Biomedical subjects
Publications and source records attributed to E L Effmann.
We report on a 20-week fetus with manifestations similar, but not identical, to those of atelosteogenesis. The present fetus had rhizomelic micromelia with absence of ossification in the humerus, radius, ulna, and cervical and upper thoracic vertebral bodies; coronal clefts in the ossified thoracic vertebral bodies; and talipes equinovarus. The physes were relatively normal on histologic examination.
Magnetic resonance imaging (MRI) of the live 11-day chick embryo with special radiofrequency coils and 3-D imaging methods has produced contiguous 1.25-mm-thick slices with 200-microns pixel resolution, permitting definition of cardiac chambers, cerebral ventricles, spinal cord, liver, and lungs. It was the objective of this study to image younger chick embryos in ovo with higher spatial resolution through the application of implanted radiofrequency coils. Fertilized Arbor Acre eggs were windowed at 9, 6, and 4 days. Circular coils 18 mm in diameter tuned to 85.5 MHz were suspended around the developing embryo. The eggs were sealed with tape and maintained at 37 degrees C during the imaging procedure. MRI was performed in a 2.0-Tesla GE system utilizing a 3-D Fourier transform acquisition in sagittal and axial planes with a partial saturation sequence (TR = 400 ms, TE = 27 ms). Approximately 1 hour of imaging time was required to obtain 16 contiguous 600-microns-thick slices with 50-microns pixel resolution. Embryos remained viable through the imaging procedure. Embryos were photographed, fixed, and cleared for correlative anatomical study. Vitelline vessels, dorsal aorta, aortic arches, cardinal veins, and cardiac chambers were identified as areas of decreased signal intensity. Cerebral ventricles and the vitreous portion of the eye have signal intensities that are less than adjacent neural, scleral, and lens tissue. Further refinements in MR instrumentation and imaging sequences promise improvements in resolution and offer the potential for sequential observations of the intact embryo.
Twenty-three pulmonary pseudocysts were identified in 20 preterm neonates undergoing mechanically assisted ventilation. Most of the pseudocysts occurred in a right parahilar location; cysts were either single (13) or multiple/multilocular (10). The pseudocysts persisted from less than 2 days to longer than 3 months (modal duration, 7 days), and they were commonly associated with generalized pulmonary interstitial emphysema (18 of 20), pneumothorax (18 of 20), bronchopulmonary dysplasia (16 of 20), and pneumomediastinum (six of 20). The reason for the predominantly right parahilar location of these pseudocysts remains uncertain. Pulmonary pseudocysts are almost always right-sided and are associated with pulmonary interstitial emphysema and pneumothoraces; complete resolution usually occurs.
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Pediatric radiologists have made numerous and important contributions to the body of medical knowledge. This essay reviews aspects of biomedical and radiological research, analyses the state of scholarship in pediatric radiology today, and examines future research opportunities. The author's research interest in cardiopulmonary malformations and in the use of murine models of human disease serve to illustrate of but one of many investigative areas open to academic pediatric radiologists. Finally, the application process for NIH funding is briefly discussed.
Origin of the right pulmonary artery from the aorta is a congenital malformation usually associated with serious symptoms in the first year of life and characterized by a poor prognosis. Sixty-five patients with this disorder have been reviewed in the literature, and 95% presented during the first year with signs of congestive heart failure. All had cardiomegaly by radiographic and electrocardiographic examination. An accurate diagnosis was established by cineangiography, and associated cardiovascular anomalies were present in 85%. Origin of the right pulmonary artery from the ascending aorta is much more common than origin of the left pulmonary artery from this vessel (8 to 1). Twenty-three patients were managed without operation with a 30% 1-year survival rate. Among those patients managed surgically, the survival rate was 84% at 1 year. It is now clear that operation should be done as early as possible to prevent irreversible changes occurring in the pulmonary arterial vasculature since microscopic features of pulmonary hypertension have been seen during the first month of life. One patient was operated on at 5 months with correction of the deformity. The pulmonary arterial pressure decreased to normal after operation. This child is now asymptomatic and his 10-year postoperative follow-up is the longest found in the literature.
