Mucosal imaging in colon polyps: New advances and what the future may hold

Table 1 Meta-analyses on efficacy of real-time computer aided detection

Ref.	Studies, patients	ADR			Adenoma per patient			Withdrawal time	False positives
		AI	WLI	RR	AI	WLI	Mean difference	Mean difference CADe vs control
Aziz et al[112], 2020	3 studies, 2815 patients	32.9%	20.8%	1.58	0.47	0.26	0.20	0.9 min (P = 0.03)	4.87% (n = 137)
Hassan et al[113], 2021	5 studies, 4354 patients	36.6%	25.2%	1.44	0.58	0.36	0.22	0.34 min (P = 0.13)	-
Spadaccini et al[114], 2021	6 studies, 5178 patients	34.0%	26.6%	1.78	-	-	-	No significant difference	-
Barua et al[115], 2021	5 studies, 4311 patients	29.6%	19.3%	1.52	0.41	0.23	0.18	0.5 min	11.2%

ADR: Adenoma detection rate; AI: Artificial intelligence; WLI: White light imaging; RR: Relative risk; CADe: Computer aided detection.

Table 2 Summary of strengths and weakness of advanced imaging technologies in adenoma detection

Modality		Strengths	Weaknesses
HD-WLI		Widely available	Marginal incremental benefit over SD-WLI
		Increased detection of flat, right-sided adenomas and SSAs
Chromoendoscopy		Increased detection of small and flat adenomas	No significant increase in detection of advanced adenomas
		Increased dysplasia detection in IBD (compared to SD-WLI)	Increased procedural time
		May increase polyp detection in high-risk syndromes (serrated polyposis syndrome, HNPCC)
Virtual chromoendoscopy	NBI	May improve flat lesion detection	Loss of brightness and familiarity of colour patterns
		Effective in those with experience using NBI	No evidence of increased total adenoma detection
			Less effective when used by proceduralists inexperienced in NBI
	i-SCAN	May reduce miss-rates in high-risk populations	Not widely available
			No difference in adenoma detection in larger studies
			Insufficient evidence to recommend use
	FICE	Retains familiar colour patterns	Not widely available
			No difference in ADR
	LCI	Retains familiar colour patterns	Not widely available
		Effective when used by non-LCI experienced proceduralists	Variable evidence regarding overall adenoma detection
		Improve adenoma detection, particularly right sided and flat lesions
	BLI	Improved adenoma detection and miss rate in smaller studies	Not widely available
			No difference in ADR in largest study to date
	TXI	Retains familiar colour patterns	Not widely available
			New technology therefore insufficient evidence
AFI		Improved detection of flat/right sided polyps	Not widely available
			Increased procedure time
			No difference in overall ADR
AI		Improves ADR	Expensive currently
		Improves consistency between proceduralists	Not widely available
		Quality assurance	Some increase in procedure time
FME		In theory may improve detection of flat/poorly visible polyps	Insufficient evidence
			Requires injection/ingestion of tracer

HD-WLI: High-definition white light imaging; SD-WLI: Standard definition white light imaging; HNPCC: Hereditary non-polyposis colon cancer; NBI: Narrow-band imaging; IBD: Inflammatory bowel disease; BLI: Blue light imaging; TXI: Texture and colour enhancement imaging; FME: Fluorescence molecular endomicroscopy; AI: Artificial intelligence; AFI: Autofluorescence imaging; SSA/Ps: Sessile serrated adenomas/polyps; ADR: Adenoma detection rate.

Table 3 Summary of existing classification systems using advanced mucosal imaging

System	Imaging modality	Polyp features	Accuracy	Complexity	TA/TVAs included	SSAs included
Kudo	Any	Pits	AUC 0.94[143]	Complex	Yes	No
NICE	NBI	Vessels and pits	Sensitivity 98%, NPV 97.8%[145]	Moderate	Yes	No
JNET	NBI	Vessels and pits	AUC 0.97 for JNET 1, 0.84 for JNET 2A, 0.9 for JNET 3 but less accurate for JNET 2B (AUC 0.72)[152]	Moderate	Yes	No
BASIC	BLI	Vessels, pits and surface	Accurate surveillance prediction in 90%, NPV for rectosigmoid polyps 91%[160]	Moderate	Yes	No
WASP	Any	Pits, surface, shape	May improve SSA detection[162]	Simple	No	Yes
mSano	NBI	Vessels, pits and surface	AUC 0.92[169]	Simple	Yes	Yes

NBI: Narrow-band imaging; WASP: Workgroup serrAted polypS & polyposis; TVA: Tubulo-villous adenomas; AUC: Area under the receiver operating characteristic curve; NPV: Negative predictive value; BASIC: Blue light imaging adenomas serrated international classification; JNET: Japan NBI Expert Team developed the Japan NBI expert team; NICE: NBI International Colorectal Endoscopic; LCI: Linked colour imaging; SSA: Sessile serrated adenomas.

