Which half of the roman empire became the byzantine empire?

The borders of the empire varied through cycles of decline and recovery. During the reign of Justinian I (r. 527-565), the empire reached its greatest extent, after reconquering much of the historically Roman western Mediterranean coast, including North Africa, Italy and Rome, which it held for two more centuries. The Byzantine-Sasanian War of 602-628 exhausted the empire's resources and during the Early Muslim conquests of the 7th century, lost its richest provinces, Egypt and Syria, to the Arab caliphate.[5] During the Macedonian dynasty (10th-11th centuries), the empire expanded again and experienced the two-century long Macedonian Renaissance, which came to an end with the loss of much of Asia Minor to the Seljuk Turks after the Battle of Manzikert in 1071. This battle opened the way for the Turks to settle in Anatolia.