ABSTRACT
PURPOSE: Micro-pinhole SPECT system with conventional multiple-head gamma cameras has the advantage of high magnification factor for imaging of rodents. However, several geometric factors should be calibrated to obtain the SPECT image with good image quality. We developed a simplified geometric calibration method for rotating triple-head pinhole SPECT system and assessed the effects of the calibration using several phantom and rodent imaging studies. MATERIAL AND METHODS: Trionix Triad XLT9 triple-head SPECT scanner with 1.0 mm pinhole apertures were used for the experiments. Approximately centered point source was scanned to track the angle-dependent positioning errors. The centroid of point source was determined by the center of mass calculation. Axially departed two point sources were scanned to calibrate radius of rotation from pinhole to center of rotation. To verify the improvements by the geometric calibration, we compared the spatial resolution of the reconstructed image of Tc-99m point source with and without the calibration. SPECT image of micro performance phantom with hot rod inserts was acquired and several animal imaging studies were performed. RESULTS: Exact sphere shape of the point source was obtained by applying the calibration and axial resolution was improved. Lesion detectibility and image quality was also much improved by the calibration in the phantom and animal studies. CONCLUSION: Serious degradation of micro-pinhole SPECT images due to the geometric errors could be corrected using a simplified calibration method using only one or two point sources.
Subject(s)
Animals , Calibration , Gamma Cameras , Head , Imidazoles , Nitro Compounds , Radius , Rodentia , Tomography, Emission-Computed, Single-Photon , Track and FieldABSTRACT
Reflex sympathetic dystrophy (RSD) is a common rheumatic disorder manifesting painful swelling, discoloration, stiffening and atrophy of the skin. Radiographic alterations include small, spotty subperiosteal bone resorption (SBR) and diffuse porosis, and MR imaging shows bone and soft-tissue edema. The purposes of current investigation were to assess 99mTc HDP pinhole SPECT (pSPECT) findings of RSD, to correlate them with those of radiography and MRI and to speculate about causative mechanism of SBR which characterizes RSD. pSPECT was performed in five patients with RSD of the foot. pSPECT showed small, discrete, spotty hot areas in the subperiosteal zones of ankle bones in all five patients. Diffusely increased tracer uptake was seen in the retrocalcaneal surface where the calcaneal tendon inserts in two patients with atrophic RSD. pSPECT and radiographic correlation showed spotty hot areas, that reflect focally activated bone turnover, to closely match with SBR. Further correlation with MRI showed both spotty hot areas and SBR to coincide in location with the insertions of ligaments and tendons, onto which pulling strain is constantly exerted. In contrast, the disuse osteoporosis in unstrained bones did not show any more significantly increased tracer uptake than normal cancellous bones.