Digital Mammography with a Mosaic of CCD-Arrays

The present invention relates generally to a mammography device and method and more particularly to a novel digital mammography device and method to detect microcalcifications of precancerous tissue. A digital mammography device uses a mosaic of electronic digital imaging arrays to scan an x-ray image. The mosaic of arrays is repositioned several times to expose different portions of the image, until the entire image is scanned. The data generated by the arrays during each exposure is stored in a computer. After the final exposure, the computer combines data of the several partial images to produce a composite of the original x-ray image. An aperture plate is used to reduce scatter and the overall exposure of the patient to x-rays. The novelty of this invention is that it provides a digital mammography device with large field coverage, high spatial resolution, scatter rejection, excellent contrast characteristics and lesion detectability under clinical conditions. This device also shields the patient from excessive radiation, can detect extremely small calcifications and allows manipulation and storage of the image

Digital Mammography with a Mosaic of CCD Arrays

A digital mammography device uses a mosaic of electronic digital imaging arrays to scan an x-ray image is discussed. The mosaic of arrays is repositioned several times to expose different portions of the image, until the entire image is scanned. The data generated by the arrays during each exposure is stored in a computer. After the final exposure, the computer combines data of the several partial images to produce a composite of the original x-ray image. An aperture plate is used to reduce scatter and the overall exposure of the patient to x-rays

An investigation of the imaging performance of CCD based x-ray detectors for digital mammography

This thesis describes the imaging performance of a prototype digital mammography system based upon charge coupled devices (CCDs). The imaging performance of these detectors is dependent upon the configuration of the detector. In this thesis the performance of 14 different detector configurations are studied for use in digital mammography. Experimental evaluations of factors which affect the performance of imaging systems such as quantum detection efficiency, dynamic range, modulation transfer function (MTF(f)) and Noise power spectrum (NPS) were performed. The use of spatial frequency dependent detective quantum efficiency DQE(f) to characterise the detectors in terms of signal to noise ratio transfer is described. It is shown that direct interactions of x-rays in the CCD act to reduce DQE(f) at high spatial frequencies and severely impair the detectors ability to detect small objects (250|im in diameter). The use of a sufficient thickness of fibre optic faceplate to couple the phosphor layer to the CCD is shown to remove these interactions and shows a corresponding increase in DQE(f) (at higher spatial frequencies) and the detector's ability to image smaller objects A subjective comparison of images of a breast phantom shows that images of superior quality were obtained with the prototype system compared with images produced using a conventional film-screen system, for a slight increase in dose. Improvements to the system and detector design are presented and will act to try to produce the same image quality for equivalent doses used in conventional mammography

High-resolution fluorescence endomicroscopy for rapid evaluation of breast cancer margins

