CT reconstruction with thick slices not only underestimates lymph node size but also reduces data reproducibility in colorectal cancer. (October 2021)

• Record Type: Journal Article
• Authors: Onuma, Yurina; Tsuruta, Chie; Okita, Kenji; Hamabe, Atsushi; Ogura, Keishi; Takemasa, Ichiro; Hatakenaka, Masamitsu
• Is Part Of: Acta radiologica. Volume 62:Number 10(2021)
• Page Start: 1275
• Page End: 1282
• Publication Date: 2021-10
• Subjects: Computed tomography -- slice thickness -- lymph node -- short-axis diameter -- reproducibility; Radiology, Medical -- Periodicals; Radiography, Medical -- Periodicals; Radiotherapy -- Periodicals; 616.0757
• DOI: 10.1177/0284185120968569
• Languages: English
• ISSNs: 0284-1851

Abstract

Background: Reliable size measurement of lymph node (LN) metastases is important for the evaluation of cancer treatment. However, image analyses without proper settings may result in inappropriate diagnoses and staging. Purpose: To investigate whether reconstruction slice thickness in computed tomography (CT) affects measurements of LN size and reproducibility. Material and Methods: We analyzed 48 patients with histological diagnoses of sigmoid colon and rectal cancer who underwent contrast-enhanced CT colonography as part of a surgical treatment preparation. A board-certified radiologist selected 106 LNs whose short-axis diameter was ≥5 mm on 1-mm-thick images; the short-axis diameters were measured on 1- and 5-mm-thick images by the radiologist and residents and compared using Wilcoxon matched-pairs signed rank test. Data variation and reproducibility were evaluated using the F test and Bland–Altman analysis. P <0.05 was considered significant. Results: Short-axis diameters measured on 5-mm-thick images were significantly lower than those measured on 1-mm-thick images ( P <0.01), even in the LNs whose short-axis diameters were over twice the slice thickness ( P <0.05). Of the 106 LNs, 57 showed short-axis diameter <5 mm on 5-mm-thick images; the maximum short-axis diameter was 6.7 mm on a 1-mm thick image. Data variation was significantly larger on 5-mm thick images than 1-mm-thick images in small LNs ( P <0.05) and reproducibility on 5-mm-thick images was inferior to that on 1-mm-thick images. Conclusion: Thick reconstruction slices in CT can result in an underestimation of LN size and reduce data reproducibility. When measuring LN size, a thin reconstruction slice would be recommended based on targeted LN size.