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: Among the 5 patients with white matter abnormalities , 4 patients ( 80 . 0 % ) showed higher than normal ADC values on initial MR images , and all showed complete resolution on follow - up images .
### Output Text:
Among the 5 patients with white matter abnormalities , 4 patients ( 80 . 0 % ) showed higher than normal ADC values on initial MR images , and all showed complete resolution on follow - up images . 