Parametric Image

About: Parametric Image is a research topic. Over the lifetime, 311 publications have been published within this topic receiving 6095 citations.

Imagewise model fitting for generating parametric images in dynamic PET studies

Abstract: In this study, we explore the use of non-linear regression for model fitting of PET measured kinetics on a pixel-by-pixel basis for generating parametric images of micro-parameters of kinetic models. We evaluate quantitatively the noise propagation of two regression methods using computer simulated data, and examine the feasibility of generating parametric images for two different real PET studies -- a human FDG study and a monkey FDOPA study. The results demonstrated that general image-wise model fitting is practically feasible for dynamic PET studies.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Theoretical analysis of lesion detectability in penalized maximum-likelihood patlak parametric image reconstruction using dynamic PET

Abstract: Detecting cancerous lesion is a major clinical application in emission tomography. In previous work, we have studied penalized maximum-likelihood (PML) image reconstruction for lesion detection in static PET. Here we extend our theoretical analysis of static PET reconstruction to dynamic PET. We study both the conventional indirect reconstruction and direct reconstruction for Patlak parametric image estimation. In indirect reconstruction, Patlak parametric images are generated by reconstructing a sequence of dynamic PET images first and then performing Patlak analysis on the time activity curves (TACs) pixel-by-pixel. In direct reconstruction, Patlak parametric images are estimated directly from raw sinogram data by incorporating the Patlak model into the image reconstruction procedure. PML reconstruction is used in both the indirect and direct reconstruction methods. We use a channelized Hotelling observer (CHO) to assess lesion detectability in the Patlak slope image. Simplified expressions for evaluating the lesion detectability have been derived and applied to the selection of the regularization parameter value to maximize the lesion detectability. The proposed method is validated using computer-based Monte Carlo simulation. Good agreements between theoretical predictions and Monte Carlo results are observed. The theoretical formula also shows the benefit of the direct method in dynamic PET reconstruction for lesion detection.

The Magnification for Optical Parametric Image Conversion in Thin Nonlinear Materials

Abstract: T.he relation between the longitudinal, transverse and angular magnifications in optical parametric image conversion was presented. These obey relations quite similar to the Maxwell elongation and Smith-Helmholtz formulas in geometrical optics. The fundamental equation for analyses of spherical aberrations wftc s ac lso given. 1. IRtroduction The up-conversion of infrared li.ght to the visible by means of an optical. parametric process in a nonlinear crystal has been studied in detail by severa1 1nvestlgators. In the range of infrared wavelengths that can be upconverted for a given pump wavelength, Warneri) d.iscussed the directional characteristics and the required geometry for phase-matched up-conversion in terms of the orientations of the various wave vectors with respect to the crystalline axis. IMidwinter2) proposed a means of broad-band, high resolution and high eMciency image conversion and pointed out that an image up-converter competitive with existing scanning photodetectors (such as lnSb detectors) in the 1 to 10 ptm band can be built. Firester3> demonstrated that th.e effect of the pump beam divergence did not degrade the resolution but changed the transverse and longitudinai magnification of the image by a paraxial ray-tracing anaiysis. Also, he discussed the dependence on the system parameters of the converted image resolution, location and chromatic aberration in the case where the pump is at infinity by the Fourier transform theory‘〉, The factors that }.imit the resolution of the upconverted image, the efliciency of up-conversion and several characteristics of six nonliRear crystals were analyzed by Andrews5). However, the general questions of aberra{ions have not been considered6). The purpose of this paper is to show a fundament’al equation aRd the relation between the longitudinal, transverse and angular magnifications for optical parametric interaction in th.in nonlinear mate.rials. “S“ @”P’his investigatien was supported in part by a Resea.rch Gant from the Ilapanese Eclucational Ministry, No. 85070 of 1970. 一d ac Department of Electronic lt.ngineering, Hol〈1〈aiclo University, Sapporo, Japan. 28 Ichiro SAKURABA 2 2. Optical Parametric lmage Conversion in lnfinitesimally Thick Nonlinear Materials Image up-conversion is possible in materiais where the d.ielectyic susceptibility coefflcients which are frequency-dependent tensor elements, are sensitive to directions of the various optical fieid and propagation vectors with respect to crystal axes. The first order nonlinear.ity z(2) couples signai and pump waves and generates a nonligear polarizatlon Pi at the idler frequency fi Pt= Z(2) E.p E,s, (1) in the case of perfectly phase-matcked up-conversion ノアール==ノ~,十ノ~, (2) ki=kp十ks, (3) and E, and E, are the electric fields at pump frequency f. and signal frequeHcy f,, respectively, and k is the corresponding wave vector. For a crystal of a width zv the phase-matched up-coRversion takes place as long as7) iAkl = lkp Nr ks-kil .〈.= 2ni /tv (4) where for convenieRce it is assumed that dk is 一一“’一一“’一一一一一一;.;.;7fAk algng.thg directi.on of ki (see Fig. 1). This t’ polarization radiates a wave at a frequency ft ks/ Y / Which produces the upconverted imag6. θθ’ @/ th夏ll、羅lll糠よ鷲s濃e。盤謡塩l kp pump beam direction), and the angle e’ which Fig. 1 Schematic diagram of up-conver一 the idler wave make’s with the optic axis are sion geometry. related by3) ti’一 lf,,”e (s) where馬andλs are the optical. wave lengthes at freq.uencies/li, and/1,,, respectivel.y. Consider aR iRfinitesimal thickness of isotropic, perfectly phase-matched, Roniinear material that is perpendicular to a line connecting a point object and point-source pump. This thin plate is a distance x, from the pump of frequency f, and a distaRce x, from the object of frequency / as shown iR Figs. 2 and 3. The distance from O to the point of interaction Q is y. lt is assumed that the spherical wavefronts originating at points P and S intersect at point Q and they NONUNEAR kp, ’ MEDIUM ’

Rapid assessment of parametric PET images with computer observers

Abstract: The theoretical formulae based only on computable first and second-order reconstruction statistics have recently been proposed in literature as a relatively rapid method to evaluate relevant figures of merit. In this paper, we extend the theoretical assessment approach from static to dynamic PET images. We consider a detection task of a SEK/BKE and variable signal location. The extended theoretical tools can accommodate different forms of spatial-temporal processing as well as model observer. The quality of single parametric image resulted from two forms of popular temporal processing is assessed and compared. Our theoretical results reveal that the FOM of applying computer observers on a single static image is inferior to that of on the parametric image obtained by Patlak analysis of multiple frame dynamic PET under certain condition.

A feasibility study on the development of ultrasonic parametric imaging based on Nakagami statistical model

Abstract: Nakagami parameter calculated from those received echoes in tissues has been demonstrated to be able to encompass various scattering conditions. To evaluate the feasibility of applying the Nakagami statistical moded to form an ultrasonic parametric image, computer simulations were carried out to design the algorithm and its associated new parameter m/sub v/. Measurements of a tissue-mimicking phantom were performed to evaluate the feasibility of Nakagami image. Simulated and experimental B-mode images of 5 MHz were obtained and processed using the modified algorithm we designed. The simulated results showed that the average of m/sub v/ parameters were increased from 0.50 /spl plusmn/ 0.0026 to 0.68 /spl plusmn/ 0.0204 corresponding to the increase of scatterer concentrations ranged from 2 to 32 scatterers/mm/sup 2/. Furthermore, the parametric image obtained from simulations and measurements is able to localize clearly the fine needle better than that of the B-mode image. Its capabilities for detecting variation of scatterer concentration and strong scatterers make the Nakagami image able to characterize tissues more quantitatively than conventional B-mode imaging.