Femoral neck radiography: effect of flexion on visualization.

OBJECTIVES: To determine whether flexion improves radiographic visualization of the femoral neck when the femur is externally rotated. METHODS: Five human femora, with varying neck-shaft and anteversion angles, were measured and immobilized. Degree of flexion required to bring the femoral neck horizontal was measured, varying the rotation. Next, one bone was radiographed in 16 positions, varying rotation in 15 degrees and flexion in 10 degrees increments. Radiographs were presented in randomized blinded fashion to 15 staff radiologists for scoring of femoral neck visualization. Following this, all 5 bones were radiographed in 4 positions of rotation and at 0 degree and 20 degrees flexion, and blinded randomized review of radiographs was repeated. Comparisons between angles and rotations were made using the Mann-Whitney test. RESULTS: The flexion angle required to bring the long axis of the femoral neck horizontal correlated directly with the degree of external rotation (p < 0.05). Visualization of the femoral neck in the extended position progressively deteriorated from 15 degrees internal rotation to 30 degrees external rotation (p < 0.01). However, when 20 degrees flexion was applied to bones in external rotation, visualization significantly improved at 15 degrees (p < 0.05) and 30 degrees (p < 0.01). CONCLUSION: Flexion of the externally rotated femur can bring the femoral neck into horizontal alignment, and a relatively small amount (20 degrees) of flexion can significantly improve radiographic visualization. This manoeuvre could be useful for radiography of the femoral neck when initial radiographs are inadequate because of external rotation of the leg.     

Emptying the gallbladder prior to intravenous cholangiography: effect on gallbladder visualization.

Experiments were done to test the hypothesis that emptying the gallbladder prior to intravenous cholangiography (IVC) would result in earler and better opacification of the gallbladder. Five dogs were studied on two separate days in a crossover experiment. Each dog had a standard IVC (15-minute infusion of meglumine iodipamide) 2.5 cc/kg of following a 14-16-hour fasting period. On one of the days, 0.3 mcg/kg of Ceruletide was intramuscularly administered to each dog 30 to 45 minutes prior to the iodipamide infusion. Films obtained at the end of infusion and at 20, 40, 60, and 90 minutes were evaluated independently by three radiologists. The results indicate that pretreatment with Ceruletide produces a significant (p less than 0.05) improvement in the quality of gallbladder opacification during the first 90 minutes following iodipamide infusion. We conclude that earlier and better opacification of the gallbladder during IVC can be obtained by prior emptying of the gallbladder with a cholecystokinetic agent.     

Image processing in digital chest radiography: effect on diagnostic efficacy.

The usefulness of digital image processing of chest radiographs was evaluated in a clinical study. In 54 patients, chest radiographs in the posteroanterior projection were obtained by both 14 inch digital image intensifier equipment and the conventional screen-film technique. The digital radiographs (512 x 512 image format) viewed on a 625 line monitor were processed in three different ways: (1) standard display; (2) digital edge enhancement for the standard display; and (3) inverse intensity display. The radiographs were interpreted independently by three radiologists. The diagnoses were confirmed by CT, follow-up radiographs and clinical records. Chest abnormalities of the films analyzed included 21 primary lung tumors, 44 pulmonary nodules, 16 cases with mediastinal disease and 17 cases with pneumonia/atelectasis. Interstitial lung disease, pleural plaques, and pulmonary emphysema were found in 30, 18 and 19 cases, respectively. The sensitivity of conventional radiography when averaged overall findings was better than that of the digital techniques (P less than 0.001). The differences in diagnostic accuracy measured by sensitivity and specificity between the three digital display modes were small. Standard image display showed better sensitivity for pulmonary nodules (0.74 vs 0.66; P less than 0.05) but poorer specificity for pulmonary emphysema (0.85 vs. 0.93; P less than 0.05) compared with inverse intensity display. We conclude that when using 512 x 512 image format, the routine use of digital edge enhancement and tone reversal at digital chest radiographs is not warranted.     

