Abstract: The present invention provides methods and apparatus for measuring and/or marking the internal features of a patient body when those features are viewed under fluoroscopy or another medical imaging modality. Although suitable for the physiological measurement of many body lumens, including the intestines, the urethra, and the like, the present invention will find its most immediate use in the measurement of vascular lesions, particularly vascular aneurysms adjacent the aortoiliac junction and other bifurcations. The positions and bend angles of such branching body lumens can be accurately mapped on a panel which remains outside the patient body. By imaging the patient through the panel, and by providing markings on the panel which give a bright contrast when imaged, the panel provides a guide that highlights the length, position, and geometry of the luminal lesion.