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At least 451 records · Page 25Linked to original sources

One-shot dual-energy subtraction chest imaging with computed radiography: clinical evaluation of film images.

A clinical evaluation of one-shot dual-energy subtraction chest imaging by means of computed radiography (CR) with imaging plates was carried out in a comparison with the original plain CR images. In analyses of chest images of 140 patients, new information, not detected on the original plain CR images, was obtained on subtraction images in 21 patients (15%). Receiver operating characteristic curve studies also verified the superiority of CR subtraction over the original plain CR images for the detection of pulmonary nodules, calcification in a nodule, and rib lesions. Subtraction images complemented the original plain images.

Bone Diseases↗

Pancreas and peripancreatic vessels: effect of imaging delay on gadolinium enhancement at dynamic gradient-recalled-echo MR imaging.

PURPOSE: To investigate the effect of imaging delay on gadolinium enhancement of the pancreas and peripancreatic vessels at dynamic gradient-recalled-echo magnetic resonance (MR) imaging of the pancreas. MATERIALS AND METHODS: Dynamic MR images were obtained after intravenous bolus injection of gadopentetate dimeglumine in 75 patients with no pancreatic malignancies. Test-bolus imaging was performed to determine aortic transit time in individual patients. Patients were randomly assigned so that the middle of k space was acquired at 5, 15, 25, 35, or 45 seconds after arrival of contrast material in the abdominal aorta. Mean signal intensities of pancreas, liver, and peripancreatic vessels were measured, and images were qualitatively assessed by two radiologists. RESULTS: The best pancreatic enhancement occurred at a delay of 15 seconds (P <.05). The best enhancement of the liver and peripancreatic vessels occurred at 25 seconds or later (P <.05). Qualitatively, the best images of the pancreas were obtained at 15 seconds, and the best images of the liver and peripancreatic vessels were obtained at 25 seconds or later. CONCLUSION: Biphasic imaging at 15 and 45 seconds or later after arrival of contrast material in the abdominal aorta is a practical method for acquisition of high-quality dynamic gradient-recalled-echo MR images of the pancreas.

Adult↗

Three-dimensional magnetic resonance imaging of lung and liver tumors in mice by use of transversal multislice magnetic resonance images.

PURPOSE: To diagnose lung and liver tumors experimentally induced in mice in three-dimensional magnetic resonance (MR) images constructed by superimposing transversal multislice MR images of thoracic and abdominal regions taken under a high magnetic field of 7.05 tesla (T). METHODS: Lung and liver tumors were induced by administration of urethane to A/J mice and implantation of transplantable colon-26 cells into BALB/c mice, respectively. Two-dimensional (2-D) multislice MR images from the thoracic to abdominal regions were taken under the proton density-weighted conditions. Each organ in the 2-D MR images was pseudocolored, and a three-dimensional (3-D) image was constructed by superimposing them on a UNIX computer, using volume-rendering software. RESULTS: In the normal mouse, each organ in the thoracic and abdominal regions was three-dimensionally imaged and was clearly distinguished from the others. In mice with tumors in the lung or liver, the pathologic changes in the tissue could be visualized in 3-D images. CONCLUSIONS: The MR images three-dimensionally constructed by use of a method combining MR imaging under a high magnetic field of 7.05 T and a computer technique using volume-rendering software was useful for diagnosis of lung and liver tumors experimentally induced in mice.

Abdomen↗

[Implementation of sector imaging mode with high signal-to-noise ratio in the high frame rate ultrasonic imaging system].

The high frame rate (HFR) ultrasonic imaging system, which is developed with limited diffraction beams, constructs images at a high frame rate. However the rectangular imaging area, to some extent, restricts the far field imaging information. At the same time, because of one transmission for constructing image, the system suffers from low SNR. In this paper we present a computationally efficient method to construct sector mode image and to increase the SNR in HFR system. The method uses Golay complementary sequence as excitation to realize two transmission events. Each event simultaneously transmits two plane waves with different transmission angle. Then the received echo signals related to different angle are separated according to orthogonality of Golay complementary sequence and used to construct two images of different area by HFR method. Finally the two images are synthesized to one frame of sector mode image.

Image Enhancement↗

Image acquisition: ultrasound, computed tomography, and magnetic resonance imaging.

