Nanotechnology enables routing information at the speed of light through photonic communication networks. Photonic band gaps and nano lasers are used to generate and amplify coherent light beams for optical switching and routing. Mirrors on the nano scale can be used as versatile routers by changing their orientation electrostatically to steer light and tightly regulate the angle. Applications include on-chip data communication, medical diagnostics, fusion energy, and laser defense. In conclusion, using nanotechnology tools like photonic band gaps, nano lasers and mirrors, information can be sent at the speed of light through photonic communication.
This document provides an overview of a quantum mechanics course taught by Martin Plenio at Imperial College in 2002. The course covers mathematical foundations of quantum mechanics, quantum measurements, dynamics and symmetries, and approximation methods. It is divided into two parts, with the first part covering core topics in quantum mechanics and the second part focusing on quantum information processing and related topics. The document provides chapter outlines and section headings for the material to be covered.
The document summarizes an academic presentation about an Nd:YAG laser.
1) Nd:YAG lasers were developed in 1964 by Bell Labs. They use neodymium-doped yttrium aluminium garnet as the lasing medium and are optically pumped, allowing them to produce high power outputs.
2) The active medium is yttrium aluminium garnet doped with 1% neodymium ions, which act as the active centers for lasing. The Nd:YAG rod is mounted inside an optical cavity formed by mirrors and is pumped using a xenon flash lamp.
This document contains lecture notes from a course on electromagnetic theory taught by Arpan Deyasi. It covers topics on magnetic scalar and vector potentials, including their definitions, properties, and applications to problems involving magnetic fields generated by currents. The notes provide the mathematical relationships between magnetic fields and potentials, and work through examples such as calculating the potentials for an infinite solenoid and current-carrying wire.
In this presentation on LED Basics we will look at a few topics in semiconductor lighting such as light generation from a semiconductor material, LED chip technology, structure of an LED, creating white light in an LED package and finally some definitions of CCT and CRI.
Fundamentals of modern physics, the de-Broglie hypothesisPraveen Vaidya
The presentation uploaded here educates about the failure of classical physics to explain Blackbody radiation and the success of quantum theory to explain the Blackbody radiation spectrum and other phenomena, the de-Broglie hypothesis and its significance, nature of de-broglie waves and the representation. Numerical problems are given at the end.
The Lycurgus Cup is a rare example of a dichroic Roman glass vessel from the 4th century AD. It appears green when light is reflected off its surface but red when light shines through it, due to minute amounts of gold and silver added to the glass. Modern analysis showed the dichroism is caused by microscopic gold and silver crystals in the glass that scatter light differently depending on the light source. The cup also has an ornate decoration depicting the legend of King Lycurgus.
Nanotechnology enables routing information at the speed of light through photonic communication networks. Photonic band gaps and nano lasers are used to generate and amplify coherent light beams for optical switching and routing. Mirrors on the nano scale can be used as versatile routers by changing their orientation electrostatically to steer light and tightly regulate the angle. Applications include on-chip data communication, medical diagnostics, fusion energy, and laser defense. In conclusion, using nanotechnology tools like photonic band gaps, nano lasers and mirrors, information can be sent at the speed of light through photonic communication.
This document provides an overview of a quantum mechanics course taught by Martin Plenio at Imperial College in 2002. The course covers mathematical foundations of quantum mechanics, quantum measurements, dynamics and symmetries, and approximation methods. It is divided into two parts, with the first part covering core topics in quantum mechanics and the second part focusing on quantum information processing and related topics. The document provides chapter outlines and section headings for the material to be covered.
The document summarizes an academic presentation about an Nd:YAG laser.
1) Nd:YAG lasers were developed in 1964 by Bell Labs. They use neodymium-doped yttrium aluminium garnet as the lasing medium and are optically pumped, allowing them to produce high power outputs.
2) The active medium is yttrium aluminium garnet doped with 1% neodymium ions, which act as the active centers for lasing. The Nd:YAG rod is mounted inside an optical cavity formed by mirrors and is pumped using a xenon flash lamp.
This document contains lecture notes from a course on electromagnetic theory taught by Arpan Deyasi. It covers topics on magnetic scalar and vector potentials, including their definitions, properties, and applications to problems involving magnetic fields generated by currents. The notes provide the mathematical relationships between magnetic fields and potentials, and work through examples such as calculating the potentials for an infinite solenoid and current-carrying wire.
In this presentation on LED Basics we will look at a few topics in semiconductor lighting such as light generation from a semiconductor material, LED chip technology, structure of an LED, creating white light in an LED package and finally some definitions of CCT and CRI.
Fundamentals of modern physics, the de-Broglie hypothesisPraveen Vaidya
The presentation uploaded here educates about the failure of classical physics to explain Blackbody radiation and the success of quantum theory to explain the Blackbody radiation spectrum and other phenomena, the de-Broglie hypothesis and its significance, nature of de-broglie waves and the representation. Numerical problems are given at the end.
The Lycurgus Cup is a rare example of a dichroic Roman glass vessel from the 4th century AD. It appears green when light is reflected off its surface but red when light shines through it, due to minute amounts of gold and silver added to the glass. Modern analysis showed the dichroism is caused by microscopic gold and silver crystals in the glass that scatter light differently depending on the light source. The cup also has an ornate decoration depicting the legend of King Lycurgus.
