Prevalence of Significant Noncardiac Findings on Electron-Beam Computed Tomography Coronary Artery Calcium Screening Examinations
Background— Screening electron-beam computed tomography (EBCT) examinations for the detection and quantification of coronary artery calcification are being performed throughout the country. In addition to information about the heart, great vessels, and coronary arteries, these examinations include portions of the lungs, bony thorax, and upper abdomen. The purpose of this study was to determine the prevalence of significant noncardiac findings in a series of patients undergoing coronary artery calcification screening studies with EBCT scanning.
Methods and Results— Between January 1, 2001, and October 1, 2001, 1326 consecutive patients underwent coronary artery calcification screening with EBCT (3-mm-thick slices were obtained at 3-mm intervals). Two board-certified radiologists reviewed the examinations on a workstation using standard mediastinal windows, lung windows, and bone windows. Significant extracardiac abnormalities were noted. Of 1326 patients, 103 (7.8%) had significant extracardiac pathology requiring clinical or imaging follow-up. These included 53 patients with noncalcified lung nodules <1 cm, 12 patients with lung nodules ≥1 cm, 24 patients with infiltrates, 7 patients with indeterminate liver lesions, 2 patients with sclerotic bone lesions, 2 patients with breast abnormalities, 1 patient with polycystic liver disease, 1 patient with esophageal thickening, and 1 patient with ascites.
Conclusions— In this study, 7.8% of patients undergoing screening EBCT examinations for coronary artery calcification were found to have important extracardiac pathology requiring additional work-up. Therefore, it is essential that a radiologist review the entire examination.
Received April 29, 2002; revision received June 7, 2002; accepted June 10, 2002.
Electron-beam computed tomography (EBCT) as well as multidetector-row computed tomography (MDCT) scanners can be used for detection and quantification of coronary artery calcification.1–4⇓⇓⇓ Coronary artery calcification is a marker for atherosclerosis, and the coronary artery calcification score, established by Agaston et al,1 has been shown to be an accurate measure of coronary plaque burden and a potent predictor of future cardiac events.5–7⇓⇓ Therefore, on the basis of this research and because of the increasing availability of EBCT and MDCT, these examinations are being performed with increasing frequency.
In addition to information about the heart, great vessels, and coronary arteries, these examinations include portions of the lungs, chest wall, spine, and upper abdomen. The purpose of this study was to determine the prevalence of significant noncardiac findings in a series of patients undergoing EBCT of the heart for coronary artery calcification scoring.
The study group consisted of 1326 consecutive patients who underwent EBCT of the coronary arteries between January 1, 2001, and October 1, 2001 at a single screening center in Maryland (Lifetest, Baltimore, Md). These patients represented a mixture of asymptomatic self-referrals, asymptomatic individuals referred by their primary care physicians, and symptomatic patients referred by either primary care physicians or cardiologists. These examinations were clinical screening studies. There were 849 male and 477 female subjects with an average age of 55.4 years (range, 23 to 87 years). Nine hundred ninety-four (75%) patients were nonsmokers, 89 (6.7%) patients were active smokers, and 243 (18.3%) patients were former smokers.
All scans were performed with an Imatron (Imatron Inc) EBCT scanner, using single breath-hold and ECG triggering. Patients were scanned in the supine position from the level of the pulmonary arteries through the base of the heart using a 350-mm field of view with a 512×512 reconstruction matrix. Slices 3 mm in size were obtained every 3 mm with an image acquisition time of 100 ms.
All examinations were transferred to a Dell workstation (Dell Computer) with Accuview software (AccuImage). Examinations were reviewed prospectively by one of two experienced CT radiologists (K.M.H. or E.K.F.). All images were reviewed in standard mediastinal windows (400W/40C), lung windows (1700W/−500C), and bone windows (2500W/500C). All abnormalities were reported. Patients with significant noncardiac radiological findings were identified. Significant findings were defined as abnormalities that required additional clinical or radiological follow-up. Findings such as scars, pleural thickening, calcified nodes, and calcified granulomata were not considered to be significant and were therefore not included in this study.
Of 1326 patients, 103 (7.8%) had significant extracardiac pathology requiring clinical or imaging follow-up. These included 53 patients with noncalcified lung nodules <1 cm, 12 patients with lung nodules ≥1 cm, 24 patients with infiltrates, 7 patients with indeterminate liver lesions, 2 patients with sclerotic bone lesions, 2 patients with breast abnormalities, 1 patient with polycystic liver disease, 1 patient with suspicious esophageal thickening, and 1 patient with ascites.
CT examinations of the heart are being performed with increasing frequency throughout the country as a method to screen for atherosclerosis of the coronary arteries. Although these studies initially required the use of electron-beam technology, improvements in CT technology allow coronary artery calcium scoring examinations to be performed on more affordable and versatile MDCT scanners.3,4⇓
Many of these screening cardiac CT studies are interpreted by cardiologists who evaluate the heart and calculate the coronary artery calcium score. However, in addition to information about the heart, these examinations (with a 350-mm field of view) include portions of the lungs, bony thorax, and sometimes upper abdomen. Using this field of view, most of the right and left lung over that section is visualized, although the lateral-most portions of the left lung are truncated in some patients. It is possible to change the field of view so that both lungs can been seen in their entirety through the section, although this requires extra work and is probably not necessary.
