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.
The document discusses a medical linear accelerator (LINAC). It begins with an overview and definition, explaining that a LINAC uses high-frequency electromagnetic waves to accelerate charged particles like electrons through a linear tube to produce x-rays for radiation therapy. The document then covers the history, generations, major components, and functioning of LINACs, describing how they have advanced from early bulky machines to today's computer-controlled systems that produce precise radiation beams for cancer treatment. Key components discussed include the electron gun, magnetron/klystron, waveguide system, bending magnet, and treatment head.
Radioisotopes such as cesium-137, iridium-192, and gold-198 have replaced radium in brachytherapy sources. Brachytherapy involves placing sealed radioactive sources close to or inside a tumor and can be delivered at low, medium, or high dose rates. Key factors in choosing radioisotopes include half-life, radiation output, specific activity, and photon energy. Proper selection of radioisotopes and dose rates optimizes treatment effectiveness while minimizing radiation exposure.
TISSUE PHANTOM RATIO - THE PHOTON BEAM QUALITY INDEXVictor Ekpo
TPR(20,10) is the recommended photon beam quality index by IAEA TRS-398 for megavoltage clinical photons generated by linear accelerators. This presentation goes through the basics of Tissue Phantom Ratio (TPR).
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.
The document discusses a medical linear accelerator (LINAC). It begins with an overview and definition, explaining that a LINAC uses high-frequency electromagnetic waves to accelerate charged particles like electrons through a linear tube to produce x-rays for radiation therapy. The document then covers the history, generations, major components, and functioning of LINACs, describing how they have advanced from early bulky machines to today's computer-controlled systems that produce precise radiation beams for cancer treatment. Key components discussed include the electron gun, magnetron/klystron, waveguide system, bending magnet, and treatment head.
Radioisotopes such as cesium-137, iridium-192, and gold-198 have replaced radium in brachytherapy sources. Brachytherapy involves placing sealed radioactive sources close to or inside a tumor and can be delivered at low, medium, or high dose rates. Key factors in choosing radioisotopes include half-life, radiation output, specific activity, and photon energy. Proper selection of radioisotopes and dose rates optimizes treatment effectiveness while minimizing radiation exposure.
TISSUE PHANTOM RATIO - THE PHOTON BEAM QUALITY INDEXVictor Ekpo
TPR(20,10) is the recommended photon beam quality index by IAEA TRS-398 for megavoltage clinical photons generated by linear accelerators. This presentation goes through the basics of Tissue Phantom Ratio (TPR).
Cobalt-60 is commonly used as a gamma ray source for teletherapy due to its suitable properties. A Co-60 unit contains a sealed radioactive Co-60 source that emits two gamma rays during decay. The source is moved between shielded and treatment positions using various mechanisms. Beam size and shape are controlled through collimation and additional devices can modify the beam. Precise patient and beam positioning is enabled through computer control and motorized components while shielding protects staff from radiation.
Dr. Puneet Seth is a radiation oncologist who has worked in several hospitals in India implementing new radiotherapy techniques like IMRT and IGRT using Varian linear accelerators. He is now at BSR Cancer Hospital in Bhilai, Chhattisgarh where he plans to install a new unique Varian linear accelerator by end of 2012/2013 that will enable techniques like RapidArc and IGRT to treat cancer patients in the region. The new setup will help improve treatment planning and delivery compared to the existing older cobalt unit through features like the Millennium MLC and integrated CT simulation.
1. A multileaf collimator (MLC) is a device used in radiation therapy to shape radiation beams by blocking parts of the beam with independently moving leaf structures made of a dense material like tungsten.
2. MLCs allow for more precise shaping of radiation beams than traditional collimators to minimize dose to healthy tissues and conform dose to the tumor shape. They enable intensity-modulated radiation therapy (IMRT) through dynamic movement of their leaves during treatment delivery.
3. MLC leaf positioning accuracy and transmission properties must be verified through quality assurance procedures to ensure proper dose delivery, such as measurements of leaf transmission, leaf position accuracy, and dosimetric leaf gaps.
This document discusses quality assurance parameters and test frequencies for medical linear accelerators. It outlines electrical, mechanical, and dosimetry QA parameters that are tested daily, weekly, monthly, and yearly. Daily tests check parameters that could affect patient positioning, radiation field definition, output constancy, and safety. Weekly tests add checks for beam congruence, flatness, and symmetry. Monthly tests expand to all mechanical and electrical components. Annual tests involve re-calibration and more stringent tolerance levels to establish new baseline values. Tests ensure spatial and dosimetric accuracy within clinically acceptable limits.
