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Table 2 Uncertainty budget for the dosimetry procedure

From: Practical kidney dosimetry in peptide receptor radionuclide therapy using [177Lu]Lu-DOTATOC and [177Lu]Lu-DOTATATE with focus on uncertainty estimates

Section in paper Source Uncertainty estimate
Dose calibrator calibration and activity measurement Calibration sourcea 3%
Calibration of dose calibratorsa 1%
Dose calibrator stability 1%
Quantitative SPECT (QSPECT) Scanner calibration 2% + 1%
Reproduction of activity 6%
Scanner stability 2%
Deadtime correctionb 1%
Kidney delineation and partial volume correction Kidney delineation 3%
Partial volume correction 7%
Time-activity curve and absorbed dose Single exponential model 1% + 1%
Fitting uncertainty Individual value from fit (normally 1–10%)
Assumption of equal effective half-lifec 12%
1-SPECT AUC calculationc Individual value dependent on 3-SPECT fit
Dose factor 1% + 1%
  Total (3-SPECT—example)d 13%e
  Total (1-SPECT—example)d 19%e
  1. aFor calculations of specific absorbed dose (Gy/GBq) this error cancels out, as it enters in both dose (Gy) measured through scanner calibration and activity (GBq) measured through dose calibrator calibration
  2. bIf the deadtime correction factor was applied
  3. cOnly relevant for 1-SPECT fractions
  4. dTaking 6% standard uncertainty on AUC as in Fig. 6b. 1-SPECT example: Assuming effective half-life of 2.2 d, scan performed 24 h after injection and 9% standard uncertainty on λ (see Eq. (4))
  5. eThe stated total uncertainty was obtained by adding the uncertainty components in quadrature and is thus valid for independent error sources. The value was rounded up