Altered fractionation schedules in radiation oncologyAbhishek Soni
Altered fractionation schedules aim to optimize tumor control and normal tissue sparing by manipulating total dose, dose per fraction, time interval between fractions, dose rate, and overall treatment time based on tumor and tissue radiosensitivity and repair characteristics. Hyperfractionation uses a higher total dose with smaller, more frequent fractions to exploit tumor reoxygenation and cell cycle effects while hypofractionation uses fewer, larger fractions which is more effective for tumors with low α/β ratios. Accelerated fractionation decreases treatment time to limit tumor repopulation at the cost of increased acute toxicity. Phase III trials show hyperfractionation and accelerated fractionation improve local control for head and neck cancers with acceptable toxicity.
The document discusses the concepts of biological effective dose (BED) and equivalent dose in 2 Gy fractions (EQD2). BED represents the total dose required to achieve a specific biological effect based on the dose per fraction and overall treatment time. EQD2 provides a more practical dose value for clinical use by converting BED to an equivalent total dose given in 2 Gy fractions. The document provides examples of calculating BED and EQD2 for different fractionation schedules and discusses applications in isoeffective dose comparisons and interpreting clinical trial results.
Mlc;multi leaf collimators of variuos companieszahramansouri
This document discusses the three basic applications of multileaf collimators (MLCs) in radiation therapy: 1) replacing conventional blocking, 2) matching the beam's eye view to the planning target volume during arc rotation, and 3) achieving beam intensity modulation. It also describes the material properties of tungsten alloy that make it well-suited for MLC leaf construction, including its high density, hardness, low cost, and low coefficient of expansion. Finally, it briefly mentions mini MLCs and the MIMiC system.
1. The Manchester system was one of the first standardized methods for interstitial brachytherapy implantation using radium sources. It provided rules for determining the amount of radium needed, its distribution, and dose specification based on the treatment area, distance, and desired total dose.
2. The amount of radium was calculated using exposure rates and tables that specified milligram hours of radium per 1000 rads of exposure for different areas and distances. The distribution of radium sources followed the inverse square law to achieve uniform dosing within 10% across the target area.
3. The system defined geometric terms and provided specific rules for distributing radium sources in planar moulds that were circular, square,
Quality assurance of linear accelerator DHXSohail Qureshi
This document outlines the daily quality assurance procedure for a linear accelerator. It describes turning on the machine, performing mechanical checks like gantry and couch movement tests, warming up the machine using various electron and photon energies, and performing dosimetry measurements to ensure parameters are within tolerance levels. Results are documented in a QA sheet for record keeping. The purpose is to ensure consistent machine quality and patient safety by verifying proper dose delivery and checking for any mechanical or software errors.
This document discusses the clinical implementation of volumetric modulated arc therapy (VMAT) at UT M.D. Anderson Cancer Center. It provides an overview of VMAT, the advantages it offers over other radiation therapy techniques, and the steps taken to configure the accelerator, treatment planning system, and quality assurance processes for VMAT delivery. Key aspects covered include accelerator prerequisites, TPS commissioning, patient-specific quality assurance using films and ion chambers, monthly constancy checks, and tips for rapid arc treatment planning for prostate cases.
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.
This document provides an overview of planning systems in radiotherapy and discusses various topics related to clinical treatment planning using computerized treatment planning systems. It begins with an introduction to the author and their experience with different treatment planning systems. It then covers definitions and concepts important for clinical treatment planning such as volumes, dose specifications, patient data acquisition, beam combinations, and dose statistics. The document also discusses virtual simulation, image fusion, treatment aids, oblique incidence corrections, and portal imaging. It provides details on the hardware, calculations algorithms, and commissioning of computerized treatment planning systems. In summary, the document offers a comprehensive review of clinical treatment planning processes and considerations for computerized treatment planning systems.
Altered fractionation schedules in radiation oncologyAbhishek Soni
Altered fractionation schedules aim to optimize tumor control and normal tissue sparing by manipulating total dose, dose per fraction, time interval between fractions, dose rate, and overall treatment time based on tumor and tissue radiosensitivity and repair characteristics. Hyperfractionation uses a higher total dose with smaller, more frequent fractions to exploit tumor reoxygenation and cell cycle effects while hypofractionation uses fewer, larger fractions which is more effective for tumors with low α/β ratios. Accelerated fractionation decreases treatment time to limit tumor repopulation at the cost of increased acute toxicity. Phase III trials show hyperfractionation and accelerated fractionation improve local control for head and neck cancers with acceptable toxicity.
The document discusses the concepts of biological effective dose (BED) and equivalent dose in 2 Gy fractions (EQD2). BED represents the total dose required to achieve a specific biological effect based on the dose per fraction and overall treatment time. EQD2 provides a more practical dose value for clinical use by converting BED to an equivalent total dose given in 2 Gy fractions. The document provides examples of calculating BED and EQD2 for different fractionation schedules and discusses applications in isoeffective dose comparisons and interpreting clinical trial results.
Mlc;multi leaf collimators of variuos companieszahramansouri
This document discusses the three basic applications of multileaf collimators (MLCs) in radiation therapy: 1) replacing conventional blocking, 2) matching the beam's eye view to the planning target volume during arc rotation, and 3) achieving beam intensity modulation. It also describes the material properties of tungsten alloy that make it well-suited for MLC leaf construction, including its high density, hardness, low cost, and low coefficient of expansion. Finally, it briefly mentions mini MLCs and the MIMiC system.
1. The Manchester system was one of the first standardized methods for interstitial brachytherapy implantation using radium sources. It provided rules for determining the amount of radium needed, its distribution, and dose specification based on the treatment area, distance, and desired total dose.
2. The amount of radium was calculated using exposure rates and tables that specified milligram hours of radium per 1000 rads of exposure for different areas and distances. The distribution of radium sources followed the inverse square law to achieve uniform dosing within 10% across the target area.
3. The system defined geometric terms and provided specific rules for distributing radium sources in planar moulds that were circular, square,
Quality assurance of linear accelerator DHXSohail Qureshi
This document outlines the daily quality assurance procedure for a linear accelerator. It describes turning on the machine, performing mechanical checks like gantry and couch movement tests, warming up the machine using various electron and photon energies, and performing dosimetry measurements to ensure parameters are within tolerance levels. Results are documented in a QA sheet for record keeping. The purpose is to ensure consistent machine quality and patient safety by verifying proper dose delivery and checking for any mechanical or software errors.
This document discusses the clinical implementation of volumetric modulated arc therapy (VMAT) at UT M.D. Anderson Cancer Center. It provides an overview of VMAT, the advantages it offers over other radiation therapy techniques, and the steps taken to configure the accelerator, treatment planning system, and quality assurance processes for VMAT delivery. Key aspects covered include accelerator prerequisites, TPS commissioning, patient-specific quality assurance using films and ion chambers, monthly constancy checks, and tips for rapid arc treatment planning for prostate cases.
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.
This document provides an overview of planning systems in radiotherapy and discusses various topics related to clinical treatment planning using computerized treatment planning systems. It begins with an introduction to the author and their experience with different treatment planning systems. It then covers definitions and concepts important for clinical treatment planning such as volumes, dose specifications, patient data acquisition, beam combinations, and dose statistics. The document also discusses virtual simulation, image fusion, treatment aids, oblique incidence corrections, and portal imaging. It provides details on the hardware, calculations algorithms, and commissioning of computerized treatment planning systems. In summary, the document offers a comprehensive review of clinical treatment planning processes and considerations for computerized treatment planning systems.
