Need for an additional imaging modality in Adaptive Radiotherapy

Is an additional modality of imaging needed or helpful for better detection of contour changes in head and neck cancer? Add your comments below.

Santam I feel that while cone beam CT scans give excellent resolution of the normal anatomy in future I would like to have additional modalities of imaging to make assessment of contour changes more relevant. The rationale is of course the fact that delineating the GTV in the oropharynx and larynx is difficult during the course of radiotherapy on CT images. Even KV CT scans are not good for this purpose. While the anatomical boundaries will remain constant and well visible during the course of radiotherapy I feel integration of other imaging modalities may help us to be more accurate with the DELINEATION part. I would like to know what the house feels about two imaging modalities in particular PET-CT and MRI. My hunch is in the future we will start to see more MR based adaptive radiotherapy. One machine design seems particularly welcome Co Tomotherapy with Integrated MRI. Another imaging cum treatment modality I would be interested in PET imaging after proton beam therapy for treatment verification and dose reconstruction.
Andrew 1. PET
PET will be useful for dose mapping and deliberate dose inhomogeneity, and that change during treatment.
2. MRI
I have never seen a during treatment MRI to comment on the resolution of anatomic structures
Pranshu I thought that the issue of choosing an appropriate threshold of SUV to differentiate tumour from non-tumour is still not clear.. has there been an update on this? Chaning window levels can completely change the volumes. MR is probably the likely step ahead, if something could be done about the scan time. We need to remember that every additional minute that the patient stays on couch, adds to the intra-fraction positional errors. About conebeam giving excellent resolution of normal anatomy, I guess we must be having "primitive" CBCT units here at PMH.. I suggest you can try delineating prostate by manual soft tissue match on the same CBCT but at different times to find out how variable we can be because of not so excellent image quality?
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