Imagining and constraining ferrovolcanic eruptions and landscapes through large-scale experiments.

Ferrovolcanism, yet to be directly observed, is the most exotic and poorly understood predicted manifestation of planetary volcanism. Large-scale experiments carried out at the Syracuse Lava Project offer insight into the emplacement dynamics of metallic flows as well as coeval metallic and silicate flows. Here, we find that, under the same environmental conditions, higher-density/lower-viscosity metallic lava moves ten times faster than lower-density/higher-viscosity silicate lava. The overall morphology of the silicate flow is not significantly affected by the co-emplacement of a metallic flow. Rather, the metallic flow is largely decoupled from the silicate flow, occurring mainly in braided channels underneath the silicate flow and as low-relief breakouts from the silicate flow front. Turbulent interactions at the metallic-silicate flow interface result in mingling of the two liquids, preserved as erosional surfaces and sharp contacts. The results have important implications for the interpretation of possible ferrovolcanic landscapes across our solar system.

Favorable outcomes in high-risk congenital pulmonary airway malformations treated with multiple courses of maternal betamethasone.

BACKGROUND/PURPOSE: Congenital pulmonary airway malformations (CPAMs) are rare congenital lung lesions often diagnosed by prenatal ultrasound. High-risk cases can result in hydrops and prenatal or postnatal demise. Antenatal betamethasone has resulted in improved survival but it is unclear how to manage patients who do not respond to a single course. METHODS: We present a bi-institutional retrospective review of patients treated with multiple courses of prenatal steroids for high-risk CPAMs between 2007 and 2013. RESULTS: Nine patients met inclusion criteria. All but one either had an increased CPAM volume ratio (CVR) or number of fluid-containing compartments involved after a single course of antenatal betamethasone, prompting additional courses. Four patients stabilized, three improved and two progressed after the second course. The two cases with disease progression underwent an in utero resection. There were one in utero fetal demise and two deaths within the delivery room. Both fetuses that underwent a fetal resection died. All but one mother who delivered a viable fetus had complications of pregnancy. CONCLUSIONS: Multiple courses of antenatal betamethasone for high-risk fetal CPAMs often result in favorable short-term outcomes without the need for open fetal resection. Pregnancy complications are common and women within this cohort should be monitored closely.

Diffusion tensor imaging of the optic nerve in multiple sclerosis: association with retinal damage and visual disability.

BACKGROUND AND PURPOSE: There is a well-known relationship between MS and damage to the optic nerve, but advanced, quantitative MR imaging methods have not been applied to large cohorts. Our objective was to determine whether a short imaging protocol (< 10 minutes), implemented with standard hardware, could detect abnormal water diffusion in the optic nerves of patients with MS. MATERIALS AND METHODS: We examined water diffusion in human optic nerves via DTI in the largest MS cohort reported to date (104 individuals, including 38 optic nerves previously affected by optic neuritis). We also assessed whether such abnormalities are associated with loss of visual acuity (both high and low contrast) and damage to the retinal nerve fiber layer (assessed via optical coherence tomography). RESULTS: The most abnormal diffusion was found in the optic nerves of patients with SPMS, especially in optic nerves previously affected by optic neuritis (19% drop in FA). DTI abnormalities correlated with both retinal nerve fiber layer thinning (correlation coefficient, 0.41) and loss of visual acuity, particularly at high contrast and in nerves previously affected by optic neuritis (correlation coefficient, 0.54). However, diffusion abnormalities were overall less pronounced than retinal nerve fiber layer thinning. CONCLUSIONS: DTI is sensitive to optic nerve damage in patients with MS, but a short imaging sequence added to standard clinical protocols may not be the most reliable indicator of optic nerve damage.

Longitudinal changes in diffusion tensor-based quantitative MRI in multiple sclerosis.

