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Biomedical subjects

D Norman

Publications and source records attributed to D Norman.

At least 181 records · Page 10Linked to original sources
PubMed1986

Spin-echo MR imaging of intracranial hemorrhage.

This retrospective study was performed to describe the appearance of intracranial hemorrhagic lesions on magnetic resonance (MR) imaging at 0.35 tesla using the spin-echo technique, and define the present clinical role of MRI in this particular pathology. Forty-eight examinations of forty-three patients with forty-seven intracranial hemorrhagic lesions (39 true hematomas and 8 hemorrhagic lesions mixed with other tissues) were reviewed for this study. Comparative CT studies were available for all the patients. In our limited experience with acute hematomas (less than 3 days old), low or isointense signal was seen with a short TR (0.5 s), but a relative increase in signal intensity was observed with a long TR (2.0 s). This appearance of acute hematoma was not specific. Chronic hematomas (more than 3 days old) were imaged as foci of bright signal intensity on both short and long TR. This pattern was characteristic of chronic hematoma. With a short TR (0.5 s), two hemorrhagic lesions (5 and 7 days old) were displayed as an isointense signal surrounded by a rim of high intensity signal. This peripheral zone most likely represented liquefaction at the clot's periphery and the initial formation of methemoglobin. T1 and T2 relaxation times were found to be very long for acute hematomas (first two days). T1 values of chronic hematomas (more than 3 days old) were comparatively short and in the same range as T1 of white matter. T2 values of chronic hematomas decreased also but remained very long.

Acute Disease↗
PubMed1986

Contrast enhancement of brain tumors and irradiated normal brain: a comparison of iohexol and iothalamate.

The nonionic contrast agent iohexol was compared with the ionic agent iothalamate for contrast enhancement of brain tumors and radiation brain damage in dogs. Tissue enhancement during infusion of contrast and 5, 10, 15 and 30 min later was measured using quantitative computed tomography. Blood iodine was measured using x-ray fluorescence. Peak contrast enhancement occurred during infusion in tumors and after 5 min in irradiated normal brain for both contrast agents. Absolute uptake of contrast in each lesion was the same for both agents when normalized to total grams of iodine administered. Blood iodine levels were slightly but not significantly higher using iohexol. The reduced osmotic load and similar contrast enhancement of lesions suggest that the nonionic contrast medium iohexol may be a useful agent for routine CT of the brain.

Animals↗
PubMed1986

Brain radiation lesions: MR imaging.

This retrospective study was performed to assess the capability of magnetic resonance (MR) to depict and characterize diffuse and focal radiation lesions in the brain using the spin-echo technique. The MR images of 55 patients who had undergone radiation therapy were reviewed. Comparative computed tomography (CT) studies were available for all the patients. Normal white matter was chosen as reference tissue for the quantitative comparison of signal intensities. Radiation lesions (identified in eight patients) were seen as regions of high signal intensity on the sequence with a long repetition time (TR) (2.0 sec) and showed no difference in signal compared with white matter when the TR was short (0.5 sec). Nonspecific prolongation of T1 and T2 relaxation times was measured in such lesions. In one patient, subependymal tumor spread, demonstrated by contrast-enhanced CT, was missed on MR images, masked by the adjacent abnormal signal owing to radiation effects. Recurrent or residual brain tumor could not be distinguished from radiation brain necrosis either by CT or by MR imaging. It is concluded that MR can depict radiation lesions with great sensitivity but is not very helpful for discrimination between recurrent or residual brain tumor, radiation necrosis, and other brain lesions.

Adolescent↗
PubMed1986

Pseudotumor of the craniovertebral junction associated with chronic subluxation: MR imaging studies.

Masses at the craniovertebral junction generally have serious prognostic implications. However, the authors studied three patients who had chronic atlantoaxial subluxation from either degenerative disease or congenital dysplasia of the dens and who also had benign fibrous masses in this region, confirmed at surgery. The association of masses of the craniovertebral junction with chronic atlantoaxial subluxation raises the possibility that the underlying cause of the masses is chronic mechanical irritation. All patients were imaged with metrizamide myelography and adjunctive computed tomography (CT), then by magnetic resonance (MR) imaging. MR images were not only superior to myelograms and CT scans in delineating the exact extent of the lesions, they also indicated the benign, fibrous nature of the masses.

Adult↗
PubMed1986

Pituitary adenomas: high-resolution MR imaging at 1.5 T.

