Anne M. Hubbard

Sedation for pediatric patients undergoing CT and MRI

Adequate sedation remains one of the most important parts of performing high quality cross-sectional imaging in children. This is a noncomparative retrospective analysis of existing sedation protocols used in 1,158 children between the ages of 1 day and 18 years, checking for safety and efficacy. The most commonly used drugs were chloral hydrate (60-120 mg/kg) by mouth for infants less than 18 months and intravenous Nembutal (2-6 mg/kg) for older children. Sedation was successful in 97% of patients.

Caval Contribution to Flow in the Branch Pulmonary Arteries of Fontan Patients With a Novel Application of Magnetic Resonance Presaturation Pulse

BACKGROUND A complete understanding of fluid mechanics in Fontan physiology includes knowledge of the caval contributions to right (RPA) and left (LPA) pulmonary arterial blood flow, total systemic venous return, and relative blood flow to each lung. METHODS AND RESULTS Ten Fontan patients underwent cine MRI. Three cine scans of the pulmonary arteries were performed: (1) no presaturation pulse, (2) a presaturation pulse labeling inferior vena cava (IVC) blood (signal void), and (3) a presaturation pulse labeling superior vena cava (SVC) blood. The relative signal decrease is proportional to the amount of blood originating from the labeled vena cava. This method was validated in a phantom. Whereas 60+/-6% of SVC blood flowed into the RPA, 67+/-12% of IVC blood flowed toward the LPA. Of the blood in the LPA and RPA, 48+/-14% and 31+/-17%, respectively, came from the IVC. IVC blood contributed 40+/-16% to total systemic venous return. The distributions of blood to each lung were nearly equal (RPA/LPA blood=0.94+/-11). CONCLUSIONS In Fontan patients with total cavopulmonary connection, SVC blood is directed toward the RPA and IVC blood is directed toward the LPA. Although the right lung volume is larger than the left, an equal amount of blood flow went to both lungs. LPA blood is composed of equal amounts of IVC and SVC blood because IVC contribution to total systemic venous return is smaller than that of the SVC. This technique and these findings can help to evaluate design changes of the systemic venous pathway to improve Fontan hemodynamics.

Mechanics of the Single Left Ventricle A Study in Ventricular-Ventricular Interaction II

BACKGROUND Left ventricular (LV) effects on right ventricular (RV) function are well known. Less is understood about the effect of the RV on systemic LV mechanics. To determine this interaction, we compared systemic LVs with and without an RV mechanically coupled to them. METHODS AND RESULTS MR myocardial tagging was used to examine 18 subjects with systemic LVs: 10 with functional single LVs (SLV) and 8 normal subjects (NL). Tracking the systolic motion of the intersecting stripes were used to determine regional twist and radial motion. Finite strain analysis was applied to derive principal strains at the atrioventricular valve (AVV) and apical short-axis levels and in 4 anatomic wall regions. Similar E1 (circumferential shortening) strain and heterogeneity of strain were noted between SLV and NL except in the septal wall. At the septal wall, NL displayed greater absolute strain (AVV=-0.16+/-0.02, apex=-0.17+/-0.02) and less heterogeneity of strain than SLV (AVV= -0.12+/-0.02, apex=-0.13+/-0.02). Similar E2 (wall thickening) strain and heterogeneity of strain were also noted between SLV and NL except again at the septal wall. At the septal wall, SLV displayed greater absolute E2 strain (AVV=0.17+/-0.08, apex=0.19+/-0.09) and less heterogeneity of strain than NL (AVV=0.07+/-0.07, apex=0.05+/-0.05). SLV twisted significantly less counterclockwise than NL in 6 of 8 wall regions and actually twisted clockwise at the AVV lateral wall. Although there was no significant difference between groups in radial wall motion, the septal and inferior walls of SLV demonstrated significantly less radial motion compared with other SLV walls. CONCLUSIONS A major influence of the RV on systemic LV strain and radial motion occurs in the septal wall, whereas absence of the RV causes marked differences in LV twist. These findings may yield clues to the long-term functioning of the SLV and be useful in determining strategies for RV augmentation of LV function.

Ovarian torsion: Clinical and imaging presentation in children

Ovarian torsion is uncommon and has a nonspecific clinical presentation. To determine the impact of imaging on clinical management, the authors reviewed their recent experience with 12 children who had a total of 13 episodes of ovarian torsion. Three children presented as neonates, six were premenarchal, and three were postmenarchal. Ultrasound was the imaging study of choice. In all three neonates, ultrasonography showed complex abdominopelvic cysts indicating the need for surgery. In five of 10 episodes in older patients, ultrasonography showed a solid mass with an appearance strongly suggestive of torsion. Same-day surgery was performed in three patients, and the involved ovary was salvaged in one. Another patient had a small piece of normal-appearing ovary left in situ. This low rate of ovarian salvage is attributable to the combination of delay in patient presentation and surgical delay owing to the often nonspecific clinical and imaging presentation of ovarian torsion. A high level of clinical suspicion, expeditious imaging, and familiarity with the varied clinical and imaging presentations of ovarian torsion should decrease the surgical delay and improve the likelihood of ovarian salvage.

