Optimal section thickness for detection of polyps at MR: resolution phantom study.

Area of Science:

• Medical Imaging
• Radiology
• Gastroenterology

Background:

• Magnetic resonance (MR) colonography is an emerging technique for colorectal polyp detection.
• Optimizing MR imaging parameters, such as slice thickness, is crucial for improving diagnostic accuracy and efficiency.

Purpose of the Study:

• To evaluate the sensitivity of MR colonography for detecting simulated polyps of varying sizes and shapes across different slice thicknesses.
• To assess radiologist confidence in polyp detection at different slice thicknesses.
• To determine the impact of slice thickness on image acquisition time.

Main Methods:

• A 3D-printed resolution phantom with sessile, flat, and pedunculated polyps (5-12 mm diameter) was imaged using MR colonography.
• Images were acquired with slice thicknesses of 5 mm, 3 mm, and 1 mm.
• Four radiologists independently reviewed the images, recording polyp detection, maximal diameter, and confidence levels (1-100 scale), alongside image acquisition time.

Main Results:

• All polyps were detected by all readers at 5 mm slice thickness.
• At 3 mm and 1 mm slice thicknesses, 3 out of 4 readers detected all polyps; the fourth reader detected 11/12.
• Reader confidence levels were not significantly different across slice thicknesses (p=0.28), while acquisition time decreased from 3 min 54 s to 41 s as thickness increased from 1 mm to 5 mm.

Conclusions:

• A 5 mm slice thickness is sufficient for identifying 5-12 mm colonic polyps of various morphologies.
• Reducing slice thickness below 5 mm did not enhance detection sensitivity or reader confidence in this phantom study.
• Further optimization of MR colonography sequences, focusing on reducing acquisition time, shows promise for segmental colonic imaging.