Miklos Z. Kiss

Viscoelastic characterization of in vitro canine tissue

Mechanical properties of biological tissues are of interest for assessing the performance of elastographic methods that evaluate the stiffness characteristics of tissue. The mechanical properties of interest include the frequency-dependent complex moduli, storage and loss moduli of tissues. Determination of the mechanical properties of biological tissues is often limited by proper geometry of the sample, as well as homogeneity of the stress-strain relationship. Measurements were performed on in vitro canine liver tissue specimens, over a frequency range from 0.1 to 400 Hz. Tests were conducted using an EnduraTEC ELF 3200, a dynamic testing system for determining the mechanical properties of materials. Both normal tissues and thermal lesions prepared by radio frequency ablation were tested. Experiments were conducted by uniaxially compressing tissue samples using Plexiglas platens larger than the specimens and measuring the load response. The resulting moduli spectra were then fit to a modified Kelvin-Voigt model, called the Kelvin-Voigt fractional derivative model. The data agree well with the model and in comparing the results from the normal tissue with that of the thermal lesions, the concept of a complex modulus contrast is introduced and its applications to elastography are discussed.

Measurement of image contrast using diffraction enhanced imaging

Refraction contrast of simple objects obtained using diffraction enhanced imaging (DEI) was studied and compared to conventional radiographic contrast. Lucite cylinders and nylon wires were imaged using monochromatic synchrotron radiation at the National Synchrotron Light Source (http://nslsweb. nsls.bnl.gov/nsls/Default.htm) at the Brookhaven National Laboratory. The DEI images were obtained by placing a silicon analyser crystal tuned to the [333] diffraction plane in the beam path between the sample and the detector. To compare the DEI images with conventional radiographic images requires a consistent definition of refraction and absorption contrast. Conventional definitions of contrast favour conventional radiography and DEI contrast is defined to emphasize the specific characteristics of DEI. The proposed definitions were then used to find the DEI gain (the ratio of the DEI contrast with respect to the conventional image contrast). The results presented here show that the DEI gain is consistently greater than 1, indicating that DEI provides more contrast information than conventional radiography.

Frequency-dependent complex modulus of the uterus: preliminary results

The frequency-dependent complex moduli of human uterine tissue have been characterized. Quantification of the modulus is required for developing uterine ultrasound elastography as a viable imaging modality for diagnosing and monitoring causes for abnormal uterine bleeding and enlargement, as well assessing the integrity of uterine and cervical tissue. The complex modulus was measured in samples from hysterectomies of 24 patients ranging in age from 31 to 79 years. Measurements were done under small compressions of either 1 or 2%, at low pre-compression values (either 1 or 2%), and over a frequency range of 0.1-100 Hz. Modulus values of cervical tissue monotonically increased from approximately 30-90 kPa over the frequency range. Normal uterine tissue possessed modulus values over the same range, while leiomyomas, or uterine fibroids, exhibited values ranging from approximately 60-220 kPa.

Improved image contrast of calcifications in breast tissue specimens using diffraction enhanced imaging

The contrast of calcifications in images of breast tissue specimens using a synchrotron-based diffraction enhanced imaging (DEI) apparatus has been measured and is compared to the contrast in images acquired using a conventional synchrotron-based radiographic imaging modality. DEI is an imaging modality which derives image contrast from x-ray absorption, refraction and small-angle scatter-rejection (extinction), unlike conventional radiographic techniques, which can only derive contrast from absorption. DEI is accomplished by inserting an analyser crystal in the beam path between the sample and the detector. Two of the three breast tissue specimens contained calcifications associated with cancer, while a third contained benign calcifications. Results of the image analysis indicate that the DEI contrast of images taken with the analyser crystal tuned to the peak of its rocking curve, was as much as 19 times that of the conventional radiograph, with an average of 5.5 for all calcifications. This improved image contrast for even near-pixel-size calcifications suggests potential utility for DEI in breast imaging.

