# 📐 L2 Spec — PET-CT Fusion (metabolism + anatomy) Mismatch-Only Spec
**ID:** `L2-156-001` · **Status:** ⊙ Testnet (genesis catalog)
**Parents:** ⬆ Principle [`L1-156`](/artifact/l1/L1-156)
> **🎯 Tolerance (ε):** expression
> **⚖ Difficulty score:** 0.55 · **Delta tier:** 5
> **⛓ On-chain block:** 41554245
---
## 1. Domain Ω
**Type:** `range`
| Parameter | Unit | Range |
|---|---|---|
| H | px | 128 |
| W | px | 128 |
| Z | — | 32 – 512 |
| Snr db | dB | 0.0 – 35.0 |
| Breathing motion | — | 0.0 – 10.0 |
| Temporal mismatch | — | 0.0 – 3600 |
| Registration error | — | 0.0 – 5.0 |
| Attenuation correction bias | — | 0.0 – 0.2 |
## 2. Tolerance (ε)
**Type:** `fn`
```
18.0 + 0.3 * SNR_dB - 1.5 * registration_error - 0.5 * breathing_motion - 10.0 * attenuation_correction_bias
```
## 3. Difficulty
| Property | Value |
|---|---|
| Difficulty score | 0.55 |
| Delta tier | 5 |
## 4. Fingerprint
`eb330aba37b81f9718f51f1328ada450bbe07afb2fada8e9d7482970f387301a`
## 5. On-chain Registration
- **Chain hash:** `0x8b1beeebe1cf8c81187c1b99018ae6a8eb0fb8c3876228f1a260bd1453f79056`
- **Chain tx hash:** `0x9b43206afcd87db1b654d6353bd380cc8cbad18ebce4c3f341743dc487b1809a`
- **Chain block:** `41554245`
---
## File Mapping
This bundle consists of: `L2-156-001.md`, `L2-156-001.json`.
| File | Role | How to regenerate |
|------|------|-------------------|
| `L2-156-001.md` | Source of truth — edit this | Human or LLM |
| `L2-156-001.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 `L2-156-001`._
_Edit it, regenerate the JSON, and submit at [/submit](/submit) to claim the artifact._