Jcct 2012 - Shawn - Extracardiac Findings on CT

Journal of Cardiovascular Computed Tomography (2012) 6, 232–245

Review Article

Learning to interpret the extracardiac findings on coronaryCT angiography examinations

Shawn D. Teague, MDa,*, Stacy Rissing, MDa, Jothiharan Mahenthiran, MD, FACCb,Stephan Achenbach, MDc

aDepartment of Radiology, Indiana University, 550 N University Blvd, Rm 0279, Indianapolis, IN 46202, USA;bCommunity Heart and Vascular, Indianapolis, IN, USA and cGiessen University Department of Cardiology,Giessen, Germany

KEYWORDS:Computed tomography;Coronary computedtomography;Coronary CTangiography;Extracardiac;Incidental findings

Conflict of interest: The authors re

* Corresponding author.

E-mail address: [email protected]

Submitted October 23, 2011. Acce

2012.

1934-5925/$ - see front matter � 2012

http://dx.doi.org/10.1016/j.jcct.2012.0

Abstract. Coronary computed tomography angiography (CTA) plays an important role in the identifi-cation of coronary artery disease in low- to intermediate-risk patients. Even with a ‘‘restrictive’’ field ofview, coronary CTA data sets will include visualization of structures adjacent to the heart, including thethoracic great vessels, pericardium, mediastinum, lungs, and bones. CT images enable detailed assess-ment of these structures, at times identifying a potential noncoronary cause of the patient’s presentingsymptom. The reported incidence of extracardiac findings on coronary CTA is as high as 53%–67%.Complete evaluation of the examination requires scrutiny of the soft tissues, lung tissues, and bones,both in the chest and adjacent abdomen. It is important to adjust the CT window display settings atvarious stages of the interpretation process to evaluate all potential extracardiac disease. Althoughin-depth radiology training would be required to correctly identify and interpret all anomalies, this ar-ticle serves as an overview and guide to evaluation of the extracardiac structures included on a coronaryCTA examination. Correct interpretation of extracardiac findings is critical because a false positive in-terpretation can lead to unnecessary testing and treatment that can be as harmful as a false negativeinterpretation. Most importantly, if the cardiac findings do not explain the patient’s symptoms, analternative cause should be specifically sought to appropriately manage the patient.� 2012 Society of Cardiovascular Computed Tomography. All rights reserved.

Introduction

Coronary computed tomography angiography (CTA)plays an important role in the identification of coronaryartery disease in low- to intermediate-risk patients. Even

port no conflicts of interest.

pted for publication February 27,

Society of Cardiovascular Computed

2.007

with a ‘‘restrictive’’ field of view, coronary CTA data setswill include visualization of structures adjacent to the heart,including the thoracic great vessels, pericardium, medias-tinum, lungs, and bones. The high-resolution CT imagesenable detailed assessment of these structures, at timesidentifying a potential noncoronary cause of the patient’spresenting symptom. The reported incidence of extracar-diac findings on coronary CTA is as high as 53%–67%.1–6

Approximately 4%–25% of these noncardiac findings areconsidered potentially significant and may require follow-up or additional investigation. Another 5%–11% of these

Tomography. All rights reserved.

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http://dx.doi.org/10.1016/j.jcct.2012.02.007

http://dx.doi.org/10.1016/j.jcct.2012.02.007

Teague et al Interpreting extracardiac findings on coronary CTA 233

findings are considered critical findings and require imme-diate evaluation or intervention.1–5 Furthermore, the gatedimages of coronary CTA reduce motion artifact and allowassessment of dynamic pathology with a greater accuracy.Current literature suggests that noncalcified pulmonarynodules (1%–24%) are the most common extracardiac find-ing.3–5 Other common findings included liver cysts, calci-fied pulmonary nodules, mediastinal lymphadenopathy,and hiatal hernia.1–8 Some important extracardiac findingssuch as pneumonia, pneumothorax, gallstones, hiatal her-nia, and aortic aneurysm had an effect on subsequent man-agement of these patients.3–5

