| --- |
| license: cc-by-4.0 |
| tags: |
| - mri |
| - qsm |
| - quantitative-susceptibility-mapping |
| - neuroimaging |
| pretty_name: QSMbly example data |
| --- |
| |
| # QSMbly example data |
|
|
| One in-vivo subject, used as the "Load example data" dataset in |
| [QSMbly](https://qsmbly.neurodesk.org/) and fetched by the browser at runtime. |
|
|
| A single 5-echo 3D gradient-echo acquisition at 1 mm isotropic, acquired on a Siemens |
| MAGNETOM Prisma Fit. Magnitude and phase are split one file per echo, since QSMbly's |
| loader reads 3D volumes and derives the echo count from the file list. |
|
|
| | | | |
| | --- | --- | |
| | Matrix | 184 × 256 × 128, 1 mm isotropic | |
| | Echoes | 5 — TE 5 / 11 / 17 / 23 / 29 ms | |
| | TR / flip | 35 ms / 15° | |
| | Sequence | `gre_bridge_1mm_psn_adapt` (product GRE, GRAPPA R=2) | |
| | Scanner | MAGNETOM Prisma Fit (XR VA30A) | |
| | Phase | radians, wrapped | |
|
|
| ## Field strength |
|
|
| `MagneticFieldStrength` is **2.8946 T**, the accurate field derived from the scanner's |
| carrier frequency (`ImagingFrequency` 123.243444 MHz ÷ 42.576384 MHz/T), not the nominal |
| 3.0 T printed on the magnet. QSM scales ppm by this value, so the accurate one is the |
| correct one to use. |
|
|
| ## Echo times |
|
|
| Recovered from the exam-card PDFs shipped with the acquisition and, for the Pulseq |
| consensus sequence in the wider study, from |
| [HarmonizedMRI/megre_label](https://github.com/HarmonizedMRI/megre_label). They are not |
| the DICOM sidecar values, which carry placeholder timings for some protocols. |
|
|
| ## Provenance |
|
|
| Packed from the 2026-08-20 QSM harmonization acquisition (MGH bays 4/5) — one subject |
| scanned on two Siemens 3T scanners under four protocols × 3 runs. The full study is on |
| OSF at [osf.io/gkemr](https://osf.io/gkemr/); this repo holds the `prisma-bridge-run1` |
| acquisition only, re-split into per-echo files. |
|
|
| The same acquisition is available to QSMxT users via `qsmxt example`. |
|
|
