San Diego State University Traveling Subjects Diffusion MRI (SDSU-TS) Dataset

# San Diego State University Traveling Subjects Diffusion MRI (SDSU-TS) Dataset

The San Diego State University Traveling Subjects Diffusion MRI (SDSU-TS) dataset was designed to facilitate the harmonization of MRI data acquired across autism neuroimaging studies conducted at San Diego State University (SDSU). The dataset includes MRI scans from 9 healthy adult participants (aged 22-55 years) collected at 2 imaging sites: SDSU Imaging Center (SDSU-MRI) and Center for Functional MRI, UC San Diego (CFMRI). Each participant was scanned at least once at both sites, with rescan data available for 5 participants at SDSU-MRI and 6 participants at CFMRI. The average interval between scan sessions within a participant was 7 days (range: 1-19 days).

The scan protocols we collected reflect those used in SDSU autism MRI studies over the last 10-15 years and include the following:

- 5 diffusion-weighted (3 at CFMRI, 2 at SDSU-MRI)
- 3 T1-weighted (2 at CFMRI, 1 at SDSU-MRI)
- 2 T2-weighted (1 at each site)

Additionally, diffusion-weighted MRI protocols matching the publicly available Adolescent Brain Cognitive Development (ABCD) and Lifespan Human Connectome Project (HCP) studies were collected.

## Scan Protocols

The MRI protocols acquired at each site are shown below:

### SDSU-MRI (GE Discovery MR750 3T)

| Type | Sequence Name | b-values (s/mm²) [# directions] | TE | TR | Res (mm) |
|------|-------------------------|---------------------------------|-----|-----|----------------|
| dwi | 2shell93dir (hcp-style) | 1500 [47]; 3000 [46] | 85 | 4 | 1.83x1.83x1.8 |
| dwi | 4shell96dir (abcd-style) | 500 [6]; 1000 [15]; 2000 [15]; 3000 [60] | 85 | 4 | 1.83x1.83x1.8 |
| dwi | hcplifespan | 1500 [98]; 3000 [99] | 89 | 3.2 | 1.5x1.5x1.5 |
| T1w | mprage | n/a | 3 | 2.3 | 1x1x1 |
| T2w | t2 | n/a | 408 | 3.2 | 0.9x0.9x0.9 |

### CFMRI (Siemens Prisma 3T)

| Type | Sequence Name | b-values (s/mm²) [# directions] | TE | TR | Res (mm) |
|------|-------------------------|---------------------------------|-----|-----|----------------|
| dwi | 2shell93dir (hcp-style) | 1500 [47]; 3000 [46] | 89 | 4 | 1.71x1.71x1.7 |
| dwi | abcd | 500 [6]; 1000 [15]; 2000 [15]; 3000 [60] | 82 | 4.1 | 1.71x1.71x1.7 |
| dwi | 3shell45dir (legacy ms) | 500 [15]; 1500 [15]; 4000 [15] | 81 | 7 | 1.88x1.88x2.5 |
| dwi | 1shell61dir (legacy ss) | 1000 [61] | 82 | 8.5 | 1.88x1.88x2 |
| T1w | mprage | n/a | 4 | 8.8 | 0.8x0.8x0.8 |
| T1w | fspgr (legacy) | n/a | 3 | 8.1 | 1x1x1 |
| T2w | t2 | n/a | 61 | 3.2 | 0.8x0.8x0.8 |

**Note:**
- TE = Echo time (ms); TR = Repetition time (s); Res = spatial resolution.
- Reversed phase-encoding fieldmaps were acquired for all protocols.
- All data were acquired using a 32-channel head coil, except for the legacy sequences at CFMRI, which were acquired using an 8-channel head coil.

The unprocessed MRI data are provided along with anonymized participant demographic data.

The imaging data was converted to BIDS using ezBIDS ([https://brainlife.io/ezbids](https://brainlife.io/ezbids)) and custom scripts. All anatomical scans have been defaced using the Quickshear method in ezBIDS.

## Data Notes

Please note the following:

- The `1shell61dir` data in the `cfmri1` session of subjects `ts001`, `ts002`, and `ts004` were acquired with a variant spatial resolution (0.94x0.94mm instead of 1.875x1.875mm in-plane resolution).
- The `3shell45dir` data in the `cfmri1` session of subject `ts002` was acquired with a variant spatial resolution (2mm instead of 2.5mm slice thickness).
- The `1shell61dir` data in the `cfmri1` session of subject `ts010` was acquired with a variant TE (0.0843 instead of 0.0818s).
- The `sdsu1` session `hcplifespan` protocol for subjects `ts002` and `ts003` was not acquired with reversed phase-encoding directions (needed for distortion correction) and are not included in the dataset but are available upon request.

## Reference

Hau, J., Scarlett, S., & Arantes de Oliveira Campos, G. (2025). A traveling subjects dataset for diffusion MRI harmonization benchmarking [Poster presentation]. *International Society for Magnetic Resonance in Medicine Workshop on 40 Years of Diffusion: Past, Present & Future Perspectives*, Kyoto, Japan.