1773
X-ray imaging was found to be a suitable method for the identification of the embedded safety features up to 15 mm in depth .
 X-ray imaging, be, safety, mm
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 X-ray imaging, be, safety, mm