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At least 55 records · Page 3Linked to original sources
PubMed2003

Contrast burst depletion imaging (CODIM): a new imaging procedure and analysis method for semiquantitative ultrasonic perfusion imaging.

BACKGROUND AND PURPOSE: Established methods of ultrasonic perfusion imaging using a bolus application of echo contrast agent provide only qualitative data because of various physical phenomena. This study was intended to investigate whether a new ultrasound perfusion imaging method termed contrast burst depletion imaging (CODIM) may provide semiquantitative measures of parenchymal perfusion independent of examination depth and acoustic energy distribution. METHODS: In a system with a constant concentration of contrast agent, analyzing the decrease in image intensity that occurs with microbubble-destructive imaging modes yields parameters that are considered to correlate with tissue perfusion. This method was first evaluated with a perfusion model that showed that the main resulting parameter "perfusion coefficient" (PC) is a monotonic nonlinear function of flow velocity. Seventeen human volunteers were then scanned according to this method with the use of 2 different contrast agents. Results were correlated with those from perfusion-weighted MRI examinations. RESULTS: The PC did not show significant differences in gray matter areas (ranging from 1.466x10(-2) x s(-1) to 1.641x10(-2) x s(-1)) of the brain despite different insonation depths (eg, ipsilateral and contralateral thalamus). In contrast, white matter exhibited significantly lower perfusion values in both imaging modes (PC: 0.604x10(-2) x s(-1) to 0.745x10(-2) x s(-1); P<0.05). CONCLUSIONS: CODIM is a promising new tool of imaging parenchymal (brain) perfusion in healthy persons. The method provides semiquantitative and depth-independent perfusion parameters and in this way overcomes the limitations of the perfusion methods using a bolus kinetic. Further investigations must be done to evaluate the potential of the method in patients with perfusion deficits.

Adult↗
PubMed2005

Dynamic flat panel detector versus image intensifier in cardiac imaging: dose and image quality.

The practical aspects of the dosimetric and imaging performance of a digital x-ray system for cardiology procedures were evaluated. The system was configured with an image intensifier (II) and later upgraded to a dynamic flat panel detector (FD). Entrance surface air kerma (ESAK) to phantoms of 16, 20, 24 and 28 cm of polymethyl methacrylate (PMMA) and the image quality of a test object were measured. Images were evaluated directly on the monitor and with numerical methods (noise and signal-to-noise ratio). Information contained in the DICOM header for dosimetry audit purposes was also tested. ESAK values per frame (or kerma rate) for the most commonly used cine and fluoroscopy modes for different PMMA thicknesses and for field sizes of 17 and 23 cm for II, and 20 and 25 cm for FD, produced similar results in the evaluated system with both technologies, ranging between 19 and 589 microGy/frame (cine) and 5 and 95 mGy min(-1) (fluoroscopy). Image quality for these dose settings was better for the FD version. The 'study dosimetric report' is comprehensive, and its numerical content is sufficiently accurate. There is potential in the future to set those systems with dynamic FD to lower doses than are possible in the current II versions, especially for digital cine runs, or to benefit from improved image quality.

Air↗
PubMed2006

Comparison of daily megavoltage electronic portal imaging or kilovoltage imaging with marker seeds to ultrasound imaging or skin marks for prostate localization and treatment positioning in patients with prostate cancer.

