A comprehensive electrocardiogram-gated 64-slice multidetector computed tomography imaging protocol to visualize the coronary arteries, thoracic aorta, and pulmonary vasculature in a single breath hold.

OBJECTIVES: Advances in computed tomography technology may permit the evaluation of coronary disease, aortic dissection, and pulmonary embolism with a single contrast bolus and breath hold. We sought to determine whether 64-slice computed tomography angiography (CTA) allows for simultaneous visualization of the coronary arteries, thoracic aorta, and pulmonary arteries (coronary, aorta, pulmonary [CAP]) with image quality comparable to routine CTA protocols. MATERIALS AND METHODS: We prospectively enrolled 20 patients who underwent CAP CTA. Image quality of CAP CTA was assessed qualitatively and quantitatively and compared with dedicated coronary (n = 20) and pulmonary (n = 10) CTA data sets using matched controls. RESULTS: The mean amount of contrast and radiation dose was 132 +/- 10 mL and 17.8 +/- 1.8 mSv, 78 +/- 9 mL and 13.7 +/- 3.4 mSv, and 135 mL and 11.9 +/- 1.5 mSv for CAP CTA, coronary CTA, and pulmonary CTA, respectively (P = 0.001). There was no difference in overall image quality (P = 0.88), presence of motion artifacts (P = 0.40), or enhancement of the proximal coronary arteries (median [interquartile range for contrast-noise ratio was 12.5 9.9-15.2 vs 13.1 10.3-16.9; P = 0.17]) or thoracic aorta (264 [113-326] vs 245 [107-295]; P = 0.34) between CAP CTA and the dedicated coronary CTA, respectively. However, contrast attenuation was higher in the pulmonary arteries with CAP CTA (363 [253-424]) versus the standard pulmonary CTA protocol (235 [182-269]; P = 0.0001). CONCLUSIONS: : Using an individually tailored single contrast injection, CAP CTA permits simultaneous visualization of the coronary arteries, thoracic aorta, and pulmonary arteries with excellent image quality. Further research is necessary to determine whether this protocol may enhance triage of patients with undifferentiated acute chest pain.

The prevalence of symptomatic and coincidental pulmonary embolism on computed tomography.

PURPOSE: To investigate the proportion of pulmonary embolism (PE) on computed tomographic pulmonary angiography (CTPA) and the proportion of coincidental PE on regular contrast-enhanced CT in oncological and nononcological patients. METHODS: This study received internal review board approval and was Health Insurance Portability and Accountability Act compliant. All consecutive adult patients who had contrast-enhanced chest CT or dedicated CTPA during January 2005 were studied. Procedural codes were used to identify cases, and all CT images were reviewed. Clinical data collected included oncology status, chemotherapy regimen, site of tumor, and location of PE. chi2 Tests were used for statistical analysis. RESULTS: Two hundred twenty-nine patients had CTPA, and 27 (11.8%) of them were positive for PE. Of 1168 patients who had contrast-enhanced CT for other indications, coincidental PE was found in 21 patients (1.8%). The proportions of coincidental PE were 3.3% of patients with progressive cancer, 2.5% of patients with stable cancer, 0.7% of patients with no evidence of cancer posttreatment, and 1.0% of nononcological patients. Coincidental PE was found more frequently in patients with progressive cancer compared with nononcological patients (P = 0.035). Patients who were on chemotherapy also had a higher risk of coincidental PE (P=0.019). CONCLUSIONS: The prevalence of symptomatic PE on dedicated CTPA was 11.8%, and the rate of coincidental PE on contrast-enhanced CT was 1.8%. Coincidental PE was significantly higher inpatients with progressive cancer or those receiving chemotherapy.

Discordance between CT and angiography in the PIOPED II study.

PURPOSE: To retrospectively evaluate the causes of discordant computed tomographic (CT)-angiographic readings from the Prospective Investigation of Pulmonary Embolism Diagnosis, or PIOPED, II study. MATERIALS AND METHODS: Institutional review board approval was obtained for this HIPAA-compliant study. Of 1036 patients suspected of having pulmonary embolism who were examined with CT, 226 underwent angiography; 206 patients had concordant results and 20 had discordant results according to two independent readers. Of these 20 patients, 10 were men and 10 were women (mean age, 49 years). Among the 20 studies with discordant results, central readers identified seven cases as negative and 13 as positive for pulmonary embolism at CT; these findings were reversed at angiography. Side-by-side comparisons of discordant studies were performed in consensus. The time between CT and angiography and all locations of pulmonary embolism vascular territory were recorded. The McNemar binomial test was used. RESULTS: One patient had false-positive findings at angiography, 13 patients had false-negative findings at angiography, and two patients had false-negative findings at CT. Four patients had true-negative findings at CT; however, findings were positive for thrombus at angiography. The sensitivity for the detection of pulmonary embolism was 87% for CT and 32% for angiography (P=.007). The largest missed thrombus at angiography was subsegmental in eight patients, segmental in two patients, and lobar in three patients; at CT it was subsegmental in two patients. The mean time between CT and angiography was 40 hours+/-21 (standard deviation) (range, 10-97 hours). CONCLUSION: In the interval between CT and angiography, thrombi can remain the same, resolve, develop, or result from angiography.

