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PubMed1989

Diagnosis of breast calcifications: comparison of contact, magnified, and television-enhanced images.

Matched contact and microfocal-spot-magnified images of 31 breasts, each containing a cluster of microcalcifications within a biopsy-proved benign (n = 21) or malignant (n = 10) lesion, were evaluated. Each matched set consisted of one image magnified 1.5 or 2.0 times by a microfocal spot; one contact film-screen mammogram; and one television-digitized, enhanced, and optically magnified contact film-screen mammogram. Three experienced mammographers and three senior diagnostic radiology residents with 2 weeks of training in mammography interpreted the calcifications. The average area under the receiver-operating-characteristic curve for the experienced mammographers was 0.60 for contact radiographs, 0.61 for the television-digitized images, and 0.69 for the microfocal-spot-magnified radiographs. The less experienced senior residents scored below a random choice, 0.44, for the television-digitized images; 0.51 for contact radiographs; and 0.69 for the microfocal-spot-magnified radiographs. We conclude that when evaluating microcalcifications, radiologists without extensive experience in mammography should not substitute television-digitized and enhanced contact mammograms for microfocal-spot-magnified mammograms; rigorous clinical evaluation is needed before this system is accepted for clinical use.

Analysis of Variance↗
PubMedDate not supplied

Toward quantitative characterization of the caudate nucleus through CT image enhancement.

Dilated lateral cerebral ventricles have been reported in association with psychiatric disorders. The dilatation is likely secondary to changes in anatomically related centers in the brain. Our attention is focused on the caudate nucleus and the need to develop quantitative characterization of it in psychiatric research. A computer method is described for accurately detecting the edges of the caudate nuclei in CT scans. The method consists of a two-dimensional filtering step to reduce image noise, followed by gradient computation for edge enhancement, and then an edge detection step to identify and record the caudate nuclei cross sections. Results from both head scans and synthetic images indicate that the method is successful even for low-contrast edges where the standard deviation of image noise approaches the difference in mean HU across the edge. The availability of an automated method of delineating the caudate nucleus permits the cross-sectional area and shape to be determined, the density to be estimated, and, from a set of closely spaced slices, volume information to be obtained.

Caudate Nucleus↗
PubMed1994

Ultrasonic B-mode image enhancement based on level-dependent spread functions.

The concept of level-dependent spatial summation is applied to the 2-dimensional amplitude distribution comprising an ultrasonic brightness image. The distribution is convolved with a level-dependent kernel. The size (i.e., extent) of the kernel is inversely proportional to the local signal level. The result is a 2-dimensional distribution of Mach bands, accentuating edges and providing useful information for the reduction of speckle. In addition, a small but powerful extension of the processing scheme is presented that supports global edge enhancement and contrast enhancement. The level of improvement has been quantified in terms of an increase in the lesion signal-to-noise ratio on the order of 60 percent. Only two system-dependent parameters have to be supplied for adjustment. The algorithm is rather insensitive to the exact choice of the parameters, making it quite robust. Since only a limited number of simple operations is required for the processing of a frame, the algorithm is expected to be suitable for real time application.

Image Enhancement↗
PubMed1996

Enhanced image generation abilities in deaf signers: a right hemisphere effect.

Deaf subjects who use American Sign Language as their primary language generated visual mental images faster than hearing nonsigning subjects when stimuli were initially presented to the right hemisphere. Deaf subjects exhibited a strong right hemisphere advantage for image generation using either categorical or coordinate spatial relations representations. In contrast, hearing subjects showed evidence of left hemisphere processing for categorical spatial relations representations, and no hemispheric asymmetry for coordinate spatial relations representations. The enhanced right hemisphere image generation abilities observed in deaf singers may be linked to a stronger right hemisphere involvement in processing imageable signs and linguistically encoded spatial relations.

Adult↗
PubMed1994

[A study of green tea for a positive gastrointestinal MR imaging enhancing agent].

Green tea has been incidentally found to produce a high signal on T1-weighted MR images. This study was therefore designed to investigate what substance in the green tea produced this T1-shortening effect and whether a green tea solution could be used as a positive enhancing agent in MR studies. As a result of the chemical analysis and measurement of T1 relaxation times in various solutions originating from green tea, it was found that the T1-shortening effect was produced not only by free manganese, but also by a high molecular weight substance (molecular weight 1.2 x 10(4) or more) united with manganese. In clinical MR studies, the gastrointestinal tract was markedly enhanced after oral administration of a green tea solution. The pancreatic head was clearly delineated with visualization of both the gastric wall and descending portion of the duodenum. However, visualization of the jejunum and ileum was not improved, suggesting that the green tea solution was diluted by intestinal fluid in the small bowel. Since only a small amount of manganese (1500 ppm) united with a high molecular weight compound such as pectin was sufficient to produce excellent enhancement of the gastrointestinal tract, it would be better to develop a purely synthetic chemical compound, for example, one consisting of a polysaccharide and manganese, rather than to use a green tea solution as a gastrointestinal enhancing agent in MR studies.