Scope of need for training

The potential clinical significance of these incidentalfindings necessitates readers of coronary CTA to recognizeand interpret important extracardiac findings. Radiologytraining routinely incorporates cross-sectional imaging andreview of all extracardiac structures systematically on a CTexamination. Currently, many cardiologists are trained toread coronary CTAwith limited emphasis on recognition orinterpretation of extracardiac findings. Because studies areoften ordered for the evaluation of acute chest pain,cardiologists are increasingly expected to identify anddiagnose noncardiac causes of chest pain. At present, thereare various published training requirements that qualifyreaders to independently interpret extracardiac findings ona coronary CTA examination. The American College ofRadiology Practice Guidelines on performing and inter-preting cardiac CT state that a reader must complete 200hours of Category I continuing medical education (CME) inCT and interpret and report 500 CT cases under supervisionand complete R30 hours of Category I CME in cardiacimaging.9 The 2008 revision of the cardiology fellowshiptraining guidelines recommends review of 150 cardiac CTcases for incidental findings and a review of a dedicatedteaching file of 25 cardiac CT cases that feature the pres-ence of significant noncardiac pathology.10 This experienceis designed to serve as an introduction to recognition ofthese extracardiac findings but cannot provide expertise inthe full spectrum of pathology found in the thorax andupper abdomen included in the scan. Current opinions arediverse for the need and the scope of expertise requiredfor evaluation of extracardiac findings.5,8,11 There are sev-eral models of shared versus single trained reader para-digms to accomplish comprehensive assessment of thisissue. Regardless, recognition of extracardiac findings ona coronary CTA remains important and crucial to patientcare. It requires dedicated additional training and interpre-tation skills by the reader(s). This article outlines a system-atic approach to interpretation of common extracardiacfindings. Examples are provided and may serve as a toolto improve identification and interpretation of extracardiacfindings on a coronary CTA examination.

Extra-cardiac reading method

Windowing and leveling

For evaluation of the extracardiac structures, customwindow settings are used to optimize visualization of thedifferent body tissues. The most commonly used windowsettings are soft tissue, lung, and bone windows. Specificvalues for the center and width of these windows are set,based on Hounsfield units. Soft tissue windows (Fig. 1A),used for evaluation of the mediastinum and upper abdomen,have a center of 50 and a width of 350. Lung windows(Fig. 1B), set for evaluation of the pulmonary parenchyma,have a center of 2500 and a width of 1800. Bone windows(Fig. 1C), used for evaluation of the bony structures, havea center of 500 and a width of 2000. Any pixels with aHounsfield unit above the upper limits of the width will bewhite, and pixels with a Hounsfield unit below the lowerlimits of the width will be black. Values within the windowwidth will be visualized as a shade of gray relative to theHounsfield unit. One additional window that can be helpfulin cardiac CT examinations is the vascular window(Fig. 1D), used for evaluating the coronary arteries as wellas other vascular structures. The center and width for evalu-ating vessels depend somewhat on the degree of vascularenhancement; however, suggested settings are a center of100 and awidth of 900. There are additional specialized win-dows for use with the liver and kidneys, but these topics arebeyond the scope of the basics covered in this review.

Planes

Most disease pathology is best evaluated with an axialplane of cross-sectional imaging. This is the primary planein which CT images are acquired and displayed forinterpretation. With the advent of faster computers, imagesare often reconstructed into coronal (Fig. 2A) and sagittal(Fig. 2B) planes as well. These additional planes can high-light specific disease pathology or anatomical findings. Forexample, the sagittal plane is helpful when evaluating thespine for disease. The coronal images often best displaythe anatomy of the tracheobronchial tree. Coronal imagescan also be useful when evaluating pulmonary pathology,such as the anatomic lobe and segment of a lung noduleor area of consolidation.

Field of view

Although the craniocaudal dimensions of a cardiac CTscan are limited, the entire thorax, from chest wall to chestwall, is exposed to radiation. To improve spatial resolutionof the inherently small coronary arteries on a coronary CTangiogram, the final images for coronary evaluation usuallyexclude the chest wall and a portion of the lungs. However,images can be reconstructed to show the entire cross-section

Figure 2 The coronal plane divides anterior from posterior. (A) This image shows the utility of the coronal plane for evaluation of trache-obronchial anatomy. (B) This image shows the anatomic location of a right middle lobe nodule (arrow) on a coronal image. (C) The sagittalplane divides right from left and shows the utility of the sagittal plane for evaluation of the thoracic spine. (D) This image shows the anatomiclocation of the same right middle lobe nodule (arrow) as in panel B, highlighting the appearance of the lung fissures on the sagittal plane.

Figure 1 (A) Soft tissue window image with center of 50 and width of 350 allows for optimal evaluation of the chest and upper abdominalsoft tissues. This axial image shows normal mediastinal and chest wall structures. However, this window should be used to look for lym-phadenopathy, thyroid nodules, and subcutaneous nodules among other soft tissue disease. (B) Lung window image with center of 2500and width of 1800 allows for optimal evaluation of the lung parenchyma. This image shows normal lung parenchyma. However, this win-dow should be used to look for pulmonary nodules and masses, infection, and emphysema among other lung parenchymal diseases.(C) Bone window image with center of 500 and width of 2000 allows for optimal evaluation of the bony thorax. This image shows normalbony structures. However, this window should be used to look for degenerative changes of the spine, rib, or vertebral compression fractures,and suspicious lytic or sclerotic bone lesions among other bone diseases. (D) Vascular window image with center of 100 and width of 900allows for optimal evaluation of the chest vasculature. This image shows the normal appearance of the vessels. However, this widow shouldbe used to look for aortic aneurysm, aortic dissection, and pulmonary embolus among other vascular diseases.

