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At least 541 records · Page 30Linked to original sources
PubMed1991

[The tracing of brain tissue and 3-D imaging display CT image application: 3-D recursive tracing].

The size and the shape of brain tissue offer lots of information for clinical diagnosis and treatment. The commercial imaging systems, such as x-ray computer tomography (CT) and magnetic resonant image (MRI), always display only two dimensional (2-D) image, which makes quantitative diagnosis of the variation of brain tissue very difficult. Furthermore, some tissue may be connected through little vessels, which is also difficult to identify using discrete 2-D image. In this study, we processed CT image data using an general purpose IBM personal computer. A new three dimensional (3-D) recursive tracing algorithm was proposed. This new algorithm can automatically extract the image of brain tissue in each 2-D image. The information obtained was therefore used to reconstruct 3-D image. This system allows user to observe 3-D size and shape of brain tissue from arbitrary view. Such 3-D image can also be used to calculate the volume of tissue. Using overlay projecting method, it can display skin, bone, brain tissue and gray material at the same time. Such display method accurately shows the relative position of each tissue and offer physicians important information for diagnosis and treatment.

Algorithms↗
PubMedDate not supplied

Optimizing brain MR imaging protocols with gadopentetate dimeglumine: enhancement of intracranial lesions on spin-density- and T2-weighted images.

To determine whether long TR MR imaging is best performed before or after IV administration of gadopentetate dimeglumine, we obtained spin-density- and T2-weighted images before and after contrast administration in 21 patients with known intracranial enhancing lesions. Of 25 lesions demonstrating enhancement on T1-weighted sequences, 21 showed mild or moderate enhancement on spin-density-weighted sequences and 20 showed mild enhancement on T2-weighted sequences. Importantly, no spin-density or T2 information was obscured by the administration of gadopentetate dimeglumine, and no T2 shortening effects were visible. Two new foci of enhancement were visible on postcontrast spin-density- and T2-weighted images that were missed on postcontrast T1-weighted images and on precontrast spin-density- and T2-weighted studies. Visualization of new areas of enhancement is the main advantage provided by the long TR images obtained after IV injection of gadopentetate dimeglumine. The most likely reason for the appearance of these newly visualized lesions is thought to be delayed enhancement. This imaging protocol also allows the display of adjacent edema or gliosis and enhancing lesions on a single image. Additionally, in three cases, posterior fossa phase-shift artifacts raised the suspicion of an enhancing lesion on postcontrast T1-weighted images, but the cerebellum was shown to be normal on the postcontrast spin-density- and T2-weighted studies. On the basis of our results, we recommend obtaining long TR images after rather than before the administration of gadopentetate dimeglumine in patients with intracranial enhancing lesions.

Astrocytoma↗
PubMed1991

[Fast MR imaging of liver metastasis using FLASH and FISP--optimal sequences for T1- and T2*-weighted images].

This paper deals with a study to obtain the optimal sequence of gradient echo (GE) for T1- and T2*-weighted images similar to T1- and T2-weighted images of spin echo (SE). Two GE sequences, fast low angle shot (FLASH) and fast imaging with steady-state precession (FISP), were performed in 15 cases of liver metastasis in various combination of flip angle (FA), repetition time (TR), and echo time (TE). The optimal combinations were summarized as follows: 1) T1-weighted FLASH image with FA of 40 degrees, TR of 22 msec and TE of 10 msec, 2) T1-weighted FISP image with FA of 70 degrees, TR of 100 msec, TE of 10 msec, 3) both T2*-weighted FLASH and FISP images with FA of 10 degrees, TR of 100 msec and TE of 30 msec. Not only to provide the adequate T1- and T2*-weighted images but also to enable breath-holding MR imaging, GE sequences can optionally take place SE in cases of deteriorated images caused by moving artifacts. Other applications support the re-examination and further detailing when required, conveniently rather in short time.