Contrast Media↗
PubMed2001

Multi--detector row helical CT of the pancreas: effect of contrast-enhanced multiphasic imaging on enhancement of the pancreas, peripancreatic vasculature, and pancreatic adenocarcinoma.

PURPOSE: To determine the optimal phase for enhancement of the normal pancreas and peripancreatic vasculature and the maximal tumor-to-pancreatic parenchymal enhancement difference by using multiphase, contrast material-enhanced, multi-detector row helical computed tomography (CT). MATERIALS AND METHODS: Forty-nine patients with a normal-appearing pancreas but suspected of having pancreatic abnormality and 28 patients with proved pancreatic adenocarcinoma underwent multiphase, contrast-enhanced, multi-detector row CT during the arterial phase (AP), pancreatic parenchymal phase (PPP), and portal venous phase (PVP). Attenuation values of the normal pancreas, pancreatic adenocarcinoma, celiac and superior mesenteric arteries, and superior mesenteric and portal veins were measured during all three imaging phases. Quantitative analysis of these measurements and subjective qualitative analysis of tumor conspicuity were performed. RESULTS: Maximal enhancement of the normal pancreatic parenchyma occurred during the PPP. Maximal tumor-to-parenchyma attenuation differences during the PPP and PVP were equivalent but greater than that during the AP. Subjective analysis revealed that tumor conspicuity during the PPP and PVP was equivalent but superior to that during the AP. Maximal arterial enhancement was seen during the PPP, and maximal venous enhancement was seen during the PVP. CONCLUSION: A combination of PPP and PVP imaging is sufficient for detection of pancreatic adenocarcinoma, because it provides maximal pancreatic parenchymal and peripancreatic vascular enhancement. AP imaging can be reserved for patients in whom CT angiography is required.

Adenocarcinoma↗
PubMed1990

Rheumatoid arthritis: evaluation of hypervascular and fibrous pannus with dynamic MR imaging enhanced with Gd-DTPA.

The knees of 20 patients with rheumatoid arthritis and two healthy volunteers were evaluated with magnetic resonance (MR) imaging. Spin-echo sequences were performed, and the signal-intensity patterns of normal and pathologic articular soft-tissue structures were quantitatively evaluated with a dynamic FLASH (fast low-angle shot) sequence after bolus intravenous injection of gadolinium diethylenetriaminepentaacetic acid. In contrast to the spin-echo images obtained before injection of contrast material, it appears possible with this technique to distinguish joint effusion from hypervascular pannus formations and to grade the vascularity of proliferative synovitis. Flat pannus deposits on the articular surface and subchondral pannus masses were identified only by their marked enhancement of signal intensity after injection of contrast material. Dynamic MR imaging appears to yield decisive information for diagnosing rheumatoid arthritis.

Adult↗
PubMed2006

Multidetector CT in abdominal aortic aneurysm treated with endovascular repair: are unenhanced and delayed phase enhanced images effective for endoleak detection?

