Showing papers in "Journal of Computer Assisted Tomography in 1991"

Pharmacokinetic parameters in CNS Gd-DTPA enhanced MR imaging.

Abstract: Dynamic MR imaging can be used to study tissue perfusion and vascular permeability. In the present article a procedure for dynamic MR is presented, which (a) accurately resolves the fast kinetics of tissue response during and after intravenous infusion of the paramagnetic contrast medium Gd-DTPA and (b) yields a linear relationship between the measured MR signal and the Gd-DTPA concentration in the tissue. According to these features, the measured signal-time curves can be analyzed within the framework of pharmacokinetic modeling. Tissue response has been parameterized using a linear two-compartment open model, with only negligible effects of the peripheral compartment on the central compartment. The three model parameters were fitted to the signal-time data pixel by pixel, based on a set of 64 rapid SE images (SE 100/10 ms, image scan time 13 s, interscan intervals 11 s). This makes it possible to construct parameter images, whereby structures become visible that cannot be distinguished in conventional Gd-DTPA enhanced MR. As a clinical example, the approach is discussed in a case of glioblastoma.

A computerized brain atlas: construction, anatomical content, and some applications.

Abstract: An adjustable computerized atlas of the human brain has been developed, which can be adapted to fit individual anatomy. It is primarily intended for positron emission tomography (PET) but may also be used for single photon emission CT, transmission CT, magnetic resonance imaging, and neuroimaging-based procedures, such as stereotactic surgery and radiotherapy. The atlas is based on anatomical information obtained from brains fixed in situ soon after death. All structures have been drawn in on digitized photos of slices from one cryosectioned brain. The definition and classification of the anatomical structures and divisions are in agreement with the standard textbooks of anatomy, and the nomenclature is that of the Nomina Anatomica of 1965. The boundaries of the cortical cytoarchitectonic areas (Brodmann areas) have been determined using information from several sources, since three-dimensional literature data on their distribution are incomplete, scarce, and partly contradictory. However, no analysis of the cytoarchitectonics of the atlas brain itself has been undertaken. At present the data base contains three-dimensional representations of the brain surface, the ventricular system, the cortical gyri and sulci, as well as the Brodmann cytoarchitectonic areas. The major basal ganglia, the brain stem nuclei, the lobuli of the vermis, and the cerebellar hemispheres are also included. The computerized atlas can be used to improve the quantification and evaluation of PET data in several ways. For instance, it can serve as a guide in selecting regions of interest. It may also facilitate comparisons of data from different individuals or groups of individuals, by applying the inverse atlas transformation to PET data volume, thus relating the PET information to the anatomy of the reference atlas rather than to the patient's anatomy. Reformatted PET data from individuals can thus be averaged, and averages from different categories or different functional states of patients can be compared.

MR color mapping of myelin fiber orientation

Abstract: Diffusion of water in brain white matter has been shown to be anisotropic: Water mobility is lower when measured perpendicular to the fiber direction rather than parallel to it. This feature was used to produce images of the myelin fiber orientation. Coronal and sagittal MR diffusion images were obtained in volunteers using an echo-planar imaging sequence sensitized to molecular diffusion in perpendicular directions. Color-coded images of myelin orientation were then generated by combining these images together. The orientation of the white matter tracts was found to be in excellent agreement with known anatomy. Myelin fiber orientation mapping may offer a new perspective to evaluate white matter disorders.

Plastic transformation of PET images

Abstract: A theory and technique are presented that allow nonlinear resampling of positron emission tomography data to remove nonlinear differences in brain shape. The resampling is determined empirically by a function relating the observed image and a desired template. The validity, reliability, and precision of the plastic transformation are compared with linear rescaling alone, within, and between subjects.

MR imaging of anisotropically restricted diffusion of water in the nervous system: technical, anatomic, and pathologic considerations.

