Time , Dose & Fractionationrevised
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The document discusses key concepts in radiation oncology including dose fractionation, tumor lethal dose, normal tissue tolerance, and factors that affect radiosensitivity. Fractionating the total radiation dose into smaller daily doses allows time for repair of sublethal damage in normal tissues, improving the therapeutic ratio by reducing side effects while still effectively treating the tumor.
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TIME DOSE & FRACTIONATION
Introduction
Time dose & fractionation
Therapeutic index
Four R’s Of Radiobiology
Radiation response
Survival Curves Of Early & Late Responding Cells
Various fractionation schedules
Clinical trials of altered fractionation
Time, dose and fractionation
This document discusses various aspects of fractionation in radiotherapy. It begins by describing early experiments by Regaud showing that fractionated doses achieved tumor sterilization without excessive skin damage, compared to single high doses. It then discusses the four R's of radiobiology - repair, repopulation, redistribution and reoxygenation - which form the basis for fractionated regimens. Various fractionation schedules are described, including conventional, hyperfractionation, accelerated fractionation and hypofractionation. The advantages and disadvantages of different approaches are summarized.
Basics of linear quadratic model
1) The linear-quadratic (LQ) model is commonly used in clinical practice to model cell survival patterns after radiation exposure and calculate biologically equivalent doses.
2) While the LQ model reasonably predicts cell survival up to doses of around 10 Gy per fraction, it may overestimate biological effect at higher doses used in stereotactic radiotherapy.
3) Several modifications have been proposed to the LQ model to address its limitations at high doses, such as accounting for non-DNA targets and cell repopulation, but there is currently no clear alternative model.
Linear quadratic model ppt
This document summarizes key concepts regarding radiation-induced cell death and survival curves. It discusses how cell death is defined for differentiated and proliferating cells. The linear-quadratic model is then explained, which describes cell survival curves using alpha and beta coefficients. Various fractionation schemes and their resulting biological effective doses are calculated and compared for treating different head and neck cancers. The limitations of hypofractionation and importance of accounting for tumor proliferation are also covered.
Dose volume histogram
This document discusses dose-volume histograms (DVHs) which are used to analyze and compare radiation dose distributions in radiotherapy treatment planning. It describes how DVHs are generated by counting the number of voxels receiving different dose levels. DVHs can be displayed cumulatively or differentially and show the volume of structures receiving particular doses. The document outlines some limitations of DVHs including their insensitivity to small hot or cold spots and lack of spatial information. It emphasizes that DVHs should be used along with visual analysis of dose distributions and dose-volume statistics when evaluating treatment plans.
Cell survival curve ppt.
Cell survival curves show the relationship between radiation dose and the proportion of cells that survive. For low linear energy transfer (LET) radiation like X-rays, the curve starts with a shoulder region followed by an exponential decrease in survival fraction. The linear-quadratic model describes cell survival as an exponential function of dose, with parameters α and β representing linear and quadratic components of cell killing. Fractionation reduces cell survival more than single high doses by allowing repair of sublethal damage between fractions. Hypoxic cells are less sensitive initially but may reoxygenate and become sensitive to later fractions. Mitotic cell death is the most common mode of radiation-induced cell death in tumor cells.
Clinical response to normal tissue with radiation
The document discusses the clinical response of normal tissues to radiation. It makes three key points:
1) The response of normal tissues to radiation is determined by the inherent radiosensitivity of individual cells, the kinetics of the tissue as a whole, and how cells are organized structurally within the tissue.
2) Radiation effects are divided into early (acute) effects, which occur within days or weeks and result from cell death, and late effects, which appear months or years later and occur in slowly proliferating tissues.
