Introduction Peripheral venous catheterization (PVC) is the most common invasive procedure in healthcare worldwide. Improving the success rate of PVC on the first attempt is crucial for patients, as it impacts pain, anxiety, the risk of extravasation, rapid access to care, and the patient-provider relationship. For healthcare providers, a higher success rate enhances self-confidence and autonomy, while institutions benefit from improved reputation and reduced costs. In the Poitiers hosptial, one in ten catheters is used in imaging services, with CT scan departments accounting for 66.3% of catheter usage due to iodinated contrast injections. Literature suggests two techniques to enhance PVC success: ultrasound-guided and infrared illumination methods. These techniques appear effective primarily for patients with difficult venous access. Additionally, the A-DIVA clinical score has been developed to predict first-attempt success rates. However, no studies in Europe have compared the effectiveness of these two techniques in imaging settings or based on the A-DIVA score. This study aims to identify the most effective technique for PVC in patients with difficult venous access. Objectives Compare the proportion of successful PVCs on the first attempt among the classical method (Gold Standard), ultrasound-guided technique, and infrared illumination technique in adult patients with difficult venous access. Compare the proportion of successful PVCs on the second attempt (if the first attempt fails) among the three techniques. Compare the total number of attempts required for successful PVC. Evaluate the maximum pain experienced by patients during successful PVC. Assess overall patient satisfaction following successful PVC. Evaluate operator satisfaction with the procedure. Measure the time taken for catheterization from material preparation to successful catheter placement. Analyze the fallback strategies chosen by operators after a failed attempt (e.g., calling a colleague, continuing with the classical method, using ultrasound guidance, infrared illumination, or abandoning the procedure). Describe the catheter sizes chosen by operators based on the A-DIVA score and the number of failed attempts. Methodology This is a prospective, controlled, randomized, three-arm, single-center, superiority trial involving patients with difficult venous access. Inclusion criteria include: Patients aged 18 years or older. Patients scheduled for a CT scan requiring PVC. Patients with an A-DIVA score of 2 or higher. Patients capable and willing to comply with study procedures. Patients covered by social security or through a third party. Patients providing written informed consent after receiving clear information about the study. Exclusion criteria include: Patients with contraindications for PVC (e.g., presence of an arteriovenous fistula, orthopedic or vascular prosthesis, history of mastectomy, etc.). Patients with contraindications for iodinated contrast injection as defined by the French Society of Radiology. Patients already included in the study. Vulnerable populations (e.g., minors, pregnant or breastfeeding women, individuals deprived of liberty). Intervention Groups Control: Classical method based on clinical examination (visualization and palpation). Experimental: Ultrasound-guided method. Experimental: Infrared illumination method. Sample Size and Duration A total of 249 patients will be enrolled, with 82 patients in each group. The inclusion period will last 12 months, and each participant will be involved for a maximum of 4 hours. The total duration of the clinical investigation will be 1 year and 4 hours. Outcome Measures The primary outcome is the proportion of successful PVCs on the first attempt, defined as the administration of 5 ml of NaCl without reported pain or visible edema. The total number of skin penetrations by the catheter will be recorded. Maximum pain will be assessed using a numerical rating scale (0-10). Patient satisfaction will be measured using a similar numerical scale. Operator satisfaction will also be evaluated on a scale from 0 (very dissatisfied) to 10 (very satisfied). Time for catheterization will be recorded in minutes, starting from the preparation of the PVC tray until successful catheter placement. The fallback strategy after a failed attempt will be documented. The size of the catheter chosen for each attempt will be recorded. Statistical Analysis The primary outcome will be compared among the three groups using ANOVA, followed by pairwise comparisons using Tukey's test if significant differences are found. Expected Outcomes Identifying the most effective PVC technique could increase the likelihood of first-attempt success in adults with difficult venous access. Benefits for Patients Reduced pain and discomfort from multiple attempts. Decreased risk of infection and extravasation. Maintenance of venous integrity. Sustained trust in the patient-provider relationship.