However, the assessment of the serotonergic system in the human hypothalamus in vivo is difficult as delineation of the hypothalamus is cumbersome with conventional region-of-interest analysis.
Preoperative radiotherapy can make tumour delineation difficult by inducing further fibrosis and submucosal oedema.
However, since the soft tissue contrast is comparatively poor in CT, the organ delineation remains difficult.
This alignment of cells at the boundaries corresponds to domains of Wingless and Hedgehog signalling (Figure 5A and B), though by late third instar, the increase in cell number makes it difficult to perceive the delineation of cells along the A/P axis.
Hence, a gold standard for tumour delineation is difficult to obtain [ 33].
CE enhances the contrast between areas with different topography on the mucosal surface, but some early gastric cancers are completely flat (type 0-IIb), making margin delineation particularly difficult with conventional non-magnifying endoscopy.
CT is currently not used for systematic prosthesis evaluation clinically or in clinical studies but is used for preoperative planning in difficult cases with better delineation of osteolysis than radiography [ 9, 10], for evaluation of suspected osteolysis or granulomas in painful hips, and for evaluation of iliopsoas muscle and tendon complications.
However, fluid identification, pressure estimation and hydrocarbon column delineation can be difficult in complex reservoirs and particularly in the case of tight reservoirs.
Traditional classification approaches to the characterization of urbanization may prove inadequate in some human-modified landscapes where complex and unique combinations of conditions can make classification and delineation of patches difficult.
Training time is a bit more difficult to analyze, as manual delineation time is involved and is the most time consuming part of the process.