234 Journal of Cardiovascular Computed Tomography, Vol 6, No 4, July/August 2012

Figure 3 (A) Axial image (soft tissue window) shows a densely calcified subcarinal lymph node (arrow), consistent with old granulom-atous infection, probably histoplasmosis. (B) Axial image shows a small, slightly eccentric calcification (arrow) within an enlarged non-calcified subcarinal lymph node. This small amount of calcification is not enough to ensure a benign cause, and, given the large size of thelymph node, further evaluation or follow-up imaging is suggested. (C) Axial image (soft tissue window) shows a 1.3-cm short-axis para-tracheal lymph node. This lymph node contains a low-density fatty hilum (arrow), characteristic of a benign lymph node. (D) Axial imageshows an enlarged subcarinal lymph node (arrow), and (E) axial image in shows an enlarged left hilar lymph node (arrow). These lymphnodes show heterogeneous enhancement and lack calcification. The appearance raises concern for malignant lymphadenopathy, and furtherevaluation is necessary.


of the chest at any scan level. The diameter of the displayedimage (field of view) is usually around 250–280 mm for acardiac CT study. This diameter is large enough to show theentire heart but limited for optimal spatial resolution of thecoronary arteries. A field of view smaller than 250 mm may

Figure 4 (A) Axial image (soft tissue window) shows a large hypodenare irregular, and further evaluation with thyroid ultrasound scanning isneous thyroid gland (arrow), which results in rightward tracheal deviatioclassic for thyroid goiter.

exclude vital structures from visualization and often onlyresults in magnification of the image without improvedspatial resolution. Regardless of the field of view used, it isimportant to evaluate all the additional structures that areincluded within the chosen field of view.

se nodule in the left thyroid lobe (arrow). The borders of the lesionrecommended. (B) This axial image shows an enlarged, heteroge-n and lateral displacement of the great vessels. The appearance is

Figure 5 (A) Axial image (vascular window) shows a dilated main pulmonary artery (arrow) that measures 4.5 cm in diameter. Pulmo-nary artery dilatation should raise the possibility of pulmonary artery hypertension, especially in patients with underlying lung disease. (B)This image shows an enhancing tubular structure that courses to the left of the aortic arch, consistent with a left superior vena cava (SVC).(C) This image is more inferior and shows the left SVC located along the left aspect of the left atrium. The left SVC in this case eventuallydrains into the coronary sinus. (D) The coronal image shows the left SVC along the left upper mediastinum. There is no typical right SVC inthis example. (E–G) These images show partial anomalous pulmonary venous return (PAPVR) with drainage of the left upper lobe pul-monary veins into the left innominate vein via a vertical vein. (E) This image shows an enhancing vascular structure along the left medi-astinum (arrow), similar to the appearance of a left SVC. In the case of left PAPVR, however, the branching left upper lobe pulmonary veinscan be seen draining into the vertical vein. (F) This image shows the vertical vein (arrow) draining into the left innominate vein. (G) Cor-onal image shows the left upper lobe pulmonary veins draining into the vertical vein (arrow), with flow directed toward the left innominatevein. (H and I) These images show anomalous drainage of the right upper lobe pulmonary veins into the SVC. (H) The arrow indicates theanomalous right upper lobe pulmonary vein. (I) The arrow indicates the SVC. This patient also had a sinus venous atrial septal defect ac-counting for the large right atrium.


Figure 5 (Continued). (J) Axial image shows a dilated ascending thoracic aorta, measuring up to 4.9 x 5.0 cm in diameter. For the as-cending aorta, diameter . 4.0 cm is considered dilated or ectatic, and diameter . 4.5 cm is considered aneurysmal. The presence of anascending thoracic aortic aneurysm should be noted in this case, and follow-up imaging should be obtained to evaluate for interval increasein aortic dimensions. Axial images show the intimal flap of an aortic dissection (arrow) at the level of the arch (K) and lower descendingthoracic aorta (L). The intimal flap separates the true lumen (white arrow) from the false lumen (black arrow). A small amount of intra-mural hematoma is seen at the level of the lower descending thoracic aorta. (M) Axial image shows atherosclerosis (arrow) of the aorta witha large noncalcified plaque along the left lateral aspect. There is likely a component of thrombus associated with the plaque, given thesignificant asymmetry. Less severe disease can also be noted in the ascending aorta, including a small amount of calcified plaque (blackarrow). (N) Axial image shows a penetrating ulcer (arrow) extending into the wall of the descending aorta. (O) Axial image at the level ofthe aortic arch shows extensive soft tissue thickening (arrows) surrounding the opacified aortic lumen. This is the typical appearance ofaortitis which is Takayasu aoritis in this patient.