Coulomb blockade occurs when the electrostatic energy required to add a single electron to a microscopic conductor is greater than the thermal energy. This results in a gap in the conductor's energy levels and prevents electron tunneling below a threshold voltage that depends on temperature. A single electron transistor uses controlled electron tunneling between a source and drain electrode connected by a quantum dot or wire channel to amplify current. It operates by changing the quantum system's energy levels with a gate voltage to allow electrons to tunnel one by one. Mathematical modeling of the single electron transistor involves calculating tunneling rates and probabilities based on free energy changes from electron additions or removals.
This document describes an experiment to determine the numerical aperture of an optical fiber. It provides background information on numerical aperture and how it is defined as the light gathering ability of an optical fiber. It then describes the experimental procedure and equipment used, which involves connecting an optical fiber to a trainer board and measuring the diameter of the light spot emitted at different distances from the fiber end. The results are tabulated and show that the numerical aperture of the optical fiber tested is 0.4.
Introduction to nanoscience and nanotechnologyaimanmukhtar1
Introduction of nanoscience/nanotechnology ,properties/potential applications of nanomaterials and electrodeposition of metal single component and alloy nanowires in AAO template
This document discusses different types of phase retardation plates, including quarter-wave plates and half-wave plates. It begins by introducing how retarders change the polarization of light by causing a phase lag between the two polarization components. It then defines a phase retardation plate as a uniformly thick birefringent crystal plate that produces a definite phase difference between the ordinary and extraordinary rays. It provides details on how quarter-wave plates and half-wave plates produce specific phase differences of π/2 and π respectively. Applications of quarter-wave plates and half-wave plates including converting between linear and circular polarization and rotating the polarization plane are also summarized.
This document provides an overview of optical fiber communication. It discusses the history and development of optical fibers, including the discovery of total internal reflection and development of glass coatings to reduce signal loss. It describes the basic components of an optical communication system including light sources, fiber cables, and light detectors. It also covers fiber types, advantages like high bandwidth and low signal degradation, and disadvantages such as higher initial cost compared to copper cables.
This document provides an overview of optical fiber communication (OFC). It begins with the historical development and need for optical systems due to limitations of traditional communication methods. The basics of OFC are explained, including the system block diagram and principles of operation using ray theory and total internal reflection. Fiber types and transmission characteristics such as attenuation and bandwidth are covered. Finally, key optical components used in OFC systems such as fiber splices, connectors, and couplers are outlined.
Introduction of semiconductor oxides in photovoltaic devicesMuhammad Mudassir
This document discusses the incorporation of semiconductor oxides in photovoltaic devices. It explains that semiconductor oxides like ZnO, TiO2, and SnO2 can absorb solar energy due to their band gap. These metal oxide semiconductors can be used as n-type or p-type materials in organic solar cells depending on their conduction and valence bands. The document also discusses how ZnO and TiO2 can be used as photocatalysts in applications like wastewater treatment due to their photoinduced oxidation-reduction reactions when illuminated. Finally, it states that metal oxide semiconductors are useful in technologies involving photon-assisted processes like serving as scaffold layers in dye-sensitized solar cells and transport layers
Metamaterials are artificial structures designed to have unique electromagnetic properties not found in nature, such as a negative refractive index. They are composed of meta-atoms that can manipulate electromagnetic waves at scales smaller than the wavelength of light. Metamaterials have applications in invisibility cloaking, super lenses, compact antennas, absorbing electromagnetic radiation, and mitigating seismic waves. However, designing metamaterials for specific wavelengths is challenging, and they do not work perfectly and are very expensive.
Circularly polarized light consists of two perpendicular electromagnetic plane waves of equal amplitude with a 90 degree phase difference between them. The light illustrated is an example of right-circularly polarized light.
This document discusses CMOS image sensors. It begins by defining an image sensor as a device that converts an optical image into an electrical signal. It then explains the basic operation of CCD and CMOS image sensors, describing how each type works at a pixel level. The document concludes by comparing CCD and CMOS technologies, noting advantages of CMOS such as lower cost and power consumption, while CCD provides better image quality for some applications.
This document discusses quantum dots, which are semiconductors on the nanometer scale that obey the principle of quantum confinement. The energy band gap of quantum dots determines the wavelength of light they can absorb and emit, and this wavelength depends on the size of the dot. Solutions containing quantum dots of different sizes appear different colors because the particles absorb and emit light within the visible spectrum. Potential applications of quantum dots include improving solar cells, use in televisions, and medical imaging.
This document discusses the density of states (DoS) for bulk semiconductors. It begins by defining DoS as the number of available energy states per unit energy interval per unit dimension in real space. It then derives the DoS for bulk semiconductors using the Bloch theorem and shows that the DoS is proportional to the square root of energy. Finally, it defines the effective DoS, which accounts for occupancy based on the Fermi-Dirac distribution.
The document certifies that Mujammil Khan, a class 12 student, completed an independent project on photodiodes under the supervision of his physics teacher, Mrs. Kanika. Khan thanks his teacher, principal, parents, friends, and classmates for their guidance and support during the project. The project report includes sections on the history, theory, types, construction, characteristics, applications, and advantages/disadvantages of photodiodes.
