Ssd calculations
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This document discusses SSD calculations for radiation therapy treatment planning. It provides examples of calculating monitor units (MUs) needed to deliver a prescribed dose to different depths using various field sizes and source-to-surface distances (SSDs), accounting for factors like percent depth dose (PDD), inverse square, scatter, and blocking. It also gives an example of calculating the dose to the depth of maximum dose (dmax) given a prescribed dose to another depth using the ratio of PDD values.
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Sad calculations
The document discusses the calculation of monitor units (MU) for radiation therapy treatment plans using the standard equation of prescribed dose multiplied by various correction factors. It provides examples of calculating MUs for different treatment scenarios, including different depths, field sizes, source-to-axis distances (SAD), and weighted beam arrangements. The key factors involved are reference dose rate, inverse square correction, collimator scatter, phantom scatter, tissue maximum ratio (TMR), and other applicable corrections.
Dosimetric calculations
This document provides information on dosimetric calculations for radiation therapy. It discusses key concepts like percent depth dose (PDD) and tissue maximum ratio (TMR) which are used to calculate dose for non-isocentric and isocentric setups, respectively. Factors like collimator scatter, phantom scatter, and beam modifiers are also covered. The document outlines the basic principles and provides examples of SSD and SAD calculations.
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The document provides details about the acceptance testing and commissioning of a new TrueBeam linear accelerator installed at the facility. Some key details include:
- The machine was installed in an existing bunker previously occupied by a Siemens Primus Plus with additional shielding added.
- Acceptance testing verifies a small subset of beam data based on manufacturer guidelines to check specifications, while commissioning involves comprehensive beam measurements and treatment planning system configuration.
- Beam data measurements included depth doses, profiles, output, symmetry, flatness, and other dosimetric parameters which were analyzed and entered into the treatment planning system.
- Electron and photon beam energies and characteristics were evaluated to ensure they met tolerance limits. Other
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1. The document discusses commissioning parameters for flattening filter free (FFF) photon beams from a linear accelerator, including profile normalization methods, dosimetric field size, penumbra, and slope.
2. Profile normalization can be done using the inflection point or renormalization value to compare FFF and flattened beams. Dosimetric field size is measured as the 50% dose width. Penumbra is defined as the 20-80% distance for FFF beams after normalization.
3. Slope describes the peak shape of FFF profiles, and flatness/unflatness parameters are discussed to characterize beam homogeneity for both FFF and flattened beams.
Isodose lines
Isodose lines represent points of equal absorbed radiation dose on a dose distribution map. They are depicted as curves on isodose charts showing the volumetric and planar variations in absorbed dose. Factors influencing isodose curves include beam quality, field size, source-to-skin distance, beam modifiers like wedges or bolus, and depth. Isodose curves are used in radiation therapy treatment planning to evaluate dose distributions and ensure tumor coverage while sparing surrounding healthy tissues. They provide critical information about the radiation dose profile essential for safe and effective treatment.
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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.
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.
Sealed radionuclides
Sealed radioactive sources are radioactive material permanently sealed in a capsule. Common sealed sources used in brachytherapy include cesium-137, iridium-192, cobalt-60, iodine-125, gold-198, and radium-226. Each isotope has different properties such as half-life, photon energy emitted, and exposure rate constant. Sources are constructed of radioactive material encapsulated in stainless steel, gold or platinum capsules to prevent leakage and are available in various geometries like seeds, ribbons, or tubes to suit different clinical applications in brachytherapy.
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Sad calculations
The document discusses the calculation of monitor units (MU) for radiation therapy treatment plans using the standard equation of prescribed dose multiplied by various correction factors. It provides examples of calculating MUs for different treatment scenarios, including different depths, field sizes, source-to-axis distances (SAD), and weighted beam arrangements. The key factors involved are reference dose rate, inverse square correction, collimator scatter, phantom scatter, tissue maximum ratio (TMR), and other applicable corrections.
Dosimetric calculations
This document provides information on dosimetric calculations for radiation therapy. It discusses key concepts like percent depth dose (PDD) and tissue maximum ratio (TMR) which are used to calculate dose for non-isocentric and isocentric setups, respectively. Factors like collimator scatter, phantom scatter, and beam modifiers are also covered. The document outlines the basic principles and provides examples of SSD and SAD calculations.
