Patent activity in this field is concentrated at the top: the leading assignee holds 1,140 of the 15,101 records in scope, and the five largest assignees together account for 17.1% of all records. That concentration extends through the ten largest holders, who together hold 23.1% of records, before dropping off sharply into a long tail of smaller filers. This pattern typically means the core compound chemistry and delivery formats are already well defended by a small group, while device and diagnostic-adjacent claims remain more open.

Filings peaked at 623 records in 2020 and had fallen to 348 by 2024, a 39% decline from the 567 filed in 2021. That is a genuine pullback over a three-year span, not a data artefact. However, counts for 2025 and 2026 are still incomplete because publication typically lags actual filing by around 18 months, so it would be premature to describe the field as still declining based on the most recent one or two years alone.

The large majority of records, 61.6% of the 15,101 in scope, carry A61K medicinal preparation classifications, reflecting the field's roots in contrast compound formulation. Diagnostic and surgical claims (A61B, 18.6%) and therapeutic activity claims (A61P, 18.2%) form a second tier, with delivery devices (A61M, 11.1%) and material testing (G01N, 10.6%) further behind. Because a single patent record can carry several of these classifications at once, the shares add up to more than 100% and describe claim density per class rather than a strict breakdown of the field.

The classification data shows formulation claims (A61K) are far denser than device, monitoring or workflow-related classes such as A61M and G01N. Practical under-claimed areas include injection viscosity control at high flow rates, real-time nephrotoxicity risk monitoring, adverse-reaction management workflows, and iodine delivery rate optimisation hardware. These are areas where filing density is comparatively thin relative to the crowded compound-chemistry core, making them more promising starting points for new claims than core formulation work.

US20050053551A1 covers the use of a combination of gadolinium-based and iodinated contrast media as a single contrast agent for X-ray based imaging procedures such as angiography, CT and cholangiography. Anyone developing a dual-constituent contrast product that mixes a gadolinium element with an iodinated element for X-ray imaging should review this filing directly, since it claims that combination approach rather than either constituent alone. It does not, on its face, block single-constituent iodinated formulations or delivery-device innovations that do not involve a gadolinium combination.