SPECT心肌灌注显像多用（ ）和（ ）两种显像剂。
参考答案：201Tl和99mTc-MIBI
圆的周长是6.28米，从该圆上取一个半圆的周长是______．
Peter will ______ as managing director when Bill retires.
A．take off
B．take over
C．take to
D．take up