Abstract: The use of MR imaging to image anisotropically restricted diffusion (ARD) of water in the nervous system is described. The theoretical basis for the use of the pulsed gradient spin echo sequences is outlined, including an estimate of the range of cell dimensions that can be studied with this technique. The importance of restricted diffusion across myelinated white matter fibre tracts is emphasised and the capacity of MR imaging to demonstrate fibre pathways as a function of their direction is illustrated. Technical developments that have been implemented include 256 x 256 spatial resolution, a wider range of diffusion times Td, and an increased range of diffusion sensitivity parameters b. Effects of these are illustrated together with the use of gradient moment nulling methods, oblique sensitisation, and a smaller set of gradient coils that enable shorter values of echo time to be used with the same value of b. The anatomical basis for ARD imaging is analysed, and association, commissural, and projection fibre tracts are demonstrated in different planes. The published literature on variations of the apparent diffusion coefficient from normal is reviewed and examples where diffusion weighted images revealed information that was not necessarily apparent with conventional sequences are illustrated. These include cases of multiple sclerosis, chronic head injury, progressive multifocal leucoencephalopathy, cerebrovascular disease, astrocytoma, and probable metastases to the brain. Imaging of ARD affords a fascinating conjunction between the microscopic movement of water, the properties of myelinated white matter fibres, gross anatomy of the brain, and changes of the diffusion of water in disease.

3D PET using a Conventional Multislice Tomograph without Septa

Abstract: A conventional multislice positron emission tomography scanner was modified to operate without interplane septa to evaluate its performance in collecting and reconstructing data in a three-dimensional (3D) format, thereby significantly increasing system sensitivity. A 3D filtered backprojection algorithm was implemented and tested, using both computer simulations and phantom measurements. No artifacts were apparent in the test images, although the algorithm was shown to lead to a 11% degradation in transaxial resolution in the outer planes. Following septa removal, sensitivity was found to increase by a factor of 7 with an increase in scatter fraction from 16 to 41%. Axial resolution degraded from 6.9 to 7.7 mm full width at half maximum at the center of the field of view. The maximum count rate without septa was 2.4 x 10(5) cps, at a concentration of 0.4 microCi/ml, compared with 1.3 x 10(5) cps at 1.5 microCi/ml with septa. Brain studies were performed with volunteers using 18F-fluorodeoxyglucose, 18F-fluorodopa, and H2 15O to compare noise-equivalent count rates and qualitatively assess image quality over a wide range of imaging conditions.

MR of benign peripheral nerve sheath tumors.

Abstract: Seventeen benign peripheral nerve sheath tumors were studied using MR. In all cases T2 relaxation time, signal intensity on T1-weighted images (lesion/muscle ratio), detectability of nerve of origin, nerve-lesion relationship, and presence of a capsule were assessed. Sixteen tumors showed marked hyperintensity on T2-weighted images with T2 relaxation times values greater than 95 ms. One schwannoma was almost isointense with fat (T2 60 ms). All lesions were isointense with muscle on T1-weighted images. In schwannomas the nerve was usually situated at the periphery of the lesion and only in one case was it obliterated by the mass. In neurofibromas the nerve was either visible in a central position within the mass (two cases) or no longer visible (five cases). A capsule could be detected in 70% of the schwannomas and in 30% of the neurofibromas. In patients with soft tissue masses, MR may contribute to recognition of nerve sheath tumors by showing the nerve of origin and typical signal hyperintensity on T2-weighted images. It can also be helpful in distinguishing between schwannomas and neurofibromas by the location of the nerve of origin and the presence of a capsule.

Semiautomatic evaluation procedures for quantitative CT of the lung.

Abstract: Accuracy, reproducibility, and objectivity are important in quantitative assessment of lung density and structure by CT, and the measurement has to be carried out under tightly controlled conditions. We therefore employ respiratory gating at defined levels of inspiration for CT scanning. In the eval

Physiological effects of fast oscillating magnetic field gradients.

Abstract: To evaluate the physiological thresholds of neuromuscular stimulation relevant to very fast NMR imaging studies that use gradient switching at frequencies of 1–2 kHz and a maximum magnetic field of up to 10 mT, a series of studies were done with human volunteers using an experimental echo pl

Acetabular angles and femoral anteversion in dysplastic hips in adults: CT investigation

Abstract: Transpelvic CT was used to quantify the relationship between the acetabulum and proximal femur in 21 adult patients (33 hips) with congenital hip dysplasia (defined by a center edge angle of less than 20 degrees). The anterior and posterior acetabular sector angles (AASA and PASA) were measured, as well as the degree of acetabular and femoral anteversion. The results demonstrated deficient anterior acetabular support (i.e., decreased AASA) in approximately two-thirds of the dysplastic hips and reduced posterior support (i.e., decreased PASA) in one-third. The acetabular anteversion was normal. The femoral anteversion. however, was greater than normal in most hip. As important additional information is obtained by CT compared with conventional radiography, CT is recommended when operative procedures aimed at preventing or postponing osteoarthrosis are considered.

Localized 1H NMR spectroscopy in fifty cases of newly diagnosed intracranial tumors.