To test the potential of 1.5 Tesla magnetic resonance imaging (MRI) for assessing the protein concentration of pleural effusions, five pleural fluid analogs (saline + 0, 2, 4, 6, 8 g albumin/100 mL) and, for comparison, four saline dilutions of whole blood were evaluated in vitro. The relaxation rates (1/T1, 1/T2) of albumin solutions were determined by 1.5 T spectroscopy (MRS) and correlated with albumin concentration (1/T1:slope 0.02, r + 0.89, P less than .05; 1/T2: slope 0.16, r = 0.997, P less than .001). MRI studies of these solutions showed no significant correlation with 1/T1, but 1/T2 showed a positive correlation with albumin concentration (r = 0.98, P less than .01). Both MRI relaxation rates were significantly correlated with blood concentration, and slopes were greater than for albumin solutions. These preliminary studies, demonstrating differences in correlation between relaxation rates and the concentration of albumin and blood, suggest that MRI has the potential for differentiating pleural effusions of different chemical composition.
The effects of patient age, anatomic level, anteroposterior location, and phase of respiration on pulmonary density were analyzed retrospectively in 33 children and prospectively in 13 children. Density standards were positioned on the chest wall for correction of scanner performance changes. The subgroup of 32 children over 7 years of age, ie, with respiratory cooperation, was analyzed separately using moderate inspiration; its mean lung density (MLD) of three levels was -792 HU (95% range, -702-882 HU). Although MLD decreased with increasing age, a significant linear regression was found only in the prospective subgroup. Densities of the apical, subcarinal, and basal levels of the lung were not different. From maximal expiration to maximal inspiration, MLD decreased by 158 HU in the subgroup studied prospectively. Anteroposterior density gradients averaged 56 HU at the subcarinal level and increased with maximal expiration.
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Vascular dysmorphogenesis is usually investigated by invasive microdissection or time-consuming reconstruction of serial sections. Stereomicroangiography (SMA) was used for detection and analysis of vascular abnormalities in a murine trisomy 13 model demonstrating pulmonary atresia. Twenty-two litters from doubly heterozygous Robertsonian translocation Rb(6.13)3Rma/Rb(5.13)70Lub male matings to NMRI females were studied. Embryos (13-17 days gestation) were prepared by umbilical vein perfusion with buffered fixative and umbilical artery perfusion with 5% AgNO3. After immersion fixation specimens were infiltrated with paraffin, mounted on stubs, and stereoradiographed at multiple angles. Transverse serial sections were prepared of the thoracic area. Thoracic vascular morphology was satisfactorily imaged and trisomy 13 embryos were correctly distinguished from normals in 105 of 120 embryos (87.5%). When independent SMA and histologic interpretations were compared anomalous vasculature was correctly identified in all 27 trisomic embryos and one control, and falsely interpreted in one normal embryo. Normal vascular morphology was demonstrated in the remaining 76 normal embryos. Separate SEM evaluation of five microdissected hearts from nontrisomic embryos following this perfusion schedule showed normal distension of the ventricular cavity and metallic silver deposition on the surface and at junctions of endocardial cells. Light microscopy revealed silver staining at the endothelial surface and within the endocardial cushions. SMA accurately records embryonic vascular morphology for rapid screening of viable embryos.
Breathing motion severely degrades the quality of magnetic resonance images (MRI) of the thorax and upper abdomen and interferes with the acquisition of quantitative data. To minimize these motion effects, we built an MRI compatible ventilator for use in animal studies. Solid state circuitry is used for controlling ventilation parameters. The ventilator can be triggered internally at frequencies of 0.1 to 30 Hz or it can be triggered externally such as by the MRI pulse sequence. When triggered by the scanner, ventilation is synchronized to occur between image data acquisitions. Thus, image data are obtained when there is no breathing motion and at a minimum lung volume when hydrogen density is maximum. Since the ventilator can be adjusted to operate at virtually any frequency from conventional to high frequency, ventilation can be synchronized to all commonly used repetition times (100 ms to 2000 ms or more; 600 to 30 breaths/min). Scan synchronous ventilation eliminates breathing motion artifacts from most imaging sequences (single and multiple spin echo and inversion recovery). Best image quality is obtained when scan synchronous ventilation is combined with cardiac gating. These methods are also useful for quantitative research studies of thoracic and abdominal organs.
Oleic acid infusion in dogs produces a patchy, predominantly peripheral lesion on CT scans. This study correlates the pattern of oleic acid injury with the distribution of infused oleic acid and pulmonary blood flow. Radiolabeled oleic acid (I-125, 0.05 ml/kg) and radiolabeled 15-micron microspheres (Co-57) were infused into the right atria of 11 dogs. Oleic acid was given after the microspheres in six dogs and before microspheres in five dogs. Ten minutes after infusion, the lungs were removed. Four transverse slices (0.5 cm thick) of the lower lobes were taken from each dog and cubed. Samples were grouped into three regions of the transverse slice: outer, middle, and inner concentric rings. In both groups, I-125 (oleic acid) activity was greater in the outer than the middle and inner concentric layers (P less than 0.001). When Cobalt-57 microspheres were given before oleic acid, Cobalt-57 activity was marginally lower in the outer layer compared with the middle and inner layers. However, when oleic acid was given first, microsphere activity in the outer layer was significantly lower (P less than 0.001) than the middle layer. Thus, oleic acid was preferentially distributed to the peripheral regions of the lung, similar to the regions of injury on CT. This distribution did not correspond to the pattern of pulmonary blood flow as indicated by the microspheres. Immediately after oleic acid infusion, pulmonary blood flow to the periphery was reduced, reflecting a response to the predominantly peripheral injury by oleic acid.
