Intravenous coronary angiography with synchrotron radiation

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Abstract
Coronary angiography is the established routine imaging modality for patients with coronary artery disease. In recent years, the number of these procedures has increased remarkably. Complications associated with this invasive approach are in the range of 1.5% and the mortality is 0.1%. A further reduction of risk appears difficult to achieve because of the invasive nature of the procedure. Therefore, efforts have been made to image coronary arteries by non-invasive or minimally invasive techniques. One method under development is dichromography. This technique is based on subtraction of two images at different energies. Dichromography allows imaging of small fast-moving objects like the coronary arteries including distal parts and sidebranches after intravenous injection of a contrast material. Two images with monochromatic x-rays just below and above the absorption K-edge of the contrast agent iodine at 33.17 keV are obtained simultaneously and logarithmically subtracted. Monochromatic x-rays of sufficient intensity to visualize coronary arteries of 1 mm diameter with a low iodine mass density of are only provided by synchrotron radiation. At the Hamburger Synchrotronstrahlungslabor HASYLAB at DESY in Hamburg, Germany the system NIKOS was developed for dichromography. This system consists of six main parts: a wiggler beamline, a two beam monochromator, a safety system, a scanning device with a seat for the patient, a two-line detector, and a computer system. After initial experimental studies with dogs, human patients have been investigated since 1990. Results of investigated patients demonstrate the feasibility and safety of the method together with high diagnostic accuracy. All cases were follow-up investigations after bypass surgery or interventions like angioplasty with a balloon catheter or rotablation with a very fast milling tool. A large-scale study has been underway since June 1997 to validate the diagnostic sensitivity and specificity compared with selective coronary angiography.