Rationale and Objectives
This study evaluates the validity and reliability of measuring the diameters of the thoracic and abdominal aorta from plain volumetric interpolated breath-hold examination (VIBE) images.
Materials and Methods
The study included 50 male subjects from the population-based Study of Health in Pomerania. They underwent imaging of the thoracic and abdominal aorta at 1.5 Tesla using a contrast-enhanced magnetic resonance angiography (CE-MRA) and plain VIBE sequence. Diameters were measured at five predefined anatomic sites from reformatted orthogonal CE-MRA images and axial plain VIBE images. The measurements were validated using Pearson correlation and Bland-Altman analysis. The Bland-Altman method was also used to assess reliability.
Results
Comparison of the diameters measured from CE-MRA and VIBE images revealed strong correlation for the ascending, descending, suprarenal, and infrarenal aorta with r = 0.95 ( P < .0001), r = 0.88 ( P < .0001), 0.92 ( P < .0001), and 0.87 ( P < .0001), respectively. Measurement for the aortic arch was moderately correlated with r = 0.78 ( P < .0001). Mean bias did not exceed 0.1 cm (6%). The 95% limits of agreement (LOA) were less than 0.5 cm (15%). Intra- and interobserver agreement showed a mean bias of less than 2%; the 95% LOA were less than 11%.
Conclusions
Axial measurement of the diameters of the thoracic and abdominal aorta using a plain axial VIBE sequence is highly valid and reliable, making it suitable for use in epidemiologic research.
Magnetic resonance imaging (MRI) has become increasingly popular in epidemiologic research. Ongoing population-based MRI studies such as the Rotterdam Study, the Multi-Ethnic Study of Atherosclerosis and the Framingham Heart Study include protocols for brain or cardiac MRI . A novel approach is pursued in the Study of Health in Pomerania (SHIP). SHIP is an epidemiologic study that differs from the aforementioned studies in that the examinations performed in a large population of approximately 4000 subjects include a whole-body MRI protocol with optional administration of a contrast agent . The data from such population-based studies can be used to estimate the prevalence and incidence of risk factors and diseases and to identify the complex relationships that exist among them. In addition, such data can be used to measure organ dimensions and define normal values. Of particular interest are the diameters of the thoracic and abdominal aorta. Conditions characterized by dilatation of the aorta such as dissecting or true aortic aneurysm are common and a significant health issue because of a considerable risk of acute and potentially fatal complications. However, no definition exists to distinguish normal diameter variation from a pathologically enlarged aorta . Moreover, many physiologic and pathologic factors affecting aortic diameter have been identified, which are particularly well understood for the thoracic aorta . Recent studies investigating aortic dimensions used computed tomography (CT) or MRI data obtained in small or highly selected samples that are not representative of the general population . Population-based studies with inclusion of a large number of subjects can potentially overcome this lack, providing unbiased estimates of the diameters of the aorta.
In addition, most investigators measured diameters from axial imaging slices, a method that is simple but prone to overestimation compared with orthogonal diameter measurement (perpendicular to blood flow) . Orthogonal measurement requires image postprocessing, which is time-consuming when performed manually and for a large number of datasets. A simple, validated measurement technique is desirable for epidemiologic research. Ideally, such a method should enable measurement from MRI scans obtained without contrast medium administration, because stricter criteria apply to their use in volunteers participating in epidemiologic research .
Get Radiology Tree app to read full this article<
Materials and methods
Study Population and Imaging Protocol
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Table 1
MRI Protocol and Pulse Sequence Parameters Used for Plain and Contrast-enhanced Imaging of the Thoracic and Abdominal Vessels
Sequence TR/TE (ms) Flip Angle (°) Voxel Size (mm) Scan Time (s)VIBE sequence Axial VIBE, thorax 3.1/1.1 8 1.8 × 1.8 × 3.0 21 Axial VIBE, abdomen (two slabs) 7.5/2.4 10 2.4 × 1.6 × 4.0 38CE-MRA Coronal FLASH, thorax 2.5/9.0 25 2.0 × 1.0 × 1.5 11 Coronal FLASH, abdomen 2.5/9.0 25 2.0 × 1.0 × 1.5 12
CE-MRA, contrast-enhanced magnetic resonance angiography; FLASH, fast low-angle shot; MRI, magnetic resonance imaging; TE, echo time; TR, repetition time; VIBE, volumetric interpolated breath-hold examination.
