2023 CiteScore: 0.8
pISSN: 2345-5829
eISSN: 2345-5837
Editor-in-Chief:
Mohammad Reza Ay
Chairman:
Saeid Sarkar
Executive Director:
Hossein Ghadiri
Vol 2 No 4 (2015)
Original Article(s)
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Purpose: Elastography is a promising method as a non-invasive test to assess the liver tissue for diagnosing chronic diseases such as fatty liver, fibrosis and cirrhosis. Most of elastography techniques measure the velocity of shear wave propagation in liver to estimate the elasticity. A high frame rate imaging system is usually required to measure the velocity of shear waves which leads to higher complexity and costs. Inducing interference patterns of shear wave is one of the proposed methods for reducing the frame rate in measuring wave propagation velocity during tissue elastography. Previously, the Nyquist rate must be met in order to provide an appropriate image for extracting the patterns with a reasonable accuracy.
Methods: To reduce the required rate of imaging, static patterns of shear wave interference should be extracted to determine the wavelength and consequently the velocity of shear wave. Shear waves are induced in the tissue using acoustic radiation force. In this article we propose a technique, and apply it to ultrasound images acquired before and after inducing the shear waves to extract the interference pattern.
Results: The average error in measuring the elasticity of the simulated phantom with the shear wave frequency of 100 Hz is 4.8%.
Conclusion: The method does not impose any restrictions on the time interval between images, so the tissue elasticity can be calculated independent of the imaging rate. -
Purpose: This article is dedicated to introduce an Automatic Trocar for LAparoscopic Surgery (ATLAS). The first step in laparoscopic surgery is the port insertion which is known as the most important and potentially dangerous step. An inaccurate Veress needle placement or uncontrolled overshoot of a sharp, blind trocar toward the viscera are the common causes of an unsuccessful procedure. Therefore, a mechatronic device was designed and developed to overcome the shortcomings of the current port insertion techniques.
Methods: The system incorporates an automatic insertion apparatus and an automatic stop mechanism to halt the procedure upon reaching the abdominal cavity. A motor was provided to pass the needle through the abdominal layers and a pressure sensor was provided to detect reaching peritoneum and stop the entry mechanism.
Results: The system was tested on an anesthetized canine. ATLAS system stopped upon reaching its peritoneum and avoided injury to intra-abdominal organs. Subsequently, the position of the needle tip was evaluated using another endoscope.
Conclusion: The animal test of the system was promising and showed the potential of this system and its improved version in laparoscopic surgeries. -
Introduction: Cardiac contraction and respiratory movement are two main factors which degrade gated myocardial perfusion SPECT images quality by inducing image blurring and also cause quantification inaccuracies. We propose a non-rigid motion correction step before image summation to eliminate the influence of cardiac motion on MPS images.
Material and Method: In this work we studied the effect of our motion correction method on projection data both using simulation and patient data. The mathematical four-dimensional NURBS-based Cardiac-Torso phantom with two different heart sizes (124 ml and 100 ml left ventricular cavities) were constructed for male and female, respectively. SIMIND Monte Carlo simulation package was used to simulate a clinical Tc99-mibi perfusion SPECT acquisition protocol on the dual headed gamma camera (Philips Medical Systems, Cleveland, Ohio), with Low Energy High Resolution (LEHR) collimators. We have warped each frame from, with respect to end diastolic frame, using a 3D dimensional non-parametric diffeomorphic algorithm based on Thirion demon registration technique in MATLAB 2015. 4D sequence of motion corrected projections and original projection data were reconstructed using FBP and OSEM algorithm in AutoRecon application in Cedars Sinai package. Myocardial thickness, myocardium to blood pool contrast and CNR were measured in summed images before correction and motion corrected (BC and MC respectively). Quantitative study of Image sequences were conducted after importing image sequences to cardiac SPECT system’s work station. BC and MC summed image parameters were automatically derived and calculated on the basis of sex specific normal limits obtained from the healthy population using standard Cedars-Sinai software.
Result: Myocardial wall thickening between end-diatolic to end systolic frame, in lateral wall is reduced 11% from BC images to MC images in patient study which is statistically significant. Myocardium to blood pool contrast in MC images are greater than the corresponding summed images before correction (BC) (27.10±11.07 vs. 32.55±12.07), CNR has increased 31% in MC images compared to corresponding BC images. TPD (Total Perfusion Defect) measure before and after correction were highly correlated.
Conclusion: Motion correction in projection domain may increases image quality by reducing blurring due to cardiac motion and possibly intra frame motion. Higher myocardial to blood pool contrast and CNR obtained in this study. It is highly recommended that with correction we can improve defect detectability and diagnostic value of images, further assessment with large patient population is under evaluation. -
Purpose: Nowadays in most researches, thermoluminescent dosimeters are used as a practical implement for dosimetry systems. In this study, we calibrated thermoluminescent dosimeters by Gamma knife 4C and Theratron 780-C units as gamma emitters in low dose conditions and moreover compared the response of both calibration curves to consider possibility of using every device’s calibration curves instead of the other instrument.
Materials and Methods: Calibration curves of Theratron 780-C machine and Gamma knife 4C unit were measured and plotted in low dose conditions. In order to conduct individual calibration, TLDs were exposed with dose of 100 cGy and through group calibration, dosimeters were divided into 7 groups and were exposed with doses of 0-12 cGy in both machines. To evaluate TLD response by changing field size, TLDs were irradiated with different field sizes in Theratron 780-C and with different collimator sizes in Gamma knife 4C. The best fitting curves were obtained with Excell and Matlab software.
Results: By complying with the best fitting curves for the TLD-100 and conforming to Fisher's test, calculated p-value was 0.92, which was greater than 0.05, therefore the difference is not significant between two calibration curves.
Conclusions: Regardless of differences in calibration conditions between Theratron 780-C machine and Gamma Knife 4C unit, the results showed that every one of these devices can be replaced and used to estimate the unknown dose both in stereotactic radiosurgery and radiotherapy. -
Purpose: The goal of this study is to introduce a quantified feature for investigating the quality manner and interaction between the immune system and tumor cell.
Methods: For this purpose, we introduced an agent based model which uses two agents consisting tumor cell and CD8+ cells and the environment which consists IL-2 and TGF-β cytokines. This model works using a variety of ratios. The most important ratio of this model is the tumor’s proliferation ratio.
Results: We investigated this ratio in three states of tumor-immune system interaction consisting elimination, equilibrium and escape using a raw model, then this ratio was investigated using models which were optimized by experimental data.
Conclusion: The results showed that if the model is leaning to the elimination state, this ratio falls faster and if is leaning to the escape state, this ratio will reduce slowly. The result was proved by models which used experimental data for optimizing. Therefore, using this ratio we can compare different manners of tumor-immune system interactions.