As the transition toward total digital image acquisition continues, radiology is transcending the current standard of two-dimensional (2-D) cross-sectional anatomic imaging to more complex models. Among these are three-dimensional (3-D) anatomic images, constructed either from a synthesis of traditional 2-D data sets, or directly from volumetrically acquired data. However, current trends are moving beyond mere anatomic imaging to include physiological data once mainly obtained via nuclear medicine. Recent magnetic resonance pulse sequences, in addition to Doppler and harmonic ultrasound methods, are providing insight into blood flow, oxygenation, and metabolite concentrations non-invasively. Through image registration techniques, these data (even from differing modalities) are being assembled into 2-D and 3-D "fusion" images that promise to revolutionize diagnosis. Furthermore, with improvements in miniaturization, reliability, speed, built-in intelligence, and ease of use, these new developments are finding their way into use by nonspecialists. For instance, a new hand-held ultrasound unit will likely become a common tool among emergency medical teams, military medical teams, and in NASA's manned space program. Portable computed tomography (CT) scanners are already being used in the operating room. The increasing sophistication of imaging instruments will bring about a complementary increase in ease of use for both scanning and data interpretation, bringing diagnostic imaging and therapeutic capabilities closer to the patient, rather than the converse.

Diagnostic Imaging↗

Magnetic Resonance Imaging of Gases: A Single-Point Ramped Imaging with T1 Enhancement (SPRITE) Study.

A pure phase-encoding MRI technique, single-point ramped imaging with T1 enhancement, SPRITE, is introduced for the purpose of gas phase imaging. The technique utilizes broadband RF pulses and stepped phase encode gradients to produce images, substantially free of artifacts, which are sensitive to the gas T1 and T&ast:2 relaxation times. Images may be acquired from gas phase species with transverse relaxation times substantially less than 1 ms. Methane gas images, 1H, were acquired in a phantom study. Sulfur hexafluoride, 19F, images were acquired from a gas-filled porous coral sample. High porosity regions of the coral are observed in both the MRI image and an X-ray image. Sensitivity and resolution effects due to signal modulation during the time-efficient acquisition are discussed. A method to increase the image sensitivity is discussed, and the predicted improvement is shown through 1D images of the methane gas phantom. Copyright 1999 Academic Press.

Journal Article↗

A visual query-by-example image database for chest CT images: potential role as a decision and educational support tool for radiologists.

Primary reading or further evaluation of diagnostic imaging examination often needs a comparison between the actual findings and the relevant prior images of the same patient or similar radiological data found in other patients. This support is of clinical importance and may have significant effects on physicians' examination reading efficiency, service-quality, and work satisfaction. We developed a visual query-by-example image database for storing and retrieving chest CT images by means of a visual browser Image Management Environment (IME) and tested its retrieval efficiency. The visual browser IME included four fundamental features (segmentation, indexing, quick load and recall, user-friendly interface) in an integrated graphical environment for a user-friendly image database management. The system was tested on a database of 2000 chest CT images, randomly chosen from the digital archives of our institutions. A sample of eight heterogeneous images were used as queries and, for each of them a team of three expert radiologists selected the most similar images from the database (a set of 15 images containing similar abnormalities in the same position of the query). The sensitivity and the positive predictive factor, both averaged over the 8 test queries and 15 answers, were respectively 0.975 and 0.91 The IME system is currently under evaluation at our institutions as an experimental application. We consider it a useful work-in-progress tool for clinical practice facilitating searches for a variety of radiological tasks.

Database Management Systems↗

Tomographic myocardial perfusion imaging with technetium-99m teboroxime during adenosine-induced coronary hyperemia: correlation with thallium-201 imaging.