Adult↗
PubMed1990

Diffusion-weighted MR imaging of acute stroke: correlation with T2-weighted and magnetic susceptibility-enhanced MR imaging in cats.

We evaluated the temporal and anatomic relationships between changes in diffusion-weighted MR image signal intensity, induced by unilateral occlusion of the middle cerebral artery in cats, and tissue perfusion deficits observed in the same animals on T2-weighted MR images after administration of a nonionic intravascular T2 shortening agent. Diffusion-weighted images obtained with strong diffusion-sensitizing gradient strengths (5.6 gauss/cm, corresponding to gradient attenuation factor, b, values of 1413 sec/mm2) displayed increased signal intensity in the ischemic middle cerebral artery territory less than 1 hr after occlusion, whereas T2-weighted images without contrast usually failed to detect injury for 2-3 hr after stroke. After contrast administration (0.5-1.0 mmol/kg by Dy-DTPA-BMA, IV), however, T2-weighted images revealed perfusion deficits (relative hyperintensity) within 1 hr after middle cerebral artery occlusion that corresponded closely to the anatomic regions of ischemic injury shown on diffusion-weighted MR images. Close correlations were also found between early increases in diffusion-weighted MR image signal intensity and disrupted phosphorus-31 and proton metabolite levels evaluated with surface coil MR spectroscopy, as well as with postmortem histopathology. These data indicate that diffusion-weighted MR images more accurately reflect early-onset pathophysiologic changes induced by acute cerebral ischemia than do T2-weighted spin-echo images.

Acute Disease↗
PubMed1995

[Reconstruction methods for 3D imaging and quantification of intracoronary ultrasound cross-sectional images using biplanar fluoroscopy. Initial experiences in vitro and in vivo].

In this investigation, we studied the feasibility of 3D-reconstruction from 2D cross-sectional intracoronary ultrasound images. A computer-aided, automated 3D-reconstruction was used to generate cylindrical and sagittal format of vessels in vitro (n = 9) and in vivo (n = 48). Ultrasound 2D-images were acquired with a 20 MHz mechanical intracoronary ultrasound catheter (Boston Scientific). A slow pullback (about 1 mm/s) of the catheter was performed during continuous recording of the ultrasound images. The recorded 2D-images were then fed to an image processing computer. Correction and scaling of the axial vessel dimensions was performed by the assessment of the catheter position in the simultaneously recorded biplane fluoroscopy. Digitized data were then processed to 3D-images with use of voxel space modeling. The 3D-views from any plane can be reconstructed. The in-vitro study demonstrated that the reconstructed images were able to correctly portray the pathological changes of the vessel wall in all specimen as proved by pathologic examination. In the in-vivo study, 3D-reconstruction provided not only a spatial visualization of the coronary arterial disorders (such as coronary aneurysm, coronary dissection, spontaneous plaque rupture etc.) but also provides the potential to quantify the mass of lesions. By combining sagittal and cylindrical views, 3D-reconstruction enables longitudinal and orthogonal imaging of the both the vessel lumen and vessel wall, therefore, it has the advantage of cross-sectional viewing as obtained from intracoronary ultrasound and the longitudinal viewing as derived from coronary angiography. These preliminary results of the study indicate that 3D-reconstruction of coronary segments is a promising technique for studying coronary artery disease. Analysis can be based not only on single or multiple cross-sectional images but also on vessel segments facilitating serial studies as for instance studies assessing the progression and regression of atherosclerosis.

Aortic Dissection↗
PubMed1996

[Evaluation of image quality of medical facsimile as a radiological image recording system].

We examined the usefulness of a new medical facsimile (MFAX) system in recording and transmitting various kinds of medical images, including X-ray images and colored histopathologic images. The system consists of an image scanner, a magnetic disk for image storage, a transmission circuit and a thermal image printer. Transmission time for a FCR (Fuji computed radiography) image by super-fine mode was 6 minutes. We used ROC (receiver operating characteristics) curves to evaluate the ability of eight radiologists to detect the small simulated nodules placed on an anthropomorphic chest phantom and shown on MFAX images. The radiologists observed both the FCR films and MFAX copies and determined the presence or absence of simulated nodules using five confidence levels. The results obtained for FCR films and MFAX images showed no statistically significant difference.

