Table 4.
Calibration factor and dead-time constant (± SE) derived from SPECT data
| Phantom | Low activity | Full activity range | Calibration factor (cps/MBq) | Dead-time constant (μs) | |||||
|---|---|---|---|---|---|---|---|---|---|
| No. of acquisitions Activity range (MBq) Photopeak count rate range (cps) Wide-spectrum count rate range (cps) |
Method A | Method B Photopeak |
Method B Wide-spectrum |
Method A Photopeak |
Method B Photopeak |
Method A Wide-spectrum |
Method B Wide-spectrum |
||
| Air-3D |
7 32-330 327-3154 1342-11,975 |
27 32-10,704 327-88,762 1342-347,060 |
9.62 ± 0.04 | 9.70 ± 0.03 | 9.67 ± 0.03 | 2.07 ± 0.01 | 2.15 ± 0.03 | 0.531 ± 0.003 | 0.544 ± 0.008 |
| CTDI-10 |
4 126-510 800-3423 5229-20,267 |
19 13-9646 93-60,750 665-354,256 |
9.91 ± 0.06 | 9.72 ± 0.03 | 9.70 ± 0.03 | 3.18 ± 0.02 | 2.93 ± 0.04 | 0.546 ± 0.005 | 0.499 ± 0.008 |
| CTDI-16 |
5 157-634 693-3302 5523-22,333 |
16 16-80,94 83-41,651 694-264,231 |
9.98 ± 0.09 | 9.84 ± 0.05 | 9.85 ± 0.06 | 3.77 ± 0.06 | 3.28 ± 0.12 | 0.603 ± 0.010 | 0.528 ± 0.024 |
| CTDI-32 |
4 293-1404 522-2364 5226-23,734 |
20 21-13,708 50-53,746 513-339,364 |
10.66 ± 0.09 | 10.19 ± 0.05 | 10.23 ± 0.04 | 4.47 ± 0.08 | 3.71 ± 0.07 | 0.705 ± 0.011 | 0.594 ± 0.012 |
| Jaszczak |
5 120-526 624-2335 4972-17,052 |
26 44-12,480 307-49,376 2650-348,334 |
9.50 ± 0.05 | 9.40 ± 0.05 | 9.46 ± 0.04 | 4.07 ± 0.04 | 4.04 ± 0.09 | 0.572 ± 0.005 | 0.565 ± 0.010 |
Method A refers to obtaining the calibration factor at low activity, i.e. a subset of the full activity range (Eq. 1), then obtaining the dead-time constant over the full activity range by fitting the data to the paralysable model (Eq. 3). Method B refers deriving both the calibration factor and the dead-time constant through a single curve fit using data from the full activity range (Eq. 3). The acquisition count rate from either the photopeak or the wide spectrum (6W, 18–680 keV, Table 2) was considered for dead-time constant determination