In-vivo evaluating and quantifying the mechanical properties of tissues, particularly the elastic properties of soft tissues, which have been of increasing interest for many medical applications for the past. two decades, by utilizing conventional measurement methods are difficult. Elastography is a promising imaging modality for invivotissue characterization. It was proposed to be utilized for breast cancer detection on the basis of tissue hardness being indicative of the presence of a tumor as the practice of palpation examination would indicate. The new imaging technique "Optical Elastography" has the potential as a clinical tool for in-vivo assessing the stiffness of biological tissues. In this paper, we briefly discuss the results of almost a-decade investigations in the field of optical elastography. We present the basic principles and limitations that are involved in the production of elastograms of biological tissues. We conclude the paper with the review of potential applications of this technique for medical diagnosis. We also discuss some fields in which much progress has yet to be made in order for optical elastography to become a viable clinical tool. The usefulness of this technology and the new information it provides suggest that it might soon be available as a commercial system.

Introduction: Pulsed photoacoustic imaging with wideband medical application is a technique in which the absorption of optieal pulse in chromophores produces ultrasonic thermoelastic waves. The waves are detected by an ultrasonic transducer at the surface of the tissue. The transducer with adequate resolution and acoustic sensitivity provides molecular imaging of superficial tissue structures such as the microvessels and skin. In this article, the sensitivity of the optical detection systems were measured in comparison with that of the calibrated hydrophone under the same experimental conditions. Material and Methods: A continuous Nd: YAG laser, a pulsed Nd: YAG laser, an optical stress detection system, a Fabry Perot detection system, a needle hydrophone, a fast-photodiode and a 500 MHz digital oscilloscope were used. Laser pulses (energy = 10 mJ, pulsewidth = 6 ns) were delivered via an optical fiber (600 mm) into an aqueous solution of Indocyanine Green (ICG). The pulses absorbed in the solution, and then acoustic waves produced and received by ultrasonic transducer at the surface of the tissue. The other side of the transducer was illuminated by the continuous laser at the wavelength of 532 nm .The modulated optical beam was detected by the photodiode and the digital oscilloscope. Therefore, a photoacoustic signal was observed as a bipolar signal on the oscilloscope monitor.The sensitivity of the of the optical stress transducer was measured in comparison with a Fabry Perot detection system and a needle hydrophone by measuring a signal to noise ratio (SNR) and a noise equivalent pressures (NEP).Results: The SNR of hydrophone, optical stress transducer and Fabry Perot were 56dB, 45 dB and 26 dB respectively. NEP of hydrophone, Fabry Perot detection system and optical stress detection system were 11 kPa, 13 kPa and 15 kPa, respectively. So NEP of Fabry Perot was 2 kPa higher than that of the Optical stress detection system.Discussion: NEP of Fabry Perot is higher that of the optical stress detection system. Because the bandwidth of the Fabry Perot was 8 MHz higher than that of the optical stresses detection system. Conclusion: The combination of high sensitivity and the small active area makes the optical stress system particularly suitable for photoacoustic imaging applications.

Introduction: Radiation imaging is one of the applicable methods in diagnostic medicine and nondestructive testing for industrial applications. In nondestructive 3D imaging, in addition to the radiation source, there is a requirement for a suitable detection system, data acquisition system, mechanical sections for moving objects, reconstruction algorithm and finally a computer for processing and control.Method and Materials: One of the most important components of a digital radiation imaging system is its detector. Light photodiode is a new light sensor which is used in digital imaging systems because of its high efficiency. In the present research, a photodiode grid has been implemented to design and make a detection system. The photodiode grid has an array of 10×10 photodiodes in a 50×50 mm2 area. Beside the photodiode grid, a control board has been designed. Furthermore, a mechanical system has been designed to move the objects in the horizontal and vertical directions, and also rotate it around its own axis. The maximum displacement in the horizontal and vertical directions is 60 cm with step accuracy of about 0.015 mm. Step accuracy of the rotational movement is about 0.9 degrees. Results: After the imaging system was constructed, background and uniformity of the system were tested. All the photodiodes in the imaging system showed good uniformity. The image data was transferred to a computer and processed using a MATLAB program to display the images on a monitor. As the physical resolution of the system is about the pixel size (5 mm), only the overall images of the object's dimensions were expected to be produced.Discussion and Conclusion: The fidelity of the detection system has been successfully tested using a visible light source and several test samples. The presented system is able to reconstruct 3D images and obtain cross-sectional images of the objects, by using the image processing algorithm specifically designed for it.

Introduction: Currently, the use of electromagnetic waves in medicine, especially in diagnostic devices such as magnetic resonance imaging (MRI) has increased and many of its biological effects have been reported. The aim of this study was to investigate the adverse effects of 1.5 T MRI on fertility and reproductive parameters of male mice.Materials & methods: Forty NMRI adult male mice were randomly divided into two groups of control and experimental. The mice in the experimental group were exposed to MRI at 1.5T for 36 minutes once a week for a period of 3 weeks. Then, in the 1st day and 35th day after the final exposure, 10 mice were used for IVF and 10 mice for In vivo studies. MRI effects on testis weight, the duration of pregnancy, the number of newborns, sperm count, and fertility were evaluated. The obtained data were analyzed by using ANOVA and Tukey’s tests.Findings: According to the present study, one day after MRI exposure, testis weight, sperm count, and the number of born children were significantly decreased in the experimental group (P 0.05).Discussion & Conclusion: Based on the results of the present study, it seems that although the MRI at 1.5T has adverse effects on fertility and reproductive parameters of the adult male mice, these side-effects are reversible.

Introduction: Fluorescence molecular imaging (FMI) in reflectance mode is a powerful method for providing valuable information about pathologic processes.Tumor growth is a common pathologic process which can be traditionally obtained by caliper measurement. The caliper measurement has several major disadvantages. However FMI method can be used as a non-invasibly method. The goal of this project is validating FMI of tumor growth by comparing it to traditional tumor volume measurement method such as caliper measurement.Materials and methods: Here we used an animal tumor model to evaluate the extent on correlation between noninvasively measured fluorescence and traditional methods. BALB/c mice received subcutaneous injection of WEHI-164 cells. The tumor size was measured. Fluorescein was directly injected in center of the tumor. Serial measurements of fluorescence intensities were performed with FMI. After imaging, the mice were sacrificed and tumor was removed for weighting.Results: The results showed that Spearman correlation coefficient between tumor volume and the maximum height of fluorescent intensity in the first, the second and the third group are 0.019, 0.5 and 0.09 respectively. The ROC analysis showed that the cutoff point of tumor volume and the weight are 93 mm3 and 0.12 g respectively.Discussion and ConclusionThe measurement of tumor growth in the BALB/c mice by imaging fluorescence correlates well with the traditional method of determining the tumor volume and with the increase in tumor weight that results from tumor growth. Given the great advantages of measuring fluorescence intensity, we conclude that FMI imaging is a the reliable and superior method for measuring experimental tumor growth in the small animals.