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Biomedical subjects

D Norman

Publications and source records attributed to D Norman.

At least 217 records · Page 12Linked to original sources
PubMed1984

Magnetic resonance of the brain: the optimal screening technique.

Seventy consecutive patients were examined with magnetic resonance (MR) and computed tomography (CT) of the brain. Each study was independently reviewed. Focal abnormalities were detected by one or both modalities in 51 patients. Neoplastic, infectious, vascular, demyelinating, metabolic, and congenital disorders of the brain were included. The MR pulse sequence that best detected these abnormalities was a spin-echo multisection technique that used a long interval between RF excitations (TR = 1500 or 2000 msec). Forty-eight of 51 patients showed focal lesions with this technique. A supplementary MR pulse sequence with a short TR (500 msec) was useful in helping to characterize certain lesions with a long T1 relaxation component, but in 10 of 26 positive cases in which this sequence was added it would have missed the abnormality had it been the sole sequence used. MR missed focal lesions in 3 of 51 patients. These were lesions that required thin-section (1.5 mm) CT techniques. Two were intrasellar, and one was an intracanalicular neurinoma. In 17 of 48 patients, CT missed the focal lesion seen with MR. Based on this experience, it is concluded that the long TR multisection spin-echo sequence is the optimal MR screening technique for detection of most brain abnormalities, and is more sensitive than CT. Currently, CT remains the screening modality of choice when high-resolution, thin-section studies in the pituitary, inner ear, and orbital regions are indicated.

Brain Diseases↗
PubMed1984

Intraventricular mass lesions.

Determining the precise etiology of an intraventricular mass can be a difficult diagnostic problem. CT and angiographic findings were reviewed in a series of 73 patients who had intraventricular masses. The histologic diagnosis can be suggested preoperatively by an analysis of the frequency of lesions occurring at a given ventricular location, lesion density before and after administration of contrast material, age and sex of the patient, morphologic appearance of the mass, and presence or absence of hydrocephalus. Angiography is useful when meningioma, choroid plexus papilloma and carcinoma, or arteriovenous malformation are considered. The differential features of each diagnostic entity are discussed.

Brain Diseases↗
PubMed1984

Beam attenuation devices for digital subtraction angiography.

A set of three contoured and beveled aluminum filters was constructed for routine use in a variety of digital subtraction angiography (DSA) applications. These adjustable devices are designed to compensate for the uneven x-ray penetration that occurs in many radiographic fields and may otherwise lead to video camera saturation, a major source of artifact in DSA. We have used this simple yet versatile adjunct in more than 200 DSA examinations with uniformly satisfactory results. Major advantages include elimination of the procedural delays that may be associated with more conventional approaches (such as the use of a bolus technique) and avoidance of misregistration artifact when pixel-shifting is used.

Angiography↗
PubMed1984

Nuclear magnetic resonance: principles of blood flow imaging.

Nuclear magnetic resonance (NMR) imaging with spin-echo techniques defines vascular structures with superb anatomic detail. Contrast agents are not necessary as there is intrinsic contrast between flowing blood and the vascular wall. The signal intensity from blood within the vessel lumen varies with the sequence of gradient and radiofrequency pulses used to generate the image as well as with the velocity of blood flow. Appropriate imaging techniques can optimize anatomic detail, distinguish slow from rapidly flowing blood, and serve to identify marked impairment or complete obstruction of flow in an artery or vein. Some examples of these principles in the intracranial circulation are illustrated.

Adolescent↗
PubMed1984

ECG-synchronized DSA exposure control: improved cervicothoracic image quality.

An electrocardiogram (ECG)-synchronized x-ray exposure sequence was used to acquire digital subtraction angiographic (DSA) images during 13 arterial injection studies of the aortic arch or carotid bifurcations. These "gated" images were compared with matched "ungated" DSA images acquired using the same technical factors, contrast material volume, and patient positioning. Subjective assessments by five experienced observers of edge definition, vessel conspicuousness, and overall diagnostic quality showed overall preference for one of the two acquisition methods in 69% of cases studied. Of these, the ECG-synchronized exposure series were rated superior in 76%. Linear intensity gradients across vessel margins generally showed improved or unchanged edge definition in the gated subtraction images as compared with their ungated pairs. These results, as well as the relatively simple and inexpensive modifications required, suggest that routine use of ECG exposure control can facilitate improved arterial DSA evaluations of suspected cervicothoracic vascular disease.

