Imaging of joints with laser‐based photoacoustic tomography: An animal study

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134964/1/mp4166.pd

A Framework for Directional and Higher-Order Reconstruction in Photoacoustic Tomography

Photoacoustic tomography is a hybrid imaging technique that combines high optical tissue contrast with high ultrasound resolution. Direct reconstruction methods such as filtered backprojection, time reversal and least squares suffer from curved line artefacts and blurring, especially in case of limited angles or strong noise. In recent years, there has been great interest in regularised iterative methods. These methods employ prior knowledge on the image to provide higher quality reconstructions. However, easy comparisons between regularisers and their properties are limited, since many tomography implementations heavily rely on the specific regulariser chosen. To overcome this bottleneck, we present a modular reconstruction framework for photoacoustic tomography. It enables easy comparisons between regularisers with different properties, e.g. nonlinear, higher-order or directional. We solve the underlying minimisation problem with an efficient first-order primal-dual algorithm. Convergence rates are optimised by choosing an operator dependent preconditioning strategy. Our reconstruction methods are tested on challenging 2D synthetic and experimental data sets. They outperform direct reconstruction approaches for strong noise levels and limited angle measurements, offering immediate benefits in terms of acquisition time and quality. This work provides a basic platform for the investigation of future advanced regularisation methods in photoacoustic tomography.Comment: submitted to "Physics in Medicine and Biology". Changes from v1 to v2: regularisation with directional wavelet has been added; new experimental tests have been include

A framework for directional and higher-order reconstruction in photoacoustic tomography

Photoacoustic tomography is a hybrid imaging technique that combines high optical tissue contrast with high ultrasound resolution. Direct reconstruction methods such as filtered back-projection, time reversal and least squares suffer from curved line artefacts and blurring, especially in the case of limited angles or strong noise. In recent years, there has been great interest in regularised iterative methods. These methods employ prior knowledge of the image to provide higher quality reconstructions. However, easy comparisons between regularisers and their properties are limited, since many tomography implementations heavily rely on the specific regulariser chosen. To overcome this bottleneck, we present a modular reconstruction framework for photoacoustic tomography, which enables easy comparisons between regularisers with different properties, e.g. nonlinear, higher-order or directional. We solve the underlying minimisation problem with an efficient first-order primal-dual algorithm. Convergence rates are optimised by choosing an operator-dependent preconditioning strategy. A variety of reconstruction methods are tested on challenging 2D synthetic and experimental data sets. They outperform direct reconstruction approaches for strong noise levels and limited angle measurements, offering immediate benefits in terms of acquisition time and quality. This work provides a basic platform for the investigation of future advanced regularisation methods in photoacoustic tomography

Tomographic imaging with an ultrasound and LED-based photoacoustic system

Pulsed lasers in photoacoustic tomography systems are expensive, which limit their use to a few clinics and small animal labs. We present a method to realize tomographic ultrasound and photoacoustic imaging using a commercial LED-based photoacoustic and ultrasound system. We present two illumination configurations using LED array units and an optimal number of angular views for tomographic reconstruction. The proposed method can be a cost-effective solution for applications demanding tomographic imaging and can be easily integrated into conventional linear array-based ultrasound systems. We present a potential application for finger joint imaging in vivo, which can be used for point-of-care rheumatoid arthritis diagnosis and monitoring.</p

Microwave-induced thermoacoustic tomography: applications and corrections for the effects of acoustic heterogeneities

This research is primarily focused on developing potential applications for microwaveinduced thermoacoustic tomography and correcting for image degradations caused by acoustic heterogeneities. Microwave-induced thermoacoustic tomography was first used to verify the feasibility of noninvasively detecting the coagulated damage based on different dielectric properties between normal tissue and lesion treated with high intensity focused ultrasound. Good image contrasts were obtained for the lesions. A comparison of the size of the lesion measured with microwave-induced thermoacoustic tomography and the size measured by a gross pathologic photograph was presented to verify the effectiveness the proposed method. Clinical data for breast tumors were also collected to verify the feasibility of using microwave-induced thermoacoustic tomography in breast cancer imaging. Next, the effects of acoustic heterogeneities on microwave-induced thermoacoustic tomography in weakly refractive medium were investigated. A correction method based on ultrasonic transmission tomography was proposed to correct for the image distortion. Numerical simulations and phantom experiments verify the effectiveness of this correction method. The compensation is important for obtaining higher resolution images of small tumors in acoustically heterogeneous tissues. Finally, the effects of the highly refractive skull on transcranial brain imaging were studied. A numerical method, which considered wave reflection and refraction at the skull surfaces, was proposed to compensate for the image degradation. The results obtained with the proposed model were compared with the results without considering the skull-induced distortion to evaluate the skull-induced effects on the image reconstruction. It was demonstrated by numerical simulations and phantom experiments that the image quality could be improved by incorporating the skull shape and acoustic properties into image reconstruction. This compensation method is important when the thickness of skull cannot be neglected in transcranial brain imaging

