# 📐 L2 Spec — US-MRI Fusion (biopsy guidance / cardiac) Mismatch-Only Spec
**ID:** `L2-159-001` · **Status:** ⊙ Testnet (genesis catalog)
**Parents:** ⬆ Principle [`L1-159`](/artifact/l1/L1-159)
> **🎯 Tolerance (ε):** expression
> **⚖ Difficulty score:** 0.55 · **Delta tier:** 5
> **⛓ On-chain block:** 41554245
---
## 1. Domain Ω
**Type:** `range`
| Parameter | Unit | Range |
|---|---|---|
| Fps | — | 1 – 60 |
| H us | µs | 128 – 2048 |
| W us | µs | 128 – 2048 |
| Z mri | — | 32 – 512 |
| Snr db | dB | 0.0 – 35.0 |
| Patient motion | — | 0.0 – 0.5 |
| Non rigid tissue | — | 0.0 – 0.5 |
| Acoustic shadowing | — | 0.0 – 0.5 |
| Real time registration error | — | 0.0 – 5.0 |
## 2. Tolerance (ε)
**Type:** `fn`
```
12.0 + 0.3 * SNR_dB - 1.5 * real_time_registration_error - 8.0 * non_rigid_tissue - 6.0 * acoustic_shadowing
```
## 3. Difficulty
| Property | Value |
|---|---|
| Difficulty score | 0.55 |
| Delta tier | 5 |
## 4. Fingerprint
`b8efb992c7988b0f3c349241433504aa7ae13d5a78dc4b603809142513d2c92f`
## 5. On-chain Registration
- **Chain hash:** `0x64a3fb80e50fa3cc930e40c9e382c4b43c80da3fc376a512be07247af97c354c`
- **Chain tx hash:** `0xf7bf87fb16ee0247f8a4a1345e7872a2093da1bc19f51abee70d9b06b33e46ea`
- **Chain block:** `41554245`
---
## File Mapping
This bundle consists of: `L2-159-001.md`, `L2-159-001.json`.
| File | Role | How to regenerate |
|------|------|-------------------|
| `L2-159-001.md` | Source of truth — edit this | Human or LLM |
| `L2-159-001.json` | Structured metadata for the registry | LLM regenerates from the sections above |
**Prompt for your LLM after editing this Markdown:**
> Read the attached Markdown. Regenerate the sibling `.json` so every field matches.
> Preserve the schema documented in the rows above.
> Output each file in its own fenced code block tagged with the filename.
> Output only the JSON object.
_This Markdown was auto-synthesized from the catalog row for `L2-159-001`._
_Edit it, regenerate the JSON, and submit at [/submit](/submit) to claim the artifact._