Smart radiotherapy aims to precisely target tumor cells while sparing healthy cells. New techniques described in the document include using hypoxic cell sensitizers to target hypoxic tumor regions, anti-angiogenic agents to inhibit tumor blood vessels, and nanoparticles to enhance radiation dose and selectively deliver drugs. Molecular imaging helps optimize treatment by identifying tumor characteristics. Combining radiotherapy with immunotherapy or targeted depletion of host cells may also improve outcomes. Overall, the document discusses developing more precise radiation approaches through better understanding of tumor biology and microenvironment.
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
Low dose rate versus high dose rate brachytherapy for carcinoma cervixRam Abhinav
Carcinoma cervix is the second most commonly occuring cancer in India.
Brachytherapy forms the most important part radiation therapy
Low dose rate Brachytherapy – Gold Standard
Experience more than a century
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.
LDR and HDR Brachytherapy: A Primer for non radiation oncologistsSantam Chakraborty
A small presentation I made for a 30 minutes class comparing and contrasting LDR and HDR brachytherapy. Good for a person with non radiation oncology background to grasp the basics.
Radioisotopes and dose rates used for brachytherapySubhash Thakur
Radioisotopes and dose rates used for brachytherapy
This is the seminar about different radioisotopes used in brachytherapy beginning from radium to iradium and different dose rates, low dose rate, high dose rate used in brachytherapy. The significance of different dose rates and its radiobiology along with the clinical results.
1) Electron beam therapy uses high-energy electrons between 6-20MeV to treat superficial tumors less than 5cm deep. It is useful for cancers of the skin, eye, breast, head and neck, and gastrointestinal tract.
2) Electron beams have distinct advantages over x-rays and brachytherapy in minimizing dose to deeper tissues and providing dose uniformity.
3) The depth that receives 90% of the maximum dose, called R90, is typically one-third to one-fourth of the electron energy in MeV. This determines the maximum treatment depth.
Final ICRU 62 ( International commission on radiation units and measurements)DrAyush Garg
The document discusses recommendations from reports by the International Commission on Radiation Units and Measurements (ICRU) for defining volumes used in radiation therapy planning and reporting. ICRU Report 62 provides additional details on volumes such as the internal target volume (ITV) and planning organ at risk volume (PRV), and introduces metrics like the conformity index. It also further classifies organs at risk as serial, parallel or serial-parallel based on their radiosensitivity.
This document discusses various time-dose models used in radiotherapy, including the Strandqvist, Cohen, NSD, and TDF models. It explains the need for these models to optimize treatment regimes for tumor control while sparing normal tissues. The document also covers gap correction factors used when treatment schedules are interrupted and the various factors that can affect tumor control outcomes due to gaps in treatment. Compensatory methods like accelerated scheduling and increased dosing are presented to account for treatment gaps.
1. The document discusses various aspects of intensity-modulated radiation therapy (IMRT) planning and delivery, including the use of inverse planning, optimization objectives and constraints, and different delivery methods like static field, dynamic field, tomotherapy, and VMAT.
2. It also discusses treatment volumes defined in ICRU 83 like gross tumor volume, clinical target volume, planning target volume, and organ-at-risk volumes. The document emphasizes using dose-volume histograms to specify dose rather than a single point.
3. Challenges with overlapping treatment volumes and the importance of evaluating the remaining volume at risk are also covered.
1) The document discusses various techniques for radiation therapy treatment planning and delivery for breast cancer, including tangential field planning, supraclavicular field matching, electron boosts, and accelerated partial breast irradiation.
2) Techniques for accelerated partial breast irradiation discussed include multi-catheter interstitial brachytherapy, balloon-based brachytherapy using devices like Mammosite, and external beam radiation therapy.
3) Factors that determine suitability for accelerated partial breast irradiation include patient age, tumor size and characteristics, and nodal involvement. Dosage schedules and advantages and disadvantages of different techniques are also reviewed.
Electron beam radiotherapy uses megavoltage electron beams ranging from 6-20 MeV to treat superficial tumors within 6 cm of the skin surface. It provides a uniform dose at a specified depth with rapid dose fall-off, sparing deeper tissues. Common tumors treated include skin, lymphomas, and breast cancer. Electrons deposit dose via interactions like collision and scattering. Dose distribution is characterized by a rapid buildup to a maximum within 1 cm followed by a rapid falloff beyond the treatment depth.
This document discusses motion management techniques for lung cancer radiotherapy. It begins by explaining why motion management is important, as standard CT scans do not fully capture lung tumor motion. It then describes 4DCT and other methods for assessing tumor motion, as well as techniques like ITV, gating, tracking and breath-holding to control for motion. Specific examples of tracking systems like ExacTrac and Cyberknife are provided. Overall, the document provides an overview of the challenges of lung tumor motion and different strategies used to manage it in radiation treatment planning and delivery.
1. ICRU Report 83 provides guidelines for prescribing, recording, and reporting intensity-modulated radiation therapy (IMRT). It emphasizes using dose-volume histograms and statistics like median dose to describe dose distributions.
2. The report outlines three levels of prescribing and reporting with increasing complexity. Level 1 involves basic 2D dose distributions while Level 3 incorporates more advanced metrics like tumor control probability.
3. Key volumes discussed include gross tumor volume, clinical target volume, planning target volume, and organs at risk. The report standardized how to account for uncertainties and patient motion when defining these volumes.
This document summarizes key aspects of the International Commission on Radiation Units and Measurements (ICRU) Report 83 from 2010 on prescribing, recording, and reporting photon beam intensity-modulated radiation therapy (IMRT). The ICRU Report 50 from 1993 and Report 62 from 1999 established guidelines for defining target volumes like gross tumor volume, clinical target volume, and planning target volume. ICRU Report 83 aimed to update these guidelines for IMRT, which uses non-uniform fluence and dose distributions compared to earlier conformal radiation techniques. Key changes included separating the planning target volume into internal and setup margins, classifying organs at risk, and defining new metrics like the planning organ at risk volume and conformity index for evaluating IM
This document provides a history of brachytherapy and its evolution for treating cervical cancer. It discusses the early use of radium-222 and the development of intracavitary systems like Stockholm, Paris, and Manchester. Point A dose prescription and applicator design evolved over time. Later sources included cesium-137, iridium-192, and cobalt-60 used in remote afterloading. Overall, the document traces the development of brachytherapy techniques and technology for cervical cancer from the discovery of radiation to modern high dose rate treatments.
This document discusses the history and techniques of stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT). It begins by outlining the early development of SRS by Lars Leksell in the 1950s. It then defines key terms like SRS, SBRT, and fractionated stereotactic radiosurgery. The document goes on to discuss the rationale and advantages of SRS/SBRT, including its ability to deliver high radiation doses with steep dose gradients using multiple beams and image guidance. It also covers topics like tumor oxygenation, cell kill mechanisms, and recent technological advances in the field like VMAT, flattening filter free beams, and 4D
Brachytherapy involves placing radioactive sources inside or near the target tissue. It began in 1898 with radium and has evolved with different radioactive isotopes and delivery methods. Common isotopes used today include iridium-192, cesium-137, palladium-103, iodine-125, and gold-198, which are used for interstitial, intracavitary, or permanent implantation depending on the clinical application and isotope properties.
1) The document discusses various radiation techniques for treating cancer of the esophagus including 2D, 3D conformal radiation therapy, IMRT, and IGRT.
2) It covers topics like target volume delineation, field design considerations for different esophageal subsites, and evolution from 2D to 3D treatment planning.
