Synthetic 4D-CT of the thorax for treatment plan adaptation on MR-guided radiotherapy systems.

Synthetic 4D-CT of the thorax for treatment plan adaptation on MR-guided radiotherapy systems. Phys Med Biol. 2019 Mar 07;: Authors: Freedman JN, Bainbridge H, Nill S, Collins DJ, Kachelriess M, Leach MO, McDonald F, Oelfke U, Wetscherek A Abstract MR-guided radiotherapy treatment planning utilises the high soft-tissue contrast of MRI to reduce uncertainty in delineation of the target and organs at risk. Replacing 4D-CT with MRI-derived synthetic 4D-CT would support treatment plan adaptation on hybrid MR-guided radiotherapy systems for inter- and intrafractional differences in anatomy and respiration, whilst mitigating the risk of CT to MRI registration errors.
 
 Three methods were devised to calculate synthetic 4D and midposition (time-weighted mean position of the respiratory cycle) CT from 4D-T1w and Dixon MRI. The first approach employed intensity-based segmentation of Dixon MRI for bulk-density assignment (sCT<sub>D</sub>). The second step added spine density information using an atlas of CT and Dixon MRI (sCT<sub>DS</sub>). The third iteration used a polynomial function relating Hounsfield units and normalised T1w image intensity to account for variable lung density (sCT<sub>DSL</sub>). Motion information in 4D-T1w MRI was applied to generate synthetic CT in midposition and in twenty respiratory phases. For six lung cancer patie...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research