The purpose of this study was to prospectively test the hypothesis that systemic anticoagulation is not needed following coronary stenting when adequate stent expansion is achieved and documented and other flow limitations eliminated. Intravascular ultrasound (IVUS) was used to confirm adequate stent expansion, which was defined as good plaque compression together with the achievement of an intrastent lumen cross-sectional area (CSA) that was greater than 40% of the average reference vessel CSA. In this prospective study, Palmaz-Schatz coronary stenting was performed on 343 lesions in 263 consecutive patients. Primary stenting was successful in 254 patients (96.6%) and 332 lesions (96.8%). All patients with successful primary stenting underwent IVUS imaging except nine patients (13 lesions) that did not have an IVUS evaluation for technical reasons and three patients (4 lesions) in which IVUS was unsuccessful. The initial IVUS performed after achieving an acceptable angiographic result revealed inadequate stent expansion in 191 patients (79%) and 244 lesions (77%). After further dilatation, final adequate stent expansion was accomplished in 230 patients and 301 lesions. These patients were treated with Ticlopidine 250 mg twice per day for 2 months and did not receive postprocedure anticoagulation. There was one acute stent thrombosis (0.3%) that occurred in a lesion with slow flow and an inadequately expanded stent. There was no subacute stent thrombosis and no bleeding or vascular complications. We conclude that when adequate stent expansion is achieved and confirmed and other flow limiting lesions eliminated, that systemic anticoagulation after the stent procedure is not necessary.

lntravascular ultrasound imaging (IVUS) is limited by the size of the imaging catheter. To facilitate imaging prior to and during interventions, a 30 MHz ultrasonic imaging device was developed that is the same dimension as an 0.018" guidewire. This imaging core was tested in 8 patients with the use of a monorail guiding sheath that was advanced through a 7Fr catheter. In addition, the standard guidewire was removed and the imaging core was placed inside a compatible balloon and imaging was performed following 6 coronary interventions. The mean lumen CSA was 6.8 ± 3.2 mm2. The lumenplaque interface and the media-plaque interface were clearly visualized in all patients. In 4 patients, imaging was also performed with a standard 2.9 Fr IVUS catheter. There was no detectable loss in image quality between the new imaging device and the larger IVUS catheter, and measurements of lumen CSA were not statistically different. Conclusions: Improvements in manufacturing technology have permited the development of a mechanically rotating ultrasound imaging core which is 0.018" in diameter. It is compatible with current balloon catheters without degradation of image quality.

OBJECTIVES:Intravascular ultrasound imaging (IVUS) is limited by the size of the imaging catheter. To facilitate imaging before and during interventions, a 30-MHz ultrasonic imaging device was developed that is the same dimension as a 0.018-inch guide wire. The purpose of this study was to evaluate the clinical feasibility of this device. METHODS AND RESULTS:The imaging core was tested in 8 patients with the use of a monorail guiding sheath that was advanced through a 7F catheter. In addition, after coronary interventions, the standard guide wire was removed, the imaging core was placed inside a compatible balloon, and imaging was performed. In 4 patients, imaging was also performed with a standard 3.2F IVUS catheter. The lumen-plaque interface and the media-plaque interface were clearly visualized in all patients. There was no detectable loss in image quality between the new imaging device and the larger IVUS catheter, and measurements of lumen cross-sectional area were not statistically different. CONCLUSIONS:Improvements in manufacturing technology have permitted the development of a mechanically rotating ultrasound imaging core 0.018 inches in diameter. It is compatible with current balloon catheters without degradation of image quality.

Background

The placement of stents in coronary arteries has been shown to reduce restenosis in comparison to balloon angioplasty. However, clinical use of intracoronary stents is impeded by the risk of subacute stent thrombosis and complications associated with the anticoagulant regimen. To reduce these complications, the hypothesis that systemic anticoagulation is not necessary when adequate stent expansion is achieved was prospectively evaluated on a consecutive series of patients who received intracoronary stents.

Methods and results

From March 1993 to January 1994, 359 patients underwent Palmaz-Schatz coronary stent insertion. After an initial successful angiographic result with < 20% stenosis by visual estimation had been achieved, intravascular ultrasound imaging was performed. Further balloon dilatation of the stent was guided by observation of the intravascular ultrasound images. All patients with adequate stent expansion confirmed by ultrasound were treated only with antiplatelet therapy (either ticlopidine for 1 month with short-term aspirin for 5 days or only aspirin) after the procedure. Clinical success (procedure success without early postprocedural events) at 2 months was achieved in 338 patients (94%). With an inflation pressure of 14.9 +/- 3.0 atm and a balloon-to-vessel ratio of 1.17 +/- 0.19, optimal stent expansion was achieved in 321 of the 334 patients (96%) who underwent intravascular ultrasound evaluation, with these patients receiving only antiplatelet therapy after the procedure. Despite the absence of anticoagulation, there were only two acute stent thromboses (0.6%) and one subacute stent thrombosis (0.3%) at 2-month clinical follow-up. Follow-up angiography at 3 to 6 months documented two additional occlusions (0.6%) at the stent site. At 6-month clinical follow-up, angiographically documented stent occlusion had occurred in 5 patients (1.6%). At 6-month clinical follow-up, there was a 5.7% incidence of myocardial infarction, a 6.4% rate of coronary bypass surgery, and a 1.9% incidence of death. Emergency intervention (emergency angioplasty or bailout stent) for a stent thrombosis event was performed in 3 patients (0.8%). The overall event rate was relatively high because of intraprocedural complications that occurred in 16 patients (4.5%). Intraprocedural complications, however, decreased to 1% when angiographically appropriately sized balloons were used for final stent dilations. There was one ischemic vascular complication that occurred at the time of the procedure and one ischemic vascular complication that occurred at the time of angiographic follow-up. By 6 months, repeat angioplasty for symptomatic restenosis was performed in 47 patients (13.1%).

