Exposure to multiple ion beams, broadly representative of galactic cosmic rays, causes perivascular cardiac fibrosis in mature male rats.

Long-duration space exploratory missions to the Earth's moon and the planet Mars are actively being planned. Such missions will require humans to live for prolonged periods beyond low earth orbit where astronauts will be continuously exposed to high energy galactic cosmic rays (GCRs). A major unknown is the potential impact of GCRs on the risks of developing degenerative cardiovascular disease, which is a concern to NASA.

Improving the Accuracy of Biologically Effective Dose Estimates, from a Previously Published Study, After Radiosurgery for Acoustic Neuromas.

Objective: To recalculate biological effective dose values (BED) for radio-surgical treatments of acoustic neuroma from a previous study. BEDs values were previously overestimated by only using beam-on times in calculations, so excluding the important beam-off-times (when deoxyribonucleic acid repair continues) which contribute to the overall treatment time. Simple BED estimations using a mono-exponential approximation may not always be appropriate but if used should include overall treatment time.

Dr Tikvah Alper: a short history of her scientific career.

Purpose: This article can only skim the surface of an extraordinary career of Dr Alper from the early days in South Africa and throughout her life.

Conclusions: She overcame many obstacles to become widely acknowledged as having had an immense effect on the study of radiation biology. Her very considerable personal scientific achievements in no way prevented her from taking time to help and inspire others in the field as well as maintaining a long and happy family life.

Further development of spinal cord retreatment dose estimation: including radiotherapy with protons and light ions.

Purpose: A graphical user interface (GUI) was developed to aid in the assessment of changes in the radiation tolerance of spinal cord/similar central nervous system tissues with time between two individual treatment courses.

Methods: The GUI allows any combination of photons, protons (or ions) to be used as the initial, or retreatment, radiotherapy courses. Allowances for clinical circumstances, of reduced tolerance, can also be made.

The impact of unscheduled gaps and iso-centre sequencing on the biologically effective dose in Gamma Knife radiosurgery.

Purpose: Establish the impact of iso-centre sequencing and unscheduled gaps in Gamma Knife® (GK) radiosurgery on the biologically effective dose (BED).

Methods: A BED model was used to study BED values on the prescription iso-surface of patients treated with GK Perfexion™ (Vestibular Schwannoma). The effect of a 15 min gap, simulated at varying points in the treatment delivery, and adjustments to the sequencing of iso-centre delivery, based on average dose-rate, was quantified in terms of the impact on BED.

The influence of the α/β ratio on treatment time iso-effect relationships in the central nervous system.

To investigate the influence of changes in α/β ratio (range 1.5-3 Gy) on iso-effective doses, with varying treatment time, in spinal cord and central nervous system tissues with comparable radio-sensitivity. It is important to establish if an α/β ratio of 2 Gy, the accepted norm for neuro-oncology iso-effect estimations, can be used.

Establishment of a Therapeutic Ratio for Gamma Knife Radiosurgery of Trigeminal Neuralgia: The Critical Importance of Biologically Effective Dose Versus Physical Dose.

Objective: How variations of treatment time affect the safety and efficacy of Gamma Knife (GK) radiosurgery is a matter of considerable debate. With the relative simplicity of treatment planning for trigeminal neuralgia (TN), this question has been addressed in a group of these patients. Using the concept of the biologically effective dose (BED), the effect of the two key variables, dose and treatment time, were considered.

Effects of variations in overall treatment time on the clonogenic survival of V79-4 cells: Implications for radiosurgery.

The importance of effects related to the repair of sublethal radiation damage as treatment duration varies, partly a function of dose-rate, is a current controversy in clinical radiosurgery. Cell survival studies have been performed to verify the importance of this effect in relation to established models. Mammalian V79-4 cells were irradiated in vitro with γ-rays, either as an acute exposure in a few minutes, where the effects of sublethal irradiation damage repair over the period of exposure can be ignored, or as protracted exposures delivered over 15-120 min.

Modelling the influence of treatment time on the biological effectiveness of single radiosurgery treatments: derivation of "protective" dose modification factors.

Objective: To provide simpler models for adjusting total dose to compensate for significant variations in central nervous system radiosurgical treatment times, which vary and will influence treatment bioeffectiveness. At present, no allowance is made for time variations. A framework of simpler equations would allow radiosurgical outcomes to be analysed with respect to treatment time, and a system for dose adjustments between radioisotope and linac-based techniques with different treatment durations.

Changes in the retreatment radiation tolerance of the spinal cord with time after the initial treatment.

