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GE Infinia

Family: GE Infinia · Modality: Nuclear Medicine / SPECT

GE's dual-head variable-angle gamma camera of the 2000s and early 2010s — the workhorse SPECT platform across community nuclear-medicine departments through that era. Infinia shipped in multiple configurations (Infinia, Infinia II, Infinia with 1" crystal for high-energy work) and was the upgrade base for the Infinia Hawkeye SPECT/CT — an Infinia can be field-retrofitted with the Hawkeye low-dose CT gantry without replacing the detector heads. Very large global installed base; a common legacy SPECT camera in the current secondary market.

Platform highlights

  • Dual-head variable-angle — detectors can be positioned at 180° (opposing, for whole-body planar imaging), 90° (L-shape, cardiac SPECT), or 76° (modified-L for cardiac-optimized positioning).
  • NaI(Tl) scintillator with two thickness options:
    • 3/8" (9.5 mm) — standard configuration for Tc-99m (140 keV) and lower-energy isotopes. Better intrinsic spatial resolution.
    • 1" (25.4 mm) — high-energy option for PET isotopes via coincidence imaging (now obsolete) or high-energy SPECT (In-111, Ga-67). Thicker crystal trades resolution for stopping power.
  • 59 PMTs per detector — 53 × 3" PMTs + 6 × 1.5" PMTs in a hexagonal close-packed arrangement.
  • NEMA useful field of view: 21.25" × 15.75" (54 × 40 cm).
  • Digital acquisition — one ADC per PMT, 30.3 MHz sampling, 10-bit word depth. Per-PMT digitization is the architectural step up from earlier analog-summing gamma cameras.
  • Energy range: 40–511 keV — supports the full clinical isotope range from low-energy Tl-201 through high-energy F-18 coincidence.
  • Upgradability — Infinia is field-upgradable to Infinia Hawkeye SPECT/CT by adding the Hawkeye low-dose CT gantry; the detector heads, control system, and workstation carry forward.

Collimator portfolio

  • LEHR (Low Energy High Resolution) — Tc-99m workhorse.
  • LEGP (Low Energy General Purpose) — higher sensitivity Tc-99m, lower resolution.
  • MEGP (Medium Energy General Purpose) — In-111, Ga-67 (170–300 keV).
  • HEGP (High Energy General Purpose) — I-131, Tc-99m breakthrough work.
  • Pinhole — thyroid, parathyroid, small-organ imaging.

Specs

  • Dual-head variable-angle SPECT
  • NaI(Tl) crystals — 3/8" or 1" thickness
  • 59 PMTs per detector (53 × 3" + 6 × 1.5")
  • NEMA UFOV 21.25" × 15.75"
  • 30.3 MHz ADC sampling per PMT, 10-bit depth
  • Energy range 40–511 keV
  • Collimators: LEHR, LEGP, MEGP, HEGP, Pinhole
  • 180° / 90° / 76° variable detector geometry

Clinical applications

  • Whole-body bone scans — Tc-99m MDP / HDP; metastatic workup, fracture evaluation.
  • Cardiac SPECT (MPI) — Tc-99m sestamibi / tetrofosmin, Tl-201.
  • Renal — Tc-99m MAG3, DTPA, DMSA.
  • Thyroid / parathyroid — Tc-99m pertechnetate, Tl-201, Tc-99m sestamibi.
  • Lung V/Q — Tc-99m MAA / DTPA.
  • Hepatobiliary, gastric emptying, GI bleeding — standard nuclear-medicine workflow.
  • I-131 imaging and therapy (HEGP collimator) — thyroid cancer post-therapy scans.

Market position (secondary / refurb)

  • Large global install base. Infinia is one of the most common legacy SPECT cameras in the secondary market.
  • Upgrade pathway — Infinia → Infinia Hawkeye (SPECT/CT retrofit) → Discovery NM family in new orders.
  • Service ecosystem — GE OEM service; multi-vendor service coverage mature.

Service reality

  • PMT gain drift is the single most important service-discipline item; monthly flood uniformity QC catches it.
  • Crystal hygroscopic damage — NaI is hygroscopic. Any seal breach → crystal clouding → permanent image-quality loss.
  • Collimator damage — drops deform lead septa; inspect after every collimator swap.
  • Center-of-rotation (COR) drift — SPECT reconstruction quality depends on 6-month COR calibration.
  • NRC / Agreement-State license required (NRC licensing).

Relationship to siblings and successors

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