Écart interquartile | EPFL Graph Search

vignette|Diagramme en boîte avec l'écart quartile apparent (noté IQR) En statistiques, l’écart interquartile (aussi appelé étendue interquartile ou EI ; en anglais, interquartile range ou IQR'') est une mesure de dispersion qui s'obtient en faisant la différence entre le troisième et le premier quartile : : EI = Q3 - Q1. L'EI est un estimateur statistique robuste. Exemples Tableau de données :{| class="wikitable" |- ! Valeurs ! % ! Quartile |- | 1|| 102 |- | 2|| 104 |- | 3|| 105|| Q1 |- | 4|| 107 |- | 5|| 108 |- | 6|| 109|| Q2 (médiane) |- | 7|| 110 |- | 8|| 112 |- | 9|| 115|| Q3 |- | 10|| 116 |- | 11|| 118 |} L'écart interquartile de cette distribution de données (noté EI), est EI = Q3 - Q1 = 115 - 105 = 10. Données dans une boîte à moustaches Cette boîte à moustaches sommaire montre :

premier quartile Q_1 = 7
deuxième quartile (médiane) Q_2 = 8,5
troisième quartile Q_3 = 9
écart interquartile Q_3-Q_1 = 2

Notes et référ

3-Dimensional Fluid and White Matter Suppression Magnetic Resonance Imaging Sequence Accelerated With Compressed Sensing Improves Multiple Sclerosis Cervical Spinal Cord Lesion Detection Compared With Standard 2-Dimensional Imaging

Tobias Kober

Objectives Fluid and white matter suppression (FLAWS) is a recently proposed magnetic resonance sequence derived from magnetization-prepared 2 rapid acquisition gradient-echo providing 2 coregistered datasets with white matter- and cerebrospinal fluid-suppressed signal, enabling synthetic imaging with amplified contrast. Although these features are high potential for brain multiple sclerosis (MS) imaging, spinal cord has never been evaluated with this sequence to date. The objective of this work was therefore to assess diagnostic performance and self-confidence provided by compressed-sensing (CS) 3-dimensional (3D) FLAWS for cervical MS lesion detection on a head scan that includes the cervical cord without changing standard procedures. Materials and Methods Prospective 3 T scans (MS first diagnosis or follow-up) acquired between 2019 and 2020 were retrospectively analyzed. All patients underwent 3D CS-FLAWS (duration: 5 minutes 40 seconds), axial T-2 turbo spin echo covering cervical spine from cervicomedullary junction to the same inferior level as FLAWS, and sagittal cervical T-2/short tau inversion recovery imaging. Two readers performed a 2-stage double-blind reading, followed by consensus reading. Wilcoxon tests were used to compare the number of detected spinal cord lesions and the reader's diagnostic self-confidence when using FLAWS versus the reference 2D T-2-weighted imaging. Results Fifty-eight patients were included (mean age, 40 +/- 13 years, 46 women, 7 +/- 6 years mean disease duration). The CS-FLAWS detected significantly more lesions than the reference T-2-weighted imaging (197 vs 152 detected lesions, P < 0.001), with a sensitivity of 98% (T-2-weighted imaging sensitivity: 90%) after consensual reading. Considering the subgroup of patients who underwent sagittal T2 + short tau inversion recovery imaging (Magnetic Resonance Imaging for Multiple Sclerosis subgroup), +250% lesions were detected with FLAWS (63 vs 25 lesions detected, P < 0.001). Mean reading self-confidence was significantly better with CS-FLAWS (median, 5 [interquartile range, 1] [no doubt for diagnosis] vs 4 [interquartile range, 1] [high confidence]; P < 0.001). Conclusions Imaging with CS-FLAWS provides an improved cervical spinal cord exploration for MS with increased self-confidence compared with conventional T-2-weighted imaging, in a clinically acceptable time.

LIPPINCOTT WILLIAMS & WILKINS2022

Tobias Kober

LIPPINCOTT WILLIAMS & WILKINS2022