X-Ray Photoelectron Spectroscopy (XPS) is a surface-sensitive technique that uses X-rays to eject electrons from the surface of a sample. An XPS instrument measures the kinetic energy of these ejected electrons to identify the elements present and the chemical and electronic states of the surface. XPS provides information only about the top 10-100 angstroms of the sample surface and requires ultra-high vacuum to prevent contamination. The technique produces characteristic peaks in spectra that can be matched to elemental binding energies to determine sample composition.
The document provides an introduction to optoelectronic devices, including their operation and key properties. It discusses:
1) The wave nature of light and how it is described by Maxwell's equations.
2) Polarization and the electromagnetic spectrum, including visible, infrared, and ultraviolet light ranges.
3) Types of optoelectronic devices like p-n junction diodes, heterojunction diodes, laser diodes, photoconductive cells, pin photodiodes, avalanche photodiodes, and photovoltaic cells. It provides details on their principles, structures, and applications.
This document discusses diamond thin films produced through chemical vapor deposition. It describes how CVD involves activating carbon-containing gases through thermal or electrical methods to decompose the gases and deposit diamond on a substrate surface. Key points covered include:
1) CVD is able to grow diamond on non-diamond substrates by thermally decomposing gases like methane and hydrogen at temperatures over 700°C.
2) The deposition process involves gas activation, surface reactions, and diamond nucleation and growth in a three-dimensional crystal structure.
3) Applications of CVD diamond thin films include cutting tools, thermal management, optics, and electronic devices due to diamond's properties of hardness, heat conductivity, and transparency.
This document defines electro-optic effects and describes how an external electric field can induce changes in the refractive index of a material, modulating its optical properties. It discusses the Pockels effect specifically, where a linear change in refractive index occurs due to an applied electric field. This effect can be used to build integrated optical modulators and switches, such as a transverse Pockels cell that inserts a phase difference between orthogonal field components, acting as a polarization modulator. The phase difference can be converted to an intensity variation using an interferometer such as a Mach-Zehnder configuration.
This document discusses the development of quantum mechanics. It summarizes that classical physics could not explain certain experimental observations, leading to quantum theory. Key events were Planck's blackbody radiation law, Einstein's explanation of the photoelectric effect using light quanta (photons), and Compton's discovery that photons transfer momentum to electrons. The photoelectric effect showed that light behaves as particles (photons), while the de Broglie hypothesis and Davisson-Germer experiment showed that electrons can behave as waves. This established the wave-particle duality of both light and matter.
Coulomb blockade occurs when the electrostatic energy required to add a single electron to a microscopic conductor is greater than the thermal energy. This results in a gap in the conductor's energy levels and prevents electron tunneling below a threshold voltage that depends on temperature. A single electron transistor uses controlled electron tunneling between a source and drain electrode connected by a quantum dot or wire channel to amplify current. It operates by changing the quantum system's energy levels with a gate voltage to allow electrons to tunnel one by one. Mathematical modeling of the single electron transistor involves calculating tunneling rates and probabilities based on free energy changes from electron additions or removals.
This document describes an experiment to determine the numerical aperture of an optical fiber. It provides background information on numerical aperture and how it is defined as the light gathering ability of an optical fiber. It then describes the experimental procedure and equipment used, which involves connecting an optical fiber to a trainer board and measuring the diameter of the light spot emitted at different distances from the fiber end. The results are tabulated and show that the numerical aperture of the optical fiber tested is 0.4.
Introduction to nanoscience and nanotechnologyaimanmukhtar1
Introduction of nanoscience/nanotechnology ,properties/potential applications of nanomaterials and electrodeposition of metal single component and alloy nanowires in AAO template
This document discusses different types of phase retardation plates, including quarter-wave plates and half-wave plates. It begins by introducing how retarders change the polarization of light by causing a phase lag between the two polarization components. It then defines a phase retardation plate as a uniformly thick birefringent crystal plate that produces a definite phase difference between the ordinary and extraordinary rays. It provides details on how quarter-wave plates and half-wave plates produce specific phase differences of π/2 and π respectively. Applications of quarter-wave plates and half-wave plates including converting between linear and circular polarization and rotating the polarization plane are also summarized.
This document provides an overview of optical fiber communication. It discusses the history and development of optical fibers, including the discovery of total internal reflection and development of glass coatings to reduce signal loss. It describes the basic components of an optical communication system including light sources, fiber cables, and light detectors. It also covers fiber types, advantages like high bandwidth and low signal degradation, and disadvantages such as higher initial cost compared to copper cables.
This document provides an overview of optical fiber communication (OFC). It begins with the historical development and need for optical systems due to limitations of traditional communication methods. The basics of OFC are explained, including the system block diagram and principles of operation using ray theory and total internal reflection. Fiber types and transmission characteristics such as attenuation and bandwidth are covered. Finally, key optical components used in OFC systems such as fiber splices, connectors, and couplers are outlined.