Approach to reading the extracardiacportion of the examination

Soft tissue windows (CT settings: center 50and width 350)

Lymph nodesGiven the limited field of view of cardiac CT, the

primary lymph nodes to evaluate are located in the medi-astinum and hilum. Two important features to considerwhen a lymph node is identified are density and size.

The size of a lymph node is important. For CT studies,the lymph node short-axis size that raises concern isR1 cm.Once the lymph node reaches 1 cm in short-axis dimen-sion, it is considered enlarged and may be pathologic(Fig. 3).4 The lymph node could be reactive to an infec-tious/inflammatory process or, more importantly, second-ary to neoplasm. If the enlarged lymph node is likelyreactive with secondary signs of infection such as

pneumonia, then the likely benign nature of the lymphnode can be suggested. If the lymph node is enlarged with-out secondary findings to suggest the underlying cause,then neoplasm must be considered and follow-up and/orbiopsy should be pursued.

Lymph nodes with high density often contain calcifica-tion and reflect a benign process. For example, if there iscentral or diffuse calcification, the lymph node is likelysecondary to a benign process such as prior tuberculosis,sarcoidosis, silicosis, or histoplasmosis (Fig. 3A). Althougha peripheral egg-shell pattern of calcification is most likelysecondary to silicosis, this pattern can sometimes be seenwith longstanding sarcoidosis. Not all calcified lymph no-des are benign; thus, the pattern of calcification is impor-tant. Specifically, if the calcification within a lymph nodeis small and eccentric in location, then the lymph node can-not be dismissed as benign (Fig. 3B). The size and otherfeatures of the lymph node must be evaluated to determinewhether there is concern for neoplasm. Consultation with aradiologist is recommended. Lymph nodes with low density


often contain fat. If there is a large fatty hilum in the lymphnode, findings are consistent with a benign lymph node,even if it is enlarged by size criteria (Fig. 3C).

ThyroidThe thyroid gland is not routinely included within the

field of view during cardiac CT imaging. In the case ofcoronary artery bypass graft and evaluation for graftpatency, however, more superior images are obtained, andthe thyroid may be visualized. Heterogeneous enhancementof the thyroid may indicate the presence of a thyroid nodule(Fig. 4A). Concern for thyroid nodule can be mentioned,and dedicated thyroid ultrasound scanning can be recom-mended for further evaluation. A thyroid gland that is dif-fusely enlarged and heterogeneous may indicate thyroidgoiter. A large thyroid goiter can extend into the mediasti-num, displacing the trachea and great vessels (Fig. 4B).Thyroid goiter is most common in elderly women. Charac-teristic findings of thyroid goiter usually do not require ad-ditional imaging evaluation.

Great vesselsThe pulmonary artery is often included within the field

of view in a coronary CT study. The most important featureto evaluate for the pulmonary artery is the size. Thediameter of the main pulmonary artery should not be .3cm. If the diameter is .3 cm, this finding should bementioned (Fig. 5A). Dilatation of the main pulmonary ar-tery can be an indicator of pulmonary artery hypertension,especially in patients with concurrent lung disease, such asemphysema. Right ventricular dilatation is a secondary signof pulmonary hypertension, and the combination of pulmo-nary artery and right ventricular dilatation should highlysuggest the diagnosis. The remainder of the great vesselswill not routinely be included in coronary CT but may beincluded as part of other cardiac CT studies.

A few vascular anomalies are important to recognize,especially for cardiovascular disease. These anomaliesinclude a persistent left superior vena cava (SVC) andpartial anomalous pulmonary venous return (PAPVR). Apersistent left SVC typically empties into the coronarysinus (Fig. 5B-D) but can also drain into other locations,such as a cardiac chamber. A left SVC can be seen in com-bination with a right SVC or can be present as the onlySVC. Left upper lobe PAPVR is important to distinguishfrom a left SVC (Fig. 5E-G). In left-sided PAPVR, theleft upper lobe pulmonary vein drains into the left innomi-nate vein. PAPVR can also be seen on the right, usuallywith a right upper lobe pulmonary vein draining into a rightSVC (Fig. 5H-I).

The diameter of the aorta should be measured toexclude the presence of aortic aneurysm (Fig. 5J). Theaortic size is best measured in true cross-section, andthe normal ascending aorta should not exceed 4 cm in di-ameter. The aorta should taper in caliber from the sinotub-ular junction to the diaphragm. If there is any area where

the aortic diameter increases and then decreases again,this indicates ectasia or aneurysm, depending on the mea-sured diameter. Examination of the aorta for dissection orintramural hematoma is also important, especially whenthe study is obtained in the setting of acute chest pain(Fig. 5K-L). If there is clinical concern for dissection orintramural hematoma, a noncontrast study should be per-formed first to evaluate for hyperdense acute blood withinthe wall of the aorta and/or the presence of a thrombosedlumen.