Table 4 Studies on the accuracy of AI for polyp histology prediction

Ref.	Study type	Imaging modality	Number of patients/polyps	Sensitivity	Specificity	NPV	Accurate surveillance interval
Kominami et al[209], 2016	Retrospective	NBI	41 patients, 118 polyps	93%	95%	93%	92.7%
Chen et al[210], 2018	Retrospective	NBI	284 polyps	96%	78%	90%	-
Mori et al[211], 2018	Prospective	NBI	325 patients, 466 polyps	93%	90%	95%	-
Renner et al[212], 2018	Retrospective	WLI, NBI	100 polyps	92%	63%	90%	-
Byrne et al[213], 2019	Retrospective	NBI	125 polyps	98%	83%	97%	-
Min et al[214], 2019	Prospective	LCI	91 patients, 217 polyps	83%	70%	71%	-
Sánchez-Montes et al[206], 2019	Retrospective	WLI	225 polyps	92%	89%	87%	-
Horiuchi et al[215], 2019	Prospective	AFI	95 patients, 258 polyps	80%	95%	93%	-
Ozawa et al[216], 2020	Retrospective	WLI, NBI	309 polyps	97% for NBI, 90% for WLI	-	91% for NBI, 85% for WLI	-
Jin et al[205], 2020	Retrospective	NBI	300 polyps	83%	90%	94%	-
Zacharia et al[208], 2020	Retrospective	WLI, NBI	524 polyps	96%	90%	93%	94%
Rodriguez-Diaz et al[217], 2021	Retrospective	NBI	119 patients, 280 polyps	96%	84%	91%	94%
Van der Zander et al[218], 2021	Retrospective	WLI, BLI	54 patients, 60 polyps	96%	93%	88%	-
Yoshida et al[220], 2021	Retrospective	BLI	25 patients, 100 polyps	91%	85%	92%	-
Sakamoto et al[219], 2022	Retrospective	WLI, BLI	604 polyps	96% for WLI, 96% for BLI	84% for WLI, 89% for BLI	-	-

NBI: Narrow-band imaging; NPV: Negative predictive value; BLI: Blue light imaging; WLI: White light imaging; LCI: Linked colour imaging.

Table 5 Summary and conclusions for each form of advanced mucosal imaging discussed

Modality		Detection	Characterisation	Comment
HD-WLI		Advantages: Marginal benefit in overall adenoma detection; and improved detection of right-sided, flat polyps, and SSAs1	Advantage: Marginal benefit for small adenomas; disadvantage: Insufficient evidence for large polyps	Advantage: Widely available
Chromo-endoscopy		Advantage: Increases polyp detection; disadvantage: Increases withdrawal time	Advantages: Highly effective for small polyps (although inefficient); and useful in prediction of invasion depth for large polyps1	Disadvantage: Increases procedural time
Virtual chromo-endoscopy	NBI	Disadvantage: No significant difference in ADR	Advantages: Accurate for distinguishing neoplastic from non-neoplastic small and diminutive polyps; and accurate for prediction of invasion depth1	Disadvantage: Loss of brightness; neutral: Greater efficacy when used by expert proceduralists
	i-SCAN	Neutral: Variable results, increased detection of flat and right-sided polyps	Advantage: Effective for diminutive and small polyps
	FICE	Disadvantage: No significant difference in ADR	Disadvantage: Inferior to NBI	Advantage: Familiar colour spectrum
	LCI	Advantages: Improves adenoma detection; and effective for non-expert proceduralists1	Disadvantage: Insufficient evidence	Advantage: Familiar colour spectrum
	BLI	Disadvantage: No significant difference in ADR	Advantage: Similar to NBI in terms of colour spectrum and accuracy1	Advantage: Similar colour spectrum to NBI
	TXI	Advantage: Increases polyp visibility in image-based studies	Disadvantage: Insufficient evidence	Disadvantage: Insufficient evidence; advantage: Familiar colour spectrum
AFI		Disadvantage: Insufficient evidence; advantage: Improves detection of flat, right-sided polyps and reduces miss rates	Disadvantage: Inferior to NBI	Disadvantage: Not widely available
AI		Advantage: Increases adenoma detection; no significant difference in withdrawal time1	Advantages: Highly accurate; superior to non-expert endoscopists for histology prediction; not superior to experts using NBI1	Disadvantage: Not yet widely available
FME		Disadvantages: Expensive; insufficient evidence		Disadvantage: Not widely available
Endo-cystoscopy			Neutral: Accurate but requires expertise for interpretation; advantages: Uptake may increase with incorporation of AI	Disadvantages: Requires additional equipment; and not widely available
Multiphoton microscopy			Disadvantage: Insufficient evidence	Disadvantage: Requires additional equipment

¹The most promising technologies.

HD-WLI: High-definition white light imaging; NBI: Narrow-band imaging; BLI: Blue light imaging; TXI: Texture and colour enhancement imaging; FME: Fluorescence molecular endomicroscopy; AFI: Autofluorescence imaging; ADR: Adenoma detection rate; AI: Artificial intelligence; LCI: Linked colour imaging; SSA: Sessile serrated adenomas.