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J L Strife

Publications and source records attributed to J L Strife.

At least 19 recordsLinked to original sources
PubMed2001

Three-dimensional MR microscopy of a transgenic mouse model of dilated cardiomyopathy.

BACKGROUND: Scientists are now able to alter the genetics of vertebrate embryos routinely to produce animal models of human developmental diseases. However, our understanding of structural changes in these animal models is limited by current methodologies. Histological techniques, although providing great anatomic detail, display only "static" data (one time point only) in two dimensions. Ultrasound may be used to generate continuous time course data, but is limited by interobserver variation, limited acoustic windows, and relatively low resolution. OBJECTIVE: To apply the high resolution, non-destructive, and three-dimensional acquisition capabilities of magnetic resonance (MR) microscopy to compare the hearts of normal mice versus an established transgenic mouse model of dilated cardiomyopathy. MATERIALS AND METHODS: Transgenic mice exhibiting dilated cardiomyopathy were developed via the introduction of a mutated, heart-specific gene (myosin light chain). Postmortem cardiac imaging was performed on the transgenic mice and normal controls. MR imaging was performed on a Bruker 3T imaging magnet using a custom radiofrequency coil following contrast perfusion of the atrial and ventricular chambers. Image resolution was 156 microm isotropic voxels. MR images were compared to gross pathologic specimens. Imaging data were post-processed using custom software to calculate the volumes of the atria and ventricles and to display the three-dimensional morphology of the chambers and myocardium. RESULTS: Of the seven mice scanned, four exhibited normal right atrial (average = 14.8 microl +/- 1.4), left atrial (average = 8.5 microl +/-0.3), right ventricular (average = 12.9 microl +/-2.7), and left ventricular (average 3.3 microl +/-0.5) volumes. Three mice exhibited dilatation of the right and left cardiac chambers (RA average = 23.9 microl +/-5.6; LA average = 15.9 microl +/-4.8; RV average = 32.5 microl +/- 6.8; LV average 24.0 microl +/-1.4). The gross morphology was verified upon autopsy of the animals and correlated with the animal's genotype. The differences in volumes between the normal and dilated cardiomyopathy mice were statistically significant (P values ranged from 0.001 to 0.024 for the different chambers). CONCLUSION: MR microscopy is a potentially useful tool for developmental biology research. The imaging of mouse hearts is feasible, and these methods provide quantitative and qualitative morphologic data of a mouse model of dilated cardiomyopathy not available using traditional methods.

Animals↗
PubMed2001

Is sedation safe during dynamic sleep fluoroscopy of children with obstructive sleep apnea?

OBJECTIVE: Airway compromise is considered a relative contraindication for pediatric sedation. This contraindication presents a paradoxical problem when patients require sedation in preparation for imaging performed to evaluate the cause of airway obstruction. We use dynamic sleep fluoroscopy in the evaluation of children who have obstructive sleep apnea. The purpose of this study was to evaluate the success and safety of a structured sedation program for dynamic sleep fluoroscopy. MATERIALS AND METHODS: Eighty consecutive dynamic sleep fluoroscopic studies were evaluated. The type of sedation used, success rate, complications related to the sedation, and characteristics of the children studied were reviewed. Patients were sedated in accordance with our departmental sedation program guidelines. Findings on fluoroscopy were correlated with episodes of oxygen desaturation or noisy breathing. RESULTS: In all 80 cases, dynamic sleep fluoroscopy was successfully performed. Seventy-two studies were performed, with sedation supervised by the radiologist. Four patients fell asleep without sedation. In four patients, sedation was performed by an anesthesiologist (preprocedural decision). Sixty-four children (80%) had complex medical problems, and 39 (49%) had a history of previous airway surgery. All studies were considered successful. Specific diagnoses were identified in 66 children (83%). No children suffered complications or required tracheal intubation. CONCLUSION: Children with airway compromise who are being evaluated for obstructive sleep apnea can be successfully and safely sedated for dynamic sleep fluoroscopy when a structured sedation program is used.

Child, Preschool↗
PubMed2000

Spiral CT versus MRI in neonatal airway evaluation.

Magnetic resonance imaging has become the standard means of imaging pediatric airway obstruction due to vascular anomalies. However, magnetic resonance imaging requires a long acquisition time and is prone to motion artifacts. The development of spiral or helical computed tomography provides an alternative imaging modality for evaluating pediatric airway obstruction. We present the case of a neonate with a double aortic arch which initially was not identified on magnetic resonance imaging but was visualized with spiral computed tomography. If suspicion of an intra-thoracic abnormality is high, spiral computed tomography may be a useful adjunct or replacement to magnetic resonance imaging.

Airway Obstruction↗
PubMed2000

A multihospital survey of radiation exposure and image quality in pediatric fluoroscopy.

