Optimization of Contrast Agent Dose in CT With Lean Body Weight (CA_LBW)

This study evaluates the different enhancement using a contrast agent dose in computed tomography based on total body weight or based on lean body weight. Half of participants will receive contrast agent dose based on their total body weight, while the other half will receive a dose based on their lean body weight. Our hypothesis is that if contrast agent is administered not basing on total body weight but on lean body weight it is possible to obtain equal or better quality of enhanced images, a reduction of the variability of contrast enhancement, and also a dose reduction in some patients (overweight ones).

Patients will undergo a CT scan of abdomen (multi-phasic) with contrast agent and will be measured: total body weight (TBW), height, lean body weight (LBW) and body mass index (BMI) through formulas known in literature and with a balance for bioelectrical impedance analysis. There is no administration of drugs other than those indicated in the request of the treating physician. Contrast agent dose: IOPAMIRO® (Iopamidol) is an x-ray contrast medium of the new generation of non-ionic compounds, which are watersoluble because the molecular structure incorporates hydrophilic groups. Recommended dosage (ml) is 0.5-2.0/kg. Single injection volume depends on the vascular area to be examined. IOMERON® (Iomeprolo) is an x-ray contrast medium of the new generation of non-ionic compounds, which are watersoluble because the molecular structure incorporates hydrophilic groups. Recommended dosage (ml) is 0.5-2.0/kg. Single injection volume depends on the vascular area to be examined. Patients will be randomly assigned to undergo one of the two contrast agent protocols. Control group (TBW protocol): patients will receive a contrast agent dose based on their TBW as a standard clinic protocol with a dose of 0.40 gI/kg of TBW. There are no differences compared to clinical practice. Experimental group (LBW protocol): patients will receive a contrast agent dose based on their calculated LBW to test our hypothesis with a dose of 0.65 gI/kg of LBW, derived from our pilot study (LBW_01 approved 10/11/2016, registration number 160/int/2016). If radiologists prefer a more enhanced examination, only scanning with contrast agent will be repeated with the standard dose as the standard clinical protocol.

The study design is monocentric, comparative, randomized, double blinded. Patients will undergo a CT scan of abdomen (multi-phasic) with contrast agent and will be measured: TBW, height, LBW and body mass index (BMI) through formulas known in literature and with a balance for bioelectrical impedance analysis. There is no administration of drugs other than indicated in the request of the treating physician.

Patients will be assigned to the TBW or LBW group based on a randomization generated by a computer, the progressive sequences containing the randomization code will be perform by an outside operator to the experiment group. Only CT technician and nurse that will record patient's data and results from scale analysis will know and will register in which group the patients will be assigned.

Contrast agent will be adrministered intravenously using total body weight or lean body weight, calculated with bioelectrical impedance analysis balance.

The liver contrast enhancement (ΔCEL) will be calculated as the difference between the CT value measured in the venous phase and that measured before contrast injection.

Inclusion Criteria: Patient ≥ 18 years of age; Patients who will perform a contrast-enhanced abdominal CT multi-phasic in our institutions; Patients able to give informed consent. Exclusion Criteria: history of chronic underlying liver disease (cirrhosis, fatty infiltration of the liver, or glycogen storage disease); history of chronic underlying heart disease (congestive heart failure, prior cardiac valve replacement, restrictive and/or constrictive pericarditis); multiple myeloma; hypersensitivity to iodine-containing compounds; renal insufficiency (serum creatinine level ≤ 1.8 mg/dL [159.12 µmol/L]) or patients with renal failure (eGR <30 ml/min/1.73 m2); patients with antecubital vein that, at medical evaluation, cannot sustain the flow rate of CA injection (see below); patients carrier of prosthesis or metal bullets, pacemaker or stimulators; patients with liver diseases that affect the entire parenchyma; fragile patients which, after radiologist evaluation, require lower dose of CA; pregnancy; general contraindications to CT examination or reasoned decision of the radiologist.