Background: Delivering the radiation dose to the target volume and minimizing the dose to normal tissues are the main objectives in radiotherapy. The aim of our study is to enhance the CONTRAST of the portal image to increase the accuracy of delineation of the organs in the irradiation field. Methods: The software was written based on local ENHANCEMENT of the pixel values in image matrix. The portal images were digitized by charged coupled device (CCD) in compatible format to be read with this program. This program was applied as an m-file in MATLAB imaging tool box to the matrices of the portal images. The imaging parameters before and after application of the program were compared. Results: The quantitative information of images was obtained. Analysis of the mean and standard deviations of the results has shown that the difference of the criteria between two groups of the images is significant (p< 0.01). In qualitative analysis, final images scores were based on “special weight “. The result of this test confirms the superior quality of the post-processed images from the professional view point. Conclusion: Superiority of final images within the three studied parameters by the experts (superiority of lung image, superiority of thorax and its soft tissue images) can be used to increase the accuracy of the treatment set up and decrease the probability of normal tissue complications.

In this paper, an adaptive image CONTRAST ENHANCEMENT algorithm based on an optimization problem in two dimensional histogram domain is presented. To reduce the unwanted effects of the histogram adjustment, through this optimization-similar to the other methods- the 2D histogram of enhanced image is found in close proximity to input image histogram and uniform distribution, simultaneously. In addition, different from the other methods, by adaptive adjusting the components of a weight matrix, local information is counted. Experimental results in the quantitative and qualitative assessments on a wide range of images demonstrate the performance of the proposed method. Tests have shown that with the addition of the adaptive adjusting the weights, the average performance in CONTRAST ENHANCEMENT increases 75 and 3 percent from the viewpoint of the AMBE_N and DE_N, respectively.

Introduction: Breast cancer is one of the most common types of cancer among women. Early detection of breast cancer is the key to reducing the associated mortality rate. The presence of microcalcifications clusters (MCCs) is one of the earliest signs of breast cancer. Due to poor imaging CONTRAST of mammograms and noise contamination, radiologists may overlook some diagnostic signs, specially the presence of MCCs. In order to improve cancer detection, image ENHANCEMENT methods are often used to aid radiologists. In this paper, a new ENHANCEMENT method was presented for the accurate and early detection of MCCs in mammograms.Materials and Methods: The proposed system consisted of four main steps including: 1) image scaling; 2) breast region segmentation; 3) noise cancellation using a filter, which is sensitive to MCCs; and 4) CONTRAST ENHANCEMENT of mammograms using CONTRAST-Limited Adaptive Histogram Equalization (CLAHE) and wavelet transform.To evaluate this method, 120 clinical mammograms were used.Results: To evaluate the performance of the image ENHANCEMENT algorithm, CONTRAST improvement index (CII) was used. The proposed ENHANCEMENT method in this research achieved the highest CII in comparison with other methods applied in this study. The Validity of the results was confirmed by an expert radiologist through visual inspection.Conclusion: Detection of MCCs significantly improved in CONTRAST-enhanced mammograms. The proposed method could be helpful for radiologists to easily detect MCCs; it could also decrease the number of biopsies and reduce the frequency of clinical misdiagnosis. Moreover, it could be useful prior to segmentation or classification stages.

Background: Gold nanoparticles with high atomic number and density have good potential to be used as CONTRAST media in computed tomography. Objectives: In this study, we aimed to assess radiation dose and CONTRAST ENHANCEMENT performance of gold nanoparticles by measuring CONTRAST to noise ratio compared to clinically used iodinated CONTRAST agents at same concentrations. CONTRAST ENHANCEMENT was evaluated in diff erent tube voltages and currents. Methods: First, polyethylene glycol coated gold nanoparticles were synthesized with concentrations of 0. 5 mM, 0. 6 mM, and 0. 7 mM. Gold nanoparticles and iodinated CONTRAST media were scanned with CT imaging system at diff erent tube voltages and timecurrent product. CT dose index (CTDI) value was measured by special phantom and electrometer. Improving in image CONTRAST was assessed by CONTRAST to noise ratio. Results: Results showed that gold nanoparticles in all concentrations and energies from 80 to 130 kVp display higher image CONTRASTto-noise ratio (CNR) than iodinated CONTRAST media. Image CNR was increased by increasing kVp and mAs. The CNR value was maximum at the voltage of 80 and 130 kVp for iodinated compounds and gold nanoparticles, respectively. The CNR value for gold nanoparticles at 130 kVp and 200 mAs was approximately fi ve times higher than that of iodinated compounds. Conclusion: Gold nanoparticles could be a good candidate for optimizing CT imaging by lowering radiation dose as low as possible while enhancing the image CONTRAST.

In this paper, a general framework for image CONTRAST ENHANCEMENT algorithm based on an optimization problem is presented. Through this optimization, the intensities can be better distributed. The algorithm is based on the facts that the histogram of the enhanced image is close to the input image histogram and uniform distribution, simultaneously. Based on this fact, we obtain a closed form optimal solution for the histogram of the enhanced image. Experimental results in a wide range of images demonstrate the high-performance of the proposed method.