18F-FDG PET of pulmonary embolism.

OBJECTIVE: The purpose of this study was to describe the manifestations of pulmonary embolism on 18F-FDG PET scans in 13 patients. CONCLUSION: The activity of acute pulmonary embolism on FDG PET scans was significantly higher than the activity of vessels not containing thrombi. The shape of the abnormal FDG uptake may be focal or curvilinear.

Transient interruption of contrast on CT pulmonary angiography: proof of mechanism.

PURPOSE: To test the hypothesis that a transient interruption of contrast is the result of an increase in flow of unopacified blood from the inferior vena cava (IVC) by comparing the relative IVC contribution to the right side of the heart in cases and age-matched and sex-matched controls. MATERIALS AND METHODS: This retrospective study was approved by our internal review board. Of 234 consecutive patients who had both CT pulmonary angiography and a close follow-up diagnostic pulmonary angiogram, or in one case CT pulmonary angiography, 7 cases were identified which contained a transient interruption of contrast. The study group included 2 men and 5 women. The age range was 37 to 77 years (mean 61.3 y +/-13.3). The artifact consists of a segment of the pulmonary arteries which demonstrates poor blood enhancement between areas of increased attenuation both proximally and distally. Hounsfield units (HU) measurements were made in the areas of decreased attenuation, the areas of higher attenuation both proximally and distally, the superior vena cava, IVC, right atrium (RA), and right ventricle (RV). The relative IVC contribution was calculated by equating density in the RA and RV to a weighted average of the densities of the superior vena cava and IVC. Age-matched and sex-matched controls and a 2-tailed paired t test were used. RESULTS: In the patients with the artifact, the average relative IVC contributions to the RA and RV are 80.1% and 79.5%, respectively. In the control patients, the values for the RA and RV are 52.8% (P=0.02) and 55.5% (P=0.02), respectively. CONCLUSIONS: Transient interruption of contrast of the pulmonary arteries represents a flow-related phenomenon associated with an increased IVC contribution to the right side of the heart.

How I do it: CT pulmonary angiography.

OBJECTIVE: The purpose of this article is to describe the techniques to improve motion artifacts, vascular enhancement, flow artifacts, body habitus image noise, vascular opacification in parenchymal lung disease, streak artifacts, and the indeterminate CT pulmonary angiogram. In addition, this article will illustrate the diagnostic criteria of acute and chronic pulmonary emboli. CONCLUSION: Pulmonary embolism is the third most common acute cardiovascular disease, after myocardial infarction and stroke, and it leads to thousands of deaths each year because it often goes undetected. For the more than 25 years that the direct signs of pulmonary embolism have been available to the radiologist on CT, this noninvasive technique has produced a paradigm shift that has raised the standard of care for patients with this disease.

Acute and chronic pulmonary emboli: angiography-CT correlation.

OBJECTIVE: The objective of our study was to review the classic direct and indirect angiographic signs of acute and chronic pulmonary embolism (PE) and correlate these findings with MDCT. CONCLUSION: CT and angiography have complementary roles in the accurate diagnosis of acute and chronic thromboembolic disease. Conventional angiography should be used as a problem-solving technique after CT angiography has been performed because CT angiography is less invasive.

The indeterminate CT pulmonary angiogram: imaging characteristics and patient clinical outcome.

