Table 3.
Step | Activity | Description |
---|---|---|
1 | Data selection | Selection of raw SPECT acquisition and CTAC series |
2 | Scatter estimation | Extraction of the photopeak acquisition series (energy window A) and generation the lower scatter series (from energy window B) using the DEW technique |
3 | Series reconstruction | Non-corrected filtered backprojection reconstruction, for the purpose of generating the SPECT matrix for CTAC resampling |
4 | Series registration | Resampling of CTAC to the SPECT matrix |
5 | Attenuation map | Conversion of resampled CTAC into an attenuation map using 208 keV narrow beam geometry settings (no filtering) |
6 | Series reconstructiona | Iterative reconstruction (OSEM Flash 3D, 4 iterations, 8 subsets) with AC and SC (no zoom, no filtering) |
7 | Series arithmetic | Multiplication (rescaling) of the raw SPECT acquisition series by 0.01 to avoid pixel saturation (>65,535 counts/pixel) during the next step. The Use Scale Factor option was enabled in this activityc |
8 | Series arithmetic | Sum of the rescaled raw SPECT acquisition series frames (96 × 4 energy windows = 384 frames) into one static image. The displayed count sum of this static image times 100 is the wide-spectrum counts (CWo) |
9 | Series arithmeticb | Multiplication of the reconstructed SPECT series by a coefficient (K) converting counts to dead-time corrected quantitative uptake data. The resulting series is saved as QSPECT |
aFor the calibration studies, the photopeak and scatter series were scaled down before reconstruction (by a factor up to 100) in order to avoid voxel saturation (>65,535 counts/voxel) in the reconstructed SPECT dataset.
bThis step was not performed for the calibration studies.
cThis allows fractions of counts (e.g. 2 decimal digits) to be preserved in subsequent step.