Single-photon emission computed tomographic imaging with technetium-99m teboroxime during exercise has been found to be feasible and the results correlate with those obtained with thallium-201. This study examined the feasibility of this technique and compared tomographic imaging with technetium-99m teboroxime during adenosine-induced coronary hyperemia with thallium-201 imaging. With the patient positioned on the imaging table, adenosine was infused at a rate of 140 micrograms/kg per min for 6 min. At 4 min, 20 to 25 mCi (740 to 925 MBq) of technetium-99m teboroxime was injected intravenously and imaging was started as soon as the infusion was completed with use of a 180 degrees anterior arc and 32 stops at 10 s/stop (total imaging time 7.8 min). Rest images were obtained 60 to 90 min later with use of a similar dose of technetium-99m teboroxime. Exercise tomographic thallium images were obtained within 2 weeks of the teboroxime studies. In the 20 patients studied, the teboroxime images were normal in 2 (50%) of 4 normal subjects and abnormal in 15 (94%) of 16 patients with coronary artery disease; 4 of the 15 had a fixed defect and 11 a reversible defect. There was agreement between teboroxime and thallium studies in 16 patients (80%), in 319 (80%) of 400 segments and in 50 (83%) of 60 vascular segments (p less than 0.05). In two normal subjects, an apparent fixed defect involving the inferior wall was seen on the teboroxime but not the thallium images and was thought to be due to an attenuation artifact secondary to extracardiac activity in the left lobe of the liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗

The generation and maintenance of visual mental images: evidence from image type and aging.

Imagery is a multi-componential process involving different mental operations. This paper addresses whether separate processes underlie the generation, maintenance and transformation of mental images or whether these cognitive processes rely on the same mental functions. We also examine the influence of age on these mental operations for independence of components. In Experiment 1, younger (22 years) and older (69 years) adults generated and maintained general, specific, contextual and autobiographical visual mental images evoked in response to concrete nouns. The older adults had longer generation times, but there was no difference between the two groups on maintenance. Both groups had shortest generation and maintenance times for general images, whereas only the older adults took longest in generating autobiographical images. In Experiment 2, the total maintenance time and number of transformations for each type of image were compared in another group of younger and older adults. General images were less transformed and more subject to decay for both groups. The older people maintained the autobiographical mental images for longest compared to other image types. In conclusion, image generation, maintenance and transformation seem to be differently affected by type of image and aging, supporting a model of their cognitive segregation.

Adult↗

The clinical impact of a combined gamma camera/CT imaging system on somatostatin receptor imaging of neuroendocrine tumours.

AIM: With a combined gamma camera/CT imaging system, CT images are obtained which are inherently registered to the emission images and can be used for the attenuation correction of SPECT and for mapping the functional information from these nuclear medicine tomograms onto anatomy. The aim of this study was to evaluate the clinical impact of SPECT/CT using such a system for somatostatin receptor imaging (SRI) of neuroendocrine tumours. MATERIALS AND METHODS: SPECT/CT imaging with (111)In-Pentetreotide was performed on 29 consecutive patients, the majority of whom had carcinoid disease. All SPECT images were first reported in isolation and then re-reported with the addition of the CT images for functional anatomical mapping (FAM). RESULTS: Fifteen of the 29 SPECT images were reported as abnormal, and in 11 of these abnormal images (73%) FAM was found to either establish a previously unknown location (7/11) or change the location (4/11) of at least one lesion. The revised location could be independently confirmed in 64% of these cases. Confirmation of location was not possible in the other patients due to either a lack of other relevant investigations, or the fact that lesions seen in the SPECT images were not apparent in the other investigations. FAM affected patient management in 64% of the cases where the additional anatomical information caused a change in the reported location of lesions. CONCLUSION: These results imply that FAM can improve the reporting accuracy for SPECT SRI with significant impact on patient management.

Adult↗

How does signal fade on photo-stimulable storage phosphor imaging plates when scanned with a delay and what is the effect on image quality?

OBJECTIVE: The goals of this in vitro study were to determine the effect of signal fading of DenOptix photo-stimulable storage phosphor imaging plates scanned with a delay and to determine the effect on the diagnostic quality of the image. In addition, we sought to correlate signal fading with image spatial resolution and average pixel intensity values. STUDY DESIGN: Forty-eight images were obtained of a test specimen apparatus and scanned at 6 delayed time intervals: immediately scanned, 1 hour, 8 hours, 24 hours, 72 hours, and 168 hours. Six general dentists using Vixwin2000 software performed a measuring task to determine the location of an endodontic file tip and root apex. One-way ANOVA with repeated measures was used to determine the effect of signal fading (delayed scan time) on diagnostic image quality and average pixel intensity value. RESULTS: There was no statistically significant difference in diagnostic image quality resulting from signal fading. No difference was observed in spatial resolution of the images. There was a statistically significant difference in the pixel intensity analysis of an 8-step aluminum wedge between immediate scanning and 24-hour delayed scan time. CONCLUSION: There was an effect of delayed scanning on the average pixel intensity value. However, there was no effect on image quality and raters' ability to perform a clinical identification task. Proprietary software of the DenOptix digital imaging system demonstrates an excellent ability to process a delayed scan time signal and create an image of diagnostic quality.

