Jason Zalev

Detecting abnormal vasculature from photoacoustic signals using wavelet-packet features

Photoacoustic systems can produce high-resolution, high-contrast images of vascular structures. To reconstruct images at very high-resolution, signals must be collected from many transducer locations, which can be time consuming due to limitations in transducer array technology. A method is presented to quickly discriminate between normal and abnormal tissue based on the structural morphology of vasculature. To demonstrate that the approach may be useful for cancer detection, a special simulator that produces photoacoustic signals from 3D models of vascular tissue is developed. Results show that it is possible to differentiate tissue classes even when it is not possible to resolve individual blood vessels. Performance of the algorithm remains strong as the number of transducer locations decreases and in the presence of noise.

Clinical Feasibility Study of Combined Optoacoustic and Ultrasonic Imaging Modality Providing Coregistered Functional and Anatomical Maps of Breast Tumors

We report on findings from the clinical feasibility study of the ImagioTM. Breast Imaging System, which acquires two-dimensional opto-acoustic (OA) images co-registered with conventional ultrasound using a specialized duplex hand-held probe. Dual-wavelength opto-acoustic technology is used to generate parametric maps based upon total hemoglobin and its oxygen saturation in breast tissues. This may provide functional diagnostic information pertaining to tumor metabolism and microvasculature, which is complementary to morphological information obtained with conventional gray-scale ultrasound. We present co-registered opto-acoustic and ultrasonic images of malignant and benign tumors from a recent clinical feasibility study. The clinical results illustrate that the technology may have the capability to improve the efficacy of breast tumor diagnosis. In doing so, it may have the potential to reduce biopsies and to characterize cancers that were not seen well with conventional gray-scale ultrasound alone.

Exact solution for a photoacoustic wave from a finite-length cylindrical source

In wide-field pulsed photoacoustics, a nearly instantaneous source of electromagnetic energy is applied uniformly to an absorbing medium to create an acoustic wave. In this work, an exact solution is derived for the photoacoustic wave originating from a finite-length solid cylindrical source in terms of known analytic functions involving elliptic integrals of canonical form. The solution is compared with the output of a finite-element simulation.

Opto-acoustic breast imaging with co-registered ultrasound

We present results from a recent study involving the ImagioTM breast imaging system, which produces fused real-time two-dimensional color-coded opto-acoustic (OA) images that are co-registered and temporally inter- leaved with real-time gray scale ultrasound using a specialized duplex handheld probe. The use of dual optical wavelengths provides functional blood map images of breast tissue and tumors displayed with high contrast based on total hemoglobin and oxygen saturation of the blood. This provides functional diagnostic information pertaining to tumor metabolism. OA also shows morphologic information about tumor neo-vascularity that is complementary to the morphological information obtained with conventional gray scale ultrasound. This fusion technology conveniently enables real-time analysis of the functional opto-acoustic features of lesions detected by readers familiar with anatomical gray scale ultrasound. We demonstrate co-registered opto-acoustic and ultrasonic images of malignant and benign tumors from a recent clinical study that provide new insight into the function of tumors in-vivo. Results from the Feasibility Study show preliminary evidence that the technology may have the capability to improve characterization of benign and malignant breast masses over conventional diagnostic breast ultrasound alone and to improve overall accuracy of breast mass diagnosis. In particular, OA improved speci city over that of conventional diagnostic ultrasound, which could potentially reduce the number of negative biopsies performed without missing cancers.

Verification and fault synthesis algorithm at switch-level

Abstract Switch-level simulation has become a common means for accurate modelling of CMOS circuit behaviour and testing. This paper presents an algorithm for modelling CMOS circuits with an arithmetic solution for circuit verification and fault synthesis. This new approach is capable of simulating multiple fault injection into the circuit and speeds up switch-level simulation. Another advantage of this algorithm is its application in the mapping of single and multiple faults from switch-level to gate level as well as its function as a multi level model. Multiple faults can be of the same or different types. Experimental results show that the algorithm is successful and reliable for CMOS technology.

Automatic fingerprint recognition algorithm

This paper summarizes a simple procedure for preprocessing and extracting minutiae from digital fingerprint images. Many approaches were studied, and the best approaches were selected and slightly modified. Methods for computing minutiae directions and further canceling false endpoints were added. The thinning algorithms of both Bernard and Chin, and the minutiae extraction algorithm of Tico were used. The reasons for their selection are discussed in detail.