Humans↗
PubMed1997

Spiral spin-echo magnetic resonance imaging of the pelvis with spectrally and spatially selective radiofrequency excitation: comparison with fat-saturated fast spin-echo imaging.

OBJECTIVE: The authors describe their initial clinical experience in comparing a spiral spin-echo technique with a fat-saturated fast spin-echo technique for imaging the pelvis. METHODS: A total of 18 patients were imaged with both spiral spin-echo and fat-saturated fast spin-echo magnetic resonance imaging. The spiral spin-echo technique combines a spectrally and spatially selective radiofrequency excitation with a spiral k-space trajectory. This technique permits rapid acquisition of T2-weighted water-only images. RESULTS: The spiral spin-echo images were judged superior to the fat-saturated fast spin-echo images in terms of uniformity of fat suppression and absence of flow-related artifacts. However, the overall image quality of the spiral spin-echo images was inferior to that of the fat-saturated fast spin-echo images, as a result of blurring caused by off resonance effects. The two techniques were judged equivalent in terms of conspicuity of the abnormality and diagnostic information. CONCLUSION: The authors conclude that the spiral spin-echo technique holds promise, particularly if combined with a deblurring algorithm.

Adolescent↗
PubMed2004

Prospective registration of human head magnetic resonance images for reproducible slice positioning using localizer images.

PURPOSE: To facilitate assessing brain tumor growth and progression of stroke lesions by reproducible slice positioning in human head magnetic resonance (MR) images, a method for prospective registration is proposed that adjusts the image slice position without moving the patient and with no additional scans. MATERIALS AND METHODS: The gradient reference frame of follow-up examinations was adjusted to achieve the same image slice positioning relative to the patient as in the previous examination. The three-dimensional geometrical transformation parameters for the gradients were determined using two-dimensional image registration of three orthogonal localizer images. The method was developed and evaluated using a phantom with arbitrarily adjustable position. Feasibility for in vivo applications was demonstrated with brain MR imaging (MRI) of healthy volunteers. RESULTS: Standard retrospective registration was used for assessing the quality of the method. The accuracy of the realignment was 0.0 mm +/- 1.2 mm and -0.2 degrees +/- 0.9 degrees (mean +/- SD) in phantom experiments. In 10 examinations of volunteers, misalignments up to 49.2 mm and 21 degrees were corrected. The accuracy of the realignment after prospective registration was 0.1 mm +/- 1.5 mm and 0.2 degrees +/- 1.5 degrees. CONCLUSION: Image-based prospective registration using localizer images of the pre- and postexaminations is a robust method for reproducible slice positioning.

Brain↗
PubMed2003

Real-time imaging of two-dimensional cardiac strain using a harmonic phase magnetic resonance imaging (HARP-MRI) pulse sequence.

The harmonic phase (HARP) method provides automatic and rapid analysis of tagged magnetic resonance (MR) images for quantification and visualization of myocardial strain. In this article, the development and implementation of a pulse sequence that acquires HARP images in real time are described. In this pulse sequence, a CINE sequence of images with 1-1 spatial modulation of magnetization (SPAMM) tags are acquired during each cardiac cycle, alternating between vertical and horizontal tags in successive heartbeats. An incrementing train of imaging RF flip angles is used to compensate for the decay of the harmonic peaks due to both T(1) relaxation and the applied imaging pulses. The magnitude images displaying coarse anatomy are automatically reconstructed and displayed in real time after each heartbeat. HARP strain images are generated offline at a rate of four images per second; real-time processing should be possible with faster algorithms or computers. A comparison of myocardial contractility in non-breath-hold and breath-hold experiments in normal humans is presented.

