Breast ultrasound tomography has the potential to improve the cost, safety, and reliability of breast cancer screening and diagnosis over the gold-standard of mammography. Vital to achieving this potential is the development of imaging algorithms to unravel the complex anatomy of the breast and its mechanical properties. The solution most commonly relied upon is time-of-flight tomography, but this exhibits low resolution due to the presence of diffraction effects. Iterative full-wave inversion methods present one solution to achieve higher resolution, but these are slow and are not guaranteed to converge to the correct solution. Presented here is HARBUT, the hybrid algorithm for robust breast ultrasound tomography, which utilizes the complementary strengths of time-of-flight and diffraction tomography resulting in a direct, fast, robust and accurate high resolution method of reconstructing the sound speed through the breast. The algorithm is shown to produce accurate reconstructions with realistic data from a complex three-dimensional simulation, with masses as small as 4 mm being clearly visible.

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High-resolution imaging without iteration: a fast and robust method for breast ultrasound tomography.

Lymphomas can arise within the central nervous system (CNS) as primary CNS lymphoma (PCNSL) typically involving the brain and less often the leptomeninges, eyes, and spinal cord. In contrast to PCNSL, secondary CNS lymphoma (SCNSL) is considered to originate as quasi metastasis from systemic lymphoma spreading to the CNS. Both types of CNS lymphomas are predominantly tumours of the diffuse large B-cell type and represent aggressive diseases necessitating a rapid diagnosis. Following neuroimaging based on magnetic resonance imaging, stereotaxy and histopathological diagnosis of CNS lymphoma currently remain obligatory to plan treatment. However, progress in cytopathological, immunophenotypic, and molecular genetic analyses of the cerebrospinal fluid (CSF) has been achieved recently and potentially will facilitate lymphoma diagnosis in the future. This review describes the diagnostic procedures in patients with suspected CNS lymphomas, primarily PCNSL. In addition to a summary of the standard diagnostic work-up, an overview and discussion of current data on different techniques for evaluation of the CSF in CNS lymphoma are given.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2141.2011.08928.x

Current strategies in the diagnosis of diffuse large B-cell lymphoma of the central nervous system.

OBJECTIVES The goal of this work was to obtain and evaluate measurements of tissue sound speed in the breast, particularly dense breasts, using backscatter ultrasound tomography. METHODS An automated volumetric breast ultrasound scanner was constructed for imaging the prone patient. A 5- to 7-MHz linear array transducer acquired 17,920 radiofrequency pulse echo A-lines from the breast, and a back-wall reflector rotated over 360° in 25 seconds. Sound speed images used reflector echoes that after preprocessing were uploaded into a graphics processing unit for filtered back-projection reconstruction. A velocimeter also was constructed to measure the sound speed and attenuation for comparison to scanner performance. Measurements were made using the following: (1) deionized water from 22°C to 90°C; (2) various fluids with sound speeds from 1240 to 1904 m/s; (3) acrylamide gel test objects with features from 1 to 15 mm in diameter; and (4) healthy volunteers. RESULTS The mean error ± SD between sound speed reference and image data was -0.48% ± 9.1%, and the error between reference and velocimeter measurements was -1.78% ± 6.50%. Sound speed image and velocimeter measurements showed a difference of 0.10% ± 4.04%. Temperature data showed a difference between theory and imaging performance of -0.28% ± 0.22%. Images of polyacrylamide test objects showed detectability of an approximately 1% sound speed difference in a 2.4-mm cylindrical inclusion with a contrast to noise ratio of 7.9 dB. CONCLUSIONS An automated breast scanner offers the potential to make consistent automated tomographic images of breast backscatter, sound speed, and attenuation, potentially improving diagnosis, particularly in dense breasts.

Imaging of Sound Speed Using Reflection Ultrasound Tomography

The paper is focused on sound-speed image reconstruction in 3-D ultrasound transmission tomography. Along with ultrasound reflectivity and the attenuation coefficient, sound speed is an important parameter which is related to the type and pathological state of the imaged tissue. This is important in the intended application, breast cancer diagnosis. In contrast to 2-D ultrasound transmission tomography systems, a 3-D system can provide an isotropic spatial resolution in the x-, y-, and z-directions in reconstructed 3-D images of ultrasound parameters. Several challenges must, however, be addressed for 3-D systems-namely, a sparse transducer distribution, low signal-to-noise ratio, and higher computational complexity. These issues are addressed in terms of sound-speed image reconstruction, using edge-preserving regularized algebraic reconstruction in combination with synthetic aperture focusing. The critical points of the implementation are also discussed, because they are crucial to enable a complete 3-D image reconstruction. The methods were tested on a synthetic data set and on data sets measured with the Karlsruhe 3-D ultrasound computer tomography (USCT) I prototype using phantoms. The sound-speed estimates in the reconstructed volumes agreed with the reference values. The breast-phantom outlines and the lesion-mimicking objects were also detectable in the resulting sound-speed volumes.

