Nonkontrast

Nonkontrast, often written as non-contrast in English medical literature, refers to imaging studies performed without the administration of intravenous or intra-arterial contrast agents. Contrast media, such as iodinated agents used in CT or gadolinium-based agents used in MRI, enhance the visibility of blood vessels, tissues, and pathologic processes. Nonkontrast imaging is chosen when there is concern about contrast safety, allergy, renal function, or when the clinical question can be answered without contrast enhancement.

In computed tomography (CT), noncontrast CT is a common first step for evaluating nephrolithiasis, calcifications, acute intracranial hemorrhage, or other conditions where differentiation by enhancement is not essential. It is often used before contrast-enhanced imaging in certain workflows or when rapid assessment is required.

In magnetic resonance imaging (MRI), non-contrast imaging includes standard sequences such as T1-weighted, T2-weighted, FLAIR, and diffusion-weighted imaging. Non-contrast MR angiography techniques, such as time-of-flight (TOF) or phase-contrast methods, can visualize vessels without gadolinium but may have limitations in flow sensitivity and artifact management.

Advantages of nonkontrast imaging include reduced risk of contrast-induced nephropathy, avoidance of allergic reactions, shorter preparation time, and lower cost. Limitations involve diminished tissue contrast and reduced ability to delineate vascular structures or enhancement patterns, which may necessitate follow-up with contrast-enhanced imaging if the initial study yields inconclusive results.

Terminology varies by language and discipline, but the concept remains a baseline imaging approach performed without contrast administration.