Adult↗
PubMed1994

Image analysis and synthesis of multimodal images in medicine.

Radiologic and clinical practice can be enhanced by improved access to multimodal image information. Analysis, visualization, method characteristic image processing and image synthesis is needed not only for the interpretation of the images but also for performing effective consultations with clinical colleagues and computer supported therapy planning and control strategies. A method is presented which enables the fast display, three-dimensional visualization and the modality oriented analysis of multimodal image information. Based on a unique image format, modality specific procedures and two- or three-dimensional processing tools of image analysis produce the input data for therapy planning programs. The easy use of this multimedia visualization tool enables radiologists and clinicians to deal with their image data. The description of methods and procedures, as well as typical examples of radiologic practice will demonstrate the efficiency of the presented system.

Algorithms↗
PubMed1991

Bayesian image processing in magnetic resonance imaging.

In the past several years, image processing techniques based on Bayesian models have received considerable attention. In our earlier work, we developed a novel Bayesian approach which was primarily aimed at the processing and reconstruction of images in positron emission tomography. In this paper, we describe how the technique has been adopted to process magnetic resonance images in order to reduce noise and artifacts, thereby improving image quality. In this framework, the image is assumed to be a statistical variable whose posterior probability density conditional on the observed image is modeled by the product of the likelihood function of the observed data with a prior density based our prior knowledge. A Gibbs random field incorporating local continuity information and with edge-detection capability is used as the prior model. Based on the formalism of the posterior density, we can compute an estimate of the image using an iterative technique. We have implemented this technique and applied it to phantom and clinical images. Our results indicate that the approach works reasonably well for reducing noise, enhancing edges, and removing ringing artifact.

Algorithms↗
PubMed2005

Interleaved silent steady state (ISSS) imaging: a new sparse imaging method applied to auditory fMRI.

The acoustic scanner noise that is generated by rapid gradient switching in echo planar imaging (EPI) is an important confounding factor in auditory fMRI. "Sparse imaging" designs overcome the influence of scanner noise on stimulus presentation by acquiring single brain volumes following a silent stimulus presentation period. However, conventional sparse imaging requires assumptions about the time-to-peak of the evoked hemodynamic response and reduces the amount of EPI data which can be acquired and hence statistical power. In this article, we describe an "interleaved silent steady state" (ISSS) sampling scheme in which we rapidly acquire a set of EPI volumes following each silent stimulus presentation period. We avoid T1-related signal decay during the acquisition of the EPI volumes by maintaining the steady state longitudinal magnetization with a train of silent slice-selective excitation pulses during the silent period, ensuring that signal contrast is constant across successive scans. A validation study comparing ISSS to conventional sparse imaging demonstrates that ISSS imaging provides time course information that is absent in conventional sparse imaging data. The ISSS sequence has a temporal resolution like event-related (ER) imaging within a single trial (unlike conventional sparse imaging, where ER-like temporal resolution can only be achieved by compiling data across many jittered trials of the same stimulus type). This temporal resolution within trials makes ISSS particularly suitable for experiments in which a) scanner noise would interfere with the perception and processing of the stimulus; b) stimuli are several seconds in duration, and activation is expected to evolve and change as the stimulus unfolds; and c) it is impractical to present a single stimulus more than once (for example, repetition priming or familiarity effects would be expected).

Acoustic Stimulation↗
PubMed2002

Comparative study of fast MR imaging: quantitative analysis on image quality and efficiency among various time frames and contrast behaviors.

