Table 5.
Contribution of various sources of error to random uncertainty and to bias of the SRP-68-01 calibration factor for 131I in thyroid.
| Source of error | Standard deviationa for age group
|
|||||
|---|---|---|---|---|---|---|
| Newborn | 1 yr | 5 yr | 10 yr | 15 yr | Adult | |
| Random uncertainty | ||||||
| Variability of scale coefficient | ±0.05 | |||||
| Variability of thyroid mass | +0.03/−0.06 | +0.04/−0.04 | +0.05/−0.08 | +0.09/−0.05 | +0.08/−0.03 | +0.07/−0.03 |
| Statistical uncertainty | ±0.01 | ±0.01 | ±0.01 | ±0.01 | ±0.02 | ±0.02 |
| Overall uncertainty due to all sourcesb | 0.08 | 0.06 | 0.09 | 0.10 | 0.10 | 0.09 |
| Bias due to errors in geometry of measurement | ||||||
| Shift away from the neck | +0.31 | +0.32 | +0.31 | +0.27 | +0.23 | +0.18 |
| Vertical shift along the neck | +0.03c | +0.03 | +0.03 | −0.02 | −0.06 | −0.07 |
| Inclination in the vertical planed | +0.12 | +0.16 | +0.14 | +0.13 | +0.10 | +0.08 |
| Inclination in the horizontal plane | +0.05 | +0.09 | +0.04 | +0.03 | +0.04 | +0.05 |
| Overall bias due to all sources | 0.51 | 0.60 | 0.52 | 0.41 | 0.31 | 0.24 |
a
Relative to a mean of 1 for each source of error.
b
Maximal error due to variability of thyroid mass was used to calculate overall uncertainty.
c
Error was assumed to be the same as that for age 1 yr.
d
Error is slightly asymmetrical relative to the “normal” position of the detector. Value averaged over position in both directions is given.