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PubMed | Friedrich - Alexander - University, Erlangen - Nuremberg, CT Imaging GmbH and Explius GmbH
Type: Journal Article | Journal: Journal of medical imaging (Bellingham, Wash.) | Year: 2015

Various applications require information on breast parameters, such as breast length and volume. An optical system was designed and tested for measuring these parameters with subjects in a prone position. The study results were used for optimizing patient positioning and handling for a future breast computed tomography (BCT) system. Measurements were conducted using an optical measurement system. To test the functionality and accuracy of the system, measurements were performed using reference phantoms. Additionally, 20 women and 5 men were examined to calculate breast parameters in alternative positions and breathing states. The results of the optical measurements were compared with magnetic resonance imaging (MRI) measurements. Volume and length of the reference phantoms were determined with errors below 2%. The patient study demonstrated a mean breast volume of 530.7ml for women during normal breathing. During an exhalation state, breast volume increased significantly by 17.7ml in comparison with normal breathing. Differences with MRI measurements were found to be 3% for breast length and 9% for breast volume on average. The proposed optical measurement system was found to be suitable for measuring the dimensional parameters of the breast in a prone position and provides a tool for evaluating breast coverage for BCT.

Agency: Cordis | Branch: FP7 | Program: CP-FP | Phase: HEALTH-2007-1.2-1;HEALTH-2007-1.2-2 | Award Amount: 5.84M | Year: 2008

This proposal offers to combine X-ray CT (XCT) and Fluorescence Molecular Tomography (FMT) into a hybrid, quantitative system and method. The project builds on state-of the-art knowledge that only recently became available in different European states as represented by the partners herein. In return it delivers the first such hybrid system worldwide. The system will operate by 1) co-registering XCT images with highly performing FMT images for merging anatomical, functional and molecular contrast and by 2) combining XCT information into the FMT inversion to provide a system with superior imaging performance. XCT-based correction, as explained in this proposal, can improve FMT performance in a more radical way than corresponding correction methods used for improving PET or SPECT images. In this way FMT-XCT can reach the imaging accuracy of radio-nuclei-based tomography hybrid systems. By using fluorescence, FMT-XCT can then enable high flexibility in targeting physiology and molecular function, especially in multi-spectral mode, and high dissemination potential because virtually any biomedical laboratory has access to fluorescence reporting, compared to radio-nuclei based research that requires access to radiochemistry and cyclotron facilities. FMT-XCT aims in advancing small animal imaging and drug discovery with a view towards the clinical application on non-invasive breast cancer imaging. For this reason, focus herein is given to imaging breast cancer and response to therapy. Overall the technology is ideally suited for commercial translation and has the potential to become the method of choice for in-vivo imaging in most biomedical laboratories and in select clinical applications. While it appreciates the value of nuclear imaging methods, this proposal will hopefully raise the funding necessary to establish on European ground a new potent paradigm of in-vivo imaging with high dissemination and application potential and large social and health-care impact .

Kalender W.A.,Friedrich - Alexander - University, Erlangen - Nuremberg | Kalender W.A.,CT Imaging GmbH | Kolditz D.,Friedrich - Alexander - University, Erlangen - Nuremberg | Kolditz D.,CT Imaging GmbH | And 7 more authors.
European Radiology | Year: 2016

Abstract: X-ray computed tomography (CT) has been proposed and evaluated multiple times as a potentially alternative method for breast imaging. All efforts shown so far have been criticized and partly disapproved because of their limited spatial resolution and higher patient dose when compared to mammography. Our concept for a dedicated breast CT (BCT) scanner therefore aimed at novel apparatus and detector design to provide high spatial resolution of about 100 μm and average glandular dose (AGD) levels of 5 mGy or below. Photon-counting technology was considered as a solution to reach these goals. The complete concept was previously evaluated and confirmed by simulations and basic experiments on laboratory setups. We here present measurements of dose, technical image quality parameters and surgical specimen results on such a scanner. For comparison purposes, the specimens were also imaged with digital mammography (DM) and breast tomosynthesis (BT) apparatus. Results show that photon-counting BCT (pcBCT) at 5 mGy AGD offers sufficiently high 3D spatial resolution for reliable detectability of calcifications and soft tissue delineation. Key points: • Photon-counting detector technology allows for spatial resolution better than 100 μm.• pcBCT allows for dose levels in the screening mammography range.• pcBCT provides the highest quality imaging of microcalcifications. © 2016 European Society of Radiology