The purpose of this study is to quantitatively compare the image quality and efficiency provided by widely available fast MR imaging pulse sequences. A composite phantom with various T1 and T2 values and subjected to periodic motion was imaged at 1.5 T. The fast MRI sequences evaluated included fast spin-echo (FSE), single shot fast spin-echo (SSFSE), echo-planar imaging (EPI), multi-slice gradient recalled (MPGR), fast MPGR (FMPGR), and fast multi-slice spoiled gradient echo (FMPSPGR). T1-weighted (T1WI), T2-weighted (T2WI), proton-density-weighted (PDWI), and T2*-weighted (T2*WI) images were evaluated in breath-hold and non-breath-hold time frames. Analysis included measurement of image signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), nonuniformity, ghosting ratio, SNR per unit time and CNR per unit time. Among fast T2WI sequences, FSE with breath-hold time frame resulted in the highest image quality and in superior SNR and CNR efficiency by a factor of 5 or 6 as compared with conventional spin echo sequence. Among fast T1WI sequences, FMPGR and FMPSPGR both with non-breath-hold time frame produced the highest image quality and SNR and CNR efficiency by a factor of greater than 5 as compared with conventional spin echo. Among fast PDWI and T2*WI sequences, FSE produced the highest SNR and CNR, and was maximally efficient with a factors of greater than 6 as compared with conventional spin echo.

Echo-Planar Imaging↗
PubMed2005

[Functional imaging of the lung using a gaseous contrast agent: (3)helium-magnetic resonance imaging].

Current imaging methods of the lung concentrate on morphology as well as on the depiction of the pulmonary parenchyma. The need of an advanced and more subtle imaging technology compared to conventional radiography is met by computed topography as the method of choice. Nevertheless, computed tomography yields very limited functional information. This is to be derived from arterial blood gas analysis, spirometry and body plethysmography. These methods, however, lack the scope for regional allocation of any pathology. Magnetic resonance imaging of the lung has been advanced by the use of hyperpolarised (3)Helium as an inhaled gaseous contrast agent. The inhalation of the gas provides functional data by distribution, diffusion and relaxation of its hyperpolarised state. Because anatomical landmarks of the lung can be visualised as well, functional information can be linked with regional information. Furthermore, the method provides high spatial and temporal resolution and lacks the potential side-effects of ionising radiation. Four different modalities have been established: 1. Spin density imaging studies the distribution of gas, normally after a single inhalation of contrast gas in inspiratory breath hold. 2. Dynamic cine imaging studies the distribution of gas with respect to regional time constants of pulmonary gas inflow. 3. Diffusion weighted imaging can exhibit the presence and severity of pulmonary airspace enlargement, as in pulmonary emphysema. 4. Oxygen sensitive imaging displays intrapulmonary oxygen partial pressure and its distribution. Currently, the method is limited by comparably high costs and limited availability. As there have been recent developments which might bring this modality closer to clinical use, this review article will comprise the methodology as well as the current state of the art and standard of knowledge of magnetic resonance imaging of the lung using hyperpolarised (3)Helium.

Administration, Inhalation↗
PubMed2005

Fast image acquisition and processing on a TV camera-based portal imaging system.

The present paper describes the fast acquisition and processing of portal images directly from a TV camera-based portal imaging device (Siemens Beamview Plus). This approach employs not only hard- and software included in the standard package installed by the manufacturer (in particular the frame grabber card and the Matrox Intellicam interpreter software), but also a software tool developed in-house for further processing and analysis of the images. The technical details are presented, including the source code for the Matrox interpreter script that enables the image capturing process. With this method it is possible to obtain raw images directly from the frame grabber card at an acquisition rate of 15 images per second. The original configuration by the manufacturer allows the acquisition of only a few images over the course of a treatment session. The approach has a wide range of applications, such as quality assurance (QA) of the radiation beam, real-time imaging, real-time verification of intensity-modulated radiation therapy (IMRT) fields, and generation of movies of the radiation field (fluoroscopy mode).

Humans↗
PubMed2000

MR imaging and histologic features of subinsular bright spots on T2-weighted MR images: Virchow-Robin spaces of the extreme capsule and insular cortex.

