orthodiagram
noun
or·tho·di·a·gram
| \ -ˈdī-ə-ˌgram
\
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Medical Definition of orthodiagram
: a tracing showing the outer contours and exact size of an organ (as the heart) made by illuminating the edge of the organ with parallel X-rays through a small movable aperture and marking the outer edge of the shadow cast upon a fluoroscopic screen