A structured light laser probe for gastrointestinal polyp size measurement: a preliminary comparative study

Abstract

Background and study aims Polyp size measurement is an important diagnostic step during gastrointestinal endoscopy, and is mainly performed by visual inspection. However, lack of depth perception and objective reference points are acknowledged factors contributing to measurement errors in polyp size. In this paper, we describe the proof-of-concept of a polyp measurement device based on structured light technology for future endoscopes.

Patients and methods Measurement accuracy, time, user confidence, and satisfaction were evaluated for polyp size assessment by (a) visual inspection, (b) open biopsy forceps of known size, (c) ruled snare, and (d) structured light probe, for a total of 392 independent polyp measurements in ex vivo porcine stomachs.

Results Visual assessment resulted in a median estimation error of 2.2 mm, IQR = 2.6 mm. The proposed probe can reduce the error to 1.5 mm, IQR = 1.67 mm (P = 0.002, 95 %CI) and its performance was found to be statistically similar to using forceps for reference (P = 0.81, 95 %CI) or ruled snare (P = 0.99, 95 %CI), while not occluding the tool channel. Timing performance with the probe was measured to be on average 54.75 seconds per polyp. This was significantly slower than visual assessment (20.7 seconds per polyp, P = 0.005, 95 %CI) but not significantly different from using a snare (68.5 seconds per polyp, P = 0.73, 95 %CI). However, the probe’s timing performance was partly due to lens cleaning problems in our preliminary design. Reported average satisfaction on a 0 – 10 range was highest for the proposed probe (7.92), visual assessment (7.01), and reference forceps (7.82), while significantly lower for snare users with a score of 4.42 (P = 0.035, 95 %CI).

Conclusions The common practice of visual assessment of polyp size was found to be significantly less accurate than tool-based assessment, but easy to carry out. The proposed technology offers an accuracy on par with using a reference tool or ruled snare with the same satisfaction levels of visual assessment and without occluding the tool channel. Further study will improve the design to reduce the operating time by integrating the probe within the scope tip.

• References

• 1 Levin B, Lieberman DA, McFarland B. et al. Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US MultiSociety Task Force on Colorectal Cancer, and the American College of Radiology. Gastroenterology 2008; 134: 1570-1595
• 2 Lieberman DA, Rex DK, Winawer SJ. et al. Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer. Gastroenterology 2012; 143: 844-857
• 3 Hassan C, Quintero E, Dumonceau JM. et al. Post-polypectomy colonoscopy surveillance: European Society of Gastrointestinal Endoscopy (ESGE) guideline. Endoscopy 2013; 45: 842-851
• 4 Pickhardt PJ. The natural history of colorectal polyps and masses: rediscovered truths from the barium enema era. AJR Am J Roentgenol 2007; 188: 619-621
• 5 Fennerty MB, Davidson J, Emerson SS. et al. Are endoscopic measurements of colonic polyps reliable?. Am J Gastroenterol 1993; 88: 496-500
• 6 Moug SJ, Vernall N, Saldanha J. et al. Endoscopists’ estimation of size should not determine surveillance of colonic polyps. Colorectal Dis 2010; 12: 646-650
• 7 Gupta S, Balasubramanian BA, Fu T. et al. Polyps with advanced neoplasia are smaller in the right than in the left colon: implications for colorectal cancer screening. Clin Gastroenterol Hepatol 2012; 10: 1395-1401.e2
• 8 Hyun YS, Han DS, Bae JH. et al. Graduated injection needles and snares for polypectomy are useful for measuring colorectal polyp size. Dig Liver Dis 2011; 43: 3914
• 9 Kaz AM, Anwar A, O’Neill DR. et al. Use of a novel polyp “ruler snare” improves estimation of colon polyp size. Gastrointest Endosc 2016; 83: 812-816
• 10 Gopalswamy N, Shenoy VN, Choudhry U. et al. Is in vivo measurement of size of polyps during colonoscopy accurate?. Gastrointest Endosc 1997; 46: 497-502
• 11 Izzy M, Virk MA, Saund A. et al. Accuracy of endoscopists’ estimate of polyp size: A continuous dilemma. World J Gastrointest Endosc 2015; 7: 824-829
• 12 Bernal J, Tajkbaksh N, Sanchez JF. et al. Comparative validation of polyp detection methods in video colonoscopy: results from the MICCAI 2015 Endoscopic Vision Challenge. IEEE Trans Med Imaging 2017; 36: 1231-1249
• 13 Maier-Hein L, Mountney P, Bartoli A. et al. Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic surgery. Med Image Anal 2013; 17: 974-996
• 14 Furukawa R, Sanomura Y, Tanaka S. 3D endoscope system using DOE projector. IEEE International Conference of the Engineering in Medicine and Biology Society (EMBC), Orlando, FL, USA. 2016
• 15 Furukawa R, Aoyama M, Hiura S. et al. Calibration of a 3D endoscopic system based on active stereo method for shape measurement of biological tissue and specimen. IEEE International Conference of the Engineering in Medicine and Biology Society (EMBC), Chicago, IL, USA. 2014