The document summarizes the key components of a Co-60 teletherapy unit. It describes the Co-60 source, which is sealed in stainless steel capsules. The source housing contains and positions the source, and shields it using lead when not in use. Beam collimation is performed using motorized jaws to shape the field size and orientation. The gantry rotates 360 degrees to deliver the beam from different angles. A control console and patient couch are also described. Beam-modifying devices like wedges and blocks are used to further shape the dose distribution.
X-rays and neutrons interact differently with biological material based on their ionizing ability. X-rays produce sparse ionization while neutrons produce more dense ionization. Linear energy transfer (LET) quantifies the energy deposited over track length and is used to compare radiation types. Higher LET radiation like alpha particles are more biologically effective due to producing denser ionization over shorter tracks. The relative biological effectiveness (RBE) of radiation depends on factors like dose, fractions, and biological system and is calculated as the ratio of doses needed for equal effect compared to a reference radiation like x-rays. RBE increases with increasing LET up to 100keV/μm then decreases with further increases in LET. Oxygen enhancement ratio (
This document discusses treatment machines used for external beam radiotherapy. It begins by describing the evolution of radiotherapy technology from X-ray tubes to modern linear accelerators (linacs). It then focuses on the key components of X-ray and gamma ray treatment units, including X-ray targets, spectra, and quality parameters as well as teletherapy machines containing radioactive cobalt-60 or cesium-137 sources. The document provides detailed information on the physics principles and design of external beam radiotherapy equipment.
This study investigated generating improved 3D treatment plans for telecoabalt machines without MLC by using locally available materials like universal shielding blocks. The study aimed to see if plans similar to IMRT could be created on telecoabalt to help poor patients who cannot afford linear accelerator treatment but need advanced techniques. Two case studies are presented where improved 3D plans were created for telecoabalt that provided dose coverage and sparing of normal tissues comparable to IMRT plans. The conclusion is that 3DCRT/IMRT type plans are feasible on telecoabalt with careful planning using field-in-field techniques and custom shielding blocks.
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.
Cobalt-60 is commonly used in teletherapy machines for radiation therapy. It decays via beta emission with a half-life of 5.26 years, emitting two high energy gamma rays. Cobalt-60 sources are typically solid cylinders encapsulated in steel and placed inside the head of a teletherapy machine. The machine head uses mechanisms like sliding drawers or rotating wheels to position the source to emit the therapeutic beam or retract it for safety. Proper housing and collimation are needed to shape the beam and minimize leakage radiation. Cobalt-60 provides advantages over other isotopes as a gamma source for radiation therapy.
This document discusses the commissioning and acceptance testing of a medical linear accelerator (LINAC). It covers regulatory requirements, installation, commissioning, and time planning for the LINAC and radiotherapy facility. It also discusses various technical reports and task group publications that provide guidelines for LINAC quality assurance, including beam data collection and commissioning. Key aspects of the commissioning process involve mechanical, radiation, dosimetry, and quality assurance checks of the LINAC. Proper time management is also required to complete the commissioning and acceptance testing.
Les rayons X sont une forme de rayonnement électromagnétique à haute fréquence constitué de photons dont l'énergie varie d'une centaine d'eV (électron-volt), à plusieurs MeV[1].
Ce rayonnement a été découvert en 1895 par le physicien allemand Wilhelm Röntgen, qui a reçu pour cela le premier prix Nobel de physique ; il lui donna le nom habituel de l'inconnue en mathématiques, X. Il est naturel (cosmologie, astronomie) ou artificiel (radiologie) et alors résulte du bombardement d'électrons sur une cible généralement en tungstène. La principale propriété des rayons X est de traverser la matière en étant partiellement absorbés en fonction de la densité de celle-ci et de l'énergie du rayonnement, ce qui permet d'avoir une information sur l'intérieur des objets qu'ils traversent.
Les rayons X sont une des modalités
Cyberknife is a robotic radiosurgery system that can treat tumors anywhere in the body with sub-millimeter accuracy. It contains a linear accelerator mounted on a robotic arm that moves in six degrees of freedom to accurately deliver radiation from numerous angles. Treatment is tracked in real-time using x-ray images and the robotic arm moves to correct for any tumor motion during treatment. Cyberknife allows for both single and multiple fraction stereotactic radiosurgery treatments without the need for invasive head frames.
