An Atlas-Based Electron Density Mapping Method for Magnetic Resonance Imaging (MRI)-Alone Treatment Planning and Adaptive MRI-Based Prostate Radiation Therapy

MR image‐based synthetic CT for IMRT prostate treatment planning and CBCT image‐guided localization

“…3(e). Absolute HU errors of 90% voxels of soft tissue were less than 46 HU using the proposed method, and 74 HU using the direct mean method 12 , 13 . Eighty percent (80%) of bone voxels had absolute HU errors less than 150 HU using the proposed method, and 153 HU using the direct mean method.…”

“…Our proposed image intensity selection method has the ability to overcome these drawbacks via selecting proper atlas‐CT for different voxel in S‐CT determined using the intersection of the atlas‐ROI masks. Consequently, the proposed method achieved much better result compared with the direct arithmetic mean method 12 , 13 Figures 3(c) and (d) demonstrate a typical case and the absolute error histogram comparison.…”

“…While providing promising results, they are not practical since these special sequences are not generally available in clinic. DIR‐based methods have also been explored to generate S‐CT 12 , 13 , 14 , 15 , 16 . However, using DIR algorithms directly 12 , 13 to map HU from the CT images in the atlas library to an S‐CT image suffers from inherent registration errors due to large anatomical differences between different patients.…”

“…DIR‐based methods have also been explored to generate S‐CT 12 , 13 , 14 , 15 , 16 . However, using DIR algorithms directly 12 , 13 to map HU from the CT images in the atlas library to an S‐CT image suffers from inherent registration errors due to large anatomical differences between different patients. It is possible to reduce registration uncertainty, either by improving the accuracy of DIR algorithm or by combining with a “CT voxel intensity selection algorithm” 14 , 16 .…”

Monte Carlo calculation based on hydrogen composition of the tissue for MV photon radiotherapy

“…Current methods to derive electron density from MRI data by generating a pseudo‐CT are divided into two approaches: the anatomy‐based and the voxel‐based methods. In the anatomy‐based methods, deformable registration of reference paired MRI/CT scan (atlas or reference patient) to the MRI scan of the patient under consideration is used to build a pseudo‐CT from the warped reference CT scan 19 , 20 , 21 . Although mathematical or statistical operations could be used to smooth registration errors due to interpatient anatomical differences, 19 , 20 these methods fail for patients presenting high anatomy dissimilarities.…”