A prototype small CdTe gamma camera for radioguided surgery and other imaging applications

Abstract

Gamma probes have been used for sentinel lymph node biopsy in melanoma and breast cancer. However, these probes can provide only radioactivity counts and variable pitch audio output based on the intensity of the detected radioactivity. We have developed a small semiconductor gamma camera (SSGC) that allows visualisation of the size, shape and location of the target tissues. This study is designed to characterise the performance of the SSGC for radioguided surgery of metastatic lesions and for other imaging applications amenable to the smaller format of this prototype imaging system. The detector head had 32 cadmium telluride semiconductor arrays with a total of 1,024 pixels, and with application-specific integrated circuits (ASICs) and a tungsten collimator. The entire assembly was encased in a lead housing measuring 152 mmx166 mmx65 mm. The effective visual field was 44.8 mmx44.8 mm. The energy resolution and imaging aspects were tested. Two spherical 5-mm- and 15-mm-diameter technetium-99m radioactive sources that had activities of 0.15 MBq and 100 MBq, respectively, were used to simulate a sentinel lymph node and an injection site. The relative detectability of these foci by the new detector and a conventional scintillation camera was studied. The prototype was also examined in a variety of clinical applications. Energy resolution [full-width at half-maximum (FWHM)] for a single element at the centre of the field of view was 4.2% at 140 keV (99mTc), and the mean energy resolution of the CdTe detector arrays was approximately 7.8%. The spatial resolution, represented by FWHM, had a mean value of 1.56 +/- 0.05 mm. Simulated node foci could be visualised clearly by the SSGC using a 15-s acquisition time. In preliminary clinical tests, the SSGC successfully imaged diseases in a variety of tissues, including salivary and thyroid glands, temporomandibular joints and sentinel lymph nodes. The SSGC has significant potential for diagnosing diseases and facilitating subsequent radioguided surgery.

Evaluation of the Efficacy of a Small CdTe γ-Camera for Sentinel Lymph Node Biopsy

“…Allowing the surgeon to see the spatial distribution of the increased radioactivity could result in more accurate delineation of the surgical field, thus facilitating the surgery. Therefore, we developed a prototype small semiconductor g-camera (SSGC) that provides images of radioactivities for surgical use (1).…”

“…The preliminary results of a simulation study for sentinel lymph node biopsy with the SSGC suggested that this camera would identify sentinel node radioactivity during the procedure (1).…”

“…Several reports of handheld small g-cameras have been published (1,(8)(9)(10)(11)(12)(13)(14)(15), but studies to date have not verified the effectiveness of small g-cameras in depicting nodes with increased radioactivities in the clinical setting of sentinel lymph node biopsy. In this study, we aimed to confirm our earlier results regarding the basic performance of the SSGC and to extend the preliminary findings by using the camera in an animal study and a clinical setting.…”

Roles of prostaglandin E2-EP1 receptor signaling in regulation of gastric motor activity and emptying

“…The cannulae were secured with thread at the middle of the esophagus and at the pylorus, respectively. Physiological saline or 1 M NaCl solution (37°C) containing 50 mg/ml BSA prelabeled with 99m Tc was applied to the stomach through the esophageal cannula, and the movement of 99m Tc-labeled BSA from stomach to duodenum was determined with a small semiconductor gamma camera (Acrorad, Tokyo, Japan) (45). The radioactivity of the duodenum 15 min after application was expressed as a percentage of the initial radioactivity applied to the stomach.…”

Assessment of Spatial Resolution on SPECT using Image Processing

“…NEMA NU1-2007 [10] states the "pixel size should be less than or equal to 0.1 FWHM", that is _0.3 mm for a 540 mm diameter gamma camera. To achieve the specified "pixel size" the analogue to digital conversion gain is increased perpendicular to the line source for each orthogonal axis simultaneously, and the "zoomed" portion of the field of view is imaged.SFOV cameras have reported values of spatial resolution of less than 1.0 mm [15,16,17,18], suggesting that the NEMA "pixel size" should be at most 0.1 mm (equal to 0.1 FWHM). For a typical LFOV resolution of 3 mm, the use of a 0.5 mm line source will not have a large effect on measured resolution; at submillimeter resolution, however, the width of the same source becomes significant.…”