 Gamma emission from the radioisotope 133Xe of xenon can be used to image the heart , lungs , and brain , for example , by means of single photon emission computed tomography . 133Xe has also been used to measure blood flow . 
 Gamma emission from the radioisotope 133Xe of xenon can be used to image the heart , lungs , and brain , for example , by means of single photon emission computed tomography . 133Xe <a href='been_done' title='1'><mark>has</mark></a> also been used to measure blood flow . 
Gamma emission from the radioisotope 133Xe of xenon can be used to image da heart , lungs , and brain , for example , by means of single photon emission computed tomography . 133Xe done also been used to measure blood flow .