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Cancer Radiotherapie : Journal de La... Jun 2005The purpose of this article is to propose a building model to delineate Clinical Target Volume in laryngeal cancers (squamous cell carcinoma). This model uses... (Review)
Review
The purpose of this article is to propose a building model to delineate Clinical Target Volume in laryngeal cancers (squamous cell carcinoma). This model uses histological knowledge about the spread of laryngeal cancers. Firstly is described the spread, depending on primary location and anatomic structures. Then illustrated examples on Computed Tomography are provided. This delineation approach appears to be useful with 3D-CRT and IMRT for adapting dose delivery to the complex spread of laryngeal cancer.
Topics: Carcinoma, Squamous Cell; Dose Fractionation, Radiation; Humans; Imaging, Three-Dimensional; Laryngeal Neoplasms; Magnetic Resonance Imaging; Models, Theoretical; Tomography, X-Ray Computed
PubMed: 15996885
DOI: 10.1016/j.canrad.2005.05.003 -
Radiotherapy and Oncology : Journal of... Aug 2019Conventionally fractionated and stereotactic body radiation therapy (SBRT) for thoracoabdominal tumors may utilize breath-hold techniques. However, there are concerns...
BACKGROUND
Conventionally fractionated and stereotactic body radiation therapy (SBRT) for thoracoabdominal tumors may utilize breath-hold techniques. However, there are concerns that differential amounts of inspired airflow may result in unplanned tumor dislocation and underdosing. Thus, we investigated tumor localization accuracy associated with lung volume variations during breath-hold treatment via an automated-gating interface.
METHODS
Twelve patients received breath-hold treatment with the active breathing coordinator (ABC) through an automated-gating interface. All breath-hold volumes were recorded at CT simulation, setup imaging, and during treatment, and analyzed as a function of airflow rate into the ABC. The variation of breath-hold volumes was calculated for each fraction over entire course. Intrafraction target motion related to the breathing variation was investigated based on daily imaging acquired before the breath-hold treatment. Correlation between target location and breath-hold variation was statistically analyzed.
RESULTS
The air volume held by the ABC increased as the airflow rate increased on inhalation and decreased on exhalation. The mean range of airflow rate was 0.77 L/s and 0.29 L/s in the conventionally fractionated and SBRT patients, respectively. The maximum air volume difference with respect to the reference volume at the CT simulation was 1.0 L for conventional fractionation and 0.16 L for SBRT. The target dislocation caused by 0.25 L of air volume difference was 6 mm for SBRT. Three patients showed significant correlation between the target location and breath-hold variations.
CONCLUSIONS
This investigation shows that because variations in the breath-hold volume may cause target dislocation, patient-specific breath-hold setting is required to improve tumor localization accuracy.
Topics: Aged; Aged, 80 and over; Breath Holding; Dose Fractionation, Radiation; Exhalation; Female; Humans; Lung Neoplasms; Male; Middle Aged; Radiosurgery; Radiotherapy Planning, Computer-Assisted
PubMed: 31103912
DOI: 10.1016/j.radonc.2019.04.036 -
Rays 2004A few important concepts in radiobiology are illustred. The cell survival, the concept of the biologically effective dose, the basis of fractionation in radiotherapy are... (Review)
Review
A few important concepts in radiobiology are illustred. The cell survival, the concept of the biologically effective dose, the basis of fractionation in radiotherapy are considered. Slow tumor regression after irradiation is not an indication of treatment failure, and the rate of regression is not , in general, prognostic. Dose volume histograms provide many data for predicting tumor control and side effects. The magnitude of a dose reduction in the tumor is the major determinant of decline in tumor control probability. Escalation of dose to hypoxic foci may be beneficial. Basic knowledge of these concepts is essential for daily radiotherapy practice and for all radiation oncologists.
Topics: Cell Survival; Dose Fractionation, Radiation; Humans; Neoplasms; Radiobiology; Relative Biological Effectiveness
PubMed: 15603293
DOI: No ID Found -
Practical Radiation Oncology 2016This white paper recommends the standardization (content and presentation order) of several "key components" of the radiation therapy prescription to facilitate accurate...