PURPOSE: To compare the accuracy of imaging modalities, immobilization, localization, and positioning techniques in patients with prostate cancer. METHODS AND MATERIALS: Thirty-five patients with prostate cancer had gold marker seeds implanted transrectally and were treated with fractionated radiotherapy. Twenty of the 35 patients had limited immobilization; the remaining had a vacuum-based immobilization. Patient positioning consisted of alignment with lasers to skin marks, ultrasound or kilovoltage X-ray imaging, optical guidance using infrared reflectors, and megavoltage electronic portal imaging (EPI). The variance of each positioning technique was compared to the patient position determined from the pretreatment EPI. RESULTS: With limited immobilization, the average difference between the skin marks' laser position and EPI pretreatment position is 9.1 +/- 5.3 mm, the average difference between the skin marks' infrared position and EPI pretreatment position is 11.8 +/- 7.2 mm, the average difference between the ultrasound position and EPI pretreatment position is 7.0 +/- 4.6 mm, the average difference between kV imaging and EPI pretreatment position is 3.5 +/- 3.1 mm, and the average intrafraction movement during treatment is 3.4 +/- 2.7 mm. For the patients with the vacuum-style immobilization, the average difference between the skin marks' laser position and EPI pretreatment position is 10.7 +/- 4.6 mm, the average difference between kV imaging and EPI pretreatment position is 1.9 +/- 1.5 mm, and the average intrafraction movement during treatment is 2.1 +/- 1.5 mm. CONCLUSIONS: Compared with use of skin marks, ultrasound imaging for positioning provides an increased degree of agreement to EPI-based positioning, though not as favorable as kV imaging fiducial seeds. Intrafraction movement during treatment decreases with improved immobilization.

Gold↗
PubMed1997

Should imaging at stress always be followed by imaging at rest in Tc-99m MIBI SPECT? A proposal for a selective referral and imaging strategy.

OBJECTIVES: We addressed the question whether in patients with cardiac chest pain referred for stress myocardial perfusion scintigraphy, Tc-99m MIBI SPECT stress imaging should always be followed by a rest imaging procedure. BACKGROUND: Using Tc-99m MIBI imaging a stress rest sequence is usually performed implying that the resting study always follows the stress study irrespective of the results of the stress study. As a normal stress study would eliminate a subsequent resting study, it appears desirable to potentially define certain subsets of patients in whom a normal stress study can be expected in order to determine a more selective referral approach to the nuclear medicine department. The consequences of such a more streamlined approach would less impose on the logistics of the department of nuclear medicine, with decrease of investigation time, radiation dose, and costs in a time of retrenchment in the medical sector. METHODS: A consecutive series of 460 patients (mean age 58.2 years) was studied who were stratified to 269 patients without prior myocardial infarction, and to 191 patients with documented evidence of a previously sustained myocardial infarction. All patients underwent Tc-99m MIBI SPECT imaging according to a two-day stress-rest protocol. RESULTS: Patients with and without a previous myocardial infarction showed suboptimal overall predictive accuracies for the exercise electrocardiograms (58% and 60%, respectively). In the total group of 460 patients, 94 (20%) patients showed a normal stress-rest Tc-99m MIBI SPECT; this occurred in 86/269 (32%) patients without a previous myocardial infarction and in only 8/191 (4%) patients with a previous myocardial infarction. CONCLUSIONS: Patients with a stress defect at Tc-99m MIBI SPECT imaging should always undergo a resting SPECT study irrespective of the clinical and stress electrocardiographic findings. As patients without a previous myocardial infarction had a normal stress SPECT study in almost one-third (32%) of patients compared to only 4% in patients with a previously myocardial infarction, it may be useful to employ different referral and imaging strategies i.e., a stress-only versus a stress-rest procedure. To schedule referring patients differently according to the presence or absence of a previously sustained myocardial infarction may be cost-saving, less demanding for the nuclear medicine personnel, and patient-convenient. In addition, a stress-only imaging procedure reduces radiation exposure to the individual patient.

Adult↗
PubMed2002

[Image quality and detection of pathology by ultrasound: comparison of B-mode ultrasound with photopic imaging and tissue harmonic imaging alone and in combination].

PURPOSE: To determine the accuracy of photopic imaging (PI) in detecting pathology by ultrasound (US) and to assess the image quality in direct comparison with conventional B-mode ultrasound and tissue harmonic imaging (THI). MATERIAL AND METHODS: Fifty-two patients underwent US examination, among them 29 patients for abdominal assessment and 23 for otolaryngological assessment. A total of 208 freeze frames, 52 B-mode scans each with and without THI and 52 B-mode scans each with and without PI, were assessed by three readers, who determined the presence of pathology on a scale of 1 (definitely abnormal) to 5 (definitely normal). All 52 patients underwent US follow-up within six weeks. The results were confirmed by CT in 30 patients and by histology in five cases. Image quality and different color encodings of each technique were rated on a ranking scale of 1 (optimal) to 4 (poor). The different US techniques were compared in terms of image quality, diagnostic accuracy, and color encoding using McNemar's test and ROC analysis. RESULTS: The results for image quality were as follows: B-scan 3.9; THI 1.9; PI 2.8; and THI plus PI 1.5 (each p < 0.05). The following AUCs (Area under Curve, presence of pathology) were calculated: 0.925, 0.990, and 0.990 for B-mode US, THI, and PI, respectively (not significant), and 0.994 for THI plus PI (significant compared to B-mode scan). The different color encodings were rated as follows: reddish brown 1.6, gray 1.9, blue 3.1, and green 3.6 (each p < 0.05). CONCLUSION: For ultrasound examinations, PI in combination with THI improves the image quality and conspicuity of pathology.