Breast cancer is a major public health problem world-wide and the second leading cause of cancer-related female deaths. Breast conserving surgery (BCS), in the form of wide local excision (WLE), allows complete tumour resection while maintaining acceptable cosmesis. It is the recommended treatment for a large number of patients with early stage disease or, in more advanced cases, following neoadjuvant chemotherapy. About 30% of patients undergoing BCS require one or more re-operative interventions, mainly due to the presence of positive margins. The standard of care for surgical margin assessment is post-operative examination of histopathological tissue sections. However, this process is invasive, introduces sampling errors and does not provide real-time assessment of the tumour status of radial margins. The objective of this thesis is to improve intra-operative assessment of margin status by performing optical biopsy in breast tissue. This thesis presents several technical and clinical developments related to confocal fluorescence endomicroscopy systems for real-time characterisation of different breast morphologies. The imaging systems discussed employ flexible fibre-bundle based imaging probes coupled to high-speed line-scan confocal microscope set-up. A preliminary study on 43 unfixed breast specimens describes the development and testing of line-scan confocal laser endomicroscope (LS-CLE) to image and classify different breast pathologies. LS-CLE is also demonstrated to assess the intra-operative tumour status of whole WLE specimens and surgical excisions with high diagnostic accuracy. A third study demonstrates the development and testing of a bespoke LS-CLE system with methylene blue (MB), an US Food and Drug Administration (FDA) approved fluorescent agent, and integration with robotic scanner to enable large-area in vivo imaging of breast cancer. The work also addresses three technical issues which limit existing fibre-bundle based fluorescence endomicroscopy systems: i) Restriction to use single fluorescence agent due to low-speed, single excitation and single fluorescence spectral band imaging systems; ii) Limited Field of view (FOV) of fibre-bundle endomicroscopes due to small size of the fibre tip and iii) Limited spatial resolution of fibre-bundle endomicroscopes due to the spacing between the individual fibres leading to fibre-pixelation effects. Details of design and development of a high-speed dual-wavelength LS-CLE system suitable for high-resolution multiplexed imaging are presented. Dual-wavelength imaging is achieved by sequentially switching between 488 nm and 660 nm laser sources for alternate frames, avoiding spectral bleed-through, and providing an effective frame rate of 60 Hz. A combination of hand-held or robotic scanning with real-time video mosaicking, is demonstrated to enable large-area imaging while still maintaining microscopic resolution. Finally, a miniaturised piezoelectric transducer-based fibre-shifting endomicroscope is developed to enhance the resolution over conventional fibre-bundle based imaging systems. The fibre-shifting endomicroscope provides a two-fold improvement in resolution and coupled to a high-speed LS-CLE scanning system, provides real-time imaging of biological samples at 30 fps. These investigations furthered the utility and applications of the fibre-bundle based fluorescence systems for rapid imaging and diagnosis of cancer margins.Open Acces

Si, CdTe and CdZnTe radiation detectors for imaging applications

The structure and operation of CdTe, CdZnTe and Si pixel detectors based on crystalline semiconductors, bump bonding and CMOS technology and developed mainly at Oy Simage Ltd. And Oy Ajat Ltd., Finland for X- and gamma ray imaging are presented. This detector technology evolved from the development of Si strip detectors at the Finnish Research Institute for High Energy Physics (SEFT) which later merged with other physics research units to form the Helsinki Institute of Physics (HIP). General issues of X-ray imaging such as the benefits of the method of direct conversion of X-rays to signal charge in comparison to the indirect method and the pros and cons of photon counting vs. charge integration are discussed. A novel design of Si and CdTe pixel detectors and the analysis of their imaging performance in terms of SNR, MTF, DQE and dynamic range are presented in detail. The analysis shows that directly converting crystalline semiconductor pixel detectors operated in the charge integration mode can be used in X-ray imaging very close to the theoretical performance limits in terms of efficiency and resolution. Examples of the application of the developed imaging technology to dental intra oral and panoramic and to real time X-ray imaging are given. A CdTe photon counting gamma imager is introduced. A physical model to calculate the photo peak efficiency of photon counting CdTe pixel detectors is developed and described in detail. Simulation results indicates that the charge sharing phenomenon due to diffusion of signal charge carriers limits the pixel size of photon counting detectors to about 250 μm. Radiation hardness issues related to gamma and X-ray imaging detectors are discussed.Työssä esitellään Suomessa kehitettyjä uudentyyppisiä digitaalisia röntgen- ja gammakuvausantureita, jotka perustuvat pii- ja CdTe-puolijohdeteknologiaan. Uuden tekniikan anturit osoitetaan toimivan hyvin lähellä teoreettista optimia. Erinomainen röntgenkuvan laatu saavutetaan pienellä säteilyannoksella. Antureiden rakenne ja toiminta selostetaan seikkaperäisesti ja niiden soveltamisesta hammaskuvaukseen ja reaaliaikaiseen videoröntgenkuvantamiseen annetaan esimerkkejä. Työssä esitellään myös fotonilaskentaan perustuvan CdTe gammakuvausanturin toiminta simuloinnein ja mittauksin sekä käsitellään antureiden säteilynkestoon liittyviä kysymyksiä

