Terahertz endoscopic imaging for colorectal cancer detection: Current status and future perspectives

Table 1 Merits and demerits of current conventional techniques used in colorectal cancer screening

Test	Advantages	Disadvantages
Flexible sigmoidoscopy	Quick and safe method	Bowel cleansing is required
	Biopsy or polypectomy can be done	Can miss small polyps
	Usually doesn’t require full bowel preparation	Views only the lower third of the colon
	Sedation is not required	Can’t remove all polyps
	Done every 5 yr	If an abnormality is found, colonoscopy will be required
Standard colonoscopy	Very sensitive	Full bowel preparation needed
	Can view entire colon	Can miss small polyps
	Can do biopsy and remove polyps	More expensive
	Can diagnose other diseases	Minor sedation is required
	Done every 10 yr	Small risk of bleeding, bowel tears, or infection
Virtual colonoscopy	Quick and noninvasive	Need full bowel preparation
	Can view entire colon	Cannot detect polyps < 5 mm
	No sedation is needed	Possibility of false positive test results
	Done every 5 yr	Cannot remove polyps
		If an abnormality is found, colonoscopy will be required
Fecal occult blood test	Non-invasive	May miss polyps and cancers that doesn’t cause bleeding
	No bowel preparation is required	Some false positive results
	No sedation is required	Pre-test dietary limitations
	Inexpensive	Should be done every year
	Sampling done at home	If an abnormality is found, colonoscopy will be required

Table 2 The relative reflectance difference between normal and cancerous colonic tissue[42]

Sample #	Co-pol (× 10-1 %)	Cross-pol (%)
Set 1	1.53	7.74
Set 2	3.03	7.74
Set 3	1.56	7.75
Set 4	2.44	7.30