Abdomen↗
PubMed1997

Computer analysis of mammography phantom images (CAMPI): an application to the measurement of microcalcification image quality of directly acquired digital images.

The purpose of this investigation was to apply the recently developed CAMPI (computer analysis of mammography phantom images) method to a Fischer Mammotest Stereotactic Digital Biopsy machine. Another aim was to further elucidate the nature of the empirically introduced CAMPI measures. Images of an American College of Radiology (ACR) accreditation phantom centered on the largest two speck groups were obtained on this machine under a variety of x-ray conditions. An additional measure, alternative SNR (ASNR) is introduced which is complementary to the SNR measure. Analyses of the Mammotest images revealed that the mAs and kVp dependencies of the CAMPI measures could be understood from basic imaging physics principles. It is shown that: (1) the measures reflect the expected linearity of the digital detector and Poisson photon statistics; (2) under automatic exposure control (AEC) conditions the signal (SIG) measure is proportional to subject contrast; and (3) under AEC conditions the noise (NOI) measure is proportional to the square root of the average absorbed photon energy. Correspondence with basic imaging physics principles shows that the measures are significantly free of artifacts. Precision of the CAMPI measures exceeds that of human observers by orders of magnitude. CAMPI measures are expected to be more relevant to clinical mammography than Fourier metrics as the measurements are done on objects of arbitrary shape and size that were designed by the manufacturer to resemble various detection tasks in mammography. It is concluded that CAMPI can perform objective and highly precise evaluations of phantom image quality in mammography. It could be used as a sophisticated quality control tool, as a replacement for the current ACR/MQSA phantom evaluation program, and to evaluate the rapidly evolving digital mammography technology.

Biophysical Phenomena↗
PubMed2006

11C-acetate positron emission tomography imaging and image fusion with computed tomography and magnetic resonance imaging in patients with recurrent prostate cancer.

PURPOSE: To assess the clinical value of computed tomography (CT) and magnetic resonance imaging (MRI) image fusion with 11C-acetate (AC) positron emission tomography (PET) imaging for detection and exact location of clinically occult recurrences. PATIENTS AND METHODS: Fifty prostate cancer patients with elevated/increasing serum prostate-specific antigen levels after radical therapy underwent whole-body AC PET. Uptake was initially interpreted as normal, abnormal, or equivocal. In case of abnormal or equivocal uptake, additional conventional imaging techniques, such as CT, MRI, and bone scans, were performed. To precisely define the anatomic location of abnormal uptake and to improve characterization of equivocal lesions, a software-assisted image fusion (CT-PET, MRI-PET) was performed and evaluated as site-by-site analysis of 51 abnormal (n = 37) or equivocal (n = 14) sites of all 50 patients. In 17 patients, additional histopathologic evaluation was available. RESULTS: In five (10%), 13 (26%), and 32 (64%) of the 50 patients, AC PET studies demonstrated AC uptake judged as normal, equivocal, and abnormal, respectively. Image fusion changed characterization of equivocal lesions as normal in five (10%) of 51 sites and abnormal in nine (18%) of 51 sites. It precisely defined the anatomic location of abnormal uptake in 37 (73%) of 51 sites. AC PET findings did influence patient management in 14 (28%) of 50 patients. CONCLUSION: Retrospective fusion of AC PET and CT/MRI is feasible and seems to be essential for final diagnosis. This is particularly true in patients with AC uptake in the prostate region.

