Interaction between the biological effects of high- and low-LET radiation dose components in a mixed field exposure

Abstract

Purpose: The relative biological effectiveness of two epithermal neutron sources, a reactor based source at Studsvik, Sweden, and a proton accelerator-based source in Birmingham, UK, was studied in relation to the proportional absorbed dose distribution as a function of neutron energy. Evidence for any interactions between the effects of biological damage induced by high- and low-linear energy transfer (LET) dose components, in this ‘mixed field’ irradiation, was also examined

Materials and methods: Clonogenic survival in Chinese Hamster-derived V79 cells was used to assess biological effectiveness in this study. Cells were irradiated in suspension at 4°C at depths of 20, 35, 50 and 65 mm in a water phantom. This prevented the repair of sublethal damage, predominantly that produced by both incident and induced γ-rays in the field, over the variable periods of exposure required to irradiate cells with the same total absorbed dose. Cell survival, as a function of the absorbed radiation dose and depth in the phantom, was compared with Monte Carlo N-Particle (MCNP) calculations of the proportional absorbed dose distribution as a function of neutron energy for the two sources.

Results: In terms of the dose-related reduction in clonogenic cell survival, the epithermal neutron source at Studsvik was more biologically effective than the Birmingham source at all depths considered in the phantom. Although the contribution from the high-LET dose component was greater for the Studsvik source at 20 mm depth in the phantom, at greater depths the dose contribution from the high-LET dose component at Studsvik overlap with those for the Birmingham source. However, the most striking difference is in the fast neutron component to the dose of the two sources, neutron energies > 1 MeV were only associated with the Studsvik source. The relative biological effectiveness (RBE) of both sources declined slightly with depth in the phantom, as the total high-LET dose component declined. The maximum source RBE for Studsvik was 2.70 ± 0.50 at 20 mm; reduced to 2.10 ± 0.35 at depths of 50 and 65 mm. The corresponding values for Birmingham were 1.68 ± 0.25 and 1.31 ± 0.19, all values relate only to the surviving fraction of V79 cells at 37%, since RBE values are only applicable to the selected endpoint. Based on a dose reduction factor (DRF) of 1.0 for the total low-LET component to the absorbed dose, the RBE values for the high-LET dose component (fast neutrons and induced protons from the nitrogen capture reaction) was 14.5 and 7.05 for the Studsvik and Birmingham neutron sources, respectively. This is well outside the range of RBE historically reported values for V79 cells for the same level of cell survival for fast neutrons. The calculation of RBE values, based on the proportional absorbed dose distribution as a function of neutron energy, from historical data, and using a RBE of 1.8 for the dose from the nitrogen capture reaction, suggests RBE values for the total high-LET dose component of 3.1–2.8 and 2.5–2.0 for Studsvik and Birmingham, respectively, values again declining with depth in the phantom.

Conclusions: The overall biological effectiveness of the mixed field irradiation from an epithermal neutron sources depends on the composition and quality of the different dose components. The experimentally derived RBE values for the total high-LET dose components in these ‘mixed field’ irradiations are well in excess of historical data for fast neutrons. The difference between the historically expected and the observed RBE values is attributed to the interactions between the damage produced by high- and low-LET radiation.     

Changes in platelet volume,morphology and RNA content in subjects treated with haemodialysis

During haemodialysis treatment, blood flows from the body to the extracorporeal circuit and vice versa. In this study, pathophysiological defects in platelets indicated by alterations in RNA content and aberrations in platelet volume and morphology are detected before and during haemodialysis treatment. In subjects receiving haemodialysis treatment, qualitative interpretation of platelet characteristics with application of light microscopic evaluation reveals only 19±11?% of platelets with appropriate staining density of the granule‐containing cytoplasm. On the contrary, a reference group of apparently healthy subjects shows 70±12?% platelets with appropriate staining density of the granule‐containing cytoplasm. During haemodialysis treatment, mean values for platelet volume, platelet distribution width and platelet large cell ratio demonstrate a tendency to decrease by 10?%, 11?% and 6?%, respectively, from the mean initial value to the value at t = 150?min. Reduction of the platelet volume parameters just mentioned is hypothesized to be due to platelet degranulation as a result of platelet activation.     

