P2369 - Photogrammetry Improves Measurements of Colon Polyps in a 3D Printed Colon Model

Rajiv Perinbasekar, MD, Divyesh Sejpal, MD
Hofstra Northwell Zucker School of Medicine, Manhasset, NY

Introduction: Multiple previous studies have shown that measurements of colon polyps by endoscopists are inaccurate. The purpose of this pilot study was to determine if photogrammetry improves the accuracy of colon polyp measurements without the need for specialized equipment.

Methods: A 3D printed colon model was designed based on standard measurements of an adult colon. Twelve polyps ranging in size from 2 mm to 20 mm were also 3D printed. The polyps were designed to be round and sessile. The polyps were painted and subsequently affixed to the inside of the colon model. Study participants visually estimated the size of each polyp using a pediatric colonoscope. Photographs were then taken of the 3D colon polyps with a standard polypectomy snare in view. Image analysis software was used to measure the pixel length of the tip of the polypectomy snare (2 mm diameter) and the pixel length of each polyp base. The size of each polyp was then calculated using the following formula: Polyp size = Polyp base pixel length / snare pixel length x polypectomy snare diameter (2 mm). Mean estimated polyp size, absolute error, and percent error were calculated for the study group (measurement by visual estimation) and for polyp measurement via photogrammetry. A two tailed t test was used to compare the two groups.

Results: Fifteen endoscopists, including attending gastroenterologists and gastroenterology fellows, participated in this pilot study. The study participants were more accurate when visually estimating the size of small polyps (1 mm to 5 mm, 28.44% percent error) as compared to medium (6 mm to 9 mm, 43.42% percent error) or large polyps (≥ 10 mm, 47.437% percent error). Compared to visual estimation, the photogrammetry method, as described in the methods section, more accurately estimated the size of small polyps (1 mm to 5 mm, 10.69% percent error), medium polyps (6 mm to 9 mm, 6.54% percent error), and large polyps (≥ 10 mm, 6.65% percent error). The results were statistically significant (p = 0.0097).

Discussion: Use of photogrammetry improves the accuracy of colon polyp measurements when compared to visual estimation, especially with medium polyps and large polyps. Since specialized equipment is not required, photogrammetry is an inexpensive and potentially cost-effective method to improve the accuracy of endoscopic measurements, including, but not limited to the measurement of colon polyps. Further study is needed to confirm the accuracy of endoscopic measurements using photogrammetry.



Disclosures:


Rajiv Perinbasekar, MD, Divyesh Sejpal, MD. P2369 - Photogrammetry Improves Measurements of Colon Polyps in a 3D Printed Colon Model, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.