Eric L. Effmann

Disappearing fetal lung masses: importance of postnatal imaging studies

Background. The “disappearance” of congenital masses of the lung on prenatal sonograms has been described, but the importance of postnatal imaging studies in these children is unknown. Objective. The objective of this work was to study the utility of radiographs and CT scans in asymptomatic infants with congenital masses of the lung that partially or completely resolve on prenatal sonograms performed late in gestation. Materials and methods. The prenatal sonograms, postnatal imaging studies, surgical findings, and pathologic diagnoses of seven children with an echogenic mass of the lung that improved or disappeared on prenatal sonograms were reviewed. Results. All masses were type II congenital cystic adenomatoid malformation, with features of intralobar sequestration also being found in four. An unsuspected extralobar sequestration adjacent to a left lower lobe mass was found at surgery in one patient. All masses were hyperechoic compared with normal lung on sonograms prior to 32 weeks of gestation, with cysts being seen in four. On scans after 32 weeks, four of the masses had resolved completely and three showed subtle increased echogenicity compared with normal lung. Cysts completely resolved in two of four cases. Postnatal radiographs showed subtle abnormalities in four infants, a hyperlucent lobe in one, a soft tissue mass with adjacent hyperlucency in one, and normal findings in one. CT scans were abnormal in all cases, with air-filled cysts and soft tissue in six and a hyperinflated lobe in one. Conclusion. Children with “disappearing” fetal lung masses have persistent abnormalities after birth that are often subtle on radiographs but are well demonstrated with CT.

Lung volume changes during respiration in ducks

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.

CT assessment of the adult intrathoracic cross section of the trachea.

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 ventilator for magnetic resonance imaging.

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.

Origin of the right pulmonary artery from the ascending aorta.

A case of aortic origin of the right pulmonary artery has been presented. A venous cineangiocardiogram demonstrated filling of the left side of the heart from the right atrium with subsequent opacification of the aorta and the anomalous right pulmonary artery without initial opacification of the right ventricle and main plus left pulmonary artery. At necropsy there was a fibrous band connecting the main pulmonary artery with the anomalous vessel. The embryologic implications suggest that this case represents atresia of the proximal portion of the right sixth aortic arch.

Hydrostatic pulmonary edema an analysis of lung density changes by computed tomography

The computed tomographic (CT) appearance of pulmonary edema induced by elevated left atrial (LA) pressure was examined. Dogs, in the prone position, were scanned during suspended ventilation at functional residual capacity. A surgically implanted LA balloon was inflated to elevate LA pressure for 30 to 140 minutes to a mean pressure of 29.8 mm Hg. Lung water, measured gravimetrically, averaged 14.7 ml/kg body weight compared with 5.7 ml/kg in nonedema control dogs. Lung density in dogs with edema was 69.5% higher than base-line density, while in the control group final lung density was only 4% higher than base line. Analysis of regional density indicated that there were greater increases in density in more central and dependent (ventral) zones of the lung and relatively smaller increases in nondependent (dorsal) peripheral zones. These results are in contrast to the previously reported pattern of density change seen with oleic acid injury in which density increases were primarily in peripheral zones of the lung.

Pulmonary edema: a CT study of regional changes in lung density following oleic acid injury.

Transmission computed tomography (CT) was used to study the global and regional density changes in the dog lung associated with oleic acid induced lung injury. The same level of the lower thorax was scanned (5 s scan) during suspended ventilation at functional residual capacity prior to and after oleic acid infusion (0.05 ml kg) into the right atrium. The first signs of edema were usually seen within 15 to 30 min after oleic acid infusion and consisted of patchy areas of increased density primarily in the peripheral and dependent /ones. Mean CT density (Hounsfield units t 1.000) of lung cross sections from five dogs was 198 ± 9 (SUM) during base line: density significantly (p 0.05) increased to 24.3 ± 14 30 min after infusion and reached an apparent plateau of 294 ± 31 75 min after oleic acid infusion. Thermal-dye dilution measurements indicated that extravascular lung water increased by 3.8 ml kg from base line to 75 min after oleic acid infusion.

Control of air flow in bird lungs: Radiographic studies

The complex pattern of air flow in the respiratory system of birds suggests that certain sites function as valves. To examine the possibility of mechanical valving, rather than aerodynamic valving, we recorded radiographic images of the orifices where the medioventral secondary bronchi branch from the primary bronchus in resting Pekin ducks. Analysis of the images indicated that the orifices do not change size or shape during the respiratory cycle, suggesting that they function as aerodynamic rather than mechanical valves in directing air flow through the lung.

Morphology of oleic acid-induced lung injury observations from computed tomography, specimen radiography, and histology

Previously, we reported that oleic acid infusion in dogs produced a patchy and predominantly peripheral increase in lung density. The present study examines in more detail the morphology of the early stages of development of the oleic acid lesion using computed tomography (CT), specimen radiography, and conventional histology. Dogs were sacrificed 10, 30, 60, and 240 minutes after infusion of oleic acid (.05 ml/kg). After freezing in dry-ice, the thorax was scanned and cut into 1-cm thick sections. Frozen sections were then contact radiographed and sampled for histology. Within 10 minutes of infusion, subtle increases in peripheral lung density were visible on the contact radiographs. Patchy areas of peripheral density, resembling secondary lobules, were especially prominent 60 and 240 minutes after infusion. These lesions were often clearly associated with the distal bronchovascular structures. Histologic signs of edema were present in all animals sacrificed 30 or more minutes after receiving oleic acid. These correlative studies provide additional insight into the early subgross development of oleic acid-induced injury by showing the relationship between the developing edema and the bronchovascular structure of the lung.

Computed Tomographic Lung Density in Children

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.