Introduction of semiconductor oxides in photovoltaic devicesMuhammad Mudassir
This document discusses the incorporation of semiconductor oxides in photovoltaic devices. It explains that semiconductor oxides like ZnO, TiO2, and SnO2 can absorb solar energy due to their band gap. These metal oxide semiconductors can be used as n-type or p-type materials in organic solar cells depending on their conduction and valence bands. The document also discusses how ZnO and TiO2 can be used as photocatalysts in applications like wastewater treatment due to their photoinduced oxidation-reduction reactions when illuminated. Finally, it states that metal oxide semiconductors are useful in technologies involving photon-assisted processes like serving as scaffold layers in dye-sensitized solar cells and transport layers
Metamaterials are artificial structures designed to have unique electromagnetic properties not found in nature, such as a negative refractive index. They are composed of meta-atoms that can manipulate electromagnetic waves at scales smaller than the wavelength of light. Metamaterials have applications in invisibility cloaking, super lenses, compact antennas, absorbing electromagnetic radiation, and mitigating seismic waves. However, designing metamaterials for specific wavelengths is challenging, and they do not work perfectly and are very expensive.
Circularly polarized light consists of two perpendicular electromagnetic plane waves of equal amplitude with a 90 degree phase difference between them. The light illustrated is an example of right-circularly polarized light.
This document discusses CMOS image sensors. It begins by defining an image sensor as a device that converts an optical image into an electrical signal. It then explains the basic operation of CCD and CMOS image sensors, describing how each type works at a pixel level. The document concludes by comparing CCD and CMOS technologies, noting advantages of CMOS such as lower cost and power consumption, while CCD provides better image quality for some applications.
This document discusses quantum dots, which are semiconductors on the nanometer scale that obey the principle of quantum confinement. The energy band gap of quantum dots determines the wavelength of light they can absorb and emit, and this wavelength depends on the size of the dot. Solutions containing quantum dots of different sizes appear different colors because the particles absorb and emit light within the visible spectrum. Potential applications of quantum dots include improving solar cells, use in televisions, and medical imaging.
This document discusses the density of states (DoS) for bulk semiconductors. It begins by defining DoS as the number of available energy states per unit energy interval per unit dimension in real space. It then derives the DoS for bulk semiconductors using the Bloch theorem and shows that the DoS is proportional to the square root of energy. Finally, it defines the effective DoS, which accounts for occupancy based on the Fermi-Dirac distribution.
The document certifies that Mujammil Khan, a class 12 student, completed an independent project on photodiodes under the supervision of his physics teacher, Mrs. Kanika. Khan thanks his teacher, principal, parents, friends, and classmates for their guidance and support during the project. The project report includes sections on the history, theory, types, construction, characteristics, applications, and advantages/disadvantages of photodiodes.
X-Ray Photoelectron Spectroscopy (XPS) is a surface-sensitive technique that uses X-rays to eject electrons from the surface of a sample. An XPS instrument measures the kinetic energy of these ejected electrons to identify the elements present and the chemical and electronic states of the surface. XPS provides information only about the top 10-100 angstroms of the sample surface and requires ultra-high vacuum to prevent contamination. The technique produces characteristic peaks in spectra that can be matched to elemental binding energies to determine sample composition.
The document provides an introduction to optoelectronic devices, including their operation and key properties. It discusses:
1) The wave nature of light and how it is described by Maxwell's equations.
2) Polarization and the electromagnetic spectrum, including visible, infrared, and ultraviolet light ranges.
3) Types of optoelectronic devices like p-n junction diodes, heterojunction diodes, laser diodes, photoconductive cells, pin photodiodes, avalanche photodiodes, and photovoltaic cells. It provides details on their principles, structures, and applications.
This document discusses diamond thin films produced through chemical vapor deposition. It describes how CVD involves activating carbon-containing gases through thermal or electrical methods to decompose the gases and deposit diamond on a substrate surface. Key points covered include:
1) CVD is able to grow diamond on non-diamond substrates by thermally decomposing gases like methane and hydrogen at temperatures over 700°C.
2) The deposition process involves gas activation, surface reactions, and diamond nucleation and growth in a three-dimensional crystal structure.
3) Applications of CVD diamond thin films include cutting tools, thermal management, optics, and electronic devices due to diamond's properties of hardness, heat conductivity, and transparency.
This document defines electro-optic effects and describes how an external electric field can induce changes in the refractive index of a material, modulating its optical properties. It discusses the Pockels effect specifically, where a linear change in refractive index occurs due to an applied electric field. This effect can be used to build integrated optical modulators and switches, such as a transverse Pockels cell that inserts a phase difference between orthogonal field components, acting as a polarization modulator. The phase difference can be converted to an intensity variation using an interferometer such as a Mach-Zehnder configuration.
This document discusses the development of quantum mechanics. It summarizes that classical physics could not explain certain experimental observations, leading to quantum theory. Key events were Planck's blackbody radiation law, Einstein's explanation of the photoelectric effect using light quanta (photons), and Compton's discovery that photons transfer momentum to electrons. The photoelectric effect showed that light behaves as particles (photons), while the de Broglie hypothesis and Davisson-Germer experiment showed that electrons can behave as waves. This established the wave-particle duality of both light and matter.
1. UNIVERZA V LJUBLJANI
ZDRAVSTVENA FAKULTETA
ODDELEK ZA RADIOLOŠKO TEHNOLOGIJO II. STOPNJE
OBSEVALNE TEHNIKE NA TELERADIOTERAPEVTSKEM
ODDELKU ONKOLOŠKEGA INŠTITUTA
Avtor: Andrej Breznik, dipl.inţ.rad.
Mentor: doc. dr. Dejan Ţontar, univ. dipl. fiz.