The magnetic resonance (MR) images of 28 patients with surgically confirmed pituitary adenomas were retrospectively evaluated. The examinations were performed on a 1.5-T superconducting MR system using a multisection spin-echo technique with 3-mm-thick sections and a 256 X 256 matrix. T1- and T2-weighted images were obtained in sagittal and coronal planes. The MR findings were correlated with detailed operative reports and diagrams. There were 11 microadenomas and 17 macroadenomas. Ten of the microadenomas and all of the macroadenomas were accurately localized and their extent delineated, particularly on T1-weighted coronal sections. Adenomas typically appeared hypointense on T1-weighted coronal sections. The appearance on T2-weighted images was variable, and generally the lesions were less well seen. Involvement of parasellar structures, particularly the optic chiasm and cavernous sinuses, was accurately depicted. Cyst formation and hemorrhage could be characterized in some instances. In general, there was excellent correlation between MR imaging and operative findings.

Adenoma↗
PubMed1986

Intracranial lesions: flow-related enhancement on MR images using time-of-flight effects.

Many physico-anatomic variables and instrument parameters influence the relative magnetic resonance signal intensity of vascular channels. The interaction of these mechanisms is complex, but their composite effects can be accounted for by two main categories of flow phenomena: time-of-flight effects and spin-phase changes. Of these two mechanisms only the time-of-flight effect known as flow-related enhancement produces augmentation of intravascular signal. Flow-related enhancement can potentially provide positive contrast of diagnostic value in terms of anatomic depiction of vascular detail as well as physiologic characterization of blood flow. The authors have used a single-section, selectively irradiated, spin-echo pulse sequence to maximize flow-related enhancement within a variety of intracranial lesions, as a supplement to their regular imaging. The technique was found to be diagnostically useful in improving the conspicuity of vascular lesions, in determining vessel patency, in distinguishing flow void from calcification, and in obtaining semiquantitative information about flow dynamics.

Brain Diseases↗
PubMed1986

MRI of angiographically occult vascular malformations.

Eleven patients with 15 angiographically occult arteriovenous malformations were studied by magnetic resonance (MR) imaging and computed tomography (CT). Five patients had biopsy proof; six were clinically diagnosed from the long-term clinical follow-up (more than 3 years) and imaging features. Of the 15 lesions, 11 were recognized by both CT and MR. Each method was falsely negative for two lesions. The most useful contribution of MR in the characterization of angiographically occult arteriovenous malformations was the depiction of hemorrhagic foci in 12 of 13 lesions seen on MR. High-attenuation foci indicative of hematomas were seen in only five lesions on CT; the rest were iso- or hypoattenuating. CT detected two very small lesions, in one case as punctate foci of enhancement and in the other as punctate calcification, that were not seen with MR. MR complements CT in characterizing angiographically occult arteriovenous malformations and in distinguishing them from similar-appearing lesions, in particular, small neoplasms. However, when such lesions are seen with only focal calcification and subtle enhancement on CT, routine MR may miss them.

Adolescent↗
PubMed1986

Foci of MRI signal (pseudo lesions) anterior to the frontal horns: histologic correlations of a normal finding.

Review of all normal magnetic resonance (MR) scans performed over a 12-month period consistently revealed punctate areas of high signal intensity on T2-weighted images in the white matter just anterior and lateral to both frontal horns. Normal anatomic specimens were examined with attention to specific characteristics of this region. Three unique features typify the brain tissues that correspond to the foci of high signal. First, this region of the brain is notable for its loose network of axons with low myelin content. Second, pathologic scrutiny revealed an entity called "ependymitis granularis," which represents patchy loss of the ependyma in the frontal horns with astrocytic gliosis. Third, flow of interstitial fluid within this region of the brain tends to converge at the dorsal-lateral angle of the frontal horns. All these factors contribute to increased water content locally, which results in foci of high signal intensity anterior to the frontal horns in all normal MR scans.

Adolescent↗
PubMed1986

Gd-DTPA in clinical MR of the brain: 1. Intraaxial lesions.

