Table 2 Relationship between imaging measures and clinical variables assessed using linear mixed models

From: High-resolution mapping of substantia nigra in Parkinson’s disease using 7 tesla magnetic resonance imaging

  

Substantia nigra

Nigrosome-1

Predictors

Std.Beta

Std. CI

t-statistic

p value

Std.Beta

Std. CI

t-statistic

p value

Linear mixed model, MT CNR

UPDRS-IIIb

−0.07

−0.24 to 0.09

−0.89

0.380

−0.14

−0.29 to 0.02

−1.76

0.079

LEDa

−0.28

−0.52 to −0.04

−2.26

0.024

−0.23

−0.47 to 0.02

−1.82

0.069

Linear mixed model, R2*

UPDRS-IIIb

0.15

0.08 to 0.22

4.06

<0.001*

0.36

0.23 to 0.50

5.14

<0.001*

LEDa

0.00

−0.34 to 0.35

0.03

0.977

−0.01

−0.32 to 0.30

−0.04

0.965

Linear mixed model, QSM

UPDRS-IIIb

0.10

0.00 to 0.20

2.00

0.046

0.21

0.07 to 0.35

2.85

0.004*

LEDa

−0.27

−0.60 to 0.07

−1.57

0.116

0.03

−0.25 to 0.31

0.22

0.823

  1. We constructed linear mixed-effects (LME) models to analyze spatially averaged signal intensities within regions of interest (ROIs). Data from both hemispheres (left and right) were included. Separate models were created for each imaging modality (MT CNR, R2* or QSM) and each anatomical structure (i.e., substantia nigra and nigrosome-1). Fixed effects in the models included hemisphere, age, LED score, sex, and the UPDRS-III score for the contralateral hand. Random intercepts were included for each subject. The models were specified as follows:
  2. ROImean_hemisphere ~ 1 + UPDRS-IIIcontralateral hand + hemisphere + LED + age + sex + (1 | subject)”, where ROImean_hemisphere represents the spatially averaged signal in a given hemisphere for a specific anatomical structure.
  3. Standardized beta-coefficients with 95% confidence intervals are reported for each fixed effect term along with the corresponding t-statistics and uncorrected p values (uncorrected p values < 0.05 in bold).
  4. *False discovery-rate adjusted p value < 0.05.
  5. aLED: Levodopa equivalent dose.
  6. bUPDRS-III: Unified Parkinson’s Disease Rating Scale, subscore III of side contralateral to ROI.
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