LJUBLJANA, 2011
2. KAZALO VSEBINE
KAZALO SLIK
Slika 1: Sestava linearnega pospeševalnika ............................................................................... 2
Slika 2: Nameščen tubus in individualna zaščita na obsevalnem aparatu .................................. 4
Slika 3: Porazdelitev globinske doze pri elektronih ................................................................... 4
Slika 4: Večlistni kolimator – MLC ........................................................................................... 5
Slika 5: Porazdelitev globinske doze pri fotonih ....................................................................... 6
Slika 6: LINAC NovalisTX – obsevalni aparat 8 ...................................................................... 8
Slika 7: Primerjava dozne porazdelitve pri različnih obsevalnih tehnikah ................................ 9
Slika 8: Exac Trac 6D robotic IGRT couch sistem .................................................................. 10
Slika 9: Prikaz poravnave z tehniko prekrivanja in deljenega polja pri slikanju z sistemom
Exac Trac.................................................................................................................................. 11
Slika 10: Primerjava obsevalnih planov IMRT in RAPID ARC tehnike obsevanja ................ 13
3. 1 KAJ JE RADIOTERAPIJA?
Radioterapija je medicinska stroka, ki se ukvarja z zdravljenjem malignih in nemalignih
bolezni s pomočjo ionizirajočega sevanja, lahko samostojno ali v kombinaciji z sistemskim in
kirurškim zdravljenjem. Uvrščamo jo med lokalne načine zdravljenja, saj je njen učinek
omejen le na obsevalno območje, kjer se absorbirajo ionizirajoči ţarki. Skupaj s kirurgijo in
sistemskim zdravljenjem je eden izmed treh temeljnih načinov zdravljenja raka.
Glede na poloţaj vira ionizirajočega sevanja v odnosu na obsevanega bolnika delimo
radioterapijo v vsebinskem in organizacijskem delu na teleterapijo (vir je zunaj bolnikovega
telesa) in brahiterapijo (vir je v bolnikovem telesu).
Bolniki so lahko obsevani z fotonskimi ţarkovnimi snopi nizkih (kV) ali visokimi (MV)
energijami in z elektronskimi ţarkovnimi snopi visokih (MeV) energij. Brahiterapevtska
dejavnost se izvaja z napravami za naknadno polnjenje vodil (HDR in LDR), ki jih zdravnik
povprej pod kontrolo različnih slikovnih metod uvede v telo bolnika, z viri ionizirajočega
sevanja.
Kot stroka radioterapija opredeljuje preplet kliničnih znanj in veščin poznavanja značilnosti
malignih in neonkoloških bolezni, ter moţnosti njihovega zdravljenja. Prav tako zavzema
področje radiofizike in radiobiologije, ki poznavata učinke ionizirajočega sevanja v bioloških
sistemih in moţnostih njegove uporabe. Radioterapija vključuje tudi tesno sodelovanje
strokovnjakov, kot so zdravnik specialist radioterapevt (nosilec dejavnosti), medicinski fizik –
dozimetrist (odgovoren za pripravo obsevalnega načrta in umerjanje radioterapevtskih naprav)
in inţenir radiološke tehnologije (upravljalec radioterapevtskih naprav in izvajalec obsevanja)
(Novaković in sod., 2009).
Med osnovne teleterapevtske naprave spadajo radioterapevtski simulator, terapevtska
rentgenska naprava, linearni pospeševalnik in računalniški sistemi za načrtovanje obsevanja in
naprave za preverjanje kakovosti obsevanja (Novaković in sod., 2009).
1
4. 2 LINEARNI POSPEŠEVALNIK - LINAC
V teleterapiji uporabljamo linearne pospeševalnike, ki lahko proizvajajo visokoenergijske
fotone ali elektrone. Sodobni medicinski linearni pospeševalniki pospešujejo elektrone do
kinetičnih energij od 4 MeV do 25 MeV (Novaković in sod., 2009). Linearni pospeševaliki
uporabljajo RF mikrovalovna polja frekvenc od 103 MHz do 104 MHz. Velika večina jih
deluje pri frekvenci mikrovalov 2856 MHz (S-band), kjer so tipične dolţine mikrovalovnih
votlin okrog 10 cm v premeru in 3 cm v dolţini (Majerle, 2003).
Izravnalna Bending magnet
filtra in
sipalne
folije Pospeševalna cev
Izvor elektornovov - GUN
Tarča
Primarni in
sekundrani
kolimator
MLC
Rtg cev -
OBI
Slikovni
detektor
EPID
slikovni
detekotor
Slika 1: Sestava linearnega pospeševalnika
VIR:http://www.google.si/imgres?imgurl=http://www.tradevision.com.bd/images/product/27.jpg&imgrefurl=http://www.tradevision.com.bd
/productlist.php%3Fsubdivid%3D7%26subdivname%3DRadiotherapy&h=600&w=600&sz=71&tbnid=pTS2cx5lOJc0tM:&tbnh=135&tbnw
=135&prev=/images%3Fq%3Dvarian%2Blinac&zoom=1&q=varian+linac&hl=sl&usg=__G5f4fyw7_ohDq65TSNfAwj8o5Ks=&sa=X&ei=
jzV_TY7LGsTYsgaam8jsBg&sqi=2&ved=0CD4Q9QEwBA
2
5. Princip delovanja linearnega pospeševalnika je takšen, da v pospeševalno cev injicirane
elektrone z začetno energijo okoli 50 keV vzdolţ le-te pospešimo s pomočjo
visokofrekvenčnega elektromagnetnega valovanja s frekvenco okoli 3000 MHz. V
pospeševalni cevi je vakuum, ki zagotavlja čim manjše število trkov elektronov z molekulami
plina in s tem čim manjše oviranje elektronov. Ob izhodu iz pospeševalne cevi dobimo ozek
snop elektronov s premerom cca 3 mm, ki ga v nadaljevanju s pomočjo magnetnih polj
usmerimo (odklonimo) v navpično smer. Elektronski curek lahko uporabljamo neposredno
(obsevanje z elektroni) ali pa ga izkoristimo za nastanek rentgentskih fotonov z usmeritvijo
elektronov v tarčo (Novaković in sod., 2009).