PURPOSE: To determine the cause and frequency of high-signal-intensity foci detected in the insular cortex and extreme capsule on thin-section, high-spatial-resolution, coronal, T2-weighted magnetic resonance (MR) images. MATERIALS AND METHODS: The authors assessed high-signal-intensity areas in the insular cortex and extreme capsule on coronal MR images obtained in 56 patients with seizure and five control subjects. Images were obtained with thin-section, high-spatial-resolution, T2-weighted, fast spin-echo; three-dimensional, spoiled gradient-recalled-echo; and fluid-attenuated inversion-recovery sequences. In two formalin-fixed brain specimens, MR imaging findings were correlated with gross anatomic and histologic findings. RESULTS: Subinsular bright spots were found in 53 of the 56 (95%) patients (96 of 112 [86%] hemispheres) and all five control subjects. The spots were elliptical in 30 patients, round in 14 patients, linear in 22 patients, and dotlike in seven patients and often had a featherlike configuration. The spots were isointense to cerebrospinal fluid on T2-weighted, fast SE images and were located in the anterior extreme capsule white matter and insular cortex. MR imaging of brain specimens revealed bilateral elliptical areas of high signal intensity that corresponded to small multiple cavities at gross anatomic inspection. At microscopic examination, these cavities were perivascular spaces of mostly arteriolar origin. CONCLUSION: High-signal-intensity subinsular foci at MR imaging are due to enlarged perivascular spaces. In most cases, these foci can be visualized on thin-section, high-spatial-resolution, coronal T2-weighted images; they should not be mistaken for pathologic conditions when they occur unilaterally.

Adolescent↗
PubMed2006

Open microscopy environment and findspots: integrating image informatics with quantitative multidimensional image analysis.

Biomedical research and drug development increasingly involve the extraction of quantitative data from digital microscope images, such as those obtained using fluorescence microscopy. Here, we describe a novel approach for both managing and analyzing such images. The Open Microscopy Environment (OME) is a sophisticated open-source scientific image management database that coordinates the organization, storage, and analysis of the large volumes of image data typically generated by modern imaging methods. We describe FindSpots, a powerful image-analysis package integrated in OME that will be of use to those who wish to identify and measure objects within microscope images or time-lapse movies. The algorithm used in FindSpots is in fact only one of many possible segmentation (object detection) algorithms, and the underlying data model used by OME to capture and store its results can also be used to store results from other segmentation algorithms. In this report, we illustrate how image segmentation can be achieved in OME using one such implementation of a segmentation algorithm, and how this output subsequently can be displayed graphically or processed numerically using a spreadsheet.

Algorithms↗
PubMed2002

[Evaluation of three-dimensional enhanced brain surface imaging using CT (3D surface CT angiography) and magnetic resonance imaging (3D surface MR angiography)].

The optimal imaging conditions for 3D brain surface imaging by magnetic resonance imaging (MRI) and multi-slice CT were investigated. Visualization of the sulci, gyri, and veins on the brain's surface was also compared between 3D surface images acquired using multi-slice CT and conventional single-slice CT and MRI. Various imaging parameters, including slice thickness, dose, and matrix size, were evaluated using our original brain surface phantom and longitudinal direction evaluation phantom as well as images obtained from healthy volunteers. Subjects of the clinical study were patients with arteriovenous malformations and brain tumors who underwent CT-angiography at the same time as MR-angiography. The quality of 3D images of the brain surface is most strongly influenced by partial volume effects related to slice thickness. In multi-slice CT, a slice thickness of 0.5 mm can be employed to minimize the partial volume effect, providing results that are far superior to those that can be achieved by conventional single-slice 3D-CT. In addition, the excellent S/N of multi-slice CT permits the veins on the brain's surface to be clearly visualized without the use of contrast medium. With regard to visualization of the sulci and gyri, although some problems remain to be overcome, multi-slice CT was found to be equivalent to 3D surface imaging using MRI.

Brain↗