放射治疗中的RBE

近几十年来,放射治疗工具不断得到重大发展,剂量分布达到理想水平。高LET射线已在许多国家广泛应用,有希望的负π介子束也正在一些国家开始运用于临床。放射治疗正在酝酿着新的进展。从放射治疗的发展基础——放射物理学和放射生物学来看,放射治疗医生对放射物理学的要求几乎已满足,而今后放射治疗取得进展的关键主要在于放射生物学。放射治疗是以辐射为工具,通过辐射能作用于生物体产生生物效应而达到治疗疾病的目的。我们不仅要掌握工具的物理性能,更重要的是认识其产生的生物     

中子治疗中的RBE值

目前临床上使用的中子RBE值3.0,不仅不正确而且是危险的。RBE与光子或中子的每次剂量有关,并且存在织织差异性。不能用单次剂量所得到的RBE转换成分割治疗计划。Hammersmith在对病人和动物实验中确立的4周12次分割,每次130rad的中子RBE值确实是3.0,但这仅是就急性皮肤反应而言。这个值已用于临床,通常用来将适当的光子剂量转换成预计的中子剂量。临床治疗中的每次剂量对于中枢神经系统特别高。用中子治疗的实验资料可以解释使用RBE值3.0的危险性是没有注意到每剂量,组织差异性以及同临床所见的脊髓耐受水平的比较。临床上使用的RBE值通常与可以接受的光子剂量划成坐标图。那么中子的限制     

密集电离辐射(高LET)的RBE和细胞的恢复

放疗中利用密集电离辐射的优点是辐射能量减弱以局部分布为主,这样就能使原发损伤效应升高,减少分次照射时亚致死性损伤细胞的恢复,即密集电离辐射的RBE大,损伤细胞恢复的少,甚至不可能恢复。随着辐射平均线性能量转换(LET)的增高,哺乳动物细胞的存活曲线由指数型分裂变为S型分裂,且亚致死性损伤细胞的恢复力减少,和以放射损伤恢复力相区分的细菌菌株的放射敏感性的差异性消失,许多抗放药效果变差。     

125IUdR掺入B16黑色素瘤细胞DNA的内照射累积吸收剂量估算及RBE

本文以微核率为生物终点,以⁶⁰Coγ 射线为基准辐射,在研究了¹²⁵IUdR掺人动力学的基础上,对¹²⁵IudR掺入B₁₀黑色素瘤细胞DNA的内照射累积吸收剂量和RBE进行了估算,结果表明:¹²⁵IUdR掺入率分别和标记活度、标记时间呈线性正比关系,肿瘤细胞总微核率和微核细胞率均随¹²⁵IUdR掺入率增高而增高,回归方程分别为Y₁=0.0395+0.029X,Y₂=0.0776+0.021X,与⁶⁰Coγ 射线相比RBE分别为4.9和5。该研究为在常温下计算¹²⁵IUdR的RBE作了尝试。     

热中子和~(10)B(n,α)~7Li反应对B-16黑色素瘤细胞的RBE

由于新的~(10)B化合物的合成,使热中子俘获疗法治疗恶性肿瘤又成为可能。用热中子俘获处理法已经证明,~(10)B-氯丙嗪十一烷基氢化十二硼(~(10)B-CPZ)和~(10)B-对硼基苯丙氨酸(~(10)B-BPA)对黑色素瘤细胞有特殊的杀伤作用。本文利用肿瘤非特异的~(10)B-硼酸(~(10)B-BA)处理培养的黑色素瘤细胞进行细胞存活试验,确定热中子和~(10)B(n,α)~7Li反应的相对生物效应,并估计出~(10)B-化合物在细胞中的蓄积。     

利用小鼠空肠腺管细胞生存率测定高与低LET射线每次低剂量分割时相对生物学效应(RBE)

在设计治疗计划时,对于任何一种新的射线,必须知道它的相对生物学效应。50年代末60年代初,高能量光子及电子线应用于放射治疗中,有关测定这些射线相对生物学效应及其与普通 X 线相比较的工作已经进行。但大多数 RBE 值是从单次高剂量照射中推导而来。对于临床经常使用的分割治疗,了解其 RBE 值是必要的。这是由于对高 LET(线样能量转换)射线其 RBE 值随着每次分割剂     

The Effect of 238Pu α-particles on the Mouse Fibroblast Cell Line C3H 10T1/2: Characterization of Source and RBE for Cell Survival

Summary

Considerable interest has been aroused in recent years by reports that the transforming and carcinogenic effectiveness of low doses of high LET radiations can be increased by reducing the dose rate, especially for transformation of 10T1/2 cells in vitro by fission-spectrum neutrons. We report on conditions which have been established for irradiation of 10T1/2 cells with high LET monoenergetic α-particles (energy of 3·2 MeV, LET of 124 keV μm^?1) from ²³⁸Pu. The α-particle irradiator allows convenient irradiation of multiple dishes of cells at selectable high or low dose rates and temperatures. The survival curves of irradiated cells showed that the mean lethal dose of α-particles was 0·6 Gy and corresponded to an RBE, at high dose rates, of 7·9 at 80 per cent survival and 4·6 at 5 per cent survival, relative to ⁶⁰Co γ-rays. The mean areas of the 10T1/2 nuclei, perpendicular to the incident α-particles, was measured as 201 μm², from which it follows that, on average, only one in six of the α-particle traversals through a cell nucleus is lethal. Under the well-characterized conditions of these experiments the event frequency of α-particle traversals through cell nuclei is 9·8 Gy^?1.     