Imaging of the Breast

Early detection of breast cancer combined with targeted therapy offers the best outcome for breast cancer patients. This volume deal with a wide range of new technical innovations for improving breast cancer detection, diagnosis and therapy. There is a special focus on improvements in mammographic image quality, image analysis, magnetic resonance imaging of the breast and molecular imaging. A chapter on targeted therapy explores the option of less radical postoperative therapy for women with early, screen-detected breast cancers

K-edge Radiography and applications to Cultural Heritage

The present work of thesis is focused on application of X-ray K-edge technique to paintings. This technique allows one to achieve a topographic map of a pigment on the whole surface of the painting. The digital acquisition of radiographic images by using monochromatic X-ray beams allows to take advantage of the sharp rise of X-ray absorption coefficient of the elements, the K-edge discontinuity. Working at different energies, bracketing the K-edge peak, allows recognition of the target element. The K-edge radiography facility installed at Larix Laboratory, at Department of Physics in Ferrara, consists of a quasi-monochromatic X-ray beam obtained via Bragg diffraction on a mosaic crystal from standard X-ray source. In this work the K-edge technique and the facility used are illustrated. A characterization of the monochromatic beams in the energy range 7-40 KeV range and the elemental mapping on pictorial layers obtained are presented. At the end, a transportable facility for digital radiography is presented and some radiographic analysis of works of art performed are shown

A Prototype Computational Phantom to Create Digital Images for Research and Training in Diagnostic Radiology

Research in the processing, compression, transmission, and interpretation of digital radiographic images require the testing and evaluation of a wide variety of images, varying both in format and in spatial resolution. If receiver operating characteristic (ROC) analysis or a related method is used to evaluate the performance of observers using novel vs. conventional displays, large numbers of test images containing known abnormalities are required. This report describes a convenient, inexpensive, and reproducible source of test images, having any desired resolution and containing precisely defined abnormalities of unlimited subtlety. The images are generated by computing x-ray transmission through mathematically defined, three dimensional masses according to Beer\u27s Law. A procedure is presented for generating computer simulated chest radiographs and mammograms, which can contain various classes of abnormalities, including tumors, infiltrates, cavities, pleural effusions, cardiac chamber enlargement, and soft tissue calcifications. Test images can be created from simple computational models of superimposed spherical densities. The approach provides a flexible, inexpensive, easy-to-use research tool for investigators exploring digital techniques in diagnostic radiology. Such simulation software may also be of benefit as a training tool, when employed to generate numerous test images containing subtle abnormalities for programmed instruction and testing

Application of a novel CCD technology to medical imaging

This thesis describes an evaluation of a novel low light level charge couple device (L3CCD) technology. Two L3CCDs have been fully evaluated in terms of their signal and noise properties. The primary aim of this work is to identify the device characteristics that affect the overall performance. Conclusions have been made to this end and a prediction of the optimal performance in terms of the device sensitivity is made. Comparisons with other detectors suitable for use in medical imaging have shown that the L3CCD surpasses other detectors in specific performance characteristics and is comparable in others. The competitive performance of the L3CCD confirms that it may afford benefits in those areas in which the L3CCD has superior performance compared to other detectors. Two diagnostic imaging techniques which were identified as applications of L3CCD technology have been investigated. Linear systems analysis has been used to predict the performance of two L3CCD based imaging systems for use in fluoroscopic imaging. Comparison of the predicted performance of the two system with systems in clinical use show that an L3CCD coupled to an x-ray phosphor via a tapered fibre optic is a competitive alternative to present fluoroscopic imaging systems. Experimental validation of the model has confirmed this conclusion. An L3 detector has been designed, built and evaluated for diffraction enhanced breast imaging. To demonstrate the use of the L3 detector for diffraction enhanced breast imaging it has been used to acquire diffraction images of human breast tissue with cancerous inclusions. Measurements of scatter contrast confirm improvements in scatter contrast compared to transmission contrast. The successful demonstration of the L3CCDs ability to collect diagnostic information has shown that the L3CCD is suitable for diffraction enhanced breast imaging