3) While there is no consensus, most contemporary trials use margins of 3-5cm cranially and caudally on the gross tumor with approximately a 2cm radial margin.
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.
Cell survival curves describe the relationship between radiation dose and the fraction of cells that survive that dose. The linear-quadratic model best approximates actual cell kill after radiation exposure using two constants, α and β, which can predict dose response for specific tissues. The α/β ratio quantifies a tissue's sensitivity to fractionated radiation, with a low ratio indicating greater sensitivity to fraction size changes. Multiple factors like linear energy transfer, fractionation, dose rate, and oxygen presence can impact the shape of survival curves.
Smart radiotherapy aims to precisely target tumor cells while sparing healthy cells. New techniques described in the document include using hypoxic cell sensitizers to target hypoxic tumor regions, anti-angiogenic agents to inhibit tumor blood vessels, and nanoparticles to enhance radiation dose and selectively deliver drugs. Molecular imaging helps optimize treatment by identifying tumor characteristics. Combining radiotherapy with immunotherapy or targeted depletion of host cells may also improve outcomes. Overall, the document discusses developing more precise radiation approaches through better understanding of tumor biology and microenvironment.
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
Low dose rate versus high dose rate brachytherapy for carcinoma cervixRam Abhinav
Carcinoma cervix is the second most commonly occuring cancer in India.
Brachytherapy forms the most important part radiation therapy
Low dose rate Brachytherapy – Gold Standard
Experience more than a century
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.
LDR and HDR Brachytherapy: A Primer for non radiation oncologistsSantam Chakraborty
A small presentation I made for a 30 minutes class comparing and contrasting LDR and HDR brachytherapy. Good for a person with non radiation oncology background to grasp the basics.
Radioisotopes and dose rates used for brachytherapySubhash Thakur
Radioisotopes and dose rates used for brachytherapy
This is the seminar about different radioisotopes used in brachytherapy beginning from radium to iradium and different dose rates, low dose rate, high dose rate used in brachytherapy. The significance of different dose rates and its radiobiology along with the clinical results.
1) Electron beam therapy uses high-energy electrons between 6-20MeV to treat superficial tumors less than 5cm deep. It is useful for cancers of the skin, eye, breast, head and neck, and gastrointestinal tract.
2) Electron beams have distinct advantages over x-rays and brachytherapy in minimizing dose to deeper tissues and providing dose uniformity.
3) The depth that receives 90% of the maximum dose, called R90, is typically one-third to one-fourth of the electron energy in MeV. This determines the maximum treatment depth.
Final ICRU 62 ( International commission on radiation units and measurements)DrAyush Garg
The document discusses recommendations from reports by the International Commission on Radiation Units and Measurements (ICRU) for defining volumes used in radiation therapy planning and reporting. ICRU Report 62 provides additional details on volumes such as the internal target volume (ITV) and planning organ at risk volume (PRV), and introduces metrics like the conformity index. It also further classifies organs at risk as serial, parallel or serial-parallel based on their radiosensitivity.
This document discusses various time-dose models used in radiotherapy, including the Strandqvist, Cohen, NSD, and TDF models. It explains the need for these models to optimize treatment regimes for tumor control while sparing normal tissues. The document also covers gap correction factors used when treatment schedules are interrupted and the various factors that can affect tumor control outcomes due to gaps in treatment. Compensatory methods like accelerated scheduling and increased dosing are presented to account for treatment gaps.
1. The document discusses various aspects of intensity-modulated radiation therapy (IMRT) planning and delivery, including the use of inverse planning, optimization objectives and constraints, and different delivery methods like static field, dynamic field, tomotherapy, and VMAT.
2. It also discusses treatment volumes defined in ICRU 83 like gross tumor volume, clinical target volume, planning target volume, and organ-at-risk volumes. The document emphasizes using dose-volume histograms to specify dose rather than a single point.
3. Challenges with overlapping treatment volumes and the importance of evaluating the remaining volume at risk are also covered.
1) The document discusses various techniques for radiation therapy treatment planning and delivery for breast cancer, including tangential field planning, supraclavicular field matching, electron boosts, and accelerated partial breast irradiation.
2) Techniques for accelerated partial breast irradiation discussed include multi-catheter interstitial brachytherapy, balloon-based brachytherapy using devices like Mammosite, and external beam radiation therapy.
3) Factors that determine suitability for accelerated partial breast irradiation include patient age, tumor size and characteristics, and nodal involvement. Dosage schedules and advantages and disadvantages of different techniques are also reviewed.
Electron beam radiotherapy uses megavoltage electron beams ranging from 6-20 MeV to treat superficial tumors within 6 cm of the skin surface. It provides a uniform dose at a specified depth with rapid dose fall-off, sparing deeper tissues. Common tumors treated include skin, lymphomas, and breast cancer. Electrons deposit dose via interactions like collision and scattering. Dose distribution is characterized by a rapid buildup to a maximum within 1 cm followed by a rapid falloff beyond the treatment depth.
This document discusses motion management techniques for lung cancer radiotherapy. It begins by explaining why motion management is important, as standard CT scans do not fully capture lung tumor motion. It then describes 4DCT and other methods for assessing tumor motion, as well as techniques like ITV, gating, tracking and breath-holding to control for motion. Specific examples of tracking systems like ExacTrac and Cyberknife are provided. Overall, the document provides an overview of the challenges of lung tumor motion and different strategies used to manage it in radiation treatment planning and delivery.
1. ICRU Report 83 provides guidelines for prescribing, recording, and reporting intensity-modulated radiation therapy (IMRT). It emphasizes using dose-volume histograms and statistics like median dose to describe dose distributions.
2. The report outlines three levels of prescribing and reporting with increasing complexity. Level 1 involves basic 2D dose distributions while Level 3 incorporates more advanced metrics like tumor control probability.
3. Key volumes discussed include gross tumor volume, clinical target volume, planning target volume, and organs at risk. The report standardized how to account for uncertainties and patient motion when defining these volumes.
This document summarizes key aspects of the International Commission on Radiation Units and Measurements (ICRU) Report 83 from 2010 on prescribing, recording, and reporting photon beam intensity-modulated radiation therapy (IMRT). The ICRU Report 50 from 1993 and Report 62 from 1999 established guidelines for defining target volumes like gross tumor volume, clinical target volume, and planning target volume. ICRU Report 83 aimed to update these guidelines for IMRT, which uses non-uniform fluence and dose distributions compared to earlier conformal radiation techniques. Key changes included separating the planning target volume into internal and setup margins, classifying organs at risk, and defining new metrics like the planning organ at risk volume and conformity index for evaluating IM
This document provides a history of brachytherapy and its evolution for treating cervical cancer. It discusses the early use of radium-222 and the development of intracavitary systems like Stockholm, Paris, and Manchester. Point A dose prescription and applicator design evolved over time. Later sources included cesium-137, iridium-192, and cobalt-60 used in remote afterloading. Overall, the document traces the development of brachytherapy techniques and technology for cervical cancer from the discovery of radiation to modern high dose rate treatments.
This document discusses the history and techniques of stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT). It begins by outlining the early development of SRS by Lars Leksell in the 1950s. It then defines key terms like SRS, SBRT, and fractionated stereotactic radiosurgery. The document goes on to discuss the rationale and advantages of SRS/SBRT, including its ability to deliver high radiation doses with steep dose gradients using multiple beams and image guidance. It also covers topics like tumor oxygenation, cell kill mechanisms, and recent technological advances in the field like VMAT, flattening filter free beams, and 4D
Brachytherapy involves placing radioactive sources inside or near the target tissue. It began in 1898 with radium and has evolved with different radioactive isotopes and delivery methods. Common isotopes used today include iridium-192, cesium-137, palladium-103, iodine-125, and gold-198, which are used for interstitial, intracavitary, or permanent implantation depending on the clinical application and isotope properties.
