---
tags:
- text-embeddings
- retrieval
- radiology
- chest
- qwen
base_model:
- Qwen/Qwen3-Embedding-4B
library_name: transformers
pipeline_tag: feature-extraction
---

# chest2vec_4B

Chest-radiology **text embedding** model: [`Qwen/Qwen3-Embedding-4B`](https://huggingface.co/Qwen/Qwen3-Embedding-4B)
contrastively LoRA-adapted for chest CT / CXR report retrieval. Embedding = left-padding-aware
last-token (EOS) pooling + L2-norm. **Embedding dim: 2560.**

## Self-contained `AutoModel`

The LoRA adapter is **merged into the weights** (`model.safetensors`) and the tokenizer is bundled,
so loading needs **no `chest2vec` package and no download of the base Qwen3-Embedding weights**:

```python
from transformers import AutoModel, AutoTokenizer
model = AutoModel.from_pretrained("chest2vec/chest2vec_4B", trust_remote_code=True).eval()
tok   = AutoTokenizer.from_pretrained("chest2vec/chest2vec_4B", trust_remote_code=True)

docs = ["Bibasilar atelectasis with small bilateral pleural effusions. Cardiomegaly."]
doc_emb = model.embed_texts(docs, tokenizer=tok)                      # [N, 2560], L2-normalized

# instruction-conditioned query
q_emb = model.embed_instruction_query(
    "Retrieve the chest CT report that is similar to the given report.",
    ["pleural effusion and cardiomegaly"], tokenizer=tok)
vals, idx = model.cosine_topk(q_emb, doc_emb, k=5)
```

## Matryoshka embeddings

Matryoshka (MRL)-trained — truncate to **512** or **256** dims (keep first *N* dims, re-normalize):

```python
emb512 = model.embed_texts(docs, tokenizer=tok, dim=512)
emb256 = model.embed_texts(docs, tokenizer=tok, dim=256)
```

Recommended dims: **2560 (full) · 512 · 256** (`config.matryoshka_dims`). Use the same `dim` for query and corpus.

## Recommended instructions

Instruction-conditioned (`Instruct: {instruction}\nQuery: {report}`). Apply to the **query** side;
embed the corpus without an instruction. Trained on chest **CT and CXR** across these families:

**Retrieval** — `Retrieve the chest CT report that is similar to the given report.` ·
`Retrieve the CXR report that is similar to the given report.` ·
`Retrieve the CXR report that is similar to the given report with prior reference omitted.`

**Summarization** — `Summarize the following chest CT report` · `Summarize the following CXR report` · `Summarize the given report.`

**Entity extraction (leaf)** — `Given the following chest CT report, extract the presence/absence of entities` · `Given the following CXR report, extract the presence/absence of entities`

**Entity extraction (upper/coarse)** — `Given the following chest CT report, extract the presence/absence of upper-level entities` · `Given the following CXR report, extract the presence/absence of upper class entities`

**Anatomy-specific** — `From the following chest {CT report | X-ray report}, extract and return only the findings related to {REGION}, ignoring all information about other structures.`
- CT regions: lungs · airways and trachea · pleura · mediastinum and hilum · cardiovascular system · chest wall · bones and spine · upper abdomen · lower neck
- CXR regions: lungs and airways · pleura · hila and mediastinum · cardiovascular system · musculoskeletal structures and chest wall · tubes, catheters, and support devices · abdomen

## Details

- **Base:** Qwen/Qwen3-Embedding-4B (Apache-2.0) — architecture rebuilt from the bundled config; merged weights loaded from this repo. Default attention `sdpa` (use `flash_attention_2` on Ampere+ for speed).
- Merged weights reproduce the original adapter-based embeddings to **cosine ≥ 0.999**.