PURPOSE: To retrospectively determine the sensitivity and specificity of unenhanced, delayed enhanced phase (DEP), and arterial enhanced phase (AEP) multi-detector row computed tomography (CT) for depicting endoleaks during follow-up of endovascular aneurysm repair. MATERIALS AND METHODS: Fifty patients (two women, 48 men; mean age, 72 years) underwent follow-up multi-detector row CT 1, 6, and 12 months after endovascular aneurysm repair. Unenhanced CT was performed with 2.5-mm collimation; 1-mm collimation was used with AEP and DEP examinations. Two independent readers assessed the presence of endoleak in three reading sessions: AEP (session A), unenhanced and AEP (session B), and AEP and DEP (session C). At 6- and 12-month follow-up, a fourth set was included: 1-month unenhanced and AEP (session D). Sensitivity, specificity, and positive predictive value of each session were calculated. Triple-phase multi-detector row CT was the reference standard. RESULTS: At 1 month, sensitivity, specificity, and positive predictive value, respectively, were 79%, 75%, and 55% for session A; 93%, 97%, and 93% for session B; and 93%, 78%, and 62% for session C. At 6 months, sensitivity, specificity, and positive predictive value, respectively, were 92%, 68%, and 48% for session A; 92%, 100%, and 100% for session B; and 100%, 84%, and 67% for session C. At 12 months, sensitivity, specificity, and positive predictive value, respectively, were 80%, 80%, and 50% for session A; 90%, 98%, and 90% for session B; and 100%, 80%, and 56% for session C. Sensitivity did not significantly differ (P > .05) among reading sessions A, B, and C, whereas specificity and positive predictive values in session B were significantly higher (P < .001). For 6- and 12-month follow-up, no significant differences (P > .05) were found between sessions D and B. CONCLUSION: The combination of AEP and unenhanced imaging performed at 1-month follow-up offers improved specificity and positive predictive values compared with AEP alone. DEP imaging does not significantly increase sensitivity for detection of endoleaks, but it does depict low-flow endoleaks not seen at AEP.

Aged↗
PubMed1983

Brain nuclear magnetic resonance imaging enhanced by a paramagnetic nitroxide contrast agent: preliminary report.

Contrast-enhancing agents for demonstrating abnormalities of the blood-brain barrier may extend the diagnostic utility of proton nuclear magnetic resonance (NMR) imaging. "TES," a nitroxide stable free radical derivative, was tested as a central nervous system contrast enhancer in dogs with experimentally induced unilateral cerebritis or radiation cerebral damage. After intravenous injection of TES, the normal brain showed no change in NMR appearance, but areas of disease demonstrated a dramatic increase (up to 45%) in spin-echo intensity and a decrease in T1 relaxation times. The areas of disease defined by TES enhancement were either not evident on the nonenhanced NMR images or were better defined after contrast administration. In-depth tests of toxicity, stability, and metabolism of this promising NMR contrast agent are now in progress.

Animals↗
PubMed1986

Tissue contrast enhancement: image reconstruction algorithm and selection of TI in inversion recovery MRI.

It is clearly demonstrated that the proper application of the inversion recovery imaging pulse sequence is dependent on the method of image reconstruction and the selection of TI for optimum tissue contrast. There are two methods of 2DFT image reconstruction of IR sequence time-domain raw data. The first is a modulus-image reconstruction algorithm (contrast-obliterating option), and the second is a phase-correction routine for reconstructing "phase-sensitive" true IR-images. The second option generates proper "in-phase" images, retains proper scale of contrast, but can invert the algebraic sign of image-values under certain conditions. A series of "phase-sensitive" and "modulus" reconstructed brain images, obtained with conventional and optimized new IR pulse sequences, are shown to demonstrate these effects. They illustrate the considerable advantages gained, in practical clinical situations, if one generates "phase-sensitive" true IR-images from IR-sequence raw data at optimum TI for tissue contrast enhancement.

Algorithms↗
PubMed2002

Time-resolved contrast-enhanced imaging with isotropic resolution and broad coverage using an undersampled 3D projection trajectory.

Time-resolved contrast-enhanced 3D MR angiography (MRA) methods have gained in popularity but are still limited by the tradeoff between spatial and temporal resolution. A method is presented that greatly reduces this tradeoff by employing undersampled 3D projection reconstruction trajectories. The variable density k-space sampling intrinsic to this sequence is combined with temporal k-space interpolation to provide time frames as short as 4 s. This time resolution reduces the need for exact contrast timing while also providing dynamic information. Spatial resolution is determined primarily by the projection readout resolution and is thus isotropic across the FOV, which is also isotropic. Although undersampling the outer regions of k-space introduces aliased energy into the image, which may compromise resolution, this is not a limiting factor in high-contrast applications such as MRA. Results from phantom and volunteer studies are presented demonstrating isotropic resolution, broad coverage with an isotropic field of view (FOV), minimal projection reconstruction artifacts, and temporal information. In one application, a single breath-hold exam covering the entire pulmonary vasculature generates high-resolution, isotropic imaging volumes depicting the bolus passage.

Abdomen↗
PubMed2000

Spotting of disc haemorrhages on fundus pictures; on Kodachrome slides and on digitally enhanced images.

