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Progress in Brain Research 2022New understandings of the biology of radiosurgery are considered. Differences from the radiobiology of fractionated radiotherapy are outlined. It is noted DNA damage...
New understandings of the biology of radiosurgery are considered. Differences from the radiobiology of fractionated radiotherapy are outlined. It is noted DNA damage alone is insufficient to account for the tissue changes which occur. Changes in blood vessels and immunological mechanisms are also involved. Tissue repair is more rapid than previously thought so that dose rate (the rate of delivery of radiation to the tissues) has been seen to be more important. The value of fractionation is examined. The effect of radiosurgery on normal brain (so called functional radiosurgery) is considered. The desired effects may be achieved by a focal stable destruction of brain from a high radiation dose. They may also be achieved using a lower dose which acts through the mechanism known as radiosurgical neuromodulation.
Topics: Brain; Dose Fractionation, Radiation; Humans; Radiobiology; Radiosurgery
PubMed: 35074083
DOI: 10.1016/bs.pbr.2021.10.024 -
Japanese Journal of Clinical Oncology May 2020Brachytherapy is an invasive therapy with placement of radiation source into or near the tumor. The difference between planning target volume and clinical target volume... (Review)
Review
Brachytherapy is an invasive therapy with placement of radiation source into or near the tumor. The difference between planning target volume and clinical target volume is minimal, and the dose out of the tumor reduces rapidly due to the inverse-square law. High-dose-rate brachytherapy enables three-dimensional image guidance, and currently, tumor dose as well as doses of the surrounding normal structures can be evaluated accurately. High-dose-rate brachytherapy is the utmost precision radiation therapy even surpassing carbon ion therapy. Biological disadvantages of high-dose rate have been overcome by the fractional irradiation. High-dose-rate brachytherapy is indispensable in the definitive radiation therapy of cervical cancer. Also in prostate cancer and breast cancer, high-dose-rate brachytherapy plays a significant role. Brachytherapy requires techniques and skills of radiation oncologists at the time of invasive placement of the radiation source into the tumor area. Education of young radiation oncologists is most urgent and important.
Topics: Brachytherapy; Dose-Response Relationship, Radiation; Humans; Imaging, Three-Dimensional; Precision Medicine; Radiotherapy Dosage
PubMed: 32134450
DOI: 10.1093/jjco/hyaa029 -
Physics in Medicine and Biology Jan 2022Pulsed low dose-rate radiotherapy (PLDR) relies on two radiobiological findings, the hyper-radiosensitivity of tumor cells at small doses and the reduced normal tissue... (Review)
Review
Pulsed low dose-rate radiotherapy (PLDR) relies on two radiobiological findings, the hyper-radiosensitivity of tumor cells at small doses and the reduced normal tissue toxicity at low dose rates. This is achieved by delivering the daily radiation dose of 2 Gy in 10 sub-fractions (pulses) with a 3 min time interval, resulting in an effective low dose rate of 0.067 Gy min.cell studies andanimal experiments demonstrated the therapeutic potential of PLDR treatments and provided useful preclinical data. Various treatment optimization strategies and delivery techniques have been developed for PLDR on existing linear accelerators. Preliminary results from early clinical studies have shown favorable outcomes for various treatment sites especially for recurrent cancers. This paper reviews the experimental findings of PLDR and dosimetric requirements for PLDR treatment planning and delivery, and summarizes major clinical studies on PLDR cancer treatments.
Topics: Humans; Neoplasms; Particle Accelerators; Radiobiology; Radiometry; Radiotherapy; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted
PubMed: 35038688
DOI: 10.1088/1361-6560/ac4c2f -
Obstetrics and Gynecology Feb 2023Despite lack of evidence for a safety threshold for oxytocin dose rate, many hospital protocols specify a maximum rate. We investigated whether exceeding 20... (Randomized Controlled Trial)
Randomized Controlled Trial
OBJECTIVE
Despite lack of evidence for a safety threshold for oxytocin dose rate, many hospital protocols specify a maximum rate. We investigated whether exceeding 20 milliunits/min of oxytocin was associated with adverse outcomes.
