Non-invasive evaluation of intestinal disorders: The role of elastographic techniques

Table 1 Summary of the technical features of the various elastographic techinques

Technique	Physical characteristic measured	Excitation method
Strain elastography/UEI	Strain	Manual compression (operator pressure, cardiovascular pulse, breathing movements)
ARFI imaging	Strain	Acoustic radiation force impulse
Shear wave elastography	Shear wave speed	Acoustic radiation force impulse
Point-shear wave speed measurement
Shear wave speed imaging
Transient elastography	Shear wave speed	Controlled external vibration

UEI: Ultrasound elasticity imaging; ARFI: Acoustic radiation force impulse.

Table 2 Summary of the feasibility studies on elastography in animal models

Ref.	Subjects		Results
Kim et al[11], 2008	Animal model (rats)	Technique	Strain difference of normal colon vs affected left colon P < 0.0002
	6 Left-sided chronic colitides (from TNBS)	Strain elastography (UEI)
	5 controls	Comparison	Significant correlation between Young’s modulus and strain r = 0.67, P < 0.0005
		Direct mechanical measurement, Histology
Stidham et al[10], 2011	Animal model (TNBS rats)	Technique	Strain values:
	5 acute colitides	Strain elastography (UEI)	controls vs acute inflammation P = 0.015,
	5 chronic fibrosis	Comparison	controls vs chronic fibrosis P = 0.001,
	5 controls	Histology	acute inflammation vs chronic fibrosis P = 0.037
			Strain ratio:
			acute inflammation vs chronic fibrosis P = 0.030
Dillman et al[45], 2013	Animal model	Technique	SW velocity ratio:
	6 acute colitides	Shear wave elastography (Shear wave speed imaging)	AUROC curve for differentiating fibrosis from inflammation 0.971
	8 chronic colitides/fibrosis
	3 controls	Comparison
		Histology

TNBS: Trinitrobenzenesulfonic acid; UEI: Ultrasound elasticity imaging; CD: Crohn’s disease; AUROC: Area under receiver operating characteristic; SW: Shear wave; VAS: Visual analogue scale.

Table 3 Studies assessing the utility of elastography in intestinal diseases

Ref.	Subjects		Outcomes
Stidham et al[10], 2011	7 CD patients with stricturing disease	Technique	Strain values:
		Strain elastography (UEI)	Correlation with Young’s modulus r = -0.81
		Comparison	Significant difference between stenotic tissue and unaffected proximal tissue P = 0.0008
		Direct mechanical measurement, Histology
Dillman et al[46], 2014	17 Human intestinal surgical specimens (from subjects with known or suspected IBD)	Technique	Difference in SW speed between low and high fibrosis
		Shear wave elastography (point SW speed measurement and SW speed imaging)	With point SW speed measurement, P = 0.004, AUROC = 0.91
		Comparison	With SW speed imaging P = 0.049 AUROC = 0.77
		Histology	No difference in mean SW speed between low and high inflammation
Havre et al[50], 2014	Human intestinal surgical specimens	Technique	UEI able to discriminate between adenoma and adenocarcinoma/CD, not between adenocarcinoma and CD
		Strain elastography (UEI)
	16 CD	Comparison	Reproducibility:
	18 adenocarcinoma	Histology	SR: intraobserver correlation rho = 0.47-0.82
	4 adenomas		Visual categorical score: interobserver agreement k = 0.38
			VAS: interobserver correlation Pearson’s r = 0.55, P = 0.002
Baumgart et al[47], 2015	10 CD patients elected for surgery	Technique	Higher strain values in affected vs unaffected bowel (P < 0.001)
		Strain elastography (UEI)
		Comparison	Good ICC among pre-, intra- and post-operative strain measurements (0.830 in affected segments)
		Direct mechanical measurement,
		Histology	Association between strain measurements and
			internal muscularis mucosae and muscularis propria width (P = 0.044 and 0.012)
			histologic fibrosis score (P < 0.001)
Fraquelli et al[49], 2015	23 CD patients elected for surgery	Technique	Interrater agreement: color scale (ICC 0.90) and SR (ICC 0.78)
		Strain elastography (UEI)
	20 CD controls	Comparison	Correlation between SR and severity of bowel fibrosis P < 0.0001 but not with inflammation scores
		Histology
			AUROC curve for prediction of severe fibrosis 0.917 (95%CI: 0.788-1.000)
Fufezan et al[48], 2015	14 pediatric CD patients (48 bowel segments)	Technique	Correlation between:
		Strain elastography (UEI)	UEI “inflammatory type” and complications
		Comparison	UEI “inflammatory” and “fibrotic” type and CRP
		US signs and Clinical Data	UEI “inflammatory type” and ESR
			UEI and bowel wall thickness and stratification

TNBS: Trinitrobenzenesulfonic acid; UEI: Ultrasound elasticity imaging; CD: Crohn’s disease; AUROC: Area under receiver operating characteristic; SW: Shear wave; VAS: Visual analogue scale; ICC: Intraclass correlation coefficient; SR: Strain ratio; CRP: C reactive protein; ESR: Erythrocyte sedimentation rate; US: Ultrasound.