Small Field Of View Gamma Camera Research Articles

Operator motion effects of a small field of view hybrid gamma camera: to hold or not to hold, that is the question?

Recording gamma images using a hand held small field of view (SFOV) hybrid gamma camera requires a few minutes to complete an acquisition. Operator motion during image acquisition may deteriorate image quality and hence affect diagnostic accuracy. The purpose of this study was to assess the magnitude of movement caused by the operator when holding a camera weighing approximately 1kg. Six participants were invited to take part and each was provided with a full explanation of the study. A SFOV hybrid gamma camera was used to acquire gamma images of a radioactive point source containing approximately 15 MBq of 99mTc-pertechnetate placed at source-to-collimator distance (SCD) of 7 cm. Each participant was requested to hold the camera for 3 minutes at their convenience during image acquisition in a clinical setting. A control image was acquired with the camera head mounted on a fixed articulated arm. The scintigraphic images obtained were post-processed and saved as DICOM images prior to assessment using bespoke software (MOCO) to determine the magnitude of motion by tracking the centre of mass (COM) of the hot spot. From this study the centre of mass (COM) was found to move away from the initial point by 4.34 ± 2.43 mm and 7.18 ± 3.34 mm in x and y directions respectively. Subjective assessment of the images acquired with the camera held by an operator showed blurring of details when compared to the control image. The mean COM displacement for the first 30 seconds of the image acquisition was less than 5 mm; however it exceeded 5 mm after one minute of acquisition. This study suggests that the image acquisition time of the SFOV gamma camera should preferably be within a minute when the camera is hand held during use.

CHARACTERIZATION OF A SMALL FOV PORTABLE GC: MediPROBE.

In this work, we evaluated the performance of the prototype SFOV MediPROBE developed at the University of Naples Federico II through the protocol proposed by (Bhatia B.S., Bugby S.L., Lees J.E., Perkins A.C. A scheme for assessing the performance characteristics of a small field of-view gamma cameras. Physica. Medica., 31 (1), pp. 98-103. (2015) doi: 10.1016/j.ejmp.2014.08.004). We extensively investigated a new device configuration where the pinhole collimator was placed outside the housing of the probe, in order to increase the system spatial resolution, and the pixel size was doubled, in order to reduce the charge sharing effect. The experimental measurements show that the spatial resolution is enhanced by only about 10%, but the sensitivity decreases strongly. Therefore, the trade-off between these two features does not seem to be advantageous. In addition, our experiments suggest that the charge sharing effect is not completely canceled. Despite these results, the features of this device appear suitable for intraoperative surgical survey. We aim to use this device in the clinical practice for the intraoperative imaging of lymph nodes, breast, thyroid and parathyroid tumors.

Assessment of the performance of small field of view gamma cameras for sentinel node imaging.

To develop a method for the assessment of small field of view (SFOV) gamma cameras using a novel phantom designed to simulate the localization of sentinel nodes in the presence of a high-activity injection site. The phantom consisted of a cube-shaped acrylic glass support frame. Sixteen acrylic glass plates and nine bars were stacked within the frame to allow a variable configuration of the simulated node depth and node-to-injection site separation. Syringes filled with Tc were used to simulate activity at the injection site and node. Scintigraphic imaging was carried out and the images were assessed subjectively and quantitatively through calculation of the contrast-to-noise ratio. The detection performance of an SFOV gamma camera was then compared with that of a large field of view gamma camera. The detectability studies showed that the SFOV gamma camera could detect low activity in nodes by visual examination of images and with contrast-to-noise ratios ranging from 3 to 62. In particular, the phantom showed the limits of node detection using an SFOV gamma camera over activity ratios less than 1 : 100 and at depths below 45 mm with 25 mm of node-to-injection site separation. Visual subjective assessment of images acquired under the same conditions showed that the SFOV gamma camera was superior to a large field of view camera for the detection of nodes at a node-to-injection site separation of 25 mm. A low-cost phantom has been designed and fabricated that provides a versatile method for the assessment of SFOV gamma cameras intended for sentinel node imaging.

A scheme for assessing the performance characteristics of small field-of-view gamma cameras

Existing protocols for assessing the performance characteristics of large field-of-view (LFOV) gamma cameras can be inappropriate and require modification for use with small field-of-view (SFOV) gamma camera systems. This communication proposes a generic scheme suitable for evaluating the performance characteristics of SFOV gamma cameras, based on modifications to the standard procedures of NEMA NU1-2007. Key differences in methodology between tests for LFOV and SFOV gamma cameras are highlighted along with the rationale for these changes. It is envisaged that this scheme will provide more appropriate methods for equipment characterisation, ensuring quality and consistency for all SFOV cameras.