The general relation between tissue response to x-radiation (α/β-values) and the relative biological effectiveness (RBE) of protons: Prediction by the Katz track-structure model

Purpose : Experimental data suggest that the relative biological effectiveness (RBE) of protons compared to x-rays may be determined by the α / β -ratio of the x-ray survival curve. The data are referring to the centre of a spread-out Bragg peak (SOBP) formed to deliver a homogeneous dose to the tumour by modulating the proton energy. In an effort to explore the basis for this observation, calculations were performed to investigate the response of different biological targets through a range of proton energies and doses. Materials and methods : To describe the x-ray survival curve, the parameters of the linear-quadratic equation, α and β, as well as those of the multi-target/single-hit equation, n and D 0, were considered. These parameters were varied to investigate the RBE using the Katz track-structure model. Known cell line characterizations, as well as different hypothetical cells assuming different α / β -ratios but similar target size parameters in the framework of the track-structure theory, were considered. Results : The RBE was found to increase with increasing α / β when the parameter n was varied, but to decrease with increasing α / β when D 0 was varied. This held when all other radiosensitivity parameters were assumed to stay constant. Thus, the RBE cannot be predicted by the α / β -ratio alone. Conclusions : Although there is no direct correlation between the proton RBE and the parameters describing the x-ray survival curve, the track-structure model predicts a tendency for late-responding tissues (low α / β) to have higher RBE values than early-responding tissues (high α / β) . These calculations reinforce the experimental findings, but also strongly suggest that there are circumstances in which the tendency for RBE to increase with increasing α / β does not occur, or even could be reversed.     

An analysis of the murder of women in a 10-year period in Eskişehir Province located in western Anatolia in Turkey

Murder of women generally occurs as a result of violence by their husbands and relatives. We evaluated the female victims of murder in Eski?ehir, located in western Anatolia, where the education level is high in this study. Our aim was to assess and discuss data related to the victims and murderers.A total of 141 women's murder cases were analysed in the study. After a legal process and the results of the autopsies during 2002–2011 in Eski?ehir, 715 subjects found to have died as a result of murder were chosen. Cases were evaluated in terms of their age, marital status, education level, relationship to the murderer, reasons for violence, type of action and reasons for death.It was determined that 48.2% (n = 68) of the victims had been killed by the husband and 7.8% (n = 11) by the ex-husband. Murderers generally stated that the reason of murder was the woman's request for divorce or breaking up (n = 40, 28.4%).In compliance with the literature, the women were most commonly killed by their husbands in our study. Enhancing women's status and preventing violence against women will decrease such murders.     

Is the nasopharynx warmer in children than in adults?

Recent studies on the aetiology of the Sudden Infant Death Syndrome (SIDS) have suggested that some of these deaths are the consequence of an overwhelming inflammatory response to the production of pyrogenic toxins from bacteria colonizing the upper respiratory tract, particularly the nasopharynx. The pyrogenic toxins of Staphlococcus aureus, one of the likelier bacterial candidates, are only produced in temperatures of over 37 degrees C. This study examined nasopharyngeal temperatures in children. It is a preliminary study to develop an accurate means to measure how close to 37 degrees C the nasopharyngeal temperature lies in infants at the age when SIDS deaths occur. Following a pilot study and power calculation, measurements of nasopharyngeal temperature were made on 30 apyrexial children aged 4-10 years and 30 adults with no nasal pathology, undergoing surgery under general anaesthesia, using an accurately sited thermocouple probe. The mean temperature in children (35.64 degrees C) was significantly higher than in adults (34.01 degrees C). Comparable measurements attempted with the same subjects awake gave similar results.     

Fatal intoxications in the age group 15–34 years in Denmark in 1984 and 1985

Summary This survey deals with the Danish part of a study on fatal intoxications conducted in the Nordic countries in 1984 and 1985 with special reference to drug addicts. There were 315 cases of fatal intoxications in people 15–34 years of age. These were examined at the Forensic Institutes in Denmark and described with reference to cause of death, sex, age and drug addiction. Of the deceased, 194 were drug addicts according to a specific definition of this term. Women accounted for 28% of all the fatalities investigated in the study and 24% of those in addicts. More than 90% of the deaths were caused by drugs, with ethanol as a contributory factor in approximately 40% of cases. Deaths caused by heroin/morphine predominated, causing 50% of the deaths among drug addicts, but legal drugs, such as dextropropoxyphene, methadone and ketobemidone were also frequent causes of death in this group. In half the cases the concentration of morphine in blood following injection of heroin/morphine was found to be equal to or less than 0.5 mol/ kg, and in only about one-tenth of cases was the blood concentration above 2.0 mol/kg.     