Another common aortic disease is atherosclerosis(Fig. 5M), usually seen as a combination of calcified andnoncalcified (low-density) plaque along the periphery ofthe aorta. In areas with a large amount of plaque, a throm-bus can form and potentially embolize peripherally. Pene-trating ulcers can also develop in the setting ofatherosclerotic disease (Fig. 5N). This process occurswhen an atherosclerotic plaque ulcerates, disrupts the in-tima, and extends into the media of the aortic wall. Pene-trating ulcer, especially at the level of the mid descendingthoracic aorta, can result in intramural hematoma or evenaortic dissection.

Aortitis is less common than atherosclerotic disease, butit should be considered when findings of diffuse wallthickening, stenosis, occlusion, or even dilatation of theaorta are present. Takayasu arteritis is the most commonaortitis and typically show wall thickening at the aortic archalong with stenosis at the descending thoracic or abdominalaorta (Fig. 5O).

Solid organs of the upper abdomenUsually only a limited portion of the upper abdomen is

visualized on a cardiac CT. Portions of the liver, spleen,adrenal glands, and bowel are often included within thefield of view. The superior aspect of the kidneys andpancreas may also be visualized. Most important duringevaluation of the upper abdomen is exclusion of a solid-organ mass lesion (Fig. 6A).

Liver and renal cysts are common benign lesions en-countered when evaluating the upper abdomen (Fig. 6B-C).Cysts appear as smooth, round, low-density lesions. TheHounsfield unit of a cyst should be near zero, indicatingthe presence of water-like fluid. The hemangioma is anothercommon benign lesion found in the liver. Hepatic hemangi-oma is a highly vascular lesion showing a characteristic earlyperipheral nodular pattern of enhancement, often termedperipheral puddling (Fig. 6D). Adrenal disease is also rela-tively common, especially the adrenal adenoma. This diag-nosis can be made when an adrenal nodule is of lowattenuation, measuring ,10 HU (Fig. 6E). Such a lowHounsfield value is usually only seen on a noncontrast study,and the adrenal adenoma can show variable enhancement(40–50 HU) on a contrast-enhanced examination. It is im-portant to realize that the evaluation of the solid abdominalorgans can be limited because of the early phase of contrastpresent during the cardiac scan.

Figure 6 (A) Axial image of the upper abdomen included as part of a coronary CT angiogram. A 1-cm hypervascular lesion is seen in theright hepatic lobe (arrow). The differential diagnosis would include small hemangioma, arterioportal shunting, and other diseases. In a pa-tient with cirrhosis, findings would raise concern for hepatocellular carcinoma. (B) Axial images show low-density lesions (arrows) in theliver which are round with smooth margins. The large 2 lesions measure close to 0 HU units, confirming they are benign cysts. (C) A similarlesion (arrow) is noted in the kidney, also consistent with a benign cyst. (D) Axial image shows a large centrally low-density lesion (arrow)with areas at the periphery (black arrow) which are bright, consistent with peripheral puddling, which is an enhancement pattern diagnosticof hemangiomas. (E) Axial image shows a low-density lesion in the left adrenal gland which is round with smooth borders. The lesionmeasures 4 HU, consistent with a benign adrenal adenoma. The abundant fat within the adenoma accounts for the low Hounsfield mea-surement. (F) Axial image shows an enlarged common bile duct (arrow) as it passes through the head of the pancreas. The patient hashad prior cholecystectomy as indicated by the surgical clips (black arrow). The common bile duct can measure up to 1.0 cm after chole-cystectomy, consistent with postoperative change. (G) Additional image shows intrahepatic biliary dilatation in a patient with metastaticdisease. Note is made of a metastatic lesion in the left lobe of the liver (arrow) and surrounding ascites (black arrow). (H) Axial imageshows bilateral hydronephrosis (black arrows), more marked on the right than on the left. The patient had retroperitoneal lymphadenopathy,resulting in ureteral obstruction and thus hydronephrosis.


Other common abdominal disorders include biliaryductal dilatation (Fig. 6F-G) and hydronephrosis. Althoughbiliary ductal dilatation can be a normal finding in patientsafter cholecystectomy, this finding can also herald the pres-ence of an obstructing distal biliary tract stone or pancreatichead mass. Hydronephrosis presents as dilatation of the py-localyceal system (Fig. 6H). This finding is most com-monly because of an obstructing renal or ureteral calculus

but on rare occasions can be caused by an abdominal or pel-vic mass that compresses the distal ureter.