Sound-speed image reconstruction in sparse-aperture 3-D ultrasound transmission tomography

Full noncontact laser ultrasound (LUS) imaging has several distinct advantages over current medical ultrasound (US) technologies: elimination of the coupling mediums (gel/water), operator-independent image quality, improved repeatability, and volumetric imaging. Current light-based ultrasound utilizing tissue-penetrating photoacoustics (PA) generally uses traditional piezoelectric transducers in contact with the imaged tissue or carries an optical fiber detector close to the imaging site. Unlike PA, the LUS design presented here minimizes the optical penetration and specifically restricts optical-to-acoustic energy transduction at the tissue surface, maximizing the generated acoustic source amplitude. With an appropriate optical design and interferometry, any exposed tissue surfaces can become viable acoustic sources and detectors. LUS operates analogously to conventional ultrasound but uses light instead of piezoelectric elements. Here, we present full noncontact LUS results, imaging targets at ~5 cm depths and at a meter-scale standoff from the target surface. Experimental results demonstrating volumetric imaging and the first LUS images on humans are presented, all at eye- and skin-safe optical exposure levels. The progression of LUS imaging from tissue-mimicking phantoms, to excised animal tissue, to humans in vivo is shown, with validation from conventional ultrasound images. The LUS system design insights and results presented here inspire further LUS development and are a significant step toward the clinical implementation of LUS. A technology that delivers ultrasound images of living tissue without directly touching the target has undergone successful human testing for the first time. The need to contact a patient’s skin with conventional sound-sensitive piezoelectric devices can cause errors in ultrasound imaging when operators apply different amounts of pressure. Xiang Zhang and Brian Anthony from the Massachusetts Institute of Technology, in Cambridge, United States, and colleagues have designed a system that overcomes these limitations by using lasers to create and listen to ultrasound. The new method uses pulsed light to excite a thin upper portion of skin, producing acoustic waves that penetrates deeply into tissue. The ultrasound that scatters back to the surface is then detected with a laser interferometer. Noncontact imaging of 3D objects, animal tissue, and human volunteers detected features comparable to conventional ultrasound.

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Full noncontact laser ultrasound: first human data.

MRI patterns in recurrence of primary CNS lymphoma in immunocompetent patients

For the detection of breast cancer, ultrasound is conventionally used in addition to mammography However, ultrasound is highly operator-dependent since speckle, depth dependency and other artifacts (eg shadowing) affect image quality Full Angle Spatial Compounding (FASC) may overcome those limitations by superimposing ultrasound data acquired in one cross-sectional plane from aspect angles all around an object Furthermore, we showed in vitro that FASC also improves contrast perfusion imaging To apply FASC to breast imaging, we developed an add-on system to a conventional ultrasound scanner, integrated in a custom-made examination couch Here, we present first in-vivo results from test persons and patients with breast lesions

Ultrasound breast imaging using Full Angle Spatial Compounding: In-vivo results

PURPOSE: To test a system using ultrasound computed tomography (USCT) that superimposes ultrasound data acquired in one cross-sectional plane from multiple angles around the breast (Full Angle Spatial Compounding, FASC) and to reconstruct the distribution of the speed of sound in the breast (SoS reconstruction). MATERIALS AND METHODS: We developed a system combining a conventional ultrasound scanner with a PC-controlled mechanical setup integrated in a custom-made examination couch. In a feasibility study, 3 volunteers (age 26 – 74 years) and one patient with breast cancer were studied. Subjects were placed in the prone position on this couch, with the breast hanging in a water tank. The ultrasound probe was moved in several planes around the breast. A curved reflector that followed the movement of the probe behind the breast was used to calculate the SoS within the breast tissue. Echo-data was processed offline by custom-made software to calculate both FASC and SoS images. RESULTS: In FASC images a reduction of artifacts (i. e. shadowing of Cooper’s ligaments and irregular edges of inhomogeneous lesions) and speckles as well as clear visualization of the inner architecture of the breast was achieved. SoS images delivered further diagnostic information and helped to compensate for geometric distortions in the computed images. Difficulties in the visualization of lesions near the thoracic wall and/or the axillary are limitations of this technique. CONCLUSION: The first clinical results of USCT imaging have proven its feasibility as an automated and standardized technique for breast imaging.

Ultrasound computed tomography in breast imaging: first clinical results of a custom-made scanner.

For the detection of breast cancer, ultrasound is conventionally used in addition to mammography. However, ultrasound is highly operator-dependent since speckle, depth dependency and artifacts (e.g. shadowing) affect image quality. Full Angle Spatial Compounding (FASC) may overcome those limitations by superimposing ultrasound data acquired in one cross-sectional plane from aspect angles all around an object. Furthermore, we showed in vitro that FASC also improves contrast perfusion imaging. To apply FASC to breast imaging, we developed an add-on system to a conventional ultrasound scanner, integrated in a custom-made examination couch. Here, we present first in-vivo results from test persons and patients with breast lesions.

An Automated System for Full Angle Spatial Compounding in Ultrasound Breast Imaging

In Full Angle Spatial Compounding (FASC) single ultrasound images from aspect angles all around an object are incoherently superimposed to achieve a higher image quality. To apply FASC to breast imaging, we developed an add-on system to a conventional ultrasound echo scanner. With this system also the distribution of Speed of Sound (SoS) inside the breast can be reconstructed using a reflector behind the breast. Next to diagnostics, SoS-images are used to geometrically correct FASC-images and avoid artifacts. However, since attenuation in the breast and reflections at its boundary are high, the detection of the reflector and the SoS-reconstruction may fail. To still correct FASC-images, we developed an image based method to compute a mean SoS for the breast on the basis of a typical double-line artifact in the FASC-image.

G. Schulte-Altedorneburg

Papers

MRI patterns in recurrence of primary CNS lymphoma in immunocompetent patients

Ultrasound breast imaging using Full Angle Spatial Compounding: In-vivo results

Ultrasound computed tomography in breast imaging: first clinical results of a custom-made scanner.

An Automated System for Full Angle Spatial Compounding in Ultrasound Breast Imaging

Determination of a mean sound velocity in the female breast for artifact reduction in Full Angle Spatial Compounding