In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: BACKGROUND : Renal dysfunction induced by iodinated contrast medium ( CM ) administration can minimize the benefit of the interventional procedure in patients undergoing renal angioplasty ( PTRA ) .
### Output Text:
BACKGROUND : Renal dysfunction induced by iodinated <span class="chemical">contrast medium</span> ( <span class="chemical">CM</span> ) administration can minimize the benefit of the interventional procedure in patients undergoing renal angioplasty ( PTRA ) . 