PURPOSE: To find out whether digital processing can facilitate interpretation of fundus photographs. METHODS: Digitised fundus pictures were manipulated and enhanced by a process called histogram equalisation. Essentially, the gamma values for red (R), green (G), and blue (B) were separately modified. The principle is explained and exemplified. MATERIAL AND RESULTS: Small disc haemorrhages, which may normally be hard to detect, became more visible after histogram equalisation, which is demonstrated in test series. CONCLUSION: Digital histogram equalisation offers a new way of looking at fundus pictures, which, alone or combined with other capabilities of digital processing, has great potential for diagnosis, as well as for follow up studies. The possibility to decide the true nature of suspect spots after applying the enhancement procedure is likewise of great value.

Diagnosis, Differential↗
PubMed1999

Infarcted myocardium in pigs: MR imaging enhanced with slow-interstitial-diffusion gadolinium compound P760.

PURPOSE: To assess the value of P760, a gadolinium chelate with slow interstitial diffusion and high relaxivity, for magnetic resonance (MR) imaging of acute myocardial infarction in pigs. MATERIALS AND METHODS: First-pass gradient-echo MR imaging and spin-echo MR imaging were performed with P760 and then with gadoterate meglumine in eight pigs with occlusive acute myocardial infarction. P760 signal intensity enhancement and clearance were compared with those of gadoterate meglumine. RESULTS: The first-pass enhancement ratio of P760 in normal myocardium was higher than that in infarcted myocardium (1.37 +/- 0.06 [SEM] vs 1.05 +/- 0.03, P = .03). The myocardial first pass showed a blood pool-like curve for P760. The blood pool enhancement ratio 40 seconds after injection was higher for P760 than for gadoterate meglumine (left ventricular cavity, 1.75 +/- 0.06 vs 1.45 +/- 0.06, P = .009). Spin-echo MR imaging showed improved contrast between normal and infarcted myocardium after P760 administration: The ratio before contrast material administration was 0.21 +/- 0.03, that at 15 minutes was 0.48 +/- 0.05 (P = .002), and that at 25 minutes was 0.47 +/- 0.07 (P = .003). CONCLUSION: P760 is an MR imaging contrast agent characterized by low diffusion, a blood pool effect soon after low-dose administration, and fast elimination. This agent is useful for improved myocardial perfusion MR imaging of acute myocardial infarction.

Animals↗
PubMed2005

Fetal magnetic resonance imaging enhances detection of spinal cord anomalies in patients with sonographically detected bony anomalies of the spine.

OBJECTIVE: Although fetal magnetic resonance imaging (MRI) is being increasingly used to evaluate sonographically suspected abnormalities, its utility in the evaluation of the spinal canal is not well studied. Because it is not susceptible to the limitations of fetal position, oligohydramnios, and shadowing from bony structures, we hypothesize that fetal MRI is better suited to assess the contents of the spinal canal compared with prenatal sonography. The purpose of this investigation was to determine whether fetal MRI could detect spinal abnormalities in cases in which they had not been originally suspected on prenatal sonography. METHODS: Fetal spine MR images were retrospectively reviewed over a 42-month period. Corresponding sonographic images were then rereviewed to determine whether there were findings in retrospect that might have suggested the cord abnormalities. Cases of myelomeningocele were counted as a spinal cord abnormality only if fetal MRI showed a cord anomaly other than the myelomeningocele. RESULTS: Of 33 cases referred for bony anomalies of the spine, fetal MRI showed additional abnormalities involving the spinal cord in 3 patients. These included diastematomyelia in 2 cases and segmental spinal dysgenesis in the third case. One case of diastematomyelia occurred in association with a lumbosacral myelomeningocele. The spinal cord anomalies were not visible on any of the prenatal sonograms, even in retrospect. CONCLUSIONS: Additional spinal cord anomalies were detected in 10% of cases reviewed. Fetal MRI can be useful in assessing the spinal cord in fetuses with bony spinal anomalies. Our findings suggest that fetuses with sonographically diagnosed bony abnormalities of the spine may benefit from further evaluation with fetal MRI.

Female↗
PubMed2000

MR angiography of the vascular tree from the aorta to the foot: combining two-dimensional time-of-flight and three-dimensional contrast-enhanced imaging.

A composite approach for magnetic resonance (MR) angiography of the lower extremities is described. Thirty patients were studied with this approach, which combined a two-dimensional (2D) time-of-flight (TOF) technique with a 3D contrast-enhanced technique. A head/neck coil was selected for imaging mid-foot to upper calf, and the body coil was used for the remainder of the peripheral vascular tree. Acquired data were transferred to a workstation for postprocessing. The final maximum intensity projection images, which display the entire vascular anatomy from aortic bifurcation to foot, were created using a 1024 x 1024 matrix. Very small arteries can be differentiated in critical regions like the calf and foot. Compared with TOF-2D alone, the scan time was reduced. This method offers another option for MR angiography of the lower extremities. J. Magn. Reson. Imaging 2000;12:884-889.