The present study is devoted to the development of a new magnetic resonance CONTRAST agent based on superparamagnetic magnetite nanoparticles. The aim of the study is to create a CONTRAST agent with improved characteristics compared to existing analogues. The process of obtaining includes two main stages such as the formation of the embryo and the growth of particles by aggregation. The size of the nanoparticles was controlled to achieve superparamagnetism. The concentration of iron in the solution was determined by X-ray fluorescence analysis. The phase composition was confirmed by X-ray phase analysis. Transmission electron microscopy and proton relaxometry were employed to evaluate the obtained solutions. The study showed that the optimal concentration of superparamagnetic nanoparticles in an aqueous solution is 0.5 mg/mL. The relaxation abilities of the synthesized particles were determined: for superparamagnetic particles (5-8 nm) - t ≈: 12.1 l/(mmol·s), t ≈: 30.1 l/(mmol·s); for ferrimagnetic particles (30-50 nm) - t ≈: 3.2 l/(mmol·s), t ≈: 35 l/(mmol·s). The cytotoxicity of the obtained nanoparticles was evaluated using an MTT test on fibroblast cells. It was found that at concentrations lower than 0.5 mg/mL, the particles do not exhibit a toxic effect on normal fibroblast cells. The research results demonstrate the feasibility of creating a new CONTRAST agent for MR tomography based on synthesized nanoparticles of complex iron oxide. The developed CONTRAST agent outperforms existing analogues in its characteristics and shows promising results in terms of biocompatibility.

Using adaptive minimum variance beamforming (MV) results in a significant improvement in image resolution, but it’s success in enhancing CONTRAST has not yet been satisfactory. In some researches, eigenspace-based minimum variance beamforming (EIBMV) method has been applied to medical ultrasound imaging system, so that it has improved image CONTRAST while maintaining its resolution. In this paper we apply another eigenspace-based beamforming called eigencanceler (EC) and show it can yield more satisfactory results. However EC needs the noise –interference covariance matrix, whereas the MV and EIBMV use the data covariance matrix. So an altered EC is proposed for the ultrasound imaging. In this method, while canceling the desired signal does not occur, any weight vector is considered to lie in the noise subspace, the subspace orthogonal to the dominant eigenvectors. Otherwise, the weight vector is defined uniformly. Simulation results show the superiority of this method over the MV and EIBMV methods in the CONTRAST aspect.Moreover, the method is more robust against the sound speed errors and can obtain images with better definition of boundaries.

Objectives Vertical root fracture (VRF) is a common complication in endodontically-treated teeth. Due to its poor prognosis, a valid and reliable detection method is imperative for treatment planning. The aim of this study was to evaluate the application of reverse CONTRAST in diagnosis of VRF by digital radiography. Methods Fifty extracted single-rooted premolar teeth were selected for this in-vitro experimental study. The teeth were mounted in a dry mandible and fixed with wax. Radiographs were obtained of all teeth with 0° horizontal angle, and 0° and +15° vertical angle. VRFs were then created by a hammer in vertical direction. Radiographs were obtained again as previously described. Radiographs of each tooth were evaluated twice: once without reverse CONTRAST and then with reverse CONTRAST 2 weeks later. The weighted kappa coefficient was calculated to assess the inter-observer agreement. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+) and negative likelihood ratio (LR-) were compared in use and no use of reverse CONTRAST using the Cochrane Q test. Results Radiographic angle had no significant effect on the diagnostic accuracy in use or no use of reverse CONTRAST, except for the sensitivity value in no use of reverse CONTRAST which was significantly higher in 15° vertical angle. The diagnostic accuracy of images enhanced with reverse CONTRAST had no significant difference with original images in 0° and 15° vertical angles. Conclusion Radiographs enhanced with reverse CONTRAST had no significant difference with original radiographs for diagnosis of VRFs. Thus, for detection of VRFs, reverse CONTRAST should only be considered as an adjunct.

In this paper, a two stage synthetic aperture sequential beamforming (SASB) is presented to abtain better lateral resolution besides more range independent lateral resolution and CONTRAST ENHANCEMENT compared to dynamic receive focusing (DRF) method. Proposed two stage beamforming includes two sequential beamformers. First, a set of B-mode image lines using a single focal point in both transmit and receive are stored. The second stage uses the focused image lines from the first stage as input data, so a high resolution image will be obtained. Obtained results show for the lateral resolution (in terms of FWHM) there is improvement of almost a factor of 2. 5 (dB 6) compared to DRF method. The proposed method on average improves 5 dB and 60% in CONTRAST ratio (CR) and CONTRAST to noise ratio (CNR) compared to DRF method, respectively. Also, the SASB image for the simulated phantom clearly shows the 2 mm diameter cyst which is not detectable in the DRF image.

Background: Sensitivity and resolution are two main parameters that have to be measured in gel dosimetry. However, the resolution in gel is strongly dependant on gel composition. Selection of optimum method in dose response readout and proper values of parameters can result in noise reduction as well as improvement of CONTRAST, and spatial resolution considerably. Materials and Methods: MAGICA polymer gel dosimeters were manufactured and irradiated to different doses using a 60Co therapy unit. Imaging was performed in a 0.5T MRI with 8 echoes in air and water as a hydrogenous environment. Imaging condition was kept constant, as much as possible, in both imaging modalities. Results: Images obtained from these two procedures were compared quantitatively. R2- dose curves have three different sections, sensitivity obtained in these three sections were 1.039, 1.671, 1.260 Gy-1S-1 and 1.032, 1.729, 1.37 Gy-1S-1 for water and air respectively. Calibration errors were investigated and graphically were compared in two different methods. Conclusion: Imaging in water medium for doses lower than 17 Gy led to a small reduction in spatial resolution was exchanged to a considerable increase of CONTRAST in R2 map. For doses higher than17 Gy, imaging in water or air was preferred depending on the importance of CONTRAST or spatial resolution.