Get Radiology Tree app to read full this article<
Data Analysis and Exclusion Criteria
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Statistical Analysis
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Results
Get Radiology Tree app to read full this article<
Validity Analysis
Get Radiology Tree app to read full this article<
Table 2
Diameters of the Thoracic and Abdominal Aorta at Five Anatomic Sites and Bland-Altman Analysis for Comparison of CE-MRA and VIBE Sequence
CE-MRA (cm) VIBE (cm) Mean Bias; LOA (%) Ascending aorta 3.37 ± 0.38 3.40 ± 0.42 −0.95; −9.24, 5.28 Aortic arch 2.94 ± 0.25 2.84 ± 0.28 3.56; −8.59, 15,71 Descending aorta 2.74 ± 0.28 2.71 ± 0.23 1.39; −10.26, 13.04 Suprarenal aorta 2.35 ± 0.26 2.37 ± 0.28 −0.56; −10.59, 9.47 Infrarenal aorta 1.91 ± 0.16 2.02 ± 0.17 −5.55; −14.29, 3.19
CE-MRA, contrast-enhanced magnetic resonance angiography; LOA, 95% limits of agreement; VIBE, volumetric interpolated breath-hold examination.
Diameters are given as mean and standard deviation.
Get Radiology Tree app to read full this article<
Reliability Analysis
Intraobserver variability
Get Radiology Tree app to read full this article<
Table 3
Intraobserver Analysis for CE-MRA and the VIBE Sequence with Percent Mean Bias and LOA
Observer 1 Observer 2 CE-MRA Mean Bias; LOA (%) Mean Bias; LOA (%) Ascending aorta −0.37; −5.54, 4.79 0.14; −6.32, 6.61 Aortic arch 0.13; −6.75, 7.01 0.74; −7.00, 8.47 Descending aorta −0.28; −6.95, 6.40 0.52; −6.13, 7.18 Suprarenal aorta −0.38; −5.98, 5.21 1.28; −6.32, 8.89 Infrarenal aorta 0.47; −6.17, 7.11 1.32; −5.43, 8.08 VIBE Mean Bias; LOA (%) Mean Bias; LOA (%) Ascending aorta 0.97; −10.45, 12.38 −0.54; −7.10, 6.00 Aortic arch 0.19; −7.04, 7.41 −0.26; −6.92, 6.40 Descending aorta 0.56; −7.70, 8.81 −0.03; −6.22, 6.16 Suprarenal aorta −1.06; −9.42, 7.30 0.85; −7.43, 9.13 Infrarenal aorta −0.74; −9.11, 7.63 0.77; −5.38, 6.91
CE-MRA, contrast-enhanced magnetic resonance angiography; LOA, 95% limits of agreement; VIBE, volumetric interpolated breath-hold examination.
Get Radiology Tree app to read full this article<
Interobserver variability
Get Radiology Tree app to read full this article<
Table 4
Interobserver Analysis for CE-MRA and the VIBE Sequence with Percent Mean Bias and LOA
Observer 1 versus Observer 2 CE-MRA Mean Bias; LOA (%) Ascending aorta −1.61; −6.51, 3.29 Aortic arch −0.19; −5.83, 5.45 Descending aorta −1.00; −6.56, 4.56 Suprarenal aorta 0.12; −6.83, 7.07 Infrarenal aorta −0.10; −6.10, 5.91 VIBE Mean Bias; LOA (%) Ascending aorta −1.16; −7.65, 5.43 Aortic arch 0.87; −5.88, 7.63 Descending aorta 0.22; −6.15, 6.60 Suprarenal aorta −0.22; −9.15, 8.73 Infrarenal aorta −0.72; −7.78, 6.34
CE-MRA, contrast-enhanced magnetic resonance angiography; LOA, 95% limits of agreement; VIBE, volumetric interpolated breath-hold examination.
Get Radiology Tree app to read full this article<
Discussion
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
Acknowledgments
Get Radiology Tree app to read full this article<
Get Radiology Tree app to read full this article<
References
1. Hofman A., Breteler M.M., van Duijn C.M., et. al.: The Rotterdam Study: objectives and design update. Eur J Epidemiol 2007; 22: pp. 819-829.
2. Turkbey E.B., McClelland R.L., Kronmal R.A., et. al.: The impact of obesity on the left ventricle: the Multi-Ethnic Study of Atherosclerosis (MESA). JACC Cardiovasc Imaging 2010; 3: pp. 266-274.
