Table 2.
Explanations and equations of the investigated clinical and imaging factors
| Variable | Explanation/equation |
|---|---|
| Mean DAT binding | (higher putamen SBR + lower putamen SBR)/2 |
| DAT binding asymmetry index | (right − left putamen SBR)/(right + left putamen SBR) |
| Motor symptom severity | Total score of the MDS‐UPDRS motor part (part III) |
| PD motor subtype (TD/PIGD/intermediate) | The ratio of 11 tremor and 5 PIGD items in MDS‐UPDRS. Ratio of ≥1.15 was classified as tremor‐dominant, ratio ≤0.90 was classified as PIGD and 0.90 < ratio < 1.15 was classified as intermediate15 |
| Motor symptom asymmetry index |
(right − left side score)/(right + left side score) Score of lateralized items in MDS‐UPDRS Part III was calculated separately for the left and right side (rigidity in upper extremity + rigidity in lower extremity + finger tapping + hand movement + pronation/supination + toe tapping + leg agility + hand postural tremor + hand kinetic tremor + hand rest tremor + foot rest tremor) |
| Predominant side of motor symptoms (right/left/symmetric) |
Right = (MDS‐UPDRS Part III right − left side score/right + left side score) > 0.3 Left = (MDS‐UPDRS Part III right − left side score/right + left side score) < −0.3 Symmetric = −0.3 ≤ (MDS‐UPDRS Part III right − left side score/right + left side score) ≤0.3 |
| Predominant side of DAT binding defect |
Right = (right − left putamen SBR/right + left putamen SBR) > 0.05 Left = (right − left putamen SBR/right + left putamen SBR) < −0.05 |
| Tremor asymmetry index |
(right − left side score)/(right + left side score) Score of lateralized tremor items in MDS‐UPDRS Part III was calculated separately for the left and right side (hand postural tremor + hand kinetic tremor + hand rest tremor + foot rest tremor) |
| Bradykinesia‐rigidity asymmetry index |
(right − left side score)/(right + left side score) Score of lateralized bradykinesia or rigidity items in MDS‐UPDRS Part III was calculated separately for the left and right side (rigidity in upper extremity + rigidity in lower extremity + finger tapping + hand movement + pronation/supination + toe tapping + leg agility) |
DAT, dopamine transporter; SBR, specific binding ratio; TD, tremor‐dominant subtype; PIGD, postural instability and gait disorder subtype.