Beam directed radiotherapy aims to deliver a homogenous tumor dose while minimizing radiation to normal tissues. It involves careful patient positioning, immobilization, tumor localization, field selection, dose calculations, and verification. Key steps include using positioning aids and molds to reproducibly position the patient, imaging such as CT to delineate the tumor volume, contouring to define external body outlines, and dose calculations and verification to ensure accurate delivery.
Brachytherapy involves placing radioactive sources inside or near a tumor to deliver radiation. It has advantages over external beam radiation in better targeting the tumor while sparing surrounding healthy tissue. The document discusses the history of brachytherapy and the types of sources, implants, and machines used. It also covers dosimetry systems for gynecological cancers like cervical cancer, which commonly uses intracavitary implants of radioactive sources in an applicator. Interstitial brachytherapy directly implants radioactive sources in the tumor. Remote afterloading machines allow safely implanting and removing radioactive sources.
The document discusses the key considerations and calculations involved in determining shielding thickness for radiotherapy facilities. It explains that the thickness depends on factors like workload, use factor, occupancy factor and permissible dose limits. It also describes calculating the thickness for primary barriers, which block direct radiation, and secondary barriers, which block scattered and leakage radiation. Precautions are discussed like allowing for field size and offsets to account for uncertainties.
Tomotherapy is a form of intensity-modulated radiation therapy (IMRT) that utilizes a radiation therapy device designed on a CT scanner-based platform. It delivers radiation via a fan beam using a ring gantry that rotates continuously around the patient. This allows for radiation to be delivered from all angles and precise tumor targeting while minimizing dose to surrounding healthy tissues. Daily MVCT imaging is used for image-guided radiation therapy (IGRT) to precisely locate tumors prior to each treatment for enhanced accuracy. Tomotherapy combines IMRT and IGRT capabilities into a single integrated platform.
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 seminar is presented as a part of weekly journal club and seminar regularly conducted at Apollo hospital,Kolkata Department of Radiation oncology.
- Cobalt compounds have been used to color glass and ceramics for millennia, dating back to ancient Egypt and China.
- Swedish chemist Georg Brandt discovered cobalt as a new element in 1735 and showed that cobalt compounds were responsible for the blue color in glass.
- Cobalt occurs naturally in combination with other elements like sulfur and arsenic in minerals, but is most often obtained as a byproduct of copper and nickel mining.
Cobalt-60 is commonly used as a gamma ray source for teletherapy due to its suitable properties. A Co-60 unit contains a sealed radioactive Co-60 source that emits two gamma rays during decay. The source is moved between shielded and treatment positions using various mechanisms. Beam size and shape are controlled through collimation and additional devices can modify the beam. Precise patient and beam positioning is enabled through computer control and motorized components while shielding protects staff from radiation.
Dr. Puneet Seth is a radiation oncologist who has worked in several hospitals in India implementing new radiotherapy techniques like IMRT and IGRT using Varian linear accelerators. He is now at BSR Cancer Hospital in Bhilai, Chhattisgarh where he plans to install a new unique Varian linear accelerator by end of 2012/2013 that will enable techniques like RapidArc and IGRT to treat cancer patients in the region. The new setup will help improve treatment planning and delivery compared to the existing older cobalt unit through features like the Millennium MLC and integrated CT simulation.
1. A multileaf collimator (MLC) is a device used in radiation therapy to shape radiation beams by blocking parts of the beam with independently moving leaf structures made of a dense material like tungsten.
2. MLCs allow for more precise shaping of radiation beams than traditional collimators to minimize dose to healthy tissues and conform dose to the tumor shape. They enable intensity-modulated radiation therapy (IMRT) through dynamic movement of their leaves during treatment delivery.
3. MLC leaf positioning accuracy and transmission properties must be verified through quality assurance procedures to ensure proper dose delivery, such as measurements of leaf transmission, leaf position accuracy, and dosimetric leaf gaps.
This document discusses quality assurance parameters and test frequencies for medical linear accelerators. It outlines electrical, mechanical, and dosimetry QA parameters that are tested daily, weekly, monthly, and yearly. Daily tests check parameters that could affect patient positioning, radiation field definition, output constancy, and safety. Weekly tests add checks for beam congruence, flatness, and symmetry. Monthly tests expand to all mechanical and electrical components. Annual tests involve re-calibration and more stringent tolerance levels to establish new baseline values. Tests ensure spatial and dosimetric accuracy within clinically acceptable limits.
