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Tungsten Multiple Layer Multileaf Collimator is used in a radiation system for giving a radiation beam in a desired beam direction, encompassing a first layer of a plurality of radiation shielding tungsten leaves, the leaves being arranged adjoining to one another so as to constitute two opposed rows of adjacently positioned leaves and being movable in a longitudinal direction, that is basically across to the beam direction, determining the radiation beam in shaping field between the opposite ends of the leaves. A second layer of a plurality of radiation shielding tungsten leave, the leaves of the second layer being placed adjacent to one another so as to make two opposed rows of transversely positioned leaves and being movable in a cross-over direction, which is basically adjoing to the beam direction and angled with respect to the longitudinal direction.
The Applications of Tungsten Multiple Layer Multileaf Collimator
Tungsten Multiple Layer Multileaf Collimator is a significant device for radiation therapy and dose delivery. It was primarily used as an alternative for tungsten alloy block field shaping and is now significantly used for Intensity Modulated Radiation Therapy. For conformal radiotherapy, the tungsten multiple layer multileaf collimator enables the conformal shaping of the linear accelerator (LINAC) beam to suit the borders of the target tumour. For intensity modulated treatments the tungsten alloy leaves of a multi-leaf collimator can be transported across the field to make Intensity Modulated Radiation Therapy distributions (tungsten alloy multi-leaf collimator actually gives a fluence modulation rather than intensity modulation).
The Advantages of Tungsten Multiple Layer Multileaf Collimator
Fast tracking: for parallel tungsten alloy leaves, aperture movement is decided by the time needed to cover/uncloak target edges parallel to leaf motion and by leaf speed. Since there is not such target edges for cross leaf - aperture formation, time is resultantly many times faster than that of a parallel tungsten leaf collimator. Besides, cross tungsten alloy leaves are of little weight and lower friction allow the higher leaf speed and reliability then common MLCs.
Improved conformity: cross tungsten leaf suits better for the complex targets (e.g., doubly concave) and removes collimator rotation. Compliance is considerablly enhanced even for a regular shape. Owing to high density that tungsten alloy materials possesses, that is 60% higher than lead, decreases the size of tungsten alloy ray shields, without impacting the radiation shielding ability, the outstanding radiation absorption capacity of tungsten alloy. Since the environment-friendly properties of tungsten alloy, tungsten alloy for radiation shielding better than lead for radiation protecting in environmental preservation.
During design of shielding, tungsten alloy radiation shielding is gathered in accordance with needs of shield to lower down the multiple shielding materials' thickness.
K = e0.693 d / 1/2
K: Shield weakened multiple
1/2: The tungsten alloy radiation protecting material of the half-value layer values