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ABSTRACT: We consider the Directed Coulomb Explosion regime of ion acceleration from ultra-thin double layer (high Z/low Z) mass limited targets. In this regime the laser pulse evacuated the electrons from the irradiated spot and accelerates the remaining ion core in the direction of the laser pulse propagation. Then the moving ion core explodes due to the excess of positive charge forming a moving charge separation field that accelerates protons from the second layer. The utilization of the mass limited targets increases the effectiveness of the acceleration. It is also shown that different parameters of laser-target configuration should be chosen to ensure optimal acceleration by either linearly polarized or circularly polarized pulses. Comment: 8 pages, 9 figures
07/2010;
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ABSTRACT: Laser accelerated protons can be a complimentary source for treatment of oncological diseases to the existing hadron therapy facilities. We demonstrate how the protons, accelerated from near-critical density plasmas by laser pulses having relatively small power, reach energies which may be of interest for medical applications. When an intense laser pulse interacts with near-critical density plasma it makes a channel both in the electron and then in the ion density. The propagation of a laser pulse through such a self-generated channel is connected with the acceleration of electrons in the wake of a laser pulse and generation of strong moving electric and magnetic fields in the propagation channel. Upon exiting the plasma the magnetic field generates a quasi-static electric field that accelerates and collimates ions from a thin filament formed in the propagation channel. Two-dimensional Particle-in-Cell simulations show that a 100 TW laser pulse tightly focused on a near-critical density target is able to accelerate protons up to energy of 250 MeV. Scaling laws and optimal conditions for proton acceleration are established considering the energy depletion of the laser pulse. Comment: 25 pages, 8 figures
07/2010;
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T. Matsuoka,
S. Reed,
C. McGuffey,
S.S. Bulanov,
F. Dollar,
L. Willingale,
V. Chvykov,
G. Kalinchenko,
A. Brantov,
V. Yu. Bychenkov,
P. Rousseau,
V. Yanovsky, D.W. Litzenberg,
K. Krushelnick,
A. Maksimchuk
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ABSTRACT: The generation of energetic electron and proton beams was studied from the interaction of high intensity laser pulses with pre-drilled conical targets. These conical targets are laser machined onto flat targets using 7–180 µJ pulses whose axis of propagation is identical to that of the main high intensity pulse. This method significantly relaxes requirements for alignment of conical targets in systematic experimental investigations and also reduces the cost of target fabrication. These experiments showed that conical targets increase the electron beam charge by up to 44 ± 18% compared with flat targets. We also found greater electron beam divergence for conical targets than for flat targets, which was due to escaping electrons from the surface of the cone wall into the surrounding solid target region. In addition, the experiments showed similar maximum proton energies for both targets since the larger electron beam divergence balances the increase in electron beam charge for conical targets. 2D particle in cell simulations were consistent with the experimental results. Simulations for conical target without preplasma showed higher energy gain for heavy ions due to 'directed coulomb explosion'. This may be useful for medical applications or for ion beam fast ignition fusion.
Nuclear Fusion 05/2010; 50(5):055006. · 4.09 Impact Factor
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Medical Physics 07/2009; 36(6):2340; author reply 2341-2. · 2.83 Impact Factor
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Reed,
T. Matsuoka,
S. Bulanov,
V. Chvykov,
G. Kalintchenko,
R. Kodama,
P. Rousseau,
M. Tampo,
V. Yanovsky, D. W. Litzenberg,
K. Krushelnick and A. Maksimchuk
Applied Physics Letters 01/2009; 94:201117. · 3.84 Impact Factor
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S S Bulanov,
A Brantov,
V Yu Bychenkov,
V Chvykov,
G Kalinchenko,
T Matsuoka,
P Rousseau,
S Reed,
V Yanovsky, D W Litzenberg,
K Krushelnick,
A Maksimchuk
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ABSTRACT: We consider the effect of laser beam shaping on proton acceleration in the interaction of a tightly focused pulse with ultrathin double-layer solid targets in the regime of directed Coulomb explosion. In this regime, the heavy ions of the front layer are forced by the laser to expand predominantly in the direction of the pulse propagation, forming a moving longitudinal charge separation electric field, thus increasing the effectiveness of acceleration of second-layer protons. The utilization of beam shaping, namely, the use of flat-top beams, leads to more efficient proton acceleration due to the increase of the longitudinal field.