OBJECTIVE: To estimate longitudinal changes in a quantitative whole-brain and tract-specific MRI study of multiple sclerosis (MS), with the intent of assessing the feasibility of this approach in clinical trials. METHODS: A total of 78 individuals with MS underwent a median of 3 scans over 2 years. Diffusion tensor imaging indices, magnetization transfer ratio, and T2 relaxation time were analyzed in supratentorial brain, corpus callosum, optic radiations, and corticospinal tracts by atlas-based tractography. Linear mixed-effect models estimated annualized rates of change for each index, and sample size estimates for potential clinical trials were determined. RESULTS: There were significant changes over time in fractional anisotropy and perpendicular diffusivity in the supratentorial brain and corpus callosum, mean diffusivity in the supratentorial brain, and magnetization transfer ratio in all areas studied. Changes were most rapid in the corpus callosum, where fractional anisotropy decreased 1.7% per year, perpendicular diffusivity increased 1.2% per year, and magnetization transfer ratio decreased 0.9% per year. The T2 relaxation time changed more rapidly than diffusion tensor imaging indices and magnetization transfer ratio but had higher within-participant variability. Magnetization transfer ratio in the corpus callosum and supratentorial brain declined at an accelerated rate in progressive MS relative to relapsing-remitting MS. Power analysis yielded reasonable sample sizes (on the order of 40 participants per arm or fewer) for 1- or 2-year trials. CONCLUSIONS: Longitudinal changes in whole-brain and tract-specific diffusion tensor imaging indices and magnetization transfer ratio can be reliably quantified, suggesting that small clinical trials using these outcome measures are feasible.

Regional differences in diffusion tensor imaging measurements: assessment of intrarater and interrater variability.

BACKGROUND AND PURPOSE: Diffusion tensor imaging (DTI) has become a valuable tool in both the research and clinical evaluation of subjects. We sought to quantify interobserver and intraobserver variability of diffusivity and diffusion anisotropy measurements with regard to specific regions of interest (ROIs). MATERIALS AND METHODS: The subject group consisted of 5 healthy control subjects and 7 study subjects (all males; 16-19 years old; mean age = 17.5 years), as part of a protocol for closed head injury. Two whole-brain DTI scans were acquired on a 3T scanner for each subject. Analysis was performed using a ROI approach. Two independent observers analyzed the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) indices in the corpus callosum, cortical spinal tract, internal capsules (ICs), basal ganglia, and centrum semiovale (CSO). Intraobserver and interobserver variability were calculated for the mean ADC, FA, and ordered eigenvalues of the diffusion tensor (lambda(1), lambda(2), and lambda(3)). RESULTS: The overall kappa statistic for intraobserver variability for both observers showed slight-to-substantial agreement (kappa = 0.02-0.69), however FA values in the CSO showed only slight agreement. Interobserver agreement was also slight to substantial for these DTI measurements with high variability in FA values in the IC and CSO. CONCLUSIONS: When one is comparing 2 DTI measurements, it is important to assess intraobserver and interobserver variability. We recommend caution in the analysis of DTI contrasts in the IC and CSO, because we have found the widest range of variability in measurements within these structures.

ROBUST MAXIMUM LIKELIHOOD ESTIMATION IN Q-SPACE MRI.

Q-space imaging is an emerging diffusion weighted MR imaging technique to estimate molecular diffusion probability density functions (PDF's) without the need to assume a Gaussian distribution. We present a robust M-estimator, Q-space Estimation by Maximizing Rician Likelihood (QEMRL), for diffusion PDF's based on maximum likelihood. PDF's are modeled by constrained Gaussian mixtures. In QEMRL, robust likelihood measures mitigate the impacts of imaging artifacts. In simulation and in vivo human spinal cord, the method improves reliability of estimated PDF's and increases tissue contrast. QEMRL enables more detailed exploration of the PDF properties than prior approaches and may allow acquisitions at higher spatial resolution.

Plume mapping via hidden Markov methods.

This paper addresses the problem of mapping likely locations of a chemical source using an autonomous vehicle operating in a fluid flow. The paper reviews biological plume-tracing concepts, reviews previous strategies for vehicle-based plume tracing, and presents a new plume mapping approach based on hidden Markov methods (HMM). HMM provide efficient algorithms for predicting the likelihood of odor detection versus position, the likelihood of source location versus position, the most likely path taken by the odor to a given location, and the path between two points most likely to result in odor detection. All four are useful for solving the odor source localization problem using an autonomous vehicle. The vehicle is assumed to be capable of detecting above threshold chemical concentration and sensing the fluid flow velocity at the vehicle location. The fluid flow is assumed to vary with space and time, and to have a high Reynolds number (Re>10).