The document summarizes the key components of a Co-60 teletherapy unit. It describes the Co-60 source, which is sealed in stainless steel capsules. The source housing contains and positions the source, and shields it using lead when not in use. Beam collimation is performed using motorized jaws to shape the field size and orientation. The gantry rotates 360 degrees to deliver the beam from different angles. A control console and patient couch are also described. Beam-modifying devices like wedges and blocks are used to further shape the dose distribution.
X-rays and neutrons interact differently with biological material based on their ionizing ability. X-rays produce sparse ionization while neutrons produce more dense ionization. Linear energy transfer (LET) quantifies the energy deposited over track length and is used to compare radiation types. Higher LET radiation like alpha particles are more biologically effective due to producing denser ionization over shorter tracks. The relative biological effectiveness (RBE) of radiation depends on factors like dose, fractions, and biological system and is calculated as the ratio of doses needed for equal effect compared to a reference radiation like x-rays. RBE increases with increasing LET up to 100keV/μm then decreases with further increases in LET. Oxygen enhancement ratio (
This document discusses treatment machines used for external beam radiotherapy. It begins by describing the evolution of radiotherapy technology from X-ray tubes to modern linear accelerators (linacs). It then focuses on the key components of X-ray and gamma ray treatment units, including X-ray targets, spectra, and quality parameters as well as teletherapy machines containing radioactive cobalt-60 or cesium-137 sources. The document provides detailed information on the physics principles and design of external beam radiotherapy equipment.
This study investigated generating improved 3D treatment plans for telecoabalt machines without MLC by using locally available materials like universal shielding blocks. The study aimed to see if plans similar to IMRT could be created on telecoabalt to help poor patients who cannot afford linear accelerator treatment but need advanced techniques. Two case studies are presented where improved 3D plans were created for telecoabalt that provided dose coverage and sparing of normal tissues comparable to IMRT plans. The conclusion is that 3DCRT/IMRT type plans are feasible on telecoabalt with careful planning using field-in-field techniques and custom shielding blocks.
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.
Cobalt-60 is commonly used in teletherapy machines for radiation therapy. It decays via beta emission with a half-life of 5.26 years, emitting two high energy gamma rays. Cobalt-60 sources are typically solid cylinders encapsulated in steel and placed inside the head of a teletherapy machine. The machine head uses mechanisms like sliding drawers or rotating wheels to position the source to emit the therapeutic beam or retract it for safety. Proper housing and collimation are needed to shape the beam and minimize leakage radiation. Cobalt-60 provides advantages over other isotopes as a gamma source for radiation therapy.
This document discusses the commissioning and acceptance testing of a medical linear accelerator (LINAC). It covers regulatory requirements, installation, commissioning, and time planning for the LINAC and radiotherapy facility. It also discusses various technical reports and task group publications that provide guidelines for LINAC quality assurance, including beam data collection and commissioning. Key aspects of the commissioning process involve mechanical, radiation, dosimetry, and quality assurance checks of the LINAC. Proper time management is also required to complete the commissioning and acceptance testing.
Les rayons X sont une forme de rayonnement électromagnétique à haute fréquence constitué de photons dont l'énergie varie d'une centaine d'eV (électron-volt), à plusieurs MeV[1].
Ce rayonnement a été découvert en 1895 par le physicien allemand Wilhelm Röntgen, qui a reçu pour cela le premier prix Nobel de physique ; il lui donna le nom habituel de l'inconnue en mathématiques, X. Il est naturel (cosmologie, astronomie) ou artificiel (radiologie) et alors résulte du bombardement d'électrons sur une cible généralement en tungstène. La principale propriété des rayons X est de traverser la matière en étant partiellement absorbés en fonction de la densité de celle-ci et de l'énergie du rayonnement, ce qui permet d'avoir une information sur l'intérieur des objets qu'ils traversent.
Les rayons X sont une des modalités
Cyberknife is a robotic radiosurgery system that can treat tumors anywhere in the body with sub-millimeter accuracy. It contains a linear accelerator mounted on a robotic arm that moves in six degrees of freedom to accurately deliver radiation from numerous angles. Treatment is tracked in real-time using x-ray images and the robotic arm moves to correct for any tumor motion during treatment. Cyberknife allows for both single and multiple fraction stereotactic radiosurgery treatments without the need for invasive head frames.