This white paper recommends the standardization (content and presentation order) of several "key components" of the radiation therapy prescription to facilitate accurate communication between radiation therapy care providers. The rationale, other similar efforts, and detailed considerations are described. In brief, the Task Force recommends that the prescription's "elements" include: treatment site, method of delivery, dose per fraction, total number of fractions, total dose (eg, right breast, tangent photons, 267 cGy * 16 = 4272 cGy). A similar formalism is recommended for brachytherapy (eg, cervix, Ir-192 brachytherapy, 600cGy * 5 = 3000 cGy) and other modalities. The white paper also considers future directions for other items such as the simulation order, treatment planning objectives, prescription point or volume, treatment schedule, localization imaging, laboratory monitoring, concurrent chemotherapy, patient instructions for treatment, etc. The intent of this white paper is to facilitate accurate communication among providers to support safe practice as well as to guide vendors in product development that is consistent with this standard prescription.
Topics: Brachytherapy; Dose Fractionation, Radiation; Humans; Interdisciplinary Communication; Medical Oncology; Neoplasms; Patient Care Planning; Prescriptions; Radiation Oncology; Radiotherapy Dosage; Reference Standards
PubMed: 27693224
DOI: 10.1016/j.prro.2016.08.007 -
Journal of Chromatography. A Apr 2010This review focuses on the applications of silicone in the form of tubes or rods for sorptive extraction of organic compounds as sample preparation method in combination... (Review)
Review
This review focuses on the applications of silicone in the form of tubes or rods for sorptive extraction of organic compounds as sample preparation method in combination with various chromatographic techniques. Silicone rods (SRs) and silicone tubes (STs) have the advantage of being inexpensive, flexible and robust. SRs and STs with different sizes and volumes of silicone (8-635microL) have so far been applied for the extraction/preconcentration of a large variety of organic micropollutants from different matrices. The theoretical principle of SR and ST extraction in comparison with similar microextraction techniques is presented as well as a summary of the published applications of SR and ST extraction in combination with gas chromatography (GC) or liquid chromatography (LC). Furthermore, the use of SRs and STs for time-integrated (passive) sampling is reported.
Topics: Adsorption; Air; Chemical Fractionation; Chromatography, Gas; Models, Theoretical; Silicones; Water
PubMed: 19954783
DOI: 10.1016/j.chroma.2009.11.025 -
Medical Physics May 2017The goal of this article is to compute the cell survival during fractionated radiotherapy with non-uniform hypoxia-targeted dose distribution relative to cell survival...
PURPOSE
The goal of this article is to compute the cell survival during fractionated radiotherapy with non-uniform hypoxia-targeted dose distribution relative to cell survival for a uniform dose distribution with equal integral tumor dose. The analysis is performed for different parameters of radiotherapy with conventional and hypofractionated dose regimens.
METHODS
Our analysis is done using a parsimonious tumor response model that describes the major components of tumor response to radiotherapy such as radiosensitivity, cell proliferation, and hypoxia using as few variables as possible. Two levels of oxygenated and hypoxic cells with the survival curves described by the linear quadratic (LQ) model are implemented in the model. The model allows for analytical solutions for relative cell survival in a single fraction simulation which can be used for additional validation of our numerical simulations. The relative cell survival was computed for conventional and hypofractionated dose regimens in a model problem with radiobiological parameters for the non-small-cell lung cancer. Sensitivity of cell survival to different parameters of radiotherapy such as the relative volume of hypoxic fraction, boost dose ratio, re-oxygenation rate, and delivery errors was investigated.
RESULTS
Our computational and analytical results show that relative cell survival for non-uniform and uniform dose distributions is larger than 1.0 during the first few fractions of radiotherapy with conventional fractionation. This indicates that the uniform dose distribution produces a higher cell killing effect for the equal integral dose. This may stem from domination of linear contribution to the cell killing effect seen in the dose range of 1-2 Gy and a steeper slope of survival curve in the oxygenated tumor region. This effect can only happen if the distribution of clonogens is nearly uniform; therefore, after the first few fractions, the non-uniform dose distributions outperform the uniform dose distribution and relative cell survival becomes less than 1.0. However, re-oxygenation and delivery errors can also reduce the effectiveness of hypoxia-targeted non-uniform dose distributions toward the end of treatment. For hypofractionated radiotherapy with fractional dose >3 Gy, the relative cell survival was always below 1.0, which means the non-uniform dose distributions produced higher cell killing effect than the uniform dose distribution during the entire treatment.