3) Tissues can be classified based on their functional subunits (FSUs). Tissues with well-defined FSUs like the kidney have a low radiation tolerance, while tissues
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Introduction
Time dose & fractionation
Therapeutic index
Four R’s Of Radiobiology
Radiation response
Survival Curves Of Early & Late Responding Cells
Various fractionation schedules
Clinical trials of altered fractionation
Time, dose and fractionation
This document discusses various aspects of fractionation in radiotherapy. It begins by describing early experiments by Regaud showing that fractionated doses achieved tumor sterilization without excessive skin damage, compared to single high doses. It then discusses the four R's of radiobiology - repair, repopulation, redistribution and reoxygenation - which form the basis for fractionated regimens. Various fractionation schedules are described, including conventional, hyperfractionation, accelerated fractionation and hypofractionation. The advantages and disadvantages of different approaches are summarized.
Basics of linear quadratic model
1) The linear-quadratic (LQ) model is commonly used in clinical practice to model cell survival patterns after radiation exposure and calculate biologically equivalent doses.
2) While the LQ model reasonably predicts cell survival up to doses of around 10 Gy per fraction, it may overestimate biological effect at higher doses used in stereotactic radiotherapy.
3) Several modifications have been proposed to the LQ model to address its limitations at high doses, such as accounting for non-DNA targets and cell repopulation, but there is currently no clear alternative model.
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This document summarizes key concepts regarding radiation-induced cell death and survival curves. It discusses how cell death is defined for differentiated and proliferating cells. The linear-quadratic model is then explained, which describes cell survival curves using alpha and beta coefficients. Various fractionation schemes and their resulting biological effective doses are calculated and compared for treating different head and neck cancers. The limitations of hypofractionation and importance of accounting for tumor proliferation are also covered.
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This document discusses dose-volume histograms (DVHs) which are used to analyze and compare radiation dose distributions in radiotherapy treatment planning. It describes how DVHs are generated by counting the number of voxels receiving different dose levels. DVHs can be displayed cumulatively or differentially and show the volume of structures receiving particular doses. The document outlines some limitations of DVHs including their insensitivity to small hot or cold spots and lack of spatial information. It emphasizes that DVHs should be used along with visual analysis of dose distributions and dose-volume statistics when evaluating treatment plans.
Cell survival curve ppt.
Cell survival curves show the relationship between radiation dose and the proportion of cells that survive. For low linear energy transfer (LET) radiation like X-rays, the curve starts with a shoulder region followed by an exponential decrease in survival fraction. The linear-quadratic model describes cell survival as an exponential function of dose, with parameters α and β representing linear and quadratic components of cell killing. Fractionation reduces cell survival more than single high doses by allowing repair of sublethal damage between fractions. Hypoxic cells are less sensitive initially but may reoxygenate and become sensitive to later fractions. Mitotic cell death is the most common mode of radiation-induced cell death in tumor cells.
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The document discusses the clinical response of normal tissues to radiation. It makes three key points:
1) The response of normal tissues to radiation is determined by the inherent radiosensitivity of individual cells, the kinetics of the tissue as a whole, and how cells are organized structurally within the tissue.
2) Radiation effects are divided into early (acute) effects, which occur within days or weeks and result from cell death, and late effects, which appear months or years later and occur in slowly proliferating tissues.
3) Tissues can be classified based on their functional subunits (FSUs). Tissues with well-defined FSUs like the kidney have a low radiation tolerance, while tissues
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This document discusses fractionation in radiation therapy. It begins with a historical review of fractionation and discusses how proliferation is a factor for normal tissues. Early responding tissues like skin and mucosa proliferate within weeks of starting fractionated radiation, while late responding tissues like spinal cord and bladder proliferate far beyond the overall treatment time of most regimens. Prolonging overall treatment time has a large sparing effect on early reactions but little effect on late reactions. The document then discusses different tissue responses and rationales for fractionation including accelerated repopulation and different fractionation schedules like conventional, hyperfractionation, accelerated fractionation, concomitant boost, split-course, and hypofractionation.
