Cardiothoracic Surgery Residency Training in Surgical Ablation for Atrial Fibrillation.

Background: As no standardized curriculum exists for training cardiothoracic surgery residents in surgical ablation for atrial fibrillation there is potential for variation in operative technique, patient selection, and overall application. Thus we sought to assess the exposure of current residents in order to identify areas for improvement in their education. Methods: A survey was emailed to residents inquiring about their training experience in surgical ablation for atrial fibrillation. Residents were asked about case volume, procedural variety, and guideline-based clinical scenarios where they felt ablation would be appropriate. Residents were also queried about their abilities to perform various lesion sets and overall satisfaction with training. Results: The respondents performed a median of five cases during training with pulmonary vein isolation the most common lesion set. Seventy seven percent of residents are unable to independently perform a bi-atrial (Cox-Maze IV) lesion set. Residents are neutral regarding their satisfaction with training in surgical ablation for atrial fibrillation. Conclusions: The findings of low case volume, incomplete lesion set use, and lack of training satisfaction suggests residents are being insufficiently exposed to surgical ablation of atrial fibrillation. These findings should inform educators on the importance of a more thorough experience during training given the increasing prevalence of atrial fibrillation and the need for appropriate and durable surgical intervention

Event-driven charge-coupled device design and applications therefor

An event-driven X-ray CCD imager device uses a floating-gate amplifier or other non-destructive readout device to non-destructively sense a charge level in a charge packet associated with a pixel. The output of the floating-gate amplifier is used to identify each pixel that has a charge level above a predetermined threshold. If the charge level is above a predetermined threshold the charge in the triggering charge packet and in the charge packets from neighboring pixels need to be measured accurately. A charge delay register is included in the event-driven X-ray CCD imager device to enable recovery of the charge packets from neighboring pixels for accurate measurement. When a charge packet reaches the end of the charge delay register, control logic either dumps the charge packet, or steers the charge packet to a charge FIFO to preserve it if the charge packet is determined to be a packet that needs accurate measurement. A floating-diffusion amplifier or other low-noise output stage device, which converts charge level to a voltage level with high precision, provides final measurement of the charge packets. The voltage level is eventually digitized by a high linearity ADC

Large-area submillimeter resolution CdZnTe strip detector for astronomy

We report the first performance measurements of a sub-millimeter CdZnTe strip detector developed as a prototype for space-borne astronomical instruments. Strip detector arrays can be used to provide two-dimensional position resolution with fewer electronic channels than pixellated arrays. Arrays of this type and other candidate technologies are under investigation for the position-sensitive backplane detector for a coded-aperture telescope operating in the range of 30 - 300 keV. The prototype is a 1.4 mm thick, 64 multiplied by 64 stripe CdZnTe array of 0.375 mm pitch in both dimensions, approximately one square inch of sensitive area. Pulse height spectra in both single and orthogonal stripe coincidence mode were recorded at several energies. The results are compared to slab- and pixel-geometry detector spectra. The room-temperature energy resolution is less than 10 keV (FWHM) for 122 keV photons with a peak-to-valley ratio greater than 5:1. The response to photons with energies up to 662 keV appears to be considerably improved relative to that of previously reported slab and pixel detectors. We also show that strip detectors can yield spatial and energy resolutions similar to those of pixellated arrays with the same dimensions. Electrostatic effects on the pulse heights, read-out circuit complexity, and issues related to design of space borne instruments are also discussed

Development of an orthogonal-stripe CdZnTe gamma radiation imaging spectrometer

We report performance measurements of a sub-millimeter resolution CdZnTe strip detector developed as a prototype for astronomical instruments operating with good efficiency in the 30-300 keV photon energy range. The prototype is a 1.4 mm thick, 64×64 contact stripe CdZnTe array of 0.375 mm pitch in both dimensions. Pulse height spectra were recorded in orthogonal-stripe coincidence mode which demonstrate room-temperature energy resolution \u3c10 keV (FWHM) for 122 keV photons with a peak-to-valley ratio \u3e5:1. Good response is also demonstrated at higher energies using a coplanar grid readout configuration. Spatial resolution capabilities finer than the stripe pitch are demonstrated. We present the image of a 133Ba source viewed through a collimator slit produced by a 4×4 stripe detector segment. Charge signals from electron and hole collecting contacts are also discussed

