Document approved Twente bubble_initial_r0 custom-field migration

twente-microbubblesim/README.md

@@ -146,9 +146,32 @@ The meanings and waveform values below are from Table I of Zorgdrager et al.
 | `raw_data` | `(1, 1, 8446, 96, 1)` | `float32` | Source-defined RF amplitude | Raw RF channel data |
 | `probe_geometry` | `(96, 3)` | `float32` | m | Element positions `(x, y, z)` |
 | `bubble_x`, `bubble_y`, `bubble_z` | `(N_bubbles,)` | `float32` | Source-defined | Ground-truth microbubble positions |
-| `bubble_R0`, `bubble_r0`, `bubble_p_dB` | `(N_bubbles,)` | `float32` | Source-defined / dB | Bubble simulation parameters |
+| `bubble_initial_r0`, `bubble_r0`, `bubble_p_db` | `(N_bubbles,)` | `float32` | Source-defined / dB | Bubble simulation parameters |
 | `pulse_waveform` | Source-dependent | Source-dependent | Source-defined | Simulated transmit waveform |
 
+### Custom Field Naming Migration
+
+The zea 0.1.6 migration uses the following lowercase custom-field names:
+
+| Original path | Migrated path |
+|---|---|
+| `custom/bubble_R0` | `custom/bubble_initial_r0` |
+| `custom/bubble_p_dB` | `custom/bubble_p_db` |
+| `custom/track_<i>_pulse_A` | `custom/track_<i>_pulse_a` for tracks 0 through 11 |
+
+In the [upstream simulator](https://github.com/POF-ultrasound/super-resolution-waveforms/blob/main/RF_simulator/microbubble-simulator/main.m),
+`R0` is the initial microbubble radius in metres, whereas `r0` is the distance
+from the bubble to the pressure sensor in metres. The distinct
+`custom/bubble_r0` field is therefore retained unchanged, not merged with
+`custom/bubble_initial_r0`. These definitions describe the public upstream
+implementation; the dataset uses a private derivative. Existing stored units
+and values are preserved, not inferred or rescaled during migration.
+
+All 14 renames preserve array values, shapes, dtypes, and existing attributes.
+Each renamed dataset records its original name in `source_custom_name`.
+During migration, files may use either naming scheme. The loading helper
+accepts both; new consumers should use the migrated paths.
+
 ## Subject Metadata
 
 This fully synthetic dataset contains no human or animal subjects, protected