Commissioning of Truebeam LINAC
The document provides details about the acceptance testing and commissioning of a new TrueBeam linear accelerator installed at the facility. Some key details include:
- The machine was installed in an existing bunker previously occupied by a Siemens Primus Plus with additional shielding added.
- Acceptance testing verifies a small subset of beam data based on manufacturer guidelines to check specifications, while commissioning involves comprehensive beam measurements and treatment planning system configuration.
- Beam data measurements included depth doses, profiles, output, symmetry, flatness, and other dosimetric parameters which were analyzed and entered into the treatment planning system.
- Electron and photon beam energies and characteristics were evaluated to ensure they met tolerance limits. Other
Flattening filter Free
1. The document discusses commissioning parameters for flattening filter free (FFF) photon beams from a linear accelerator, including profile normalization methods, dosimetric field size, penumbra, and slope.
2. Profile normalization can be done using the inflection point or renormalization value to compare FFF and flattened beams. Dosimetric field size is measured as the 50% dose width. Penumbra is defined as the 20-80% distance for FFF beams after normalization.
3. Slope describes the peak shape of FFF profiles, and flatness/unflatness parameters are discussed to characterize beam homogeneity for both FFF and flattened beams.
Isodose lines
Isodose lines represent points of equal absorbed radiation dose on a dose distribution map. They are depicted as curves on isodose charts showing the volumetric and planar variations in absorbed dose. Factors influencing isodose curves include beam quality, field size, source-to-skin distance, beam modifiers like wedges or bolus, and depth. Isodose curves are used in radiation therapy treatment planning to evaluate dose distributions and ensure tumor coverage while sparing surrounding healthy tissues. They provide critical information about the radiation dose profile essential for safe and effective treatment.
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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.
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.
Sealed radionuclides
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Isodose curves depict absorbed dose distributions and variations in volume and planes. They join points of equal dose. Isodose charts show the variation in dose as a function of depth and transverse distance from the central beam axis. Factors like beam energy, field size, and distance affect isodose curve shape through penumbra and dose deposition. Multiple beams are often needed to adequately treat tumors while sparing surrounding tissues. Beam arrangements, weights, and modifiers must be optimized for each plan.
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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.
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Electron-beam therapy: is used to treat superficial tumors at a standard 100 cm source-to-surface distance (SSD). Characteristics of electron beams from an Elekta PreciseTM linear accelerator are presented at a nominal SSD of 100 cm. However, certain clinical situations require the use of an extended SSD. The effects of extended source-to-surface distance (SSD) on the electron beam dose profiles were evaluated for various electron beam energies 6, 8, 10,12 and 15 MeV and the accuracy of various output correction methods was analyzed on an Elekta PreciseTM linear accelerator using a radiation field analyzer (RFA). Effective SSDs was evaluated for field sizes ranging from 6×6, 10×10, 14×14 and 20×20 cm2 for various energies.
Aim of the work
1.Investigate the physical properties of electron beams
at different beam energies.
2.Evaluate the accuracy of dose calculated by
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1. Isodose curves represent the dose distribution from radiation beams and are lines connecting points of equal percentage depth dose. They are used to depict the volumetric and planar variations in absorbed dose.
2. The parameters that affect the shape of isodose curves include beam quality, source size, SSD, SDD, field size, and beam modifiers like wedges and flattening filters. Lower beam energy results in greater lateral scatter and more bulging curves.
3. Multiple radiation fields can be combined using appropriate beam weights, sizes, angles and modifiers to deliver a more uniform dose to the tumor while sparing surrounding tissues. Parameters like setup accuracy and plan practicality are also considered.
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Electron-beam therapy: is used to treat superficial tumors at a standard 100 cm source-to-surface distance (SSD). Characteristics of electron beams from an Elekta PreciseTM linear accelerator are presented at a nominal SSD of 100 cm. However, certain clinical situations require the use of an extended SSD. The effects of extended source-to-surface distance (SSD) on the electron beam dose profiles were evaluated for various electron beam energies 6, 8, 10,12 and 15 MeV and the accuracy of various output correction methods was analyzed on an Elekta PreciseTM linear accelerator using a radiation field analyzer (RFA). Effective SSDs was evaluated for field sizes ranging from 6×6, 10×10, 14×14 and 20×20 cm2 for various energies.