METHODS
This is a secondary analysis of a double-blind, single-center, randomized controlled trial of nulliparous patients with singleton gestations at 36 weeks of gestation or later who presented in spontaneous labor randomized 1:1 to either a high-dose oxytocin titration regimen (initial-incremental rate of 6 milliunits/min) or standard-dose titration regimen (initial-incremental rate of 2 milliunits/min) for labor augmentation. A maximum oxytocin dose rate limit was not specified in the study protocol. For this secondary analysis, outcomes of participants who received oxytocin and exceeded a dose rate of 20 milliunits/min at any point in labor were compared with those whose rate remained at 20 milliunits/min or less. In addition, the cumulative proportions of labor and birth outcomes were calculated for each maximum dose rate of oxytocin reached among this study cohort.
RESULTS
Of the 1,003 participants in the parent trial, 955 (95.2%) received oxytocin, as planned, and were included, with 190 (19.9%) exceeding a maximum dose rate of 20 milliunits/min. Those who exceeded 20 milliunits/min were older and were more likely to have rupture of membranes as their trial entry indication, have hypertensive disorders of pregnancy, receive intrapartum magnesium sulfate infusion, and receive oxytocin for longer. Those whose maximum rates exceeded 20 milliunits/min underwent cesarean delivery more frequently, but the majority (74%) still delivered vaginally. In multivariable analyses, there were no significant associations between maximum oxytocin dose rates greater than 20 milliunits/min and cesarean delivery (adjusted odds ratio [aOR] 1.57, 95% CI 1.00-2.46), peripartum infection (aOR 0.69, 95% CI 0.41-1.19), postpartum hemorrhage (aOR 1.37, 95% CI 0.70-2.71), or neonatal intensive care unit (NICU) admission (aOR 1.72, 95% CI 0.89-3.31). Although 85% of spontaneous vaginal deliveries occurred at maximum oxytocin dose rates of 20 milliunits/min or less, vaginal deliveries continued to occur at higher maximum dose rates. The cumulative proportions of NICU admissions and composite severe neonatal morbidity and mortality cases increased with increasing oxytocin dose rates even with maximum oxytocin dose rates at 20 milliunits/min or less.
CONCLUSION
In multivariable analyses, there are no significant differences in maternal or perinatal adverse outcomes based on exceeding 20 milliunits/min of oxytocin. These data suggest that oxytocin dosing should be individualized to each patient and not be based on arbitrary thresholds.
CLINICAL TRIAL REGISTRATION
ClinicalTrials.gov , NCT02487797.
Topics: Female; Humans; Infant, Newborn; Pregnancy; Cesarean Section; Delivery, Obstetric; Labor, Induced; Oxytocics; Oxytocin; Double-Blind Method
PubMed: 36649339
DOI: 10.1097/AOG.0000000000005058 -
Radiation and Environmental Biophysics Nov 2022Despite decades of research to understand the biological effects of ionising radiation, there is still much uncertainty over the role of dose rate. Motivated by a... (Review)
Review
Despite decades of research to understand the biological effects of ionising radiation, there is still much uncertainty over the role of dose rate. Motivated by a virtual workshop on the "Effects of spatial and temporal variation in dose delivery" organised in November 2020 by the Multidisciplinary Low Dose Initiative (MELODI), here, we review studies to date exploring dose rate effects, highlighting significant findings, recent advances and to provide perspective and recommendations for requirements and direction of future work. A comprehensive range of studies is considered, including molecular, cellular, animal, and human studies, with a focus on low linear-energy-transfer radiation exposure. Limits and advantages of each type of study are discussed, and a focus is made on future research needs.
