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MRI Patient Table

The non-magnetic, motorized patient table that translates the patient into the magnet bore for imaging — engineered for position-precision (slice-position consistency across a study session), patient comfort (long acquisitions), and compatibility with the integrated / surface / Tim-platform coil ecosystem. Distinct from CT and linac patient tables in two ways: (1) construction must be entirely non-magnetic within the magnet's fringe field — no steel components, no ferrous bearings, brass / aluminum / plastic / non-magnetic stainless throughout; and (2) table-embedded posterior coils are a routine architectural feature on current-generation systems (the spine coil and posterior body coil are integrated into the table top, not handled separately).

The table position-encoder drives slice-position consistency across multi-acquisition study sessions — a patient imaged at multiple time points with consistent position has comparable images for radiologist comparison. Table-encoder drift produces slice-position inconsistency that radiologists notice as "the slice doesn't quite line up with the prior study."

For interventional MRI (breast MRI biopsies, MR-guided focused ultrasound, MR-linac patient setup), table positioning becomes a delivery-precision concern alongside imaging-consistency.

Fits

MRI patient tables are platform-specific. Every clinical MRI has an integrated patient table; representative platforms include the entire current-generation MRI installed base across GE / Siemens / Philips / Canon.

Distinctive technology

  • Non-magnetic construction — the entire table assembly is fringe-field-tolerant. Materials selection is more constrained than CT or linac couches.
  • Embedded posterior coils — table-top integrated spine coil + posterior-body coil on current-generation BioMatrix (Siemens), Tim 4G (Siemens earlier), AIR (GE), dStream (Philips) platforms.
  • Position-encoder + drive motor for in-out translation — typically belt-drive or screw-drive, all non-magnetic.
  • Quick-release patient straps + accessory mounting for surface coils, head-coil docking, immobilization.
  • Patient-comfort padding — replaceable foam / vinyl assemblies.
  • Integrated patient-call button + light — accessory for patient communication during long acquisitions.

Failure modes

  • Drive-motor wear — the in-out translation motor wears with cumulative-cycle count. Manifests as noisy or sticky table motion.
  • Position-encoder drift — slice-position consistency drift outside calibration tolerance. See patient-table positioning encoder drift for the cross-modality pattern.
  • Table-coil interface wear — connectors and cabling between the table-embedded coils and the system-side electronics. Coil-element issues can manifest as table-side wiring problems even when the coil itself is intact.
  • Patient-pad wear — routine consumable replacement.
  • Mechanical-stop / limit-switch issues — the table's end-of-travel safety system can develop intermittent faults that produce annoying false-alarms.

Diagnosis

  • Daily QA slice-position acceptance — the canonical detection method.
  • Service-log table-position-event review.
  • Drive-motor current-draw trending if instrumented.
  • Visual inspection of pads, connectors, and patient-call accessories.

Replacement path

  • Pad-level replacement — routine consumable swap.
  • Motor / encoder swap for component-level failures.
  • Table-embedded coil service for posterior coil issues — see AIR Coil / dStream / Tim 4G for the coil-side details.
  • Full table replacement rare; capital-grade event tied to system-level refurbishment.

Field notes

  • Table-embedded coil inheritance matters at refurb — a refurb MRI without table-embedded posterior coils is a meaningful capital delta vs new.
  • Magnet-relocation events require full table re-acceptance + position calibration at the destination site.
  • MR-linac couch + MRI table integration (Elekta Unity, ViewRay MRIdian) is platform-specific — the patient setup and treatment delivery happens on a couch with combined MRI-position + linac-treatment-position requirements.

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