Ioflupane I-123

Ioflupane I-123 (DaTscan in the US, DaTSCAN in the EU; GE Healthcare) was approved by the FDA in January 2011 and by the EMA in 2000. It is a SPECT radiopharmaceutical indicated as an adjunct to other diagnostic evaluations for striatal dopamine transporter visualisation in adult patients with suspected Parkinsonian syndromes, to help differentiate essential tremor from tremor due to Parkinson's disease, multiple system atrophy or progressive supranuclear palsy (the scan cannot distinguish between these three), and in adult patients to help differentiate probable dementia with Lewy bodies from Alzheimer's disease (it also cannot separate dementia with Lewy bodies from Parkinson's disease dementia).

The recommended dose is 111-185 MBq (3-5 mCi) given as a slow intravenous injection over at least 15-20 seconds; a thyroid-blocking agent (potassium iodide solution, Lugol's solution or potassium perchlorate) must be given at least one hour beforehand to limit thyroid uptake of free iodine-123. SPECT imaging is performed 3 to 6 hours after injection. Effective dose is about 3.9-4.6 mSv from a 185 MBq administration, depending on the dosimetry source.

Interpretation is by visual (and increasingly semi-quantitative, using striatal binding ratios against normative databases) assessment of striatal uptake shape and intensity: a normal, symmetric comma- or crescent-shaped pattern argues against a parkinsonian syndrome, while reduced, asymmetric or absent putamen uptake supports one. Unlike amyloid PET, DAT SPECT does not currently gate access to any approved disease-modifying therapy; its clinical role remains diagnostic clarification, particularly in early or atypical presentations where tremor aetiology or the AD-versus-Lewy-body-dementia distinction is unclear on clinical grounds alone.