Adult↗
PubMed2000

Does quantitative ultrasound imaging enhance precision and discrimination?

The aim of this study was to compare quantitative ultrasound (QUS) measurements obtained using a new calcaneal QUS imaging device with a conventional non-imaging device using fixed transducers. The study group consisted of 340 healthy women with no risk factors associated with osteoporosis (176 premenopausal and 164 postmenopausal) and 83 women with one or more vertebral fractures. All women had QUS measurements performed on the Osteometer DTU-one (imaging) and Walker-Sonix UBA575+ (non-imaging) devices and bone mineral density (BMD) measurements performed at the spine and hip. A subgroup of 81 women had additional dual-energy X-ray absorptiometry (DXA) scans at the calcaneus. Short-term standardized precision (SP = SD/young adult SD) based on duplicate measurements was significantly better on the DTU for broadband ultrasound attenuation (BUA) (SP: DTU 0.15 vs UBA 0.21,p = 0.01) and speed of sound (SOS) (SP: DTU 0.14 vs UBA 0.18, p = 0.01). However, long-term SP of the DTU was comparable to or significantly poorer than the SP of the UBA device. The BUA and SOS measurements obtained on the DTU and UBA were significantly correlated (r = 0.76 and 0.89 for BUA and SOS measurements respectively). The correlations between QUS and BMD measurements were all significant, ranging from 0.53 to 0.72. No significant improvements in the correlation with axial or peripheral BMD were observed using the imaging device. All the QUS measurement parameters showed a significant negative relationship between age and years since menopause in the postmenopausal group. Annual losses were lower for the DTU for BUA (DTU 0.22 dB/MHz per year vs UBA 0.44 dB/MHz per year) but comparable for SOS (DTU 0.29 m/s per-year vs UBA 0.22 m/s per year). However, when these figures were standardized to take into account the clinical range, the annual losses were similar on the DTU and UBA. Age-adjusted odds ratios for each SD decline were similar on the DTU for BUA (DTU 3.2 vs UBA 3.3) and SOS (DTU 3.4 vs UBA 5.1). The corresponding odds ratios for BMD at the lumbar spine, femoral neck and total hip were 2.7, 2.9 and 3.3 respectively. Age-adjusted receiver-operating characteristics analysis yielded values for the area under the curve (AUC) ranging from 0.74 to 0.83. The DTU BUA AUC of 0.83 was significantly greater than the AUC obtained for UBA BUA and BMD measurements at the lumbar spine and femoral neck. Ultrasound imaging at the calcaneus was found to improve the standardized precision of BUA and SOS measurements in the short term but not in the long term. Neither the correlation with BMD nor the discriminatory ability of QUS was improved by utilizing QUS images at the calcaneus. The inconsistencies of the imaging system used for this study demonstrate that further development is required before it will be possible to show improvements in long-term precision.

Absorptiometry, Photon↗
PubMed1990

Parotid gland: plain and gadolinium-enhanced MR imaging.

The purpose of this study was to show the typical appearance of lesions of the parotid gland with plain MR imaging and MR imaging enhanced with gadopentetate dimeglumine. Seventeen patients with inflammatory changes and 43 with benign and malignant tumors were studied. The examinations were carried out with plain T1-weighted sequences with a repetition time (TR) of 500 msec and an echo time (TE) of 25 msec (TR/TE = 500/25), T2-weighted sequences (1,600/90), and gadolinium-enhanced T1-weighted sequences in axial, coronal, and sagittal orientations. For identifying normal anatomic structures such as the facial nerve and the main duct, the administration of gadopentetate dimeglumine was helpful. In inflammatory changes, gadolinium-enhanced images showed no diagnostic advantages. Gadopentetate dimeglumine proved helpful in delineating tumorous lesions and in differentiating benign and malignant lesions. However, an exact differentiation of the different histologic types was not possible. Post-operative fibrosis could be differentiated from recurrent tumors after administration of gadolinium. If a question regarding infiltration or definition of the boundaries of a lesion cannot be answered with non-enhanced MR imaging, gadopentetate dimeglumine administration is advised. However, for routine imaging of the parotid gland, its use is not recommended.

Contrast Media↗