Investigating magnetic field dose effects in small animals: a Monte Carlo study

Purpose: In MRI-linac treatments, radiation dose distributions are affected by magnetic fields, especially at high-density/low-density interfaces. Radiobiological consequences of magnetic field dose effects are presently unknown and preclinical studies are desirable. This study investigates the optimal combination of beam energy and magnetic field strength needed for preclinical murine studies.Methods: The Monte Carlo code MCNP6 was used to simulate the effects of a magnetic field when irradiating a mouse lung phantom with a 1.0 cm × 1.0 cm photon beam. Magnetic field dose effects were examined using various beam energies (225 kVp, 662 keV [Cs-137], and 1.25MeV [Co-60]) and magnetic field strengths (0.75 T, 1.5 T, and 3 T). The resulting dose distributions were compared to Monte Carlo results for humans with various field sizes and patient geometries using a 6MV/1.5T MRI-linac.Results: In human simulations, the addition of a 1.5 T magnetic field causes an average dose increase of 49% (range: 36% - 60%) to lung at the soft tissue-lung interface and an average dose decrease of 30% (range: 25% - 36%) at the lung-soft tissue interface. In mouse simulations, no magnetic field dose effects were seen with the 225 kVp beam. The dose increase for the Cs-137 beam was 12%, 33%, and 49% for 0.75 T, 1.5 T, and 3.0 T magnetic fields, respectively while the dose decrease was 7%, 23%, and 33%. For the Co-60 beam the dose increase was 14%, 45%, and 41%, and the dose decrease was 18%, 35%, and 35%.Conclusion: The magnetic field dose effects observed in mouse phantoms using a Co-60 beam with 1.5 T or 3 T fields or a Cs-137 beam with a 3T field fall within the range seen in humans treated with an MRI-linac. These irradiator/magnet combinations are therefore suitable for preclinical studies investigating potential biological effects of delivering radiation therapy in the presence of a magnetic field.---------------------------Cite this article as: Rubinstein A, Guindani M, Hazle JD, Court LE. Investigating magnetic field dose effects in small animals: a Monte Carlo study. Int J Cancer Ther Oncol 2014; 2(2):020233. DOI: 10.14319/ijcto.0202.3

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Shop Talk by Frank Santos (page 1) You\u27ve Come a Long Way, Lawn-Mower Pusher by Alan B. Albin (2) In The Eyes of the Laymen by Eugene P. Elcik (2) The Importance of Water Management by Fred V. Grau (A-1) Automatic Irrigation Systems Integrated with Pumping Systems by Michael O. Mattwell (A-5) Installation of a Complete Water Source and Automatic System by Richard C. Blake (A-19) How the Soil Conservation Service Can Help in Golf Course Management by Christopher G. Mousitakis (A-22) Our Shrinking Environment by Haim B. Gunner (A-24) Pesticides\u27 Dilemma - Emotion vs. Science by Allen H. Morgan (A-28) Effects of Turf Grasses and Trees in Neutralizing Waste Water by William E. Sopper (A-34) Unsolved and New Problems Developing in Golf Course Management by Alexander M. Radko (A-44) Coming of the Conglomerate Director of Golf Courses by Edmund B. Ault (A-48) Aquatic Weed Control by John E. Gallagher (A-52) What Project Apollo Has Done for Golf and Golf Course Architecture by Mal Purdy (A-54) Maintenance of Grass Tennis Courts by Wayne Zoppo (A-59) Diseases of Ornametnals Growing in Turf Areas by R.E. Partyka (A-62) Control of Turf Insects by John C. Schread (A-65) Lime for Turf by Henry W. Indyk (A-68) How to Stop Guessing When You Buy Seed by Dale Kern (A-71) Broad Aspects of Turf Grass Culture Other Than Golf Courses by Geoffrey S. Cornish (A-79) Establishing and Maintaining Turf int he national Capitol Parks by Alton E. Rabbitt (A-81) Preventive Maintenance on Small One Cylinder Air Cooled Engine by F. W. Hazle (A-85) Top Fairway Mower Performance by James R. Maloney (A-95) Grinding Reel Type Mowers by Ray Christopherson (A-99

