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Demonstrating the viability of Advanced Accelerator Concepts (AAC) relies on experimental validation. Over the last three decades, the U.S. has maintained a portfolio of advanced and novel accelerator test facilities to support research critical to AAC. The facilities have enabled pioneering developments in a wide variety of beam and accelerator physics, including plasma-wakefield and structure-wakefield acceleration. This paper provides an overview of the current portfolio of U.S. facilities possessing charged particle drive beams with high energies, on the order of tens of joules per pulse, or drive lasers with high peak powers, on the order of a petawatt, and are actively conducting AAC research.

In a plasma wakefield accelerator (PWFA), using advanced injection techniques such as the density down-ramp injection is a promising approach for generating electron beams with ultralow emittance. In this study, we describe how such a scheme could be realized using the beam from the Linac Coherent Light Source (LCLS) accelerator as a driver. Moreover, we explore the potential applications of such high-brightness e-beams in a facility like LCLS and in novel concepts for compact FELs.

A 9-month old castrated male Labradoodle presented to the cardiology service at Purdue University for evaluation of a low-grade murmur. Physical examination, thoracic radiography, and echocardiography were strongly supportive of an extracardiac left-to-right shunt. Subsequent evaluation with nuclear scintigraphy and computed tomography angiography revealed a large, complex arteriovenous malformation within the cranial abdomen. Staged interventional attenuation of the shunt was performed using n-butyl cyanoacrylate that resulted in a reduction in echocardiographic and nuclear scintigraphy derived shunt estimation.

Hematoma expansion in intracerebral hemorrhage is associated with poor clinical outcome. The ‘spot sign’ is a radiological marker that is associated with hematoma expansion, and thought to represent active extravasation of contrast. This case demonstrates the use of dynamic CT angiography in identifying the time-dependent appearance of a spot sign in a patient with warfarin-associated intracerebral hemorrhage. Repeat imaging is also presented which verified cessation of the spot sign after INR correction.

Background The effectiveness of intravenous tissue plasminogen activator in the management of acute ischemic strokes diminishes significantly with time. Advanced computed tomography (CT) imaging can be helpful to identify candidates for neurointerventional procedures. We have successfully used a 320-slice Toshiba volume CT scanner since mid-2008. Other centers have forgone advanced imaging because of concerns of time delay. This study is to assess the time delay while using this scanner compared with our 64-slice scanner. Methods Treatment times of patients scanned with advanced imaging (CT head, dynamic CT angiography, and whole brain perfusion–group A) and patients scanned in a 64-slice scanner (CT head and traditional CT angiogram–group B) were compared. Two groups of stroke patients from November-March 2009-2010 (group 1) and 2012-2013 (group 2) were audited to assess temporal improvement. Multiple timing variables were analyzed. Results One hundred fifty-three cases from 2009/10 and 192 cases from 2012/13 were analyzed. The median door-to-needle time (DNT) for group 1A and group 2A was 57 minutes and 47 minutes, respectively. The median DNT for group 1B and group 2B was 54 minutes and 49 minutes, respectively. Decrease in the overall DNT with group A can be attributed to the “streamlining” of the stroke code process. There was no difference in the DNT for patients who presented during working hours versus those who presented during nonworking hours. Conclusions With adequate experience and training, advanced stroke imaging with whole brain perfusion/dynamic CT angiography can be performed with treatment times that are comparable with traditional CT scanning.

Saint Louis University created a 24/7 remotely accessible "computer laboratory" where students receive full server administration privileges to use in developing their server, networking, security, and database administration skills using the Linux operating system. The university's decision to outsource the computer lab to MDK was simple. The resulting partnership provided each student in a senior-level undergraduate Web Applications and Architectures course with a virtual Linux server as well as full administrative rights.

BACKGROUND AND PURPOSE: The accuracy of tumor plasma volume and K(trans) estimates obtained with DCE MR imaging may have inaccuracies introduced by a poor estimation of the VIF. In this study, we evaluated the diagnostic accuracy of a novel technique by using a phase-derived VIF and “bookend” T1 measurements in the preoperative grading of patients with suspected gliomas. MATERIALS AND METHODS: This prospective study included 46 patients with a new pathologically confirmed diagnosis of glioma. Both magnitude and phase images were acquired during DCE MR imaging for estimates of K(trans)_ϕ and V(p_)ϕ (calculated from a phase-derived VIF and bookend T1 measurements) as well as K(trans)_SI and V(p_)SI (calculated from a magnitude-derived VIF without T1 measurements). RESULTS: Median K(trans)_ϕ values were 0.0041 minutes(−1) (95 CI, 0.00062–0.033), 0.031 minutes(−1) (0.011–0.150), and 0.088 minutes(−1) (0.069–0.110) for grade II, III, and IV gliomas, respectively (P ≤ .05 for each). Median V(p_)ϕ values were 0.64 mL/100 g (0.06–1.40), 0.98 mL/100 g (0.34–2.20), and 2.16 mL/100 g (1.8–3.1) with P = .15 between grade II and III gliomas and P = .015 between grade III and IV gliomas. In differentiating low-grade from high-grade gliomas, AUCs for K(trans)_ϕ, V(p_)ϕ, K(trans)_SI, and V(p_)SI were 0.87 (0.73–1), 0.84 (0.69–0.98), 0.81 (0.59–1), and 0.84 (0.66–0.91). The differences between the AUCs were not statistically significant. CONCLUSIONS: K(trans)_ϕ and V(p_)ϕ are parameters that can help in differentiating low-grade from high-grade gliomas.

