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T M Simonson

Publications and source records attributed to T M Simonson.

27 records · Page 2Linked to original sources
PubMed1994

Contrast MR of the brain after high-perfusion cardiopulmonary bypass.

PURPOSE: To study the efficacy of contrast MR imaging in the evaluation of central nervous system complications in the cardiopulmonary bypass patient and attempt to explain their pathophysiology based on the MR appearance and the cardiopulmonary bypass protocol. METHOD: Nineteen patients were prospectively studied with contrast MR examinations the day before and 3 to 7 days after cardiopulmonary bypass, to determine the nature, extent, and number of new postoperative MR abnormalities. Cardiopulmonary bypass parameters used in our institution included: membrane oxygenation, arterial filtration with a pore size of 25 microns, and a relatively high perfusion rate to produce a cardiac index of 2.0 to 2.5 L/min per m2. RESULTS: The preoperative noncontrast MR examination showed age-related changes and/or signs of ischemia in 60% of patients on the day before surgery. However, there was no abnormal enhancement or new T2 abnormalities on any postoperative MR examination to suggest hypoperfusion or emboli. None of the 19 patients developed overt neurologic deficits postoperatively. Review of the cardiopulmonary bypass protocol used indicated significant variations in technique at different institutions. CONCLUSION: Contrast MR imaging demonstrated no new abnormalities in patients after cardiopulmonary bypass performed with strict in-line arterial filtration and relatively high perfusion. MR imaging is feasible in the early postoperative period after cardiopulmonary bypass and may offer a convenient method for evaluation of the neurologic impact of technical factors associated with cardiopulmonary bypass.

Adult↗
PubMed1994

Venous sinus occlusive disease: MR findings.

PURPOSE: To study MR patterns of venous sinus occlusive disease and to relate them to the underlying pathophysiology by comparing the appearance and pathophysiologic features of venous sinus occlusive disease with those of arterial ischemic disease. METHODS: The clinical data and MR examinations of 26 patients with venous sinus occlusive disease were retrospectively reviewed with special attention to mass effect, hemorrhage, and T2-weighted image abnormalities as well as to abnormal parenchymal, venous, or arterial enhancement after intravenous gadopentetate dimeglumine administration. Follow-up studies when available were evaluated for atrophy, infarction, chronic mass effect, and hemorrhage. RESULTS: Mass effect was present in 25 of 26 patients. Eleven of the 26 had mass effect without abnormal signal on T2-weighted images. Fifteen patients had abnormal signal on T2-weighted images, but this was much less extensive than the degree of brain swelling in all cases. No patient showed abnormal parenchymal or arterial enhancement. Abnormal venous enhancement was seen in 10 of 13 patients who had contrast-enhanced studies. Intraparenchymal hemorrhage was seen in nine patients with high signal on T2-weighted images predominantly peripheral to the hematoma in eight. Three overall MR patterns were observed in acute sinus thrombosis: 1) mass effect without associated abnormal signal on T2-weighted images, 2) mass effect with associated abnormal signal on T2-weighted images and/or ventricular dilatation that may be reversible, and 3) intraparenchymal hematoma with surrounding edema. CONCLUSION: MR findings of venous sinus occlusive disease are different from those of arterial ischemia and may reflect different underlying pathophysiology. In venous sinus occlusive disease, the breakdown of the blood-brain barrier (vasogenic edema and abnormal parenchymal enhancement) does not always occur, and brain swelling can persist up to 2 years with or without abnormal signal on T2-weighted images. Abnormal signal on T2-weighted images may be reversible and does not always indicate infarction.

Adolescent↗
PubMed1994

MR of fetal central nervous system abnormalities.

PURPOSE: To investigate whether MR can provide additional information on fetuses with central nervous system abnormalities as demonstrated by ultrasonography. METHODS: Fetal MR examinations were studied prospectively in 22 pregnant women whose fetuses showed evidence of anomalies on ultrasound performed in the High-Risk Obstetric Clinic. RESULTS: In 19 of 22 cases, postpartum confirmatory diagnoses were obtained by MR or CT examinations, autopsy, or surgery. In general, the image quality of MR is comparable with that of ultrasound. However, in six of 22 cases (27%), MR provided additional information that altered the ultrasound diagnosis; these included cases of infarction, diastematomyelia, normal hemimegalencephaly with early myelination, Dandy-Walker variant, and lipoma. All of these cases had postpartum confirmation. The additional information changed the treatment in three of six patients (no intervention or elective abortion). CONCLUSIONS: In certain situations MR can add valuable information to that obtained by sonography in the evaluation of the fetal central nervous system.