In this study, 7.8% of patients undergoing screening EBCT examinations for coronary artery calcification were found to have significant extracardiac pathology requiring additional work-up.
There is very little in the literature about the prevalence of noncardiac abnormalities in cardiac CT studies. Only one relevant study has been published. In a study by Hunold et al8 of 1812 consecutive patients undergoing EBCT cardiac studies, the authors reviewed only the mediastinal windows for extracardiac pathology and found lung abnormalities in 28%, abdominal abnormalities in 2%, mediastinal pathology in 4%, and spine abnormalities in 5%. These abnormalities included a large number of minor, relatively insignificant abnormalities, such as scars, granulomata, atelectasis, degenerative arthritis, and rib fractures.8 In that study, nodules were found in only 1.1%, which is a lower percentage than that found in our study. However, in the study by Hunold et al, lung windows were not reviewed, and, therefore, the actual number of lung nodules present is not known. In our study, 65 patients (5%) had one or more noncalcified lung nodules. In comparison with the early lung cancer lung project, in which 23% of patients undergoing full-chest CT scanning demonstrated noncalcified lung nodules,9,10⇓ our study only detected noncalcified nodules in 65 of 1326 of patients (5%). However, a cardiac CT scan only images ≈30% of the lungs; also, in our study, only 25% of patients were active or former smokers, compared with 100% in the early lung cancer project. In our experience, characterization of lung nodules was adequate with EBCT, and, therefore, it was not necessary to recommend conventional CT scanning in cases of small nodules. Larger nodules (≥1 cm) or suspicious nodules with spiculation would benefit from conventional spiral CT scanning with IV contrast for additional characterization and for the detection of possible adenopathy or metastases.
One potential limitation of our study is the lack of follow-up on the patients. Following lung nodules, for example, is difficult and requires demonstration of stability over 2 years, and therefore, complete follow-up will not be available for a considerable amount of time. However, it was not the goal of the study to follow the outcome of the abnormalities detected. The primary goal of this study was to determine the prevalence of significant noncardiac findings, which, according to present standard radiological practice, requires additional clinical or radiological follow-up. On the basis of lung cancer screening studies, it is accepted that most nodules that are detected will be benign. However, presently, the only way to ensure that a small nodule is benign is to either resect the nodule or monitor it over time.11
We are attempting to follow up abnormalities detected in the first group of 581 patients scanned between January 1, 2001, and May 1, 2001. That group of patients included 12 patients with nodules measuring <1 cm, 3 patients with nodules ≥1 cm, 6 patients with infiltrates, 2 patients with bone lesions, 2 patients with liver lesions, 2 patients with breast abnormalities, 1 patient with polycystic liver disease, and 1 patient with ascites.The available follow-up is listed in the Table. One of the patients with a 1.1-cm lung nodule underwent surgical resection. Histological evaluation revealed a 1-cm bronchoalveolar carcinoma (Figure).
Since its introduction into clinical use in the late 1970s, CT scanning has been quickly accepted as an essential diagnostic tool for the detection and staging of many diseases. Recently, CT scanning has been used in asymptomatic people to screen for subclinical disease. For example, cardiac CT scans are becoming more available as a method to detect coronary artery calcification in asymptomatic adults. In many centers, the cardiac CT scan is reviewed only by cardiologists who perform scoring for coronary artery calcification and who are primarily concerned with the cardiac portion of the examination. However, given the fact that cardiac CT scans are actually limited scans through the mid thorax, abnormalities may be present in the extracardiac structures as well. We feel that it should be the responsibility and obligation of the physician interpreting the cardiac CT scan to review the entire study, including the lungs and bones. Therefore, a qualified radiologist should review the entire examination, even if a cardiologist has performed the coronary artery calcification scoring to avoid missing potentially important pathology.
- ↵Agaston AS, Janowitz WR, Hildner FJ, et al. Quantification of coronary artery calcium using ultrafast computed tomography. J Am Coll Cardiol. 1999; 15: 827–832.
- ↵Raggi P, Callister TQ, Cooil B, et al. Identification of patients at increased risk of first unheralded acute myocardial infarction by electron beam computed tomography. Circulation. 2000; 101: 850–855.
- ↵Hunold P, Schmermund A, Seibel RM, et al. Prevalence and clinical significance of accidental findings in electron beam tomographic scans for coronary artery calcification. Eur Heart J. 2001; 22: 1748–1758.
- ↵Henschke CI, McCauley DI, Yankelevitz DF, et al. Early lung cancer action project: summary of the findings on baseline screening. Oncologist. 2001; 6: 147–152.