Patients , following a three-day low-fibre diet , received one of the two reduced preparations : 1-L polyethylene glycol and four tablets of bisacodyl in association with 90 mL of Iopamidol for faecal tagging administered on the same day as CTC examination ( group 1 ) ; or a standard `` iodine-only '' preparation , consisting in 180 ml of Iopamidol the day before the examination ( group 2 ) .