Central Nervous System↗
PubMed1992

MR imaging of the pituitary gland in central precocious puberty.

Cranial magnetic resonance imaging was performed in 17 children with central precocious puberty (CPP) and 19 aged-matched controls to compare the appearance of the pituitary gland. Gland size was measured on T1-weighted sagittal and coronal images. The gland was graded according to the concavity or convexity of the upper surface, and the signal intensity of the gland was assessed visually. The mean pituitary volume in 13 CPP children without hypothalamic tumor (292.6 mm3) was significantly greater than that in normal controls (181.35 mm3). The mean volume for the four CPP children with hypothalamic tumor was smaller (145.0 mm3). Compared to controls, the upper pituitary surface in CPP patients appeared convex in a higher proportion. The anterior pituitary was isointense to pons in all patients and controls. Although the posterior pituitary bright spot was present in 14 controls and 11 CPP patients, none with hypothalamic tumor showed it.

Astrocytoma↗
PubMed1992

Normal childhood developmental patterns in skull bone marrow by MR imaging.

To establish the normal developmental pattern of skull bone marrow in children by MR imaging, sagittal T1-weighted MR skull images of 324 normal children (newborn to 18 years) were reviewed. Bone marrow intensity was assigned four gradations as compared with that of muscle and fat on the same image. Bone marrow became isointense with fat (yellow marrow) at a mean age +/- S.E.M. (in years) of 8.5 +/- 0.24 in sphenoid, 9.1 +/- 0.29 in mandible, 9.3 +/- 0.28 in hard palate, 9.7 +/- 0.26 in frontal, 11.0 +/- 0.26 in squamous occiput, 11.5 +/- 0.28 in parietal, and 11.9 +/- 0.24 in basiocciput. There is a strong correlation between age and marrow intensity by Spearman analysis (p < 0.001): hard palate 0.64, mandible 0.61, parietal 0.42, sphenoid 0.70, cervical spine 0.50, basi-occiput 0.58 and occiput 0.52. Two consistent overall patterns of red-yellow marrow conversion were observed. Bone marrow became isointense with fat prior to pneumatization of the paranasal sinuses. Marrow conversion in the bones of the face occurred before those of the calvarium in a specific pattern. There was no significant sex difference in the pattern or rate of marrow conversion. These normative data are necessary to evaluate the immature skull by MR imaging in disease states.

Adolescent↗
PubMed1992

MR imaging and HMPAO scintigraphy in conjunction with balloon test occlusion: value in predicting sequelae after permanent carotid occlusion.

OBJECTIVE: Permanent occlusion of the internal carotid artery may be required for en bloc resection of a neck tumor or to treat certain aneurysms. The risk of ischemic infarct is usually assessed with carotid balloon test occlusion and concurrent distal arterial pressure measurement. However, up to 20% of patients who tolerate the test occlusion have delayed neurologic sequelae. We propose enhanced MR imaging and hexamethylpropyleneamine oxime (HMPAO) scintigraphy to detect subclinical signs of ischemia and hypoperfusion as adjuncts to the balloon test occlusion to identify patients at risk for delayed sequelae. SUBJECTS AND METHODS: We prospectively examined 12 patients referred for balloon test occlusion of the carotid artery. Serial measurements of distal occluded internal carotid pressure were recorded. 99mTc-HMPAO was injected IV after 2 min of asymptomatic test occlusion, and single-photon emission computed tomographic (SPECT) data acquisition was done 1-6 hr later. Contrast-enhanced MR imaging was performed 1-8 hr after completion of the 30-min test occlusion. Signs of decreased perfusion or ischemia on these tests were compared with the mean distal arterial pressure and neurologic status of the patient during test occlusion. RESULTS: Seven (58%) of 12 patients had abnormal findings on HMPAO scintigraphy or contrast-enhanced MR imaging. Only one patient had neurologic deficits that corresponded to abnormal MR enhancement. The other 11 patients (92%) remained asymptomatic during the 30-min test occlusion. Of these 11 asymptomatic patients, five (45%) had areas of decreased perfusion on scintigraphy and three (27%) had abnormal MR contrast enhancement suggesting residual focal ischemia as a result of the test occlusion. Mean arterial pressures in the distal occluded artery did not correlate well with the imaging results. CONCLUSION: HMPAO scintigraphy can show clinically silent areas of decreased perfusion, while enhanced MR shows signs of acute ischemia (i.e., significant hypoperfusion) associated with asymptomatic balloon test occlusion. Theoretically, such patients would be at increased risk for permanent sequelae after permanent carotid occlusion.