Topics: Animals; Humans; Radiation Protection; Radiation Dosage; Radiation Injuries; Radiation Exposure; Radiation, Ionizing; Radiobiology
PubMed: 36241855
DOI: 10.1007/s00411-022-00996-0 -
Applied Radiation and Isotopes :... Apr 2022As a consequence of the Chernobyl accident in 1986 the Integrated Measurement and Information System (IMIS) was established (Weiss and Leeb, 1993) which includes on-line... (Review)
Review
As a consequence of the Chernobyl accident in 1986 the Integrated Measurement and Information System (IMIS) was established (Weiss and Leeb, 1993) which includes on-line monitoring networks for the surveillance of radioactivity in Germany. Today, the German Federal Office for Radiation Protection (BfS) operates a gamma dose rate network with 1800 ambient dose equivalent rate H*(10) (ADER) stations almost equally distributed over the German territory. The ADER network integrates Geiger-Müller (GM) based detectors which, if low and high dose rate tubes are combined, are known to have excellent long-term stability and an extended dose rate range from environmental background level (20 nSv/h) up to several Sv/h. However, one main drawback is the lack of information about nuclides contributing to the observed dose rate. Therefore BfS has started to integrate LaBr-based spectrometric detector systems (so-called spectro-dosemeters) in the existing ADER network. In this paper detector design, quality assurance and quality control (QA/QC) procedures are described as well as efforts required to characterize and operate monitoring networks based on spectrometric detectors.
Topics: Germany; Radiation Dosage; Radiation Dosimeters; Radiation Monitoring
PubMed: 35121275
DOI: 10.1016/j.apradiso.2021.110077 -
Applied Radiation and Isotopes :... Aug 2023Review is provided of a number of low-dose, low dose rate situations that in study require advances in the development of dosimetric facilities. Using a clinical linac...
Review is provided of a number of low-dose, low dose rate situations that in study require advances in the development of dosimetric facilities. Using a clinical linac set up to provide doses down to the few mGy level, the performance of a real-time radioluminescence system has then been illustrated, accommodating pulsed as well as continuous dose delivery. The system gate times provide for tracking of the pattern of dose delivery, allowing detailed account of dose and dose-rate variations. The system has been tested in both x-ray and electron mode dose delivery.
Topics: Radiometry; Radiography; Radiotherapy Dosage; X-Rays
PubMed: 37257265
DOI: 10.1016/j.apradiso.2023.110875 -
Frontiers in Oncology 2022
PubMed: 35356219
DOI: 10.3389/fonc.2022.877165 -
Biomedical Instrumentation & Technology Jun 2020In the radiation sterilization arena, the question often arises as to whether radiation resistance of microorganisms might be affected by the energy level of the...
In the radiation sterilization arena, the question often arises as to whether radiation resistance of microorganisms might be affected by the energy level of the radiation source and the rate of the dose delivered (kGy/time). The basis for the question is if the microbial lethality is affected by the radiation energy level and/or the rate the dose is delivered, then the ability to transfer dose among different radiation sources could be challenged. This study addressed that question by performing a microbial inactivation study using two radiation sources (gamma and electron beam [E-beam]), two microbial challenges (natural product bioburden and biological indicators), and four dose rates delivered by three energy levels (1.17 MeV [gamma], 1.33 MeV [gamma], and 10 MeV [high-energy E-beam]). Based on analysis of the data, no significant differences were seen in the rate of microbial lethality across the range of radiation energies evaluated. In summary, as long as proof exists that the specified dose is delivered, dose is dose.
Topics: Gamma Rays; Sterilization
PubMed: 34169974
DOI: 10.2345/0899-8205-54.s3.45 -
Radiation Protection Dosimetry Sep 2023Testing and validation of biodosimetry assays is routinely performed using conventional dose rate irradiation platforms, at a dose rate of approximately 1 Gy/min. In...
Testing and validation of biodosimetry assays is routinely performed using conventional dose rate irradiation platforms, at a dose rate of approximately 1 Gy/min. In contrast, the exposures from an improvised nuclear device will be delivered over a large range of dose rates with a prompt irradiation component, delivered in less than 1 μs, and a protracted component delivered over hours and days. We present preliminary data from a large demographic study we have undertaken for investigation of age, sex and dose rate effects on dicentric and micronucleus yields. Our data demonstrate reduced dicentric and micronucleus yields at very high dose rates. Additionally, we have seen small differences between males and females, with males having slightly fewer micronuclei and slightly more dicentrics than females, at high doses.
Topics: Female; Male; Humans; Cytogenetics; Biological Assay; Cell Nucleus; Cytogenetic Analysis
PubMed: 37721073
DOI: 10.1093/rpd/ncac286