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Primary malignant rhabdoid tumor (PMRT) of the brain is a rare and recently described neoplasm of youth. We report magnetic resonance imaging (MRI), computed tomography (CT), and pathology of one case of PMRT in an adult which seeded along the needle track for stereotactic biopsy.

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A historical cohort study was carried out to evaluate the effects in utero medical ionizing radiation on head circumference at birth. The nature of medical practice in Rochester, Minnesota, and the Mayo Clinic medical records linkage system enabled us to provide accurate estimates of medical radiation absorbed dose in 9,793 pregnancies of 2,980 women pregnant in Rochester between 1917 through 1973. Data were controlled for sex of the fetus, duration of pregnancy and congenital head abnormalities. It was found that medical ionizing radiation in the second and third trimesters of more than 300 mrad were related to significantly decreased head circumference. There was no significant effect of radiation exposure in the first trimester or periconceptional period. Medical ionizing radiation in the second and third trimesters of more than 300 mrad is related to a significant yet minimal, decreasing head circumference at birth. Maximum effects were seen during the midgestational and second trimester periods.

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The administration of oral contrast (OC) is widely recommended for computed tomography (CT) of the abdomen in patients with blunt trauma. The purpose of this study was to determine whether routine abdominal CT scans performed without OC were associated with diagnostic error in patients with blunt trauma. Four hundred ninety-two patients were identified from our Trauma Registry who had CT scans for the evaluation of blunt abdominal trauma between January 1988 and December 1991. Seventy-six percent (372) of the CT scans were interpreted as negative, and 24% (120) were considered positive. OC was used in 8 (1.6%) of 492 patients. Only 1 of 372 patients whose initial non-OC--enhanced scan was negative subsequently required surgery. There were 5 bowel injuries among the 42 patients who underwent an abdominal operation; in none would the use of OC have ensured the preoperative diagnosis. We found that the omission of OC did not represent a disadvantage to patients with blunt trauma undergoing a routine abdominal CT scan. Potential time delays and the hazards associated with the use of OC were minimized.

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Acute ipsilateral pulmonary edema following reexpansion of the lung after pleurocentesis or pneumothorax is a well described entity. We report the unusual occurrence of bilateral pulmonary edema following unilateral pleurocentesis in a young male without heart disease. Various hypotheses regarding the mechanism of reexpansion pulmonary edema include increased capillary permeability due to hypoxic injury, decreased surfactant production, altered pulmonary perfusion and mechanical stretching of membranes. This case suggests that forces leading to ipsilateral reexpansion pulmonary edema also affect the contralateral lung.

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A new approach for producing primarily T2- and proton-density-weighted MR images in less time than the conventional long TR, long TE imaging is to reduce the TR of a double spin-echo pulse sequence and to also reduce the RF excitation flip angle to minimize the resulting T1 sensitivity. In preliminary studies with a human volunteer and five patients with various diseases of the head and neck, conventional long TR, long TE and short TR, short TE images were compared with short TR, long TE images with reduced flip angles (45 degrees, 30 degrees), which required only 40% of the imaging time of the long TR images. The latter images showed a similar contrast pattern to the conventional T2-weighted image, and contrast-to-noise measurements indicated an increase in contrast between the lesion and nearby tissue when the flip angle was reduced. Furthermore, the maximum contrast/noise per unit imaging time on the short TR, long TE image was comparable to that on the long TR, long TE image. Optimization of the flip angle with short TR allows a substantial reduction in imaging time but with a reduction in multislice capability. This technique will be most useful in areas of complex anatomy where two or more orthogonal imaging planes are required, such as the head and neck.

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To estimate fetal absorbed dose from radiographic examinations, the depth from the anterior maternal surface to the midline of the fetal skull and abdomen was measured by ultrasound in 97 pregnant women. The relationships between fetal depth, fetal presentation, and maternal parameters of height, weight, anteroposterior (AP) thickness, gestational age, placental location, and bladder volume were analyzed. Maternal AP thickness (MAP) can be estimated from gestational age, maternal height, and maternal weight. Fetal midskull and abdominal depths were nearly equal. Fetal depth normalized to MAP was independent or nearly independent of maternal parameters and fetal presentation. These data enable a reasonable estimation of absorbed dose to fetal brain, abdomen, and whole body.

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Seventy-two amniocenteses with concurrent placental grading by ultrasound were performed during 66 pregnancies. No relationship was observed between placental grade and the mean ratio of lecithin to sphingomyelin (L/S) or the phosphatidylglycerol concentration. Both placental grade and fetal lung maturity were interrelated by the independent variable of gestational age. The latter may explain the trend observed between a mature L/S ratio and the placental grade. Grade 3 placentas were present in only 20% of patients studied at 37 weeks of gestation or later (12 of 61 patients), and in every instance a Grade 3 placenta was associated with an absence of neonatal respiratory distress.

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Although ultrasonically detectable placental changes have been correlated with fetal maturity, the relative incidence of each placental grade at various gestational ages has not been known. During a one-year study period, placental grading was evaluated in 1709 scans performed at 27 weeks' gestation or after. At 40 weeks' gestation or beyond, only about 20% of placentas had extensive calcification (Grannum grade 3). Significant placental calcification was rarely seen before 37 weeks' gestation. Placental grading could not be used to predict postmaturity. The incidence of fetal distress in labor was found to be increased with postmaturity as well as with other pregnancy complications that give rise to premature placental senescence, rather than with grade 3 placentas per se.

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