Infection Prevention and Control Guideline for Cystic Fibrosis: 2013 Update

The 2013 Infection Prevention and Control (IP&C) Guideline for Cystic Fibrosis (CF) was commissioned by the CF Foundation as an update of the 2003 Infection Control Guideline for CF. During the past decade, new knowledge and new challenges provided the following rationale to develop updated IP&C strategies for this unique population: 1. The need to integrate relevant recommendations from evidence-based guidelines published since 2003 into IP&C practices for CF . These included guidelines from the Centers for Disease Control and Prevention (CDC)/Healthcare Infection Control Practices Advisory Committee (HICPAC), the World Health Organization (WHO), and key professional societies, including the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA). During the past decade, new evidence has led to a renewed emphasis on source containment of potential pathogens and the role played by the contaminated healthcare environment in the transmission of infectious agents. Furthermore, an increased understanding of the importance of the application of implementation science, monitoring adherence, and feedback principles has been shown to increase the effectiveness of IP&C guideline recommendations. 2. Experience with emerging pathogens in the non-CF population has expanded our understanding of droplet transmission of respiratory pathogens and can inform IP&C strategies for CF . These pathogens include severe acute respiratory syndrome coronavirus and the 2009 influenza A H1N1. Lessons learned about preventing transmission of methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant gram-negative pathogens in non-CF patient populations also can inform IP&C strategies for CF

In vivo magnetic resonance studies of experimental liver disease: Carbon tetrachloride hepatotoxicity and alcohol-induced fatty liver in rat

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) were used to non-invasively determine if cirrhosis induced by carbon tetrachloride (CCl\sb4) and phospholipase-D (PLD) could be distinguished from fatty infiltration in rat. MRS localization and water suppression methods were developed, implemented and evaluated in terms of their application to in vivo proton NMR studies of experimental liver disease. MRS studies were also performed to quantitate fatty infiltration resulting from carbon tetrachloride (CCl\sb4) or alcohol (ethanol) administration and the MRS results were confirmed using biochemical total lipid analysis and histology. \rm T\sb1 weighted MR images acquired weekly, 48 hours post administration, demonstrated only a slight increase in overall liver intensity with CCl\sb4 or alcohol administration, which is consistent with previously reported results. The MR images were able to detect nodules resulting from CCl\sb4+PLD induced cirrhosis as hypointense regions, also consistent with previous reports. Localized in vivo water and lipid proton \rm T\sb1 relaxation time measurements were performed and demonstrated no statistically significant trends for either agent. In vivo proton spectra were also acquired using stimulated echo techniques to quantitatively follow the changes in liver lipid content. The changes in liver lipid content observed using MRS were verified by total lipid analysis using the Folch technique and histology. The in vivo \rm T\sb1 and lipid quantification data str inconsistent with the previous hypothesis that the changes in \rm T\sb1 weighted images were the result of increased free water content and, therefore, increased water \rm T\sb1 relaxation times. These data indicate that the long term changes are more likely the result of changes in lipid content. The data are also shown to agree with the accepted hypothesis that the time course and mechanism of fatty infiltration are different for CCl\sb4 and alcohol. The hypothesis that the lipids resulting from either protocol are from the same lipid fraction(s), presumably triglycerides, is also supported. And lastly, on the basis of MR images and quantitative MRS lipid information, it was shown that cirrhosis could be distinguished from fatty infiltration