The effect of fractionated administration of locetamic acid (Cholebrine) on gallbladder visualization.

Fractionated administration of iopanoic acid (Telepaque) has already been shown to result in superior visualization of the gallbladder. A similar study was undertaken to evaluate the effect of fractionation when iocetamic acid (Cholebrine) is employed. It was found that the gall bladder is opacified better if Cholebrine is given in a single dose.     

Enhanced visualization and quantification of magnetic resonance diffusion tensor imaging using the p:q tensor decomposition

Many scalar measures have been proposed to quantify magnetic resonance diffusion tensor imaging (MR DTI) data in the brain. However, only two parameters are commonly used in the literature: mean diffusion (D) and fractional anisotropy (FA). We introduce a visualization technique which permits the simultaneous analysis of an additional five scalar measures. This enhanced diversity is important, as it is not known a priori which of these measures best describes pathological changes for brain tissue. The proposed technique is based on a tensor transformation, which decomposes the diffusion tensor into its isotropic (p) and anisotropic (q) components. To illustrate the use of this technique, diffusion tensor imaging was performed on a healthy volunteer, a sequential study in a patient with recent stroke, a patient with hydrocephalus and a patient with an intracranial tumour. Our results demonstrate a clear distinction between different anatomical regions in the normal volunteer and the evolution of the pathology in the patients. In the normal volunteer, the brain parenchyma values for p and q fell into a narrow band with 0.976相似文献   

Multidetector-row CT: economics and workflow

With rapid evolution of multidetector-row CT (MDCT) technology and applications, several factors such as technology upgrade and turf battles for sharing cost and profitability affect MDCT workflow and economics. MDCT workflow optimization can enhance productivity and reduce unit costs as well as increase profitability, in spite of decrease in reimbursement rates. Strategies for workflow management include standardization, automation, and constant assessment of various steps involved in MDCT operations. In this review article, we describe issues related to MDCT economics and workflow.     

Enhanced positive‐contrast visualization of paramagnetic contrast agents using phase images

Iron oxide–based MRI contrast agents are increasingly being used to noninvasively track cells, target molecular epitopes, and monitor gene expression in vivo. Detecting regions of contrast agent accumulation can be challenging if resulting contrast is subtle relative to endogenous tissue hypointensities. A postprocessing method is presented that yields enhanced positive‐contrast images from the phase map associated with T₂*‐weighted MRI data. As examples, the method was applied to an agarose gel phantom doped with superparamagnetic iron‐oxide nanoparticles and in vivo and ex vivo mouse brains inoculated with recombinant viruses delivering transgenes that induce overexpression of paramagnetic ferritin. Overall, this approach generates images that exhibit a 1‐ to 8‐fold improvement in contrast‐to‐noise ratio in regions where paramagnetic agents are present compared to conventional magnitude images. This approach can be used in conjunction with conventional T₂* pulse sequences, requires no prescans or increased scan time, and can be applied retrospectively to previously acquired data. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Digital image processing: effect on detectability of simulated low-contrast radiographic patterns

Detection studies of simulated low-contrast radiographic patterns were performed with a high-quality digital image processing system. The original images, prepared with conventional screen-film systems, were processed digitally to enhance contrast by a "windowing" technique. The detectability of simulated patterns was quantified in terms of the results of observer performance experiments by using the multiple-alternative forced-choice method. The processed images demonstrated a significant increase in observer detection performance over that for the original images. These results are related to the displayed and perceived signal-to-noise ratios derived from signal detection theory. The improvement in detectability is ascribed to a reduction in the relative magnitude of the human observer's "internal" noise after image processing. The measured dependence of threshold signal contrast on object size and noise level is accounted for by a statistical decision theory model that includes internal noise.     

Three-dimensional visualization and analysis methodologies: a current perspective.