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The document discusses cell survival curves, which describe the relationship between radiation dose and the proportion of cells that survive. It defines key terms like clonogenic cells and explains the components of in vitro survival curves. It describes exponential and shoulder survival curves based on single-hit and multi-target theories. The mechanisms of cell killing like mitotic death and apoptosis are covered. Factors influencing radiosensitivity like dose rate, oxygen level and genetic mutations are summarized. Comparisons are made between survival curves of different mammalian cell types and microorganisms.
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The four R's of radiobiology are repair, repopulation, redistribution, and reoxygenation. Repair refers to cells' ability to fix radiation-induced DNA damage through pathways like base excision repair. Redistribution occurs as cells in different phases of the cell cycle have differing radiosensitivities. Repopulation is the regrowth of cells after irradiation. Repopulation can reduce the effectiveness of fractionated radiotherapy if it accelerates in tumors. Reoxygenation describes how hypoxic tumor cells may reoxygenate between fractions, increasing their sensitivity to subsequent doses. Fractionating radiation therapy exploits these four R's to better kill tumor cells while allowing normal tissues to recover.
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This document discusses central axis depth doses in water for both SSD and SAD techniques. For SSD technique:
- Percentage depth dose (PDD) curves measure attenuation at different depths and are affected by beam quality, field size, and SSD.
- Buildup region occurs as secondary electrons deposit energy downstream, increasing dose with depth until maximum.
- Depth dose maximum (zmax) depends on beam energy and field size.
- PDD increases with larger field sizes due to increased scatter radiation.
- PDD increases with longer SSD due to the inverse square law of radiation intensity.
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1) The document discusses various factors that affect radiation response, including linear energy transfer (LET), relative biological effectiveness (RBE), oxygen effect, and cell cycle phase.
2) It provides details on oxygen enhancement ratio (OER), describing how it ranges from 2.5-3.0 for x-rays and varies according to cell cycle phase and radiation type (higher for x-rays and neutrons vs. alpha particles).
3) LET is discussed in relation to radiation type (low for x-rays, medium for neutrons, high for alpha particles) and how it impacts ionization density and biological damage. An optimal LET of around 100 keV/μm is described.
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Cell survival curve
describes relationship between radiation dose and the fraction of cells that “survive” that dose
model of cell killing
target model
linear quadratic model
TSET
Total skin electron therapy (TSET) is used to treat cutaneous T-cell lymphoma by delivering a uniform dose of radiation to the entire skin surface while sparing underlying organs. It requires large electron fields over the entire body and precise dosimetry. The most common technique uses six electron beams arranged at 60 degree intervals to provide circumferential coverage. Proper field design and calibration are needed to achieve uniform dose across irregular body surfaces and minimize dose from bremsstrahlung x-rays.
Chap 5 fractionated radiation and the dose rate effect
This chapter discusses fractionated radiation and the dose-rate effect. It covers operational classifications of radiation damage including potentially lethal damage and sublethal damage. Fractionation allows for repair of sublethal damage through processes like reassortment and repopulation. The dose-rate effect results from increased repair at lower dose rates. Examples are provided for both in vitro and in vivo models. Brachytherapy techniques like intracavitary and interstitial brachytherapy are also summarized.
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Fractionated radiation and dose rate effect
Fractionated radiation and the dose-rate effect can impact cell survival through mechanisms like sublethal damage (SLD) repair and cell cycle redistribution. SLD repair occurs as double-strand breaks are rejoined after radiation exposure. At lower dose rates, more SLD can be repaired between fractions, improving cell survival. However, very low dose rates may instead reduce survival if cells become frozen in radiosensitive phases of the cell cycle. The dose-rate effect varies between cell types and depends on factors like oxygenation and ability to progress through the cell cycle after radiation.
Treatment verification and set up errors
This document discusses the importance of treatment verification in radiotherapy and outlines the process. It notes that even small errors can have negative consequences so treatment verification is essential to ensure the right dose is delivered to the right area. The key aspects of treatment verification are machine setup, monitor units, patient positioning and imaging by comparing images to references. Errors can be systematic from planning or random from daily variations; various methods are described to reduce errors and ensure treatments are accurately delivered.