Aim of the work
1.Investigate the physical properties of electron beams
at different beam energies.
2.Evaluate the accuracy of dose calculated by
Treatment Planning System (TPS) and measured for
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Brachytherapy permanent seed implant
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Linear Accelerator Acceptance, Commissioning and Annual QA
This document summarizes the expectations and key learnings from a linear accelerator acceptance, commissioning, and annual QA training that occurred from September to November 2008. The training covered:
1. Fundamental concepts of linear accelerators, beam production, safety features, and the acceptance testing process.
2. Techniques for collecting beam data needed for commissioning, including measurements and data definitions.
3. Procedures for linear accelerator QA and other treatment machine QA on an annual basis.
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The document provides a brief history of radiation therapy and x-rays, including their discovery in the late 19th century, and developments in equipment over time. It discusses early radiation therapy methods like orthovoltage and kilovoltage treatments. It also summarizes linear accelerators and how they improved upon older cobalt-60 and betatron technology to allow higher energy photon beams for treating deeper tumors. Simulation equipment is covered, comparing conventional versus CT-based simulation and how various imaging modalities can aid treatment planning.
Hsc 340
Cancer is caused by abnormal cell growth and proliferation due to environmental, genetic, and infectious factors. Tumors are classified as benign or malignant, with malignant tumors able to metastasize and invade other tissues. Cancer is detected through screening exams, tests, and imaging and is staged based on tumor size, lymph node involvement, and metastasis. Treatment may include surgery, chemotherapy, radiation therapy, and immunotherapy. Cancer spreads primarily via the lymphatic system and bloodstream, with patterns varying by cancer type. A patient's prognosis depends on factors like grade, stage, and tumor characteristics.
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Ssd calculations
- 1. SSD Calculations • Patient surface at 100cm – (80cm for Co-60) – Usually a single beam – Most simple of all calculations – Most likely to be called upon to do 100 cm Dose to a point at depth Depth = d cm Source Patient Surface
- 2. The SSD Equation • MU Setting = Prescribed Dose . RDR x ISCF x Sc x Sp x (PDD/100) x Other Factors RDR = reference dose rate usually 1 cGy/MU (cGy/min for Co-60) ISCF = inverse square correction factor Sc = collimator scatter factor Sp = phantom scatter factor PDD = percent depth dose Other factors = trays, wedges, etc…
- 3. Case 1: 180 cGy to Dmax, 10x10 Open Field • MU Setting = Prescribed Dose . RDR x ISCF x Sc x Sp x (PDD/100) x Other Factors RDR = reference dose rate usually cGy/MU (cGy/min for Co-60) ISCF = inverse square correction factor Sc = collimator scatter factor Sp = phantom scatter factor PDD = percent depth dose Other factors = trays, wedges, etc… RDR = 1 cGy/MU ISCF = N/A = 1.000 Sc = 1.000 Sp = 1.000 PDD = 100% Other factors = N/A = 1.000 • MU Setting = 180 . 1 x 1.000 x 1.000 x 1.000 x (100/100) x 1.000 = 180 MU 100 cm Depth = dmax = 1.5 cm 10x10 Field Size