3. Jefferson A.L., Himali J.J., Beiser A.S., et. al.: Cardiac index is associated with brain aging: the Framingham Heart Study. Circulation 2010; 122: pp. 690-697.
4. Hegenscheid K., Kühn J., Völzke H., et. al.: Whole-body magnetic resonance imaging of healthy volunteers: pilot study results from the population-based SHIP Study. Rofo 2009; 181: pp. 748-759.
5. Wanhainen A., Themudo R., Ahlström H., et. al.: Thoracic and abdominal aortic dimension in 70-year-old men and women—a population-based whole-body magnetic resonance imaging (MRI) study. J Vasc Surg 2008; 47: pp. 504-512.
6. Wolak A., Gransar H., Thomson L.E.J., et. al.: Aortic size assessment by noncontrast cardiac computed tomography: normal limits by age, gender, and body surface area. JACC Cardiovasc Imaging 2008; 1: pp. 200-209.
7. Hager A., Kaemmerer H., Rapp-Bernhardt U., et. al.: Diameters of the thoracic aorta throughout life as measured with helical computed tomography. J Thorac Cardiovasc Surg 2002; 123: pp. 1060-1066.
8. Garcier J.-M., Petitcolin V., Filaire M., et. al.: Normal diameter of the thoracic aorta in adults: a magnetic resonance imaging study. Surg Radiol Anat 2003; 25: pp. 322-329.
9. Kaiser T., Kellenberger C.J., Albisetti M., et. al.: Normal values for aortic diameters in children and adolescents—assessment in vivo by contrast-enhanced CMR-angiography. J Cardiovasc Magn Reson 2008; 10: pp. 56.
10. Jaakkola P., Hippeläinen M., Farin P., et. al.: Interobserver variability in measuring the dimensions of the abdominal aorta: comparison of ultrasound and computed tomography. Eu J Vasc Endovasc Surg 1996; 12: pp. 230-237.
11. d’Audiffret A., Desgranges P., Kobeiter D.H., et. al.: Follow-up evaluation of endoluminally treated abdominal aortic aneurysms with duplex ultrasonography: validation with computed tomography. J Vasc Surg 2001; 33: pp. 42-50.
12. Sprouse L.R., Meier G.H., Parent F.N., et. al.: Is ultrasound more accurate than axial computed tomography for determination of maximal abdominal aortic aneurysm diameter?. Eur J Vasc & Endovasc Surg 2004; 28: pp. 28-35.
13. Lin F.Y., Devereux R.B., Roman M.J., et. al.: Assessment of the thoracic aorta by multidetector computed tomography: age- and sex-specific reference values in adults without evident cardiovascular disease. J cardiovasc Computed Tomogr 2008; 2: pp. 298-308.
14. Mao S.S., Ahmadi N., Shah B., et. al.: Normal thoracic aorta diameter on cardiac computed tomography in healthy asymptomatic adults: impact of age and gender. Acad Radiol 2008; 15: pp. 827-834.
15. Rodenwaldt J., Kopka L., Vosshenrich R., et. al.: 3D MR angiography of the entire aorta: modified application of the body-phased array coil for a single-shot technique. Eur J Radiol 2000; 33: pp. 41-49.
16. François C.J., Tuite D., Deshpande V., et. al.: Unenhanced MR angiography of the thoracic aorta: initial clinical evaluation. Am J Roentgenol 2008; 190: pp. 902-906.
17. Kataoka M., Ueda H., Koyama T., et. al.: Contrast-enhanced volumetric interpolated breath-hold examination compared with spin-echo T1-weighted imaging of head and neck tumors. AJR Am J Roentgenol 2005; 184: pp. 313-319.
18. Rofsky N.M., Lee V.S., Laub G., et. al.: Abdominal MR imaging with a volumetric interpolated breath-hold examination. Radiology 1999; 212: pp. 876-884.
19. Biederer J., Graessner J., Heller M.: Magnetic resonance imaging of the lung with a volumetric interpolated 3D-gradient echo sequence. Rofo 2001; 173: pp. 883-887.
20. Groth M., Henes F.O., Mullerleile K., et. al.: Accuracy of thoracic aortic measurements assessed by contrast enhanced and unenhanced magnetic resonance imaging. Eur J Radiol 2012; 81: pp. 762-766.
21. Norman P.E., Muller J., Golledge J.: The cardiovascular and prognostic significance of the infrarenal aortic diameter. J Vasc Surg 2011; 54: pp. 1817-1820.