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This document discusses planned and unplanned gaps in radiation therapy treatment schedules. Planned gaps are built into the schedule to account for tumor repopulation during weekends and holidays. Unplanned gaps negatively impact treatment outcomes by prolonging the overall time and allowing tumors to regrow. The effects of gaps depend on the prolongation length, tumor proliferation rate, and timing of the interruption. Corrections like increasing the dose or number of fractions are sometimes made to account for biological effects of treatment gaps.
Electron beam therapy
Electron beam therapy uses accelerated electrons to treat superficial tumors. Electrons interact with matter through inelastic collisions that cause ionization and excitation, and elastic collisions that scatter the electrons. This gives electron beams a characteristically sharp dose drop-off beyond the tumor depth. Key applications of electron beams include treatment of skin cancers, chest wall irradiation for breast cancer, and boost doses to lymph nodes.
4 r's of radiobiology and dose rate effects
1) The four Rs of radiobiology are repair, re-assortment, repopulation, and re-oxygenation. They influence how tumors and normal tissues respond to fractionated radiation treatment.
2) When radiation is delivered in two fractions separated by time, cell survival increases due to repair of sublethal damage between fractions. The increase peaks at 2-3 hours and then levels off due to repopulation.
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Radiotherapy /certified fixed orthodontic courses by Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
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0091-9248678078
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Beam directed radiotherapy aims to deliver a homogenous tumor dose while minimizing radiation to normal tissues. It involves careful patient positioning, immobilization, tumor localization, field selection, dose calculations, and verification. Key steps include using positioning aids and molds to reproducibly position the patient, imaging such as CT to delineate the tumor volume, contouring to define external body outlines, and dose calculations and verification to ensure accurate delivery.
Altered fractionation kiran
The document discusses various radiation fractionation schedules used in cancer treatment. It begins with an overview of conventional fractionation, which divides the total radiation dose into smaller daily doses to allow healthy cells to repair sublethal damage between fractions. It then explores the radiobiological rationale of the 5 R's of fractionation - repair, redistribution, reoxygenation, repopulation, and radiosensitivity. The document discusses various altered fractionation schedules including hyperfractionation, accelerated fractionation, split-course, and hypofractionation, explaining how each schedule aims to improve the therapeutic ratio for cancer patients.
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The document discusses cell survival curves, which describe the relationship between radiation dose and the proportion of cells that survive. It defines key terms like clonogenic cells and explains the components of in vitro survival curves. It describes exponential and shoulder survival curves based on single-hit and multi-target theories. The mechanisms of cell killing like mitotic death and apoptosis are covered. Factors influencing radiosensitivity like dose rate, oxygen level and genetic mutations are summarized. Comparisons are made between survival curves of different mammalian cell types and microorganisms.
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This document discusses central axis depth doses in water for both SSD and SAD techniques. For SSD technique:
- Percentage depth dose (PDD) curves measure attenuation at different depths and are affected by beam quality, field size, and SSD.
- Buildup region occurs as secondary electrons deposit energy downstream, increasing dose with depth until maximum.
- Depth dose maximum (zmax) depends on beam energy and field size.
- PDD increases with larger field sizes due to increased scatter radiation.
- PDD increases with longer SSD due to the inverse square law of radiation intensity.
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1) The document discusses various factors that affect radiation response, including linear energy transfer (LET), relative biological effectiveness (RBE), oxygen effect, and cell cycle phase.
2) It provides details on oxygen enhancement ratio (OER), describing how it ranges from 2.5-3.0 for x-rays and varies according to cell cycle phase and radiation type (higher for x-rays and neutrons vs. alpha particles).
3) LET is discussed in relation to radiation type (low for x-rays, medium for neutrons, high for alpha particles) and how it impacts ionization density and biological damage. An optimal LET of around 100 keV/μm is described.
