1994
Due to the expense involved in AM , non-destructive tools are especially useful to analyze parts without destroying them : the most widely used are X-ray techniques such as 2D digital radiography and 3D micro-computed tomography .
 manufacturing process: AM; machine or equipment: tools; process characterization: X-ray; material: as; concept or principle: 2D; enabling technology: radiography; concept or principle: 3D
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: 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:
 manufacturing process: AM; machine or equipment: tools; process characterization: X-ray; material: as; concept or principle: 2D; enabling technology: radiography; concept or principle: 3D