All of the following investigations use non-ionizing radiation, except:

Radiography is the procedure in which film is exposed as ionizing radiation passes through the patient and shows internal body structures in profile. Ultrasonography, thermography and MRI use non ionizing radiation. Ref: Essentials of Human Disease By Leonard V C roley, Pages 8-11; Grainger and Allison's Diagnostic Radiology, 4th Edition, Page 606