Beam directed radiotherapy aims to deliver a homogenous tumor dose while minimizing radiation to normal tissues. It involves careful patient positioning, immobilization, tumor localization, field selection, dose calculations, and verification. Key steps include using positioning aids and molds to reproducibly position the patient, imaging such as CT to delineate the tumor volume, contouring to define external body outlines, and dose calculations and verification to ensure accurate delivery.
Brachytherapy involves placing radioactive sources inside or near a tumor to deliver radiation. It has advantages over external beam radiation in better targeting the tumor while sparing surrounding healthy tissue. The document discusses the history of brachytherapy and the types of sources, implants, and machines used. It also covers dosimetry systems for gynecological cancers like cervical cancer, which commonly uses intracavitary implants of radioactive sources in an applicator. Interstitial brachytherapy directly implants radioactive sources in the tumor. Remote afterloading machines allow safely implanting and removing radioactive sources.
The document discusses the key considerations and calculations involved in determining shielding thickness for radiotherapy facilities. It explains that the thickness depends on factors like workload, use factor, occupancy factor and permissible dose limits. It also describes calculating the thickness for primary barriers, which block direct radiation, and secondary barriers, which block scattered and leakage radiation. Precautions are discussed like allowing for field size and offsets to account for uncertainties.
Tomotherapy is a form of intensity-modulated radiation therapy (IMRT) that utilizes a radiation therapy device designed on a CT scanner-based platform. It delivers radiation via a fan beam using a ring gantry that rotates continuously around the patient. This allows for radiation to be delivered from all angles and precise tumor targeting while minimizing dose to surrounding healthy tissues. Daily MVCT imaging is used for image-guided radiation therapy (IGRT) to precisely locate tumors prior to each treatment for enhanced accuracy. Tomotherapy combines IMRT and IGRT capabilities into a single integrated platform.
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 seminar is presented as a part of weekly journal club and seminar regularly conducted at Apollo hospital,Kolkata Department of Radiation oncology.
- Cobalt compounds have been used to color glass and ceramics for millennia, dating back to ancient Egypt and China.
- Swedish chemist Georg Brandt discovered cobalt as a new element in 1735 and showed that cobalt compounds were responsible for the blue color in glass.
- Cobalt occurs naturally in combination with other elements like sulfur and arsenic in minerals, but is most often obtained as a byproduct of copper and nickel mining.
The document discusses isotopic teletherapy machines, which use cobalt-60 or cesium-137 radioactive sources to produce gamma rays for external beam radiation therapy. It describes the components and operation of cobalt-60 teletherapy machines, including the radioactive cobalt-60 source, source housing, collimators, gantry, patient support assembly, and control console. Key factors in selecting radioisotopes are high gamma ray energy, long half-life, and ability to produce large quantities for clinical use.
brief but informative knowledge about what basically Cobalt 60 is and what is the phenomenon behind this machine ... easy to understand as well as presenting during lectures and in classes . share it
The document discusses cobalt-60 and its use in external beam radiation therapy. Cobalt-60 is a radioactive isotope that decays through beta decay, emitting two gamma rays with energies of 1.17 and 1.33 MeV. It is used as a sealed source in teletherapy units, where its gamma rays are aimed at cancerous tumors from multiple angles to destroy cancer cells. The main components of a cobalt-60 machine are the head containing the cobalt-60 source, a collimator to shape the beam, a gantry that rotates around the patient, and a patient support assembly. Cobalt-60 therapy has been used for almost 60 years to treat various cancers throughout the body due its precision and effectiveness.
cours pour le scanner ,bases physique ;HISTORIQUE . FORMATION DE L IMAGE . CONSTITUTION D'UN SCANOGRAPHE ;PARAMETRES D'ACQUISITION ET DE
RECONSTRUCTION ; QUALITE DE L IMAGE
SMC lance ses nouveaux ioniseurs IZS40/41/42 destiné à l'élimination de l'électricité statique lors de la construction ou l'emballage des produits.
3 types de modèles sont disponibles :
- ioniseur standard série IZS40 : seule l'activation ou la désactivation
de l'alimentation (ON/OFF) est nécessaire.
- ioniseur type avec capteur de retour : le capteur de retour permet une élimination rapide de l'électricité statique.
- ioniseur type à double CA série IZS42 : amplitude tension réduite.
2. La distribution spectrale, c’est-à-dire les proportions relatives des énergies
qui sont représentées dans le faisceau.
