limited to these examples bismuth iodine and bromine containing contrast medium solutions 4s 4 ethoxybenzyl 3 6 9 tris carboxylatomethyl 3 6 9 triazaundecanoic acid bismuth complex disodium salt iotrolan inn or n cetyl n n n trimethylammonium bromide are produced at a concentration of 9 8 mg of bi ml 6 mg of iodine ml or 3 8 mg of br ml in 2 agar the agar gels are cut into layers that are 3 mm 5 mm or 10 mm thick the contrast medium containing gels as well as a control gel with 2 8 mg of nacl ml are integrated into an agar block with a thickness of 5 cm the entire phantom is x rayed at 28 kv and 63 ma corresponding to a mammogram whereby the x ray radiation in each case has to pass through about 4 cm to 5 cm of contrast mediumfree agar and 3 mm to 10 mm of contrast medium containing agar even the contrast medium containing agar pieces that are only about 3 mm thick are readily detectable at an equimolar concentration bromine is surprisingly enough about twice as effective as iodine bismuth is more than three times as effective as iodine fig1 0050 fig1 shows an x ray image at 28 kv 63 ma of an agar phantom with embedded contrast medium containing agar blocks of a left series with a thickness of 5 mm a center series with a 10 mm thickness and a right series with a 3 mm thickness the blocks of the upper series contain 3 8 mg of bromine ml those of the center series contain 6 mg of iodine ml and those of the lower series.