Real-time MRI has become an increasingly useful tool in articulatory studies, especially in examining posterior regions of the vocal tract. Previous work on Brazilian Portugese has shown the emergence of coda consonants following word-final nasal vowels, though this has been limited to the discussion of front vowels and coda emergence in anterior regions of the vocal tract. We present rt-MRI evidence showing a narrow constriction between the tongue dorsum and velum emerging at the end of back nasal vowels, patterning similarly with velar stop consonants. Though our present subject does not show evidence of complete occlusion, we believe the small distance between the tongue dorsum and velum makes the emergence of a velar consonant highly likely. The emergence of these consonants is a result of sound change that further distinguishes oral and nasal vowel pairs. We also show the utility of advanced image processing methodologies to give a more accurate and computationally economical way to do speech articulation research.