Anti-schistosoma single-domain antibody-nanoparticles conjugate: a novel tool for diagnostic and therapeutic applications

Nanotechnology has enthused excessive expectations in recent years, particularly in the biology and biomedical fields. Carbon-coated metallic nanomagnets reveal significant physicochemical properties, which are referred to as superparamagnetism, that when designed appropriately can be utilized to generate novel diagnostic and therapeutic applications for a wide range of biologically hazardous species. Schistosomiasis is a chronic parasitic disease that can infect both humans and animals, particularly cattle. It is caused by a trematode blood fluke of the genus Schistosoma which belong to the schistosomatidae family. At least 200 million individuals are infected in 75 countries while 600 million people are exposed to infection and are potentially victim of this parasite. Schistosomiasis is still recognized as one of the most neglected disease, the current available diagnostic techniques are deficient in accuracy and are incapable of identifying the disease in its early stages. Moreover, they suffer from prolonged examination time. Besides, the poorly available therapeutic drugs started to lose their efficacy and the parasite started to develop resistance against most of them, which create an imperative need for developing novel diagnostic and therapeutic tools. The humoral immune response of the Camelidae is unique since these animals possess functional heavy-chain only antibodies in addition to the classical antibodies. Thanks to recombinant DNA technology, a series of single domain antigen binding entities can be produced against specific schistosomeâ s parasite antigens. These binders possess a number of distinctive biophysical properties that offer particular advantages in various theranostic applications. Finally, nanomagnetism was selected to represent a certain phenomena through which we demonstrated, to our knowledge for the first time, the successful construction of effective and functional bioconjugate system which is appropriate for a plethora of diagnostic and therapeutic applications. The main thrust of this research work was towards the developing of single domain antibodies against Schistosoma mansoni gut specific antigen and execratory secretory antigen. In parallel, state-of-the-art methodologies were implemented for constructing a bioconjugate system composed of sdAb and graphene-coated metallic nanomagnet tagged with a carboxyl terminal. Finally, the well-established metastable technetium-99 (99mTc) is used for labeling the conjugate for studying the possibility of active and magnetic targeting of the nano-structured system i.e. 99mTc-sdAb-Fe@C-MNP conjugates

Biomedical Photoacoustic Imaging and Sensing Using Affordable Resources

The overarching goal of this book is to provide a current picture of the latest developments in the capabilities of biomedical photoacoustic imaging and sensing in an affordable setting, such as advances in the technology involving light sources, and delivery, acoustic detection, and image reconstruction and processing algorithms. This book includes 14 chapters from globally prominent researchers , covering a comprehensive spectrum of photoacoustic imaging topics from technology developments and novel imaging methods to preclinical and clinical studies, predominantly in a cost-effective setting. Affordability is undoubtedly an important factor to be considered in the following years to help translate photoacoustic imaging to clinics around the globe. This first-ever book focused on biomedical photoacoustic imaging and sensing using affordable resources is thus timely, especially considering the fact that this technique is facing an exciting transition from benchtop to bedside. Given its scope, the book will appeal to scientists and engineers in academia and industry, as well as medical experts interested in the clinical applications of photoacoustic imaging

Investigation of Techniques to increase the Field of View of a Staring Transducer Array for Photoacoustic Imaging

Photoacoustic imaging (PAI) is a hybrid imaging modality that takes advantage of both optical and acoustic techniques for biomedical imaging. It is believed that PAI can successfully assess the margins of lumpectomy specimens in the operating room, decreasing the number of surgeries and wait time for patients. However, current PAI systems do not have sufficient field of view (FOV) to accommodate the size of lumpectomy specimens. In this work, transducer directionality and the use of a shaped matching layer were explored as means to increase the FOV of a staring photoacoustic transducer array. The results indicated that applying a convex matching layer to the face of transducers and directing them toward the centre of the array provides optimal sensitivity throughout the imaging volume. By employing these techniques, any PAI system’s effective FOV can be increased without replacing existing transducers. The optimized system can now be investigated for lumpectomy margin assessment