Adult↗
PubMed1984

Computerized tomography of cranial sutures. Part 1: Comparison of suture anatomy in children and adults.

Knowledge of normal suture anatomy and development is vital in order to understand abnormal suture development and to be able to distinguish sutures radiographically from normal anatomical structures and possible skull fractures. The anatomy of the sutures and synchondroses of 150 normal pediatric and adult patients was studied using high-resolution computerized tomography scanning. Sutures of both the calvaria and skull base were most accurately identified in axial and coronal high-resolution thin-section scans when bone window algorithms were used. Developmental changes of the sutures and synchodroses , the inner and outer tables, and the diploic space were all well delineated. Vault sutures could be identified routinely in children, but their presence in adults varied considerably. With increasing age, parasutural sclerosis developed and sutures were more closely apposed.

Adolescent↗
PubMed1984

Computerized tomography of cranial sutures. Part 2: Abnormalities of sutures and skull deformity in craniosynostosis.

Preoperative computerized tomographic (CT) scans of 24 children who had surgery for either single or multiple craniosynostoses were compared with skull radiographs and operative and pathological findings. In addition to providing accurate imaging of calvarial and skull base deformities secondary to premature suture closure, high-resolution CT with bone definition algorithms supplied valuable detail of anatomical changes at the abnormally developed suture. The CT findings varied with the location of the suture. Thickened bony ridges predominated at the sagittal suture, focal bone thickening and erosions were more likely to be found at the metopic suture, and parasutural sclerosis was the prevalent finding on one side of the lambdoid suture. No evidence of the suture could be detected in the majority of patients with complete coronal craniosynostosis. Radiographs of the skull were shown to be a relatively insensitive means of imaging the zone of limited fusion, especially the lambdoid suture. An excellent correlation was found between the CT scan and the operative and pathological findings. There was histological evidence of progressive suture fusion in virtually all patients. An asymmetrically narrowed lucent zone with parasutural sclerosis or bony ridges seen on CT scans correlated well with fibrous union of the suture found on histological examination. The authors conclude that high-definition CT used in conjunction with bone windows and thin and coronal slices for the evaluation of sagittal sutures is a useful imaging method for the evaluation of craniosynostosis.

Cranial Sutures↗
PubMed1983

Computed tomography in acute disseminated encephalomyelitis.

Computed tomographic (CT) scans were obtained for eleven patients with acute disseminated encephalomyelitis (ADE). Four patients had normal CT scans despite repeated examination. Abnormalities were found in seven patients and included cortical-enhancing lesions, low-density lesions in the deep white matter and basal ganglia, and edema of the brainstem. These findings support the hypothesis that both vascular injury and demyelination are involved in the pathogenesis of ADE. A delay between the onset of clinical signs and the appearance of lesions on CT scan was common. Clinical improvement was accompanied by improvement in CT abnormalities. There was a limited correlation between the clinical course and the anatomical distribution and type of abnormality seen on CT scan.

Acute Disease↗
PubMed1983

Nuclear magnetic resonance imaging in multiple sclerosis.

Ten patients with definite multiple sclerosis underwent hydrogen nuclear magnetic resonance imaging with a 3.5 kilogauss superconducting magnet, using the inversion recovery and spin-echo techniques of signal acquisition. Results were compared with high-resolution x-ray computed tomography. Spin-echo images demonstrated abnormal regions as areas of variably increased signal intensity. The contrast between abnormal and normal white matter improved as the intervals between sequential radiofrequency pulses and between pulse administration and signal sampling were increased. Inversion recovery images demonstrated abnormal areas as regions of decreased signal intensity but did not visualize lesions as well as spin-echo imaging. Spin-echo and inversion recovery imaging each demonstrated more extensive abnormalities than did computed tomography.

Adult↗
PubMed1983

Carotid-cavernous fistula: closure with detachable silicone balloons.

Detachable silicone rubber balloons, which do not require an outer catheter to effect detachment, were used to close carotid-cavernous fistulas in 10 patients. Closure was effective in nine of 10 patients. The internal carotid artery was intentionally occluded in two patients. The procedure resulted in inadvertent occlusion of the internal carotid artery in three patients. Follow-up studies showed no recurrence of the fistula; nor did any permanent neurologic deficits develop as a result of the procedure. The balloon catheter system and techniques of introduction are discussed in detail. The system is compared with other silicone and latex balloon systems that require a coaxial catheter for detachment. Technical and clinical problems are illustrated.

