Varian
Plate 01Varian 21Ex
The machine is equipped with a multi-leaf collimator (MLC) available as an 80-leaf or a 120-leaf model, the latter having 5 mm leaf width in the central 20 cm and 10 mm in the outer 20 cm of a 40×40 cm field. Optional on-board imaging (OBI) provides kV x-ray and cone-beam CT for image-guided radiation therapy (IGRT). Portal imaging is available with LC250, aS500, or aS1000 electronic portal imaging devices (EPIDs).[1]
The machine is compatible with three-dimensional conformal radiation therapy (3D-CRT), intensity-modulated radiation therapy (IMRT), and, when equipped with OBI and appropriate MLC, volumetric modulated arc therapy (VMAT) and stereotactic radiosurgery/stereotactic body radiation therapy (SRS/SBRT).[1]
The optional kV imaging and cone-beam CT allow daily patient positioning verification and soft-tissue imaging, enabling adaptive radiotherapy approaches though the Clinac 21EX generation does not include iterative CBCT or dedicated adaptive radiotherapy software.[1]
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The following facts about the 21EX Silhouette are absent from this record as of this revision. First-hand knowledge or a citation closes a gap; every submission is reviewed before publication.
No publicly documented production dates or lifecycle milestones (introduction, end of production, EOL) for the 21EX Silhouette are on record.
Answerable by: OEM historical records or a trade-press announcement
No publicly documented variants, configuration options, or revision breakpoints of the 21EX Silhouette are on record.
Answerable by: an OEM product catalog or an engineer who ordered or specified the tool
The control-system platform and OS era of the 21EX Silhouette are not on record.
Answerable by: an engineer who operated it or OEM installation records
No publicly documented failure modes or field errata for the 21EX Silhouette are on record.
Answerable by: a field service engineer, process engineer, or maintenance technician
No publicly documented compatible parts, consumables, or accessories for the 21EX Silhouette are on record.
Answerable by: an OEM parts catalog or a service engineer
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Last updated Sep 22, 2026.