Abstract: Fifty patients with newly diagnosed, untreated intracranial tumors were examined with 1H nuclear magnetic resonance single-volume spectroscopy (MRS) using a 1.5 T whole-body MR system. Prior to the MRS, contrast enhanced MR and/or CT imaging studies were carried out. Histological verification was obtained in all patients except one. All tumor spectra revealed distinct abnormalities as compared with the normal brain spectra. Although most meningiomas showed a rather characteristic spectral pattern, generally features specific for the various tumor types were not observed. For instance, though a strong lactic acid signal was seen in most malignant tumors, this signal was also evident in five benign neoplasms.

Localized proton NMR spectroscopy of brain tumors using short-echo time STEAM sequences.

Abstract: Recent progress in localized proton NMR spectroscopy has been utilized to improve the spatial resolution and the metabolic specificity in a study of 19 patients with intracranial tumors. Selected examples demonstrate that short echo time stimulated echo acquisition mode sequences are able (a) to account for macroscopic tissue heterogeneity by reducing the volume of interest to 2-8 ml and (b) to facilitate a reasonable characterization of tumor metabolism by increasing the number of accessible metabolites. Proton NMR spectra were acquired within measuring times of 6.5 min on a 2.0 T whole-body system using the imaging headcoil.

3D surface rendered MR images of the brain and its vasculature.

Abstract: Both time-of-flight and phase contrast magnetic resonance angiography images are combined with stationary tissue images to provide data depicting two contrast relationships yielding intrinsic discrimination of brain matter and flowing blood. A computer analysis is based on nearest neighbor segmentation and the connection between anatomical structures to partition the images into different tissue categories: from which, high resolution brain parenchymal and vascular surfaces are constructed and rendered in juxtaposition, aiding in surgical planning.

CT-pathologic correlation of axillary lymph nodes in breast carcinoma.

Abstract: A prospective study was performed to determine whether thoracic CT yielded useful information regarding the status of axillary lymph nodes (LNs) in patients with breast cancer. Thirty-five consecutive patients with clinically suspected stage II or III breast carcinomas were scanned preoperatively from the supraclavicular regions to the lung bases. Axillary LNs measuring greater than or equal to 1 cm were considered abnormal. The lymph nodes were classified according to their relationship to the pectoralis muscle. Extracapsular lymph node extension was diagnosed when there was irregularity and spiculation of the lymph node margin with surrounding fatty infiltration. Correlation with axillary dissection was obtained in 20 patients, giving a positive predictive value for axillary metastases of 89% with 50% sensitivity, 75% specificity, and 20% negative predictive value. CT was also able to detect the level of axillary involvement accurately when the lymph nodes were enlarged and to evaluate extracapsular LN extension. Although superior to physical examination, CT was not an accurate predictor of axillary LN involvement, primarily because of its low negative predictive value.

Cardiac First-Pass and Myocardial Perfusion in Normal Subjects Assessed by Subsecond Gd-DTPA Enhanced MR Imaging

Abstract: To evaluate first pass in the right ventricular (RV) and left ventricular (LV) cavities and myocardial perfusion, subsecond MR imaging was performed in seven normal subjects following intravenous bolus injection of Gd-DTPA. After the baseline scans, sequential ECG-triggered images were obtained every three to four RR intervals. The procedure consisted of an initial presaturation pulse (150 degrees), and the acquisition time for one image was approximately 500 ms with 64 phase-encoding steps. After bolus administration of Gd-DTPA (0.05 mmol/kg body wt), progressively increasing signal intensities were observed in the RV cavity, the LV cavity, and the myocardial wall. Gadolinium DTPA enhanced subsecond MR offers temporal information of the first transit in the cardiac chambers and may provide useful clinical reference data for assessment of myocardial perfusion in patients with coronary artery disease.

Cancellous bone structure: analysis of high-resolution CT images with the run-length method.

Abstract: Quantitative computed tomography is extensively used to assess bone density; its potential to quantify bone structure, however, remains to be explored. In this work we present the modifications of the run-length method necessary to enable an analysis of the trabecular bone structure at the distal radius and the distal tibia. Furthermore, the close relationship between histomorphometric values and the run-length parameters is shown. The procedure may be regarded as a noninvasive, reproducible biopsy. For an adequate analysis, high resolution CT images are required. To obtain such images, we modified a special purpose CT system and achieved a high contrast resolution of 0.25 mm. The procedure was applied to groups of normal volunteers and osteoporotic patients, and the results are interpreted with the help of simple two- and three-dimensional models of the trabecular architecture.

