Hi Timothy, The contrast and the spatial resolution mostly depends on the spatial resolution of the CT image you are projecting. I don't think you can do better with Joseph's projector. Regarding contrast, you might want to apply the Beer Lambert law (opposite then exponential) to have something more similar to a kV projection (up to a multiplicative constant probably). I have BCCed Andy Shieh (first author of your reference) in case he has something else to suggest. I hope it helps, Simon
On Tue, Sep 10, 2024 at 6:12 PM Timothy Wang Bok Yau <ty...@uwo.ca> wrote: > Hi everyone, > > I recently started using rtk to generate DRRs and was hoping to receive > some insight on how to improve the quality of a DRR generated from a > patient CT. I am hoping that the DRR would be able to approximate the > quality of a kV projection from a cone beam CT. Currently I am setting the > projection parameters to match the kV acquisition parameters on our linear > accelerators, but am finding that the DRRs I produce are very blurry with > low contrast. I was able to find some studies in the literature using rtk > to generate DRRs and have found that their image quality is significantly > better than what I am currently achieving (see Fig. 1 from the following > paper https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4833659/). I've copied > my code for generating the DRRs. Any insight would be greatly appreciated. > > # Read CT in from DICOM files > dirName = r"C:\Users\yaut\CT" > namesGenerator = itk.GDCMSeriesFileNames.New() > namesGenerator.SetUseSeriesDetails(True) > namesGenerator.AddSeriesRestriction("0008|0021") > namesGenerator.SetGlobalWarningDisplay(False) > namesGenerator.SetDirectory(dirName) > uid = namesGenerator.GetSeriesUIDs()[0] > fileNames = namesGenerator.GetFileNames(uid) > > # Setup the image series reader using GDCMImageIO > ImageType = itk.Image[itk.F,3] > reader = itk.ImageSeriesReader[ImageType].New() > dicomIO = itk.GDCMImageIO.New() > reader.SetImageIO(dicomIO) > reader.SetFileNames(fileNames) > reader.ForceOrthogonalDirectionOff() > > # Read DICOM > reader.Update() > CT = reader.GetOutput() > > # change the direction and origin to align with the RTK convention > CTDirection = np.array([[0.,1.,0.],[0.,0.,1.],[-1.,0.,0.]]) > CT.SetDirection(itk.matrix_from_array(CTDirection)) > > # Center the image around 0 which is the default center of rotation > > CT.SetOrigin([-0.5*(CT.GetLargestPossibleRegion().GetSize()[1]-1)*CT.GetSpacing()[1], > > -0.5*(CT.GetLargestPossibleRegion().GetSize()[2]-1)*CT.GetSpacing()[2], > > 0.5*(CT.GetLargestPossibleRegion().GetSize()[0]-1)*CT.GetSpacing()[0]]) > > > # Set forward projection geometry > geometry = rtk.ThreeDCircularProjectionGeometry.New() > > # Image type > ImageType = itk.Image[itk.F,3] > > # Image geometry > geometry = rtk.ThreeDCircularProjectionGeometry.New() > numberOfProjections = 360 > firstAngle = 0 > angularArc = 2*np.pi > > # Source to isocentre distance in mm > sid = 1000 > > # Source to detector distance in mm > sdd = 1500 > > for x in range(0,numberOfProjections): > angle = firstAngle + x*angularArc/numberOfProjections > geometry.AddProjectionInRadians(sid,sdd,angle,inPlaneAngle=np.pi) > > # Create a stack of empty projection images > # Spacing and output size are set based on kV acquisition parameters on > our Linacs > ConstantImageSourceType = rtk.ConstantImageSource[ImageType] > constantImageSource = ConstantImageSourceType.New() > origin = CT.GetOrigin() > sizeOutput = [1024, 1024, numberOfProjections ] > spacing = [0.388, 0.388, 0.5] #mm > constantImageSource.SetOrigin( origin ) > constantImageSource.SetSpacing( spacing ) > constantImageSource.SetSize( sizeOutput ) > constantImageSource.SetConstant(0.) > > # Generate DRRs > JosephType = rtk.JosephForwardProjectionImageFilter[ImageType, ImageType] > joseph = JosephType.New() > joseph.SetGeometry(geometry) > joseph.SetInput(constantImageSource.GetOutput()) > joseph.SetInput(1, CT) > > > _______________________________________________ > Rtk-users mailing list > rtk-us...@openrtk.org > https://www.creatis.insa-lyon.fr/mailman/listinfo/rtk-users >
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