Background: Mortality after congenital heart defect surgery has dropped dramatically in the last few decades. Current research on long-term outcomes has focused on preventing secondary neurological sequelae, for which embolic burden is suspected. In children, little is known of the correlation between specific surgical maneuvers and embolic burden. Transcranial Doppler ultrasound is highly useful for detecting emboli but has not been widely used with infants and children. Methods: Bilateral middle cerebral artery blood flow was continuously monitored from sternal incision to chest closure in 20 infants undergoing congenital heart defect repair or palliative surgery. Embolus counts for specific maneuvers were recorded using widely accepted criteria for identifying emboli via high-intensity transient signals (HITS). Results: An average of only 13% of all HITS detected during an operation were correlated with any of the surgical maneuvers of interest. The highest mean number of HITS associated with a specific maneuver occurred during cross-clamp removal. Cross-clamp placement also had elevated HITS counts that significantly differed from other maneuvers. Conclusions: In this study of infants undergoing cardiac surgery with cardiopulmonary bypass, the great majority of HITS detected are not definitively associated with a specific subset of surgical maneuvers. Among the measured maneuvers, removal of the aortic cross-clamp was associated with the greatest occurrence of HITS. Future recommended research efforts include identifying and confirming other sources for emboli and longitudinal outcome studies to determine if limiting embolic burden affects long-term neurological outcomes.

Studies have suggested that elevated cerebrospinal fluid (CSF) pressure can have a damaging effect on the optic nerve and visual acuity. There is need for a noninvasive CSF pressure measurement technique. A portable device for noninvasive intracranial pressure (ICP) monitoring would have a significant impact on clinical care. A proof-of-concept prototype is used to test the feasibility of a technique for monitoring ICP changes. The proposed methodology utilizes transcranial Doppler ultrasonography to monitor blood flow through the ophthalmic and central retinal arteries while forces are applied to the cornea by a controlled actuator. Control algorithms for the device were developed and tested using an integrated experimental platform. Preliminary results using tissue-mimicking materials show the ability to differentiate between materials of differing stiffness that simulates different levels of ICP. These experiments are an initial step toward a handheld noninvasive ICP monitoring device.

Possible traumatic brain injury victims would greatly benefit from a handheld, noninvasive intracranial pressure (ICP) monitoring tool, which a medic could operate in a remote area. Such a device would also benefit the transport of injured soldiers during en route medical care and critical care air transport. This study demonstrates the use of noninvasive blood flow measurements in the eye by ultrasound as a proxy for ICP. ICP was artificially raised in a porcine model and resultant blood flow change in the ophthalmic artery was measured. In addition, the ultrasound transducer itself was used to compress the eye further altering ophthalmic hemodynamics. Blood flow velocities at a range of applied forces and ICP were compared. It was found that 3.25 N of force applied to the cornea was sufficient to produce significant changes in ophthalmic artery blood dynamics regardless of the ICP value. Specifically, the change in resistivity index (RI) and pulsatility index (PI) as force was applied to the cornea correlated with ICP levels. In multiple animal experiments, the magnitude of PI/RI percent change was inversely related to differences in ICP. Force applied to the cornea at baseline ICP resulted in a 15% increase in PI/RI. Results indicate that as ICP increases, the percent change in PI/RI while force is applied decreases. The consistency of data collected indicates that a trend line developed with this data and from similar experiments could be used as a predictive measurement of ICP.

We thank Dr Ü ndar and Mr Dan for their interest and comments on our recent publication, 1 "Most-high intensity transient signals are not associated with specific surgical maneuvers" in their recent Letter to the Editor. We are happy to provide a few comments and answers to questions posed in their letter.Regarding the transcranial Doppler instrumentation used (Doppler Box X; Compumedics Gmbh): we agree that the newer generation of Doppler devices have improvements in spectral quality and emboli detection. We did not find the company's fixation device suitable for long-term use on infants and neonates in the operating room. Instead, we have devised and fabricated our own and have used it in various applications (scaling the overall size to head dimensions). Prior testing of the headset proved it was quite capable of maintaining bilateral middle cerebral artery signals with excellent stability. [2][3][4][5] We do not have the emboli discrimination option (requiring dualfrequency probes) on our system, but have watched emboli detection, discrimination, and sizing technology with great interest, including the work of Dr Ü ndar's group (eg, Clark et al and Clark et al 6,7 ). Novel signal processing methods on the raw radio frequency signal and its spectral representation are required to solve this challenging problem, with accompanying clinical studies needed to determine the pediatric health significance of these emboli parameters. 8,9 We intend to follow up with further studies to determine highintensity transient signal correlations with some of the surgical parameters identified in the letter. For the current study, we used the 1/8 inch arterial line on only a few very small patients, for which a statistical comparison with the patients using the 3/16 inch line would not have achieved valid significance. We did not monitor flow proximal to the arterial cannula with an external probe. The surgical procedure incorporated a very small open shunt with adjustment of pump flow rates accordingly to ensure proper patient flow rates. The surgical purge catheter remained closed during cardiopulmonary bypass. Average values for VAVD levels were approximately À30 mm Hg, and for venous reservoir volumes approximately 100 mL.Certainly, as the letter authors stated, emboli source and delivery during surgical procedures is complex. Multidisciplinary teams are needed to solve this problem. We are glad that a robust body of literature precedes us and that the relatively small but extremely important research community represented by World Journal for Pediatric and Congenital Heart Surgery readers will continue to work together toward improving technology to accurately identify emboli burden and characteristics during cardiac procedures.

In this paper we introduce a low-cost procedure and methodology for markerless projectile tracking in three-dimensional (3D) space. Understanding the 3D trajectory of an object in flight can often be essential in examining variables relating to launch and landing conditions. Many systems exist to track the 3D motion of projectiles but are often constrained by space or the type of object the system can recognize (Qualisys, Göteborg, Sweden; Vicon, Oxford, United Kingdom; Opti-Track, Corvallis, Oregon USA; Motion Analysis, Santa Rosa, California USA; Flight Scope, Orlando, Florida USA). These technologies can also be quite expensive, often costing hundreds of thousand dollars. The system presented in this paper utilizes two high-definition video cameras oriented perpendicular to each other to record the flight of an object. A postprocessing technique and subsequent geometrically based algorithm was created to determine 3D position of the object using the two videos. This procedure and methodology was validated using a gold standard motion tracking system resulting in a 4.5 ± 1.8% deviation from the gold standard.

Research has suggested that elevated intracranial pressure (ICP) can cause damage to the optic nerve and reduce visual acuity. There is a need for noninvasive ICP monitoring devices. A simple, portable device capable of measuring relative changes in ICP using a noninvasive methodology would have a significant impact on clinical care. The methodology presented in this paper utilizes transcranial Doppler ultrasonography to monitor ophthalmic artery hemodynamics while small forces are applied to cornea. In vivo testing using a porcine model results in a correlation between pulsatility or resistivity indices and ICP levels. Specifically, the change in these indices while force is applied decreases as ICP increases. The data collection prototype used in these experiments contained an ultrasound transducer instrumented with a load cell to measure force applied to the cornea. These experiments are an initial step towards adapting the data collection prototype into a handheld noninvasive ICP monitoring device.

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