Performance of CdZnTe strip detectors as sub-millimeter resolution imaging gamma radiation spectrometers

We report & gamma;-ray detection performance measurements and computer simulations of a sub-millimeter pitch CdZnTe strip detector. The detector is a prototype for & gamma;-ray astronomy measurements in the range of 20-200 keV. The prototype is a 1.5 mm thick, 64×64 orthogonal stripeCdZnTe detector of 0.375 mm pitch in both dimensions, with approximately one square inch of sensitive area. Using discrete laboratory electronics to process signals from an 8×8 stripe region of the prototype we measured good spectroscopic uniformity and sub-pitch (~0.2 mm) spatial resolution in both x and y dimensions. We present below measurements of the spatial uniformity, relative timing and pulse height of the anode and cathode signals, and the photon detection efficiency. We also present a technique for determining the location of the event in the third dimension (depth). We simulated the photon interactions and signal generation in the strip detector and the test electronics and we compare these results with the data. The data indicate that the cathode signal-as well as the anode signal-arises more strongly from the conduction electrons rather than the holes

CdZnTe strip detectors as sub-millimeter resolution imaging gamma radiation spectrometers

We report γ-ray detection performance measurements and computer simulations of a sub-millimeter pitch CdZnTe strip detector. The detector is a prototype for γ-ray measurements in the range of 20-600 keV. The prototype is a 1.5 mm thick, 64×64 orthogonal stripe CdZnTe detector of 0.375 mm pitch in both dimensions, with approximately one square inch of sensitive area. Using discrete laboratory electronics to process signals from an 8×8 stripe region of the prototype we measured good spectroscopic uniformity and sub-pitch (~0.2 mm) spatial resolution in both x and y dimensions. We present below measurements of the spatial uniformity, relative timing and pulse height of the anode and cathode signals. We simulated the photon interactions and signal generation in the strip detector and the test electronics and we compare these results with the data. The data indicate that cathode signal-as well as the anode signal-arises more strongly from the conduction electrons rather than the holes

Mesoporous stilbene-based lanthanide metal organic frameworks: synthesis, photoluminescence and radioluminescence characteristics

Mesoporous non-interpenetrating stilbene-based lanthanide metal organic frameworks exhibits photo and radioluminescence behavior.</p

A Comprehensive Study of Short Bursts from SGR 1806-20 and SGR 1900+14 Detected by HETE-2

We present the results of temporal and spectral studies of the short burst (less than a few hundred milliseconds) from the soft gamma repeaters (SGRs) 1806-20 and 1900+14 using the HETE-2 samples. In five years from 2001 to 2005, HETE-2 detected 50 bursts which were localized to SGR 1806-20 and 5 bursts which were localized to SGR 1900+14. Especially SGR 1806-20 was active in 2004, and HETE-2 localized 33 bursts in that year. The cumulative number-intensity distribution of SGR 1806-20 in 2004 is well described by a power law model with an index of -1.1+/-0.6. It is consistent with previous studies but burst data taken in other years clearly give a steeper distribution. This may suggest that more energetic bursts could occur more frequently in periods of greater activity. A power law cumulative number-intensity distribution is also known for earthquakes and solar flares. It may imply analogous triggering mechanisms. Although spectral evolution during bursts with a time scale of > 20 ms is not common in the HETE-2 sample, spectral softening due to the very rapid (< a few milliseconds) energy reinjection and cooling may not be excluded. The spectra of all short bursts are well reproduced by a two blackbody function (2BB) with temperatures ~4 and ~11 keV. From the timing analysis of the SGR 1806-20 data, a time lag of 2.2+/-0.4 ms is found between the 30-100 keV and 2-10 keV radiation bands. This may imply (1) a very rapid spectral softening and energy reinjection, (2) diffused (elongated) emission plasma along the magnetic field lines in pseudo equilibrium with multi-temperatures, or (3) a separate (located at < 700 km) emission region of softer component (say, ~4 keV) which could be reprocessed X-rays by higher energy (> 11 keV) photons from an emission region near the stellar surface.Comment: 50 pages, 14 figures, accepted for publication in PAS