A technique to identify isoattenuating gallstones with dual-layer spectral CT

An ex vivo phantom study

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Abstract

Background: Previously reported dual-energy CT methods for detecting noncalcified gallstones have reduced accuracy for gallstones smaller than 9 mm. Purpose: To develop a dual-energy CT method for differentiating isoattenuating gallstones from bile and compare it with previously reported dual-energy CT methods by using a prospective ex vivo phantom reader study. Materials and Methods: From May 2017 to May 2018, gallstones were collected from 105 patients (34 men; mean age, 51 years; age range, 18–84 years) undergoing cholecystectomy and placed inside 120-mL vials containing ox bile. The vials were placed inside a water-filled phantom and were scanned with dual-layer dual-energy CT. Thirty isoattenuating gallstones (4.3–24.7 mm in diameter) were evaluated. Conventional CT images, virtual noncontrast images, and monoenergetic images at 200 and 40 keV were created. Segmented images were created by using a two-dimensional histogram of Compton and photoelectric attenuation. Six readers evaluated the presence of isoattenuating gallstones in each image. Intra- and interreader agreement was measured by using percentage agreement, diagnostic performance was evaluated by using mean area under the receiver operating characteristic curve (AUC) estimates and pairwise comparisons, and the agreement of gallstone sizes measured at pathologic examination with those measured on segmented images was compared by using Bland-Altman analysis. Results: For all gallstones, segmented images provided the highest mean intrareader (88.1%) and interreader (88.2% and 93.6%) agreements for all readers and reading sessions and the highest overall AUC (0.99; 95% confidence interval [CI]: 0.97, 1.00; adjusted P , .02 for all). For gallstones larger than 9 mm, no significant difference was found between the segmented and monoenergetic AUCs (all P . .94, adjusted P . .05 for all). For gallstones measuring 9 mm or smaller, the segmented images had the highest overall AUC (0.99; 95% CI: 0.97, 1.00; adjusted P , .01 for all). The mean difference in stone sizes was 20.6 mm, with limits of agreement from 2.6 to 23.8 mm. Conclusion: Segmented images from Compton and photoelectric attenuation coefficients improve detection of isoattenuating gallstones compared with previously reported dual-energy CT methods.

Original languageEnglish (US)
Pages (from-to)400-406
Number of pages7
JournalRadiology
Volume292
Issue number2
DOIs
StatePublished - Jan 1 2019

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Gallstones
Area Under Curve
Bile
Confidence Intervals
Cholecystectomy
ROC Curve
Reading

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

Cite this

@article{ba812de827804c49be5636d9fd3a6e04,
title = "A technique to identify isoattenuating gallstones with dual-layer spectral CT: An ex vivo phantom study",
abstract = "Background: Previously reported dual-energy CT methods for detecting noncalcified gallstones have reduced accuracy for gallstones smaller than 9 mm. Purpose: To develop a dual-energy CT method for differentiating isoattenuating gallstones from bile and compare it with previously reported dual-energy CT methods by using a prospective ex vivo phantom reader study. Materials and Methods: From May 2017 to May 2018, gallstones were collected from 105 patients (34 men; mean age, 51 years; age range, 18–84 years) undergoing cholecystectomy and placed inside 120-mL vials containing ox bile. The vials were placed inside a water-filled phantom and were scanned with dual-layer dual-energy CT. Thirty isoattenuating gallstones (4.3–24.7 mm in diameter) were evaluated. Conventional CT images, virtual noncontrast images, and monoenergetic images at 200 and 40 keV were created. Segmented images were created by using a two-dimensional histogram of Compton and photoelectric attenuation. Six readers evaluated the presence of isoattenuating gallstones in each image. Intra- and interreader agreement was measured by using percentage agreement, diagnostic performance was evaluated by using mean area under the receiver operating characteristic curve (AUC) estimates and pairwise comparisons, and the agreement of gallstone sizes measured at pathologic examination with those measured on segmented images was compared by using Bland-Altman analysis. Results: For all gallstones, segmented images provided the highest mean intrareader (88.1{\%}) and interreader (88.2{\%} and 93.6{\%}) agreements for all readers and reading sessions and the highest overall AUC (0.99; 95{\%} confidence interval [CI]: 0.97, 1.00; adjusted P , .02 for all). For gallstones larger than 9 mm, no significant difference was found between the segmented and monoenergetic AUCs (all P . .94, adjusted P . .05 for all). For gallstones measuring 9 mm or smaller, the segmented images had the highest overall AUC (0.99; 95{\%} CI: 0.97, 1.00; adjusted P , .01 for all). The mean difference in stone sizes was 20.6 mm, with limits of agreement from 2.6 to 23.8 mm. Conclusion: Segmented images from Compton and photoelectric attenuation coefficients improve detection of isoattenuating gallstones compared with previously reported dual-energy CT methods.",
author = "Soesbe, {Todd C} and Lewis, {Matthew A} and Yin Xi and Browning, {Travis G} and Lakshmi Ananthakrishnan and Julia Fielding and Lenkinski, {Robert E} and John Leyendecker",
year = "2019",
month = "1",
day = "1",
doi = "10.1148/radiol.2019190083",
language = "English (US)",
volume = "292",
pages = "400--406",
journal = "Radiology",
issn = "0033-8419",
publisher = "Radiological Society of North America Inc.",
number = "2",