Acetates↗
PubMed1999

Radiological diagnosis of acute stroke. Comparison of conventional MR imaging, echo-planar diffusion-weighted imaging, and spin-echo diffusion-weighted imaging.

PURPOSE: To compare conventional MR imaging, echo-planar diffusion-weighted imaging (EP-DWI) and spin-echo diffusion-weighted imaging (SE)-DWI at radiological diagnosis of acute stroke. MATERIAL AND METHODS: Twenty-seven patients (30-85 years old) were examined. Clinical examination was performed before MR imaging. All MR examinations were assessed by an experienced neuroradiologist blinded to clinical findings. RESULTS: In EP-DWI, every patient had a lesion corresponding to the clinical findings. EP-DWI was used as the gold standard. In conventional PD+T2 imaging, 23/59 focal lesions were interpreted as acute, which was false in 11 lesions, and 36/59 lesions were considered to be old, 6 were in fact acute. Nine acute lesions were only detected retrospectively and 12 acute lesions were not detected at all on PD+T2. SE-DWI including the apparent diffusion coefficient correlated fairly well with EP-DWI but the procedure was impractical. CONCLUSION: EP-DWI is reliable for diagnosis of early ischemic stroke, while SE-DWI performs reasonably well. Conventional PD+T2 imaging is not reliable for diagnosis of early ischemia.

Acute Disease↗
PubMedDate not supplied

Ultrafast MR imaging of the abdomen: echo planar imaging and diffusion-weighted imaging.

Ultrafast MRI technique has become available with the introduction of new generation MR scanners for abdominal imaging. However, there is no consensus about the optimal imaging acquisition at the present time. Because single shot echo planar imaging (EPI) technique is based on high technology and had just applied in clinical imaging, further clinical investigation will be needed. Currently, the hypersensitivity to magnetic inhomogeneity and local magnetic susceptibility and the low spatial resolution may limit the widespread application of EPI technique. In addition to providing information for morphologic diagnosis, EPI will be more widely used for functional and qualitative diagnosis. Diffusion-weighted imaging can be used for differentiation of solid tumors according to their different cellular construction, evaluation of cystic lesions based on the different viscosity of their contents, and assessment of diffused pathologic changes in the parenchyma of solid organs. In addition to the previous parameters such as proton density and T1 and T2 values, diffusion factors may provide important information for the qualitative and dynamic evaluation of abdominal pathologic changes. Even though there are many difficulties that must be solved for diffusion-weighted imaging, a more wide application of this technique is expected through technologic improvement.

Abdomen↗
PubMed1992

Near-infrared imaging in vivo (I): Image restoration technique applicable to the NIR projection images.

To enhance spatial resolution of NIR projection images in vivo, we performed refocusing of NIR projection images of human forearm of about 50 mm thickness. A volunteer's forearm was illuminated by parallel light beam-flux, and then projection images at 750 nm was measured with a Pertier-cooled CCD video camera and digitized. For refocusing computation, PSF of the light transmitted through the tissue was calculated by general equation proposed by van der Zee and Delpy (1988). Simple inverse, constrained least squares, and Wiener filters were tested as refocusing algorithms. Wiener filter gave the best result in terms of image quality and computation time. By applying Wiener filter to the image refocusing of NIR projection images of human forearm, we obtained enhanced spatial resolution.

Evaluation Studies as Topic↗
PubMed2003

Multi-wavelength raman imaging using a small-diameter image guide with a dimension-reduction imaging array.

A commercially available fiber-optic Raman probe was modified for high-resolution spectral Raman imaging using a 350 microm diameter optical fiber image guide coupled to a dimension-reduction imaging array (DRIA). The DRIA comprised 672 optical fibers, arranged as a square array (21 x 32 fibers) on one end and a linear array (672 x 1 fibers) on the other. An imaging spectrograph was used with the DRIA to acquire multi-wavelength Raman images from -250 to 1800 cm(-1) at a spectral resolution of approximately 5 cm(-1). The utility of this technique for in situ and remote Raman imaging is demonstrated by monitoring the polymerization of a model polymer, dibromostyrene (DBS), while simultaneously measuring the Raman Stokes/ anti-Stokes ratio as a function of sample heating time, over a sample area of approximately 4 x 1.6 mm.