- 4. Case 2: 180 cGy to d = 5 cm, 10x10 Open Field • MU Setting = Prescribed Dose . RDR x ISCF x Sc x Sp x (PDD/100) x Other Factors RDR = reference dose rate usually cGy/MU (cGy/min for Co-60) ISCF = inverse square correction factor Sc = collimator scatter factor Sp = phantom scatter factor PDD = percent depth dose Other factors = trays, wedges, etc… RDR = 1 cGy/MU ISCF = N/A = 1.000 Sc = 1.000 Sp = 1.000 PDD = 87.1% Other factors = N/A = 1.000 • MU Setting = 180 . 1 x 1.000 x 1.000 x 1.000 x (87.1/100) x 1.000 = 207 MU 100 cm Depth = 5 cm 10x10 Field Size
- 5. Case 3: 180 cGy to d = 5 cm, 10x20 Open Field • MU Setting = Prescribed Dose . RDR x ISCF x Sc x Sp x (PDD/100) x Other Factors RDR = reference dose rate usually cGy/MU (cGy/min for Co-60) ISCF = inverse square correction factor Sc = collimator scatter factor Sp = phantom scatter factor PDD = percent depth dose Other factors = trays, wedges, etc… RDR = 1 cGy/MU ISCF = N/A = 1.000 Sc = 1.013 (Based Upon 13x13 equivalent square) Sp = 1.008 (Based Upon 13x13 equivalent square) PDD = 87.7% (Based Upon 13x13 equivalent square) Other factors = N/A = 1.000 • MU Setting = 180 . 1 x 1.000 x 1.013 x 1.008 x (87.7/100) x 1.000 = 201 MU 100 cm 10x20 Field Size Depth = 5 cm
- 6. Case 4: 180 cGy to d = 5 cm, 10x20, 20% blocked field • MU Setting = Prescribed Dose . RDR x ISCF x Sc x Sp x (PDD/100) x Other Factors RDR = reference dose rate usually cGy/MU (cGy/min for Co-60) ISCF = inverse square correction factor Sc = collimator scatter factor Sp = phantom scatter factor PDD = percent depth dose Other factors = trays, wedges, etc… RDR = 1 cGy/MU ISCF = N/A = 1.000 Sc = 1.013 (Based Upon 13x13 equivalent square) Sp = 1.005 (Based Upon 11.7x11.7 effective square) PDD = 87.4% (Based Upon 11.7x11.7 effective square) Other factors = 0.970 (a blocking tray transmission factor) • MU Setting = 180 . 1 x 1.000 x 1.013 x 1.005 x (87.4/100) x 0.970 = 208 MU 100 cm 10x20 Field Size Depth = 5 cm
- 7. Case 5: 180 cGy to d = 5 cm, 10x20, 20% blocked field, SSD = 110 cm* *Ignoring Mayneord Factor • MU Setting = Prescribed Dose . RDR x ISCF x Sc x Sp x (PDD/100) x Other Factors RDR = reference dose rate usually cGy/MU (cGy/min for Co-60) ISCF = inverse square correction factor Sc = collimator scatter factor Sp = phantom scatter factor PDD = percent depth dose Other factors = trays, wedges, etc… RDR = 1 cGy/MU ISCF = (101.52 /111.52 ) = 0.828 Sc = 1.007 (Based Upon 11.8x11.8 equivalent square) Sp = 1.005 (Based Upon 11.7x11.7 effective square) PDD = 87.4% (Based Upon 11.7x11.7 effective square) Other factors = 0.970 (a blocking tray transmission factor) • MU Setting = 180 . 1 x 0.828 x 1.007 x 1.005 x (87.4/100) x 0.970 = 253 MU 110 cm 10x20 Field Size on the patient Depth = 5 cm 9.1x18.2 Field Size on the machine
- 8. Case 6: 180 cGy to d = 5 cm, 10x20, 20% blocked field, SSD = 110 cm* *Including Mayneord Factor • MU Setting = Prescribed Dose . RDR x ISCF x Sc x Sp x (PDD/100) x Other Factors RDR = reference dose rate usually cGy/MU (cGy/min for Co-60) ISCF = inverse square correction factor Sc = collimator scatter factor Sp = phantom scatter factor PDD = percent depth dose Other factors = trays, wedges, etc… RDR = 1 cGy/MU ISCF = (101.52 /111.52 ) = 0.828 Sc = 1.007 (Based Upon 11.8x11.8 equivalent square) Sp = 1.005 (Based Upon 11.7x11.7 effective square) PDD = 87.4% x (1052 )/(101.52 ) x (111.52 )/(1152 ) = 87.9% Other factors = 0.970 (a blocking tray transmission factor) • MU Setting = 180 . 1 x 0.828 x 1.007 x 1.005 x (87.9/100) x 0.970 = 252 MU 110 cm 10x20 Field Size on the patient Depth = 5 cm 9.1x18.2 Field Size on the machine
- 9. Case 7: Rx 180 cGy to d = 5cm, what is the dose to dmax? In an SDD setup, the doses inside the patient are related by the ratio of PDDs. Dose Dmax = 180 cGy x PDD(dmax) / PDD(d=5) = 180 x 100 / 87.1 = 206.7 cGy 100 cm Depth = 5 cm 10x10 Field Size dmax
- 10. Mayneord Factor