Few radiologists would argue against the underlying principle of hybrid PET/CT. Cross-sectional CT produces superb spatial resolution for visualizing anatomy, but small cancerous lesion are often hidden in the details. FDG-PET identifies small metastatic lesions, but gives the clinician few clues about where they are located. In combination, the two modalities theoretically give radiologists the best of both worlds. At least that has been the sales pitch since GE Medical Systems and Siemens Medical introduced this new technology earlier this year. The study results presented by Dr. Hans Steinert, a professor of nuclear medicine at the University of Zurich in Switzerland, suggest that FDG-PET lives up to its early hype. Steinert described the first clinical results with hybrid whole-body PET/CT imaging for staging lung cancer in a session Thursday morning.
Twenty-nine lung cancer patients who were candidates for surgery were imaged with a GE Discovery LS hybrid device and also separately with multislice CT and FDG scanning. The CT and PET images were read separately. All lesions were correlated with surgery and histopathology.
It is essential, according to Steinert, to have exact anatomic localization for patients with metastatic disease. The hybrid procedure provided additional information about the localization of mediastinum and distant metastases. It also made it easier to distinguish between tumors and atelectasis, a determination that is important for radiotherapy planning.
Steinert was particularly impressed by the amount of information about tumor infiltration that PET/CT revealed.
"This was very surprising for us all," he said.
To demonstrate the power of the hybrid technique, Steinert displayed axial CT images and PET images of a patient with left-side non-small cell lung cancer. Localization was essential to determining whether surgery was advisable in this case, he said. Hybrid PET/CT revealed that a 6-mm metastasis was embedded in the margins of a single lymph node. The case was downstaged and the attending physicians decided against surgery.
"PET/CT is clearly superior to FDG-PET for the localization of metastatic pulmonary disease. In a very short time, PET/CT scanning has become the imaging modality of choice for our surgeons," Steinert said.