Stereomicroradiographic images of timed-gestation mouse embryos clarify aortic development and help one to understand human vascular anomalies.
The avian lung has been considered to be rigid and to remain isovolumetric during the respiratory cycle. We tested this hypothesis by implanting radiopaque markers of tantalum on the dorsal pulmonary surfaces and ventral pulmonary aponeuroses of Pekin ducks (Anas platyrhynchos) and measuring changes in lung thickness during the respiratory cycle using high speed cineradiography. We found small but regular changes in lung thickness that were synchronous with respiratory phase. Lung thickness was greatest at mid-inspiration (0.6% greater than mean) and least at mid-expiration (0.8% less than mean). Measurements made on ostrich (Struthio camelus) respiratory structures suggest that the maximal force that could be generated by the muscles (Mm. costopulmonales) at the margins of the ventral pulmonary aponeurosis is more than two orders of magnitude greater than would be required to resist pressure-induced changes in lung volume during respiration at rest. The action of these muscles could account for the very small magnitude of the volume changes measured during the respiratory cycle.
This article describes the use of computed tomography for the evaluation of pediatric patients with a variety of chest diseases. Indications for chest CT, constraints of technical factors on the study, and analysis of the benefits of CT examination versus risks will also be discussed.
Clinical, radiological, and pathologic data for nine children with adult respiratory distress syndrome (ARDS) were reviewed. The children ranged in age from 7 months to 15 years (mean age, 7.4 yrs). Underlying diseases and precipitating events included sepsis, pneumonia, near drowning, aspiration pneumonia, central nervous system trauma, and malignancy. All patients had the rapid onset of diffuse bilateral lung opacification, required assisted ventilation for periods of 5-86 days (mean, 25.2 days), and received high levels of inspired oxygen for 2-41 days (mean, 12.7 days). Eight patients manifested air leak complications; these problems persisted until the patients died or were weaned from the respirator. Five of the nine patients died. Autopsy in three patients demonstrated alveolar duct fibrosis characteristic of the late proliferative phase of ARDS and consistent with oxygen toxicity. Two survivors demonstrated mild restrictive changes on follow-up pulmonary function tests and showed persistent linear densities on chest radiographs.
After phantom validation of the method, normal tracheal morphology of 25 women and 25 men was studied retrospectively at level 1, the thoracic inlet; level 2, the supracarinal level, and level 3, halfway between. In no case was the minimal cross-sectional area less than 68% of the maximum of the three levels. Areas at the same level were different depending on sex, but not on other body parameters, and so were the means of the three levels: 194 mm2 (SD 35) in women and 272 mm2 (SD 33) in men. Mean tracheal area correlated with mean tracheal diameter (r = 0.98). Average configuration of the trachea was sagittal at the thoracic inlet and transverse supracarinally. Absolute tracheal cross sections of less than 120 mm2 in women and 190 mm2 in men and relative values of less than two-thirds compared with other levels should suggest an abnormality. Although static and not in competition with functional tests, noninvasive CT area calculation may be useful in demonstrating and quantifying tracheal obstruction when mediastinal neoplasms are staged or as a complementary morphological test when ventilatory studies do not afford enough information to localize the lesion and to decide about treatment.
A computer method that calculates tracheal cross-sectional area by compensating for partial volume averaging was developed and validated in a study with phantoms. The program was then used to determine the tracheal cross-sectional area of 30 normal children who ranged in age from four months to 18 years. CT-derived cross sections were correlated with age, height, weight, and body-surface area, and they were compared with findings of published clinical and post-mortem studies. CT cross-sectional areas ranged from 20-275 mm2, varied by as much as 22% at the three different tracheal levels studied, and appeared to correlate most closely with body height. CT-derived tracheal cross-sectional areas are quite similar to those in published reports of postmortem and clinical studies. Measurement of tracheal cross section by CT may prove useful in quantitating tracheal compromise by intrinsic or extrinsic causes.