Analysis of Variance↗

IMAGE-WARP: a real-space restoration method for high-resolution STEM images using quantitative HRTEM analysis.

We have developed a new method for processing distorted high-resolution scanning transmission electron microscopy (STEM) images. The method is based on finding the displaced vertices in the experimental STEM image and warping to geometrically correct reference grid of the object. As a reference grid for warping a structural model obtained using a high-resolution transmission electron microscopy (HRTEM) analysis of the area of interest is utilised. Combined with quantitative HRTEM analysis the IMAGE-WARP method provides a real-space restoration of high-resolution high-angle annular dark-field (HAADF) STEM images without affecting the original Z-contrast information. The method can be applied to extract valuable compositional atomic-column data from any HAADF-STEM image of any kind of bulk crystals with local occupancy or chemistry fluctuations, stacking faults, special grain boundaries or interfaces, for which we have an available structural model. After the warping, distortion-corrected images can be further enhanced using conventional image-filtering techniques, and finally quantified with HAADF-STEM image simulations. The applicability of the IMAGE-WARP method was illustrated using experimental HAADF-STEM images of a strontium titanate crystal disrupted with a Ruddlesden-Popper-type antiphase boundary.

Journal Article↗

Fixations in natural scenes: interaction of image structure and image content.

Explorative eye movements specifically target some parts of a scene while ignoring others. Here, we investigate how local image structure--defined by spatial frequency contrast--and informative image content--defined by higher order image statistics-are weighted for the selection of fixation points. We measured eye movements of macaque monkeys freely viewing a set of natural and manipulated images outside a particular task. To probe the effect of scene content, we locally introduced patches of pink noise into natural images, and to probe the interaction with image structure, we altered the contrast of the noise. We found that fixations specifically targeted the natural image parts and spared the uninformative noise patches. However, both increasing and decreasing the contrast of the noise attracted more fixations, and, in the extreme cases, compensated the effect of missing content. Introducing patches from another natural image led to similar results. In all paradigms tested, the interaction between scene structure and informative scene content was the same in any of the first six fixations on an image, demonstrating that the weighting of these factors is constant during viewing of an image. These results question theories, which suggest that initial fixations are driven by stimulus structure whereas later fixations are determined by informative scene content.

Animals↗

An investigation of hemisphere differences for moderately imageable words across high and low image contexts.

The RVF/LH advantage typically found for high image nouns may be reduced or eliminated when they are mixed with other types of words, such as low image nouns ([Chiarello et al., 2001]). Global stimulus context thus appears to affect the distribution of processing across the hemispheres ( [Chiarello et al., 2001]). This idea was further investigated in the present study by presenting moderately imageable words (e.g., HOBBY) intermixed with either low or high image nouns. It was predicted that these medium image words would show a RVF advantage when mixed with high image nouns. However, this RVF advantage was expected to disappear when they were mixed with low image nouns, because the medium image words would be relatively more imageable in that context. This hypothesis was not supported, as similar RVF advantages were found for each imageability condition. It is suggested that more heterogenous stimulus distributions may be necessary for context-dependent alterations of cerebral asymmetries to occur.

Brain↗

Image Fusion System Using PACS for MRI, CT, and PET Images.

This paper presents and evaluates Picture Archiving and Communication System (PACS) and its interaction with the image fusion applications using positron emission tomography (PET), CT, and MRI, as well as some clinical applications of fusion images. A network connections between medium-sized PACS involving CT, MRI, SPECT, and PET were developed. Image registration and fusion was achieved in the PET's workstation by Advanced Visual System (AVS) software. Reconstructed datasets of CT, MRI, SPECT, and PET were transferred and archived in PACS servers. Series of anatomical images of CT and MRI were fused with metabolical images of PET with (18)F labeled fluoro-2-deoxy-D-glucose (FDG). Throughput rate of image data, as well as clinical applications of fusion images were evaluated and correlated with phantom studies. The average throughput rate of archiving and processing steps was 0.45 Mbps, 0.77 Mbps, respectively. Image fusion experiment using phantom and patients' data showed high accuracy in all directions. The combination of PACS and image fusion provided very useful clinical tools and made it quite easy to maximize the benefit from the diagnostic imaging.