Steiding C.,Friedrich - Alexander - University, Erlangen - Nuremberg | Kolditz D.,Friedrich - Alexander - University, Erlangen - Nuremberg | Kalender W.A.,CT Imaging GmbH
Medical Physics | Year: 2014

Purpose: Thousands of cone-beam computed tomography (CBCT) scanners for vascular, maxillofacial, neurological, and body imaging are in clinical use today, but there is no consensus on uniform acceptance and constancy testing for image quality (IQ) and dose yet. The authors developed a quality assurance (QA) framework for fully automated and time-efficient performance evaluation of these systems. In addition, the dependence of objective Fourier-based IQ metrics on direction and position in 3D volumes was investigated for CBCT. Methods: The authors designed a dedicated QA phantom 10 cm in length consisting of five compartments, each with a diameter of 10 cm, and an optional extension ring 16 cm in diameter. A homogeneous section of water-equivalent material allows measuring CT value accuracy, image noise and uniformity, and multidimensional global and local noise power spectra (NPS). For the quantitative determination of 3D high-contrast spatial resolution, the modulation transfer function (MTF) of centrally and peripherally positioned aluminum spheres was computed from edge profiles. Additional in-plane and axial resolution patterns were used to assess resolution qualitatively. The characterization of low-contrast detectability as well as CT value linearity and artifact behavior was tested by utilizing sections with soft-tissue-equivalent and metallic inserts. For an automated QA procedure, a phantom detection algorithm was implemented. All tests used in the dedicated QA program were initially verified in simulation studies and experimentally confirmed on a clinical dental CBCT system. Results: The automated IQ evaluation of volume data sets of the dental CBCT system was achieved with the proposed phantom requiring only one scan for the determination of all desired parameters. Typically, less than 5 min were needed for phantom set-up, scanning, and data analysis. Quantitative evaluation of system performance over time by comparison to previous examinations was also verified. The maximum percentage interscan variation of repeated measurements was less than 4% and 1.7% on average for all investigated quality criteria. The NPS-based image noise differed by less than 5% from the conventional standard deviation approach and spatially selective 10% MTF values were well comparable to subjective results obtained with 3D resolution pattern. Determining only transverse spatial resolution and global noise behavior in the central field of measurement turned out to be insufficient. Conclusions: The proposed framework transfers QA routines employed in conventional CT in an advanced version to CBCT for fully automated and time-efficient evaluation of technical equipment. With the modular phantom design, a routine as well as an expert version for assessing IQ is provided. The QA program can be used for arbitrary CT units to evaluate 3D imaging characteristics automatically. © 2014 American Association of Physicists in Medicine.

Luck F.,Friedrich - Alexander - University, Erlangen - Nuremberg | Luck F.,CT Imaging GmbH | Kolditz D.,Friedrich - Alexander - University, Erlangen - Nuremberg | Kolditz D.,CT Imaging GmbH | And 4 more authors.
Physics in Medicine and Biology | Year: 2013

The purpose of this study was to investigate the effect of shaped filters specifically designed for dedicated breast computed tomography (CT) scanners on dose and image quality. Optimization of filter shape and material in fan direction was performed using two different design methods, one aiming at homogeneous noise distributions in the CT images and the other aiming at a uniform dose distribution in the breast. The optimal filter thickness as a function of fan angle was determined iteratively to fulfil the above mentioned criteria for each breast diameter. Different filter materials (aluminium, copper, carbon, polytetrafluoroethylene) and breast phantoms with diameters between 80-180 mm were investigated. Noise uniformity in the reconstructed images, obtained from CT simulations based on ray-tracing methods, and dose in the breast, calculated with a Monte Carlo software tool, were used as figure of merit. Furthermore, CT-value homogeneity, the distribution of noise in cone direction, spatial resolution from centre to periphery and the contrast-to-noise ratio weighted by dose (CNRD) were evaluated. In addition, the decrease of scatter due to shaped filters was investigated. Since only few or one filter are practical in clinical CT systems, the effects of one shaped filter for different breast diameters were also investigated. In this case the filter, designed for the largest breast diameter, was simulated at variable source-to-filter distances depending on breast diameter. With the filter design method aiming at uniform noise distribution best results were obtained for aluminium as the filter material. Noise uniformity improved from 20} down to 5} and dose was reduced by about 30-40} for all breast diameters. No decrease of noise uniformity in cone direction, CT-value homogeneity, spatial resolution and the CNRD was detected with the shaped filter. However, a small improvement of CNRD was observed. Furthermore, a scatter reduction of about 20-30} and a more homogeneous scatter distribution were reached which led to reduced cupping artefacts. The simulations with one shaped filter at variable source-to-filter distance resulted in nearly homogeneous noise distributions and comparable dose reduction for all breast diameters. In conclusion, by means of shaped filters designed for breast CT, significant dose reduction can be achieved at unimpaired image quality. One shaped filter designed for the largest breast diameter used with variable source-to-filter distance appears to be the best solution for breast CT. © 2013 Institute of Physics and Engineering in Medicine.

