Development of Portable Digital Radiography System with a Device for Monitoring X-ray Source-Detector Angle and Its Application in Chest Imaging. - Tae-Hoon Kim; Dong-Woon Heo; Chang-Won Jeong; Jong-Hyun Ryu; Hong Young Jun; Seung-Jun Han; Taeuk Ha; Kwon-Ha Yoon (Sensors, 2017)