1) The document discusses various radiation techniques for treating cancer of the esophagus including 2D, 3D conformal radiation therapy, IMRT, and IGRT.
2) It covers topics like target volume delineation, field design considerations for different esophageal subsites, and evolution from 2D to 3D treatment planning.
3) While there is no consensus, most contemporary trials use margins of 3-5cm cranially and caudally on the gross tumor with approximately a 2cm radial margin.
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.
Cell survival curves describe the relationship between radiation dose and the fraction of cells that survive that dose. The linear-quadratic model best approximates actual cell kill after radiation exposure using two constants, α and β, which can predict dose response for specific tissues. The α/β ratio quantifies a tissue's sensitivity to fractionated radiation, with a low ratio indicating greater sensitivity to fraction size changes. Multiple factors like linear energy transfer, fractionation, dose rate, and oxygen presence can impact the shape of survival curves.
Cell survival curves describe the relationship between radiation dose and the fraction of cells that survive that dose. They are used to assess the biological effectiveness of radiation. The curves follow an exponential relationship, with cell killing increasing exponentially with dose. Two common models used to describe survival curves are the linear-quadratic model and the multi-target model. Key parameters of the curves include D0, D10, and the shoulder width, which provide information about a cell's radiosensitivity. Factors like LET, fractionation, dose rate, cell type, and oxygen presence can impact the shape and slope of the 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
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.
It describes relationship between radiation dose and the fraction of cells that “survive” that dose.
This is mainly used to assess biological effectiveness of radiation.
To understand it better, we need to know about a few basic things e.g.
Cell Death
Estimation of Survival / Plating Efficiency
Nature of Cell killing etc.
A cell survival curve is the relationship between the fraction of cells retaining their reproductive integrity and absorbed dose.
Conventionally, surviving fraction on a logarithmic scale is plotted on the Y-axis, the dose is on the X-axis . The shape of the survival curve is important.
The cell-survival curve for densely ionizing radiations (α-particles and low-energy neutrons) is a straight line on a log-linear plot, that is survival is an exponential function of dose.
The cell-survival curve for sparsely ionizing radiations (X-rays, gamma-rays has an initial slope, followed by a shoulder after which it tends to straighten again at higher doses.
Evolution of Fractionation and Conventional Fractionation in RadiotherapyNikhil Sebastian
The document discusses the evolution of radiation fractionation in cancer treatment. Early radiation machines had low output, so delivering a tumoricidal dose as a single fraction would have caused unacceptable toxicity. Fractionation was used from the beginning. Over the following decades, two schools of thought emerged on fractionation - the Erlangen school believed single large doses were necessary, while the Paris school's experiments on animal models supported fractionation. Clinical results in the 1930s also showed fractionation produced better tumor control with less toxicity. The rationale for fractionation is based on the different cell kinetics of normal and tumor cells, allowing sparing of normal tissues. Mathematical models were later developed to quantify fractionation schedules, incorporating factors like overall time, dose per
Glimpse of clinical radiobiology courseManoj Gupta
This document provides an overview of key concepts in clinical radiobiology. It discusses how ionizing radiation interacts with matter and cells, causing ionization which can lead to cell death. The attenuation of radiation as it passes through different tissues is described, as well as different radiation interactions like the photoelectric effect. Cell survival curves are introduced, showing their exponential nature and how factors like oxygenation and fractionation affect the curves. The linear quadratic model is explained. Finally, the four R's of radiobiology - reoxygenation, redistribution, repopulation and repair - are summarized as the basis for fractionated radiotherapy.
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.
- Cell survival curves relate the radiation dose to the proportion of cells that survive. They are generated through in vitro experiments where cells are exposed to radiation doses and then assessed for their ability to proliferate into colonies.
- The linear-quadratic model describes cell survival as having both a linear component related to single radiation hits and a quadratic component related to multiple radiation hits. It is used to design fractionated radiotherapy regimens and understand acute vs late tissue responses.
- Key factors in the model include the alpha coefficient representing intrinsic radiosensitivity, the beta coefficient representing repair capacity, and the alpha/beta ratio which indicates the dose where linear and quadratic death are equal.
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.
This document provides an overview of key concepts in radiobiology, including:
1. Ionizing radiation can cause direct and indirect DNA damage. DNA is the main cellular target of radiation.
2. The biological effects of radiation are determined by factors like DNA break type, cell cycle radiosensitivity, and the advantages of dose fractionation such as allowing time for repair between fractions.
3. Fractionation exploits differences in recovery rates between normal and tumor tissues, allowing higher total doses to be delivered to tumors while sparing normal tissues.
This document provides an overview of radiobiology concepts including cell biology, radiation interactions with matter, and cellular and tissue responses to radiation. Key points include:
- Cells are composed of inorganic components like water and salts, and organic components like proteins, carbohydrates, nucleic acids, and lipids. The cellular structures include the cytoplasm, cell membrane, organelles, nucleus and DNA.
- Radiation can directly or indirectly interact with targets in the cell. Indirect action through free radical production is more common. Higher linear energy transfer (LET) radiation like alpha particles is more effective at killing cells.
- Cell survival curves describe the relationship between radiation dose and surviving cells. The shape depends on LET, with
Cell survival curves relate the fraction of cells retaining reproductive integrity to radiation dose. Mammalian curves have an initial curved portion then become exponential. This shoulder represents sublethal damage repair. The linear-quadratic model is clinically used, describing cell kill as proportional to dose (αD) and dose-squared (βD2). α measures intrinsic radiosensitivity and β repair capacity. Their ratio determines curve shape and tissue type. Factors like oxygen level, proliferation, and fractionation influence survival curves. Cell survival curves are important for understanding radiation effects and optimizing fractionation schemes.
The document discusses the radiobiology behind dose fractionation in radiation therapy. It provides an overview of the linear quadratic model which describes how cell survival changes with dose and is used to determine biologically equivalent doses for different fractionation schedules. The model assumes equal effect per fraction but may not be accurate at high or low doses. Fractionation takes advantage of the four R's - repair, repopulation, redistribution, and reoxygenation - to better kill tumors while sparing normal tissues. The alpha/beta ratio indicates a tissue's sensitivity to fractionation and is used to estimate equivalent total doses for different fraction sizes.
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.
Fractionation of radiation doses allows normal tissues to repair sublethal damage between fractions through processes like repair, repopulation, and reoxygenation. This reduces damage to normal tissues compared to a single high dose. Tumor cells are sensitized by redistribution and reoxygenation. Hyperfractionation uses smaller doses more frequently to allow higher total doses while respecting normal tissue tolerance. Accelerated fractionation reduces treatment time to limit tumor regrowth. Dose rate effects occur as repair of sublethal damage reduces cell killing at lower dose rates, though some cell lines are more sensitive in G2 phase at very low dose rates in an inverse effect.
Fractionation involves dividing the total radiation dose into smaller daily fractions over the treatment period. This allows normal tissues to repair sublethal damage between fractions better than tumor tissues. Historical models like Stranquist cube root and Cohen's models related total dose and treatment time to biological effects. The linear quadratic model explains cell survival based on linear and quadratic components of radiation damage. Fractionation takes advantage of the four R's of radiobiology: repair of sublethal damage, repopulation, reoxygenation, and redistribution to improve the therapeutic ratio and deliver tumoricidal doses with minimal damage to surrounding normal tissues.