V principu ločimo dve vrsti obsevanja, glede na vrsto ionizirajočega sevanja:
- obsevanje z elektroni,
- obsevanje s fotoni.
2.1. Obsevanje z elektronskim snopom
V primeru obsevanja z elektronskim snopom, pospešeni elektroni trčijo ob vstavljeno tanko
kovinsko sipalno folijo, katera ţarek razprši, hkrati pa poskrbi za homogenost obsevalnega
polja, kar pomeni, da je količina elektronov po celotnem preseku obsevalnega polja enaka
»dose flattnes«. Debeline sipalnih folij so takšne, da se elektroni v preteţni meri sipljejo in da
ne prihaja do dodatnega zavornega sevanja. Izhodni snop elektronov omejujemo z t.i.
aplikatorji oz. tubusi in individualnimi zaščitami iz Woodove zlitine, ki posnemajo obliko
tarče. Tipične energije za obsevanje z elektorni so: 6, 9, 12, 15 in 18 MeV. Globinska
porazdelitev doze pa je odvisna od jakosti energije. Pomembno je vedeti, da ima obsevanje z
elektroni hiter padec izodozne krivulje, ko ta doseţe 80%. Na takšen način se lahko izognemo
nepotrebnemu obsevanju t.i. kritičnih oz. zdravih organov. (Novaković in sod., 2009).
3
6. Slika 2: Nameščen tubus in individualna zaščita na obsevalnem aparatu
Vir: http://www.flickr.com/photos/vm1757/562061042/sizes/m/in/photostream/
100,0
6 MeV
9 MeV
80,0
12 MeV
PDD [%]
15 MeV
60,0
18 MeV
40,0
20,0
0,0
0 2 4 6 8 10 12
globina [cm]
Slika 3: Porazdelitev globinske doze pri elektronih
Slika 3 prikazuje razmerje med globino in odstotkom globinske doze (angl. Percent depth
dose – PDD) pri elektronskem snopu.
4
7. 2.2. Obsevanje s fotonskim snopom
Fotonsko obsevanje poteka po postopku, da elektroni na poti iz pospeševalne cevi trčijo na
vstavljeno tarčo, ki je snov z visokim vrstnim številom Z. V tarči prihaja do zavornega
sevanja in rezultat je nastanek visoko energijskih fotonov primernih za fotonsko obsevanje. V
nadaljevanju fotoni zadanejo izravnalni filter, ki poskrbi, da je ţarek po prehodu skozenj po
svojem preseku čim bolj homogen oz. izravnan. Za dodatno omejitev fotonskih ţarkov skrbi
serija zaslonk, ki ţarek še dodatno oblikujejo. Zadnji element, ki omogoča skoraj poljubno
oblikovanje obsevalnih poljm je t.i. večlistni komatorski sistem MLC (angl. MultiLeaf
Collimator), s katerim oblikujemo fotonska obsevalna polja tako, da ta povzamejo obliko
obolenja, kot ga vidimo iz smeri ţarkov. Sodobni pospeševalniki imajo vgrajen tudi EPID –
elektronski portalni sistem za verifikacijo obsevalnih polj. Pri fotonskem načinu obsevanja se
posluţujemo energijama 6 MV in 15 MV (Novaković in sod., 2009).
Slika 4: Večlistni kolimator – MLC
Vir: http://varian.mediaroom.com/file.php/301/MLC+-+gold.jpg
5
8. 100
6 MV
15 MV
80
Kobalt
PDD [%]
60
40
20
0
0 10 20 30 40
globina [cm]
Slika 5: Porazdelitev globinske doze pri fotonih
Slika 5 prikazuje razmerje med globino in odstotkom globinske doze (angl. Percent depth
dose – PDD) pri fotonskem snopu.
6
9. 3 NOVE OBSEVALNE TEHNIKE NA OI
Vključitev novih obsevalnih tehnik v delovno rutino je pogojena z uporabo CT simulatorja in
sodobne podprte računalniške programe, ki s pomočjo algoritmov omogoča izdelavo
natančnega obsevalnega načrta. Z razvojem računalniške podprte tehnologije je sledil tudi
razvoj popolnega računalniškega nadzora oz. krmiljenje linearnih pospeševalnikov, večlistnih
kolimatorjev za oblikovanje obsevalnega polja in računalniško podprtega sistema za
načrtovanje obsevanja (Novaković in sod., 2009).