Investigation of temperature-dependent viscoelastic properties of thermal lesions in ex vivo animal liver tissue

The viscoelastic characteristics of thermal lesions in ex vivo animal liver are investigated in this paper. Characterization of the moduli of thermal lesions prepared at several temperatures will provide additional information for the elastographic monitoring of radio frequency ablation of hepatic tumors. In this study, the frequency-dependent complex modulus of thermal lesions prepared at temperatures ranging from 60 to 90 degrees C over a frequency range from 0.1 to 50Hz are presented. Lesions were prepared using either radio frequency ablation or double immersion boiling. It was found that both the magnitude and phase of the modulus increase with frequency, a behavior that has been noted in the literature. A new result reported shows that the modulus dependence on temperature reveals a local maximum around 70-75 degrees C corresponding to the temperature at which tissue has released most of its water content. The modulus values at temperatures higher than 70 degrees C continued to increase, but the extent of increase depend on animal species and other factors.

In Vitro Uterine Strain Imaging Preliminary Results

Uterine abnormalities, such as leiomyomas, endometrial polyps, and adenomyosis, are often clinically associated with irregular uterine bleeding. These abnormalities can have similar B‐mode characteristics but require different treatment. The objective of this study was to develop diagnostic techniques based on ultrasound strain imaging that would allow in vivo visualization and characterization of endometrial and myometrial uterine abnormalities, enabling physicians to improve diagnosis and treatment.

DIFFRACTION ENHANCED IMAGING OF SOFT TISSUES

Z. ZHONG , D. CHAPMAN, D. CONNOR , A. DILMANIAN, N. GMUR , M. HASNAH, R. E. JOHNSTON, M. Z. KISS, J. LI , C. MUEHLEMAN-, O. OLTULU, C. PARHAM, E. PISANO, L. RIGON , D. SAYERS, W. THOMLINSON, M. YAFFE, AND H. ZHONG 1 2 NSLS, Brookbaven National Lab., Upton, NY 11973, USA Biological, Chemical and Physical Sci., Illinois lnst. Tech., Chicago, IL 60616, USA Dept. Physics, North Carolina State Univ., Raleigh, NC 27695, USA Medical Dept., Brookhaven National Lab., Upton, NY 11973, USA Dept. Biochemistry, Anatomy, Rush Med. College, Chicago, IL 60612, USA Biomed. Eng., Radiology, Univ. North Carolina, Chapel Hill, NC 27599, USA Dept. Physics, Univ. of Trieste and INFN, Sezione di Trieste, Italy ESRF, F-38043, Grenoble Cedex, France 11 Med. Imaging and Med. Biophysics, Univ. Toronto, Ontario, M4N3M5, Canada Dept. Mechanical Engineering, Univ. Akron, Akron, OH 44325-3903, USA

Application of the multiple image radiography method to breast imaging

The Multiple Image Radiography (MIR) method is new imaging modality that extends the capability of conventional absorption based radiography by adding the additional contrast mechanisms of x-ray refraction and ultra-small angle scatter. In order to design a clinically based MIR system, the MIR specific x-ray properties in breast tissue must be analyzed to determine which are diagnostically useful. Developing MIR as an imaging modality also requires developing new phantoms that incorporate x-ray refraction and ultra-small angle scatter in addition to traditional x-ray absorption. Three breast cancer specimens were imaged using MIR to demonstrate its MIR specific x-ray properties. An uncompressed anthropomorphic breast phantom with an imbedded low absorption contrast acrylic sphere was imaged to provide a physical model of how the unique properties of MIR can be utilized to improve upon conventional mammography and illustrate how these can be used to design a clinically useful imaging system.

X-ray diffraction order selection with a prism in DEI (abstract)

The refraction angle of x rays as they pass through a refractive prism is proportional to the square of the x-ray wavelength. This was used to discriminate between different harmonic orders, which have different energies, created by a two-crystal 111 monochromator [Z. Zhong, J. Appl. Crystallogr 33, 1082 (2000)]. Refractive prisms inserted between the two monochromator crystals allowed selection, among the 111, 333, 444, and 555 diffractions, in our diffraction enhanced imaging program at National Synchrotron Light Source’s X15A beamline, and facilitated convenient change of sensitivity in our efforts to optimize DEI system for mammography and other radiographic applications. The selection of 111 and 333 refractions were straightforward since the necessary angle of refraction is small. The challenge of selecting 444 and 555 reflections was met by designing an acrylic prism that offered an angle of refraction much larger than 10 μrad and was compact enough to be manipulated in the small space between the c...