Variability of maximal aortic aneurysm diameter measurements on CT scan

Significance and methods to minimize

Neal S. Cayne, Frank J. Veith, Evan C. Lipsitz, Takao Ohki, Manish Mehta, Nick Gargiulo, William D. Suggs, Alla Rozenblit, Zina Ricci, Carlos H. Timaran

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

Objectives: We noted substantial differences when measuring repeatedly the same abdominal aortic aneurysm (AAA) on the same computed tomography (CT) scan. This study quantitated this variability, and methods to minimize it were developed. Methods: The CT maximal diameter of 25 AAAs was measured by eight experienced observers, including six vascular surgeons and two radiologists, using two methods: an unstandardized protocol, and a standardized protocol using fine calipers to carefully measure the largest diameter perpendicular to the estimated aneurysm centerline, from outer aneurysm wall to outer wall. The average measurement difference between observers was calculated for each method. The average difference between each observer's measurement and the official radiology report value was also calculated. Agreement between the two measurement methods was assessed with Bland-Altman plots. Results: The difference in maximal diameter measurements between each observer averaged 4.0 ± 5.1 mm (range, 0.0-35.0 mm) with the unstandardized method. The mean measurement difference with the standardized protocol was significantly lower, and averaged 2.8 ± 4.4 mm (range, 0.0-26.0 mm; P < .05). Measurements taken from the official radiology report differed from each of the observer's standardized measurement by an average of 5.0 ± 6.3 mm (range, 0.0-28.0 mm). This difference was similar for both the unstandardized and standardized methods. Bland-Altman plots confirmed the wide variation of the maximal diameter measurements when the unstandardized method was compared with the standardized method (95% confidence interval, -9-9 mm). Conclusions: Routine CT maximal diameter measurement of AAAs can have substantial interobserver variability. Standardized measurement protocols can decrease, but not eliminate, this measurement variability. Thus apparent size changes based on CT measurements may represent measurement artifact rather than actual aneurysm growth or shrinkage, particularly when a standardized system is not used.

Original languageEnglish (US)
Pages (from-to)811-815
Number of pages5
JournalJournal of Vascular Surgery
Volume39
Issue number4
DOIs
StatePublished - Apr 2004

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Aortic Aneurysm
Tomography
Aneurysm
Radiology
Observer Variation
Abdominal Aortic Aneurysm
Artifacts
Blood Vessels
Confidence Intervals

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Surgery

Cite this

Variability of maximal aortic aneurysm diameter measurements on CT scan : Significance and methods to minimize. / Cayne, Neal S.; Veith, Frank J.; Lipsitz, Evan C.; Ohki, Takao; Mehta, Manish; Gargiulo, Nick; Suggs, William D.; Rozenblit, Alla; Ricci, Zina; Timaran, Carlos H.

In: Journal of Vascular Surgery, Vol. 39, No. 4, 04.2004, p. 811-815.

Research output: Contribution to journalArticle

Cayne, Neal S. ; Veith, Frank J. ; Lipsitz, Evan C. ; Ohki, Takao ; Mehta, Manish ; Gargiulo, Nick ; Suggs, William D. ; Rozenblit, Alla ; Ricci, Zina ; Timaran, Carlos H. / Variability of maximal aortic aneurysm diameter measurements on CT scan : Significance and methods to minimize. In: Journal of Vascular Surgery. 2004 ; Vol. 39, No. 4. pp. 811-815.
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abstract = "Objectives: We noted substantial differences when measuring repeatedly the same abdominal aortic aneurysm (AAA) on the same computed tomography (CT) scan. This study quantitated this variability, and methods to minimize it were developed. Methods: The CT maximal diameter of 25 AAAs was measured by eight experienced observers, including six vascular surgeons and two radiologists, using two methods: an unstandardized protocol, and a standardized protocol using fine calipers to carefully measure the largest diameter perpendicular to the estimated aneurysm centerline, from outer aneurysm wall to outer wall. The average measurement difference between observers was calculated for each method. The average difference between each observer's measurement and the official radiology report value was also calculated. Agreement between the two measurement methods was assessed with Bland-Altman plots. Results: The difference in maximal diameter measurements between each observer averaged 4.0 ± 5.1 mm (range, 0.0-35.0 mm) with the unstandardized method. The mean measurement difference with the standardized protocol was significantly lower, and averaged 2.8 ± 4.4 mm (range, 0.0-26.0 mm; P < .05). Measurements taken from the official radiology report differed from each of the observer's standardized measurement by an average of 5.0 ± 6.3 mm (range, 0.0-28.0 mm). This difference was similar for both the unstandardized and standardized methods. Bland-Altman plots confirmed the wide variation of the maximal diameter measurements when the unstandardized method was compared with the standardized method (95{\%} confidence interval, -9-9 mm). Conclusions: Routine CT maximal diameter measurement of AAAs can have substantial interobserver variability. Standardized measurement protocols can decrease, but not eliminate, this measurement variability. Thus apparent size changes based on CT measurements may represent measurement artifact rather than actual aneurysm growth or shrinkage, particularly when a standardized system is not used.",
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T2 - Significance and methods to minimize