Total body irradiation
This document provides information about total body irradiation (TBI). It discusses that TBI uses megavoltage photon beams to destroy the recipient's bone marrow and tumor cells prior to bone marrow transplantation. It is used to treat various diseases like leukemia, lymphoma, and multiple myeloma. TBI can be delivered at high or low doses, to half the body, or total nodes. Techniques include parallel opposed beams from linear accelerators or cobalt-60 machines. Dosimetry and in vivo dosimetry are important due to the large fields and difficulty achieving uniform dose. Complications can include sterility, secondary cancers, and growth issues.
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This document discusses various techniques used for treatment verification in radiation therapy. It describes electronic portal imaging devices (EPID) which can be used for daily treatment localization and verification through portal images with little additional dose. Cone beam computed tomography (CBCT) is also discussed, which provides volumetric CT images with submillimeter resolution, allowing verification of patient positioning before treatment. Both EPID and CBCT help ensure the correct radiation dose is delivered to the intended target volume.
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This document discusses various beam modification devices used in radiation therapy to modify the spatial distribution of radiation within the patient. It describes different types of devices such as shielding blocks, wedges, compensators, multileaf collimators, and bolus. Shielding blocks are used to protect critical organs and reduce unnecessary dose to surrounding normal tissues. Wedge filters are used to tilt the isodose curves. Compensators even out skin surface contours and allow normal dose distributions to be applied to irregular surfaces. Multileaf collimators can dynamically shape radiation fields and are important for intensity-modulated radiation therapy. Bolus is used to reduce the depth of maximum dose for superficial lesions.
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describes relationship between radiation dose and the fraction of cells that “survive” that dose
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target model
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TSET
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Chap 5 fractionated radiation and the dose rate effect
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Quantec dr. upasna saxena (2)
This document discusses normal tissue tolerance doses from radiation therapy. It describes the formation of a task force to establish tolerance protocols, with an emphasis on partial volume effects. The earliest publication of tolerance doses is cited from 1972. 28 critical organ sites were included and considered in terms of dose, time factors, and partial volumes irradiated. The significance of these parameters and a quantitative model for normal tissue complication probability are provided. Limitations of the available data and ongoing areas of research are also outlined.
Fractionated radiation and dose rate effect
Fractionated radiation and the dose-rate effect can impact cell survival through mechanisms like sublethal damage (SLD) repair and cell cycle redistribution. SLD repair occurs as double-strand breaks are rejoined after radiation exposure. At lower dose rates, more SLD can be repaired between fractions, improving cell survival. However, very low dose rates may instead reduce survival if cells become frozen in radiosensitive phases of the cell cycle. The dose-rate effect varies between cell types and depends on factors like oxygenation and ability to progress through the cell cycle after radiation.
Treatment verification and set up errors
This document discusses the importance of treatment verification in radiotherapy and outlines the process. It notes that even small errors can have negative consequences so treatment verification is essential to ensure the right dose is delivered to the right area. The key aspects of treatment verification are machine setup, monitor units, patient positioning and imaging by comparing images to references. Errors can be systematic from planning or random from daily variations; various methods are described to reduce errors and ensure treatments are accurately delivered.
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This document discusses planned and unplanned gaps in radiation therapy treatment schedules. Planned gaps are built into the schedule to account for tumor repopulation during weekends and holidays. Unplanned gaps negatively impact treatment outcomes by prolonging the overall time and allowing tumors to regrow. The effects of gaps depend on the prolongation length, tumor proliferation rate, and timing of the interruption. Corrections like increasing the dose or number of fractions are sometimes made to account for biological effects of treatment gaps.
Electron beam therapy
Electron beam therapy uses accelerated electrons to treat superficial tumors. Electrons interact with matter through inelastic collisions that cause ionization and excitation, and elastic collisions that scatter the electrons. This gives electron beams a characteristically sharp dose drop-off beyond the tumor depth. Key applications of electron beams include treatment of skin cancers, chest wall irradiation for breast cancer, and boost doses to lymph nodes.
