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ISRT vs INRT
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In both INRT and ISRT, the prechemotherapy GTV determines the CTV,
and the irradiated volume is significantly smaller than with IFRT
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However, ISRT accomomodates cases in which optimal prechemotherapy
imaging is not available to the radiation oncologist
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In these situations, it is not possible to reduce the CTV to the same extent
as with INRT, because the prechemotherapy GTV information may not be
optimal
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In ISRT, clinical judgment in conjunction with the best available imaging
is used to contour a larger CTV that will be accommodate the uncertainties
in defining the prechemotherapy GTV