ABSTRACTOsteosarcoma (Osteogenic Sarcoma) is a type of malignancy that arises in the bone. Bone costae has a special shape that surrounded (around the thoracic cavity) that requires special MSCT examination techniques, especially examination in pediatric patients. Costae located in the anterior section is higher in the lateral part than the medial part, the posteriorly located costae is higher in the medial than in the lateral part. The MSCT Thorax examination for the osteosarcoma costae case requires a special reconstruction technique that reconstructs MSCT 3D with ss- VRT. This study aims to investigate MSCT 3D thoracic examination techniques in patients with sosteosarcoma costae, and to find out the reasons for the use of 3D techniques on 3D Thoracic MSCT examination in patients with osteosarcoma costae in Radiology Department RSUD dr. Soehadi Prijonegoro Sragen.The type of research used in the preparation of this thesis is a type of qualitative research with case study approach. The subjects used in this research are 1 patient of MSCT Thorax 3D child in Radiology Department of RSUD dr, Soehadi Prijonegoro Sragen with case of osteosarcoma at costae, 1 radiologist, 3 radiographer and 1 sending doctor. Using data analysis in an interactive way model.MSCT Thorax Examination Techniques 3D children with cases of osteosarcoma costae in Radiology department of RSUD dr. Soehadi Prijonegoro Sragen done without using contrast media and scanning starting from supra clavicula up to supra renalis with slice thickness 2 mm, FOV 249 mm, 120kV, 225mA and 0,8S. The use of 3D reconstruction techniques is done, so that the picture of the costae structure can be projected intact, uncut, more clear and detailed.