Fiber Optic Technology↗
PubMed1991

MR imaging of the portal venous system: value of gradient-echo imaging as an adjunct to spin-echo imaging.

We evaluated the use of gradient-echo (GRE) as an adjunct to spin-echo (SE) MR imaging of the portal venous system. GRE imaging was performed in 31 subjects, 15 normal volunteers and 16 patients with documented portal venous disease (15 cases) or suspected disease (one case). Eight of 16 patients had venous thrombosis, five had focal thrombus, and three had complete occlusion. Six patients had extrinsic venous compression by tumor. Of the two other patients, one had an arteriovenous fistula and the other a falsely positive angiogram, suggesting portal vein occlusion. In normal subjects, GRE scans had excellent visualization of the portal venous system with high intravascular signal compared with surrounding tissues. Nine (60%) of 15 normal subjects and three patients had an artifact consisting of a curvilinear area of decreased signal that could mimic clot. In three of five patients with focal thrombus, clot was identified on GRE but not on SE images. In all three patients with occlusion, SE and GRE images demonstrated similar findings. In five of the six patients with extrinsic venous compression by tumor, SE and GRE studies showed similar findings. Of the two patients, an arteriovenous fistula was seen on GRE MR in one, and in the other, patency of the left portal vein was seen on SE and GRE images after angiography had suggested portal vein occlusion. Collateral vessels were seen in nine of 16 patients. In five of nine cases, GRE MR demonstrated more extensive collaterals than did SE MR. In summary, GRE MR provides a useful adjunct to standard SE MR imaging. Benefits include high contrast between vascular structures and surrounding tissues, reduced motion artifact, and rapid scanning within a breath-hold.

Adolescent↗
PubMed2003

Accelerated dynamic MR imaging with a parallel imaging technique for hypervascular hepatocellular carcinomas: usefulness of a test bolus in examination and subtraction imaging.

PURPOSE: To assess the impact of the accelerated dynamic MR imaging (ADMRI) approach using parallel imaging for detecting hypervascular hepatocellular carcinomas (HCCs) and to evaluate the usefulness of a test bolus in examination and subtraction imaging in this setting. MATERIALS AND METHODS: Thirty patients with 135 HCCs underwent ADMRI using a two-dimensional gradient-recalled echo sequence with parallel imaging. Seventeen patients were evaluated without a test bolus and 13 patients with a test bolus. The detectability of HCCs was calculated between the groups with and without a test bolus. ADMRI was evaluated regarding the signal-to-noise ratio (SNR) of the lesion and the liver, the contrast-to-noise ratio (CNR) of the lesion vs. the liver, and the feasibility of subtraction images. RESULTS: ADMRI with and without a test bolus had almost equal sensitivity (92.5% and 92.6%). No significant difference was seen in the SNR of lesions and the CNR of lesions vs. livers between both groups. With a test bolus, ADMRI could depict the peak enhancement of nodules on the 2nd or 3rd dynamic phases and optimized the timing of peak lesion enhancement. Subtraction images could be obtained regarding minimal slice misregistration. CONCLUSION: ADMRI had high detectability of HCCs with and without a test bolus.

Adult↗
PubMed1983

A distribution system for digital images from diverse image sources. Incorporating a local area network in an imaging environment.

This paper proposes a unified image-processing and viewing system as a viewing station and initially as the central file server in a unified digital image distribution and processing network, linking various digital image sources through a high speed data link and a common image format. The network allows for viewing and processing of all images produced within the complex and for locating viewing stations in any number of convenient areas. The system proposed can be slowly expanded to include all the digital images produced within the department of institution.

Computers↗
PubMed2000

Image analysis methods for assessing levels of image plane nonuniformity and stochastic noise in a magnetic resonance image of a homogeneous phantom.

