醫(yī)學(xué)影像重建原理課件

1、醫(yī)學(xué)影像重建原理1. DYNAVISION3.Image calibration +2D slice calculation4.3D image generation +3D image displayWorkflow2. Image transfer5.In room data displayPixelSmallest picture element in the image reconstructed from digital data, displayed on a matrix.VoxelSmallest volume unit, picture element. Cube-shape

2、d volume element which is associated with a digitized point in a volume.Bit Depth Number of different colors (or gray shades) available in a data set for displaying each voxel value (HU). OpacityA transparency value can be allocated to each voxel in a data set.Values range from 0.0 to 1.0 and determ

3、ine whether a voxel should be displayed as transparent (low opacity) or as opaque (high opacity).0.11.0HistogramGraphical representation in which the X axis corresponds to the voxel value (CT = Grayscale value). The Y axis represents the number of voxels with a certain voxel value. 100HU-100001000Re

4、ndering All voxels in a data set serve for displaying a 3D image. Rendering refers to a process, e.g. rotation, projection etc. , which is required so that the image can be displayed as 3D image on the screen.OptimizingFine adjustment of colors and transparency values to be able to differentiate tis

5、sue with similar voxel values.Postprocessing - CTMulti-Planar Reconstruction MPRShaded Surface Display SSDMaximum Intensity Projection MIPMinimum Intensity ProjectionVolume Rendering Technique VRTThe visible (i.e not hidden) surface of all selected voxels is displayed; all other voxels are treated a

6、s transparent.ThresholdSSDScans the volume along projection ray projection.The voxels with the highest value, e.g HU-value, are selected.Each voxel is displayed as occurs in the original dataset.Maximum Intensity Projection MIPThe voxels with the highest value are selectedvoxel with the highest atte

7、nuationMIPMIP3D dataset2D MIP image Volume Rendering VRTProduction of a histogram of the voxel values and their distribution.Each voxel is rendered with an opacity and absorption value (color values also possible).Adaptations are made interactively and in real time. 100Grayscale-100001000Mean valueV

8、RTVRT3D dataset2D VRT imageVolume Rendering VRTThe resulting image is a summation of voxel values which can be rotated and displayed on the screen in all projections.No loss of data! 100% of the data set are used.VRT shaded3D dataset2D VRT imageThe computer projects a light sourceExample!Anatomical

9、spatial relations between organs are retained2. Advantages of VRT compared with SSD and MIP No time-consuming editing required in order to eliminate cloudy or concealing structures.3. Advantages of VRT compared with SSD and MIP Sees through “to the other side” of walls. Looks into cavities which are not accessible to normal endoscopy.Permits insights between concealed structures.4. Advantages of VRT compared with SSD and MIP Opacity 15%Unshaded VRTEvaluation of lumen diameter - same dataset.9.6 mmOpacity 50%Unshaded VRT9.6 mmOpacity 50%Shaded VRTRefraction index 4