Stomach and bowelHiatal hernia is themost common findingwhen evaluating

the stomach and bowel (Fig. 7A). A hiatal hernia is presentwhen there is stomach, identified by the characteristic rugalfold pattern, located above the level of the gastroesophageal

Figure 7 (A) A portion of the stomach is located above the diaphragm, posterior to the heart and anterior to the spine and descendingthoracic aorta. The stomach can be definitively identified by its characteristic rugal fold pattern and air content. These findings are consis-tent with a moderate-sized hiatal hernia. (B) Single axial noncontrast CT image shows multiple air-filled outpouchings (arrow) along themargin of the transverse colon, consistent with colonic diverticulosis.


junction. Colonic diverticulosis is also a common finding(Fig. 7B). Colonic diverticuli are small air-filled outpouch-ings along the wall of the colon. Most other disease of thestomach and bowel is beyond the scope of this review.

Peritoneal cavityWhen evaluating the peritoneal cavity, the 2 most

important findings are pneumoperitoneum (free air) andascites. Sometimes it can be helpful to use lung windowsettings to view the peritoneal cavity and evaluate for freeair. Unless massive in quantity, free air will usually presentas small bubbles that are non-dependent in location, such asanterior to the diaphragm and along the inferior surface ofthe liver (Fig. 8A-B). Ascites is usually visualized as anamorphous collection of hypodense fluid that collects inthe dependent portions of the peritoneal cavity, oftenaround the liver, gall bladder, and/or spleen (Fig. 8C). Un-complicated ascites should measure ,20 HU. Ascitic fluidwith attenuation .20 HU should raise concern for blood orbowel contents within the fluid.

Figure 8 (A) Axial image (lung window) shows a crescent-shaped colung parenchyma by the diaphragm. (B) The sagittal image nicely showthe liver and below the diaphragm. (C) Axial image (soft tissue windowlocated along the borders of the liver and spleen. The liver is small anunexpected in this patient with hepatic cirrhosis.

Subcutaneous tissueSubcutaneous tissues included in the field of view may

show subcutaneous nodules, sebaceous cysts, and othermore concerning lesions, such as melanoma (Fig. 9). Injec-tion granulomas may also be visualized as soft tissue nod-ular densities with associated calcification present in thesubcutaneous tissues. These injection granulomas form atsites of repeated subcutaneous injections.

Lung windows (CT settings: center 2500and width 1800)

Lung parenchymaIn the evaluation of the lung parenchyma, disease can be

separated into 2 main categories: diseases that make thelung more lucent (black) and diseases that make the lungmore dense (white). Processes that make the lung morelucent result from parenchymal destruction, such as em-physema, cystic lung disease, or air trapping.

llection of free air anterior to the liver (arrow), separated from thes the anatomic location of pneumoperitoneum (arrow), anterior to) shows ascites (arrow) throughout the upper abdomen, primarilyd shows a micronodular contour, and the finding of ascites is not

Figure 9 Axial image shows two soft tissue density nodules (ar-rows) located within the posterior chest wall subcutaneous tissues.In this patient with a history of melanoma, these soft tissue nod-ules are highly concerning for subcutaneous metastases. A leftpara-aortic lymph node and left lower lobe nodule are also noted,consistent with metastatic disease.


Emphysema is usually related to smoking and is com-monly present in the same patient population that isundergoing evaluation for coronary artery disease. Emphy-sema is the result of parenchymal destruction and presentsas small or large holes within the lung (Fig. 10A). Theseholes within the lung parenchyma do not have discerniblewalls, a key finding in the distinction between emphysemaand cystic lung disease. When areas of lung destruction arelarge, bullae may form. These bullae may be located at thelung apices, which are not often included within the field ofview on a cardiac study. Holes in the lung parenchyma thatshow definable walls are usually secondary to cystic lungdisease (Fig. 10B), such as Langerhans cell histiocytosis(eosinophilic granuloma) or lymphangioleiomyomatosis.If cystic lung disease is suspected, consider consultationwith a radiology expert.

Many diseases result in increased opacity within thelung parenchyma. Ground-glass opacities are common andare characterized by hazy increased attenuation of the lungwith preserved visualization of the bronchial and vascularmargins (Fig. 10C). These ground-glass opacities are oftennonspecific in appearance, and a definitive diagnosisusually cannot be made. Infectious and inflammatory pro-cesses are the most common cause for ground-glass atten-uation; however, adenocarcinoma in situ (commonlyreferred to as bronchioloalveolar cell carcinoma) canhave an identical imaging appearance. Therefore, it is im-portant to recommend follow-up imaging for ground-glassopacities to evaluate for resolution or stability. A focalground-glass nodular opacity that is increasing in sizeand/or density over time should raise concern for

malignancy, and further investigation with biopsy maybe appropriate.