Standardized quantitative high resolution CT in lung diseases

Abstract: Twenty-seven patients with diffuse fibrosing alveolitis (DFA), 27 patients with granulomatous lung disease (GLD), 3 patients with homozygous alpha 1-proteinase inhibitor deficiency (alpha 1-PID), and 6 healthy volunteers (C) were studied using thin section high resolution CT (HRCT) at 50% of actual vital capacity (VC), determined and controlled spirometrically during each exposure. A fast contour tracing algorithm was used to isolate the lung parenchyma followed by a quantitative histogram analysis of the frequencies of CT values. Mean CT values enabled us to discriminate significantly between the groups of C and alpha 1-PID. Significant differences were found between the groups of GLD and DFA versus C by applying suitably selected intervals of CT values. Moreover, if the patients were assigned to four different groups according to their lung function results (normal, restrictive, obstructive, restrictive and obstructive), again significant differences existed with respect to defined intervals of CT values. Mean CT values showed a significant negative correlation with lung function tests representative of lung parenchymal disease, i.e., VC, diffusing capacity, and exercise PaO2. Moreover, CT values ranging from -899 to -800 HU correlated positively, whereas CT value frequencies above -699 HU correlated inversely with these same lung function parameters. These results indicated that certain intervals of CT values do reflect functionally different abnormalities of lung parenchyma. It is concluded that an analysis of frequencies of CT values determined by spirometrically standardized HRCT provides objective quantitative data that reflect changes of pulmonary structure corresponding to lung function impairments. Thus, spirometrically standardized HRCT may be helpful for evaluating and staging patients with diffuse pulmonary disease.

MR of enchondroma and chondrosarcoma: rings and arcs of Gd-DTPA enhancement.

Abstract: MR studies of five chondrosarcomas and three enchondromas were performed with intravenous Gd-DTPA administration. All tumors showed enhancement of scalloped margins and curvilinear septa (ring-and-arc pattern) on T1-weighted SE sequences with Gd-DTPA. On radiologic-pathologic correlation, the enhanced areas corresponded to fibrovascular bundles surrounding hyaline cartilage lobules. The rings and arcs of enhancement with Gd-DTPA on MR is a reflection of the lobulated growth pattern of cartilaginous tumors and therefore helpful in differential diagnosis of bone tumors.

Cardiac tumors: assessment with Gd-DTPA enhanced MR imaging.

Abstract: Previous studies have shown the value of MR imaging for the identification of cardiac masses. The distinction of intramural tumors from normal myocardium may be equivocal because of the similarity of signal intensity between tumor and normal myocardium on ECG-gated SE images. The purpose of this study was to assess the role of Gd-DTPA for improving the contrast between cardiac tumors and myocardium. Four patients with established or suspected cardiac tumors were imaged with a 1.5 T imager. The T1-weighted images (TR = RR interval, TE = 20-30 ms) were obtained before and immediately after the intravenous injection of Gd-DTPA, at a dosage of 0.1 mmol/kg. Tumors were identified in three patients. All tumors were isointense to the myocardium in precontrast images but demonstrated differential enhancement relative to myocardium after the administration of Gd-DTPA. Two tumors were hyperintense relative to myocardium, and the third was mostly hypointense, surrounded by a hyperintense rim. In the remaining case, no tumor was found and the myocardium was homogeneously enhanced on postgadolinium images. Gadolinium DTPA can produce differential enhancement of tumor from normal myocardium and therefore demonstrate intramural masses.

Evaluation of adrenal masses in oncologic patients: dynamic contrast-enhanced MR vs CT.

Abstract: The CT examinations, precontrast gradient echo MR images, and fast contrast enhanced dynamic MR studies were evaluated in 44 patients with 52 adrenal masses and known malignant disease of different origin. Morphologic features (size, shape, attenuation, contour, and enhancement) on CT scans, signal intensity on T2-weighted MR images, and patterns of enhancement on Gd-DTPA enhanced dynamic MR studies were analyzed in all patients. With dynamic contrast enhanced studies with prolonged imaging up to 15 min after Gd-DTPA, masses with moderate enhancement and complete washout after 10 min were considered as adenomas. Computed tomography and plain MR had a sensitivity of 0.71 and 0.96, a specificity of 0.75 and 0.88, and overall accuracy of 0.56 and 0.71, respectively. Simultaneous use of precontrast MR and dynamic contrast enhanced studies led to an accurate diagnosis in 88% (sensitivity = 1.0, specificity = 0.91) and thus should be considered in oncologic patients with undetermined adrenal masses.