Over 35 intraaxial lesions in 15 patients suspected of having intracranial tumors were studied with MR before and after injection of Gadolinium-DTPA (Gd-DTPA). Diseases included primary and metastatic brain tumors, plaques of multiple sclerosis, occult arteriovenous malformations, lymphoma, toxoplasmosis, and pituitary adenoma. The precontrast T2-weighted sequence (SE 2000/30, 60) was found to be most sensitive in detecting intraaxial lesions, showing 17 lesions that were not seen on the post-Gd-DTPA T1-weighted sequence (SE 500/30). In one case of multiple sclerosis, several lesions seen on the pre-Gd-DTPA study on T2-weighted images faded after injection of Gd-DTPA (due to T2 shortening). In two patients with large metastatic foci, other small metastatic lesions were seen better after Gd-DTPA on both T1- and T2-weighted sequences. Four other patients with only one focal-enhancing lesion and one patient with multifocal lesions on T1-weighted images actually had a much larger single glioma depicted on pre-Gd-DTPA T2-weighted images. In a patient with AIDS, a ring-enhancing lesion thought to be an abscess proved to be lymphoma. The cryptic arteriovenous malformations enhanced but showed more characteristic findings, such as hemorrhage, on pre-Gd-DTPA studies. Our experience suggests that Gd-DTPA may not improve sensitivity of MR in the detection of intraaxial lesions. However, functional aspects of brain disease, such as the presence of perfusion of a lesion and active breach of the blood-brain barrier, are depicted well with Gd-DTPA and are vital for proper diagnosis in many instances.

Adult↗
PubMed1986

Gadolinium-DTPA in the magnetic resonance evaluation of the postoperative patient. Work in progress.

The application of gadolinium-DTPA to magnetic resonance scanning has been demonstrated to have considerable potential. Because the evaluation of the post-operative patient is particularly difficult for magnetic resonance due to the non-specific appearance of surgical trauma and edema, we attempted to formulate some preliminary impressions regarding the use of gadolinium-DTPA in this setting based on our experience with 15 patients studied at varying intervals following surgery, from 2 days to 8 years. Specifically, the time course and appearance of normal post-surgical enhancement was found to exhibit certain patterns. Recognition of these patterns may allow differentiation from pathology and may result in gadolinium-DTPA adding useful information in evaluating these patients.

Adult↗
PubMed1986

Magnetic resonance characterization of non-flowing intravascular blood.

We eliminated the effects of flow on the magnetic resonance (MR) appearance of intraluminal blood by imaging the superficial veins in the arms and legs of 3 volunteers during venous occlusion with tourniquets. T1, intermediate and T2 weighted transaxial images were obtained using a multisection spin-echo technique at 1.5 T. The images were analyzed by visual inspection and by region of interest pixel intensity measurements. The intensity of non-flowing blood was compared with muscle, fat and a tube of water taped to the skin. We determined that non-flowing, unclotted blood has intermediate T1 characteristics and long T2 characteristics. On T1 weighted images, non-flowing blood is of greater signal intensity than water or muscle, but less than fat. On T2 weighted images, non-flowing blood is of greater signal intensity than fat and muscle, but slightly less than water. These results may help explain the signal observed with very slow intravascular flow and hyperacute intracranial hematomas, where intermediate T1 and long T2 relaxation characteristics are reported.

Blood Flow Velocity↗
PubMed1986

Magnetic resonance imaging of spinal cord hemangioblastoma.

We retrospectively reviewed the magnetic resonance (MR) studies in nine patients with spinal cord hemangioblastoma. Five patients were studied with a low field magnet (0.35 T/0.5 T) and four with a high field magnet (1.5 T). Six tumors were thoracic and three cervical in location. Magnetic resonance imaging (MRI) was positive in all the nine patients. MRI permitted a specific diagnosis prior to angiographic evaluation of the cord in three patients. The most characteristic findings in such tumors were: an intramedullary vascular nodule, enlarged drainage vessels, diffuse enlargement of the cord, and/or intramedullary cyst. The high field magnet showed a greater sensitivity in detecting vascularity within the nodule and draining vessels than did the low field magnet. MRI should be the first procedure in patients with myelopathy and subarachnoid bleed of spinal origin and for screening patients with von Hippel-Lindau disease.

Adult↗
PubMed1985

Magnetic resonance imaging and characterization of normal and abnormal intracranial cerebrospinal fluid (CSF) spaces.

A retrospective review of twenty-five normal MRI brain studies performed with the spin-echo technique focused special attention on the ventricular and extraventricular cerebrospinal fluid (CSF) and revealed unique signal intensity characteristics in the two locations. In addition, MRI studies of ten patients with abnormal extraaxial fluid collections either missed with CT or indistinguishable from CSF on CT images were also analyzed. MRI is more sensitive when compared to CT in evaluating the composition of CSF. Unique signal intensity characterizes the two major CSF compartments and presumably reflects their known but subtle difference in protein concentration (10-15 mg%). Normal variant or abnormal developmental fluid collections can be better characterized with MRI than with CT. These preliminary observations are offered in view of their implications for patient management and suggest further investigation.