Conclusions

The Palmaz-Schatz stent can be safely inserted in coronary arteries without subsequent anticoagulation provided that stent expansion is adequate and there are no other flow-limiting lesions present. The use of high-pressure final balloon dilatations and confirmation of adequate stent expansion by intravascular ultrasound provide assurance that anticoagulation therapy can be safely omitted. This technique significantly reduces hospital time and vascular complications and has a low stent thrombosis rate.

Low-dose Proton Computed Tomography (pCT) is an evolving imaging modality that is used in proton therapy planning which addresses the range uncertainty problem. The goal of pCT is generating a 3D map of Relative Stopping Power (RSP) measurements with high accuracy within clinically required time frames. Generating accurate RSP values within the shortest amount of time is considered a key goal when developing a pCT software. The existing pCT softwares have successfully met this time frame and even succeeded this time goal, but requiring clusters with hundreds of processors. This paper describes a novel reconstruction technique using two Graphics Processing Unit (GPU) cores, such as is available on a single Nvidia P100. The proposed reconstruction technique is tested on both simulated and experimental datasets and on two different systems namely Nvidia K40 and P100 GPUs from IBM and Cray. The experimental results demonstrate that our proposed reconstruction method meets both the timing and accuracy with the benefit of having reasonable cost, and efficient use of power.

We present the Data Release 12 Quasar catalog (DR12Q) from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. This catalog includes all SDSS-III/BOSS objects that were spectroscopically targeted as quasar candidates during the full survey and that are confirmed as quasars via visual inspection of the spectra, have luminosities Mi [z = 2] <-20.5 (in a ΛCDM cosmology with H0 = 70 km s-1 Mpc-1, ΩM = 0.3, and ΩΛ = 0.7), and either display at least one emission line with a full width at half maximum (FWHM) larger than 500 km s-1 or, if not, have interesting/complex absorption features. The catalog also includes previously known quasars (mostly from SDSS-I and II) that were reobserved by BOSS. The catalog contains 297 301 quasars (272 026 are new discoveries since the beginning of SDSS-III) detected over 9376 deg2 with robust identification and redshift measured by a combination of principal component eigenspectra. The number of quasars with z > 2.15 (184 101, of which 167 742 are new discoveries) is about an order of magnitude greater than the number of z > 2.15 quasars known prior to BOSS. Redshifts and FWHMs are provided for the strongest emission lines (C iv, C iii], Mg ii). The catalog identifies 29 580 broad absorption line quasars and lists their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry with typical accuracy of 0.03 mag together with some information on the optical morphology and the selection criteria. When available, the catalog also provides information on the optical variability of quasars using SDSS and Palomar Transient Factory multi-epoch photometry. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra, covering the wavelength region 3600-10 500 Å at a spectral resolution in the range 1300 < R < 2500, can be retrieved from the SDSS Catalog Archive Server. We also provide a supplemental list of an additional 4841 quasars that have been identified serendipitously outside of the superset defined to derive the main quasar catalog.

We present the second edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 16,713 objects in the SDSS First Data Release that have luminosities larger than Mi = -22 (in a cosmology with H0 = 70 km s-1 Mpc-1, ΩM= 0.3, and Ω∇ = 0.7), have at least one emission line with FWHM larger than 1000 km s-1, and have highly reliable redshifts. The area covered by the catalog is ≈ 1360 deg 2. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.43. For each object, the catalog presents positions accurate to better than 0.′2 rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains some radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. Calibrated digital spectra of all objects in the catalog, covering the wavelength region 3800-9200 Å at a spectral resolution of 1800-2100, are available. This publication supersedes the first SDSS Quasar Catalog, which was based on material from the SDSS Early Data Release. A summary of corrections to current quasar databases is also provided. The majority of the objects were found in SDSS commissioning data using a multicolor selection technique. Since the quasar selection algorithm was undergoing testing during the entire observational period covered by this catalog, care must be taken when assembling samples from the catalog for use in statistical studies. A total of 15,786 objects (94%) in the catalog were discovered by the SDSS; 12,173 of the SDSS discoveries are reported here for the first time. Included in the new discoveries are five quasars brighter than i= 16.0 and 17 quasars with redshifts larger than 4.5.

(Abridged) This is the Maunakea Spectroscopic Explorer 2018 book. It is intended as a concise reference guide to all aspects of the scientific and technical design of MSE, for the international astronomy and engineering communities, and related agencies. The current version is a status report of MSE's science goals and their practical implementation, following the System Conceptual Design Review, held in January 2018. MSE is a planned 10-m class, wide-field, optical and near-infrared facility, designed to enable transformative science, while filling a critical missing gap in the emerging international network of large-scale astronomical facilities. MSE is completely dedicated to multi-object spectroscopy of samples of between thousands and millions of astrophysical objects. It will lead the world in this arena, due to its unique design capabilities: it will boast a large (11.25 m) aperture and wide (1.52 sq. degree) field of view; it will have the capabilities to observe at a wide range of spectral resolutions, from R2500 to R40,000, with massive multiplexing (4332 spectra per exposure, with all spectral resolutions available at all times), and an on-target observing efficiency of more than 80%. MSE will unveil the composition and dynamics of the faint Universe and is designed to excel at precision studies of faint astrophysical phenomena. It will also provide critical follow-up for multi-wavelength imaging surveys, such as those of the Large Synoptic Survey Telescope, Gaia, Euclid, the Wide Field Infrared Survey Telescope, the Square Kilometre Array, and the Next Generation Very Large Array.