Musculoskeletal Research Resources at the Institute for Aging Research

Musculoskeletal Research Resources

Radiographic Atlas of Location, Severity and Progression of Calcific Lesions in the Abdominal Aorta
D. P. Kiel, S. P. Menn, and D. E. Karasik
 

Institute for Aging Research
Hebrew SeniorLife
Harvard Medical School, Division on Aging

1200 Centre Street
Boston, MA 02131

Phone: 617-971-5365
Fax: 617 971-5339

e-mail: kiel@hsl.harvard.edu | David Karasik 

Introduction

The presence of calcified lesions in the abdominal aorta has been found to predict various cardiovascular events [1,2] and correlates with degenerative changes in the lumbar spine [3]. However, no standardized method to assess the location and progression of such lesions has been available and few studies [4,5] have attempted to assess the severity of aortic calcifications from lateral abdominal radiographs. A grading system has been developed, which allows both localization of

calcifications in different segments of the abdominal aorta and quantification of the calcifications.  This facilitates assessments of severity and progression of calcific lesions.

Method

To evaluate calcific deposits in the abdominal aorta, Kauppila et al. [1997] developed new indices of the location and severity of calcifications. Our approach was to assess both the location and severity of calcific deposits in relation to segmental lumbar arteries by assessing aortic calcifications at each vertebral segment. All assessments were carried out in a darkened room with a standard radiographic-viewing, backlit box.  Calcific deposits were regarded as present if densities were visible in an area parallel and anterior to the lumbar spine. Aortic densities at the upper part of the lumbar spine often overlapped the vertebrae, as the abdominal aorta in the L1-L2 region is often lateral to the spine, while the lower abdominal aorta in the L3 and L4 region is situated anterior to the spine. Densities overlapping the vertebrae were scored present only if they extended from or formed a clear pattern with those of the lower part of the aorta. Since calcific deposits tend to occur first in the lower aorta [6,7], calcific deposits at upper levels were almost always accompanied by extensive calcifications in the lower part of the aorta (Fig. 1). Other calcific deposits visible in lumbar films, such as intestinal calcifications and calcified costal cartilages, are usually distinguishable from aortic calcifications in most radiographs.

Calcific deposits in the abdominal aorta adjacent to each lumbar vertebra were individually assessed for the posterior and anterior wall of the aorta using the midpoint of the intervertebral space above and below the vertebrae as the boundaries. Lesions were graded as follows: 0, no aortic calcific deposits; 1, small scattered calcific deposits filling less than one third of the longitudinal wall of the aorta; 2, one third or more, but less than two thirds of the longitudinal wall of the aorta calcified; 3, two thirds or more of the longitudinal wall of the aorta calcified (Fig. 1) .

Individual level-specific severity scores were summarized to yield a composite score for aortic calcifications, the antero-posterior severity score (0-24), in which the scores of individual aortic segments both for the posterior and anterior wall were summed (Fig. 2) .

The lateral two-dimensional projection of the lumbar spine and abdominal aorta creates two basic appearances of calcific deposits in the aorta.  In some instances the anterior and/or posterior wall of the aorta display linear sharply distinct deposits.  Often, however, the calcific deposits are circumferential.  This creates a hazy, "ground-glass" appearance to the deposits without necessarily including the distinct linear dense stripes of calcium.  Grading for the presence of calcific deposits uses the above criteria regardless of the appearance of the deposits.  Thus, if the hazy, ground-glass pattern extends over an entire vertebral segment the segment would be scored as "3" anteriorly and "3" posteriorly.

The Appearance of "Ground Glass"  

"Ground-glass" may sometimes be better appreciated from a distance. In some instances, the ground-glass appears as a solid homogenous pipe-like tubular appearance, while at other times it may appear as a non-homogenous and patchy cloud.
The Aortic Bifurcation 

The aorta occasionally bifurcates at the L4 level. Sometimes calcification of this bifurcation is visible.  This may appear as a vertical line of calcification halfway between the anterior and posterior lines above it or in some cases as three vertical lines adjacent to L4. In such cases, a category, ‘middle' wall should be used; however, the total score for the aorta adjacent to the L4 vertebra should not exceed a total of 6.

Distinguishing Artifacts from Aortic Calcification 

Artifacts such as gas, ribs or stool may sometimes appear as white linear marks resembling  aortic calcification.  If they appear as contiguous continuations of linear deposits above or below, it is likely that they are true calcifications. Comparing the intensity/denseness and the shape may help distinguish a true calcification from a simple artifact.  For example, calcifications that are round, non-linear, or extending in a non-vertical direction may not be in the aorta, but rather part of another structure such as a rib.  Occasionally one can see the cross-section of a smaller vessel branching from the aorta; however, these were never counted in the aortic calcification score.  Finally, due to anatomic variation and rotation (oblique X-ray angle), vascular calcification may be superimposed on vertebral bodies themselves.

Procedure for Approaching Longitudinal Film Sets 

In the case of longitudinal films, these should be read side-by-side to minimize technical difficulties.

Acknowledgments  
We gratefully acknowledge the participants of the Framingham Heart Study whose radiographs were used in this atlas. We would like to express our thanks to Mr. Alik Kogan for creation of this web page and Ms. Aleksandra Brenckle for her help in acquiring images and technical assistance.
 
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