We have developed a miniature scintillation camera to be used in surgical cancer staging. The availability of such a compact hand-held gamma camera may in certain cases improve localization of the sentinel lymph node and reduce the duration of a surgical breast cancer staging procedure. We have investigated image processing algorithms applied to planar images that may improve node detection capabilities for breast cancer staging. We have also studied contrast enhancement methods that may be able to identify nodes that would otherwise be missed. Exposure duration for a given camera position can be adaptively shortened or increased by using an optical flow algorithm to estimate camera motion with respect to the current frame. By determining if the camera is in motion or not, the exposure time may be increased to allow more image counts to accumulate at a given camera position. Adaptive exposure time may improve the ease of use of the hand-held camera, and allow regions of interest to be imaged more effectively. We feel that these image processing techniques can improve the utility of a hand-held gamma ray imager for sentinel lymph node detection during breast cancer staging.
"Another research group has addressed the issue of motion blurring and small field of view of a hand-held camera by attempting to use motion sensors to tile the image into a large synthetic field of view , . In this camera, assuming the surgeon scans slowly, the motion blurring can controlled using optical flow . "
[Show abstract][Hide abstract] ABSTRACT: A compact, hand-held gamma camera with excellent intrinsic and extrinsic performance has been developed for the rapid identification and localization of sentinel lymph nodes during the surgical staging of cancer. The camera comprises a 5times5 cm<sup>2</sup> field of view NaI (Tl) pixellated crystal array, a high sensitivity lead (2.0 cm thick) hexagonal parallel-hole collimator, a position sensitive photomultiplier tube (PSPMT), and a novel highly multiplexed electrical readout. The intrinsic energy resolution (12.1plusmn2.0%) at 140 keV including edge crystals, extrinsic sensitivity (5 cps/muCi from 1-5 cm with a 24% energy window) and extrinsic spatial resolution (1.81plusmn0.1 mm at 0.6 cm) facilitate rapid identification of a radioactive node. Using a node phantom we performed an ideal observer study to estimate the detectability of small spheres in the range of 3 mm to 8 mm with different exposure times. With a 5 seconds exposure the camera can detect a 3 mm diameter sphere at a depth of 3.6 cm containing 1 muCi of Tc-99m within a cold background, and a 4 mm diameter sphere containing 2 muCi at 2.6 cm depth within a warm background (>10:1 contrast) with a 5 second exposure duration. [All rights reserved Elsevier].
[Show abstract][Hide abstract] ABSTRACT: A compact, hand-held gamma camera with excellent intrinsic and extrinsic performance has been developed for the rapid identification and localization of the sentinel lymph node during the surgical staging of cancer. A goal for this device is an image acquisition time of five seconds to allow the surgeon to easily search for points of interest without excessive motion blurring. The camera comprises a 5×5 cm<sup>2</sup> field of view NaI (TI) pixellated crystal array, a high sensitivity (2.0 cm thick) hexagonal parallel-hole collimator, a position sensitive photomultiplier tube (PSPMT), and a novel highly multiplexed electrical readout. The good intrinsic energy resolution (12.3±2.6%) resolution, extrinsic sensitivity (5 cps/μCi with 24% energy window) and extrinsic spatial resolution (1.6+/-0.02 mm at 0.5 cm) facilitate rapid identification of a hot node.
[Show abstract][Hide abstract] ABSTRACT: Preoperative lymphoscintigraphy (PLS) combined with intraoperative gamma probe (GP) localization is standard procedure for localizing the sentinel lymph nodes (SLN) in melanoma and breast cancer. In this study, we evaluated the ability of a novel intraoperative handheld gamma camera (IHGC) to image SLNs during surgery.
The IHGC is a small-field-of-view camera optimized for real-time imaging of lymphatic drainage patterns. Unlike conventional cameras, the IHGC can acquire useful images in a few seconds in a free-running fashion and be moved manually around the patient to find a suitable view of the node. Thirty-nine melanoma and eleven breast cancer patients underwent a modified SLN biopsy protocol in which nodes localized with the GP were imaged with the IHGC. The IHGC was also used to localize additional nodes that could not be found with the GP.
The removal of 104 radioactive SLNs was confirmed ex vivo by GP counting. In vivo, the relative node detection sensitivity was 88.5 (82.3, 94.6)% for the IHGC (used in conjunction with the GP) and 94.2 (89.7, 98.7)% for the GP alone, a difference not found to be statistically significant (McNemar test, p = 0.24).
Small radioactive SLNs can be visualized intraoperatively using the IHGC with exposure time of 20 s or less, with no significant difference in node detection sensitivity compared to a GP. The IHGC is a useful complement to the GP, especially for SLNs that are difficult to locate with the GP alone.
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