Measuring random microscopic motion of water in tissues with MR imaging: a cat brain study.

Abstract: Cat brain images sensitized to incoherent motion by additional gradient pulses were obtained on a 4.7 T magnetic resonance unit equipped with shielded gradient coils. The apparent diffusion coefficient of water in gray and white matter was accurately determined and imaged from the signal attenuation curve obtained as a function of gradient strength. Contrast in calculated diffusion images differed from typical T2-weighted contrast. Furthermore, in gray matter and in areas containing flowing CSF the attenuation curve was found to be biexponential. These results are interpreted in terms of a simple voxel model with microcirculation and diffusion contributions.

MR imaging of anisotropically restricted diffusion in the brain of neonates and infants.

Abstract: Brain MR examinations were performed on one normal and 30 abnormal neonates and infants with a variety of clinical problems using pulsed gradient spin echo (PGSE) sequences sensitized in different directions to detect changes due to anisotropically restricted diffusion of water within the brain. Anisotropically restricted diffusion was demonstrated within white matter, which appeared to be myelinated with T1-weighted inversion recovery or spin echo sequences and within white matter where the presence of myelin was not demonstrated with these sequences. Cysts and fluid collections were recognised by their low signal intensity using PGSE sequences in the subcortical regions, lentiform nuclei, and periventricular regions. An intracerebral hematoma and a subdural hematoma showed a high signal intensity with PGSE sequences consistent with isotropically restricted diffusion. Chronic infarction displayed a low signal intensity consistent with relatively free isotropic diffusion. Patients with leukodystrophy associated with congenital muscular dystrophy showed an anisotropic pattern with different components of the abnormality present on images with sensitization in different directions. The corticospinal tracts failed to show highlighting in three cases where conventional imaging was normal. In several patients with a history of birth asphyxia, asymmetry and a relative reduction in signal intensity were seen in the corticospinal tracts.

High Dose Chloral Hydrate Sedation for Children Undergoing CT

Abstract: Chloral hydrate is commonly used to sedate children before CT. However, no prospective study has been published of the safety and efficacy of chloral hydrate at high dose levels for children undergoing CT. We define high dose levels of oral chloral hydrate to be 80-100 mg/kg, with a maximum total dose of 2 g. High dose chloral hydrate sedation was administered orally to 295 children for 326 CT examinations. Adverse reactions occurred in 7% of the children, with vomiting being the most common (4.3% of children). Hyperactivity and respiratory symptoms each occurred in less than 2% of children. Prolonged sedation ( greater than 2 h) was not encountered in our series. Sedation was successful in producing motion free CT examinations, so that in 303 (93%) of the cases, no repeat CT scans were needed. We conclude that high dose oral chloral hydrate provides safe and effective sedation for children undergoing CT.

Wegener granulomatosis: CT features of parenchymal lung disease

Abstract: Chest CT from eight patients with pulmonary Wegener granulomatosis were reviewed. The CT features of parenchymal lung involvement included multiple nodules or masses (seven of eight; 88%), ranging in size from 0.3 to 5.0 cm. Lung nodules demonstrated distinct feeding vessels in seven of eight patients (88%); and lesions similar to pulmonary infarcts, i.e., peripheral wedge-shaped lesions abutting the pleura, were identified in seven cases (88%). Scarring, spiculation, and pleural tags emanating from pulmonary nodules were prominent features (seven of eight; 88%). Other findings included cavitation (four of eight; 50%), air bronchograms through nodules (two of eight; 25%), and pleural effusions (two of eight; 25%). One patient on immunosuppressant therapy also demonstrated scattered ground glass infiltrates due to complicating pneumocystis pneumonia. In comparison to corresponding conventional chest radiography, CT examinations revealed more parenchymal lesions in five of eight cases (63%) and bilateral disease instead of unilateral disease in one of eight cases (13%). Feeding vessels were only identified on CT. Wegener granulomatosis is a primary necrotizing granulomatous vasculitis, and when it affects the lung it demonstrates CT features that are similar to other vessel-related disorders of the lung such as septic emboli, pulmonary infarcts, and tumor emboli of hematogenous metastases. We believe that these CT features--nodules with feeding vessels and wedge-shaped lesions abutting the pleura--are related to the necrotizing angiitis that affects pulmonary arteries and veins in this disease.

FDG-PET in the selection of brain lesions for biopsy.