Magnetic response image plane nonuniformity and stochastic noise are properties that greatly influence the outcome of quantitative magnetic resonance imaging (MRI) evaluations such as gel dosimetry measurements using MRI. To study these properties, robust and accurate image analysis methods are required. New nonuniformity level assessment methods were designed, since previous methods were found to be insufficiently robust and accurate. The new and previously reported nonuniformity level assessment methods were analyzed with respect to, for example, insensitivity to stochastic noise; and previously reported stochastic noise level assessment methods with respect to insensitivity to nonuniformity. Using the same image data, different methods were found to assess significantly different levels of nonuniformity. Nonuniformity levels obtained using methods that count pixels in an intensity interval, and obtained using methods that use only intensity values, were found not to be comparable. The latter were found preferable, since they assess the quantity intrinsically sought. A new method which calculates a deviation image, with every pixel representing the deviation from a reference intensity, was least sensitive to stochastic noise. Furthermore, unlike any other analyzed method, it includes all intensity variations across the phantom area and allows for studies of nonuniformity shapes. This new method was designed for accurate studies of nonuniformities in gel dosimetry measurements, but could also be used with benefit in quality assurance and acceptance testing of MRI, scintillation camera, and computer tomography systems. The stochastic noise level was found to be greatly method dependent. Two methods were found to be insensitive to nonuniformity and also simple to use in practice. One method assesses the stochastic noise level as the average of the levels at five different positions within the phantom area, and the other assesses the stochastic noise in a region outside the phantom area.

Image Processing, Computer-Assisted↗
PubMedDate not supplied

Periodically rotated overlapping parallel lines with enhanced reconstruction-based diffusion tensor imaging. Comparison with echo planar imaging-based diffusion tensor imaging.

OBJECTIVE: To evaluate diffusion tensor imaging (DTI) based on periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) compared with DTI based on single-shot echo planar imaging (EPI). METHODS: Diffusion tensor data were acquired with PROPELLER (PROPELLER-DTI, 3 NEX), EPI (EPI-DTI2, 16 NEX) with the same acquisition time (11.4 minutes) and with EPI (EPI-DTI1, number of excitations = 4) with a shorter acquisition time (2.8 minutes). Regions of interest were set in the genu and splenium of the corpus callosum, as determined on T2-weighted fast spin echo images and fractional anisotropy (FA) maps, separately. Two neuroradiologists visually evaluated image distortion and quality in the supra- and infratentorial structures. RESULTS: In the genu, standard deviation determined by respective FA maps was decreased in order of PROPELLER-DTI, EPI-DTI1, and EPI-DTI2. Both EPI-DTI sequences were quantitatively superior in the splenium, but PROPELLER-DTI was less distorted. CONCLUSION: Periodically rotated overlapping parallel lines with enhanced reconstruction-DTI could become a complementary tool when qualitatively evaluating seriously distorted structures.

Adult↗
PubMed2002

Combined magnetic resonance imaging and spectroscopic imaging approach to molecular imaging of prostate cancer.

Magnetic resonance spectroscopic imaging (MRSI) provides a noninvasive method of detecting small molecular markers (historically the metabolites choline and citrate) within the cytosol and extracellular spaces of the prostate, and is performed in conjunction with high-resolution anatomic imaging. Recent studies in pre-prostatectomy patients have indicated that the metabolic information provided by MRSI combined with the anatomical information provided by MRI can significantly improve the assessment of cancer location and extent within the prostate, extracapsular spread, and cancer aggressiveness. Additionally, pre- and post-therapy studies have demonstrated the potential of MRI/MRSI to provide a direct measure of the presence and spatial extent of prostate cancer after therapy, a measure of the time course of response, and information concerning the mechanism of therapeutic response. In addition to detecting metabolic biomarkers of disease behavior and therapeutic response, MRI/MRSI guidance can improve tissue selection for ex vivo analysis. High-resolution magic angle spinning ((1)H HR-MAS) spectroscopy provides a full chemical analysis of MRI/MRSI-targeted tissues prior to pathologic and immunohistochemical analyses of the same tissue. Preliminary (1)H HR-MAS spectroscopy studies have already identified unique spectral patterns for healthy glandular and stromal tissues and prostate cancer, determined the composition of the composite in vivo choline peak, and identified the polyamine spermine as a new metabolic marker of prostate cancer. The addition of imaging sequences that provide other functional information within the same exam (dynamic contrast uptake imaging and diffusion-weighted imaging) have also demonstrated the potential to further increase the accuracy of prostate cancer detection and characterization.

Humans↗