Transient thermal imaging has not as yet found a niche among industrial NDE methodologies even though the field has been active since the mid 1980’s. Difficulty with image interpretation is perhaps the primary reason. An ambiguous image leads to false calls and lack of confidence. Ultrasonics, on the other hand appears not to generally suffer from these issues for a simple reason — the term “flat-bottom hole” (FBH) is second nature in the field. Such standards encourage quantitative imaging. The present work provides a deeper insight into certain invariances in 1-D and 2-D heat flow that permit the use of flatbottom hole standards to quantify thermal imaging yielding reproducible and interpretable images of flaws. The very simple theoretical basis for these effects will be described with emphasis placed on the thermal images obtained and the accuracy of the quantitative results. We describe recent work both at GE-CRD and UTRC in the area of thermal standards evaluation.