The Mechanical Design Of Whole-body PET

In this thesis, the whole-body medical PET is designed and its mechanical properties is analyzed. The existing whole-body medical PET usually adopts ring structure, but its number of rings is fixed, so it cannot be upgraded according to market conditions after the equipment is produced. Besides, the existing ring aperture of the whole-body PET is fixed, when it is used to detect small parts of the body, it will lead to declind of the resolution of PET.Firstly, in order to solve the difficulties of the existing PET can not be upgraded, the extensible medical body PET system is designed with the realization of the requirements of the detector’s malposition in line and the detector ring’s alignment. The detector and the detector ring are connected by the pins and bolts, while, the manufacturing precision of the detector packaging box and detector ring are used to ensure malposition in line of the detector. The detector ring is placed on the guide rail to realize the expandability of detector ring and the maintainability of detector, and four detector rings are connected by the guide rod. The detector ring’s alignment is made ensure by the match between the positioning hole of the detector ring and the guide bar.To determine the detector’s malposition in line and the detector ring’s alignment, the paper analyzes the detector, detector ring and guide rod in detail and confirms the main cause of the detector’s malposition in line and the detector ring’s alignment, including stress deformation factor and parts machining accuracy factor. What’s more, the quantitative analysis shows the machining precision of the existing conventional processing methods can achieve the requirements of the detector’s malposition in line and the detector ring’s alignment, and the costs are controlled in the range.The paper proposes and designs a variable aperture PET system, because the sensitivity is decreased while the constant aperture body PET system is used for detecting small parts of the body. The variable aperture mechanism and axial stretching mechanism are designed to achieve a variable aperture PET system. The variable aperture mechanism uses the planar thread and only one motor to control the radial movement of 24 detectors, and it saves cost significantly. Axial stretching mechanism adopts rope to driving three detector rings to move different distance, so that institutions greatly simplified.