ROC is an abbreviation for receiver operating characteristic; LBH is an abbreviation for limb-bud and heart; and AUC is an abbreviation for area under the curve. These are all components of radiology reports. Limb-bud and heart (LBH) refers to a radiologist's assessment of whether there is evidence of blood flow to a fetus. This information is important in determining risk to the baby. MRI can show blood flow to the fetus if it is needed. Ultrasound cannot show blood flow but it can reveal other signs of life in the fetus such as organ movement. A radiologist reads images of the fetus to look for signs of life, such as heart activity or blood flow. If no signs of life are seen, the fetus will not survive beyond birth. However, some organs may be developed enough for transplant into an infant. A fetus that is aborted prior to cardiac activity being detected cannot be diagnosed as live or dead based on autopsy results. The only way to be sure if a fetus is alive is by measuring its heart rate with ultrasound or Doppler techniques during pregnancy.