By Topic

Medical Imaging, IEEE Transactions on

Issue 7 • Date July 2000

Filter Results

Displaying Results 1 - 12 of 12
  • Nondistorting flattening maps and the 3-D visualization of colon CT images

    Publication Year: 2000 , Page(s): 665 - 670
    Cited by:  Papers (23)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (297 KB)  

    Considers a novel three-dimensional (3-D) visualization technique based on surface flattening for virtual colonoscopy. Such visualization methods could be important in virtual colonoscopy because they have the potential for noninvasively determining the presence of polyps and other pathologies. Further, the authors demonstrate a method that presents a surface scan of the entire colon as a cine, and affords the viewer the opportunity to examine each point on the surface without distortion. The authors use certain angle-preserving mappings from differential geometry to derive an explicit method for flattening surfaces obtained from 3-D colon computed tomography (CT) imagery. Indeed, the authors describe a general method based on a discretization of the Laplace-Beltrami operator for flattening a surface into the plane in a conformal manner. From a triangulated surface representation of the colon, the authors indicate how the procedure may be implemented using a finite element technique, which takes into account special boundary conditions. They also provide simple formulas that may be used in a real-time cine to correct for distortion. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Correction of MR k-space data corrupted by spike noise

    Publication Year: 2000 , Page(s): 671 - 680
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (821 KB)  

    Magnetic resonance images are reconstructed from digitized raw data, which are collected in the spatial-frequency domain (also called k-space). Occasionally, single or multiple data points in the k-space data are corrupted by spike noise, causing striation artifacts in images. Thresholding methods for detecting corrupted data points can fail because of small alterations, especially for data points in the low spatial frequency area where the k-space variation is large. Restoration of corrupted data points using interpolations of neighboring pixels can give incorrect results. The authors propose a Fourier transform method for detecting and restoring corrupted data points using a window filter derived from the striation-artifact structure in an image or an intermediate domain. The method provides an analytical solution for the alteration at each corrupted data point. It can effectively restore corrupted k-space data, removing striation artifacts in images, provided that the following 3 conditions are satisfied. First, a region of known signal distribution (for example, air background) is visible in either the image or the intermediate domain so that it can be selected using a window filter. Second, multiple spikes are separated by the full-width at half-maximum of the point spread function for the window filter. Third, the magnitude of a spike is larger than the minimum detectable value determined by the window filter and the standard deviation of k-space random noise. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An inverse problem approach to the correction of distortion in EPI images

    Publication Year: 2000 , Page(s): 681 - 689
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (594 KB)  

    Magnetic resonance imaging using the echo planar imaging (EPI) technique is particularly sensitive to main (B 0) field inhomogeneities. The primary effect is geometrical distortion in the phase encoding direction. Here, the authors present a method based on the conjugate gradient algorithm to correct for this geometrical distortion, by solving the EPI imaging equation. Two versions are presented: one that attempts to solve the full four-dimensional (4-D) imaging equation, and one that independently solves for each profile along the blip encoding direction. Results are presented for both phantom and in vivo brain EPI images and compared with other proposed correction methods. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Real-time image reconstruction for spiral MRI using fixed-point calculation

    Publication Year: 2000 , Page(s): 690 - 698
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (322 KB)  

    Because spiral magnetic resonance imaging (MRI) is more robust to motion artifacts than echo planar imaging (EPI), spiral imaging method is more suitable in real-time imaging applications where dynamic processes are to be observed. The major hurdle to use spiral imaging method in real-time applications is its slow reconstruction speed. Since spiral trajectories do not sample data on rectilinear grids, raw data must be regridded before inverse fast Fourier transform (FFT). At present, the computational cost for the spiral reconstruction algorithm is still too high and it is not fast enough to achieve the minimum speed requirement of 20 frames/s for real-time imaging applications. Here, the authors propose to replace floating-point calculations with fixed-point calculations in the reconstruction algorithm to remove the computational bottlenecks. To overcome the quantization and round-off errors introduced by fixed-point calculations, the authors devise a method to find the optimal precision for the fixed-point representation. Adding with a highly efficient vector-radix two-dimensional (2-D) FFT algorithm and modifications to speed up the gridding convolution, the authors have cut the reconstruction time by 42% and achieved real-time reconstruction at 30 frames/s for 128×128 matrices on low-cost PC's. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Interpolation of 3-D binary images based on morphological skeletonization