Physical Review E 09/2008; 78(2 Pt 2):026412. · 2.26 Impact Factor
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S. A. Reed,
S. S. Bulanov,
V. Chvykov,
A. Brantov,
V. Yu. Bychenkov,
G. Kalinchenko,
T. Matsuoka,
P. Rousseau,
V. Yanovsky, D. W. Litzenberg,
A. Maksimchuk
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ABSTRACT: The acceleration of protons to therapeutic energies of over 200 MeV by short‐pulse, high‐intensity lasers requires very high temporal intensity contrast. We describe improvements to the contrast ratio of the laser pulse produced by a multi‐terawatt chirped pulsed amplification (CPA) Ti:sapphire laser for the application of proton acceleration. The modified cross‐polarized wave generation (XPW) technique has been implemented on the Hercules laser at the University of Michigan to reject the low‐intensity amplified spontaneous emission (ASE) preceding the main laser pulse. We demonstrate that by using two BaF2 crystals, the XPW technique yields a 10−11 contrast ratio between the main peak and the ASE for a 50 TW laser system which can be maintained up to 500 TW. Such contrast may be sufficient for a preplasma‐free interaction of 225 TW laser pulses with sub‐micron thick foils at an intensity of ∼1022 W/cm2. Particle‐in‐cell (PIC) simulations were conducted under the anticipated experimental conditions: 6.75 J, 30 fs laser pulse without a prepulse, focused to a spot size of 1.2 microns (FWHM) on thin foils of varying thickness. The performed PIC simulations show that for a 0.2 μm thick hydrogen foil protons with energy up to 200 MeV can be produced. In the case of the two‐layer aluminum‐hydrogen foil, the maximum energy of accelerated protons is about 150 MeV, but the flux‐energy spectrum of the accelerated protons has a narrow peak at high energies, which may be more advantageous for medical applications. © 2006 American Institute of Physics
AIP Conference Proceedings. 11/2006; 877(1):430-436.
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ABSTRACT: To ensure target coverage during radiotherapy, all sources of geometric uncertainty in target position must be considered. Movement of the prostate due to breathing has not traditionally been considered in prostate radiotherapy. The purpose of this study is to report the influence of patient orientation and immobilization on prostate movement due to breathing.
Four patients had radiopaque markers implanted in the prostate. Fluoroscopy was performed in four different positions: prone in alpha cradle, prone with an aquaplast mold, supine on a flat table, and supine with a false table under the buttocks. Fluoroscopic movies were videotaped and digitized. Frames were analyzed using 2D-alignment software to determine the extent of movement of the prostate markers and the skeleton for each position during normal and deep breathing.
During normal breathing, maximal movement of the prostate markers was seen in the prone position (cranial-caudal [CC] range: 0.9-5.1 mm; anterior-posterior [AP] range: up to 3.5 mm). In the supine position, prostate movement during normal breathing was less than 1 mm in all directions. Deep breathing resulted in CC movements of 3.8-10.5 mm in the prone position (with and without an aquaplast mold). This range was reduced to 2.0-7.3 mm in the supine position and 0.5-2.1 mm with the use of the false table top. Deep breathing resulted in AP skeletal movements of 2.7-13.1 mm in the prone position, whereas AP skeletal movements in the supine position were negligible.
Ventilatory movement of the prostate is substantial in the prone position and is reduced in the supine position. The potential for breathing to influence prostate movement, and thus the dose delivered to the prostate and normal tissues, should be considered when positioning and planning patients for conformal irradiation.
