Immunology and AllergyTier 2Topic

Specialised imaging, including arteriography

Role

Specialised imaging in immunology/allergy practice is used predominantly for large- and medium-vessel vasculitis workup, where the vessel wall or lumen changes are not visible on standard imaging
Used when clinical suspicion of vasculitis exists but tissue biopsy is not feasible or would be non-diagnostic (e.g. large-vessel disease, where the affected artery is not readily biopsied)

Techniques

Catheter or CT/MR angiography demonstrates luminal changes - stenosis, occlusion, aneurysm, or the classic "beading" pattern in some vasculitides
PET-CT detects vessel wall inflammation (FDG uptake) even before structural luminal change develops - useful in large-vessel vasculitis (giant cell arteritis, Takayasu arteritis) where early disease may not yet show stenosis

Findings by disease

Takayasu arteritis - arteriography/CTA/MRA shows stenosis, occlusion, or aneurysm of the aorta and its major branches, classically in a younger woman
Giant cell arteritis - temporal artery ultrasound (the "halo sign") is increasingly used as a first-line, less invasive alternative/adjunct to temporal artery biopsy; PET-CT can identify large-vessel involvement beyond the cranial arteries

Guiding biopsy and treatment

Imaging findings guide biopsy site selection when biopsy is still needed, and monitor disease activity/response to treatment over time in large-vessel vasculitis, where clinical assessment alone is a poor activity marker

Conditions

Giant cell arteritis, Takayasu arteritis, other large/medium-vessel vasculitides

Persistent changes

Vessel wall changes (especially on PET-CT) can persist even in clinical remission, complicating the use of imaging alone to guide treatment duration/tapering decisions

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