Conventional Linear Accelerators FourPx Articles

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Modern linear accelerators are devised to enable intensity- modulated radiotherapy (IMRT). This namely a dynamic radiotherapy delivery usage which enables agreeable control over the three-dimensional potion distribution: the conveyed beam instead of being flat, changes the intensity at different points within the beam.
The operation of linear accelerators should be according to the existing criteria and regulations which include: IEC standards,[link widoczny dla zalogowanych], radiation regulations, guidelines for radio therapy room design, etc.
The linear accelerators’ three-dimensional imaging systems can be materialized in three different ways:
1. Applying diagnostic x-ray cone beam, in plain or orthogonal to the linear accelerators
* Arc therapy methods: in which the radiation runs continuously and the gantry collimators and MLC leaves are all moving continuously. The dose rate also varies during the delivery. Treatments are delivered in an arc (know next to nothing ofmetimes in two arcs). This is probably the best alternative for IMRT.
Radiotherapy works at targeting high-energy gamma ray alternatively electron beam onto cancer cells,[link widoczny dla zalogowanych], which are extra disposed to radiation harm than the customary tissues. Linear accelerators are commonly multi-modality ionizing radiation generators with associated imaging devices, currently used for delivery of external beam radiotherapy.
The present-day linear accelerators provide either 6 MeV photons in the “low energy” scope machines, or dual/triple photon energy and several electron energies.
* Dynamic MLC methods: in which the radiation runs constant, while the MLC leaves shake cross the field at variable speeds.
The imager systems differ in the degree of complexity of software invested, as well as the ease of use.
The technology used in conventional linear accelerators is essentially the same for entire linear accelerators. The high energy generation can be achieved either by implementing the “traveling waveguide technology” or by implementing the “standing waveguide technology”. The 1st approach is simpler and quite reliable, meantime the second reach features a more settled treatment beam. The generated radiation beam is flattened and shaped using collimation devices to form a beam matching the shape of the tumor. The wag adviser, the filters and the collimator are mounted ashore a gantry which rotates approximately the patient, allowing the tumor to be irradiated from multiple directions. There is a linear accelerators patient coach principally designed to permit irradiation of the patient from multiple instructions.
Other added traits may be merged into the linear accelerators, such as: arc-based IMRT Delivery,[link widoczny dla zalogowanych], aggregate body irradiation, high-dose rate electrons, etc.
* Step and shoot method: this method consists of delivering a array of different shape fields formed by the MLC to establish up a variable intensity pattern. The irradiation is stopped between each field.
The following systems are incorporated into the linear accelerators: multileaf collimator (MLC) for beam shaping, capability to deliver intensity modulated radiotherapy (IMRT) and a 3D picture guidance system (IGRT). The linear accelerator also provides an electronic entry imaging system for imaging treatment beams.
The multileaf collimator is a delicate computer-controlled machinery. The performance of the collimator depends on its resolution, the leakage radiation and the system penumbra.
The electronic portal imaging appliance allows verification of patient position on orthogonal two-dimensional images produced by the high-energy treatment beam. The detector used for the portal imaging consists of an amorphous silicon oblique revelation flat plate imager.
Despite the tall chief cost of purchasing linear accelerators, their tall patient throughput over a long lifespan makes them exceedingly cost-effective compared with the additional handling adoptions.
Technical Considerations
There are differ types of linear accelerator IMRT allocation methods: