gms | German Medical Science

Molecular imaging with PET and SPECT enables the detection of neoplastic tissue with a high lesion-to-background contrast. However, detailed information on morphology is usually not provided by these techniques. The molecular and morphologic information can be combined by software-based retrospective registration of PET and SPECT data with those from CT or MRI. Furthermore, hybrid scanners combining a PET or SPECT camera with a CT scanner within one gantry offer the opportunity to exactly correlate molecular and morphological information in one imaging session. Since its introduction in 1998, PET/CT has gained acceptance as a routine diagnostic tool. Besides F-18-fluorodeoxyglucose, which enables the visualization of tumour energy metabolism, more specific PET tracers have been developed in the recent past. For example, F-18-choline is able to visualize prostate cancer and its metastases, F-18-fluoride can be used as an agent for the detection of osseous metastases. Especially for these more specific tracers the disadvantages arising from the lack of anatomic background can be compensated by hybrid scanning. Recently, also hybrid scanners combining SPECT and CT have become available. This opens a wide field of applications also in oncology: In bone scintigraphy, the differentiation between degenerative processes and bone metastases is possible with SPECT/ CT in one imaging session. With SPECT/ CT, an improvement in diagnostic accuracy has also been shown for the tumour scintigraphies, e.g., using In-111 pentetreotide in neuroendocrine carcinomas, I-123-MIBG in neuroblastoma, I-131 in thyroid cancer, or Tc-99m-MIBI in parathyroid tumours. A further interesting application for SPECT/CT is sentinel lymph node scintigraphy where it helps to exactly localize the first lymph node draining a tumour. In summary, hybrid imaging considerably improves the diagnostic accuracy of molecular imaging and may also increase cost efficiency by abbreviating the diagnostic process.