Photoacoustic simulation of microvessel bleeding: spectral analysis and its implication for monitoring vascular-targeted treatments

The destruction of blood vessels is a commonly used cancer therapeutic strategy. Bleeding consequently follows and leads to the accumulation of blood in the interstitium. Photoacoustic (PA) imaging is well positioned to detect bleeding due to its sensitivity to hemoglobin. After treatment vascular disruption can occur within just a few hours, which leads to bleeding which might be detected using PA to assess therapeutic effectiveness. Deep micro-vessels cannot typically be resolved using acoustic-resolution PA. However, spectral analysis of PA signals may still permit assessment of bleeding. This paper introduces a theoretical model to simulate the PA signals from disrupted vessels using a fractal model. The fractal model uses bifurcated-cylinder bases to represent vascular trees. Vessels have circular absorption cross-sections. To mimic bleeding from blood vessels, the diffusion of hemoglobin from micro-vessels was simulated. The PA signals were computed and in the simulations were detected using a linear array transducer (30 MHz center frequency) for four different vascular trees (at 256 axial spatial locations/tree). The Fourier Transform of each beam-formed PA signal was computed and the power spectra were fitted to a straight line within the -6 dB bandwidth of the receiving transducer. When comparing the power spectra before and after simulated bleeding, the spectral slope and mid-band fit (MBF) parameters decreased by 0.12 dB/MHz and 2.12 dB, while the y-intercept did not change after 1 hour of simulated bleeding. The results suggest that spectral PA analysis is sensitive to changes in the concentration and spatial distribution of hemoglobin in tissue, and changes due to bleeding can be detected without the need to resolve individual vessels. The simulations support the applicability of PA imaging in cancer treatment monitoring by detecting micro-vessel disruption.

Opto-acoustic image fusion technology for diagnostic breast imaging in a feasibility study

Functional opto-acoustic (OA) imaging was fused with gray-scale ultrasound acquired using a specialized duplex handheld probe. Feasibility Study findings indicated the potential to more accurately characterize breast masses for cancer than conventional diagnostic ultrasound (CDU). The Feasibility Study included OA imagery of 74 breast masses that were collected using the investigational Imagio® breast imaging system. Superior specificity and equal sensitivity to CDU was demonstrated, suggesting that OA fusion imaging may potentially obviate the need for negative biopsies without missing cancers in a certain percentage of breast masses. Preliminary results from a 100 subject Pilot Study are also discussed. A larger Pivotal Study (n=2,097 subjects) is underway to confirm the Feasibility Study and Pilot Study findings.

Clinical optoacoustic imaging combined with ultrasound for coregistered functional and anatomical mapping of breast tumors

Optoacoustic imaging, based on the differences in optical contrast of blood hemoglobin and oxyhemoglobin, is uniquely suited for the detection of breast vasculature and tumor microvasculature with the inherent capability to differentiate hypoxic from the normally oxygenated tissue. We describe technological details of the clinical ultrasound (US) system with optoacoustic (OA) imaging capabilities developed specifically for diagnostic imaging of breast cancer. The combined OA/US system provides co-registered and fused images of breast morphology based upon gray scale US with the functional parameters of total hemoglobin and blood oxygen saturation in the tumor angiogenesis related microvasculature based upon OA images. The system component that enabled clinical utility of functional OA imaging is the hand-held probe that utilizes a linear array of ultrasonic transducers sensitive within an ultrawide-band of acoustic frequencies from 0.1 MHz to 12 MHz when loaded to the high-impedance input of the low-noise analog preamplifier. The fiberoptic light delivery system integrated into a dual modality probe through a patented design allowed acquisition of OA images while minimizing typical artefacts associated with pulsed laser illumination of skin and the probe components in the US detection path. We report technical advances of the OA/US imaging system that enabled its demonstrated clinical viability. The prototype system performance was validated in well-defined tissue phantoms. Then a commercial prototype system named Imagio™ was produced and tested in a multicenter clinical trial termed PIONEER. We present examples of clinical images which demonstrate that the spatio-temporal co-registration of functional and anatomical images permit radiological assessment of the vascular pattern around tumors, microvascular density of tumors as well as the relative values of the total hemoglobin [tHb] and blood oxygen saturation [sO2] in tumors relative to adjacent normal breast tissues. The co-registration technology enables increased accuracy of radiologist assessment of malignancy by confirming, upgrading and/or downgrading US categorization of breast tumors according to Breast Imaging Reporting And Data System (BI-RADS). Microscopic histologic examinations on the biopsied tissue of the imaged tumors served as a gold standard in verifying the functional and anatomic interpretations of the OA/US image feature analysis.

Classifying normal and abnormal vascular tissues using photoacoustic signals

In this paper a new method is proposed to classify vascular tissues in the range from normal to different degrees of abnormality based on the Photo-Acoustic (PA) signals generated by different categories of vasculatures. The classification of the vasculatures is achieved based on the statistical features of the photoacoustic radiofrequency (RF) signals such as energy, variance, and entropy in the wavelet domain. A feature vector for each category of vasculature is provided and the distance between feature vectors are computed as the measure of similarity between vasculatures. The distances are mapped in two-dimensional space depicting the proximities of the different categories of the vasculatures. The method proposed in this paper can help both detecting abnormal tissues and monitoring the treatment progress by measuring the similarity between vascular tissues in different stages of treatment. The method is applied to simulated data as well as in vivo data from tumor bearing mice to detect cancer treatment effects.