Fetoscopic temporary tracheal occlusion by means of detachable balloon for congenital diaphragmatic hernia.

Occlusion of the fetal trachea blocks the egress of fetal lung fluid and stimulates the growth of hypoplastic lungs in fetuses with diaphragmatic hernia. Accomplishing temporary and reversible occlusion of the fetal trachea has proven difficult without invasive fetal surgery. Using simultaneous real-time ultrasonography and fetal bronchoscopy through a single uterine port, we placed a detachable balloon in the trachea of 2 fetuses with severe diaphragmatic hernia. In both fetuses the fetal lung subsequently enlarged, allowing survival after birth.

Outcome of prenatally diagnosed solid fetal tumors.

BACKGROUND/PURPOSE: In the last 10 years, the ability to diagnose fetal tumors in the prenatal period has improved greatly because of technical advances in imaging. Early diagnosis and determination of tumor may affect prognosis. METHODS: The authors retrospectively reviewed the records of 1316 fetuses who underwent sonographic evaluation for congenital defects at University of California-San Francisco over a 6-year period. Of these, 16 had fetal tumors and were followed up at our institution. There were solid or predominantely solid with small cystic component masses in one of 3 locations: cervical, mediastinal, or abdominal. Excluded from our study were those fetuses with either sacrococcygeal teratoma, congenital cystic adenomatoid malformation of the lung, or ovarian cyst, because these defects have been extensively reviewed elsewhere. In addition, masses that were primarily cystic also were excluded. Data collected included diagnosis, gestational age at diagnosis and at delivery, mode of delivery, fetal and neonatal survival, and disease confirmation. RESULTS: Of the 16 fetuses, 4 had mediastinal tumors: 2 with pericardial teratomas (both of whom died in utero) and 2 with cardiac rhabdomyomas (1 died; the other presented tuberous sclerosis and is alive at 2 years of age). Four patients had cervical tumors (3 died; 1 survived and is alive and well), and 8 had abdominal tumors (3 with liver tumors, 4 with a left adrenal mass, and 1 with retroperitoneal teratoma). All eight patients with an abdominal tumor are alive and well. CONCLUSIONS: Fetal tumors are rare, and the prognosis seems to depend on their location and size. Although easier to detect, cervical and mediastinal tumors have a worse prognosis. Abdominal masses are more difficult to detect but have a better prognosis.

Congenital diaphragmatic hernia associated with a gastroesophageal duplication cyst: a case report.

Severe left congenital diaphragmatic hernia was diagnosed in a baby prenatally, and she underwent hernia repair on the sixth postnatal day of life. She was found to have a huge symptomatic gastroesophageal duplication cyst on day 24 of life. A thoracoabdominal dissection allowed successful cyst excision. J Pediatr Surg 36:626-628.

Adaptive observer backstepping control using neural networks.

This paper extends the application of neurocontrol approaches to a new class of nonlinear systems diffeomorphic to output feedback nonlinear systems with unmeasured states. A neural-based adaptive observer is introduced for state estimation as well as system identification using only output measurements during online operation. System identification is achieved via the online approximation of a priori unknown functions. The controller is designed using the backstepping control design procedure. Leakage terms in the adaptive laws and nonlinear damping terms in the backstepping controller are introduced to prevent instability from arising due to the inherent approximation error. A primary benefit of the online function approximation is the reduction of approximation errors, which allows reduction of both the observer and controller gains. A semi-global stability analysis for the proposed approach is provided and the feasibility is investigated by an illustrative simulation example.

Congenital diaphragmatic hernia without herniation of the liver: does the lung-to-head ratio predict survival?

