FIGURE 7.  Acquisition of position profile with LSO-APD detector outside 7-T magnet (A), inside magnet (B), and during MRI with spin-echo sequence (C). Corresponding analog signals after 200-ns shaping are shown below for detector in magnet (B) and while applying spin-echo sequence (C). Signal baseline shows slightly increased noise level (oscilloscope pictures) when spin-echo sequence is applied. Square signal in oscilloscope diagram shows trigger that initiates sampling for analog–digital conversion.