Similar to The Radiobiology Behind Dose Fractionation.pdf (20)
This document discusses different types of radiation used in radiation oncology. It describes the evolution from kilovoltage x-ray units to modern megavoltage linear accelerators. Key developments include the use of higher voltage x-rays called supervoltage therapy, and later the advent of megavoltage x-rays and electrons generated by linear accelerators. The document outlines the main components of linear accelerators including the electron gun, RF power source like klystrons or magnetrons, accelerating structure, and treatment head for beam shaping and monitoring.
Brachytherapy involves placing radioactive sources inside or next to the area requiring treatment. There are two main types - high dose rate (HDR) and low dose rate (LDR) brachytherapy. Sources must be encapsulated to protect against radiation exposure. Common photon-emitting sources used include iridium-192, cobalt-60, and cesium-137. Brachytherapy is commonly used as a boost with external beam radiation therapy (EBRT) or as a monotherapy for conditions like cervical, prostate, breast, and head and neck cancers. Dose specifications and fractionation schedules vary depending on the clinical application and brachytherapy technique used.
This case report describes the treatment of a 55-year-old male patient diagnosed with gastric diffuse large B-cell lymphoma (DLBCL) at the Portsudan Oncology Center in Sudan from August 2018 to July 2021. The patient received 8 cycles of CHOP chemotherapy, followed by 8 cycles of rituximab and 30GY radiotherapy to the gastric region and lymph nodes. The treatment resulted in regression of lesions. However, the patient later experienced a relapse and was treated with 8 cycles of ICE chemotherapy, with regression of lesions observed again. The report discusses DLBCL and the challenges of treating it at a small oncology center with limited resources and capabilities.
Protons are the dominant baryonic particle in the universe, comprising 87% of particle mass. Protons have a positive charge and are present in every atom, participating in all matter interactions. Proton therapy delivers a high radiation dose localized to the tumor site using proton beams, which deposit more energy at the tumor compared to X-rays due to the Bragg peak effect, sparing surrounding healthy tissues. Clinical applications of proton therapy include treatment of ocular melanoma, skull base and spine sarcomas, optic pathway gliomas, astrocytomas, and meningiomas.
This case report describes a 55-year-old man diagnosed with gastric diffuse large B-cell lymphoma (DLBCL) in 2018 in Port Sudan, Sudan. He received 8 cycles of CHOP chemotherapy, followed by 8 cycles of rituximab after a relapse in 2019. When a mesenteric lymph node mass recurred in 2021, he received 8 cycles of ICE chemotherapy. The report discusses DLBCL diagnosis, treatment challenges at the regional oncology center due to limited resources, and the patient's response to three lines of chemotherapy and radiotherapy over three years.
This case report describes a 55-year-old man diagnosed with gastric diffuse large B-cell lymphoma (DLBCL) in 2018 in Port Sudan, Sudan. He received 8 cycles of CHOP chemotherapy, followed by 8 cycles of rituximab after a relapse in 2019. When a mesenteric lymph node mass recurred in 2021, he received 8 cycles of ICE chemotherapy. The report discusses DLBCL diagnosis, treatment challenges at the regional oncology center due to limited resources, and the patient's response to three lines of chemotherapy and radiotherapy over three years.
Omer Hashim Mohammed Ebrahim is a radiation oncologist who has been practicing since July 2010. He has over 4 years of experience in radiotherapy, chemotherapy, and caring for cancer patients. He is currently working as a radiation oncologist at Portsudan Oncology Center in Portsudan, Sudan, a position he has held since March 2018. Previously, he worked as a radiation oncologist at the Radiation and Isotope Center in Khartoum, Sudan from March 2016 to March 2018. He received his fellowship training in radiation oncology from the Egyptian Fellowship Board of Radiation Oncology in Cairo, Egypt from July 2010 to December 2016 and holds a Bachelor of Medicine and Surgery degree
This document provides technical specifications for radiotherapy equipment used in cancer treatment. It covers specifications for external beam radiotherapy equipment like linear accelerators and cobalt-60 units, as well as brachytherapy equipment like high-dose rate afterloaders. The document is intended to help procurement of appropriate equipment and establishment of safe and effective radiotherapy services that meet quality standards. Technical requirements are provided for individual pieces of equipment as well as considerations for project management, maintenance, quality assurance, and training when setting up a new radiotherapy facility. Emerging technologies in radiotherapy are also briefly discussed.
This document provides a summary of the key elements of a specialty portfolio in radiation oncology, including:
1. An overview of the methodology, mission, vision, and authority governing the portfolio.
2. Details of the CanMEDS competencies and roles, as well as general core competencies required for radiation oncology training.
3. Guidelines on training structure, including levels, milestones, length of training, accredited centers, admission criteria, and regulation.
4. Components of the training program, including goals, opportunities, references, academic credits, evaluation, and maintenance of certification.
5. An outline of the clinical and basic science syllabus covered during training.
6.
1. Radiation therapy is the only curative treatment for non-metastatic recurrent nasopharyngeal cancer (rNPC). The addition of concurrently administered chemotherapy has been shown to significantly improve outcomes including overall survival for locally advanced cases.
2. Re-irradiation for rNPC provides a benefit, but carries risks of toxicity due to damage from previous radiation. Modern radiotherapy techniques like IMRT can help deliver a therapeutic dose while sparing nearby critical organs.
3. Doses over 60 Gy are typically used for re-irradiation of rNPC, though the optimal dose has not been established. Late effects depend on factors like recurrence site, prior treatment doses and volumes, time since initial radiation, and
1) Portsudan Oncology Center was established in 2015 to serve cancer patients in Red Sea state.
2) Breast cancer was the most common cancer type seen at the center, accounting for over 50% of cases in some years.
3) The center provides medical oncology services including chemotherapy, hormonal therapy, and targeted therapy, but is deficient in radiotherapy equipment.
This document provides information about breast cancer including what it is, risk factors, screening tools and recommendations, types of treatment, and myths. Some key points:
- Breast cancer is a malignant tumor that develops from breast tissues, usually the milk ducts or lobules.
- Risk factors include age, gender, family history, genetic factors, reproductive history, and lifestyle.
- Screening tools include breast self-exams, clinical exams, mammography, and ultrasound. Mammography is recommended annually starting at age 40.
- Early detection through screening can help prevent death and suffering by finding cancer early when it may be easier to treat.
This document discusses head and neck cancer, including:
- Squamous cell carcinomas make up 78% of head and neck cancers.
- Staging uses the TNM classification system to determine tumor size, nodal status, and metastasis.
- Treatment planning considers the patient's age, medical history, and potential complications.
- Primary treatments include surgery, radiation therapy, chemotherapy, or a combination.
- Acute complications of radiation therapy include mucositis, dysphagia, xerostomia, and trismus. Chronic complications include osteoradionecrosis and soft tissue necrosis.
This document discusses modern radiotherapy techniques including conformal radiotherapy and intensity-modulated radiation therapy (IMRT). It describes the planning steps which involve CT scanning of the patient, delineating the tumor and organ-at-risk volumes, dose analysis, and treatment delivery with quality assurance and patient positioning. IMRT allows for improved target conformality and reduced radiation exposure to surrounding healthy tissues compared to traditional radiotherapy through inverse planning optimization of multiple modulated radiation beams. Image-guided radiotherapy (IGRT) further improves treatment accuracy by accounting for organ motion and setup variations using frequent imaging.
