---
license: apache-2.0
library_name: konfai
pipeline_tag: image-to-image
tags:
- medical-imaging
- registration
- deformable
- multimodal
- ct
- mri
- cbct
- konfai
---

# IMPACT-Reg — Multimodal Medical Image Registration

Robust **multimodal** (**MR / CT / CBCT**) deformable **registration** presets, built with
[**KonfAI**](https://github.com/vboussot/KonfAI). Alignment is driven by the **IMPACT** semantic
similarity metric — deep features from pretrained segmentation / foundation models (**MIND**,
**TotalSegmentator**, **MRSegmentator**) — so cross-modality pairs align while the deformation
stays smooth and physically plausible.

Each preset is a **self-contained KonfAI app**: on the **fixed** grid it produces the moving image
resampled onto the fixed image (**`MovedImage`**) and the **`DisplacementField`**. Presets can be
**ensembled** (their displacement fields are averaged into one transform).

## 🧩 Presets

| Preset | Pair | Engine | Description |
|:--|:--|:--|:--|
| `Generic_Rigid` | any | elastix | Rigid alignment (mutual information, multi-resolution) |
| `Generic_Rigid_BSpline` | any | elastix | Rigid, then B-spline deformable refinement |
| `MR_CT_HeadNeck` | MR/CT | elastix + IMPACT | MR/CT head & neck preset |
| `MR_CT_TS` | MR/CT | elastix + IMPACT | MR/CT with MIND + TotalSegmentator features |
| `MR_CT_MRSeg` | MR/CT | elastix + IMPACT | MR/CT with MIND + MRSegmentator features |
| `CBCT_CT_HeadNeck` | CBCT/CT | elastix + IMPACT | CBCT/CT head & neck preset |
| `CBCT_CT_TS` | CBCT/CT | elastix + IMPACT | CBCT/CT with TotalSegmentator features |
| `CBCT_CT_MRSeg` | CBCT/CT | elastix + IMPACT | CBCT/CT with MRSegmentator features |
| `ConvexAdam_Coarse` | any | itk-impact (native) | Global coarse coupled-convex init (IMPACT/MIND) |
| `ConvexAdam_Fine` | any | itk-impact (native) | Adam instance-optimisation (tileable; expects a pre-aligned start) |
| `ConvexAdam_Composite` | any | itk-impact (native) | Coarse + fine ConvexAdam in one app (IMPACT/MIND) |

Inputs: **Fixed**, **Moving**, and optional **FixedMask** / **MovingMask** (restrict the metric region).

## 🚀 Usage

```bash
pip install impact-reg-konfai
# Register a moving image onto a fixed image (ensemble several presets by listing them):
impact-reg-konfai register ConvexAdam_Composite -f fixed.nii.gz -m moving.nii.gz -o ./Output --gpu 0
```

- **Generic runner (single preset):** `konfai-apps infer VBoussot/ImpactReg:ConvexAdam_Composite -i fixed.nii.gz -i moving.nii.gz -o output/`
- **Interactive:** [**SlicerImpactReg**](https://github.com/vboussot/SlicerImpactReg) — a 3D Slicer extension driving these presets.

> The `ConvexAdam_*` presets depend on [`itk-impact`](https://pypi.org/project/itk-impact/); resolving the app installs it automatically (it reuses your existing PyTorch, CPU or GPU).

## ⚡ Performance & VRAM

`ConvexAdam` presets (native, GPU) benchmarked on an **NVIDIA RTX PRO 5000 (24 GB)** with a real
abdomen **MR→CT** pair, **222 × 226 × 124 @ 2 mm** (single pass, no TTA):

| Preset | Stages | Time / case | Peak VRAM |
|:--|:--|:--:|:--:|
| `ConvexAdam_Fine` | fine (150 Adam iters) | **≈ 0.5 s** | ~2.1 GB |
| `ConvexAdam_Coarse` | linear + coarse | **≈ 4.6 s** | ~2.1 GB |
| `ConvexAdam_Composite` | linear + coarse + fine | **≈ 5.1 s** | ~2.1 GB |

Per-stage breakdown: linear pre-align **≈ 4.2 s** (ITK affine, MI) · coarse **≈ 0.4 s** · fine **≈ 0.5 s**.
One-time TorchScript feature-model load **≈ 7 s** (amortised across a batch). Times scale with case size;
`--tta k` multiplies runtime. The `elastix + IMPACT` presets run through elastix and scale differently.

## 🔗 Links & Citation

- 🧠 **KonfAI:** [github.com/vboussot/KonfAI](https://github.com/vboussot/KonfAI)
- 📦 **PyPI:** [impact_reg_konfai](https://pypi.org/project/impact_reg_konfai/)
- 🩻 **Slicer:** [SlicerImpactReg](https://github.com/vboussot/SlicerImpactReg)
- 📄 **Paper:** KonfAI — [arXiv:2508.09823](https://arxiv.org/abs/2508.09823)
</content>
</invoke>