International Journal of Radiation OncologyBiologyPhysics 10/2000; 48(2):319-23. · 4.11 Impact Factor
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ABSTRACT: We have previously reported that computer-controlled table repositioning can increase the reproducibility of patient setup in 2D using a megavoltage imager and bony anatomy as reference of position. This investigation was extended to daily 3D localization of soft tissue structures (“target of the day” treatment). Research to date has involved liver (under ventilatory immobilization) and prostate patients. Both protocols involve aligning the specified target to the reference position (determined via CT) using a diagnostic imager and alignment software. The liver position is determined by the position of the diaphragm and the spine, the prostate target is automatically localized and positioned through computer-based extraction of 3 implanted gold markers. Adjustments to correct target position are executed using a computer-controlled table. Measuring the residual offset of the target after the corrective action determines the accuracy of measurement and table adjustment, however this uncertainty is also influenced by organ motion between images. For the prostate protocol, the accuracy of the computer-controlled target repositioning is dx:0.56 mm (σ=3.69 mm), dy:2.74 mm (σ=3.87 mm), dz:2.38 mm (σ=4.5 mm) after 24 treatment fractions. For the liver protocol, the accuracy is dx:-0.7 mm (σ=1.67 mm), dy:-0.9 mm (σ=1.89 mm), dz:-1.0 mm (σ=3.18 mm) after 23 treatment fractions. The extra time necessary to image, align, and adjust the target has also been calculated. The average time for the localization and subsequent verification is 12.2 minutes (σ=5.7 min)
Engineering in Medicine and Biology Society, 2000. Proceedings of the 22nd Annual International Conference of the IEEE; 02/2000
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ABSTRACT: An algorithm is presented for determining how to adjust the actuators of a tilt and roll table. The algorithm is based on a geometrical model of the table, which was designed with six degrees of freedom. This design and algorithm allows complete translational and rotational corrections to be applied to the target volume position on a daily basis.
Medical Physics 12/1999; 26(12):2586-8. · 2.83 Impact Factor
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ABSTRACT: Proton radiotherapy is a powerful tool in the local control of cancer. The advantages of proton radiotherapy over gamma-ray therapy arise from the phenomenon known as the Bragg peak. This phenomenon enables large doses to be delivered to well-defined volumes while sparing surrounding healthy tissue. To fully realize the potential of this technique the location of the high-dose volume must be controlled very accurately. An imaging system was designed and tested to monitor the positron-emitting activity created by the beam as a means of verifying the beam's range, monitoring dose, and determining tissue composition. The prototype imaging system consists of 12 pairs of cylindrical BGO detectors shielded in lead. Each crystal was 1.9 cm in diameter, 5.0 cm long, and separated by 0.5 cm from other detectors in the row. These are arranged in two rows, 60 cm apart, with the proton beam and tissue phantoms half-way between and parallel to the detector rows. Experiments were conducted with 150 MeV continuous and macro-pulsed proton beams which had beam currents ranging from 0.14 nA to 1.75 nA. The production and decay of short-lived isotopes, 15O and 14O, was studied using 1 min irradiations with a continuous beam. These isotopes provide a significant signal on short time scales, making on-line imaging possible. Macro-pulsed beams, having a period of 10 s, were used to study on-line imaging and the production and decay of long-lived isotopes, 13N, 11C, and 18F. Decay data were acquired and on-line images were obtained between beam pulses and indicate that range verification is possible, for a 150 MeV beam, after one beam pulse, to within the 1.2 cm resolution limit of the imaging system. The dose delivered to the patient may also be monitored by observing the increase in the number of coincidence events detected between successive beam pulses. Over 80% of the initial positron-emitting activity is from 15O while the remainder is primarily 11C, 13N, 14O with traces of 18F, and 10C. Radioisotopic imaging may also be performed along the beam path by fitting decay data collected after the treatment is complete. Using this technique, it is shown that variations in elemental composition in inhomogenous treatment volumes may be identified and used to locate anatomic landmarks. Radioisotopic imaging also reveals that 14O is created well beyond the Bragg peak, apparently by secondary neutrons.
Medical Physics 07/1999; 26(6):992-1006. · 2.83 Impact Factor
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ABSTRACT: A tilt and roll device has been developed to add two additional degrees of freedom to an existing treatment table. This device allows computer-controlled rotational motion about the inferior-superior and left-right patient axes. The tilt and roll device comprises three supports between the tabletop and base. An automotive type universal joint welded to the end of a steel pipe supports the center of the table. Two computer-controlled linear electric actuators utilizing high accuracy stepping motors support the foot of table and control the tilt and roll of the tabletop. The current system meets or exceeds all pre-design specifications for precision, weight capacity, rigidity, and range of motion.
Medical Physics 10/1998; 25(9):1739-40. · 2.83 Impact Factor
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ABSTRACT: The image reconstruction algorithm and design considerations for
an annihilation gamma-ray coincidence detection camera are presented.
The imaging system is designed to provide fast, on-line monitoring of
the positron-emitting activity created by narrow gamma-ray, proton, or
heavy-ion radiotherapy beams in tissue for determining total dose,
performing range verification for charged particles, and for determining
the oxygen content as a function of depth. A model of the detection
system was developed and implemented using Monte Carlo techniques.
