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ABSTRACT: There are many instances where Monte Carlo simulation using the track-structure method for electron transport is necessary for the accurate analytical computation and estimation of dose and other tally data. Because of the large electron interaction cross-sections and highly anisotropic scattering behavior, the track-structure method requires an enormous amount of computation time. For microdosimetry, radiation biology and other applications involving small site and tally sizes, low electron energies or high-Z/low-Z material interfaces where the track-structure method is preferred, a computational device called a field-programmable gate array (FPGA) is capable of executing track-structure Monte Carlo electron-transport simulations as fast as or faster than a standard computer can complete an identical simulation using the condensed history (CH) technique. In this paper, data from FPGA-based track-structure electron-transport computations are presented for five test cases, from simple slab-style geometries to radiation biology applications involving electrons incident on endosteal bone surface cells. For the most complex test case presented, an FPGA is capable of evaluating track-structure electron-transport problems more than 500 times faster than a standard computer can perform the same track-structure simulation and with comparable accuracy.
Physics in Medicine and Biology 11/2008; 53(19):5539-53. · 2.83 Impact Factor
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J Vanamala,
A Glagolenko,
P Yang,
R J Carroll,
M E Murphy,
R A Newman, J R Ford,
L A Braby,
R S Chapkin,
N D Turner,
J R Lupton
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ABSTRACT: We have shown that dietary fish oil and pectin (FP) protects against radiation-enhanced colon cancer by upregulating apoptosis in colonic mucosa. To investigate the mechanism of action, we provided rats (n = 40) with diets containing the combination of FP or corn oil and cellulose (CC) prior to exposure to 1 Gy, 1 GeV/nucleon Fe-ion. All rats were injected with a colon-specific carcinogen, azoxymethane (AOM; 15 mg/kg), 10 and 17 days after irradiation. Levels of colonocyte apoptosis, prostaglandin E(2) (PGE(2)), PGE(3), microsomal prostaglandin E synthase-2 (mPGES-2), total beta-catenin, nuclear beta-catenin staining (%) and peroxisome proliferator-activated receptor delta (PPARdelta) expression were quantified 31 weeks after the last AOM injection. FP induced a higher (P < 0.01) apoptotic index in both treatment groups, which was associated with suppression (P < 0.05) of antiapoptotic mediators in the cyclooxygenase (COX) pathway (mPGES-2 and PGE(2)) and the Wnt/beta-catenin pathway [total beta-catenin and nuclear beta-catenin staining (%); P < 0.01] compared with the CC diet. Downregulation of COX and Wnt/beta-catenin pathways was associated with a concurrent suppression (P < 0.05) of PPARdelta levels in FP-fed rats. In addition, colonic mucosa from FP animals contained (P < 0.05) a proapoptotic, eicosapentaenoic acid-derived COX metabolite, PGE(3). These results indicate that FP enhances colonocyte apoptosis in AOM-alone and irradiated AOM rats, in part through the suppression of PPARdelta and PGE(2) and elevation of PGE(3). These data suggest that the dietary FP combination may be used as a possible countermeasure to colon carcinogenesis, as apoptosis is enhanced even when colonocytes are exposed to radiation and/or an alkylating agent.
Carcinogenesis 04/2008; 29(4):790-6. · 5.70 Impact Factor
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ABSTRACT: Advancements in parallel and cluster computing have made many complex Monte Carlo simulations possible in the past several years. Unfortunately, cluster computers are large, expensive, and still not fast enough to make the Monte Carlo technique useful for calculations requiring a near real-time evaluation period. For Monte Carlo simulations, a small computational unit called a Field Programmable Gate Array (FPGA) is capable of bringing the power of a large cluster computer into any personal computer (PC). Because an FPGA is capable of executing Monte Carlo simulations with a high degree of parallelism, a simulation run on a large FPGA can be executed at a much higher rate than an equivalent simulation on a modern single-processor desktop PC. In this paper, a simple radiation transport problem involving moderate energy photons incident on a three-dimensional target is discussed. By comparing the evaluation speed of this transport problem on a large FPGA to the evaluation speed of the same transport problem using standard computing techniques, it is shown that it is possible to accelerate Monte Carlo computations significantly using FPGAs. In fact, we have found that our simple photon transport test case can be evaluated in excess of 650 times faster on a large FPGA than on a 3.2 GHz Pentium-4 desktop PC running MCNP5.
IEEE Transactions on Nuclear Science 05/2006; · 1.45 Impact Factor
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ABSTRACT: We are using a novel perfusion system to examine the effects of radiation on a model respiratory tissue. Tracheas taken from young adult male Fischer 344 rats are embedded in a growth factor-enriched agarose matrix that is mounted in a special apparatus designed to allow growth medium to periodically wash the epithelial surface of the lumen. A comparison of the microarray expression profiles of freshly harvested tracheas and tracheas maintained in perfusion culture for 24 h shows no significant difference except for an increase in expression of a few metabolism- and surfactant-related genes. Perfusion culture samples exposed to 4 Gy of X rays show a lower than expected increase in expression for some cell cycle- and repair-related genes.
Radiation Research 11/2005; 164(4 Pt 2):487-92. · 2.68 Impact Factor
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J. Vanamala,
A. Glagolenko,
P Yang,
R J Carroll,
M E Murphy,
R A Newman, J R Ford,
L A Braby,
R S Chapkin,
N D Turner,
J R Lupton
[show abstract]
[hide abstract]
ABSTRACT: We have shown that dietary fish oil and pectin (FP) protects against radiation-enhanced colon cancer by upregulating apoptosis in colonic mucosa. To investigate the mechanism of action, we provided rats ( n = 40) with diets containing the combination of FP or corn oil and cellulose (CC) prior to exposure to 1 Gy, 1 GeV/nucleon Fe-ion. All rats were injected with a colon-specific carcinogen, azoxymethane (AOM; 15 mg/kg), 10 and 17 days after irradiation. Levels of colonocyte apoptosis, prostaglandin E 2 (PGE 2 ), PGE 3 , microsomal prostaglandin E synthase-2 (mPGES-2), total β-catenin, nuclear β-catenin staining (%) and peroxisome proliferator-activated receptor δ (PPARδ) expression were quantified 31 weeks after the last AOM injection. FP induced a higher ( P < 0.01) apoptotic index in both treatment groups, which was associated with suppression ( P < 0.05) of antiapoptotic mediators in the cyclooxygenase (COX) pathway (mPGES-2 and PGE 2 ) and the Wnt/β-catenin pathway [total β-catenin and nuclear β-catenin staining (%); P < 0.01] compared with the CC diet. Downregulation of COX and Wnt/β-catenin pathways was associated with a concurrent suppression ( P < 0.05) of PPARδ levels in FP-fed rats. In addition, colonic mucosa from FP animals contained ( P < 0.05) a proapoptotic, eicosapentaenoic acid-derived COX metabolite, PGE 3 . These results indicate that FP enhances colonocyte apoptosis in AOM-alone and irradiated AOM rats, in part through the suppression of PPARδ and PGE 2 and elevation of PGE 3 . These data suggest that the dietary FP combination may be used as a possible countermeasure to colon carcinogenesis, as apoptosis is enhanced even when colonocytes are exposed to radiation and/or an alkylating agent.
