Table 1

Imaging modalities and markers for Parkinson's disease

Modality	Example tracers/sequence	Observation(s)	Analysis	Accessibility	Cost	Suitability for screening
SPECT	¹²³I-β-CIT ¹²³I-FP-CIT	Loss of binding in striatum	Visual inspection, quantification	++	+++	+++
TCS	2–3.5 Hz transducer	Hyperechogenicity in the region of the substantia nigra	Visual inspection, quantification	++++	+	+++
PET	¹⁸F-dopa ¹⁸F-FDG	Loss of binding in striatum May help differentiate atypical PD	Visual inspection, quantification	++	++++	+
MRI	Traditional (T1& T2), T2/T2* (gradient echo), DTI, spin echo, fMRI	Numerous reported, none established	Visual inspection, quantification	+++	++	++
MIBG	¹²³I-meta-iodobenzylguanidine	Low heart-to-mediastinum ratio	Visual inspection, quantification	++	++	++

Accessibility, cost and suitability for screening are estimated semiquantitatively on a four-point relative scale with + lowest and ++++ highest.
DTI, diffusion tensor imaging; FDG, fludeoxyglucose; fMRI, functional MRI; Hz, hertz; MIBG, metaiodobenzylguanidine; PET, positron emission tomography; SPECT, single photon emission computed tomography; TCS, transcranial sonography.