This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
[{'content': 'CPD is best assessed by \nSelect and explain. \nA. CT scan, B. Ultrasound, C. Radio pelvimetry, D. Pelvic assessment', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Methods of assesment of Pelvis\xa0\n\nClinically\nImaging studies\n\nClinical Pelvimetry :\n\nDone manually\nCan be done beyond 37th week, better done after onset of labour\nFollowing are to be observed\xa0\n\n\nSacrum\xa0\nSacrosciatic notch\nIscial spines\xa0\nSide walls\nPubic arch\nPubic angle\nTransverse diameter of outlet\n\nImaging :\n\nX-ray pelvimetry\xa0\nUSG\nCT\xa0\nMRI\n\nX-ray pelvimetry :\xa0\n\nLimited value in diagnosis\nCan only assess size and shape of pelvis\xa0\nUseful in cases with pelvic fractures\xa0\nDisadvantage : Radiation exposure to both mother and foetus (885 milirad)\nErect lateral view\xa0\n\nCT\xa0\n\nEasier to perform\nRadiation exposure(45-425milirad)\nMore accurate\n\nMRI\n\nMore accurate to assess bony pelvis\nAssess pelvic capacity in different planes\nAssess foetal size and head volume, pelvic soft tissues\nNo radiation risk\nExpensive,limited availability, more time taking\n\nUSG :\xa0\n\nAccurately measures the biparietal diameter', 'role': 'assistant'}]