THE PHYSICAL PERFORMANCE OF DIFFERENT X-RAY CONTRAST AGENTS - CALCULATIONS USING A MONTE-CARLO MODEL OF THE IMAGING CHAIN

A Monte Carlo computational model of the imaging chain has been used t o investigate the performance of x-ray contrast agents with atomic num ber, Z, 53 less than or equal to Z less than or equal to 90 with respe ct to physical image quality descriptors (contrast and signal to noise ratio, SNR) and patient mean absorbed dose. Contrast agents of equal molar concentrations were used within a water slab (simulating the pat ient). The imaging conditions were chosen to represent adult and paedi atric examinations. For all tube potentials studied (40-140 kV), the c ontrast agents with the highest atomic numbers (bismuth and thorium) g ave the highest contrast. In analogue screen-film imaging, several oth er contrast agents could produce a higher image contrast than iodine i n a limited range of tube potentials. This advantage could alternative ly be effected as a reduced amount of administered contrast agent, or as a reduced mean absorbed dose in the patient. In digital imaging, a lower mean absorbed dose for a constant SNR than that with iodine can be achieved for ranges of tube potentials and contrast agents. Bismuth and thorium yield a lower dose than iodine at all studied tube potent ials. Gadolinium and erbium could alternatively be used at a broad ran ge of tube potentials above 90 kV with a dose penalty of only 5-20%.