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Instrumentation & Data Analysis: InstrumentationInstrumentation Posters |
1 UMC Utrecht, Utrecht, Netherlands
1691
Objectives: U-SPECT-II is a high resolution animal scanner consisting of stationary detectors with exchangeable general purpose (GP) cylindrical collimators to facilitate high resolution imaging of both mice and rats. Each GP collimator has 75 micro-pinholes that focus to a small field-of-view (FOV) in order to maximize count-yield. The GP rat collimators (reconstructed resolution ~0.75mm) are sub-optimal for brain imaging. Since (i) the head of the rat is much smaller in diameter than its body and (ii) the brain is located in the top of the skull, pinholes can be placed much closer to the top, the left and right side of the brain.
Methods: New focused collimators were constructed with 0.6 and 0.35 mm gold pinholes. Each collimator consists of 3 full rings with 15 pinholes each (360° sampling) plus two partial rings. The partial rings contain 10 pinholes distributed over 240°. An extrusion is placed in the remaining part to provide sufficient space for the shoulders of the rat. Resolution tests were performed with a Tc-99m filled Derenzo micro-capillary phantom using an extended FOV mode with moving bed in order to sample an area equally sized as the rat brain. Images were reconstructed using ordered-subsets expectation-maximization.
Results: With 0.6 mm pinholes 0.45 mm capillaries were clearly distinguishable. This improved to < 0.4 mm for 0.35 pinholes. Volumetric resolution (mL) is about an order of magnitude better than was obtained with General Purpose rat collimators.
Conclusions: We showed for the first time that it is possible to perform radio-molecular imaging in rat brains at sub-half mm resolution.
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