Consolidation is characterized by a more confluent areaof increased density within the lung parenchyma (Fig. 10D).Although pneumonia is the most common cause, the accu-mulation of pus, blood, water, or cells (tumor) within theair spaces of the lung can result in consolidation. If clinicalsymptoms of pneumonia are absent (ie, fever or leukocyto-sis), other processes such malignancy must be considered.

Solid lung nodules are one of the most commonincidental findings in cardiac CT (Fig. 10E-F). This state-ment is especially true in geographic areas where endemicfungal infections are common, such as the Ohio River Val-ley and dessert regions of the Southwest. Lung nodulesmust be followed by imaging to evaluate for interval growthor other signs of malignancy. The Fleischner Society haspublished guidelines for follow-up imaging of incidentalpulmonary nodules.12

Similar to lymph nodes, the presence of calcificationwith a lung nodule is often an indicator of a benign process.The thin-section images obtained for cardiac imaging areuseful when looking for nodule calcification; however, aswith lymph nodes, the pattern of calcification is critical.Nodules with central or diffuse calcification are consideredbenign (Fig. 10G-H). The presence of eccentric calcifica-tion is more worrisome and does not confirm a benigncause (Fig. 10I-J); follow-up imaging or further evaluationis necessary. Unfortunately, without follow-up imaging, it isimpossible to determine whether a small noncalcified nod-ule is benign or an early lung cancer.

A lung mass is distinguished from a lung nodule by a sizeR 3 cm. The presence of a lung mass is obviously a muchmore worrisome finding, and primary lung cancer or met-astatic disease must be considered (Fig. 10K). Short-termfollow-up imaging for a lung mass or nodule . 1 cm in di-ameter is usually not appropriate. Sometimes positron emis-sion tomography/CT may be valuable; however, oftentimesbiopsy is necessary for definitive diagnosis.

Pleural effusionThe pathology of the pleural space can range from

simple transudative effusion of pulmonary edema to com-plex empyema. Simple pleural effusion should measure,20 HU, layer dependently within the chest, and show ameniscus configuration (Fig. 11A). Loculated pleural effu-sion can occur when pockets of fluid form, often in nonde-pendent locations within the pleural space. Pleural fluid ofhigh density (.20 HU) may represent hemothorax orempyema. Other characteristics of empyema include locu-lation, pleural thickening, and the presence of small bubblesof air within the pleural fluid collection (Fig. 11B-C). Intra-venous contrast can help distinguish among pleural fluid,pleural thickening, and atelectatic lung. After contrast ad-ministration, pleural fluid will often remain low density,thickened pleura will show mild enhancement, and atelec-tatic lung will brightly enhance.

Figure 10 (A) Axial image (lung window) shows replacement of the normal lung parenchyma by multiple holes without discernible bor-ders. The appearance is characteristic of emphysema. (B) Axial image also shows multiple holes within the lung parenchyma. In contrast tothe case of emphysema in panel A, the cysts in this example show thin but definable walls, consistent with cystic lung disease. In this34-year-old woman with progressive dyspnea, the diagnosis is lymphangioleiomyomatosis. (C) Coned down axial image (lung window)shows a small ground-glass opacity (arrow) in the left lower lobe. Although this opacity could be secondary to a focal infectious or inflam-matory process, in this case the diagnosis was bronchioloalveolar cell carcinoma. The presence of a focal ground-glass opacity shouldprompt short-term imaging follow-up or further diagnostic workup. (D) Axial image (lung window) shows a focal area of consolidationin the left lower lobe. In this 28-year-old man with fever and cough, findings are consistent with pneumonia. In an older patient with con-solidation, follow-up imaging after treatment to ensure complete resolution is recommended to exclude neoplasm. (E) This image (lungwindow) shows a small nodule (arrow) in the lingula. (F) This image (soft tissue window) shows the same nodule (arrow) and confirmsthe absence of any calcification. This subcentimeter incidental nodule is indeterminate in cause, and follow-up recommendations are basedon the Fleischner Society guidelines. (G) This image (lung window) shows a small nodule (arrow) in the left upper lobe. The center of thenodule appears denser. (H) This image (soft tissue window) confirms the presence of a high-density calcification in the center of the nodule(arrow). This appearance is classic for a benign calcified granuloma, and no follow-up imaging is necessary. Axial (I) and sagittal (J)images (lung window) show a nodule (arrow) in the right upper lobe. This nodule contains a small focus of calcification, located in aneccentric position along the inferior margin of the nodule. In contrast to the large central calcification shown in panels I and J, the smalleccentric focus of calcification in this example is not enough to confirm a benign cause. This partially calcified nodule remains indetermi-nate, and short-term imaging follow-up or further evaluation is recommended. (K) Cardiac CT was performed for evaluation of the pul-monary vein anatomy before pulmonary vein ablation. Axial image (lung window) shows a 5-cm mass in the right upper lobe. Thismass shows spiculated borders and some adjacent ground-glass opacification. The appearance is a concern for primary lung cancer, andpathologic studies from percutaneous biopsy confirmed adenocarcinoma.