    Publication Year: 2000 , Page(s): 699 - 710
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (674 KB)  

    The morphological skeleton interpolation (MSI) algorithm is presented. It is an efficient, shape-based interpolation method used for interpolating slices in a three-dimensional (3-D) binary object. It is based on morphological skeletonization, which is used for two-dimensional (2-D) slice representation. The proposed morphological skeleton matching process provides translation, rotation, and scaling information at the same time. The interpolated slices preserve the shape of the original object slices, when the slices have similar shapes. It can also modify the shape of an object when the successive slices do not have similar shapes. Applications on artificial and real data are also presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Morphology-based three-dimensional interpolation

    Publication Year: 2000 , Page(s): 711 - 721
    Cited by:  Papers (19)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (546 KB)  

    In many medical applications, the number of available two-dimensional (2-D) images is always insufficient. Therefore, the three-dimensional (3-D) reconstruction must be accomplished by appropriate interpolation methods to fill gaps between available image slices. Here, the authors propose a morphology-based algorithm to interpolate the missing data. The proposed algorithm consists of several steps. First, the object or hole contours are extracted using conventional image-processing techniques. Second, the object or hole matching issue is evaluated. Prior to interpolation, the centroids of the objects are aligned. Next, the authors employ a dilation operator to transform digital images into distance maps and they correct the distance maps if required. Finally, the authors utilize an erosion operator to accomplish the interpolation. Furthermore, if multiple objects or holes are interpolated, they blend them together to complete the algorithm. The authors experimentally evaluate the proposed method against various synthesized cases reported in the literature. Experimental results show that the proposed method is able to handle general object interpolation effectively. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An imaging system with calibrated color image acquisition for use in dermatology

    Publication Year: 2000 , Page(s): 722 - 730
    Cited by:  Papers (43)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1014 KB)  

    The authors propose a novel imaging system useful in dermatology, more precisely, for the follow-up of patients with an increased risk of skin cancer. The system consists of a Pentium PC equipped with an RGB frame grabber, a three-chip charge coupled devices (CCD) camera controlled by the serial port and equipped with a zoom lens and a halogen annular light source. Calibration of the imaging system provides a way to transform the acquired images, which are defined in an unknown color space, to a standard, well-defined color space called SRGB, sRGB has a known relation to the CIE 1 XYZ and CIE L*a*b* colorimetric spaces. These CIE color spaces are based on the human vision, and they allow the computation of a color difference metric called CIE ΔE ab*, which is proportional to the color difference, as seen by a human observer. Several types of polynomial RGB to sRGB transforms will be tried, including some optimized in perceptually uniform color spaces. The use of a standard and well-defined color space also allows meaningful exchange of images, e.g., in teledermatology. The calibration procedure is based on 24 patches with known color properties, and it takes about 5 minutes to perform. It results in a number of settings called a profile that remains valid for tens of hours of operation. Such a profile is checked before acquiring images using just one color patch, and is adjusted on the fly to compensate for short-term drift in the response of the imaging system. Precision or reproducibility of subsequent color measurements is very good with <ΔE ab*>=0.3 and ΔE ab*<1.2. Accuracy compared with spectrophotometric measurements is fair with <ΔE ab*>=6.2 and ΔE ab*><13.3. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Normalization of local contrast in mammograms

    Publication Year: 2000 , Page(s): 731 - 738
    Cited by:  Papers (18)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (251 KB)  

    Equalizing image noise has been shown to be an important step in automatic detection of microcalcifications in digital mammograms. In this study, an accurate adaptive approach for noise equalization is presented and investigated. No additional information obtained from phantom recordings is improved in the method, which makes the approach robust and independent of film type and film development characteristics. Furthermore, it is possible to apply the method on direct digital mammograms as well. In this study, the adaptive approach is optimized by investigating a number of alternative approaches to estimate the image noise. The estimation of high-frequency noise as a function of the grayscale is improved by a new technique for dividing the grayscale in sample intervals and by using a model for additive high-frequency noise. It is shown that the adaptive noise equalization gives substantially better detection results than does a fixed noise equalization. A large database of 245 digitized mammograms with 341 clusters was used for evaluation of the method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Interpolation revisited [medical images application]

    Publication Year: 2000 , Page(s): 739 - 758
    Cited by:  Papers (226)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1096 KB)  