Beam modification techniques include blocks, wedges, and compensators to modify the spatial distribution of radiation. Shielding blocks are commonly made of lead and are used to shield organs at risk. Wedge filters cause a progressive decrease in beam intensity to tilt isodose lines and provide a dose boost. Compensators are customized materials that account for tissue irregularities and ensure uniform dose distribution within the target. Flattening filters reduce the central exposure rate relative to the beam edges to produce a uniform beam density.
The uterus is a pear-shaped organ divided into the fundus, body, and cervix. Lymph drainage from the fundus goes to para-aortic nodes at L1, while the body and cervix drain to internal and external iliac nodes. Endometrial cancer is the most common gynecologic malignancy in the US, with risk factors including age, estrogen exposure, genetics, and medical history. Treatment depends on staging and includes surgery, radiation, chemotherapy, and hormonal therapy.
This document provides information about cervical cancer, including:
1. The anatomy of the cervix and epidemiology and risk factors for cervical cancer. Squamous cell carcinoma makes up 80% of cases.
2. The pathology, lymph node spread, diagnosis, staging according to FIGO, and prognostic factors like tumor size and lymph node involvement.
3. The treatment approaches for different stages, including surgery, radiation therapy alone or with chemotherapy. Concurrent chemotherapy with radiation improves outcomes for stages 1B2 or higher.
4. Details on radiation therapy techniques including target volume delineation and field arrangements tailored to the tumor extent and lymph node areas. Intensity-modulated radiation therapy can better spare normal
The document discusses prostate cancer including its anatomy, epidemiology, diagnosis, staging, treatment and outcomes. Key points include:
- Prostate cancer is the most commonly diagnosed cancer in men. Risk factors include age, family history, and ethnicity. Screening includes PSA testing and biopsy.
- Treatment depends on risk classification based on PSA, Gleason score, and stage. Options include active surveillance, surgery, radiation therapy and hormone therapy.
- Studies show dose escalation radiation therapy and use of IMRT/3D conformal radiation improve biochemical control rates with acceptable toxicity compared to conventional radiation. Adjuvant hormone therapy with radiation improves outcomes for intermediate-high risk disease.
Bladder cancer most commonly presents as hematuria and is usually transitional cell carcinoma. Risk factors include smoking, industrial chemical exposure, and past pelvic radiation. Diagnosis involves cystoscopy and biopsy. Staging uses TNM system and determines prognosis and treatment. Treatment depends on stage and includes transurethral resection for superficial disease or radical cystectomy for invasive disease, with chemotherapy sometimes used as well. Prognosis depends on stage, with 5-year survival rates ranging from 85% for stage Ta to 10-20% for stage IV disease.
This document summarizes cancer of the larynx, including its risk factors, diagnosis, staging, and treatment options. It describes the anatomy of the larynx and discusses how cancer can spread locally or to lymph nodes. Treatment depends on the stage and location of the cancer, and may include radiation therapy or surgery like laryngectomy. For early stage cancers, radiation is usually the preferred initial treatment to preserve the larynx and voice. More advanced cancers may be treated with chemoradiation to try to avoid laryngectomy when possible.
Local Advanced Lung Cancer: Artificial Intelligence, Synergetics, Complex Sys...Oleg Kshivets
Overall life span (LS) was 1671.7±1721.6 days and cumulative 5YS reached 62.4%, 10 years – 50.4%, 20 years – 44.6%. 94 LCP lived more than 5 years without cancer (LS=2958.6±1723.6 days), 22 – more than 10 years (LS=5571±1841.8 days). 67 LCP died because of LC (LS=471.9±344 days). AT significantly improved 5YS (68% vs. 53.7%) (P=0.028 by log-rank test). Cox modeling displayed that 5YS of LCP significantly depended on: N0-N12, T3-4, blood cell circuit, cell ratio factors (ratio between cancer cells-CC and blood cells subpopulations), LC cell dynamics, recalcification time, heparin tolerance, prothrombin index, protein, AT, procedure type (P=0.000-0.031). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and N0-12 (rank=1), thrombocytes/CC (rank=2), segmented neutrophils/CC (3), eosinophils/CC (4), erythrocytes/CC (5), healthy cells/CC (6), lymphocytes/CC (7), stick neutrophils/CC (8), leucocytes/CC (9), monocytes/CC (10). Correct prediction of 5YS was 100% by neural networks computing (error=0.000; area under ROC curve=1.0).
Integrating Ayurveda into Parkinson’s Management: A Holistic ApproachAyurveda ForAll
Explore the benefits of combining Ayurveda with conventional Parkinson's treatments. Learn how a holistic approach can manage symptoms, enhance well-being, and balance body energies. Discover the steps to safely integrate Ayurvedic practices into your Parkinson’s care plan, including expert guidance on diet, herbal remedies, and lifestyle modifications.
These lecture slides, by Dr Sidra Arshad, offer a quick overview of the physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar lead (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
6. Describe the flow of current around the heart during the cardiac cycle
7. Discuss the placement and polarity of the leads of electrocardiograph
8. Describe the normal electrocardiograms recorded from the limb leads and explain the physiological basis of the different records that are obtained
9. Define mean electrical vector (axis) of the heart and give the normal range
10. Define the mean QRS vector
11. Describe the axes of leads (hexagonal reference system)
12. Comprehend the vectorial analysis of the normal ECG
13. Determine the mean electrical axis of the ventricular QRS and appreciate the mean axis deviation
14. Explain the concepts of current of injury, J point, and their significance
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. Chapter 3, Cardiology Explained, https://www.ncbi.nlm.nih.gov/books/NBK2214/
7. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
TEST BANK For Basic and Clinical Pharmacology, 14th Edition by Bertram G. Kat...rightmanforbloodline
TEST BANK For Basic and Clinical Pharmacology, 14th Edition by Bertram G. Katzung, Verified Chapters 1 - 66, Complete Newest Version.
TEST BANK For Basic and Clinical Pharmacology, 14th Edition by Bertram G. Katzung, Verified Chapters 1 - 66, Complete Newest Version.
TEST BANK For Basic and Clinical Pharmacology, 14th Edition by Bertram G. Katzung, Verified Chapters 1 - 66, Complete Newest Version.
TEST BANK For Basic and Clinical Pharmacology, 14th Edition by Bertram G. Katzung, Verified Chapters 1 - 66, Complete Newest Version.
share - Lions, tigers, AI and health misinformation, oh my!.pptxTina Purnat
• Pitfalls and pivots needed to use AI effectively in public health
• Evidence-based strategies to address health misinformation effectively
• Building trust with communities online and offline
• Equipping health professionals to address questions, concerns and health misinformation
• Assessing risk and mitigating harm from adverse health narratives in communities, health workforce and health system
- Video recording of this lecture in English language: https://youtu.be/kqbnxVAZs-0
- Video recording of this lecture in Arabic language: https://youtu.be/SINlygW1Mpc
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
Basavarajeeyam is a Sreshta Sangraha grantha (Compiled book ), written by Neelkanta kotturu Basavaraja Virachita. It contains 25 Prakaranas, First 24 Chapters related to Rogas& 25th to Rasadravyas.