PURPOSE: To retrospectively review imaging characteristics of indeterminate computed tomographic (CT) pulmonary angiograms for pulmonary embolism (PE) and patient outcome. MATERIALS AND METHODS: Investigational review board approval was obtained, informed consent was waived, and the study was HIPAA compliant. Retrospective review of 3612 CT pulmonary angiography reports created between July 1, 2001, and July 1, 2003, was performed with a keyword search for "indeterminate," "nondiagnostic," or "inadequate" (thereafter, all defined as "indeterminate") and yielded studies from 237 patients (mean age, 57 years; 117 men, 120 women). Randomly selected diagnostic studies were used to form a control group of 25 subjects (mean age, 64 years; eight men, 17 women). Electronic medical records were reviewed for follow-up imaging (repeat CT pulmonary angiography, conventional pulmonary angiography, ventilation-perfusion scintigraphy, or lower-extremity ultrasonography [US]), use of anticoagulation, placement of inferior vena cava (IVC) filters, clinical outcomes, and comments regarding indeterminate reading of CT angiograms. Studies (in patients and control subjects) were reviewed for PE, contrast attenuation in the main pulmonary artery (MPA), motion artifacts, image noise, and flow artifacts. Findings were compared with two-sample t tests assuming unequal variance. RESULTS: The cause cited for indeterminism was most often motion (74%), followed by poor contrast enhancement (40%). Contrast attenuation in the MPA was 245 HU +/- 80 (standard deviation) in patients and 339 HU +/- 88 in control subjects (P < .001). Only 46% of indeterminate studies met institutional criteria for adequate contrast attenuation in the MPA. Rereview of studies demonstrated five missed PEs. A total of 81 patients (33%) underwent follow-up imaging within 5 days, with one positive pulmonary angiogram and four positive lower-limb US scans. Reread or follow-up images depicted thromboembolic disease in 4.2% of patients. Nineteen patients (8%) with indeterminate final result were treated for thromboembolic disease with either anticoagulation or IVC filters. Reports on 22% of indeterminate studies contained recommendations for follow-up imaging, and those recommendations nonsignificantly increased the rate for those examinations from 13% to 19%. Review of discharge summaries showed 22% of studies are clinically interpreted as negative. CONCLUSION: The two major causes of indeterminism are motion artifacts and poor contrast enhancement.

Postpneumonectomy pulmonary artery stump thrombosis: CT features and imaging follow-up.

PURPOSE: To retrospectively evaluate the computed tomographic (CT) features of pulmonary artery stump thrombosis at initial and follow-up CT. MATERIALS AND METHODS: The study was approved by institutional review board, which waived informed consent, and was HIPPA compliant. All patients who had undergone pneumonectomy and CT from January 2001 to August 2003, as identified with data search system, were included. Eighty-nine patients (49 men, 40 women; mean age, 60 years) were studied. Thrombus identification, categorization (concave or convex), and stump and thrombus measurements were made by two radiologists in consensus. The use of anticoagulation therapy was determined from patients' charts. The t test was used. RESULTS: Initial CT scans were obtained 34 months +/- 67 (standard deviation) after pneumonectomy; multiple CT scans were obtained in 58 patients during follow-up of 25.1 months +/- 24.8. Eleven (12.4%) of 89 patients had stump thrombi with near equal frequency on either side. Five concave and six convex thrombi were initially identified. Anticoagulation was not commenced for stump thrombosis. The mean length of the right stump (31 mm +/- 10) was greater than that of the left stump (13 mm +/- 7) (P < .01). After a right and left pneumonectomy, there was a significant difference between the length of the stump in patients with (right, 40 mm +/- 14; left, 21 mm +/- 11) and patients without thrombosis (right, 30 mm +/- 9; left, 12 mm +/- 6) (P = .027 and P < .01, respectively). Follow-up CT scans were not available in four cases. CT findings demonstrated a reduction in thrombus size in four patients (one received anticoagulation therapy for concomitant pulmonary embolism). Two patients had stable concave thrombi, one with an initial concave thrombus developed convex thrombus, and one with an initial convex thrombus developed concave thrombus. No thrombi propagated outside of the stump. CONCLUSION: There is a relationship between stump length and the development of in situ thrombosis. The data suggest a rather benign natural history.

Attenuation of acute and chronic pulmonary emboli.

PURPOSE: To compare retrospectively the attenuation coefficients of acute and chronic pulmonary embolism (PE). MATERIALS AND METHODS: Institutional review board approval was obtained, and informed consent was waived. The study was compliant with requirements of the Health Insurance Portability and Accountability Act. All patients with chronic PE, from July 2001 to January 2004, were identified via a radiology report search system; of the 39 identified, 25 were excluded because the thrombi were too small to measure or were obscured by streak artifacts or because there was no corroborative evidence of chronic PE. Of 27 consecutive patients with acute PE who were also identified, two were excluded because of streak artifacts. The final study group included six women and eight men with chronic PE (mean age, 50 years; range, 26-76 years) and 11 women and 14 men with acute PE (mean age, 61 years; range, 33-83 years) (P = .01 for age). Images were acquired with a four-detector row computed tomographic scanner and 1.25-mm collimation. Two readers made independent attenuation measurements of the largest thrombus in each patient at a workstation. Statistical analysis included calculation of means and standard deviations, the t test, and the Bland-Altman test. RESULTS: Reader 1 found mean attenuation of 90 HU +/- 30 (range, 54-155 HU) for chronic PE and 33 HU +/- 15 (range, 6-63 HU) for acute PE (P < .001). Reader 2 found mean attenuation measurements of 83 HU +/- 32 (range, 32-135 HU) for chronic PE and 33 HU +/- 14 (range, 13-65 HU) for acute PE (P < .001). The mean attenuation for both readers was 33 HU for acute PE (95% confidence interval: 26, 41 HU) and 87 HU for chronic PE (95% confidence interval: 66, 107 HU). The Bland-Altman test demonstrated agreement between readers. CONCLUSION: The mean attenuation measurement in chronic PE is significantly higher than in acute PE.

