kV Energy Research Articles

SU‐GG‐I‐15: An Analytical Approach to Correction for X‐Ray Scatter in Heterogeneous Medium

Purpose: To approximately express first order Compton scatter fluence as a function of primary fluence at detector, and to develop a method for scatter correction based on the analytical approximation. Method and Materials: From the Klein‐Nishina formula for the first order Compton scatter we derive an approximate form in which the function characterizing the scattering object is separated from the known information on the imaging system, including the geometry and the source photon spectrum. Based on the strong correlation between the unknown 3‐D object function and its projection, which can be measured, we estimate the first order scatter and the primary fluence through an iterative scheme. We use a Catphan phantom to experimentally measure primary and scatter fluences, as well as simple Monte Carlo models to determine primary and any order scatter fluences through computer simulation. These experimental and Monte Carlo results are utilized to validate our analytical approach. Results: For simple object models, our approximation results are within 2% of relative error from the exact solution (obtained using the Klein‐Nishina formula and verified with from Monte Carlo simulations). For the Catphan phantom, the relative error is within 3% between the estimated and experimentally measured primary fluences. Tomographic image reconstructions from scatter corrected projections show clearly the advantages of our scatter correction scheme in improving the accuracy of CT numbers and soft‐tissue contrast. Conclusion: Our analytical scheme can estimate primary and first order scatter x‐ray fluences to high accuracy without requiring any additional imaging time and dose to the patient. It can be employed for scatter correction in a variety x‐ray transmission imaging applications, including cone beam CT at both kV and MV photon energy ranges. The correction process is also computationally efficient — it requires a few seconds of processing time per projection image.

Extracorporeal shock wave treatment in nonunions of long bone fractures

We reviewed the clinical results of the past 7 years in order to investigate the effect of extracorporeal shock wave therapy (ESWT) in nonunions of long bone fracture. Sixty-nine patients with 69 nonunions (22 femora, 28 tibiae, 13 humeri, 5 radii, and 1 ulna) were treated with extracorporeal shock waves. The technical parameters were 6,000 to 10,000 impulses at 28 kV (0.62 mJ/mm(2) energy flux density) for the femur and tibia, 4,000 impulses at 24 kV for the humerus (0.56 mJ/mm(2) energy flux density), and 3,000 impulses at 24 kV (0.56 mJ/mm(2) energy flux density) for the radius and ulna. Sixty-six patients were followed up. The total successful rate of bony union was 75.4%. ESWT was successful in hypertrophic nonunions and seemed to have no evident effect in atrophic nonunions. We believe that extracorporeal shock wave therapy may be a good choice for nonunions of long bone fracture especially in hypertrophic nonunions.

SU-FF-T-192: DVS MOSFET Dosimeter Response to Kilovoltage Radiation

Purpose: To determine the dose response of implantable DVS MOSFET dosimeters to kilovoltage x‐ray radiation compared to the response to irradiation from a 60 Co source. Method and Materials: Sicel Technologies, Inc. has developed a Dose Verification System (DVS®), using implantable MOSFET dosimeters that are read telemetrically by an inductively coupled antenna. Three Virtual Water™ phantom cassettes, each containing four DVS dosimeters, were irradiated in a Virtual Water phantom with a 60 Co source for five doses of 200 cGy. These were used as controls to compare to a fourth cassette that was similarly irradiated by the 60 Co source before it was exposed to kV energy at NIST‐equivalent beam qualities of M80, L100, M100, M120, and M150. The dose delivered was determined following TG‐61 protocol (in‐phantom method at 2 cm depth), substituting Virtual Water for liquid water. Following the x‐ray exposures, the cassette was exposed again to 60 Co to confirm device stability. Results: Before correcting for temperature, energy, and isotropy, the 60 Co cassettes demonstrated a slight and consistent under‐response. After appropriate scaling, the overall ratio of corrected dose measured to dose delivered was 1.002 ± 0.004. The dosimeters irradiated with the kV beams, however, exhibited an over‐response. The overall ratio of corrected dose measured to dose delivered for the kV beams was 2.428 ± 0.043, whereas the same cassette demonstrated nearly the same response to the 60 Co source as the other three cassettes, with a ratio of corrected dose measured to dose delivered of 0.9755 ± 0.0113. Conclusion: This data shows the DVS dose response for the examined kV beams at 2 cm depth is ∼2–3 times greater than the response at MeV energies from the 60 Co source due to the shift in dominance from Compton to photoelectric events. Conflict of Interest: Funding for this research was provided by Sicel Technologies, Inc.

