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Publication Detail
In silico validation of motion-including dose reconstruction for MR-guided lung SBRT using a patient specific motion model
  • Publication Type:
    Conference
  • Authors:
    Bertholet J, Eiben B, Menten M, Tran EH, Hawkes DJ, Wetscherek A, Nill S, McClelland JR, Oelfke U
  • Publisher:
    ICCR
  • Publication date:
    20/06/2019
  • Published proceedings:
    Proceedings of the 19th International Conference on the Use of Computers in Radiation Therapy
  • Status:
    Accepted
  • Name of conference:
    ICCR, 19th International Conference on the Use of Computers in Radiation Therapy
  • Conference place:
    Montreal, Canada
  • Conference start date:
    17/06/2019
  • Conference finish date:
    20/06/2019
Abstract
Motion-including dose reconstruction (MIDR) aims at reconstructing the actually delivered dose to the moving anatomy during radiotherapy. Patient-specific motion models (PSMM) can be used to determine the time-resolved anatomy during treatment delivery on an MR-linac for MIDR. In this study, PSMM-based MIDR was validated for MR-guided lung SBRT. The digital XCAT phantom was used to generate a ground truth moving anatomy (GT-XCAT) based on in-vivo measured motion. Using the first 10 minutes of the motion trace, GT-XCAT volumes were subsampled to simulate pre-treatment interleaved sagittal/coronal MR acquisition with a sagittal navigator slice for breathing signal extraction. A PSMM was fitted and a motion-compensated super-resolution image (MCSRI) was reconstructed simultaneously. An MR-linac treatment plan for 3-fraction lung-SBRT was designed on a reference GT-XCAT. GT-XCATs were generated for the remainder of the motion trace. The intra-treatment time-resolved anatomy was estimated via MCSRI deformation using the PSMM and the breathing signals extracted from navigator slices sub-sampled from GT-XCATs. Treatment delivery was simulated in our in-house emulator. The treatment fluence was discretized into sub-beams, each associated with the GT or deformed-MCSRI anatomy that it was delivered to. The dose was accumulated onto the reference anatomy. For comparison, shift-MIDR was calculated emulating tumour motion as sub-beam isocenter shifts on the static reference GT-XCAT anatomy. For the plan dose, GT-MIDR, PSMM-MIDR and shift-MIDR respectively: GTV-D98% was 70.8Gy, 67.7Gy, 69.0Gy and 67.4Gy; GTV-D50% was 77.7Gy, 775.2Gy, 75.5Gy and 76.0Gy; heart-V30Gy was 48.4cc, 55.6cc, 53.0cc and 64.7cc; Oesophagus-V2% was 22.6Gy, 21.7Gy, 21.7Gy and 23.1Gy. Evaluated against GT-MIDR, PSMM-MIDR was more accurate than shift-MIDR for organ at risk (OAR) dose estimation and similar for target dose estimation. The MR-based PSMM was shown to be suitable for MIDR of the target and OAR. Shift-MIDR is not intended to correctly estimate OAR dose but may be used for target dose estimation.
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Dept of Med Phys & Biomedical Eng
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Dept of Med Phys & Biomedical Eng
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Dept of Med Phys & Biomedical Eng
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