Digital subtraction angiography (DSA), also known as Dichromography, using synchrotron radiation beams has been
developed at Stanford University (R. Hofstadter) and was subsequently taken over at the Brookhaven Synchrotron and
later at Hamburg (HASYLAB) [see, e.g., W.R. Dix, Physik in unserer Zeit. 30 (1999) 160]. The imaging of coronary
arteries is carried out with an iodine-based contrast agent which need not be injected into the heart. The radiation must
be monochromatized and is applied above and below the K-edge of iodine (33.16 keV), with a subsequent digital
subtraction of the two images. Monochromatization of the synchrotron radiation causes a loss of intensity of 10-3. We
propose instead the use of coherent bremsstrahlung [see, e.g., A.W. Saenz and H. Uberall, Phys. Rev. B25 (1982) 448]
which is inherently monochromatic, furnishing a flux of 1012 photon/sec. This requires a 10-20 MeV electron linac
which can be obtained by many larger hospitals, eliminating the scheduling problems present at synchrotrons.
The large, broad incoherent bremsstrahlung background underlying the monochromatic spike would lead to
inadmissible overexposure of the patient. This problem can be solved with the use of Kumakhov's capillary optics [see
e.g., S.B.Dabagov, Physics-Uspekhi 46
(2003) 1053]: the low-energy spiked radiation can be deflected towards the patient, while the higher energy incoherent background continues forward, avoiding the patient who is placed several
meters from the source.