Application of the new MultiTrans SP3 radiation transport code in BNCT dose planning

Dose planning in boron neutron capture therapy (BNCT) is a complex problem and requires sophisticated numerical methods. In the framework of the Finnish BNCT project, new deterministic three-dimensional radiation transport code MultiTrans SP3 has been developed at VTT Chemical Technology, based on a novel application of the tree multigrid technique. To test the applicability of this new code in a realistic BNCT dose planning problem, cylindrical PMMA (polymethyl-methacrylate) phantom was chosen as a benchmark case. It is a convenient benchmark, as it has been modeled by several different codes, including well-known DORT and MCNP. Extensive measured data also exist. In this paper, a comparison of the new MultiTrans SP3 code with other methods is presented for the PMMA phantom case. Results show that the total neutron dose rate to ICRU adult brain calculated by the MultiTrans SP3 code differs less than 4% in 2 cm depth in phantom (in thermal maximum) from the DORT calculation. Results also show that the calculated 197Au(n,gamma) and 55Mn(n,gamma) reaction rates in 2 cm depth in phantom differ less than 4% and 1% from the measured values, respectively. However, the photon dose calculated by the MultiTrans SP3 code seems to be incorrect in this PMMA phantom case, which requires further studying. As expected, the deterministic MultiTrans SP3 code is over an order of magnitude faster than stochastic Monte Carlo codes (with similar resolution), thus providing a very efficient tool for BNCT dose planning.     

A noninvasive dose estimation system for clinical BNCT based on PG-SPECT--conceptual study and fundamental experiments using HPGe and CdTe semiconductor detectors

A noninvasive method for measuring the absorbed dose distribution during the administration of clinical boron neutron capture therapy (BNCT) using an online three-dimensional (3D) imaging system is presented. This system is designed to provide more accurate information for treatment planning and dosimetry. The single-photon emission computed tomography (SPECT) technique is combined with prompt gamma-ray analysis (PGA) to provide an ideal dose estimation system for BNCT. This system is termed PG-SPECT. The fundamental feasibility of the PG-SPECT system for BNCT is confirmed under the following conditions: (1) a voxel size of 1 x 1 x 1 cm3, comparable to the spatial resolution of our standard dosimetric technique using gold wire activation, where data are available for every 5-10 mm of wire length; (2) a reaction rate of 10B(n,alpha)7Li within the measurement volume is greater than 1.1 x l0(6) interactions/cm3/s, corresponding to a thermal neutron flux of 5 x 10(8) n/cm2/s and a 10B concentration of greater than 10 ppm for the deepest part of the tumor volume under typical BNCT clinical conditions; (3) statistical uncertainty of the count rate for 10B(n,alpha)7Li prompt gamma rays is 10% or less. The desirable characteristics of a detector for the PG-SPECT system were determined by basic experiments using both HPGe and CdTe semiconductor detectors. The CdTe semiconductor detector has the greatest potential for this system because of its compactness and simplicity of maintenance.     

Monte Carlo model of the Studsvik BNCT clinical beam: description and validation

The neutron beam at the Studsvik facility for boron neutron capture therapy (BNCT) and the validation of the related computational model developed for the MCNP-4B Monte Carlo code are presented. Several measurements performed at the epithermal neutron port used for clinical trials have been made in order to validate the Monte Carlo computational model. The good general agreement between the MCNP calculations and the experimental results has provided an adequate check of the calculation procedure. In particular, at the nominal reactor power of 1 MW, the calculated in-air epithermal neutron flux in the energy interval between 0.4 eV-10 keV is 3.24 x 10(9) n cm(-2) s(-1) (+/- 1.2% 1 std. dev.) while the measured value is 3.30 x 10(9) n cm(-20 s(-1) (+/- 5.0% 1 std. dev.). Furthermore, the calculated in-phantom thermal neutron flux, equal to 6.43 x 10(9) n cm(-2) s(-1) (+/- 1.0% 1 std. dev.), and the corresponding measured value of 6.33 X 10(9) n cm(-2) s(-1) (+/- 5.3% 1 std. dev.) agree within their respective uncertainties. The only statistically significant disagreement is a discrepancy of 39% between the MCNP calculations of the in-air photon kerma and the corresponding experimental value. Despite this, a quite acceptable overall in-phantom beam performance was obtained, with a maximum value of the therapeutic ratio (the ratio between the local tumor dose and the maximum healthy tissue dose) equal to 6.7. The described MCNP model of the Studsvik facility has been deemed adequate to evaluate further improvements in the beam design as well as to plan experimental work.     

