Intraoperative Gamma Camera Research Articles

Intraoperative Gamma Cameras: A Review of Development in the Last Decade and Future Outlook.

Portable gamma cameras suitable for intraoperative imaging are in active development and testing. These cameras utilise a range of collimation, detection, and readout architectures, each of which can have significant and interacting impacts on the performance of the system as a whole. In this review, we provide an analysis of intraoperative gamma camera development over the past decade. The designs and performance of 17 imaging systems are compared in depth. We discuss where recent technological developments have had the greatest impact, identify emerging technological and scientific requirements, and predict future research directions. This is a comprehensive review of the current and emerging state-of-the-art as more devices enter clinical practice.

The utility of pre-operative lymphoscintigraphy for sentinel lymph node biopsy in breast cancer

Background: Sentinel lymph node (SLN) identification in breast cancer is most commonly performed by a combination of preoperative Tc99 with lymphoscintigraphy, intraoperative gamma camera localization, and visualization using a dye technique. It is reported that using these together results in the most accurate localization with lowest false negative rates. Non-visualisation of SLNs on scintigraphy is reported in upto 30% and some work has questioned its utility in routine practice, however image acquisition remains part of the minimum dataset within procedural guideline.

A novel fully integrated handheld gamma camera

In this paper, we present an innovative, fully integrated handheld gamma camera, namely designed to gather in the same device the gamma ray detector with the display and the embedded computing system. The low power consumption allows the prototype to be battery operated.To be useful in radioguided surgery, an intraoperative gamma camera must be very easy to handle since it must be moved to find a suitable view. Consequently, we have developed the first prototype of a fully integrated, compact and lightweight gamma camera for radiopharmaceuticals fast imaging. The device can operate without cables across the sterile field, so it may be easily used in the operating theater for radioguided surgery.The prototype proposed consists of a Silicon Photomultiplier (SiPM) array coupled with a proprietary scintillation structure based on CsI(Tl) crystals. To read the SiPM output signals, we have developed a very low power readout electronics and a dedicated analog to digital conversion system. One of the most critical aspects we faced designing the prototype was the low power consumption, which is mandatory to develop a battery operated device.We have applied this detection device in the lymphoscintigraphy technique (sentinel lymph node mapping) comparing the results obtained with those of a commercial gamma camera (Philips SKYLight). The results obtained confirm a rapid response of the device and an adequate spatial resolution for the use in the scintigraphic imaging.This work confirms the feasibility of a small gamma camera with an integrated display. This device is designed for radioguided surgery and small organ imaging, but it could be easily combined into surgical navigation systems.

Laparoscopic lymphatic roadmapping with blue dye and radioisotope in colon cancer

Lymphatic mapping (LM) and sentinel lymph node (SLN) identification by blue dye in colon cancer is a procedure feasible during minimally invasive surgery, with good specificity, but still a low sensitivity (78% in our series). These results are in accordance with the literature and have limited more widespread diffusion of the method, both as a tool for upstaging and more controversially, as a potential roadmap to a tailored lymphadenectomy. It is possible to improve the results of LM with careful selection of patients and by the use of an intraoperative gamma camera. The preliminary results of intra-operative lymphoscintigraphy are promising in a well-selected small group of patients, with high levels of sensitivity and specificity. If these results are confirmed in further prospective analyses, it may be possible to undertake selected, tailored lymphadenectomy.

P21 Presentation of multicentric trial about sentinel node identification with sentinella intraoperative gamma camera versus traditional gamma probe

P21 Presentation of multicentric trial about sentinel node identification with sentinella intraoperative gamma camera versus traditional gamma probe

Radioguided occult lesion localisation in breast cancer using an intraoperative portable gamma camera: first results

The role of the radioguided occult lesion localisation (ROLL) technique in breast cancer has been increasing in recent years. One of the important drawbacks of such a technique is radiotracer spillage within the mammary gland that makes the precise lesion resection difficult, and this requires the use of a hook-wire collocation to reach the lesion. The possibility of obtaining an intraoperative image of the specimen could help to confirm whether the lesion is correctly removed. Some types of portable gamma cameras have been designed, but up to now, intraoperative use has been confined to surgery of parathyroid adenomas and sentinel lymph node location. The aim of the study was to value the usefulness of an intraoperative gamma camera to assess the resection of non-palpable breast lesions. The study involved 42 women diagnosed with non-palpable early breast cancer. Lymphoscintigraphy was performed on the day before surgery by injection of (99m)Tc-labelled nanocolloid. During surgery a gamma probe was used to guide the surgeon, and afterwards images of the surgical bed and the tumoral specimen were acquired by means of a portable gamma camera, fitted with a pinhole collimator. A (99m)Tc pointer was used to draw an outline image around the specimen. On lymphoscintigraphy, radiotracer was concentrated in 31 cases. During surgery, all lesions were removed. In the images acquired by the portable gamma camera, the lesion was centred inside the surgical specimen in 23 of 42 cases, non-centred in 15 and in contact in 4 cases. Congruence of 60% was found between the intraoperative images and the histopathological results. The posterior margin was the most frequently involved. The whole acquisition time for the tumoral specimen with its margins was 5 min at most. The use of portable gamma cameras in theatre is in an early phase. The short period of time required during the surgical procedure will allow the surgical team to improve this technique until it can replace hand-held probes. The intraoperative acquisition of such images can predict the involvement of surgical margins, avoiding future surgical procedures.