Figure 11 (A) Axial image (lung window) shows bilateral pleu-ral effusions. The effusions are layering dependently within theposterior pleural spaces. This image also shows mild interlobularseptal thickening and subtle bilateral ground-glass opacities. Theconstellation of findings in this case is most consistent with pul-monary edema. (B) Axial image (soft tissue window) shows aright pleural collection. There is thickening and enhancement of

Figure 12 Axial image (lung window) shows a small left pneu-mothorax. Air appears as pure black within the pleural space.There is a thin pleural line (arrow) separating the air within thepleural space from the lung parenchyma.


PneumothoraxPneumothorax is a relatively easy diagnosis to make and

should be looked for on every examination. Pneumothoraxis characterized by the presence of low-density air withinthe pleural space. Often there is a sharp pleural line,indicating the boundary between the lung parenchyma andthe adjacent pleural air (Fig. 12).

Bone windows (CT settings: center 500and width 2000)

Lytic or sclerotic lesionsWhen evaluating the bones, it is important to look for

focal lesions of abnormal increased (sclerotic) or decreased(lytic) density. Metastatic lesions can be either sclerotic orlytic, depending on the cause of the primary malignancy.These focal lesions must be distinguished from the processof degenerative disc disease, which is commonly seen inthe spine. Degenerative changes are often more diffuse,characterized by osteophyte formation and intervertebraldisk space narrowing (Fig. 13A-B). Although bony meta-static disease can be diffuse and widespread, most lesionsare more focal in nature and tend to preserve the diskspaces (Fig. 13C).

FracturesRib fractures (Fig. 14) and vertebral compression frac-

tures can be incidental findings discovered on a cardiacCT. Most of these fractures will be chronic rather thanacute findings. Chronic rib fractures are characterized by

both the visceral and parietal pleura layers (arrows). This findingis known as the split pleura sign and is suggestive of empyema.(C) Axial image (lung window) also shows a right pleural collec-tion. This collection contains multiple small pockets of air, raisingthe concern for empyema. Sometimes recent instrumentation, suchas recent thoracentesis, can produce a similar appearance.

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Figure 13 (A) Sagittal image (bone window) shows endplatesclerosis and osteophyte formation (arrow), consistent with degen-erative disk disease. This appearance should be distinguished from

Figure 14 (A) Axial image (bone window) shows angulationand cortical disruption of a left-sided rib (arrow). Findings areconsistent with rib fracture. In this case, there is little callus for-mation, and the fracture age may be acute to subacute. (B) Thisimage shows sclerotic change at the site of the right rib fracture(arrow). This is an old rib fracture that has had incompletehealing.


irregular contour and sclerotic change with or without visu-alization of the actual fracture line. Callus formation is of-ten seen during the subacute phase. An acute rib fracturemay show a sharp fracture margin and frank angulation.Vertebral compression fractures are best visualized on thesagittal images as vertebral body height loss.

the patchy sclerotic vertebral changes seen with blastic metastaticdisease (see panel C). (B) Axial image (bone window) shows theappearance of bulky osteophytes (arrow) in this plane. (C) Sagittalimage (bone window) shows patchy sclerosis throughout thebones, including the vertebral bodies, sternum, and manubrium.This appearance is characteristic of blastic metastatic disease,such as in prostate cancer.

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Conclusion

In summary, a multitude of noncardiac findings can bepresent on CTA examinations obtained for coronary arteryevaluation. In fact, the high spatial resolution of coronaryCT angiography imaging may show more abnormalities andvariants than a standard chest CT. Complete evaluation ofthe examination requires scrutiny of the soft tissues, lungtissues, and bones, both in the chest and adjacent abdomen.It is important to adjust the CT window display settings atvarious stages of the interpretation process to evaluate allpotential extracardiac disease. Although in-depth radiologytraining would be required to correctly identify andinterpret all anomalies, this article serves as an overviewand guide to evaluate the extracardiac structures includedon a coronary CTA examination. Correct interpretation ofextracardiac findings is critical because a false positiveinterpretation can lead to unnecessary testing and treatmentthat can be as harmful as a false negative interpretation.Most importantly, if the cardiac findings do not explain thepatient’s symptoms, an alternative cause should be specif-ically sought to appropriately manage the patient.

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