Knowledge Hub · Co-57 Flood Source
A gamma camera's daily uniformity check needs a reference radiation field flat enough that the source contribution to the measurement is negligible. Co-57 at ≤ 0.9 % coefficient of variation, 272-day half-life, and a 122 keV emission that fits inside the Tc-99m clinical window — one sealed source covers a year of daily QA without depending on Tc-99m elution. NEMA NU-1-2007 sets the thresholds; the source supplies the ground truth.
Why this matters
Why Co-57
Tc-99m emits 140 keV gammas; Co-57 emits 122 keV. Close enough that the Tc-99m energy window catches the Co-57 emission, but Co-57 has a 272-day half-life vs Tc-99m's 6-hour half-life. One source covers months of daily QA without the cyclotron-generator dependency.
Based on: NEMA NU-1-2007 Performance Measurements of Gamma Cameras.
Read source ↗Uniformity numbers
Source non-uniformity adds directly to the camera's measured uniformity. At a CV of ≤ 0.9 %, the source itself contributes less than 1 % to the uniformity reading — the camera result reflects camera performance, not source imperfection. INU ≤ 3.6 % across the full useful field of view sits below the NEMA-set thresholds.
Based on: Source manufacturer spec; NEMA NU-1-2007 uniformity metrics.
Read source ↗AAPM QA cadence
AAPM Task Group 22 and the AAPM SPECT QA guidance (TG-150) frame the routine schedule: a daily visual / threshold-based flood uniformity check before patient imaging, plus a weekly quantitative NEMA NU-1 uniformity measurement to trend the camera over time. The same flood source covers both — different acquisition counts, same source on the head.
Based on: AAPM TG-22 / TG-150 SPECT QA guidance; NEMA NU-1-2007.
Read source ↗AERB licensing input
The AERB Safety Code for Nuclear Medicine Facility expects a documented gamma-camera QA programme with a calibrated flood source. The Co-57 source is one of the cited engineering controls — sealed-source licence, NIST-traceable certificate, and dated daily-QA logs form the inspection dossier.
Based on: AERB Safety Code for Nuclear Medicine Facility; ANSI 42.27 sealed-source standard.
Read source ↗Co-57 flood source at a glance
≤ 0.9 %
CV uniformity
Source contribution negligible
122 keV
Co-57 photon
Inside Tc-99m window
272 day
Half-life
~12 months of daily QA
NEMA
NU-1-2007
+ ANSI 42.27 sealed
Scope of this page
The flood source is the reference field for daily uniformity QA. It is not the camera-QA programme — the programme owns the acquisition recipe (matrix size, total counts, duration), the daily action threshold, the weekly NEMA NU-1 quantitative measurement, the trending log, and the AERB sealed-source licence record. The Co-57 source provides the engineered reference inside that programme.
Manufacturer product page and the AERB Safety Code that frames the gamma-camera QA programme.