Radiotherapy CT Simulator PDF

G Simulators and CT Simulators ❑ Simulators and CT simulators cover several important steps in the radiotherapeutic process related to: ❑ Determination of target location within the patient. ❑ Determination of the target shape and volume. 93 -, ❑ Determinati...

G Simulators and CT Simulators ❑ Simulators and CT simulators cover several important steps in the radiotherapeutic process related to: ❑ Determination of target location within the patient. ❑ Determination of the target shape and volume. 93 -, ❑ Determination of the location of critical structures adjacent to treatment volume. - ❑ Planning of dose delivery procedure (treatment planning). ❑ Accuracy of dose delivery to the target. M.Sc. Medical Physics Dr. Khalid I Hussein  i2 5 / fil so Radiotherapy Simulator ❑ Radiotherapy simulator consists of a diagnostic x- ray tube mounted on a rotating gantry to simulate geometries of isocentric teletherapy machines and isocentric linacs. · Y j, & - · Si :53 n M.Sc. Medical Physics Dr. Khalid I Hussein  & Kup 2 mas Radiotherapy Simulators ❑ The simulator enjoys the same degrees of freedom as a megavoltage therapy machine, however: YS. ❑ Rather than providing a megavoltage beam for dose delivery. therapy simulter, assels zadio I ❑ It provides a diagnostic quality x-ray beam suitable for planar imaging (fluoroscopy and radiography) and cone beam CT. · M.Sc. Medical Physics Dr. Khalid I Hussein Radiotherapy Simulators Pastor ❑ In megavoltage machines, radiation fields are defined with collimators (upper and lower jaws). basic ❑ In&simulators radiation fields (square and rectangular) are indicated with delineator wires while the radiation field, defined with a collimator, provides a field that 55s. exceeds in size the delineated field to enable visualization of the target as well as healthy tissues adjacent to the target. M.Sc. Medical Physics Dr. Khalid I Hussein  Radiotherapy Simulators 55 ❑Modern simulator covers the following processes: ·nig 2 31 , = 93 , · ❑Tumour and adjacent normal tissue localization. ❑Treatment simulation.⑫S To ❑Treatment plan verification. d > - ❑Monitoring of treatment. 2/ 2x419 - 9 ❑Components of radiographic simulators: fur ❑Imaging source & detector. - ❑Localizing lasers. 3 ❑Optical distance indicator. ❑Field light. jig? gponig's ❑Patient support assembly M.Sc. Medical Physics Dr. Khalid I Hussein  A flat table surface ensures the patient’s position during simulation is the same as during treatment.on a megavoltage machine Radiotherapy CT Simulator. % 359 * ❑CT simulators are CT scanners equipped with special features dedicated to the radiotherapy process, such as: ❑ Flat table top surface to provide a patient position during simulation that will be identical to the position during treatment on a megavoltage machine. -Y ❑ Laser marking system to transfer the coordinates of the tumour isocentre to the surface of the patient. 35: g - ❑ Virtual simulator consisting of software packages to allow the user to define and calculate a treatment isocentre and $1/s then simulate a treatment using digitally reconstructed I-S To radiographs (DRRs). - M.Sc. Medical Physics Dr. Khalid I Hussein Radiotherapy CT Simulator ❑Oncology CT simulator (Philips) ❑Bore opening: 85 cm C ❑Flat table top j gar M.Sc. Medical Physics Dr. Khalid I Hussein  7)M -6424151 ,1 Liji ↓ Radiotherapy CT Simulator - -- M - The major steps in the target localization and field design are: ❑Physical simulation = ga i (1) Acquisition of the patient data set. - (2) Localization of target and adjacent structures. (3) Definition and marking of the patient coordinate system. · &/Y Will g 5 o ❑Virtual simulation (1) Design of treatment fields. (2) Transfer of data to the treatment planning system (TPS). (3) Production of images used for treatment verification. M.Sc. Medical Physics Dr. Khalid I Hussein  VI Radiotherapy CT Simulator ❑CT simulation process: ❑Patient data set is collected and target localization is carried out using CT axial images. - ❑Laser alignment system is used for marking. - ❑Virtual simulator software package is used for field design and - production of-verification images (DRRs). ❑Transfer of patient data to the TPS is achieved electronically. tretmanty sti e => M.Sc. Medical Physics Dr. Khalid I Hussein Radiotherapy CT Simulator ❑ Digitally reconstructed radiograph (DRR) is the digital equivalent of a planar simulation x-ray film. - - ❑ DRR is reconstructed from a CT data set using virtual simulation software available on CT simulator or on TPS tretment planning = - & sisty mu - 95 -, ❑ DRR represents a computed radiograph of a virtual patient generated from a CT data set representing the actual patient. - => ❑ Like a conventional radiograph, the DRR accounts for beam - divergence. => M.Sc. Medical Physics Dr. Khalid I Hussein Radiotherapy CT Simulator Virtual Simulation - 3 - ,1 > ❑ Synthetic radiographs can be produced by tracing ray- lines from a-virtual source position through the CT data of - - the patient to a virtual film plane and simulating the attenuation of x-rays. - 7 - ❑ Synthetic radiographs are called Digitally Reconstructed Radiographs (DRRs).- ❑ Advantage of DRRs is that anatomical information may be used directly in the determination of treatment field parameters. · a s5  Radiotherapy CT Simulator Beam’s eye view (BEV) - ❑ Beam’s eye views (BEV) are projections through the patient onto a virtual film plane perpendicular to the beam direction -- ⑧ ❑ BEVs are frequently superimposed onto the corresponding DRRs resulting in a synthetic representation of a simulation -- radiograph. > - -