Prednosti novih obsevalnih tehnik omogoča:
- povečanje gradienta med visokodoznim in nizkodoznim območjem,
- povečanje konformnosti visokodoznega območja (skladnost s 3D obliko tarče),
- natančnejše obsevanje (zmanjšanje odmika lege posameznega polja od referenčne).
Na Onkološkem inštitutu v Ljubljani smo z nakupom novejših obsevalnih aparatov pričeli
obsevati naslednje različne obsevalne tehnike:
- IMRT – intizitetno modulirana radioterapija (angl. Intensity-modulated radiation
therapy)
- IGRT – slikovno vodena radioterapija (angl. image-guided radiotherapy)
- SRT – stereotaktična radioterapija (angl. stereotactic radiotherapy)
- SRS – stereotaktična kirurgija (angl. stereotactic radiosurgery)
- RAPIR ARC – volumetrično ločno obsevanje (angl. VMAT - volumetric arc therapy)
7
10. Infrared sistem Silicijeva slikovna detektorja
Robotic 6D
OBI – On
couch – Exac
board
Trac
Imager
Room based x
ray
Slika 6: LINAC NovalisTX – obsevalni aparat 8
VIR: http://www.jeffradonc.com/page.php?pID=21
3.1. IMRT – Intenziteno modulirana radioterapija
Intizitetno modulirano obsevanje – IMRT je sodobna obsevalna tehnika, ki zdruţuje vse
doseţke moderne računalnike tehnologije. V primerjavi z navadnimi konvencionalnimi
obsevalnimi tehnikami, lahko z IMRT doseţemo pomembno izboljšanje razporeditve doze v
obsevalnem tkivu. To se kaţe v večji konformnosti, ki jo dopolnjuje strm gradient doze na
robu tarčnega volumna, kar nam omogoča bolj natančno in usmerjeno obsevanje samega
tumorja in manjšo dozno obremenitev zdravih tkiv v okolici tumorja. S tem pripomoremo k
zmanjšanju verjetnosti pojavljanja in restnosti nezaţelenih stranskih učinkov (Strojan in sod.,
2010).
Poznamo več načinov IMRT tehnike, med najpogostejše sodita:
- dinamična tehnika (angl. sliding windows) deluje tako, da obsevanje traja ves čas,
torej kontinuirano s pomočjo premikanja MLC lističev in s tem tudi pogojeno
spreminjanje obsevalnega polja;
8
11. - stopenjska tehnika (angl. step and shoot) deluje na principu »prestavi in sproţi«, kar
pomeni, da se ţarek sproţi le, kadar obsevalno polje zavzame določeno obliko oz. se
lističi kolimatorskega sistema zapeljejo v ţe naprej določeno leg.
Iz kliničnega vidika se IMRT od konvencionalnega 3D obsevanja razlikuje v tem, da
omogoča večjo konformnost, kar pomeni, da izodoze natančneje posnemajo 3D obliko
tarčnega volumna in konkavno oblikovanje obsevalnega polja. IMRT tehnika uporablja
računalniško vodeno modulacijo intenzitete s krmiljenjem večlistnih kolimatorjev (Strojan in
sod., 2010).
Prednosti IMRT tehnike pred ostalimi tehnikami:
- bolj homogena porazdelitev doze v tarči kot pri 3D konformalnem obsevanju,
- niţja dozna obremenitev izven PTV (planirnega terčnega volumna),
- omogoča oblikovanje pol z konkavnimi oblikami,
- omogoča kompenzacijo nehomogenosti polj.
Prikaz tehnike »sliding windows« IMRT: http://www.youtube.com/watch?v=Llxe9t8wwB0.
Slika 7: Primerjava dozne porazdelitve pri različnih obsevalnih tehnikah
VIR: IMRT obsevanje ORL bolnika (Kuduzović in Sekereš, 2010)
9
12. 3.2. IGRT – Slikovno vodena radioterapija
Slikovno vodena radioterapija – IGRT nam omogoča izvajanje slikovno vodene metode
kvalitete obsevanja pred vsakim ali celo med samim obsevanjem. Namen IGRT tehnike je
zagotoviti, da je planirni tarčni volumen (PTV) vedno v enakem poloţaju med samim
obsevanjem (Varian Inc., 2011).
Z tehniko IGRT lahko predvsem zmanjšamo napake obsevanja zaradi:
- premikanja tarče med obsevanji (intra-fractional),
- premikanja tarče med obsevanjem (inter-fractional),
- napak pri pozicioniranju pacienta.
Radiološki inţenirji se pri delu posluţujemo različnih komponent obsevalnega aparata in
nekatere pomembne komponenete za izvajanje IGRT tehnike so:
- Exac Trac X-ray 6D robotic system,
- IR sistem,
- On-board Imager (OBI) kV sistem za cone-beam CT (CBCT),
- Portal Vision slikovni sistem.
Slika 8: Exac Trac 6D robotic IGRT couch sistem
VIR: http://www.newswise.com/articles/new-image-guided-radiotherapy-system-benefits-high-risk-patients
10
13. Exac Trac 6D robotic IGRT couch se uporablja za uravnavanje nepravilnosti, ki nastanejo
pri vsakodnevnnem pozicioniranju pacienta v poloţaj izocentra. Sestavni deli Exac Tracta so:
dve vgrajeni rentgenski cevi v prostoru linearnega pospeševalnika, dva silicijeva detektorja in
IR sistem za detekcijo rentgenske slike in hkrati poloţaja pacienta.