Evaluation of correlation between dose and clinical outcomes in subcutaneous immunoglobulin replacement therapy

The importance of serum immunoglobulin (Ig)G concentration in IgG replacement therapy for primary immunodeficiency diseases is established in certain settings. Generally, IgG is infused via the intravenous (IVIG) or subcutaneous (SCIG) route. For IVIG infusion, published data demonstrate that higher IgG doses and trough levels provide patients with improved protection from infection. The same conclusions are not yet accepted for SCIG; data from two recent Phase III studies and a recent post-hoc analysis, however, suggest the same correlation between higher SCIG dose and serum IgG concentration and decreased incidence of infection seen with IVIG. Other measures of clinical efficacy have not been considered similarly. Thus, combined analyses of these and other published SCIG studies were performed; a full comparison of the 13 studies was, however, limited by non-standardized definitions and reporting. Despite these limitations, our analyses indicate that certain clinical outcomes improve at higher SCIG doses and associated higher serum IgG concentrations, and suggest that there might be opportunity to improve patient outcomes via SCIG dose adjustment.     

临床技能培训规范在妇科肿瘤学教学中的应用

临床技能培训是提高临床教学质量的重要内容,而建构针对性较强的临床技能培训规范则是提高妇科肿瘤学临床教学质量的关键环节。昆明医科大学第三附属医院妇瘤科,采用"知群体-建规范-重思路-提要求"的"四步走"策略进行培训,既有利于学生"三基"的融会贯通,激发学生学习妇科肿瘤学临床技能的主动性;又有利于任课教师在临床技能培训中拓展思维,调动带教的积极性。该方法为妇科肿瘤学临床技能规范培训提供了一种新途径。     

Overview of rabies in the Americas

Between 1993 and 2002, the number of human and canine rabies cases in the Americas Region fell by approximately 80%. There were 39 human cases in 2002, 63% of them transmitted by dogs. Furthermore, human rabies transmitted by wildlife, mostly by bats is a risk to inhabitants in many countries in the Region. The objective of this study is to describe this epidemiological situation based in the information received from the countries of the Americas Region in Regional Rabies Surveillance System in the Americas (SIRVERA) administrated by the Pan American Health Organization. This sharp reduction is attributable mainly to the control measures implemented by the countries of the Region, such as the mass vaccination of dogs and prophylactic treatment for people who have been exposed.     

Immunology south of the equator in the Americas

Despite a troubled economic and political past, a tradition of fundamental research in immunology and infectious diseases has been fostered in Argentina, Brazil and Chile, as well as in other South American countries.     

Relationship between the paired hearing centers of the dog's brain

Summary It may be concluded from these experiments that after unilateral extirpation of various parts or the whole of the auditory cortex and after total removal of the cortex of one hemisphere, there is no disturbance of conditioned excitation and conditioned inhibition in the symmetrically opposite region of the cortex. The results also demonstrate that the presence of the cortical auditory center of either hemisphere is sufficient to ensure find sound discrimination in dogs.(Presented by Active Member AN SSSR I. S. Beritashvili) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 56, No. 7, pp. 8–11, July, 1963     

Correlation between CT numbers and tissue parameters needed for Monte Carlo simulations of clinical dose distributions

We describe a new method to convert CT numbers into mass density and elemental weights of tissues required as input for dose calculations with Monte Carlo codes such as EGS4. As a first step, we calculate the CT numbers for 71 human tissues. To reduce the effort for the necessary fits of the CT numbers to mass density and elemental weights, we establish four sections on the CT number scale, each confined by selected tissues. Within each section, the mass density and elemental weights of the selected tissues are interpolated. For this purpose, functional relationships between the CT number and each of the tissue parameters, valid for media which are composed of only two components in varying proportions, are derived. Compared with conventional data fits, no loss of accuracy is accepted when using the interpolation functions. Assuming plausible values for the deviations of calculated and measured CT numbers, the mass density can be determined with an accuracy better than 0.04 g cm(-3). The weights of phosphorus and calcium can be determined with maximum uncertainties of 1 or 2.3 percentage points (pp) respectively. Similar values can be achieved for hydrogen (0.8 pp) and nitrogen (3 pp). For carbon and oxygen weights, errors up to 14 pp can occur. The influence of the elemental weights on the results of Monte Carlo dose calculations is investigated and discussed.     

Present situation and problems of the transportation of samples by clinical laboratory centers

Several preanalytical as well as analytical problems on quality control (QC) in clinical laboratory centers have been suspected. Participation in several control surveys and practical checks and guides including surveys ordered by the Bureau of Health and Welfare seem to have prompted the improvement of QC in the centers. However, preanalytical QC seems to be poorly recognized, and is much more difficult than analytical QC. In hospitals and various medical institutions, the following problems have been pointed; technical problems in sampling, sample care after collection (time, temperature, etc), serum separation and so on. The most difficult and unrecognized problems are sampling of urine and feces by patients themselves. Much more attention should be focused on these problems, and medical staff should be educated more on sampling and transportation.