Phosphorylation of Ser-129 Is the Dominant Pathological Modification of α-Synuclein in Familial and Sporadic Lewy Body Disease

A comprehensive, unbiased inventory of synuclein forms present in Lewy bodies from patients with dementia with Lewy bodies was carried out using two-dimensional immunoblot analysis, novel sandwich enzyme-linked immunosorbent assays with modification-specific synuclein antibodies, and mass spectroscopy. The predominant modification of alpha-synuclein in Lewy bodies is a single phosphorylation at Ser-129. In addition, there is a set of characteristic modifications that are present to a lesser extent, including ubiquitination at Lys residues 12, 21, and 23 and specific truncations at Asp-115, Asp-119, Asn-122, Tyr-133, and Asp-135. No other modifications are detectable by tandem mass spectrometry mapping, except for a ubiquitous N-terminal acetylation. Small amounts of Ser-129 phosphorylated and Asp-119-truncated alpha-synuclein are present in the soluble fraction of both normal and disease brains, suggesting that these Lewy body-associated forms are produced during normal metabolism of alpha-synuclein. In contrast, ubiquitination is only detected in Lewy bodies and is primarily present on phosphorylated synuclein; it therefore likely occurs after phosphorylated synuclein has deposited into Lewy bodies. This invariant pattern of specific phosphorylation, truncation, and ubiquitination is also present in the detergent-insoluble fraction of brain from patients with familial Parkinson's disease (synuclein A53T mutation) as well as multiple system atrophy, suggesting a common pathogenic pathway for both genetic and sporadic Lewy body diseases. These observations are most consistent with a model in which preferential accumulation of normally produced Ser-129 phosphorylated alpha-synuclein is the key event responsible for the formation of Lewy bodies in various Lewy body diseases.

SU‐FF‐J‐60: Effectiveness of MVCBCT for Patients with Implanted High‐Z Material

Purpose: To exploit the penetrability of high‐energy photons of Megavoltage ConeBeam CT system (MVCBCT) to obtain 3D images of the anatomy in presence of “Non‐compatible CT” objects made of high‐Z material. Methods and Material: A new MVCBCT system integrated onto a clinical Linac was used to acquire 3D images of different phantoms and patients. The grey levels of different electron density inserts (lung to dense bone) in a CT phantom were measured with and without the presence of a small Cerrobend rod (10×15mm) on a regular CT and with the MVCBCT. MVCBCT of a Rando phantom with implanted gold markers and tooth fillings as well as patients with dental implants or with gold markers implanted in prostate were also obtained. Results: The presence of the Cerrobend object in the CT phantom scanned with a regular CT creates strong artifacts around the object and disturbs the quality of the entire image, modifying the Hounsfield numbers by an average of 10%, even 15 cm away from the rod. The grey levels of the density inserts in the CT phantom remain unchanged within 3% in presence of the Cerrobend rod for MVCBCT. Similarly, gold markers appear with the typical star pattern artifact on CT images where a well‐defined dot is seen on MVCBCT. The tooth fillings in the MVCBCT Rando phantom do not disturb the soft tissue information around the teeth. Conclusion: Compared to the kV energy range, the presence of high‐Z material has relatively little impact on image quality of MVCBCT. Therefore, MVCBCT can complement missing information for planning or patient position verification purposes when high‐Z materials such as gold markers, tooth fillings, dental implants or hip prostheses are present. Clinical examples of each of these items will be presented. Conflict of Interest: Siemens supports this Research.

Plasma surface modification of Ti and TiAlV alloy

AbstractSurface modification of commercially pure Ti and of Ti6Al4V alloy samples was performed by plasma immersion ion implantation with 25 kV energy. Plasma was generated by RF discharge in air, in nitrogen, or in a mixture of nitrogen and methane. Treatment in air plasma produced an oxide layer on the surface without appreciable incorporation of nitrogen, as detected by XPS. Significant surface enrichment of aluminium was measured after air plasma treatment of Ti6Al4V, but no such segregation was observed after nitrogen plasma treatment. These effects are interpreted by involvement of thermodynamic driving forces. Development of rutile and a sub‐stoichiometric oxide were identified on Ti while no crystalline phases could be evaluated on the Ti6Al4V upon oxidation. The cubic TiN phase was found after nitrogen PIII treatment on both Ti and Ti6Al4V. Nanomechanical tests showed a significant increase in the hardness for Ti6Al4V after oxidizing PIII treatment in air. Considerable change in hardness could not be measured, however, after nitriding PIII treatments. Copyright © 2004 John Wiley & Sons, Ltd.

