compact high dose and dose rate microbeam radiation therapy system is currently under development at UNC. Conclusion: The distributed field emission x‐ray source array technology offers unique capabilities that are attractive for tomography imaging and potentially for radiotherapy. The flexibility in source configuration opens up new possibilities in system design. As a brand new source technology, issues such as reliable and long term stability which are critical for commercial products need further investigation and improvement.Conflict of Interest: Zhou is a board director of XinRay Systems which develops and commercializes the CNT X‐Ray source technology.