partElekta

Elekta Agility MLC

Elekta's 160-leaf high-resolution multi-leaf collimator — the current-generation MLC on the Versa HD and a retrofit option on later Synergy / Infinity platforms. Agility's design distinction is the 80 leaf-pair, 5 mm-leaf-width-throughout geometry — a uniform 5 mm leaf width across the full field, in contrast to Varian's Millennium 120 (5 mm central + 10 mm outer) or the dual-bank designs on prior Elekta platforms.

For SRS / SBRT and small-field VMAT delivery, the uniform-leaf-width geometry simplifies the planning model and improves achievable conformity at the periphery of larger targets. Agility is one of the principal differentiators marketed for the Versa HD platform, alongside the high-dose-rate FFF (flattening-filter-free) treatment mode.

Fits

Family / configurations

  • Agility (standard) — 160 leaves, 80 leaf pairs, 5 mm leaf width throughout, 40 cm × 40 cm maximum field.
  • Predecessor: Elekta MLCi / MLCi2 — 80-leaf configurations with 10 mm leaf width.
  • Beam Modulator — different Elekta design for high-precision small-field use, smaller maximum field size, finer leaf width. Distinct product from Agility.

Failure modes

  • Leaf-positioning drift — individual leaves drift from commanded position; calibration restores. Cumulative drift past tolerance is the end-of-service indicator. See MLC leaf-positioning drift.
  • Motor failure — Agility uses brushless motors with closed-loop position control; motor failures manifest as stuck or slow-tracking leaves.
  • Encoder / position-readout faults.
  • Leaf-bank thermal stability — sustained high-duty-cycle delivery (intensity-modulated arcs over many fractions per day) generates heat in the leaf bank that can affect calibration; Agility includes active cooling on the leaf bank.

Diagnosis

  • Picket-fence + similar QA patterns.
  • Per-leaf log analysis from delivered fractions.
  • Agility-specific QA tools in Elekta's service stack.
  • TG-142 / TG-50 quality-assurance protocols.

Replacement path

  • Per-leaf motor swap for individual failures.
  • Full leaf-bank service for systemic issues.
  • MLC head replacement as a major capital event.

Field notes

  • Newer line than Varian Millennium — Agility installed base is younger, refurb supply thinner.
  • 5 mm uniform-leaf-width is a positioning advantage for SRS / SBRT planning vs the variable-leaf-width Millennium geometry.
  • Active leaf-bank cooling is a maintenance item distinct from prior Elekta MLC designs.
  • Cross-OEM MLC comparisons reduce to: Agility (Elekta) vs Millennium 120 / HD120 (Varian) vs Accuray-specific MLCs on TomoTherapy / Radixact / CyberKnife. Each has a distinct planning-model signature.

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