Histololgy of Female Reproductive System.pptxAyeshaZaid1
Dive into an in-depth exploration of the histological structure of female reproductive system with this comprehensive lecture. Presented by Dr. Ayesha Irfan, Assistant Professor of Anatomy, this presentation covers the Gross anatomy and functional histology of the female reproductive organs. Ideal for students, educators, and anyone interested in medical science, this lecture provides clear explanations, detailed diagrams, and valuable insights into female reproductive system. Enhance your knowledge and understanding of this essential aspect of human biology.
2. Objectives
To understand the mathematical bases behind survival
curves
Know the linear quadratic model formulation
Understand how the isoeffect curves for fractionated
radiation vary with tissue and how to use the LQ model to
change dose with dose per fraction
Understand the 4Rs of radiobiology as they relate to
clinical fractionated regimens and the sources of
heterogeneity that impact the concept of equal effect
per fraction
Know the major clinical trials on altered fractionation and
their outcome
Recognize the importance of dose heterogeneity in
modern treatment planning
3. Cells killing theories
• Target Theory:-
Target theory explains the cell damage caused by
radiation based on the principles of probability. It
assumes that there are certain critical molecules or
critical targets within cells that need to be hit or
inactivated by the radiation to kill the cell.
4. Single target–single hit
For viruses and bacteria
Multiple target–single hit
there is more than one target per cell, and a single hit of any of these
targets is required for cell death.Not all targets are hit; some of them are
killed, while others are damaged by low
doses. This type of damage is called sublethal damage (SLD) for
mammlain cells
5. Cell Survival Curves
The number of cells in cell lines within cell cultures can
increase in one of two ways:
• either arithmetically
• or exponentially (geometrically).
7. When cell culture exposed to radiation P:-
die
reproductive cell death
Divide and form small colonies
form colonies over longer periods
,The remaining cells are not affected by the radiation called surviving
fraction
8. Surviving Fraction:-
The ratio of the number of cells that form
colonies to the number of seed cells under
normal conditions (i.e., no irradiation) in a
cell culture is termed the plating efficiency
(PE). The same ratio obtained under
irradiated conditions and divided by the
PE is called the surviving fraction (SF):
9. Surviving fraction (SF) =
Colony number rad /Seeded cell number rad × PE
e.g 100 cells are seeded … 10 colonies formed
PE = 100/10 =10>>….. IF 450 CGY IS given and 5 colonies
ware formed
then SF =5/[100 × 10/100] = 1/2.
as a cell–dose plot. If the SF is calculated for various doses,
then it can be presented
Combining the points on the plot leads to a cell survival
curve.
10. LD50 value can be obtained from a
sigmoid survival curve (LD50 is the
dose that kills
50% of cells → lethal dose).
0 200 400 600
1
1
0.8
0.6
800
0.4
0.2
0 200 400 600 800
1.0
0.1
0.01
Survival curves are radiobiologically
defined using semilogarithmic
curves, and these
curves provide information on some
parameters such as the number of
cells killed by
the radiation and cell radiosensitivit
11. Exponential Survival Curves :-
These are the survival curves resulting from the single
target–single hit hypothesis of target
theory
0.37
D0
Single target single hit
12. After 100 radiation “hits,” the probability that one of the
hits will be a target→ e−1 (e » 2.718 …).
e−1 is approximately 37%. In other words, 63% of the
targets will be hit after 100 hits, while 37% of the targets will
D0 = dose that decreases the surviving fraction to 37%.
This is the dose required to induce an average damage
per cell.
A D0 dose always kills 63% of the cells in the region in
which it is applied, while 37%
of the cells will survive.
1/D0 = the slope of the survival curve.
13. If n increases → Dq increases → a wide shouldered curve is
observed.
If n decreases → Dq decreases → a narrow shouldered curve is
observed.
If Dq is wide and D0 is narrow, the cell is radioresistant.
The D0 and Dq values for the tumor should be smaller than
those of normal tissue to
achieve clinical success.
14.
15.
16. As the value of D0 decreases → 1/D0 increases → slope
increases → radiosensitive cell.
As the value of D0 increases → 1/D0 decreases → slope
decreases → radioresistant cell
17. Shouldered Survival Curves with Zero Initial Slope :-
These survival curves are based on the multiple
target–single hit hypothesis of target theory
18.
19. D0: the dose that yields a surviving fraction of 37%.
Dq: half-threshold dose → the region of the survival
curve where the shoulder starts
(indicates where the cells start to die exponentially) (=
quasi-threshold dose).
n: extrapolation number (the number of D0 doses
that must be given before all of the
cells have been killed).
20.
21. 1/D1: the slope of the component corresponding to multiple
target–single hit (the slope
of the initial region).
Dq: the dose at which the shoulder starts for the multiple
target–single hit component
(the quasi-threshold dose).
1/D0: the slope of the terminal region of the multiple target–
single hit component.
n: extrapolation number.
22. Components of Shouldered Survival Curves with Nonzero
Initial Slope :-
• Component corresponding to the single target–single hit model (blue in the
figure)
This shows lethal damage.
This shows the cells killed by the direct effect of the radiation.
This shows the effect of high-LET radiation.
• Component corresponding to the multiple target–single hit model (red in the
figure)
This shows the accumulation of SLD.
This shows the cells killed by the indirect effect of the radiation
23. Linear–Quadratic Model (LQ
Model)
In this model, developed by Douglas and Fowler in
1972, it was assumed that cell death due to ionizing
radiation has two components
The first component Directly proportional to dose → D
Linear component
The second component Directly proportional to the
square of the dose → D2 Quadratic component
24. a → shows the intrinsic cell radiosensitivity, and it is the
natural logarithm (loge) of the proportion of cells that
die or will die due to their inability to repair radiation-
induced damage per Gy of ionizing radiation.
b → reflects cell repair mechanisms, and it is the
natural logarithm of the proportion of repairable cells
due to their ability to repair the radiation-induced
damage per Gy of
ionizing radiation.
25. • p1 = aD.a → initial slope of the survival curve (low-
dose region) → linear coefficient.
• If the effect of two radiation hits is p2, then
p2 = bD2
b → quadratic coefficient.
Total effect p1 + p2 = ad + bd2
26. S.F. = e-aD
Single lethal hits
S.F. = e-(aD+bD2)
Single lethal hits plus
accumulated damage
• Cell kill is the result of single lethal
hits plus accumulated damage
from 2 independent sublethal
events
• The generalized formula is E = aD + bD2
• For a fractionated regimen E= nd(a + bd) =
D (a + bd) Where d = dose per fraction and
D = total dose
• a/b is dose at which death due to single
lethal lesions = death due to accumulation
of sublethal lesions i.e. aD = bD2 and D = a/b
in Gy
S.F.
1.0
0.1
0.01
0.001
DOSE Gy
a/b in Gy
aD
bD2
Linear Quadratic Model
28. What total dose (D) to give if the
dose/fx (d) is changed
• New old
Dnew (dnew + a/b) = Dold (dold +a/b)
So, for late responding tissue, what total dose in 1.5Gy
fractions is equivalent to 66Gy in 2Gy fractions?
Dnew (1.5+2) = 66 (2 + 2)
Dnew = 75.4Gy
NB:-Small differences in a/b for late responding tissues can
make a big difference in estimated D!
29. Biologically Effective Dose (BED)
Biologically Effective
Dose Total dose
Relative
Effectiveness
S.F. = e-E = e-(aD+bD2)
E = nd(a + bd)
E/a = nd(1+d/a/b)
35 x 2Gy = B.E.D.of 84Gy10 and 117Gy3
NOTE: 3 x 15Gy = B.E.D.of 113Gy10 and 270Gy3
Normalized total dose2Gy
= BED/RE
= BED/1.2 for a/b of 10Gy
= BED/1.67 for a/bof 3Gy
Equivalent to 162 Gy in 2Gy Fx -unrealistic!