Pro-inflammatory interleukins in patients operated on for proximal femur fracture

Abstract

Objectives. The aims of this study were to measure plasma IL 6 and IL 8 in patients with proximal femoral fracture (PFF) during the early phases of trauma and operation and to find out if there was any correlation between these ILs and the post-operative lower limb oedema. Material and methods. Thirty patients with a median age of 81 years were grouped into pertrochanteric fracture (PTF) (n = 16) and femoral cervical fracture (FCF) (n = 14). Plasma interleukin levels were determined on blood samples obtained from the common femoral vein, immediately after hospital admission, 1 h before operation, and post-operatively at 1, 6, 12, 24, 48 h and on the 7th day. Thigh oedema was calculated by the frustum method. Results. In the patients with PTF, maximum mean plasma IL-6 and IL-8 values were found, respectively at 24 h (45.12 pg/mL) and 6 hours (21.7 pg/mL) postoperatively. Whereas, in the patients with FCF, it was respectively, at 12 h (33.1 pg/mL) and 6 h (17.0 pg/mL), for IL-6 and IL-8 post operatively. The patients with PTF and FCF had respectively, 34.1% and 27.4% more thigh oedema in the operated limb on the 7th post-operative day as compared to the preoperative oedema volume (p<0.001). No significant correlation could be found between the plasma IL-6 and IL-8 levels and oedema in the operated limb. Conclusion: Increased levels of IL 6 and IL 8 suggest ongoing inflammation.     

Distribution of thromboembolism in valvular versus non-valvular atrial fibrillation

The most feared consequence of atrial fibrillation (AF) is thromboembolism, either to the brain causing stroke or to the non-cerebral circulation. Valvular atrial fibrillation (VAF) and non-valvular atrial fibrillation (NVAF) differ not only by morphological substrate of arrhythmia but also by the rate of thromboembolic complications, predisposing factors and destination of embolism. In the setting of VAF, there is a higher risk of thromboembolism and a higher prevalence of thrombus location within the body of the left atrium compared to NVAF. VAF is also associated with a proportionally higher propensity for non-cerebral thromboemboli than in NVAF. The distribution of non-cerebral thromboemboli appears to be similar in VAF and NVAF; however, more research needs to be done in this area, particularly with regard to VAF.     

Production of influenza pseudotyped lentiviral particles and their use in influenza research and diagnosis: an update

Pseudotyped viral particles are being used as safe surrogates to mimic the structure and surface of many viruses, including highly pathogenic viruses such as avian influenza H5N1, to investigate biological functions mediated by the envelope proteins derived from these viruses. The first part of this article evaluates and discusses the differences in the production and characterization of influenza pseudoparticles. The second part focuses on the applications that such a flexible tool can provide in modern influenza research, in particular in the fields of drug discovery, molecular biology and diagnosis.     

PCR for detection of respiratory viruses: seasonal variations of virus infections

Real-time PCR and related methods have revolutionized the laboratory diagnosis of viral respiratory infections because of their high detection sensitivity, rapidness and potential for simultaneous detection of 15 or more respiratory agents. Results from studies with this diagnostic modality have significantly expanded our knowledge about the seasonality of viral respiratory diseases, pinpointed the difficulties to make a reliable etiologic diagnosis without the aid of an unbiased multiplex molecular assay for respiratory viruses, and revealed previously unknown details as to possible infections with multiple agents as aggravating factors. The scope of this article is to review and discuss this new knowledge and its implications for diagnostic strategies and other measures essential for the clinical management of respiratory viral infections and for epidemiological surveillance of seasonal respiratory infections.     