The purpose of the present study was to determine the ability of lung-to-head ratio to predict survival and need for extracorporeal membrane oxygenation support in fetuses with left congenital diaphragmatic hernia without herniation of the liver into the chest. The perinatal records of 20 fetuses with isolated left congenital diaphragmatic hernia without herniation of the left lobe of the liver into the chest were reviewed. Fetuses were stratified into two groups depending on lung-to-head ratio: those with a ratio of less than 1.4 (historically a poor prognosis group) and those with a ratio of greater than 1.4. The outcome of both groups was compared with chi-square analysis. Eight of 11 fetuses with a lung-to-head ratio greater than 1.4 survived, whereas 8 of 9 fetuses with a ratio of less than 1.4 survived. No differences were noted in the need for extracorporeal membrane oxygenation support or survival between the two groups. Fetuses with a prenatally diagnosed left congenital diaphragmatic hernia without herniation of liver into the chest have a favorable prognosis even in the presence of a low lung-to-head ratio.

Successful fetal sacrococcygeal teratoma resection in a hydropic fetus.

BACKGROUND/PURPOSE: The development of hydrops in a fetus with a sacroccocygeal teratoma (SCT) usually is a predictor of fetal demise; in utero resection may offer the only chance of survival. Although the authors had performed this procedure in 3 previous cases, they had no long-term patient survival. The authors report a successful case of in utero resection of a fetal sacrococcygeal teratoma. METHODS: The authors resected a fetal SCT from a 23-weeks-gestation hydropic fetus, using gradually tightening umbilical tapes at the tumor base, electrocautery, and careful sharp dissection. After a blood transfusion, the fetus suffered cardiac arrest but was resuscitated and returned to the uterus. RESULTS: Postoperatively, residual SCT growth ceased, and hydrops rapidly resolved. Five weeks after the procedure, the infant was delivered because of preterm labor, and, after resection of residual SCT, was discharged home at 3 months of age. She is now a healthy 3 year old. CONCLUSION: This case shows that successful fetal SCT resection and long-term patient survival is possible.

Successful resuscitation during fetal surgery.

After in utero resection of a sacrococcygeal teratoma coupled with a transfusion of packed red blood cells, a 23-week-gestation fetus had bradycardia. Chest compressions were begun and epinephrine, atropine, and sodium bicarbonate were given, while the fetus remained bathed in warm saline. After 3 rounds of drugs, and just before withdrawing support, the fetal heart resumed beating and normal cardiac function. Based on to this case, the authors developed a resuscitation protocol for fetal surgery.

Twin-twin transfusion syndrome: the 'Select' procedure.

OBJECTIVES: Twin-twin transfusion syndrome (TTTS) is associated with a high risk of perinatal morbidity and mortality. The condition results from intertwin vascular connections in the shared placenta. We report here a case of early, severe TTTS that failed to respond to serial amniocenteses and that was successfully treated by means of superselective laser coagulation. METHODS: A causative arteriovenous anastomosis was identified by means of prenatal obstetrical sonography, using color and spectral Doppler techniques. At fetoscopy, performed at 23 weeks' gestation, laser occlusion of only this connection was achieved. RESULTS: This therapeutic intervention resulted in rapid resolution of all evidence of TTTS and a successful pregnancy outcome, with subsequent delivery of 2 healthy infants at 33 weeks' gestation. CONCLUSIONS: The potentially fatal pathophysiology of TTTS was reversed by interruption of a single arteriovenous connection. We have termed this the sonographically evaluated, laser-endoscopic coagulation for twins ('Select') procedure.

Cord ultrasonic transection procedure for selective termination of a monochorionic twin.

Placental vascular communications can present a life-threatening problem in monochorionic twins when one fetus has a lethal anomaly. Although selective feticide is the best option for salvaging the normal twin, techniques normally employed (i.e. intracardiac potassium, air embolism) are not prudent given the common circulatory system. Furthermore, in monoamniotic, monochorionic twin gestations it is important to transect the umbilical cord completely to prevent entanglement of the dead fetus around the cord of the normal twin. We present two cases of monochorionic twins in which the cords were transected with a harmonic scalpel under ultrasonic guidance via one trocar. The harmonic scalpel is an instrument which can simultaneously coagulate and cut blood vessels or tissues. The cord ultrasonic transection procedure is a novel, minimally invasive technique which offers several advantages over the methods currently used for selective feticide in discordant monochorionic twin gestations.