(Fowler et al IJROBP 60: 1241, 2004)
31. 4Rs OF DOSE FRACTIONATION
These are radiobiological mechanisms that impact the
response to a fractionated course of radiation therapy
• Repair of sublethal damage
o spares late responding normal tissue preferentially
• Redistribution of cells in the cell cycle
o increases acute and tumor damage, no effect on late responding
normal tissue
• Repopulation
o spares acute responding normal tissue, no effect on late effects,
o danger of tumor repopulation
• Reoxygenation
o increases tumor damage, no effect in normal tissues
32. Regeneration assumed to be exponential
• S.F.regeneration = eT = e (ln2/Tp)T
o Where T = overall treatment time; Tp =
effective doubling time
• i.e. S.F. = e-(aD+bD2)+ln2/Tp(T-Tk)
o Where Tk is time of start of regeneration
33. Repair
• Repair” between fractions should be complete - N.B.
we are dealing with tissue recovery rather than DNA
repair
• CHART analysis HNC showed that late morbidity was less than
would be expected assuming complete recovery between
fractions
o Is the T1/2 for recovery for late responding normal tissues
2.5-4.5hrs?
34. Regeneration
• The lag time to regeneration varies with the tissue
• In acute responding tissues,
o Regeneration has a considerable sparing effect
• In human mucosa, regeneration starts 10-12 days into a 2Gy
Fx protocol and increases tissue tolerance by at least 1Gy/dy
o Prolonging treatment time has a sparing effect
o As treatment time is reduced, acute responding tissues become
dose-limiting
• In late responding tissues,
o Prolonging overall treatment time beyond 6wks has little effect,
but
prolonging time to retreatment may increase tissue tolerance
37. Multifraction Effects cell types
• The slope of an isoeffect curve changes with size of dose per
fraction depending on tissue type
• Acute responding tissues have flatter curves than do late
responding tissues
• a/b measures the sensitivity of tumor or tissue to fractionation
i.e. it predicts how total dose for a given effect will change
when you change the size of dose fraction
38.
39. Response to Fractionation Varies With Tissue
16
12
8
4
0
0
.01
.1
1
Dose (Gy)
S.F.
Late Responding
Tissues - a/b= 2Gy
Acute Responding
Tissues a/b= 10Gy
a/b is high (>6Gy) when survival
curve is almost exponential and
low (1-4Gy) when shoulder is wide
20
16
12
8
4
0
0
.01
.1
1
Dose (Gy)
S.F.
Single Dose
Late Effects
a/b= 2Gy
Single Dose
Acute Effects
a/b= 10Gy
Fractionated
Late Effects
Fractionated
Acute Effects
Fractionation spares late responding tissues
41. What are a/b ratios for human cancers?
In fact, for some tumors e.g. prostate, breast, melanoma,
soft tissue sarcoma, and liposarcoma a/b ratios may be
moderately low
Prostate
o Brenner and Hall IJROBP 43:1095, 1999
• comparing implants with EBRT
• a/b ratio is 1.5 Gy [0.8, 2.2]
o Lukka JCO 23: 6132, 2005
• Phase III NCIC 66Gy 33F in 45days vs 52.5Gy 20F in 28 days
• Compatible with a/b ratio of 1.12Gy (-3.3-5.6)
Breast
• UK START Trial
o 50Gy in 25Fx c.w. 39Gy in 13Fx; or 41.6Gy in 13Fx [or 40Gy in 15Fx (3 wks)]
• Breast Cancer a/b = 4.0Gy (1.0-7.8)
• Breast appearance a/b = 3.6Gy; induration a/b = 3.1Gy
• If fractionation sensitivity of a cancer is similar to dose-limiting healthy
tissues, it may be possible to give fewer, larger fractions without
compromising effectiveness or safety
43. Other Sources of
Heterogeneity
• Biological Dose
o Cell cycle
o Hypoxia/reoxygenation
o Clonogenic “stem cells” (G.F.)
• Number
• Intrinsic radiosensitivity
• Proliferative potential
• Differentiation status
• Physical Dose
o Need to know more about the importance of dose-volume
constraints
Dose
oxic
hypoxic
S.F
48. Hypofractionation
Tumor has low a/b ratio and there is
no therapeutic advantage to be gained
with respect to late complications
Reduced total number
of fractions (N)
Dose per fraction (d)
higher than 2.2 Gy
49. Conventional
70 Gy - 35 fx - 7 wks
Very accelerated
with reduction of dose
54 Gy - 36 fx - 12 days
Moderately accelerated
72 Gy - 42 fx - 6 wks
Hyperfractionated
81.6 Gy - 68 fx - 7 wks
53. EORTC hyperfractionation trial in
oropharynx cancer (N = 356)
Years
LOCAL CONTROL SURVIVAL
Years
Horiot 1992
80.5 Gy - 70 fx - 7 wks control: 70 Gy - 35-40 fx - 7-8 wks
p = 0.02
p = 0.08
54. CHART (N = 918)
• 54 Gy - 36 fx - 12 days control: 66 Gy - 33
fx - 6.5 wks
56. RTOG 90-03, Phase III comparison of fractionation
schedules in Stage III and IV SCC of oral cavity,
oropharynx, larynx, hypopharynx (N = 1113)
Conventional
Accelerated with split
70 Gy - 35 fx - 7 wks
67.2 Gy - 42 fx - 6 weeks (including 2-week split)
72 Gy - 42 fx - 6 wks
Hyperfractionated
81.6 Gy - 68 fx - 7 wks
Accelerated with
Concomitant boost
Fu 2000
60. Acute effects in accelerated or
hyperfractionated RT
Author Regimen Grade 3-4 mucositis
Cont Exp
• Horiot (n=356) HF 49% 67%
• Horiot (n=512) Acc fx + split 50% 67%
• Dische (n=918) CHART 43% 73%
• Fu (n=536) Acc fx(CB) 25% 46%
• Fu (n=542) Acc fx + split 25% 41%
• Fu (n=507) HF 25% 42%
• Skladowski (n=99) Acc fx 26% 56%
61. Conclusions for HNSCC
• Hyperfractionation increases TCP and protects late
responding tissues
• Accelerated treatment increase TCP but also increases acute
toxicity
• What should be considered standard for patients treated with
radiation only?
– Hyperfractionated radiotherapy
– Concomitant boost accelerated radiotherapy
• Fractions of 1.8 Gy once daily when given alone, cannot be
considered as an acceptable standard of care
• TCP curves for SSC are frustratingly shallow … selection of
tumors?
62. Hypofractionation
• Delivery of large dose in few fractions well known in
• SBRT and SABT in NSCLC but also in prostate and
breast in which ∞/β ratio is low even lower than
• Late tissues complication so high conformal dose
requirement to save normal tissues
63. Other Major Considerations
• Not all tumors will respond to hyper or accelerated
fractionation like HNSCC, especially if they have a low
a/bratio.
• High single doses or a small number of high dose per
fractions, as are commonly used in SBRT or SRS generally
aim at tissue ablation. Extrapolating based on a linear
quadratic equation to total dose is fraught with danger.
• Addition of chemotherapy or biological therapies to RT
always requires caution and preferably thoughtful pre-
consideration!!!
• Don’t be scared to get away from the homogeneous
field concept, but plan it if you intend to do so.