Kuttig J.D.,Friedrich - Alexander - University, Erlangen - Nuremberg | Steiding C.,Friedrich - Alexander - University, Erlangen - Nuremberg | Steiding C.,CT Imaging GmbH | Kolditz D.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 6 more authors.
Physica Medica | Year: 2015

Purpose: To investigate the dose saving potential of direct-converting CdTe photon-counting detector technology for dedicated breast CT. Materials and methods: We analyzed the modulation transfer function (MTF), the noise power spectrum (NPS) and the detective quantum efficiency (DQE) of two detector technologies, suitable for breast CT (BCT): a flat-panel energy-integrating detector with a 70μm and a 208μm thick gadolinium oxysulfide (GOS) and a 150μm thick cesium iodide (CsI) scintillator and a photon-counting detector with a 1000μm thick CdTe sensor. Results: The measurements for GOS scintillator thicknesses of 70μm and 208μm delivered 10% pre-sampled MTF values of 6.6mm-1 and 3.2mm-1, and DQE(0) values of 23% and 61%. The 10% pre-sampled MTF value for the 150μm thick CsI scintillator 6.9mm-1, and the DQE(0) value was 49%. The CdTe sensor reached a 10% pre-sampled MTF value of 8.5mm-1 and a DQE(0) value of 85%. Conclusion: The photon-counting CdTe detector technology allows for significant dose reduction compared to the energy-integrating scintillation detector technology used in BCT today. Our comparative evaluation indicates that a high potential dose saving may be possible for BCT by using CdTe detectors, without loss of spatial resolution. © 2015 Associazione Italiana di Fisica Medica.

Sawall S.,Friedrich - Alexander - University, Erlangen - Nuremberg | Bergner F.,Friedrich - Alexander - University, Erlangen - Nuremberg | Lapp R.,CT Imaging GmbH | Mronz M.,CT Imaging GmbH | And 3 more authors.
Medical Physics | Year: 2011

Purpose: Micro-CT imaging of animal hearts typically requires a double gating procedure because scans during a breath-hold are not possible due to the long scan times and the high respiratory rates. Simultaneous respiratory and cardiac gating can either be done prospectively or retrospectively. True five-dimensional information can be either retrieved with retrospective gating or with prospective gating if several prospective gates are acquired. In any case, the amount of information available to reconstruct one volume for a given respiratory and cardiac phase is orders of magnitude lower than the total amount of information acquired. For example, the reconstruction of a volume from a 10% wide respiratory and a 20% wide cardiac window uses only 2% of the data acquired. Achieving a similar image quality as a nongated scan would therefore require to increase the amount of data and thereby the dose to the animal by up to a factor of 50. Methods: To achieve the goal of low-dose phase-correlated (LDPC) imaging, the authors propose to use a highly efficient combination of slightly modified existing algorithms. In particular, the authors developed a variant of the McKinnon-Bates image reconstruction algorithm and combined it with bilateral filtering in up to five dimensions to significantly reduce image noise without impairing spatial or temporal resolution. Results: The preliminary results indicate that the proposed LDPC reconstruction method typically reduces image noise by a factor of up to 6 (e.g., from 170 to 30 HU), while the dose values lie in a range from 60 to 500 mGy. Compared to other publications that apply 250-1800 mGy for the same task [C. T. Badea, "4D micro-CT of the mouse heart," Mol. Imaging 4(2), 110-116 (2005); M. Drangova, "Fast retrospectively gated quantitative four-dimensional (4D) cardiac micro computed tomography imaging of free-breathing mice," Invest. Radiol. 42(2), 85-94 (2007); S. H. Bartling, "Retrospective motion gating in small animal CT of mice and rats," Invest. Radiol. 42(10), 704-714 (2007)], the authors' LDPC approach therefore achieves a more than tenfold dose usage improvement. Conclusions: The LDPC reconstruction method improves phase-correlated imaging from highly undersampled data. Artifacts caused by sparse angular sampling are removed and the image noise is decreased, while spatial and temporal resolution are preserved. Thus, the administered dose per animal can be decreased allowing for long term studies with reduced metabolic inference. © 2011 American Association of Physicists in Medicine.