4 r's of radiobiology and dose rate effects
1) The four Rs of radiobiology are repair, re-assortment, repopulation, and re-oxygenation. They influence how tumors and normal tissues respond to fractionated radiation treatment.
2) When radiation is delivered in two fractions separated by time, cell survival increases due to repair of sublethal damage between fractions. The increase peaks at 2-3 hours and then levels off due to repopulation.
3) Lowering the radiation dose rate generally decreases biological effects because it allows more time for repair of sublethal damage.
Icru reports in external beam radiotherapy
The document summarizes key ICRU reports related to external beam radiotherapy, including ICRU Reports 29, 50, and 62. Report 29 established definitions like target volume, treatment volume, and organs at risk. Report 50 refined definitions and introduced clinical target volume, planning target volume, and treated volume. Report 62 further refined margins and introduced internal margin and setup margin. It also defined planning organ at risk volume and conformity index. The reports provide recommendations for dose reporting including minimum, maximum, and reference doses.
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This document provides an overview of interstitial brachytherapy principles and concepts. It discusses the history and evolution of brachytherapy sources from radium to modern radioactive sources like iridium-192. Key concepts covered include dose rate calculations, implant systems like the Paris system, and factors that influence dose distribution from a radioactive source like distance, absorption and scattering. The document also describes temporary and permanent brachytherapy sources and different methods of source application including preloading, afterloading and remote afterloading.
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Fractionation in radiotherapy refers to dividing the total radiation dose into smaller doses given over multiple treatment sessions. This allows healthy cells to repair sublethal damage between fractions while maximizing cancer cell kill through mechanisms like redistribution and reoxygenation. The "5 R's" of radiobiology explain fractionation: repair of sublethal damage in normal cells; redistribution of tumor cells to sensitive phases; reoxygenation of hypoxic tumor cells; repopulation of tumor cells during prolonged treatment; and intrinsic radiosensitivity differences between cell types. Fractionation schedules are tailored based on these factors to improve the therapeutic ratio for different cancers and patients.
Role of radiotherapy in oral ca ppt for csm
Radiotherapy plays an important role in the management of oral cancer. It uses ionizing radiation to deliver tumoricidal doses to cancer while limiting dose to surrounding normal tissues. There are several techniques of radiotherapy including external beam therapy and brachytherapy. Factors like total radiation dose, chemotherapy combination, treatment delays and interruptions can influence effectiveness. Complications include both early side effects like mucositis and late effects like osteoradionecrosis. Advances in radiotherapy techniques aim to improve targeting accuracy and reduce side effects.
Radiotherapy and chemotherapy in Oral cancer management
This document discusses the use of radiotherapy and chemotherapy in the management of oral cancer. It provides details on different treatment modalities including external beam radiation therapy, intensity modulated radiation therapy, brachytherapy, and chemotherapy. It also covers topics like dental preparation before radiation treatment, acute and late side effects of radiation therapy including xerostomia, and approaches to manage radiation-associated complications.
radition.pdf
This document provides an overview of radiation therapy and its therapeutic index for cancer treatment. It discusses how radiation damages DNA in cancer cells, the biologic basis involving differential repair between normal and cancerous tissues. Fractionation is explained as dividing the total dose into smaller daily fractions over weeks to spare normal tissues through repair while increasing damage to tumors. Clinical uses of radiation to cure cancer or palliate symptoms are described. The treatment process including simulation, planning and delivery is covered along with common side effects and palliative applications of radiation therapy.
Foundation of Radiotherapy (RT)
Radiotherapy uses ionizing radiation to treat malignant tumors. The effectiveness of radiotherapy depends on properly selecting the radiation type, dose, and fractioning schedule based on the tumor's characteristics and location. The goal is to deliver a high enough dose to destroy cancer cells while minimizing damage to healthy tissues. A full radiotherapy course involves planning treatment, delivering the planned radiation, and monitoring the patient's response post-treatment.