Charging System of ECRH High-Voltage Power Supply and its Control System

High-voltage power supply (HVPS) of Electron Cyclotron Resonance Heating (ECRH) for HT-7 and HT-7U is presently being constructed. The high voltage (100 kV) energy of HVPS is stored in the capacitor banks, and they can power one or two gyrotrons. All the operation of the charging system will be done by the control system, where the field signals are interfaced to programmable logic controller (PLC). The use of PLC not only simplifies the control system, but also enhances the reliability. The software written by using configuration software installed in the master computer allows for remote and multiple operator control, and the status and data information is also remotely available.

A performance comparison of flat-panel imager-based MV and kV cone-beam CT.

The use of cone-beam computed tomography (CBCT) has been proposed for guiding the delivery of radiation therapy, and investigators have examined the use of both kilovoltage (kV) and megavoltage (MV) x-ray beams in the development of such CBCT systems. In this paper, the inherent contrast and signal-to-noise ratio (SNR) performance for a variety of existing and hypothetical detectors for CBCT are investigated analytically as a function of imaging dose and object size. Theoretical predictions are compared to the results of experimental investigations employing largearea flat-panel imagers (FPIs) at kV and MV energies. Measurements were performed on two different FPI-based CBCT systems: a bench-top prototype incorporating an FPI and kV x-ray source (100 kVp x rays), and a system incorporating an FPI mounted on the gantry of a medical linear accelerator (6 MV x rays). The SNR in volume reconstructions was measured as a function of dose and found to agree reasonably with theoretical predictions. These results confirm the theoretically predicted advantages of employing kV energy x rays in imaging soft-tissue structures found in the human body. While MV CBCT may provide a valuable means of correcting 3D setup errors and may offer an advantage in terms of simplicity of mechanical integration with a linear accelerator (e.g., implementation in place of a portal imager), kV CBCT offers significant performance advantages in terms of image contrast and SNR per unit dose for visualization of soft-tissue structures. The relatively poor SNR performance at MV energies is primarily a result of the low x-ray quantum efficiencies (approximately a few percent or less) that are currently achieved with FPIs at high energies. Furthermore, kV CBCT with an FPI offers the potential of combined volumetric and radiographic/fluoroscopic imaging using the same device.

Small‐scale, “electrostatic” auroral structures and Alfvén waves

The results from a numerical investigation of the influence of the plasma micro‐turbulence on the structure and amplitude of macroscopic electromagnetic fields and currents inside the alfvénic field line resonance (FLR) layers are presented. Without analyzing an exact mechanism causing microturbulence, the plasma anomalous resistivity (AR) in the simplest form is included in the linear, reduced two‐fluid MHD/kinetic model, developed earlier to describe dispersive alfvénic FLRs in a dipole magnetic geometry. Computations show the following: (1) A fundamental FLR forming near L = 7.5 in the plasma with AR produces small‐scale, intense disturbances of E⊥ at low altitudes, just above the microturbulence layer, without any significant disturbances of B⊥ with the same spatial structure. (2) Plasma AR causes a parallel electric field inside the microturbulence layer, sufficient to accelerate electrons up to 1 kV energy over a distance ≈ 1000 km along the magnetic field line. (3) A numerical model of the alfvénic FLR, including the effect of the plasma AR even in the simplest form, reproduces the main features of the data measured by FAST satellite in the nightside auroral magnetosphere with remarkable exactness.