Technologies en développement pour l'identification des ganglions sentinelles en chirurgie mammaire

Sentinel lymph node (SLN) biopsy is now routinely used in breast cancer multidisciplinary management. The combined use of blue dye and lymphoscintigraphy gives the best SLN identification rate. Two different types of probes are available for the SLN procedure: semi-conductor probes and scintillator ones. Moreover, to increase the performances of the SLN procedure, intra-operative gamma cameras have recently been developed. The objectives of our review are to describe these materials to highlight their advantages and drawbacks from the point of view of the surgeon and the physicist.

A newly developed intra-operative gamma camera: performance characteristics in a laboratory phantom study

Radioguided surgery depends on the intra-operative detection of radiolabelled tissues. This is currently accomplished with hand tools capable of providing a tone signal, depending on the proximity and direction of a radioactive source in relation to the probe. The advantages of visual images of radiolabelled tissues are well recognised, but satisfactory means of acquiring such images intra-operatively are not yet available. The goal of this study was to examine the performance of a newly developed intra-operative gamma camera, compact enough to be a hand tool and capable of yielding a visual image of the source field. The study was performed in the laboratory with a phantom consisting of a water bath and small hollow spheres (1-2 cm in internal diameter) filled with 99mTc (1-5 microCi/cc), placed in different configurations within the bath. For comparison, studies were also performed using a standard intra-operative gamma probe, and others using a standard single-head high-resolution gamma camera. Compared with the gamma probe, the intra-operative camera was found to possess a superior ability to distinguish small, deep and weakly localised radioactivity sources from background. By acquiring images from different angles, it allowed a 3D understanding of multiple radioactive sources. It detected "cold" defects within a "hot" radiolabelled sphere. It discriminated a weak source located near a much "hotter" radioactivity source, similar to discrimination with the standard gamma camera, and discerned localised sources against a background of radioactivity. It is anticipated that the high imaging potential of the camera tested in this study will offer clinical advantages.

Development of an intraoperative gamma camera based on a 256-pixel mercuric iodide detector array

A 256-element mercuric iodide (HgI/sub 2/) detector array has been developed which is intended for use as an intraoperative gamma camera (IOGC). The camera is specifically designed for use in imaging gamma-emitting radiopharmaceuticals (such as 99m-Tc labeled Sestamibi) incorporated into brain tumors in the intraoperative surgical environment. The system is intended to improve the success of tumor removal surgeries by allowing more complete removal of subclinical tumor cells without removal of excessive normal tissue. The use of HgI/sub 2/ detector arrays in this application facilitates construction of an imaging head that is very compact and has a high SNR. The detector is configured as a cross-grid array. Pixel dimensions are 1.25 mm squares separated by 0.25 mm. The overall dimension of the detector is 23.75 mm on a side. The detector thickness is 1 mm which corresponds to over 60% stopping at 140 keV. The array has good uniformity with average energy resolution of 5.2/spl plusmn/2.9% FWHM at 140 keV (best resolution was 1.9% FWHM). Response uniformity (/spl plusmn//spl sigma/) was 7.9%. A study utilizing realistic tumor phantoms (uptake ratio varied from 2:1 to 100:1) in background (1 mCi/l) was conducted. SNRs for the reasonably achievable uptake ratio of 50:1 were 5.61 /spl sigma/ with 1 cm of background depth (normal tissue) and 2.74 /spl sigma/ with 4 cm of background for a 6.3 /spl mu/l tumor phantom (/spl sim/270 nCi at the time of the measurement).

Development of a mercuric iodide detector array for medical imaging applications

A nineteen element mercuric iodide (HgI 2) detector array has been developed as a prototype for a larger (169 element) array, which is intended for use as an intra-operative gamma camera (IOGC). This work is motivated by the need for identifying and removing residual tumor cells after the removal of bulk tumor, while sparing normal tissue. Prior to surgery, a tumor seeking radiopharmaceutical is injected into the patient, and the IOGC is used to locate and map out the radioactivity. The IOGC can be used with commercially available radioisotopes such as 201Tl, 99mTc, and 123I which have low energy X- and gamma-rays. The use of HgI 2 detector arrays in this application facilitates construction of an imaging head that is very compact and has a high signal-to-noise ratio. The prototype detectors were configured as discrete pixel elements joined by fine wires into novel pseudo crossed-grid arrays to promote improved electric field distribution compared with previous designs, and to maximize the fill factor for the expected circular probe shape. Pixel dimensions are hexagonal with 1.5 mm and 1.9 mm diameters separated by 0.2 mm thick lead septa. The overall detectors are hexagonal with a diameter of ∼1 cm. The sensitive detector thickness is 1.2 mm, which corresponds to >99% efficiency at 59 keV and 67% efficiency at 140 keV. Row, column, and pixel spectra have been measured on the prototypical detector array. Energy resolution was found to vary with the width of the row/column coincidence window that was applied. With the low edge of the coincidence window at 30% below the photopeak, pixel energy resolutions of 2.98% and 3.88% FWHM were obtained on the best individual pixels at 59 keV ( 241Am) and 140 keV ( 99mTc), respectively. To characterize this array as an imaging device, the spatial response of the pixels was measured with stepped point sources. The spatial response corresponded well with the pixel geometry, indicating that the spatial resolution was determined by the pixel geometry.