Slika 9: Prikaz poravnave z tehniko prekrivanja in deljenega polja pri slikanju z sistemom Exac Trac
VIR: http://www.varian.com/media/oncology/resources/flash/obi_image_gallery/portal_vision.html
3.2.1 On-board Imager (OBI)
Uporaba On-board Imager (OBI) sistema omogoča bolj učinkovito in primerno dinamično
spremljanje obsevalne tarče – obsevalnega polja ter naslenje podrobnosti:
- pravilno pozicioniranje bolnika v primerjavi z izocentrom,
- verifikacijo obsevalnih polj v primerjavi z določenimi markerji in terapijo z
obsevanjem,
- pozicioniranje obsevalnega poljna glede na implantirane zlate markerje ali kostne
strukture,
- izboljšan nadzor nad tumorjem pred in med obsevanjem,
- zaznavanje sprememb pri premikanju notranjih organov in spremembe pri dihanju,
11
14. - zajete visoko kvalitetne slike omogočajo hitrejšo obravnavo in pregled anatomskih
razlik,
- sprejemanje odločitev o morebitnih premikih izocentra pred obsevanjem,
- nizke kV dozne obremenitve omogočajo dnevno preverjanje obsevalnih polj.
S pomočjo OBI sistema in računalniških programov izvedemo korekcijo obsevalnih polj, ti.
»repozicioniranje bolnika«. Repozicioniranje lahko opravimo na dva načina in sicer na:
a) kostne strukture
- omogočanje direktne določitve obsevalne tarče
- kostne strukure so zanesljiva orientacija za določitev obsevalne tarče
b) implantirana zlata zrnca – markerje
- prilagoditev izocentra obsevalnega polja na določen implantirani zlati marker
(Varian Inc., 2011).
Prikaz IGRT, link: http://www.youtube.com/watch?v=8ySdWkx6m_c&feature=related.
3.3. RapidArc – volumetrično ločno obsevanje
Obsevalna tehnika RapidArc je omogočila velik napredek pri obsevanju bolnikov, saj
izboljšuje skladnost med odmerkom doze in skrajšanim časom obsevanja. RapidArc tehnika
deluje na princupu računalniških algoritmov, ki samodejno premikajo gantrij, kateri obkroţi
bolnika na obsevalni mizi za 360° in hkrati uravnavajo sekvenčno premikanje »sliding
window« MLC lističev in spreminjajočo se intenziteto sevanja (dose rate). Vse to omogoča
kontinuirano in učinkovitejše, ter predvsem hitrejše obsevanje za razliko od ostalih tehnik
(Varian Inc., 2011). RapidArc nam omogoča prenos celotne frakcionirane doze s tehniko
IMRT v eni sami rotaciji gantrija za 360° (Zankowski, 2007).
Glavne prednosti obsevalne tehnike RapidArc so:
- simultano gibanje gantrija okoli pacienta za 360°, kar omogoča optimalno
porazdelitev doze v bolniku,
12
15. - simulatano premikanje MLC-jev z načinom t.i. »sliding window«,
- nadzor nad hitrostjo premikanja gantrija,
- Varianov patentiran »gridded gun«, ki omogoča sprotno spreminjanje intenzitete
izhodnega snopa iz obsevalnega aparata,
- minimalen čas obsevanja (navadno okoli 1-2 min) (Zankowski, 2007).
Prikaz Rapid Arc, link: http://www.youtube.com/watch?v=fMIW2SRTE1I&feature=related.
Slika 10: Primerjava obsevalnih planov IMRT in RAPID ARC tehnike obsevanja
VIR: http://www.varian.com/us/oncology/treatments/treatment_techniques/rapidarc/comparison.html
13
16. 4 LITARATURA
- Novaković in sod. (2009). Onkologija. Raziskovanje, diagnostika in zdravljenje raka.
1. izd. Ljubljana: Mladinska knjiga; 120-154.
- Majerle M. (2003). Umerjanje linearnega pospeševalnika Philips SL-75/5 za potrebe
3D načrtovanja v radioterapiji. Diplomsko delo. Univerza v Ljubljani. Fakuleteta za
matamatiko in fiziko; 30-58
- Strojan in sod. (2010). Onkologija. Intenzitetno modulirano obsevanje (IMRT) zdaj
tudi na Onkološkem inštututu v Ljubljani. Leto XIV. Onkološki Inštitut; 91-96
- Evans et al (2001). Performance assessment of the Gulmay D3300 kilovoltage X-ray
therapy unit. The British Journal of Radiology. 74 (2001). The British Institute of
Radiology; 537–547
- Zankowski C (2007). Varian’s NewRapidArc™ Delivery. The Next Dimension in
Speed and Precision. Centerline: 1-5
- Advance radiation center of New York (2011). Image radiatoin radiotherapy and
Rapid Arc technology.
http://advancedradiationcenters.com/?p=whatisigrt <10.5.2011>.
- Varian Inc. (2011). Varian radiation oncology program solution.
http://www.varian.com/us/oncology/radiation_oncology/ <14.5.2011>.
14