Adolescent↗
PubMed1983

Digital subtraction cerebral angiography by intraarterial injection: comparison with conventional angiography.

For 4 months, a prototype digital subtraction system was used to obtain images of the cerebral vasculature after intraarterial contrast injections. In 12 instances, the intraarterial injections were recorded with both a digital subtraction unit and conventional direct magnification film-screen system. The digital subtraction and conventional film subtraction images were compared and graded for quality and information content by three skilled observers. In addition, quantitative measurements of contrast-detail performance and spatial resolution were obtained on both the digital system and the screen-film imaging chain. In a clinical setting, both the digital subtraction and conventional film-screen systems provided similar quality images and angiographic information. Contrast-detail curves demonstrated that digital subtraction angiography outperformed conventional film technique for low-contrast objects. Digital subtraction angiography also reduced the time required to obtain the angiogram, markedly reduced film cost, and lowered the contrast agent burden.

Adolescent↗
PubMed1983

Economic impact of CT scanning on the evaluation of pituitary adenomas.

The medical and financial records of three cohorts of 20 consecutive patients with pituitary adenomas surgically treated in 1976, 1978, and 1980 were evaluated to assess the impact of changing technology on the cost of preoperative diagnostic evaluation. The average preoperative length of hospital stay decreased from 6.8 days in 1976 to 1.9 days in 1980. The average diagnostic radiologic charge adjusted to 1980 dollars decreased from +1,747 in 1976 to +585 in 1980, while the radiologic bill as a percentage of the total hospital bill changed from 17.3% in 1976 to 11.9% in 1980. The decline in cost parameters coincided with the dramatic increase in the use of cranial computed tomography and the sharp reduction in the use of angiography and pneumoencephalography. These findings suggest that computed tomography is a highly efficacious technique for the evaluation of patients with suspected pituitary adenoma, resulting in significant savings in the costs of diagnostic evaluation.

Adenoma↗
PubMed1983

NMR demonstration of cerebral abnormalities: comparison with CT.

Sixty-eight patients with a wide spectrum of brain pathology were imaged with both computed tomography (CT) using a G.E. 8800 scanner and nuclear magnetic resonance (NMR) imaging with a 3.5 kG prototype device. NMR was more advantageous in the detection and/or characterization of pathology in 20 of the 68 patients, especially when demyelination was part of the disease process or when the lesion was obscured on CT by beam-hardening artifact. Punctate foci of calcification identified on CT were not detected on NMR, but larger calcifications were seen. NMR was sensitive to detection of both normal and abnormal vascular structures. The ability of NMR to differentiate among different pathologic entities remains to be fully evaluated. NMR currently complements CT in the evaluation of many disease entities and may actually supplant CT in some. The full future potential of NMR and its role with respect to CT has only begun to be elucidated.

Adolescent↗
PubMed1983

Magnetic resonance imaging of the spinal cord and canal: potentials and limitations.

Preliminary experience with magnetic resonance imaging (MRI) of the spinal cord and canal in 17 patients indicates considerable promise in the diagnosis of neoplastic, degenerative, and congenital lesions. The ability to image the cord directly rather than indirectly as in myelography, the absence of bone artifact as in computed tomography, and the multiplanar capabilities indicate that MRI will be the procedure of choice in the examination of the spinal cord. Current limitations include partial-volume effects due to slice thickness and the inability to perform contiguous sections when using multiplanar techniques. The relative increase in signal from cerebrospinal fluid with long TR and TE sequences in spin-echo imaging may result in less sensitivity than in the brain for detection of cord edema and/or infarction.

Humans↗
PubMed1983

Computerized tomography of peripheral nerve lesions.

Nine patients with a peripheral nerve lesion (six intrinsic and three extrinsic) were evaluated with computerized tomography (CT). In all but one instance, the CT scans gave useful information regarding the anatomical location, size, and relationship of the lesion to surrounding structures. These cases illustrate the usefulness of CT as a diagnostic tool in the evaluation of peripheral nerve lesions.

Adult↗