Intraoperative detection of radiolabeled compounds using a hand held gamma probe

Scintillation cameras in Nuclear Medicine allow external detection of cancerous lesions after administration of a specific radiopharmaceutical to the patient. In some particular cases the affinity of the tracer is sufficient to consider the use of an intraoperative probe which enables the surgeon to identify radioactive tissues. A radiopharmaceutical consists of a radioisotope bound to a carrier molecule. The radioactive emissions must represent certain criteria in terms of half-life and energy to be detected during an operation. In the field of intraoperative detection radionuclides like 99mTc, 111In, 125I and 131I fall into this category. Their energy, which ranges from some 10 to 364 keV, cannot be properly detected by a single type of detector. Two technologies have been developed to yield detectors which are handy and sufficiently sensitive: semiconductor CdTe or CdZnTe to detect low energies and scintillator CsI(Tl) for higher energies. Today the intraoperative detection has been evaluated in the case of several pathologies such as osteoid osteoma, colorectal cancer, neuroblastoma, reoperation of differentiated thyroid carcinoma and localization of sentinel node in breast cancer and cutaneous melanoma. Obviously, the results obtained are not comparable from one indication to the other. Nevertheless, the surgeons have noted a considerable advantage in using the intraoperative probe in the case of neuroblastoma and thyroid surgery, especially when the reoperation is difficult or the localizations are ectopic or unusual. As regards the sentinel node, this concept represents a major new opportunity in the field of intraoperative detection and the results actually reported in the literature demonstrate that, when it is detected, elective node excision renders the staging of the disease more accurate. In conclusion, intraoperative detection supplies the surgeon with additional knowledge to be used in correlation with the patientʹs medical history.