Magnetic resonance and echocardiographic imaging of pulmonary artery size throughout stages of Fontan reconstruction.

BackgroundBecause pulmonary artery size is considered by most investigators to be a major prognosticator of outcome in patients undergoing staged Fontan reconstruction, the objective of the present study was to determine the efficacy of noninvasive measures in determining pulmonary artery size. Methods and ResultsThis study analyzed the T1-weighted, spin-echo magnetic resonance and echocardiographic images of 36 functional single-ventricle patients throughout stages of Fontan reconstruction (prebidirectional and postbidirectional cavopulmonary anastomosis and after Fontan) and compared them with angiography images at cardiac catheterization. Magnetic resonance imaging had a high degree of agreement with angiography, with the McGoon index agreeing better than the Nakata index and absolute right and left pulmonary diameters. Although echocardiography had fair agreement with angiography, it agreed less well and had a wider standard deviation than magnetic resonance imaging for all indexes and measurements and, based on the prediction interval, would be a poorer prospective measure of pulmonary artery size in this population. In addition, echocardiography was a poorer measure of pulmonary artery size as the size of the vessel increases. Magnetic resonance imaging correctly detected five of five patients with nonconfluent branch pulmonary arteries and six of six patients with stenoses, whereas echocardiography was unable to visualize any of the patients with nonconfluent branch pulmonary arteries with certainty and only two of six (33%) with stenoses. ConclusionsMagnetic resonance imaging is a useful, noninvasive tool to determine pulmonary artery size in patients undergoing Fontan reconstruction and is superior to echocardiography. Echocardiography was a fair predictor of pulmonary artery size, but magnetic resonance imaging agreed with angiography better than echocardiography and outperformed echocardiography in diagnosing branch pulmonary artery discontinuity and stenoses. Magnetic resonance imaging may avoid unnecessary cardiac catheterization, especially in older patients, and may obviate the need for jugular or subclavian catheterization in those who have undergone bidirectional cavopulmonary anastomosis.

Evaluation of iron overload by single voxel MRS measurement of liver T2

To overcome the difficulty of poor signal‐to‐noise ratio of magnetic resonance imaging (MRI) in evaluating heavy iron overload by using a single voxel magnetic resonance spectroscopy (MRS) technique.

A new tool for prenatal diagnosis: ultrafast fetal MRI.

The development of ultrafast magnetic resonance imaging scanners and sequences provides a new tool for the diagnosis of fetal anomalies. Magnetic resonance imaging is a valuable adjunct to prenatal ultrasound especially for the evaluation of suspected fetal brain anomalies, chest masses, abdominal masses, and renal diseases.

Ultrafast Fetal MRI and Prenatal Diagnosis

Improvements in magnetic resonance imaging (MRI) technology continue to provide faster scan times and higher resolution increasing the applications for fetal imaging. MRI is an adjunct to good prenatal ultrasound scan (US). It provides significant additional information that improves diagnostic accuracy in evaluation of the fetal brain, spine, neck, chest, abdomen, and urinary tract. MRI provides important anatomic information that helps in planning delivery and surgical procedures.

Magnetic resonance imaging of skewfoot.

Magnetic resonance imaging was used to visualize the ossified and unossified portions of the bones and soft tissues of the feet in order to evaluate the tarsometatarsal anatomy in sixteen children, three months to six years old (mean, fifteen months old), who were seen in the orthopaedic clinic with a suspected diagnosis of skewfoot. Twenty-seven feet were clinically abnormal and five were normal. Of the abnormal feet, twenty-six had a radiographic diagnosis of skewfoot and one, of simple metatarsus adductus. Of the skewfeet, seven had a talocalcaneal angle of 45 degrees or more as measured on the lateral radiograph and six had a talocalcaneal angle of 45 degrees or more as measured on the anterior radiograph. Valgus deformity of the hindfoot was not apparent on clinical examination in any of the children. The talocalcaneal angles measured on the magnetic resonance images corresponded poorly with those measured on the radiographs, possibly because it is not possible to simulate weight-bearing during magnetic resonance imaging or because of the effect of partial volume averaging on thin sections. However, magnetic resonance imaging demonstrated the shapes of the bones and the positions of the unossified portions of the bones. Magnetic resonance imaging showed lateral subluxation of the navicular in twenty-four skewfeet, plantar subluxation in ten, and medial subluxation of the first metatarsal on the medial cuneiform in twenty-five. The alignment of the lateral margin of the calcaneus and cuboid on the magnetic resonance images was normal in all patients. Magnetic resonance imaging has the unique ability to show the cartilaginous and ossified portions of the developing bones of the foot.

Anomalies and malformations affecting the fetal/neonatal chest

Although significant anomalies of the fetal thorax are uncommon, with improvement in high-resolution ultrasonography, more of these lesions are being diagnosed prenatally. Accurate and specific prenatal diagnosis is important because different lesions have different natural histories and prognosis. Prenatal MRI is an increasingly important adjunct for identification and differentiation of these lesions and may help determine in selected cases when and if in utero fetal intervention is indicated.