CONCLUSION
The data obtained in this work suggest that non-uniform hypoxia-targeted dose distributions are less effective at cell killing than uniform dose distributions at the beginning of radiotherapy with conventional fractionation. However; non-uniform dose distributions can outperform uniform dose distribution by the end of the treatment if the effects of re-oxygenation and delivery errors are reduced. In hypofractionated radiotherapy, non-uniform hypoxia-targeted dose distributions are more efficient than uniform dose distributions during the entire treatment.
Topics: Carcinoma, Non-Small-Cell Lung; Cell Survival; Dose Fractionation, Radiation; Humans; Hypoxia; Lung Neoplasms; Models, Biological; Radiobiology; Tumor Cells, Cultured
PubMed: 28236652
DOI: 10.1002/mp.12177 -
Radiation Oncology (London, England) Feb 2016A method is presented to radiobiologically compare sequential (SEQ) and simultaneously integrated boost (SIB) breast radiotherapy. (Comparative Study)
Comparative Study
PURPOSE
A method is presented to radiobiologically compare sequential (SEQ) and simultaneously integrated boost (SIB) breast radiotherapy.
METHODS
The method is based on identically prescribed biologically effective dose (iso-BED) which was achieved by different prescribed doses due to different fractionation schemes. It is performed by converting the calculated three-dimensional dose distribution to the corresponding BED distribution taking into consideration the different number of fractions for generic α/β ratios. A cumulative BED volume histogram (BEDVH) is then derived from the BED distribution and is compared for the two delivery schemes. Ten breast cancer patients (4 right-sided and 6 left-sided) were investigated. Two tangential intensity modulated whole breast beams with two other oblique (with different gantry angles) beams for the boost volume were used. The boost and the breast target volumes with either α/β = 10 or 3 Gy, and ipsi-lateral and contra-lateral lungs, heart, and contra-lateral breast as organs at risk (OARs) with α/β = 3 Gy were compared.
RESULTS
Based on the BEDVH comparisons, the use of SIB reduced the biological breast mean dose by about 3 %, the ipsi-lateral lung and heart by about 10 %, and contra-lateral breast and lung by about 7 %.
CONCLUSION
BED based comparisons should always be used in comparing plans that have different fraction sizes. SIB schemes are dosimetrically more advantageous than SEQ in breast target volume and OARs for equal prescribed BEDs for breast and boost.
Topics: Breast Neoplasms; Dose Fractionation, Radiation; Female; Humans; Imaging, Three-Dimensional; Models, Statistical; Radiotherapy; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Intensity-Modulated; Relative Biological Effectiveness; Retrospective Studies; Risk; Software; Tomography, X-Ray Computed
PubMed: 26830843
DOI: 10.1186/s13014-016-0590-1 -
Physics in Medicine and Biology Jan 2020To investigate the dosimetric impact of intrafraction translation and rotation motion of the prostate, as extracted from daily acquired post-treatment 3D cine-MR based...
To investigate the dosimetric impact of intrafraction translation and rotation motion of the prostate, as extracted from daily acquired post-treatment 3D cine-MR based on soft-tissue contrast, in extremely hypofractionated (SBRT) prostate patients. Accurate dose reconstruction is performed by using a prostate intrafraction motion trace which is obtained with a soft-tissue based rigid registration method on 3D cine-MR dynamics with a temporal resolution of 11 s. The recorded motion of each time-point was applied to the planning CT, resulting in the respective dynamic volume used for dose calculation. For each treatment fraction, the treatment delivery record was generated by proportionally splitting the plan into 11 s intervals based on the delivered monitor units. For each fraction the doses of all partial plan/dynamic volume combinations were calculated and were summed to lead to the motion-affected fraction dose. Finally, for each patient the five fraction doses were summed, yielding the total treatment dose. Both daily and total doses were compared to the original reference dose of the respective patient to assess the impact of the intrafraction motion. Depending on the underlying motion of the prostate, different types of motion-affected dose distributions were observed. The planning target volumes (PTVs) ensured CTV_30 (seminal vesicles) D99% coverage for all patients, CTV_35 (prostate corpus) coverage for 97% of the patients and GTV_50 (local boost) for 83% of the patients when compared against the strict planning target D99% value. The dosimetric impact due to prostate intrafraction motion in extremely hypofractionated treatments was determined. The presented study is an essential step towards establishing the actual delivered dose to the patient during radiotherapy fractions.