Purpose: To estimate, from experimental data, the retreatment radiation 'tolerances' of the spinal cord at different times after initial treatment.

Materials And Methods: A model was developed to show the relationship between the biological effective doses (BEDs) for two separate courses of treatment with the BED of each course being expressed as a percentage of the designated 'retreatment tolerance' BED value, denoted [Formula: see text] and [Formula: see text]. The primate data of Ang et al.

Effects of Synchrotron X-Ray Micro-beam Irradiation on Normal Mouse Ear Pinnae.

Purpose: To analyze the effects of micro-beam irradiation (MBI) on the normal tissues of the mouse ear.

Methods And Materials: Normal mouse ears are a unique model, which in addition to skin contain striated muscles, cartilage, blood and lymphatic vessels, and few hair follicles. This renders the mouse ear an excellent model for complex tissue studies.

Simvastatin mitigates increases in risk factors for and the occurrence of cardiac disease following 10 Gy total body irradiation.

The ability of simvastatin to mitigate the increases in risk factors for and the occurrence of cardiac disease after 10 Gy total body irradiation (TBI) was determined. This radiation dose is relevant to conditioning for stem cell transplantation and threats from radiological terrorism. Male rats received single dose TBI of 10 Gy.

The role of the concept of biologically effective dose (BED) in treatment planning in radiosurgery.

Radiosurgery (RS) treatment times vary, even for the same prescription dose, due to variations in the collimator size, the number of iso-centres/beams/arcs used and the time gap between each of these exposures. The biologically effective dose (BED) concept, incorporating fast and slow components of repair, was used to show the likely influence of these variables for Gamma Knife patients with Vestibular Schwannomas. Two patients plans were selected, treated with the Model B Gamma Knife, these representing the widest range of treatment variables; iso-centre numbers 3 and 13, overall treatment times 25.

Alternative models for estimating the radiotherapy retreatment dose for the spinal cord.

Purpose: To review the available experimental animal and patient data on response of the spinal cord to re-irradiation in order to identify appropriate data sets to investigate the clinical potential of models that would allow evaluation of the increase in the retreatment dose with elapsed time from the initial exposure.

Materials/methods: Analysis of published data on irradiated rat and primate spinal cord identified results for the rat cervical spinal cord that could be compared, where the development of myelopathy was caused by selective white matter necrosis. This data, although limited, provide some important insights.

Response to 'Position statement on ethics, equipoise and research on charged particle therapy'.

In August 2011, a group of medical doctors, ethicists, academic and medical physicists were asked to debate and reach consensus on the potential need for randomised control trials to test charged particle radiation therapy (CPRT) for treating tumours. The outcome of the meeting was a paper recently published in the Journal of Medical Ethics entitled "Position statement on ethics, equipoise and research on charged particle therapy" by Sheehan et al. However 6 of the 30 meeting participants withdrew from authorship of the 'position statement' because their views were not adequately represented.

Cardiac injury after 10 gy total body irradiation: indirect role of effects on abdominal organs.

The objective of this study was to determine whether radiation-induced injury to the heart after 10 Gy total body irradiation (TBI) is direct or indirect. Young male WAG/RijCmcr rats received a 10 Gy single dose using TBI, upper hemi-body (UHB) irradiation, lower hemi-body (LHB) irradiation, TBI with the kidneys shielded or LHB irradiation with the intestines shielded. Age-matched, sham-irradiated rats served as controls.

Response of the rat spinal cord to X-ray microbeams.

Background And Purpose: To quantify the late dose-related responses of the rat cervical spinal cord to X-ray irradiations by an array of microbeams or by a single millimeter beam.

Materials And Methods: Necks of anesthetized rats were irradiated transversely by an 11 mm wide array of 52 parallel, 35 μm wide, vertical X-ray microbeams, separated by 210 μm intervals between centers. Comparison was made with rats irradiated with a 1.

Application of the concept of biologically effective dose (BED) to patients with Vestibular Schwannomas treated by radiosurgery.

In the application of stereotactic radiosurgery, using the Gamma Knife, there are large variations in the overall treatment time for the same prescription dose, given in a single treatment session, for different patients. This is due to not only changes in the activity of the Cobolt-60 sources, but also to variations in the number of iso-centers used, the collimator size for a particular iso-center, and the time gap between the different iso-centers. Although frequently viewed as a single dose treatment the concept of biologically effective dose (BED), incorporating concurrent fast and a slow components of repair of sublethal damage, would imply potential variations in BED because of the influence of these different variables associated with treatment.