Brain↗
PubMed1985

Magnetic resonance imaging of primary intracranial tumors: a review.

The experience in magnetic resonance (MR) imaging of primary intracranial neoplasia at University of California, San Francisco is reviewed. Seventy patients have been evaluated by MR and computerized tomography (CT). MR scans were performed using a multi-slice spin echo technique with a long pulse repetition time (TR = 2000 msec), and long echo sampling delay (TE = 56 msec). This method was most sensitive in differentiating normal gray and white matter and in detecting both cerebral edema and abnormal tissue with prolonged T2 characteristics. More sensitive to slight alterations in normal tissue, MR may detect a focal lesion in cases in which CT shows only mass effect. Moreover, MR may demonstrate more thoroughly the extent of tumor infiltration and broaden the characterization of abnormal tissue. Posterior fossa and brainstem anatomy are invariably better depicted by MR. The major limitations of MR include its inability to detect foci of tumor calcification, demonstrate the severity of bone destruction, or reliably distinguish tumor nidus from surrounding edema.

Astrocytoma↗
PubMed1985

Magnetic resonance scanning in orbital tumor diagnosis.

We have compared the accuracy of magnetic resonance scanning (MRI) versus computed tomography (CT) in the differentiation of lateral orbital masses. The MRI results did not improve our ability to accurately diagnose malignant epithelial and lymphoid tumors.

Adolescent↗
PubMed1985

Efficacy of ciprofloxacin in experimental arthritis caused by Escherichia coli--in vitro-in vivo correlations.

Ciprofloxacin, a new carboxyquinolone, has potent in vitro bactericidal activity against the major aerobic, gram-negative bacillary pathogens that cause human pyoarthroses. We investigated the in vivo efficacy of ciprofloxacin in a rabbit model of septic arthritis due to Escherichia coli. Animals received either ciprofloxacin (80 mg/kg per day) or gentamicin (5 mg/kg per day). Ciprofloxacin was rapidly bactericidal in vivo and was significantly more effective in reducing the numbers of E. coli in synovial tissue than was gentamicin at days 10 and 17 of therapy (P less than .0005 and P less than .05, respectively). Similarly, ciprofloxacin was significantly more active than was gentamicin in reducing the numbers of E. coli in joint fluid on day 10 of therapy (P less than .0005); however, by day 17 of therapy, the numbers of E. coli in joint fluid were not significantly different in the two therapy groups. Neither regimen was effective in preventing the development of postinfectious inflammatory synovitis. There was no in vivo development of resistance to either antibiotic during therapy. Ciprofloxacin therapy was associated with significantly higher bactericidal titers in serum and joint fluid than were observed with gentamicin therapy (P less than .0005). Ciprofloxacin warrants further in vivo evaluation in invasive E. coli infections.

Animals↗
PubMed1985

Efficacy of amikacin and ceftazidime in experimental aortic valve endocarditis due to Pseudomonas aeruginosa.

The in vivo efficacies of amikacin, ceftazidime, and their combination were evaluated in experimental aortic valve endocarditis due to Pseudomonas aeruginosa. Eighty catheterized rabbits were infected with a P. aeruginosa strain susceptible to both amikacin and ceftazidime and then received no therapy (controls), amikacin (15 mg/kg per day), ceftazidime (100 mg/kg per day), or amikacin-ceftazidime. Amikacin-ceftazidime significantly lowered vegetation titers of P. aeruginosa at day 7 of therapy versus other regimens (P less than 0.0005). However, by day 14 of therapy, vegetation titers in animals receiving amikacin or ceftazidime regimens or both were not different from those of untreated controls; this was associated with in vivo development of amikacin resistance in most infected vegetations (79%), a phenomenon not seen at day 7 of therapy. Amikacin resistance was unstable in vivo, being undetectable in vegetations examined 5 days after treatment with amikacin had been completed. In contrast, ceftazidime resistance (first noted at day 7 of therapy in 12% of vegetations) persisted after termination of treatment with this agent. These in vivo observations on loss of amikacin resistance and persistence of ceftazidime resistance were mirrored during in vitro passage studies of amikacin- or ceftazidime-resistant P. aeruginosa strains isolated from cardiac vegetations. Amikacin resistance was no longer detectable by passage 5 in antibiotic-free media; however, ceftazidime resistance was stable despite 15 such passages. In vivo development of aminoglycoside-beta-lactam resistances was associated with poor bacteriologic efficacy in this model.

Amikacin↗