BACKGROUND: Traditionally, pediatric radiologists have been advocates of fluoroscopy systems that provide diagnostic images at the lowest possible radiation dose to the pediatric patient. Manufacturers of fluoroscopic equipment vary as to their claims of "low radiation" exposures. OBJECTIVES: To obtain comparative data on radiation exposure and image quality from four pediatric hospitals, across variants of fluoroscopic equipment (such as pulsed versus continuous fluoroscopy). MATERIALS AND METHODS: Images were acquired from phantoms that simulated the size of a 3-year-old child. Phantom results, both stationary and rotating dynamic, were evaluated for radiation exposure and for image resolution of high- and low-contrast objects. RESULTS: Radiation exposure from the four fluoro units varied widely; the lowest-dose selectable fluoro mode produced exposures varying between 34 and 590 mrads/min among the four fluoro units, and the highest-dose selectable fluoro mode produced 540-2,230 mrads/min. The lowest radiation exposures were produced by pulsed fluoro units, and the very lowest radiation exposure was produced by a fluoroscope that had been especially optimized for pediatric imaging. There was only a small variation in image quality among the hospitals for visualization of stationary objects. A wide variability was noted for detection of objects on the moving phantom. CONCLUSIONS: The variability in the number of detected objects was considerably smaller than the variability in radiation exposure. Pulsed fluoroscopy provides improved resolution for moving objects. Optimization of one hospital's fluoroscope especially for pediatric imaging produced the best ratio of image quality to radiation exposure.

Age Factors↗
PubMed2000

Congenital diaphragmatic hernia in neonates: variations in umbilical catheter and enteric tube position.

PURPOSE: To evaluate anatomic variations of support apparatus position on radiographs obtained in neonates with congenital diaphragmatic hernia (CDH). MATERIALS AND METHODS: The authors evaluated radiographs obtained in 71 neonates with CDH to determine whether nasogastric tubes, umbilical venous catheters, and umbilical arterial catheters deviated from their expected anatomic course. The relationship between deviation patterns and hernia contents was evaluated. RESULTS: Sixty-eight neonates-54 with left-sided CDH and 14 with right-sided CDH-had a nasogastric tube. The tubes in 21 patients with left-sided CDH had a normal anatomic course at radiography. Nineteen of these patients did not have stomach in the hernia. In 13 patients, the tip of the nasogastric tube was lodged at the esophagogastric junction. In 17 patients, the tube was in the left hemithorax. In all 30 of these patients, the stomach was within the CDH. All nasogastric tubes in the 14 patients with right-sided CDH had leftward deviation. Thirty-seven patients-27 with left-sided CDH and 10 with right-sided CDH-had umbilical venous catheters. The catheters in 12 patients with left-sided CDH had apex leftward convexity. The umbilical venous catheter in eight patients with right-sided CDH had rightward shift; all eight patients had liver herniation. CONCLUSION: The positions of nasogastric tubes and umbilical venous catheters vary in several predictable patterns in neonates with CDH. Knowledge of these variations may be helpful for supporting the diagnosis of CDH in unclear cases and thus avoiding unnecessary apparatus adjustments, and for predicting hernia contents.

Catheterization, Peripheral↗
PubMed2000

Glossoptosis (posterior displacement of the tongue) during sleep: a frequent cause of sleep apnea in pediatric patients referred for dynamic sleep fluoroscopy.

OBJECTIVE: The purpose of this study was to evaluate the frequency of glossoptosis (posterior displacement of the tongue) as a cause of sleep apnea in pediatric patients referred for fluoroscopic sleep studies. MATERIALS AND METHODS: Seventy consecutive dynamic fluoroscopic sleep studies performed to evaluate sleep apnea were reviewed. All patients had been sedated and examined with lateral fluoroscopy during sleep. Anatomic changes in the airway were correlated with episodes of oxygen desaturation. Cases of glossoptosis, in which the tongue moved posteriorly during sleep and abutted the posterior pharynx, resulting in airway obstruction and oxygen desaturation, were identified. Associated factors were reviewed. RESULTS: Of 70 sleep studies reviewed, glossoptosis was the cause of airway obstruction in 17 patients (24%). Mean age in these 17 patients was 3 years (range, 5 days to 13 years). Seven of the 17 children were younger than 1 year old. Only three patients had no underlying medical problems. Four patients had macroglossia (Down syndrome, n = 3; duplicated tongue, n = 1) as a cause, and three patients had micro- or retrognathia (Pierre Robin syndrome, n = 2; Rubinstein-Taybi syndrome, n =1) as a cause. Six patients had neuromuscular abnormalities. CONCLUSION: Glossoptosis was a cause of airway obstruction in 25% of pediatric patients referred for fluoroscopic sleep studies. Attention to this anatomic region is important when evaluating children with sleep apnea.

Airway Obstruction↗