Scatter rejection by air gaps in diagnostic radiology. Calculations using a Monte Carlo collision density method and consideration of molecular interference in coherent scattering

The air gap technique is an old method for scatter rejection. It is still used in lung examinations and may be reconsidered for use in digital radiography. Using magnification techniques, for example in mammography, the air gap thereby introduced simultaneously yields scatter rejection. A Monte Carlo collision density method is exploited to investigate the physical parameters relevant to this technique. Radiation quantities of scattered photons at points behind a water slab both on and laterally displaced from the central axis are calculated and their dependence on field area, slab thickness, air gap length and detector type is derived. Values of `scatter-to-primary' ratios of the plane energy fluence (the energy imparted to a totally absorbing detector) are given for perpendicularly incident 30, 70 and 130 kV energy spectra, slab thicknesses of 0.05 and 0.2 m (30 kV: 0.05 m), air gaps of length 0.002 - 1.0 m and field areas from to . Contrast degradation factors are derived for both totally absorbing and thin detectors. The influence on the scatter-to-primary ratios of using divergent instead of parallel beams and of neglecting molecular interference in coherent scattering is analysed.

Design of a 400 MW power supply for a 60 T pulsed magnet

The National High Magnetic Field Laboratory at Los Alamos designs a magnet that produces magnetic fields of up to 60 T for as long as 100 ms. The power and energy to operate the magnet is provided by a 1430 MVA, 24 kV energy storage generator. Three modular design power supplies convert the AC-power produced by the generator into controlled DC-power needed by the three coil groups of the eight coil magnet. The modules are rated at 4 kV no-load voltage and 20 kA full-load current for up to 2 seconds once every hour, each including a 12-pulse, line-commutated rectifier designed to operate in the 66 Hz to 42 Hz pulse operation range of the generator. A short description of the overall 60 T/100 ms magnet system is given, followed by a detailed description of the the power converter system design.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ferrofluid viscometer: transient magnetic birefringence in crossed fields

A ferrofluid viscometer turns the viscosity determination into an optical birefringence measurement. Some colloidal magnetic particles are diluted in the studied medium. In a constant field, these ferrofluid particles behave as magnetic dipoles and experience a couple which tends to align these along the field: as each particle is optically anisotropic, the medium becomes birefringent. If the field is switched off, birefringence relaxes to zero with a characteristic time proportional to solution viscosity and to the particle volume. New measurements in crossed fields (static H c and pulsed H p) are here presented. Various relaxation regimes are explored depending on respective hierarchies of the Brownian energy kT, anisotropy energy of particles KV and magnetic energy μ H c. In these regimes the relaxation time becomes independent of particle size.

Experimental study of multiple frequency effects in a free electron laser amplifier

Measurements are presented of the gain and phase of a free electron laser (FEL) amplifier in the presence of a second, perturbing electromagnetic wave of different frequency. The studies are carried out in the microwave range of 7–11 GHz using a mildly relativistic electron beam of ∼160 kV energy and a current of ∼1 A. The presence of the perturbing wave causes serious deterioration of the FEL performance.

Wave profile modification (optical guiding) induced by free-electron laser interaction.

Modification of the transverse intensity profile of a single electromagnetic waveguide mode during the free-electron laser (FEL) interaction has been measured. This effect is the waveguide analog to free-space optical guiding. The studies were carried out at microwave frequencies (8--12 GHz) in a FEL with use of a mildly relativistic electron beam of \ensuremath{\simeq}200 kV energy and \ensuremath{\simeq}1.0 A current. The probing of the rf fields was accomplished by small electric dipole antennas inserted in the interaction region. The observed intensity profiles are compared with the measured FEL-induced phase shifts (wave refractive index).

Flashlamp probe source for nanosecond spectroscopic studies in the ultraviolet

Implementation of a high-pressure (7.5-atm) compact arc flashlamp as a probe source for ultraviolet spectroscopic measurements is described. Trigger circuitry is given which operates the lamp in simmered mode with discharge voltages up to 6 kV (energy 3.6 J) producing a 1-micros (FWHM) duration flash. Spectral outputs of lamps with argon, krypton, and xenon fill gasses are compared. Excellent UV output is obtained for both krypton and xenon with peak spectral output between 200 and 300 nm as measured by an optical multichannel analyzer. The lamps are inexpensive and have lifetimes of >100,000 flashes.

Radiation therapy in the conservative management of cancers of the low rectum and anal canal.