Journal Article↗

Optimal strategies for imaging thick biological specimens: exit wavefront reconstruction and energy-filtered imaging.

In transmission electron microscopy (TEM) of thick biological specimens, the relationship between the recorded image intensities and the projected specimen mass density is distorted by incoherent electron-specimen interactions and aberrations of the objective lens. It is highly desirable to develop a strategy for maximizing and extracting the coherent image component, thereby allowing the projected specimen mass density to be directly related to image intensities. For this purpose, we previously used exit wavefront reconstruction to understand the nature of image formation for thick biological specimens in conventional TEM. Because electron energy-loss filtered imaging allows the contributions of inelastically scattered electrons to be removed, it is potentially advantageous for imaging thick, biological samples. In this paper, exit wavefront reconstruction is used to quantitatively analyse the imaging properties of an energy-filtered microscope and to assess its utility for thick-section microscopy. We found that for imaging thick biological specimens (> 0.5 microns) at 200 keV, only elastically scattered electrons contribute to the coherent image component. Surprisingly little coherent transfer was seen when using energy-filtering at the most probable energy loss (in this case at the first plasmon energy-loss peak). Furthermore, the use of zero-loss filtering in combination with exit wavefront reconstruction is considerably more effective at removing the effects of multiple elastic and inelastic scattering and microscope objective lens aberrations than either technique by itself. Optimization of the zero-loss signal requires operation at intermediate to high primary voltages (> 200 keV). These results have important implications for the accurate recording of images of thick biological specimens as, for instance, in electron microscope tomography.

Animals↗

Photoscreening for diabetic retinopathy: a comparison of image quality between film photography and digital imaging.

PURPOSE: Retinal images from patients attending an urban screening centre before and after the transition from film photography to digital image acquisition were analysed for quality of image. METHODS: A total of 1946 diabetic patients, aged 12-92 years (mean 55.6 +/- 14.88 years), were included in this retrospective study of retinal screening techniques. Each imaging group was subdivided into age-matched groups. In all subjects pupils were pharmacologically dilated before photography. The images were reviewed by the same three experienced observers and graded at the time of screening from grade 1 (excellent quality) to grade 4 (unreadable). RESULTS: Of 938 patients in the film group, 31.3% had excellent images, 38.2% good, 22.7% poor and 7.8% were unreadable. Of the 1008 patients in the digital imaging group, 25.3% had excellent images, 46.3% good, 14.6% poor and 13.8% were unreadable. A significant difference was observed in patients over 65 years of age who exhibited a threefold increase in failure rate with digital imaging (33.7% v 11.3%)(P < 0.0001). CONCLUSION: In this study population a statistically significant degradation of image quality was observed in those older than 65 years following transition to digital photography. This has implications for service provision planning.

Adolescent↗

Thyroid imaging using positron emission tomography--a comparison with ultrasound imaging and conventional scintigraphy in thyrotoxicosis.

Forty-six comparative studies were performed on 41 patients with hyperthyroidism. Clinically these comprised two groups: those with Graves' disease, and those with multinodular goitre. All patients underwent an ultrasound examination and positron emission tomography (PET) using 124I, then gamma camera pinhole imaging following their 131I therapy administration. Although the 131I pinhole imaging was not performed for diagnostic purposes, there was good correlation (78% agreement) between it and 124I PET in determining relative lobe size. Hence either imaging modality could be used as an indicator of the relative radiation dose delivered to each thyroid lobe at a macroscopic level. In terms of gland morphology the PET images corresponded well to the high resolution ultrasound images (78% agreement), unlike the pinhole images which correlated poorly (only 28% agreement). The results showed that PET imaging gives better anatomical and physiological detail than 131I pinhole imaging. In 77% of cases where the pinhole image showed a uniform distribution of radioisotope, the improved spatial resolution of the PET images revealed non-homogeneous distribution indicating a non-uniform distribution of radiation dose. Since all dosimetry calculations are based on the assumption of uniform distribution of radioiodine, this non-uniformity could possibly have important consequences in the outcome of radioiodine therapy in thyrotoxicosis.

Adult↗