Whole tumor assessment by 3D-PDU may be inadequatebecause, in large tumors for example, it is virtuallyimpossible to include the whole tumor in just one volumebox.Insuchcases,informationcanbelostandsubsequentanalysis can be subject to bias. Furthermore, in mosttumors vascularization is located in a few areas and notevenly distributed throughout the tumor. Thus one mightinclude within the volume box misleading information.Gray signals from stationary blood clots and mucousplugs, for example, will be processed by the Virtual OrganComputer-aided AnaLysis (VOCAL) software as normal,non-malignant tissue that would reduce the relativeproportion of vascular data within the sampled volume.Furthermore, if the tumor contains cystic areas, theseare irrelevant for analysis. If they contain color voxelsresulting from artifacts or noise, 3D-PDU calculationsmay be erroneously affected. In our opinion, cystic areasshould be excluded to avoid this potential source of error.The selection of a 5-cm