    Based on the theory of approximation, this paper presents a unified analysis of interpolation and resampling techniques. An important issue is the choice of adequate basis functions. The authors show that, contrary to the common belief, those that perform best are not interpolating. By opposition to traditional interpolation, the authors call their use generalized interpolation; they involve a prefiltering step when correctly applied. The authors explain why the approximation order inherent in any basis function is important to limit interpolation artifacts. The decomposition theorem states that any basis function endowed with approximation order ran be expressed as the convolution of a B spline of the same order with another function that has none. This motivates the use of splines and spline-based functions as a tunable way to keep artifacts in check without any significant cost penalty. The authors discuss implementation and performance issues, and they provide experimental evidence to support their claims. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The effect of image distortion on 3-D reconstruction of coronary bypass grafts from angiographic views

    Publication Year: 2000 , Page(s): 759 - 762
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (387 KB)  

    Three-dimensional (3-D) reconstructions of coronary bypass grafts performed from X-ray angiographic images may become increasingly important for the investigation of damaging mechanical stresses imposed to these vessels by the cyclic movement of the heart. Contrary to what the authors had experienced with coronary arteries, appreciable reconstruction artifacts frequently occur with grafts. In order to verify the hypothesis that those are caused by distortions present in the angiographic images (acquired with image intensifiers), the authors have implemented a grid correction technique in their 3-D reconstruction method and studied its efficiency with phantom experiments. In this article, the nature of the encountered artifacts and the way in which the dewarping correction eliminates them are illustrated by a phantom experiment and by the reconstruction of a real coronary bypass vein graft. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Segmenting skin lesions with partial-differential-equations-based image processing algorithms

    Publication Year: 2000 , Page(s): 763 - 767
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (221 KB)  

    A partial-differential equations (PDE)-based system for detecting the boundary of skin lesions in digital clinical skin images is presented. The image is first preprocessed via contrast-enhancement and anisotropic diffusion. If the lesion is covered by hairs, a PDE-based continuous morphological filter that removes them is used as an additional preprocessing step. Following these steps, the skin lesion is segmented either by the geodesic active contours model or the geodesic edge tracing approach. These techniques are based on computing, again via PDEs, a geodesic curve in a space defined by the image content. Examples showing the performance of the algorithm are given. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Quantitative and kinetic evolution of wound healing through image analysis

    Publication Year: 2000 , Page(s): 767 - 772
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    To define a healing function based on parameters measured on digitized images of wounds, and to use it to compare the rate of healing of two skin graft donor sites, one treated with petrolatum gauze (Pg) and the other with a topical preparation containing alginates (A). Digital photographs of donor sites (depth 0.6 mm) taken every two days between day 6 and day 12 were analyzed blind using the same algorithm, following changes in color and homogeneity. Analysis of variance was used to identify those parameters that changed during heating. The healing function was constructed using measurements made in six patients (group 1) randomly chosen from ten requiring skin grafts, and was applied and validated using data from the remaining four patients (group 2). The results given by this healing function were compared with those provided by principal component analysis. The most significant healing parameters were those measuring wound homogeneity, and our healing function reflects how these change with time. The time-dependent curves of the function calculated for groups 1 and 2 matched well enough to be considered as being derived from the same set of measurements. The results given by this healing function explained, by analogy, the meaning of the first principal component of principal component analysis. From day 6 to day 12, the healing function followed the same time-course for the Pg and A treatments, but healing was achieved significantly earlier (4 days, p<0.03) with A. This suggests that the effect of A on wound healing is achieved in the first six days, before the visual changes from epidermalization are analyzed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Transactions on Medical Imaging (T-MI) encourages the submission of manuscripts on imaging of body structures, morphology and function, and imaging of microscopic biological entities. The journal publishes original contributions on medical imaging achieved by various modalities, such as ultrasound, X-rays (including CT) magnetic resonance, radionuclides, microwaves, and light, as well as medical image processing and analysis, visualization, pattern recognition, and related methods. Studies involving highly technical perspectives are most welcome. The journal focuses on a unified common ground where instrumentation, systems, components, hardware and software, mathematics and physics contribute to the studies.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Michael Insana
Beckman Institute for Advanced Science and Technology
Department of Bioengineering
University of Illinois at Urbana-Champaign
Urbana, IL 61801 USA
m.f.i@ieee.org