Three-dimensional (3D) imaging was developed to provide both qualitative and quantitative information about an object or object system from images obtained with multiple modalities including digital radiography, computed tomography, magnetic resonance imaging, positron emission tomography, single photon emission computed tomography, and ultrasonography. Three-dimensional imaging operations may be classified under four basic headings: preprocessing, visualization, manipulation, and analysis. Preprocessing operations (volume of interest, filtering, interpolation, registration, segmentation) are aimed at extracting or improving the extraction of object information in given images. Visualization operations facilitate seeing and comprehending objects in their full dimensionality and may be either scene-based or object-based. Manipulation may be either rigid or deformable and allows alteration of object structures and of relationships between objects. Analysis operations, like visualization operations, may be either scene-based or object-based and deal with methods of quantifying object information. There are many challenges involving matters of precision, accuracy, and efficiency in 3D imaging. Nevertheless, 3D imaging is an exciting technology that promises to offer an expanding number and variety of applications.     

Thoracic duct: visualization at nonenhanced MR lymphography--initial experience.

In six healthy volunteers, the thoracic duct was examined at magnetic resonance (MR) lymphography without contrast agent. With a 1.5-T clinical imager, a short echo spacing, three-dimensional, half-Fourier fast spin-echo sequence with electrocardiographic gating was employed to depict the thoracic duct along the thoracic aorta. The images clearly depicted the main duct in the region of the thoracic aorta in all six volunteers, drainage into the left subclavian region in four, and the cisterna chyli in one.     

MR visualization of the insula.

Magnetic resonance imaging (MRI) has made possible non-invasive research on the living human brain. However, three-dimensional display of areas obscured by the operculum deep within the cortex has been difficult. This study used MRI in an attempt to establish a three-dimensional method of displaying an obscured brain structure (the insula). A three-dimensional image of the insular cortex was constructed from horizontal MR images. As a result, the major anatomical landmarks of the insula were clearly displayed. This method makes possible non-invasive display and analysis of obscured structures deep in the brain, overcoming the disadvantage presented by the use of sectional images.     

Optimal visualization of esophageal varices.

Twelve patients with known esophageal varices and willingness to cooperate were included in the study. Medications administered were placebo, 2 mg of glucagon, and 30 mg of propantheline bromide. All medications were given double-blind and crossover. On the basis of this study the authors believe that for optimal visualization of esophageal varices the following is the procedure of choice: (1) the patient should remain horizontal (this is best done in the left lateral position for comfort and ease of expectoration) for ten minutes after swallowing high density barium; (2) the patient should "clear his throat" frequently and expectorate all saliva (barium sticks to the pharynx and makes the patient want to swallow and "clearing his throat" by forced expiration helps the patient to expectorate this coating and prevents swallowing); (3) filming should be done in expiration in the supine (left posterior oblique to table top) position; and (4) in equivocal cases the examination can be repeated with an anticholinergic drug if the patient has no contraindications to its use. The patient should empty his bladder just before administration of the drug. The intelligent use of these factors should result in a saving of both fluoroscopic time and film, and give the radiologist a safe optimal diagnostic yield.     

Surface modeling--uncertainty estimation and visualization.

The work presents a method of determining uncertainty of surface-based models that are reconstructed fragments of a human body built on the basis of slice images received from computed tomography CT or magnetic resonance imaging MRI. An analysis of geometric structure of the models has been carried out determining features, such as local inclination angle of the normal to the surface relative to the direction of scanning, and local radius of curvature. These features, together with the distance between slice images, have the largest influence on accuracy of the reconstructed surface-based models. A model of uncertainty has been determined by comparing properly selected virtual anatomical models and their spatial reconstructions. The estimated uncertainty model has then been employed to determine local errors in geometric structure of surface-based models. A quality visualisation of the errors in the geometric model has been presented in the form of a colour scale, and a quantity visualisation in the form of a ribbon, whose width is proportional to the uncertainty model.