Topics: Algorithms; Dose Fractionation, Radiation; Humans; Imaging, Three-Dimensional; Male; Movement; Prostatic Neoplasms; Radiometry; Radiosurgery; Radiotherapy Planning, Computer-Assisted; Rotation
PubMed: 31842008
DOI: 10.1088/1361-6560/ab6241 -
Acta Oncologica (Stockholm, Sweden) Nov 2010Published results of randomised trials involving >7000 women confirm the safety and efficacy of hypofractionated schedules of adjuvant radiotherapy for women with early... (Meta-Analysis)
Meta-Analysis
Published results of randomised trials involving >7000 women confirm the safety and efficacy of hypofractionated schedules of adjuvant radiotherapy for women with early breast cancer using fraction sizes between 2 and 3 Gy assuming appropriate downward adjustments to total dose. Unnecessary concerns relating to heart tolerance, suboptimal dose distribution and duration of follow up need not discourage the routine adoption of 15- or 16-fraction schedules in women treated by breast conservation surgery for early breast cancer. Regardless of fractionation regimen, dose escalation to the index quadrant in high risk subgroups will result in a greater relative increase in late adverse effects than tumour control, a therapeutic disadvantage that can only be overcome by exploiting a marked dose-volume effect. A 15-fraction schedule of whole breast radiotherapy is unlikely to represent the lower limits of hypofractionation, and the preliminary results of a 5-fraction regimen are encouraging.
Topics: Adult; Aged; Breast Neoplasms; Dose Fractionation, Radiation; Female; Humans; Mastectomy, Segmental; Middle Aged; Radiotherapy, Adjuvant; Treatment Outcome; United Kingdom
PubMed: 20950226
DOI: 10.3109/0284186X.2010.509334 -
Physics in Medicine and Biology May 2012The purpose of this study was to investigate the increase in cell kill that can be achieved by tumor irradiation with heterogeneous dose distributions targeting hypoxic...
The purpose of this study was to investigate the increase in cell kill that can be achieved by tumor irradiation with heterogeneous dose distributions targeting hypoxic regions that can be visualized with non-invasive imaging. Starting with a heterogeneous distribution of microvessels, a microscopic two-dimensional model of tumor oxygenation was developed using planar simulation of oxygen diffusion. Non-invasive imaging of hypoxia was simulated taking partial volume effect into account. A dose-modulation scheme was implemented with the goal of delivering higher doses to the hypoxic pixels, as seen in simulated hypoxia images. To determine the relative cell kill in response to hypoxia-targeting irradiation, tumor cell survival fractions were compared to those resulting from treatments delivering the same average dose to the lesion in a spatially uniform fashion. It was shown that hypoxia-targeting dose modulation may be better suited for tumors with low α/β, low hypoxic fraction and spatially aggregated hypoxic features. Most importantly, it was determined that at low fraction doses there is no cell kill increase from targeting hypoxic regions alone versus escalating the total tumor dose. However, for higher doses per fraction (≥8 Gy/fraction), the effectiveness of hypoxia-targeting irradiation increases, resulting in the tumoricidal effect of up to 30% higher than that of uniform tumor irradiation delivering the same average tumor dose.
Topics: Cell Hypoxia; Cell Line, Tumor; Cell Survival; Dose Fractionation, Radiation; Humans; Models, Biological; Neoplasms; Positron-Emission Tomography
PubMed: 22507874
DOI: 10.1088/0031-9155/57/9/2757