Un tube à rayons X émet simultanément, et indépendamment, un spectre continu et
un spectre de raies.
3. Qualité du faisceau
Exemple de couche de demi atténuation
(CDA)
pour des faisceaux d'ortho voltage.
Potentiel 60 80 100 120 250
nominal
(kVp)
CDA 2.24 3.28 0.24 0.50 1.86
(mm) (Al) (Al) (Cu) (Cu) (Cu)
4. Émetteurs de Rx de basses énergies
Appareil basse
énergie: 50 kV
Faisceau de RX est
émis dans la
direction opposée
du faisceau
d’électrons.
5. Applications Clinique en per-operatoire
Types de cancers
• Sein
• Colorectal
• Cerebrale
• Peau
• Sphere ORL
10
10. Contact-thérapie et Appareils de
Moyenne Énergie
Contact-thérapie Moyenne Énergie
– 10 à 150kVp – 150 à 400kVp
– Petites lésions cutanées – Lésions cutanées et
– Taille maximale de métastases osseuses
l’applicateur
généralement < 7cm – applicateurs ou
diaphragme
– DSP < 30cm
– Qualité du faisceau – DSP : 30 à 60cm
spécifiée en terme de – Qualité du faisceau est
CDA d’Aluminium (0.5 to spécifiée en CDA de
8mm) Cuivre (0.2 to 5mm)
11.
12. Appareils à Rayons X de Moyenne Énergie (150 - 400 kVp
Vue d’ensemble de l’appareil
Limité à la radiothérapie dermatologique:
Les rayons appliqués avec les tubes à rayons X avaient permis d’obtenir des guérissons
de tumeurs de la peau ou du sein mais toujours superficielles
13. 2 – Appareil de cobalthérapie
Il fallait trouver un moyen de pénétrer plus loin les tissus pour traiter
les tumeurs profondes
14. - Un nouveau progrès survint après la seconde guerre mondiale, avec l’introduction des
radioéléments artificiels, dont la découverte avait été faite en 1934 par Fréderic et Irène
Joliot-Curie
- La bombe au cobalt révolutionna des le début des années 1950 la radiothérapie
transcutanée
18. Appareil de Télécobalt :
Au Centre Anti Cancer de Blida 02 télécobalthérapie utilisés
pour la radiothérapie (traitement des tumeurs malignes par des
rayonnements ionisants), ce sont PHOENIX 29 et PHOENIX 30
fabriqués par L’Energie Atomique du Canada, limitée (A.E.C.L.).
Le Canada est le plus grand producteur de cobalt 60 (isotope
précieux) au monde.
La tête :
La tête d’un appareil de télécobalthérapie est une
enceinte dans laquelle se trouve la source radioactive, elle est
constituée d’un métal lourd, plomb ou tungstène et son
épaisseur doit être calculée pour arrêter le rayonnement qui est
émis dans toutes les directions ; un orifice permet le passage du
faisceau utile. L’émission du rayonnement est continue
l’interruption du faisceau est obtenue en déplaçant la source
par un dispositif (système à commande pneumatique),qui en
position de repos est située au centre de l’enceinte de plomb. La
source est montée dans un cylindre de plomb ; à l’autre
extrémité de ce cylindre est placée une lampe projetant un
faisceau lumineux simulant le faisceau d’irradiation la
translation de ce cylindre permet d’amener en face l’orifice soit
la source de Cobalt, soit la source lumineuse .
19. La source de Cobalt 60 est constituée par un empilement de grains de Cobalt 60, le
cylindre ainsi constitué a une base dont le diamètre mesure 2 cm (diamètre de la
source) et dont la hauteur est également voisine de 2 cm . Les photons du Cobalt 60,
dont l’énergie est de 1.17 et 1.33 MeV, mais compte tenu des interactions subies par
ces photons dans la source elle-même et dans le dispositif de collimation, l’énergie
moyenne du faisceau est estimée à 0.9 MeV.
Assemblage de la source : La source doit être scellée de façon a résister a des
températures élevées lors d’un éventuel incendie du bâtiment
La source est à l'intérieur d'une capsule d'acier inoxydable soudée afin de la rendre
étanche.
20. Schéma de la tête de l’appareil de télécobalt et mécanisme de
l’entraînement de source: Translation
21. Schéma de la tête de l’appareil de télécobalt et mécanisme de l’entraînement
de source: Rotation