When a highly relativistic electron is injected off-axis into an ion channel, the restoring force of the radial field of the ions will cause the electron to accelerate towards the axis, overshoot, and begin to undergo oscillations about the ioncolumn axis at a characteristic frequency; the betatron frequency. This so-called betatron motion will cause the electron to radiate hard x-rays in the forward direction. In two recent experiments at the Stanford Linear Accelerator Center (SLAC), betatron x-rays in the 1-20kV range and in the 1-50MV range were produced with an electron beam with an energy of 28.5 GeV for ion densities of about 1 x 10 14 cm -3 and 1 x 10 17 cm -3 , respectively. To make such an x-ray source more compact, the 3km long SLAC linac would be replaced by a source of electrons from a Laser Wakefield accelerator (LWFA). To increase the efficiency of converting laser into photons at high photon energies, we propose adding a second stage where the LWFA electrons radiate via a second ion channel, independent of the accelerating process. This two stage concept allows one to control the critical frequency of the emitted radiation as well as the efficiency of the process.

Background and Purpose— We investigated whether computed tomography (CT) perfusion–derived cerebral blood flow (CBF) and cerebral blood volume (CBV) could be used to differentiate between penumbra and infarcted gray matter in a limited, exploratory sample of acute stroke patients. Methods— Thirty patients underwent a noncontrast CT (NCCT), CT angiography (CTA), and CT perfusion (CTP) scan within 7 hours of stroke onset, NCCT and CTA at 24 hours, and NCCT at 5 to 7 days. Twenty-five patients met the criteria for inclusion and were subsequently divided into 2 groups: those with recanalization at 24 hours (n=16) and those without (n=9). Penumbra was operationally defined as tissue with an admission CBF −1 · min −1 that was not infarcted on the 5- to 7-day NCCT. Logistic regression was applied to differentiate between infarct and penumbra data points. Results— For recanalized patients, CBF was significantly lower ( P −1 · min −1 ) than penumbra (25.0±3.82 mL · 100 g −1 · min −1 ). CBV in the penumbra (2.15±0.43 mL · 100 g −1 ) was significantly higher than contralateral (1.78±0.30 mL · 100 g −1 ) and infarcted tissue (1.12±0.37 mL · 100 g −1 ). Logistic regression using an interaction term (CBF×CBV) resulted in sensitivity, specificity, and accuracy of 97.0%, 97.2%, and 97.1%, respectively. The interaction term resulted in a significantly better ( P −1 · min −1 and 1.17±0.41 mL · 100 g −1 , respectively. Conclusions— We have shown in a limited sample of patients that CBF and CBV obtained from CTP can be sensitive and specific for infarction and should be investigated further in a prospective trial to assess their utility for differentiating between infarct and penumbra.

BACKGROUND AND PURPOSE: Standard (static) CT angiography is used to identify the intracerebral hemorrhage (ICH) spot sign. We used dynamic CT-angiography to describe spot sign characteristics and measurement parameters over 60-seconds of image acquisition. METHODS: We prospectively identified consecutive patients presenting with acute ICH within 4.5 hours of symptom onset, and collected whole brain dynamic CT-angiography (dCTA). Spot parameters (earliest appearance, duration, maximum Hounsfield unit (HU), time to maximum HU, time to spot diagnostic definition, spot volume and hematoma volumes) were measured using volumetric analysis software. RESULT: We enrolled 34 patients: three were excluded due to secondary causes of ICH. Of the remaining 31 patients there were 18 females (58%) with median age 70 (range 47-86) and baseline hematoma volume 33 ml (range 0.7-103 ml). Positive dCTA spot sign was present in 13 patients (42%) visualized as an expanding 3-dimensional structure temporally evolving its morphology over the scan period. Median time to spot appearance was 21 s (range 15-35 seconds). This method allowed tracking of spots evolution until the end of venous phase (active extravasation) with median duration of 39 s (range 25-45 seconds). The average density and time to maximum density was 204HU and 30.8 s (range 23-31 s) respectively. Median time to spot diagnosis was 20.8 s using either 100 or 120HU definitions. CONCLUSION: Dynamic CTA allows a 3-dimensional assessment of spot sign formation during acute ICH, and captured higher spot sign prevalence than previously reported. This is the first study to describe and quantify spot sign characteristics using dCTA; these can be used in ongoing and upcoming ICH studies.

A method for using Cerenkov radiation near atomic spectral lines to measure plasma source properties for plasma wakefield applications has been discussed and experimentally verified. Because the radiation co-propagates with the electron beam, the radiation samples the source properties exactly along the path of interest with perfect temporal synchronization. Observation wavelengths were chosen with respect to the atomic resonances of the plasma source, where the relative change in the index of refraction strongly affects the Cerenkov cone angle, and permits flexible diagnostic design. The Cerenkov spatial profiles were systematically studied for a Lithium heat pipe oven as a function of oven temperature and observation wavelength. Neutral densities and plasma densities were extracted from the measurements.

A prototype positron emission tomography (PET) system has been designed for high-resolution imaging of small volumes. The detectors use Pb converter stacks and multiwire proportional counters (MWPC); the data acquisition components and image reconstruction methods are also described briefly. The performance of the system is discussed in terms of sensitivity, count rate capability, spatial resolution, and scattered background. Three examples of metabolic or transport imaging demonstrate the capabilities and limitations of the system. These are blood flow to bone, cerebral glucose uptake, and nutrient translocation in plants. The performance of the prototype has been sufficiently promising that an improved system is under development.

Compton scattering of gamma rays within the image volume has been assessed for a large-aperture positron-emission-tomography imaging system. The Compton scattered attenuation and the Compton scattered background were both modeled and measured for point sources centered in scattering spheres up to 10 cm in diameter. Good agreement was obtained between simulations and measurements. The attenuation problem is independent of the detector system, but its correction is more difficult in a large-aperture system. The scattered coincidence background is large in this system (43% for a 10-cm-diameter scattering sphere), but the background overlap is reduced with 3D imaging. >