Radiotherapy has gained a prominent place in the management of cancer of the rectum and anus. In 221 cases of epidermoid carcinoma of the anal canal not involving more than three quarters of the circumference of the anal canal or the vaginal mucosa combined external beam using 60 Cobalt (30 Gy over 19 days) with an iridium implant boost (10-20 Gy) 2 months later resulted in a 5-year survival rate of 65%. Ninety percent of patients had normal anal function. A series of 281 patients with "early" adenocarcinoma of the rectum was treated by intracavitary irradiation (50 Kv energy, 100-150 Gy in 3-4 applications over 6 weeks). They were selected as being confined to the bowel wall without evidence of lymphadenopathy or anaplasia. Five-year survival and local recurrence rates were 78% and 5% respectively. A further series of 64 patients with more extensive "intermediate" type adenocarcinoma of the lower third of the rectum selected on the basis of age and poor surgical risk were treated by external beam 60 Cobalt irradiation (30 Gy over 12 days) followed by intracavitary and 192 iridium inplant after a two month interval. Of 44 patients treated more than 3 years previously the local control rate was 79.5% and survival 83%. These results suggest that radiotherapy might be applied to more extensive rectal carcinomas which otherwise would require total rectal excision.

Ion beam hydrogenation of polysilicon coated thermal oxide on silicon

Abstract The annealing of bare thermal oxide on silicon at 400–500°C in a hydrogen bearing gas results in a reduced density of states Nss at the substrate silicon/oxide interface. Treatments of this type have played a role in MOS processing schedules for several years. However, a similar approach applied to large areas (cm2) of poly-silicon coated oxide appears to be less effective in reducing Nss. This may be due to the polysilicon acting as a partially impermeable barrier which tends to starve the substrate/oxide interface of hydrogen. In the present work hydrogenation of 2-inch diameter, polysilicon coated wafers has been accomplished by hydrogen ion implantation. H2+ ions of 135 kV energy were implanted (to a dose of 1015 cm−2) through a 7000 A polysilicon coating into an underlying 1400 A SiO2 layer. The polysilicon was removed after 30-min anneals carried out in pure N2 at 300, 400 or 500°C. Aluminium dots, 1 mm in diameter were then deposited on to the oxide and high frequency (1 MHz) and quasistat...

Kinetic energy effects in mass spectrometry/mass spectrometry using a sector/quadrupole tandem instrument

Using a new hybrid (magnet/quadrupole) tandem mass spectrometer the effects of ion kinetic energy and target mass upon energy deposition have been investigated. In the range 1–100 eV, the degree of fragmentation is very sensitive to changes in the translational energy of the parent ion. Comparisons with MS/MS spectra recorded for the same ions (protonated 5-indanol, protonated diethylamine) using other instruments show that less significant changes in spectra occur in the kV energy range. Plots of branching ratios for competitive collision-induced dissociation channels against collision energy (1–100 eV) resemble, qualitatively, breakdown curves displaying ion abundances versus internal energy. In addition, comparisons of the effect of collision energy are made with spectral changes resulting from selection of the scattering angle in kV energy collisions. It is evident that translational energy selection is a counterpart, for spectrometers operating at low translational energy, of angle-resolved mass spectrometry.

A Low Inductance 120 KV Energy Storage Module

A low inductance 120 kV energy storage module has been developed at the Naval Research Laboratory. Fifty of these modules operating in parallel will form the 300 kJ capacitor bank for the fast reversal field of the SWAP experiment. The module comprises two 60 kV, 1.85 ?F capacitors operating as a modified Marx-type circuit. The self-inductance of the module, including the output switch and cable terminations, is approximately 110 nH. This arrangement has the advantage of using 60 kV power supplies, charging circuit and capacitors for a 120 kV capacitor bank and eliminates one of the series fast synchronized switches with a concomitant inductance reduction. The bank construction cost has been drastically reduced by the module physical arrangement. The second stage capacitor is mounted upside down directly on the first stage capacitor. The first stage capacitor therefore acts as both the support and insulator for the second stage capacitor whose case rises to 120 kV above ground at discharge.

The study of meta-stable positive ions with a double-focussing mass spectrometer: Part I. Description of the instrument used and its performance

The instrument used in these studies is the RMH-2 mass spectrometer, of Nier-Johnson geometry having 70° electrostatic and magnetic sectors with an ion radius of 500 mm in the electric and 400 mm in the magnetic sectors. When operated at 10 kV a resolving power of 90,000 has been obtained. Typical energy profiles of the ion beam at 5 kV energy are shown having widths at half-height of ±0.26 V. The focussed ion beam at the source slit is about 0.08 mm wide. Curves obtained when the accelerating voltage is scanned at fixed electric sector voltage show a “third” field-free region in this instrument in which decomposition of meta-stable ions can be studied.