systemLeksellGamma Knife

Elekta Leksell Gamma Knife Icon

Manufacturer: Elekta Leksell · Modality: Gamma Knife

Current-generation Gamma Knife (2015–present). Built on the Perfexion 192-source / 8-sector / 4-8-16 mm collimator architecture, with two platform additions that materially change clinical workflow: an integrated cone-beam CT for in-treatment imaging and image-based stereotactic space definition, and an intra-fraction motion management (IFMM) infrared system that enables frameless thermoplastic-mask-based treatments.

What changes vs Perfexion

  • Integrated CBCT — an on-board kV imaging arm provides CBCT volumes directly in stereotactic space. Eliminates the requirement for invasive frame placement in every case; the CBCT alone can define Leksell stereotactic coordinates.
  • IFMM (Intra-Fraction Motion Management) — a Polaris Vicra infrared camera mounted to the patient couch tracks a reflective marker on the patient's nose during treatment. User-selectable motion threshold from 0.5 mm to 3 mm; if motion exceeds the threshold the beam interlocks.
  • Frameless thermoplastic-mask workflow — Icon supports both the traditional Leksell frame and mask-based immobilization, enabling fractionated stereotactic radiotherapy (single or multi-fraction) where Perfexion was framed-single-fraction only.
  • Same radiation delivery — the 192 Co-60 sources, 8 motorized sectors, tungsten collimator array, and 4 / 8 / 16 mm apertures are architecturally unchanged from Perfexion.

CBCT subsystem

  • X-ray source — 70–120 kVp, 0.6 mm focal spot.
  • Detector — amorphous-silicon panel, 780 × 720 pixels, 0.368 × 0.368 mm pixel pitch.
  • Reconstructed volume — 224 × 224 × 224 mm, 0.5 × 0.5 × 0.5 mm voxels.
  • Presets — low-dose and high-dose acquisitions, balancing patient dose against CNR for the clinical use.

Specs

  • 192 Co-60 sources in 8 motorized sectors (24 sources each)
  • Collimator apertures: 4, 8, 16 mm (plus blocked / home per sector)
  • Absolute dose rate ~3.86 Gy/min (fresh source inventory)
  • Integrated CBCT (70–120 kVp, 0.6 mm focal spot, 780 × 720 aSi detector)
  • IFMM infrared motion management (Polaris Vicra, adjustable 0.5–3 mm threshold)
  • Leksell GammaPlan treatment planning
  • Leksell Coordinate Frame G and Extend frameless mask workflows
  • End-to-end targeting accuracy typically <0.5 mm (framed and frameless per published commissioning data)

Clinical positioning

  • Brain metastases — single-fraction or fractionated, framed or frameless.
  • Meningioma, vestibular schwannoma, pituitary — benign skull-base tumors, now routinely fractionated.
  • AVM — single-fraction SRS.
  • Functional — trigeminal neuralgia, select functional indications.
  • Fractionated cranial radiotherapy — Icon's frameless capability brings fractionated stereotactic indications (multi-session over days / weeks) that were not practical on framed-only Perfexion.

Regulatory and operational reality

  • NRC / state radiation license for the Co-60 source inventory (see NRC licensing). Radiation Safety Officer, source exchange logistics, decay management.
  • QMP + commissioning per TG-standards and professional-society guidance; frameless workflow commissioning adds mask / CBCT / IFMM end-to-end QA beyond the traditional framed workflow.
  • Co-60 half-life 5.27 years — the source-inventory decay economics drive multi-year reload planning decisions.

Relationship to siblings

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