MRI to Delineate the Gross Tumor Volume of Nasopharyngeal Cancers:
AbstractBackground: Magnetic resonance imaging (MRI) has been found to be better than computed tomography for defining the extent ofprimary gross tumor volume (GTV) in advanced nasopharyngeal cancer. It is routinelyapplied for target delineation in planning radiotherapy. However, the specificMRI sequences/planes that should be used are unknown. Methods:Twelve patients with nasopharyngeal cancer underwent primary GTV evaluation withgadolinium-enhanced axial T1 and T2, coronal T1, and sagittal T1 sequences.Each sequence was registered with the planning computed tomography scans. Planningtarget volumes (PTVs) were derived by uniform expansions of the GTVs. The volumesencompassed by the various sequences/planes, and the volumes common to allsequences/planes, were compared quantitatively and anatomically to the volumedelineated by the commonly used axial T1-based dataset. Results and Discussion: Addition of the axial T2 sequence increased the axial T1-basedGTV by 12% on average (p= 0.004), and composite evaluations that included thecoronal T1 and sagittal T1 planes increased the axial T1-based GTVs by 30% onaverage (p= 0.003). The axial T1-based PTVs were increased by 20% by theadditional sequences (p= 0.04). Each sequence/plane added unique volumeextensions. The GTVs common to all the T1 planes accounted for 38% of the totalvolumes of all the T1 planes. Anatomically, addition of the coronal andsagittal-based GTVs extended the axial T1-based GTV caudally and cranially, notablyto the base of the skull.Conclusions: Adding MRI planes and sequences to the traditional axial T1 sequenceyields significant quantitative and anatomically important extensions of theGTVs and PTVs. For accurate target delineation in nasopharyngeal cancer, werecommend that GTVs be outlined in all MRI sequences/planes and registered withthe planning computed tomography scans.
How to Cite
popovtzer, A. (2014). MRI to Delineate the Gross Tumor Volume of Nasopharyngeal Cancers:. Radiology and Oncology, 48(3). Retrieved from https://radioloncol.com/index.php/ro/article/view/2066