}

TY - JOUR

T1 - A technique to identify isoattenuating gallstones with dual-layer spectral CT

T2 - An ex vivo phantom study

AU - Soesbe, Todd C

AU - Lewis, Matthew A

AU - Xi, Yin

AU - Browning, Travis G

AU - Ananthakrishnan, Lakshmi

AU - Fielding, Julia

AU - Lenkinski, Robert E

AU - Leyendecker, John

PY - 2019/1/1

Y1 - 2019/1/1

N2 - Background: Previously reported dual-energy CT methods for detecting noncalcified gallstones have reduced accuracy for gallstones smaller than 9 mm. Purpose: To develop a dual-energy CT method for differentiating isoattenuating gallstones from bile and compare it with previously reported dual-energy CT methods by using a prospective ex vivo phantom reader study. Materials and Methods: From May 2017 to May 2018, gallstones were collected from 105 patients (34 men; mean age, 51 years; age range, 18–84 years) undergoing cholecystectomy and placed inside 120-mL vials containing ox bile. The vials were placed inside a water-filled phantom and were scanned with dual-layer dual-energy CT. Thirty isoattenuating gallstones (4.3–24.7 mm in diameter) were evaluated. Conventional CT images, virtual noncontrast images, and monoenergetic images at 200 and 40 keV were created. Segmented images were created by using a two-dimensional histogram of Compton and photoelectric attenuation. Six readers evaluated the presence of isoattenuating gallstones in each image. Intra- and interreader agreement was measured by using percentage agreement, diagnostic performance was evaluated by using mean area under the receiver operating characteristic curve (AUC) estimates and pairwise comparisons, and the agreement of gallstone sizes measured at pathologic examination with those measured on segmented images was compared by using Bland-Altman analysis. Results: For all gallstones, segmented images provided the highest mean intrareader (88.1%) and interreader (88.2% and 93.6%) agreements for all readers and reading sessions and the highest overall AUC (0.99; 95% confidence interval [CI]: 0.97, 1.00; adjusted P , .02 for all). For gallstones larger than 9 mm, no significant difference was found between the segmented and monoenergetic AUCs (all P . .94, adjusted P . .05 for all). For gallstones measuring 9 mm or smaller, the segmented images had the highest overall AUC (0.99; 95% CI: 0.97, 1.00; adjusted P , .01 for all). The mean difference in stone sizes was 20.6 mm, with limits of agreement from 2.6 to 23.8 mm. Conclusion: Segmented images from Compton and photoelectric attenuation coefficients improve detection of isoattenuating gallstones compared with previously reported dual-energy CT methods.

AB - Background: Previously reported dual-energy CT methods for detecting noncalcified gallstones have reduced accuracy for gallstones smaller than 9 mm. Purpose: To develop a dual-energy CT method for differentiating isoattenuating gallstones from bile and compare it with previously reported dual-energy CT methods by using a prospective ex vivo phantom reader study. Materials and Methods: From May 2017 to May 2018, gallstones were collected from 105 patients (34 men; mean age, 51 years; age range, 18–84 years) undergoing cholecystectomy and placed inside 120-mL vials containing ox bile. The vials were placed inside a water-filled phantom and were scanned with dual-layer dual-energy CT. Thirty isoattenuating gallstones (4.3–24.7 mm in diameter) were evaluated. Conventional CT images, virtual noncontrast images, and monoenergetic images at 200 and 40 keV were created. Segmented images were created by using a two-dimensional histogram of Compton and photoelectric attenuation. Six readers evaluated the presence of isoattenuating gallstones in each image. Intra- and interreader agreement was measured by using percentage agreement, diagnostic performance was evaluated by using mean area under the receiver operating characteristic curve (AUC) estimates and pairwise comparisons, and the agreement of gallstone sizes measured at pathologic examination with those measured on segmented images was compared by using Bland-Altman analysis. Results: For all gallstones, segmented images provided the highest mean intrareader (88.1%) and interreader (88.2% and 93.6%) agreements for all readers and reading sessions and the highest overall AUC (0.99; 95% confidence interval [CI]: 0.97, 1.00; adjusted P , .02 for all). For gallstones larger than 9 mm, no significant difference was found between the segmented and monoenergetic AUCs (all P . .94, adjusted P . .05 for all). For gallstones measuring 9 mm or smaller, the segmented images had the highest overall AUC (0.99; 95% CI: 0.97, 1.00; adjusted P , .01 for all). The mean difference in stone sizes was 20.6 mm, with limits of agreement from 2.6 to 23.8 mm. Conclusion: Segmented images from Compton and photoelectric attenuation coefficients improve detection of isoattenuating gallstones compared with previously reported dual-energy CT methods.

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U2 - 10.1148/radiol.2019190083

DO - 10.1148/radiol.2019190083

M3 - Article

VL - 292

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JO - Radiology

JF - Radiology

SN - 0033-8419

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