Portable gamma cameras: the real value of an additional view in the operating theatre

Abstract

It has been a long time since the preliminary portable gamma cameras (PGCs) were developed [1]. During the last decade some PGCs have become available for clinical practice, and can be used in open surgery or with laparoscopy, providing information that can be combined with that coming from conventional or laparoscopic gamma probes. Some of these PGCs are not designed specifically for radioguided surgery (Dilon 6800 gamma camera, a model optimized to perform breast-specific gamma imaging, or Cardiotom 3D mobile gamma camera, optimized to perform myocardial perfusion scintigraphy), but other models are focused on sentinel node (SN) procedures [2][3][4].In this issue of the journal, Vidal-Sicart et al.[5] report on the use of the Sentinella S102 (Oncovision) camera, which is a compact scintillation camera with a 50×50× 4 mm 3 CsI crystal optically coupled through a light guide to a flat panel type position-sensitive photomultiplier tube. This model is connected to a computer via USB, which processes the output signals and provides energy to the detector system. It has three interchangeable pin-hole collimators with apertures of diameter 1.0, 2.5 and 4 mm, and is mounted in a support to facilitate transport to the operating theatre. This support also incorporates a touchsensitive screen, which allows images to be viewed with ease throughout the surgical process. The intrinsic spatial resolution is approximately 2 mm and the energy resolution is 13% at 140 keV [6]. This PGC is provided with laser devices, which can help centre the image acquisitions, and it can also acquire images from dual isotopes. It is able to use a pointer (i.e. of iodine-125) to help localize hot spots seen on the screen.The main application of these devices is in SN procedures. SNs are widely used in breast cancer, melanoma and head and neck cancer, but in the last decade, their use has expanded to additional indications, with more sophistication and complexity in the technique, including indications in urology, gynaecology and gastroenterology. The addition of PGCs has improved the SN technique, particularly when intraoperative tracer injection is needed or in laparoscopic SN localization [7][8][9].In breast cancer, the main indication for a SN procedure worldwide, usually no laparoscopic technique and no intraoperative tracer injection is needed. The utility of the PGC in breast cancer remains only when no conventional gamma camera is available, and in particular in cases with extra-axillary drainage. In breast cancer, the use of PGCs in radioguided occult lesion localization combined with a conventional gamma probe has been described [7].In head and neck cancers the usefulness of the PGC seems more clear, because of the unpredictable lymphatic drainage and the possibility of comparing the preoperative image and the intraoperative image in order to ensure that no SN is missed. This is made possible by PGCs as they can give an overview of all radioactive hot spots within the surgical field. Prior SPECT images may be mandatory in head and nec...

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General Concepts on Radioguided Sentinel Lymph Node Biopsy: Preoperative Imaging, Intraoperative Gamma Probe Guidance, Intraoperative Imaging, Multimodality Imaging

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