Evaluation of a Novel Hand Held Gamma Camera for Intra-Operative Single Photon Emission Computed Tomography

Cancer when detected at an early stage, before it has spread, can often be treated successfully by surgery or local irradiation. However, when cancer is detected only after it has metastasized, treatments are much less successful. The lymphatic system is a primary path by which malignant cells can travel to other organs in the body. Thus determination of the presence or absence of malignant cells in lymph nodes to which a primary tumor drains is a key component of cancer staging. Sentinel lymph node biopsy (SLNB) has been developed over the past decade as a minimally invasive technique to assess regional lymph node status in patients with malignancy.
Despite its routine role in clinical management of cancer, SLNB has a higher false-negative rate (5- 10%) than is generally recognized. The current standard of care in SLNB employs a non-imaging gamma probe to locate and excise the sentinel nodes. We are exploring whether the use of a 3-D intraoperative imaging system using a hand held gamma camera could provide advantages compared to the use of the non-imaging probe. The 3-D intraoperative system has been developed through a collaborative effort involving UVa, Dilon Technologies Inc. (Newport News, Virginia), the Jefferson Lab (Newport News, VA) and SurgicEye, (München, Germany).
The system’s hand held camera has a circular field of view (FOV) of diameter 60 mm and comprises a pixelated NaI(Tl) crystal array coupled to an array of silicon photomultipliers (SiPMs). In 3-D operation an optical tracking system consisting of both visual and infrared (IR) cameras tracks the location and orientation of the camera as it is moved by the surgeon. A fast iterative reconstruction algorithm uses the streamed camera data to produce and display the image of the nodes.
This thesis evaluates the 2-D and 3-D imaging performance of the hand held gamma camera system. Performance metrics include energy resolution, 2D and 3D spatial resolution, gamma ray detection sensitivity, geometric linearity, attenuation compensation, activity quantification accuracy, and the effect of scatter radiation from the radiotracer injection site.