Abstract: The CT-guided stereotaxic needle biopsy has become a widely used procedure in the diagnostic evaluation of intracranial lesions including tumors. Conventional CT or MR frequently defines the anatomic regions of abnormality, which may be multiple lesions or a single lesion that is heterogeneous in cellular composition owing to the topographic variation of cellular constituency or the combination of active disease, nonspecific inflammation, necrosis, and/or edema. In these cases, selection of the most appropriate site for a successful diagnostic needle biopsy can be difficult. In three patients, we have used (18F)fluorodeoxyglucose (FDG) positron emission tomography (PET) to determine the site most likely to provide a diagnostic biopsy result. In the first patient, who presented with confusion, multiple biopsies from the temporal lobe, based on MR abnormalities, revealed only reactive gliosis and edema. Repeat biopsy directed by PET revealed an anaplastic astrocytoma. In a second patient, PET allowed us to differentiate radiation effect from active metastatic breast cancer. In the third patient, who presented with a grand mal seizure, biopsy of a CT-defined hypodense region demonstrated lymphocytosis. Metabolism of FDG was normal or increased in areas of Aspergillus encephalitis at autopsy. These preliminary studies suggest a complementary role for FDG-PET and CTmore » or MR in selected patients for defining the intracranial site most likely to yield a positive biopsy result.« less

MR and CT appearance of nodular fasciitis.

Abstract: Nodular fasciitis is a common soft-tissue tumor that remains almost unreported in the radiology literature. We retrospectively reviewed all available imaging studies on three patients with nodular fasciitis studied by MR at our institution. The lesions were round to oval in configuration, ranging in

MR phase-shift velocity mapping of mitral and pulmonary venous flow

Abstract: Mitral and pulmonary venous flows are important indexes in the evaluation of left ventricular diastolic function and in the assessment of mitral valve disease. We used MR phase-shift velocity mapping to measure mitral and pulmonary venous flow velocity in 10 healthy volunteers and mitral flow veloci

Hepatocellular tumors with high signal on T1-weighted MR images: chemical shift MR imaging and histologic correlation.

Abstract: We reviewed conventional and chemical shift MR images and histologic findings of seven proven primary hepatic masses that had higher signal than liver on T1-weighted images to determine if this necessarily indicates fat and if the presence of fat indicates malignancy. These seven masses included five hepatocellular carcinomas (HCCs), one focal nodular hyperplasia (FNH), and one fatty dysplastic nodule. An eighth solitary high signal mass without histologic proof had evidence of abundant fat on each of two chemical shift MR images 25 months apart. Only one of the five HCCs had chemical shift or histologic evidence of fat, while the FNH and dysplastic nodule each had both chemical shift and histologic confirmation of fat. The dysplastic nodule became more dysplastic and grew significantly within 14 months, but remained benign. The unproven fatty lesion decreased in size over 25 months and is therefore presumably benign. Although no statistical inferences can be drawn from this small correlative study, we have shown that HCC may have higher signal intensity than liver on T1-weighted images, whether or not it contains fat. Chemical shift techniques can confirm the presence of intratumoral fat and thus indicate a mass of hepatocellular origin, but the mass may be benign or malignant.

CT findings after uncomplicated percutaneous laparoscopic cholecystectomy.

Abstract: To investigate the postoperative pulmonary and abdominal findings following uncomplicated percutaneous laparoscopic cholecystectomy, 27 patients were studied by upper abdominal CT within 24 h of the surgical procedure. Both pneumoperitoneum (70%) and subcutaneous emphysema (56%) were commonly observed. Postoperative atelectasis and pleural effusions were observed in 44 and 33% of the patients, respectively. Forty-eight percent of the patients had a postoperative ileus demonstrated by CT. Approximately 22% of the patients had fluid in the abdomen as either edema in the gallbladder fossa or small amounts of ascites. In our patients the amount of ascitic fluid was small and no clinical significance could be attributed to the intraabdominal fluid collections.

"Dural tail sign": a specific MR sign for meningioma?

Abstract: Somewhat conflicting reports have appeared about the significance of linear meningeal thickening and enhancement adjacent to peripherally located cranial mass lesions on contrast enhanced magnetic resonance images. Some authors consider this finding nearly diagnostic of meningioma. In an attempt to determine the specificity of this so-called tail sign, particularly with respect to meningioma, we retrospectively reviewed 16 cases from institutional records. From our results, the tail sign appears to be highly suggestive but not specific for meningioma.