references

Author: ChristianHinge

README.md

@@ -43,7 +43,7 @@ Note that no PET reconstruction experience is needed to participate in the chall
 | Guide | Description |
 |-------|-------------|
 | [Rules](docs/rules.md) | All rules for participating teams including training data policy, and pretraining policy |
-| [PET Background](docs/pet-background.md) | PET physics and attenuation correction — start here if you're new to PET |
+| [Data Background](docs/data-background.md) | Details dat acquisition, preprocessing, and alignment of modalities |
 | [Reconstruction Pipeline](docs/reconstruction.md) | How the pseudo-CT is turned into an AC-PET image; how to run it locally |
 | [Submission Guide](docs/submission-guide.md) | Validation, dry-run, and final submission phases explained |
 | [Docker Packaging](docs/docker-packaging.md) | How to containerize your model, with baseline as a worked example |

docs/data-background.md

@@ -28,7 +28,7 @@ The four input modalities span a spectrum from *well-aligned but low-quality* to
 A 2D sagittal scout X-ray acquired roughly 2 minutes before the CT. It is the most temporally and spatially aligned feature, but has very limited anatomical detail — it is a single 2D projection with coarse resolution. The topogram and CT share the same patient position and scanner table.
 
 ### NAC-PET (`nacpet.nii.gz`)
-The non-attenuation-corrected PET, reconstructed from the **50–70 minute** window of the dynamic scan. This is the same scanner as the CT, so patient positioning is roughly preserved, but ~50 minutes elapsed between the CT and the PET window. Over this time, gross body position is stable, but peripheral structures (arms, fingers, legs) may have shifted a bit. NAC-PET encodes useful soft-tissue contrast and body shape, and has the same matrix and affine as the ground-truth CT.
+The non-attenuation-corrected PET, reconstructed from the **50–70 minute** window of the dynamic scan. This is the same scanner as the CT, so patient positioning is roughly preserved, but ~50 minutes elapsed between the CT and the PET window. Over this time, gross body position is stable, but peripheral structures (arms, fingers, legs) may have shifted a bit. NAC-PET encodes useful soft-tissue contrast and body shape, and has the same matrix and affine as the ground-truth CT. 
 
 ### MRI (`mri_chunk_*` / `mri_combined_*`)
 Whole-body DIXON MRI acquired on a **separate scanner** the same day as the PET/CT (for 95/99 participants; 4 were scanned 9–89 days later). The MRI provides excellent soft-tissue contrast and anatomical detail, but it is not inherently aligned to PET/CT space. The DIXON MRI sequence used is designed specifically to capture anatomical informing relevant for attenuation correction. Patients were placed head first supine with arms down the side in both PET/CT and MRI, but the use of coils, different beds and raisable head rests makes the MRI-to-PET/CT alignment poor. A rigid translation (no rotation) was applied to bring the MRI into approximate PET/CT alignment. Whether to incorporate additional registration as a preprocessing step is left to the participant.