In utero repair of rectal atresia after complete resection of a sacrococcygeal teratoma.

PURPOSE: A case of a fetus with a prenatally diagnosed sacrococcygeal teratoma that produced high-output cardiac failure, hydrops, rectal atresia, and urinary tract obstruction is presented. The unique prenatal surgical management along with the embryogenesis of tumor-related rectal atresia is discussed. CASE REPORT: A large fetal sacrococcygeal teratoma with a significant intrapelvic component was detected at routine ultrasound in a 35-year-old gravida 3 para 2. Fetal hydrops developed rapidly due to high-output cardiac failure from the vascular 'steal' by the growing tumor. The urinary tract was obstructed due to the intrapelvic tumors mass. At 27 weeks' gestation, the female fetus underwent hysterotomy, resection of the entire mass and urinary diversion via bilateral flank ureterostomies. The rectum was found to be completely atretic due to apparent encasement by the tumor. Pull-through anorectoplasty was carried out concurrently. At 30 weeks' gestation, the mother developed preterm labor and a 1.8-kg was delivered by cesarean section. The baby did very well for 3 days but had a cardiac arrest and died due to an atrial perforation by a transfemoral venous catheter. CONCLUSIONS: To our knowledge this is the first report of a complete prenatal resection of a sacrococcygeal teratoma with concomitant pull-through anorectoplasty for rectal atresia.

Nonlinear adaptive control using networks of piecewise linear approximators.

This paper presents a stable nonparametric adaptive control approach using a piecewise local linear approximator. The continuous piecewise linear approximator is developed and its universal approximation capability is proved. The controller architecture is based on adaptive feedback linearization plus sliding mode control. A time varying activation region is introduced for efficient self-organization of the approximator during operation.We modify the adaptive control approach for piecewise linear approximation and self-organizing structures. In addition, we provide analyses of asymptotic stability of the tracking error and parameter convergence for the proposed adaptive control scheme with the on-line self-organizing structure. The method with a deadzone is also discussed to prevent a high-frequency input which might excite the unmodeled dynamics in practical applications. The application of the piecewise linear adaptive control method is demonstrated by a computational simulation.

Maternal fertility is not affected by fetal surgery.

The purpose of this report is to assess the impact of fetal surgery on future maternal fertility, subsequent pregnancy outcome, and the incidence of pregnancy complications. Retrospective data were collected on 70 mothers who underwent fetal surgery between April 1981 and June 1996. Indications for open hysterotomy fetal surgery included congenital diaphragmatic hernia (n = 44), congenital cystic adenomatoid malformation of the lung (n = 11), urinary obstruction (n = 9), sacrococcygeal teratoma (n = 4), heart block (n = 1), and acardiac-acephalic twin reduction (n = 1). The following data were obtained: number of pregnancy attempts, number of successful pregnancies, pregnancy outcome including obstetrical and neonatal complications, and infertility after fetal surgery. There were 45 respondents, of whom 35 attempted subsequent pregnancies. Thirty-two were successful, resulting in 31 livebirths. Two women had a strong prefetal surgery history of infertility, 1 has only attempted to conceive for 3 months. We report this experience because the effect of open fetal surgery on futrue fertility is such an important question for our patients and referring physicians. This analysis suggests that hysterotomy and open fetal surgery has a negligible impact on maternal fertility.

Fetal neurenteric cyst causing hydrops: case report and review of the literature.

Routine prenatal ultrasound revealed a unilocular cystic mass associated with upper thoracic hemivertebrae that grew to 6 cm at 28 weeks and was associated with hydrops. A thoraco-amniotic shunt decompressed the cyst and resolved the hydrops, but the shunt occluded 17 days later. Preterm labour led to vaginal delivery at 31 2/7 weeks. Postnatally, the cyst was decompressed by thoracentesis due to respiratory distress. It was resected on day four of life. Severe tracheobronchomalacia was present post-operatively, presumably due to prenatal mass effect of the cyst. At one year of age, the child has recovered completely without adverse respiratory or neurological sequelae.