Xenon-127, a comparison with xenon-133 for ventilation studies.

In 133Xe ventilation studies the 81-keV gamma photon emitted is a major disadvantage for imaging. Using a lung model with the same attenuation coefficient as inflated lung, we compared 133Xe with 127Xe to determine the smallest "lesion" that could be imaged at different places within the lung. With the "lung lesion" directly against the collimator, the lesion had to be 10 ml in volume in order to be seen with 127Xe, but with 133Xe "lesion" had to be 30 ml. Xenon-127 gave better resolution, no matter where the lesion was placed within the lung. Xenon-127 was not better than 133Xe in resolving a lead bar phantom. When 133Xe was used with 99mTc in a model of pulmonary embolism, a "ventilation defect" was apparent even though the distribution of xenon was even throughout the model. This artifact was not seen when the 127Xe model was imaged.