Investigating magnetic field dose effects in small animals: a Monte Carlo study

Purpose: In MRI-linac treatments, radiation dose distributions are affected by magnetic fields, especially at high-density/low-density interfaces. Radiobiological consequences of magnetic field dose effects are presently unknown and preclinical studies are desirable. This study investigates the optimal combination of beam energy and magnetic field strength needed for preclinical murine studies.Methods: The Monte Carlo code MCNP6 was used to simulate the effects of a magnetic field when irradiating a mouse lung phantom with a 1.0 cm × 1.0 cm photon beam. Magnetic field dose effects were examined using various beam energies (225 kVp, 662 keV [Cs-137], and 1.25MeV [Co-60]) and magnetic field strengths (0.75 T, 1.5 T, and 3 T). The resulting dose distributions were compared to Monte Carlo results for humans with various field sizes and patient geometries using a 6MV/1.5T MRI-linac.Results: In human simulations, the addition of a 1.5 T magnetic field causes an average dose increase of 49% (range: 36% - 60%) to lung at the soft tissue-lung interface and an average dose decrease of 30% (range: 25% - 36%) at the lung-soft tissue interface. In mouse simulations, no magnetic field dose effects were seen with the 225 kVp beam. The dose increase for the Cs-137 beam was 12%, 33%, and 49% for 0.75 T, 1.5 T, and 3.0 T magnetic fields, respectively while the dose decrease was 7%, 23%, and 33%. For the Co-60 beam the dose increase was 14%, 45%, and 41%, and the dose decrease was 18%, 35%, and 35%.Conclusion: The magnetic field dose effects observed in mouse phantoms using a Co-60 beam with 1.5 T or 3 T fields or a Cs-137 beam with a 3T field fall within the range seen in humans treated with an MRI-linac. These irradiator/magnet combinations are therefore suitable for preclinical studies investigating potential biological effects of delivering radiation therapy in the presence of a magnetic field.---------------------------Cite this article as: Rubinstein A, Guindani M, Hazle JD, Court LE. Investigating magnetic field dose effects in small animals: a Monte Carlo study. Int J Cancer Ther Oncol 2014; 2(2):020233. DOI: 10.14319/ijcto.0202.33</p

Theoretical model for laser ablation outcome predictions in brain: calibration and validation on clinical MR thermometry images

<p><b>Purpose:</b> Neurosurgical laser ablation is experiencing a renaissance. Computational tools for ablation planning aim to further improve the intervention. Here, global optimisation and inverse problems are demonstrated to train a model that predicts maximum laser ablation extent.</p> <p><b>Methods:</b> A closed-form steady state model is trained on and then subsequently compared to <i>N</i> = 20 retrospective clinical MR thermometry datasets. Dice similarity coefficient (DSC) is calculated to provide a measure of region overlap between the 57 °C isotherms of the thermometry data and the model-predicted ablation regions; 57 °C is a tissue death surrogate at thermal steady state. A global optimisation scheme samples the dominant model parameter sensitivities, blood perfusion (<i>ω</i>) and optical parameter (<i>μ</i>_eff) values, throughout a parameter space totalling 11 440 value-pairs. This represents a lookup table of <i>μ</i>_eff–<i>ω</i> pairs with the corresponding DSC value for each patient dataset. The <i>μ</i>_eff–<i>ω</i> pair with the maximum DSC calibrates the model parameters, maximising predictive value for each patient. Finally, leave-one-out cross-validation with global optimisation information trains the model on the entire clinical dataset, and compares against the model naïvely using literature values for <i>ω</i> and <i>μ</i>_eff.</p> <p><b>Results:</b> When using naïve literature values, the model’s mean DSC is 0.67 whereas the calibrated model produces 0.82 during cross-validation, an improvement of 0.15 in overlap with the patient data. The 95% confidence interval of the mean difference is 0.083–0.23 (<i>p</i> < 0.001).</p> <p><b>Conclusions:</b> During cross-validation, the calibrated model is superior to the naïve model as measured by DSC, with +22% mean prediction accuracy. Calibration empowers a relatively simple model to become more predictive.</p

Copper Sulfide Nanoparticles As a New Class of Photoacoustic Contrast Agent for Deep Tissue Imaging at 1064 nm

Photoacoustic tomography (PAT) is an emerging molecular imaging modality. Here, we demonstrate use of semiconductor copper sulfide nanoparticles (CuS NPs) for PAT with an Nd:YAG laser at a wavelength of 1064 nm. CuS NPs allowed visualization of mouse brain after intracranial injection, rat lymph nodes 12 mm below the skin after interstitial injection, and CuS NP-containing agarose gel embedded in chicken breast muscle at a depth of ∼5 cm. This imaging approach has great potential for molecular imaging of breast cancer