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[[File:MLCShape.svg|thumb|''MLC shape of an X-MLCs'']]
A '''multileaf collimator''' ('''MLC''') is a [[collimator]] or beam-limiting device that is made of individual "leaves" of a high [[atomic numberednumber]]ed material, usually [[tungsten]], that can move independently in and out of the path of a [[external beam radiotherapy|radiotherapy beam]] in order to shape it and vary its intensity.
MLCs are used in external beam radiotherapy to provide conformal shaping of beams. Specifically, [[Radiation therapy#External beam radiation therapy|conformal radiotherapy]] and [[Intensity Modulated Radiation Therapy]] (IMRT) can be delivered using MLCs.
The MLC has improved rapidly since its inception and the first use of leaves to shape structures in 1965 <ref>{{cite journal | last=Takahashi, | first=S., "| title=Conformation radiotherapy:. rotationRotation techniques as applied to radiography and radiotherapy of cancer",. ''| journal=Acta Radiol.Radiologica: Suppl.Diagnosis 242| (year=1965) 1–142''| issn=0567-8056 | pmid=5879987 | page=Suppl 242:1+}}</ref> to modern day operation and use. MLCs are now widely used and have become an integral part of any radiotherapy department. MLCs were primarily used for conformal radiotherapy, and have allowed the cost-effective implementation of conformal treatment with significant time saving,<ref>{{cite journal | last1=Brewster, L.;| first1=Linda | last2=Mohan, R.;| first2=Radhe | last3=Mageras, G.;| first3=Gig | last4=Burman, C.;| first4=Chandra | last5=Leibel, S.| andfirst5=Steven | last6=Fuks, Z.,| first6=Zvi | "title=Three dimensional conformal treatment planning with multileaf collimators", ''Int.| J.journal=International Rad.Journal Onc.of Biol.Radiation Phys. 33 (1995) 1081–9''</ref><ref>HelyerOncology, S. J. and HeisigBiology, S.,Physics "Multileaf| collimationpublisher=Elsevier versusBV conventional| shieldingvolume=33 blocks:| aissue=5 time| anddate=1995-12-01 motion| studyissn=0360-3016 of| beampmid=7493834 shaping| in radiotherapy", ''Raddoi=10. Onc. 37 1016/0360-3016(199595)02061-6 | 61–4''pages=1081–1089}}</ref> and also have been adapted for use for IMRT treatments. For conformal radiotherapy the MLC allows conformal shaping of the beam to match the borders of the target tumour. For intensity modulated treatments the leaves of a MLC can be moved across the field to create IMRT distributions (MLCs really provide a [[fluence]] modulation rather than intensity modulation).
[[File:Collimatore multilama.jpg|thumb|Leaves, changing shape, direct the beam to the right [[cancer]] area]]
The MLC is an important tool for radiation therapy dose delivery. It was originally used as a surrogate for alloy block field shaping and is now widely used for IMRT. As with any tool used in radiotherapy the MLC must undergo commissioning and quality assurance. Additional commissioning measurements are completed to model a MLC for [[treatment planning]]. Various MLCs are provided by different vendors and they all have unique design features as determined by specifications of design,<ref>{{cite journal | last1=Galvin, J.| first1=James M.; | last2=Smith, A.| first2=Alfred R. and| last3=Lally, B.,| first3=Brian | "title=Characterization of a multi-leafmultileaf collimator system" | journal=International Journal of Radiation Oncology, ''Int.Biology, J.Physics Rad.| Onc.publisher=Elsevier Biol.BV Phys.| volume=25 (| issue=2 | date=1993-01-15 | issn=0360-3016 | pmid=8420867 | doi=10.1016/0360-3016(93)90339-w | 181–92''pages=181–192}}</ref> and these differences are quite significant.
==References==
[[Category:Particle accelerators]]
[[Category:Radiation therapy]]
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