# 📐 L2 Spec — SPECT-CT Fusion Mismatch-Only Spec
**ID:** `L2-158-001` · **Status:** ⊙ Testnet (genesis catalog)
**Parents:** ⬆ Principle [`L1-158`](/artifact/l1/L1-158)
> **🎯 Tolerance (ε):** expression
> **⚖ Difficulty score:** 0.55 · **Delta tier:** 5
> **⛓ On-chain block:** 41554245
---
## 1. Domain Ω
**Type:** `range`
| Parameter | Unit | Range |
|---|---|---|
| H | px | 64 |
| W | px | 64 |
| Z | — | 16 – 256 |
| Snr db | dB | 0.0 – 35.0 |
| Patient motion | — | 0.0 – 10.0 |
| Low count spect | — | 0.0 – 0.5 |
| Registration error | — | 0.0 – 5.0 |
| Attenuation correction bias | — | 0.0 – 0.3 |
## 2. Tolerance (ε)
**Type:** `fn`
```
15.0 + 0.3 * SNR_dB - 1.5 * registration_error - 10.0 * attenuation_correction_bias - 6.0 * low_count_SPECT
```
## 3. Difficulty
| Property | Value |
|---|---|
| Difficulty score | 0.55 |
| Delta tier | 5 |
## 4. Fingerprint
`ad03f6aacbb7fd9d3bfcfbdff105857bc8c9aed74f549c8691b94f3361c68bc1`
## 5. On-chain Registration
- **Chain hash:** `0x87175406e9914cc076348b541a3cb2d9c9def44eb9182c45df641ce7487e26e6`
- **Chain tx hash:** `0x08b8efae448915950cf92df172f09c945d5cfb330e7bc79035b1ff78400b6027`
- **Chain block:** `41554245`
---
## File Mapping
This bundle consists of: `L2-158-001.md`, `L2-158-001.json`.
| File | Role | How to regenerate |
|------|------|-------------------|
| `L2-158-001.md` | Source of truth — edit this | Human or LLM |
| `L2-158-001.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 `L2-158-001`._
_Edit it, regenerate the JSON, and submit at [/submit](/submit) to claim the artifact._