‘Current trends in lower limb Doppler scanning in Ireland’

IntroductionThe clinical need to diagnose and treat above knee deep vein thrombosis (AKDVT) has long been established in literature and in practice. On the other hand, the need to diagnose and treat below knee deep vein thrombosis (BKDVT) continues to be debated in literature. This has resulted in variation in clinical guidelines and protocols nationwide. This research aims to establish if there is a standard practice in Irish ultrasound departments and if so, what that practice is and where sonographers are getting information to inform this.MethodsA questionnaire was designed using SurveyMonkey and distributed using online platforms. The questionnaire aimed to establish the experience of the sonographer, the types of exams performed, protocols/guidelines used as well as scenarios where the sonographer might deviate from protocol.ResultsThe study yielded 90 responses. The research found 49% of sites perform whole leg ultrasound routinely and 46% perform proximal ultrasound only. 41% of respondents said their protocols were based on clinical guidelines however, 22% of participants didn't know what these guidelines were. 49% of respondents were unaware of what treatment a patient would receive in cases where there is a high clinical suspicion of DVT, but the ultrasound is negative for DVT.ConclusionThe research has established a lack of consistency amongst sonographers and scanning practices with a fairly even split (49% of respondents perform whole leg ultrasound and 46% perform proximal only). Not only has the research identified a lack of standardised scanning approach nationwide, but inconsistencies are also seen in the guidelines that inform our department's protocols as well as inconspicuous terms used in radiology reporting and jargon in literature in relation to DVT.Implications for practice1. An inconsistency in practice has been established. Discussions are now needed to decide what guidelines should be implemented into Irish Ultrasound DVT protocols. 2. A national protocol for BKDVT would result in all patients in Ireland having access to the same standard of care. 3. Call for consensus on appropriate training for sonographers undertaking LLDs.     

Posterior-anterior weight-bearing radiograph in 15° knee flexion in medial osteoarthritis

OBJECTIVE: To evaluate the degree of knee flexion at which: (1) degenerative joint space narrowing is best seen, (2) the tibial plateau is best visualized and (3) the tibiofemoral angle is most correct, in order to assess the degree of flexion in the anteroposterior radiographic view that is most useful for assessing medial compartment osteoarthritis (OA) of the knee. DESIGN AND PATIENTS: We compared the conventional extended view of the knee and views at 15 degrees, 30 degrees, and 45 degrees of flexion with respect to joint space narrowing, alignment of the medial tibial plateau (MTP), and tibiofemoral angles in 113 knees of 95 patients with medial osteoarthritis of the knee (22 men, 73 women; mean age 67 years). RESULTS: At the midpoint and the narrowest point of the medial compartment, joint space narrowing values at 15 degrees, 30 degrees, and 45 degrees of flexion of the knee were smaller than that of the conventional extended view. Superimposition of the margins of the tibial plateau was satisfactory in 12% of patients in the conventional extended view, in 36% at 15 degrees of flexion, in 20% at 30 degrees of flexion, and in 19% at 45 degrees of flexion of the knee. When the knee was at 15 degrees of flexion there was a smaller difference in the tibiofemoral angle, in comparison with the knee extended, than was the case at 30 degrees and 45 degrees of flexion in patients with medial OA. CONCLUSION: A posteroanterior view with 15 degrees of flexion of the knee was able to detect joint space narrowing accurately, to achieve good alignment of the MTP in the medial compartment, and to reduce the difference in tibiofemoral angle compared with a view of the knee in conventional extension, and may be an alternative view in cases of medial OA of the knee.     

Xeroradiography in β-thalassaemia

Xeroradiographic investigations of the skull, hand, and elbow were performed on 27 patients with homozygous -thalassaemia. The results were compared with plain radiographic examinations. Xeroradiography, because of its technical properties (i.e. edge contrast enhancement and wide latitude), was shown to demonstrate cortical thinning of long bones, swelling of the diploic space in the skull, and reticulated patterns in the elbow better than standard radiography. Moreover, the use of positive mode imaging was shown to have advantages in the study of the skull and extremities.     

Metabolic Factors in Fatigue

KEYPOINTS Sustainedproductionofmuscularforceduringexercise dependsonthegenerationofchemicalenergy(ATP)bynonoxidative(anaerobic)andoxidative(aerobic)metabolism.Fatiguedevelopswhenthecompoundsneededtopro duceATParedepletedorwhenby-productsof metabolismaccumulateinmuscle.Thesemetabolicchangescancausefatiguebyactingon nerveprocessesthatactivatemuscles.Bothcentral andperipheralnervoussystemsmaybeimpaired.ReductionsinmusclelevelsofATP,phosphocreatine,andglycogen,andlowbloodglucoseavailabilit…