Adult↗
PubMedDate not supplied

MR imaging of ventriculomegaly--a qualitative and quantitative comparison of communicating hydrocephalus, central atrophy, and normal studies.

Both communicating hydrocephalus and central atrophy cause ventricular dilatation. However, patients with hydrocephalus may require treatment. The aim of this study was to assess qualitatively and quantitatively the efficacy of MR imaging in the differentiation of communicating hydrocephalus from central atrophy. The midsagittal T1-weighted MR images of 33 patients with communicating hydrocephalus, 31 patients with central atrophy, and 23 normal subjects were evaluated qualitatively and quantitatively. This included configuration of the aqueduct; area of the septum pellucidum, third ventricle, and fourth ventricle; and morphology of the corpus callosum. Distal dilatation of the aqueduct was detected in 33.3% of patients with communicating hydrocephalus and in none of those with central atrophy. The corpus callosum was elevated in patients with communicating hydrocephalus when compared with that in patients with central atrophy. In conclusion, an analysis of midsagittal T1-weighted images has identified useful qualitative and quantitative criteria in the differentiation of communicating hydrocephalus from central atrophy. The configuration of the aqueduct with funneling at the fourth ventricular end strongly suggests the presence of communicating hydrocephalus rather than central atrophy alone.

Aged↗
PubMedDate not supplied

MR evaluation of acoustic schwannoma with fractional contrast doses.

OBJECTIVE: To investigate the utility of lower contrast medium doses for the detection and conspicuity of acoustic schwannomas. MATERIALS AND METHODS: The L/B (L, lesion; B, background) ratios or lesion contrast of 17 pathologically proven acoustic schwannomas studied with a standard dose (0.1 mmol/kg) of gadopentetate dimeglumine was measured. In addition, 22 patients with acoustic schwannomas were studied prospectively with fractional doses using the incremental dose technique. Each patient received an initial bolus injection of one-eight the standard dose (0.0125 mmol/kg) followed by an injection of one-eighth, one-fourth, and one-half the standard dose at 5 min intervals to achieve a cumulative dose of one-fourth, one-half and full dose, respectively. Imaging was performed immediately after each injection. RESULTS: Standard dose--The L/B ratios of pathologically proven acoustic schwannomas to mastoid air cells ranged from 14.8 to 41.2 (mean +/- SEM, 28.0 +/- 1.95), which were approximately 17 times more than those of intraparenchymal lesions. Fractional cumulative dose--Qualitative visual analysis demonstrated that all acoustic schwannomas showed apparent enhancement at one-fourth dose. Intense enhancement was noted at one-half and full dose. Quantitative analysis demonstrated the mean L/B ratios between the acoustic schwannomas and mastoid air cells of the precontrast and one-eighth, one-fourth, one-half, and full dose studies were 8.33 +/- 0.52, 11.21 +/- 0.75, 13.02 +/- 0.83, 15.38 +/- 0.98, and 18.03 +/- 1.36, respectively. CONCLUSION: The L/B ratios or lesion contrast of acoustic schwannomas at various fractional contrast medium doses was significantly higher compared with that of intraparenchymal lesions. Thus, the standard contrast medium dose may not be necessary for detection of acoustic schwannomas, and a fractional dose may be sufficient. Although the optimal fractional dose remains to be determined, one-half of the standard dose (0.05 mmol/kg) appears to be sufficient because of intense enhancement at this dose.

Contrast Media↗