Simulations based on this model are compared with experimental results
from a prototype system and are used to study the detection efficiency
and imaging characteristics of the system, while parameters such as
scintillation crystal spacing, length, and separation are varied. In
addition the effects of intercrystal shielding, extended activity
distributions, and attenuation on detection efficiency and image
reconstruction are presented. Simulation results suggest that the
detection geometry which optimizes the sensitivity and spatial
resolution utilizes tightly packed, narrow, uncoupled scintillation
crystals with no intercrystal shielding. The one-dimensional
reconstruction algorithm requires that the angular acceptance be
minimized to reduce blurring for extended activity distributions. It is
also shown that the depth-of-interaction blurring effect present in
annular Positron Emission Tomography imaging systems may be removed
through the calibration procedure and the one-dimensional image
reconstruction algorithm used for this system
IEEE Transactions on Nuclear Science 09/1997; · 1.45 Impact Factor
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ABSTRACT: We have designed and built a modified positron emission tomography
(PET) imaging system for monitoring the dose delivered by proton and
γ ray radiotherapy beams. By measuring the amount and ratio of the
beam induced positron emitting activity, the dose distribution and
tissue composition may be determined. The system utilizes fast LeCroy
ECLine electronics and a VME multinode transputer based frontend.
Utilizing a transputer based filter, positron annihilation events
containing timing, energy, and position information will be filtered in
real time at event rates of up to 40 kHz. This will result in only valid
events being transmitted back to the host for further analysis and
display, reducing both storage media requirements and image
reconstruction time. At these rates, proton radiotherapy beams may be
monitored between beam pulses for online range verification. It will
also be possible to perform bloodflow studies on tumors using the
activity induced by a γ-ray radiotherapy beam. Future electronic
developments will allow event rates up to roughly 80 kHz. For both
treatment modalities, determination of the composition of tumors will
directly affect treatment planning through compensation for oxygen
enhancement effects to the dose
IEEE Transactions on Nuclear Science 03/1996; · 1.45 Impact Factor
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D.W. Litzenberg,
J.F. Bajema,
F.D. Becchetti,
J.A. Brown,
R.S. Raymond,
D.A. Roberts,
J. Caraher,
G. Hutchins,
R. Ronningen,
R. Smith,
M. Abbott
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ABSTRACT: Preliminary experiments have been performed which indicate that
online localization of proton radiotherapy beams in tissue is feasible.
Using a two-dimensional array of online sodium iodide (NaI) detectors it
is possible to perform real-time monitoring of the production of
positron emitting isotopes (mainly <sup>11</sup>C, <sup>13</sup>N, and
<sup>15</sup>O) as a function of depth with pulsed proton beams of
sufficiently low current. A commercial PET (positron emission
tomography) scanner was used off-line to verify range and activity
measurements. Results of range measurements using the two techniques are
in good agreement with the calculated range, to within their respective
resolutions
Nuclear Science Symposium and Medical Imaging Conference, 1992., Conference Record of the 1992 IEEE; 11/1992
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D.W. Litzenberg,
J.F. Bajema,
F.D. Becchetti,
D. A. Roberts,
R. Ronningen,
S. Van der Molen,
J. A. Brown,
R K Ten Haken,
J. Caraher,
C. Hazard,
M. Chawla
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ABSTRACT: We have performed experiments which indicate that online monitoring of proton radiotherapy beams in tissue is feasible. Using a two-dimensional array of on-line BGO detectors, it is possible to image the production of β<sup>+</sup>-emitting isotopes (mainly <sup>11 </sup>C, <sup>13</sup>N, and <sup>15</sup>O) as a function of tissue depth and time with pulsed proton beams of sufficiently low current. These measurements allow the dose and range of charged particle radiotherapy beams to be measured directly while the treatment is being delivered
Nuclear Science Symposium and Medical Imaging Conference, 1994., 1994 IEEE Conference Record;
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S A Reed,
T Matsuoka,
S S Bulanov,
V Chvykov,
A Brantov,
V Yu,
Bychenkov,
G Kalinchenko,
P Rousseau,
V Yanovsky, D W Litzenberg,
K Krushelnick,
A Maksimchuk
[show abstract]
[hide abstract]
ABSTRACT: Proton production from ultrathin foils using 3x10 20 W/cm 2 and 10 -11 ASE contrast is explored. Maximum proton energy and laser transmittance for ultrathin foils are studied to achieve ion acceleration within the Directed Coulomb Explosion regime.