Kyriakou Y.,Friedrich - Alexander - University, Erlangen - Nuremberg | Meyer M.,Friedrich - Alexander - University, Erlangen - Nuremberg | Lapp R.,CT Imaging GmbH | Kalender W.A.,Friedrich - Alexander - University, Erlangen - Nuremberg
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2010

Typical cupping correction methods are pre - processing methods which require either pre-calibration measurements or simulations of standard objects to approximate and correct for beam hardening and scatter. Some of them require the knowledge of spectra, detector characteristics, etc. The aim of this work was to develop a practical histogram- driven cupping correction (HDCC) method to post process the reconstructed images. We use a polynomial representation of the raw- data generated by forward projection of the reconstructed images; forward amid back-projection are performed on graphics processing units (GPU). The coefficients of the polynomial are optimized using a simplex minimization of the joint entropy of the CT image and its gradient. The algorithm was evaluated using simulations and measurements of homogeneous and inhomogeneous phantoms. For the measurements a C arm flat-detector CT (FD CT) system with a 30×40 cm2 detector, a kilovoltage on board imager (radiation therapy simulator) and a micro-CT system were used. The algorithm reduced cupping artifacts both in simulations and measurements using a fourth-order polynomial and was in good agreement to the reference. The minimization algorithm required less than 70 iterations to adjust the coefficients only performing a linear combination of basis images, thus executing without time consuming operations. HDCC reduced cupping artifacts without the necessity of pre-calibration or other scan information enabling a retrospective improvement of CT image homogeneity. However, the method can work with other cupping correction algorithms or in a calibration manner, as well. © 2010 SPIE.

Agency: Cordis | Branch: FP7 | Program: CP | Phase: Fission-2007-3.2-01 | Award Amount: 2.71M | Year: 2008

Early and accurate diagnosis of breast cancer in women is a pending challenge. Digital x-ray mammography is considered todays state of the art in diagnosis although severe insufficiencies are acknowledged. Conventional film-screen mammography, digital tomosynthesis, ultrasound, nuclear medicine and magnetic resonance imaging are also in use or under investigation. There is a general consensus that 3D imaging could offer significant advantages. Dedicated x-ray computed tomography (CT) of the female breast without exposure of the body trunk appears to be a further candidate with improved diagnostic capabilities, but radiation protection issues have to be solved. In consequence, this project focuses on the development of a dedicated scanner using novel technology and optimisation strategies. We intend to prove the feasibility of CT of the breast with very high spatial resolution of 100 m or better and high soft-tissue differentiation at dose levels equal to or below those of two-view digital mammography. First simulation studies support the concept. To allow for balanced conclusions on justification of practice and risk assessment, the performance of breast CT will be validated and compared against digital mammography and tomosynthesis primarily, but also against any other novel approach. To achieve the proposed goals three European scientific institutes of international reputation and two manufactures with the respective know-how have formed a consortium. The necessary equipment, tools, test and measurement approaches are available; new multi-modality tests have to be developed for a meaningful comparison of 2D and 3D imaging. It is our intention to provide proofs of concept and results on breast CT in the relatively short time span of 30 months. Pending on the results of the project outlined here, a multimodality clinical study with an extended European consortium is planned as a follow-up.

PubMed | Friedrich - Alexander - University, Erlangen - Nuremberg, CT Imaging GmbH and Siemens AG
Type: Journal Article | Journal: Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB) | Year: 2014

The estimation of patient dose using Monte Carlo (MC) simulations based on the available patient CT images is limited to the length of the scan. Software tools for dose estimation based on standard computational phantoms overcome this problem; however, they are limited with respect to taking individual patient anatomy into account. The purpose of this study was to generate whole-body patient models in order to take scattered radiation and over-scanning effects into account. Thorax examinations were performed on three physical anthropomorphic phantoms at tube voltages of 80kV and 120kV; absorbed dose was measured using thermoluminescence dosimeters (TLD). Whole-body voxel models were built as a combination of the acquired CT images appended by data taken from widely used anthropomorphic voxel phantoms. MC simulations were performed both for the CT image volumes alone and for the whole-body models. Measured and calculated dose distributions were compared for each TLD chip position; additionally, organ doses were determined. MC simulations based only on CT data underestimated dose by 8%-15% on average depending on patient size with highest underestimation values of 37% for the adult phantom at the caudal border of the image volume. The use of whole-body models substantially reduced these errors; measured and simulated results consistently agreed to better than 10%. This study demonstrates that combined whole-body models can provide three-dimensional dose distributions with improved accuracy. Using the presented concept should be of high interest for research studies which demand high accuracy, e.g. for dose optimization efforts.

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