AU - Cayne, Neal S.

AU - Veith, Frank J.

AU - Lipsitz, Evan C.

AU - Ohki, Takao

AU - Mehta, Manish

AU - Gargiulo, Nick

AU - Suggs, William D.

AU - Rozenblit, Alla

AU - Ricci, Zina

AU - Timaran, Carlos H.

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N2 - Objectives: We noted substantial differences when measuring repeatedly the same abdominal aortic aneurysm (AAA) on the same computed tomography (CT) scan. This study quantitated this variability, and methods to minimize it were developed. Methods: The CT maximal diameter of 25 AAAs was measured by eight experienced observers, including six vascular surgeons and two radiologists, using two methods: an unstandardized protocol, and a standardized protocol using fine calipers to carefully measure the largest diameter perpendicular to the estimated aneurysm centerline, from outer aneurysm wall to outer wall. The average measurement difference between observers was calculated for each method. The average difference between each observer's measurement and the official radiology report value was also calculated. Agreement between the two measurement methods was assessed with Bland-Altman plots. Results: The difference in maximal diameter measurements between each observer averaged 4.0 ± 5.1 mm (range, 0.0-35.0 mm) with the unstandardized method. The mean measurement difference with the standardized protocol was significantly lower, and averaged 2.8 ± 4.4 mm (range, 0.0-26.0 mm; P < .05). Measurements taken from the official radiology report differed from each of the observer's standardized measurement by an average of 5.0 ± 6.3 mm (range, 0.0-28.0 mm). This difference was similar for both the unstandardized and standardized methods. Bland-Altman plots confirmed the wide variation of the maximal diameter measurements when the unstandardized method was compared with the standardized method (95% confidence interval, -9-9 mm). Conclusions: Routine CT maximal diameter measurement of AAAs can have substantial interobserver variability. Standardized measurement protocols can decrease, but not eliminate, this measurement variability. Thus apparent size changes based on CT measurements may represent measurement artifact rather than actual aneurysm growth or shrinkage, particularly when a standardized system is not used.

AB - Objectives: We noted substantial differences when measuring repeatedly the same abdominal aortic aneurysm (AAA) on the same computed tomography (CT) scan. This study quantitated this variability, and methods to minimize it were developed. Methods: The CT maximal diameter of 25 AAAs was measured by eight experienced observers, including six vascular surgeons and two radiologists, using two methods: an unstandardized protocol, and a standardized protocol using fine calipers to carefully measure the largest diameter perpendicular to the estimated aneurysm centerline, from outer aneurysm wall to outer wall. The average measurement difference between observers was calculated for each method. The average difference between each observer's measurement and the official radiology report value was also calculated. Agreement between the two measurement methods was assessed with Bland-Altman plots. Results: The difference in maximal diameter measurements between each observer averaged 4.0 ± 5.1 mm (range, 0.0-35.0 mm) with the unstandardized method. The mean measurement difference with the standardized protocol was significantly lower, and averaged 2.8 ± 4.4 mm (range, 0.0-26.0 mm; P < .05). Measurements taken from the official radiology report differed from each of the observer's standardized measurement by an average of 5.0 ± 6.3 mm (range, 0.0-28.0 mm). This difference was similar for both the unstandardized and standardized methods. Bland-Altman plots confirmed the wide variation of the maximal diameter measurements when the unstandardized method was compared with the standardized method (95% confidence interval, -9-9 mm). Conclusions: Routine CT maximal diameter measurement of AAAs can have substantial interobserver variability. Standardized measurement protocols can decrease, but not eliminate, this measurement variability. Thus apparent size changes based on CT measurements may represent measurement artifact rather than actual aneurysm growth or shrinkage, particularly when a standardized system is not used.

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