The idiopathic interstitial pneumonias.

This review includes the seven idiopathic interstitial pneumonias defined by The American Thoracic Society and The European Respiratory Society 2002 publication. Idiopathic pulmonary fibrosis is the clinical term for usual interstitial pneumonia. The radiologic pattern includes basal and subpleural ground glass and reticular opacities and honeycomb lung. Nonspecific interstitial pneumonia is characterized with a radiologic pattern of subpleural and basal ground glass and reticular opacities. Cryptogenic organizing pneumonia is manifest radiologically by peribronchial ground glass opacities and subpleural consolidation. Acute interstitial pneumonia is the clinical term for idiopathic diffuse alveolar damage and the exudative phase is characterized radiologically with diffuse ground glass opacification and dependent consolidation with the additional feature of lung architectural distortion in the organizing phase. Respiratory bronchiolitis associated interstitial lung disease manifests as centrilobular ground glass opacities on CT. Desquamative interstitial pneumonia is characterized by ground glass opacities with lower zone predominance on CT. Lymphoid interstitial pneumonia manifests by ground glass opacities and nodular interlobular septal thickening on CT. The diagnosis of an IIP should be rendered ideally only after all clinicoradiologic-pathologic data have been reviewed.

CT angiography of pulmonary embolism: diagnostic criteria and causes of misdiagnosis.

Computed tomographic (CT) pulmonary angiography is becoming the standard of care at many institutions for the evaluation of patients with suspected pulmonary embolism. This pathologic condition, whether acute or chronic, causes both partial and complete intraluminal filling defects, which should have a sharp interface with intravascular contrast material. In acute pulmonary embolism that manifests as complete arterial occlusion, the affected artery may be enlarged. Partial filling defects due to acute pulmonary embolism are often centrally located, but when eccentrically located they form acute angles with the vessel wall. Chronic pulmonary embolism can manifest as complete occlusive disease in vessels that are smaller than adjacent patent vessels. Other CT pulmonary angiographic findings in chronic pulmonary embolism include evidence of recanalization, webs or flaps, and partial filling defects that form obtuse angles with the vessel wall. Factors that cause misdiagnosis of pulmonary embolism may be patient related, technical, anatomic, or pathologic. The radiologist needs to determine the quality of a CT pulmonary angiographic study and whether pulmonary embolism is present. If the quality of the study is poor, the radiologist should identify which pulmonary arteries have been rendered indeterminate and whether additional imaging is necessary.

Trends in thoracic radiology over a decade at a large academic medical center.

OBJECTIVE: To investigate thoracic radiology usage over and above the secular trends associated with hospital-wide changes in the number of patients over a decade. MATERIALS AND METHODS: We retrospectively reviewed administrative data from our 905-bed tertiary-care hospital between January 1, 1992, to December 31, 2001. Three points of entry to the radiology department were identified: inpatient (IP), outpatient (OP), and the emergency room (ER). The total numbers of patients, imaging studies, chest radiographs, chest CTs, CTs for pulmonary embolism, pulmonary angiograms, ventilation/perfusion scintigrams (V/Qs), lung biopsies, cardiac and chest MRIs, and FDG-PET scans for lung nodules and masses were collected. The significance of trends using linear regression analysis was evaluated. RESULTS: IP and OP numbers have significantly increased over a decade (P = 0.04 and P = 0.01 respectively); ER patient numbers have not. There has been an increase in the ratio of chest radiographs per patient arising from the ER area (P = 0.0002). All 3 areas demonstrated an increase in the ratio of chest CTs per patient: IP (P = 0.0002), OP (P = <0.0001), and ER (P = <0.0001). IP and ER areas demonstrated an increase in the ratio of CTs for pulmonary embolism per patient (P = 0.006, P = 0.04 respectively). There was a decrease in the ratios of pulmonary angiograms and V/Qs per IP (P = 0.02 & P = 0.0003 respectively). Cardiac MRIs per patient demonstrated an increase (IP P = 0.01, OP P = 0.02). FDG-PET for lung nodules and masses per patient demonstrated an increase in IP (P = 0.03) and OP (P = 0.003) areas. The total number of chest imaging studies divided by the total number of imaging studies demonstrated an increase in IP and ER areas (P = 0.02 and P = 0.02 respectively). CONCLUSION: There has been an increase in thoracic radiology usage above secular trends, particularly in the regions of chest CT and FDG-PET. CT is replacing more traditional techniques to diagnose pulmonary embolism for inpatients.