BOOK ON REIRRADIATION
1. Re-irradiation involves delivering a second course of radiation to patients who develop recurrent or new primary tumors in an area previously treated with radiation. It requires careful patient selection and consideration of normal tissue tolerance to minimize toxicity risks.
2. A multidisciplinary evaluation is necessary to determine if re-irradiation provides a survival or palliative benefit over other treatment options like chemotherapy or surgery. Factors like tumor type, initial treatment details, disease control, and patient performance status must be considered.
3. Advanced radiation techniques like IMRT can help spare nearby organs-at-risk and lower toxicity when used for re-irradiation. Close monitoring during treatment is still needed to watch for normal tissue complications.
Oncology
This document discusses principles of cancer therapy and different treatment modalities, including surgery, radiation therapy, and chemotherapy. It provides details on each treatment type, how they work to target cancer cells, their goals and side effects. The key points are:
1) The main treatment modalities are surgery, radiation therapy, chemotherapy and immunotherapy. Each aims to eliminate cancer cells while limiting harm to healthy tissue.
2) Surgery aims to entirely remove the cancer, but recurrence is possible if microscopic cells remain. Radiation therapy damages DNA in cancer cells to stop growth and division.
3) While treatments aim to cure, controlling symptoms and improving quality of life are also important goals, as curing all cancers is unlikely
Re Radiation
- Reirradiation or retreatments after initial radiotherapy is possible for 10% of cancer patients who experience a second cancer. However, if the radiation tolerance of a normal organ or tissue was exceeded in the initial treatment, reirradiation cannot be done safely.
- Early-responding tissues like skin generally recover better than late-responding tissues like fibrosis and can tolerate reirradiation with reduced doses. Spinal cord and lung data from rodent and monkey studies show some reirradiation is possible. Kidney and bladder do not recover from late damage.
- Clinical studies on reirradiation are limited but show it can provide local control and possibly survival for head and neck cancers, though with high risks of toxicity and functional
Radiation oncology
The document discusses various aspects of radiation oncology and radiotherapy clinical trial design. It provides an overview of the evolution of radiation therapy techniques from the 1960s to present. It also covers important considerations for radiation oncology trials, including target volume delineation, dose schedules, quality assurance measures, and assessing toxicity. Multidisciplinary collaboration and factors influencing radiation sensitivity are also briefly discussed.
RE-IRRADIATION IN HEAD AND NECK CANCER
Reirradiation can provide local tumor control for recurrent head and neck cancer when surgery is not possible. Modern radiation techniques like IMRT allow higher radiation doses to be safely delivered to the tumor while minimizing risks of severe toxicity. Outcomes from reirradiation include a median survival of 10-12 months and 2-year local control rates of 40-64%. Patient selection is important to balance potential benefits of local tumor control against risks of treatment-related side effects.
Stereotactic body radiotherapy
Stereotactic body radiotherapy (SBRT) delivers high-dose radiation to tumors in a small number of fractions using high precision. For prostate SBRT, the target and organs at risk are contoured on planning CT. A dose of 35-38Gy in 5 fractions is used as primary treatment for low risk prostate cancer. Rigid image guidance and intrafraction monitoring are important to minimize setup errors. ExacTrac X-ray positioning co-registers X-rays with digitally reconstructed radiographs and corrects for rotational and translational deviations, achieving sub-millimeter accuracy. This allows safe dose escalation for prostate SBRT.
Recent advances in radiation oncology final (1)
The document discusses recent advances in radiation oncology. It describes how radiation therapy works, the treatment process from simulation to delivery, different radiation techniques including IMRT and proton beam therapy, and types of radiation such as external beam and brachytherapy. It also covers the radiation oncology team, basic principles of fractionation and the four R's of radiobiology, clinical uses of radiation to cure or palliate cancer, and potential acute and late side effects of treatment.
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Radiotherapy /certified fixed orthodontic courses by Indian dental academy
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Radiotherapy and chemotherapy in Oral cancer management
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- 71. THANK YOU