3D-Quantitative evaluation of a rigid seating system and dynamic seating system using 3D movement analysis in individuals with dystonic tetraparesis

To improve postural stability in individuals with dystonic cerebral palsy, the concept of a dynamic seat has been suggested as a potential solution. An experimental set-up for the acquisition of movement during extensor thrusts while sitting on a seating system was defined and applied on a group of dystonic individuals, to compare a dynamic versus a rigid seat system, using quantitative movement analysis. The seating system in dynamic configuration is able to reduce the extensor thrust experienced by the consumers, as well as to increase range of motion in the anterior–posterior direction, limiting the sliding down of trunk and showing better upper limb smoothness during extensor thrusts. The procedures used in this study appear to provide a useful tool for better understanding how the concept of a dynamic back in a seat system may affect and influence position and stability of individuals with dystonia on the seat system.     

经皮椎体成形术中斜面针应用效果观察

目的探讨斜面穿刺针和菱形穿刺针在经皮椎体成形手术中的应用方法和优势.方法解离成人25~40岁尸体腰椎1~5椎节(L1~5),共计10×5节,完成各椎节骨含量检测,符合骨含量减少或轻度骨质疏松标准.分别应用斜面穿刺针和菱形穿刺针完成在尸椎上经皮椎体成形术手术模拟操作.手术后行椎体正侧位拍片,使用简易的学生用角度尺和直尺测量穿刺针道偏转数据;观察CT断层扫描下骨水泥在椎体内的分布特点.针道偏转计量数据应用统计软件完成统计分析.结果斜面穿刺针在椎体骨质内发生背向斜面的偏转,偏转角度为(1.83±0.2)°至(3.30±0.3)°.菱形穿刺针在椎体内未发生针道偏转.骨密度值与修正后偏转角度经Pearson相关分析结果显示:2者存在负相关关系,r=-0.991,P=0.001.CT断层扫描显示:自斜面穿刺针之斜面溢出的骨水泥团分布呈现为偏向分布的类椭圆体,随着针体旋转调整,可控制骨水泥注射方向和分布区域;骨水泥自菱形穿刺针顶端溢出后,直接冲向针尖远端,成为类球形体,旋转针体后,不能调整骨水泥注射方向和分布区域.结论实验观察表明,应用斜面穿刺针具实施经皮椎体成形手术,可以在进针和注射过程中充分发挥其所具有天然的设计优势,获得精确的进针路径控制和骨水泥在靶区内的填充控制效果.     

Comparative study of dose distribution between carbon ion radiotherapy and photon radiotherapy for head and neck tumor

PURPOSE: A comparative treatment planning study has been performed between carbon ion radiotherapy (CIRT) and photon radiotherapy [three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT)] to assess the potential improvements and limitations that could result for locally advanced, nonresectable head and neck tumors. MATERIALS AND METHODS: Seven patients, originally treated with CIRT, were randomly selected for the comparative study. The evaluations analyzed using dose-volume histogram parameters, conformity index, inhomogeneity coefficient, and dose to the organs at risk (OARs). RESULTS: The mean conformity index was 1.46, 1.43, and 1.22 for 3D-CRT, IMRT, and CIRT, respectively. The mean inhomogeneity coefficient was 0.05, 0.07, and 0.02 for 3D-CRT, IMRT, and CIRT respectively. Photon plans resulted in greater volumes of normal tissues at 10% to 95% isodose levels compared with the corresponding carbon ion plans where the volumes increased by a factor of 1.2 to 2.7 for 3D-CRT and 1.2 to 2.0 for IMRT. CONCLUSION: CIRT has the potential to improve the target dose conformity, inhomogeneity coefficient, and OAR sparing when compared with 3D-CRT and IMRT. Compared with 3D-CRT, normal tissue exposure was reduced mainly in the mid-to low-isodose levels using IMRT. Additional improvement was obtained using CIRT.