[22] http://rad.usuhs.edu/medpix , Medical Image Database for radiology[23] http://info.med.yale.edu/intmed/cardio/ ,Yale School of medicine.EE 5359 Project-Pattern Recognition Diagnostic using Phase Only Correlation technique . submitted byThejaswini Purushotham1000616811Pattern Recognition Diagnostic using Phase Only Correlation techniqueObjective: The objective of the thesis is to achieve diagnosis on medical imaging.Motivation:Diagnosis based on medical imaging means making the diagnosis after observing, analyzing, inducing and synthesizing the medical images. Traditional diagnosis based on medical imaging makes diagnosis through doctor’s observation of medical images of all types of medical imaging equipments, to get help from doctors’ professional levels and clinical experience. As doctor’s observation will have limitations inevitably, different doctors with different professional levels and clinical experience may have a case to make different diagnostic results, resulting in misdiagnosis. Moreover, the subjectivity omissions are inevitable and the timeliness of diagnosis can be assured, these restrictions more or less impact the better development of diagnosis based on medical imaging [6]. Details: The schematic for the experimental set up is as shown in Fig .1Fig. 1 Experimental setup for medical image diagnostics.An image database has to be maintained which includes images of the subjects under question. These images are stored in the portable gray map(PGM) file format. The medical images can be X-ray images of bones or electroencephalogram images. Since the images in the database can be modeled as two dimensional arrays,the two dimension fast Fourier transform(2D FFTs) of the images can be calculated. The 2D FFTs are then fed to the phase only correlation(POC) algorithm to generate the correlation graph. Decision about the possible defect in the subject’s medical image can be made deciding on the correlation graph. OVERVIEW OF PHASE ONLY CORRELATIONIn general both the magnitude and the phase are needed to completelydescribe a function in the frequency domain. Sometimes, only information regarding the magnitudes is displayed, such as in the power spectrum, where phase information is completely discarded. However when the relative roles played by the phase and the magnitude in the Fourier domain are examined, it is found that the phase information is considerably more important than the magnitude in preserving the features of an image pattern [3].The Fourier synthesis using full-magnitude information with a uniform phase resulted in nothing meaningful as compared to the original images . Inspired by the above findings, investigations of the use of phase-only information for matched filters or pattern recognition have been carried out. It is found that the phase only approach produces a sharper correlation peak [3].Consider two n1 x n2 images, f(n1 , n2 ) and g(n1 , n2 ) where we assume that the index range are n1 =-M1.…….M1(M1>0) and n2=-M2.….M2(M2>0) for mathematical simplicity, and hence n1=2 x M1+1 and n2=2 x m2+1[4].Let Denote the two dimension3 discrete Fourier transforms(2D DFT) of the two images. are given by(1)(2)1NW)2exp(1Nj,2NW)2exp(2Nj are the phase components.(3) denotes the phase difference .The ordinary correlation function is given by the two dimension inverse discrete Fourier transform(IDFT) of and is given by(4) is the 2 D inverse Fourier transform of On the other hand, the cross phase spectrum is defined as(5)The phase only correlation(POC) function is the 2D IDFT of and isgiven by (6)When and are the same image, i.e, , the POC function will be given by (7)The equation (7) implies that the POC function between two identical images is the kronecker’s delta function .The most remarkable property of POC compared to the ordinary correlation is its accuracy in image matching. When two images are similar, their POC function gives a distinct sharp peak. When two images are not similar, the peak drops significantly. Thus , the POC function exhibits much higher discrimination capability than the ordinary correlation function. The height of the peak can be used as a good similarity measure for image matching. The other properties of the POC function used here are the invariance to image shift and brightness change, and highly robust against noise.(1) Property of shift invarianceLet be the displaced version of the original image then , (8)where are the displacements. The POC function between and will be given by(9)The equation (9) shows that the correlation peak is shifted by and the value of the peak is invariant with respect to the positional image translation. We can estimate image displacement from the equation (9).(2) Property of brightness invarianceSuppose that is the brightness-scaled image of (10)The equation (12)implies that the POC function is not influenced by brightness change.Fig 3: Simulation result for the images in Fig 5.Fig 2:(a) and (b) are the X-ray images of the same chest with variation in illumination. (c) POC graphFig.4:POC function between two identical images along the vertical axis. The horizontal axes represent the spatial domain of size n1 x n2 [4]Fig.5:POC function between two dissimilar images along the vertical axis. The horizontal axes represent the spatial domain of size n1 x n2 [4]Application of POC for pulmonary emphysema detection. There are 80 million patents with developed pulmonary emphysema all over the world, and 3 million patients are dying every year[9] .Pulmonary emphysema is a disease that Pulmonary alveoli destroyed on the ground of chronic smoking custom.Stages of emphysema development [12]The various stages of emphysema include: At-risk Mild emphysema Moderate emphysema Severe emphysema. At-RiskIn the at-risk stage of emphysema, the breathing test is normal. Mild symptoms of at-risk emphysema include a chronic cough and sputum production. Mild EmphysemaIn the mild stage of emphysema, the breathing test shows mild airflow limitation. Symptoms may include a chronic cough and sputum production. At this stage of emphysema, you may not be aware that airflow in your lungs is reduced.Moderate EmphysemaIn the moderate stage of emphysema, the breathing test shows a worsening airflow limitation. Usually the symptoms have increased. Shortness of breath usually develops when working hard, walking fast, or doing other brisk activity. At
View Full Document
Unlocking...