Incidental pulmonary nodules on cardiac computed tomography: prognosis and use

BACKGROUND

Small asymptomatic lung nodules are found frequently in the course of cardiac computed tomography (CT) scanning. However, the utility of assessing and reporting incidental findings in healthy, asymptomatic subjects is unknown.

METHODS

The sample comprised 1023 60- to 69-year-old subjects free of clinical cardiovascular disease and cancer who participated in the Atherosclerotic Disease, VAscular functioN and genetiC Epidemiology Study. All subjects underwent cardiac CT for determination of coronary calcium between 2001 and 2004, and the first 459 subjects were assessed for incidental pulmonary findings. We used health plan clinical databases to ascertain 24-month health care use and clinical outcomes.

RESULTS

Noncalcified pulmonary nodules were reported in 81 of 459 subjects (18%). Chest CT was performed on 78% of participants in the 24 months after notification, compared with 2.5% in the previous 24 months. Chest x-ray use increased from 28% to 49%. The mean number of chest CT scans per subject was 1.3 (range, 0-5). Although no malignant lesions were diagnosed in the group who had pulmonary findings read, 1 lung cancer case was diagnosed in the group who did not have lung findings read. Among the 63 participants followed up by CT, the original lesion was not identified in 22 participants (35%), the lesion had decreased or remained stable in 39 participants (62%), and there was interval growth in 2 participants (3%).

CONCLUSION

Reporting noncalcified pulmonary nodules resulted in substantial rescanning that overwhelmingly revealed resolution or stability of pulmonary nodules, arguing for benign processes.

Adaptive border marching algorithm: automatic lung segmentation on chest CT images

Segmentation of the lungs in chest-computed tomography (CT) is often performed as a preprocessing step in lung imaging. This task is complicated especially in presence of disease. This paper presents a lung segmentation algorithm called adaptive border marching (ABM). Its novelty lies in the fact that it smoothes the lung border in a geometric way and can be used to reliably include juxtapleural nodules while minimizing oversegmentation of adjacent regions such as the abdomen and mediastinum. Our experiments using 20 datasets demonstrate that this computational geometry algorithm can re-include all juxtapleural nodules and achieve an average oversegmentation ratio of 0.43% and an average under-segmentation ratio of 1.63% relative to an expert determined reference standard. The segmentation time of a typical case is under 1min on a typical PC. As compared to other available methods, ABM is more robust, more efficient and more straightforward to implement, and once the chest CT images are input, there is no further interaction needed from users. The clinical impact of this method is in potentially avoiding false negative CAD findings due to juxtapleural nodules and improving volumetry and doubling time accuracy.

Susceptibility locus for clinical and subclinical coronary artery disease at chromosome 9p21 in the multi-ethnic ADVANCE study

A susceptibility locus for coronary artery disease (CAD) at chromosome 9p21 has recently been reported, which may influence the age of onset of CAD. We sought to replicate these findings among white subjects and to examine whether these results are consistent with other racial/ethnic groups by genotyping three single nucleotide polymorphisms (SNPs) in the risk interval in the Atherosclerotic Disease, Vascular Function, and Genetic Epidemiology (ADVANCE) study. One or more of these SNPs was associated with clinical CAD in whites, U.S. Hispanics and U.S. East Asians. None of the SNPs were associated with CAD in African Americans although the power to detect an odds ratio (OR) in this group equivalent to that seen in whites was only 24-30%. ORs were higher in Hispanics and East Asians and lower in African Americans, but in all groups the 95% confidence intervals overlapped with ORs observed in whites. High-risk alleles were also associated with increased coronary artery calcification in controls and the magnitude of these associations by racial/ethnic group closely mirrored the magnitude observed for clinical CAD. Unexpectedly, we noted significant genotype frequency differences between male and female cases (P = 0.003-0.05). Consequently, men tended towards a recessive and women tended towards a dominant mode of inheritance. Finally, an effect of genotype on the age of onset of CAD was detected but only in men carrying two versus one or no copy of the high-risk allele and presenting with CAD at age >50 years. Further investigations in other populations are needed to confirm or refute our findings.

CT angiography effectively evaluates extremity vascular trauma

Traditionally, conventional arteriography is the diagnostic modality of choice to evaluate for arterial injury. Recent technological advances have resulted in multidetector, fine resolution computed tomographic angiography (CTA). This study examines CTA for evaluation of extremity vascular trauma compared with conventional arteriography. Our hypothesis is that CTA provides accurate and timely diagnosis of peripheral vascular injuries and challenges the gold standard of arteriogram. Traumatic extremity injuries over a 5-year period were identified using a Level I trauma center registry and radiology database. Information collected included patient demographics, mechanism, imaging modality, vascular injuries, management, and follow-up. Two thousand two hundred and fifty-one patients were identified with extremity trauma. Twenty-four patients were taken directly to the operating room for evaluation and management of vascular injuries. Fifty-two underwent vascular imaging. Fourteen patients had conventional arteriograms with 13 abnormal studies: 7 were managed operatively, 2 embolized, and 4 observed. Thirty-eight patients underwent CTA with 17 abnormal scans: 9 were managed operatively, 3 embolized, and 5 observed. There were no false negatives or missed injuries. CTA provides accurate peripheral vascular imaging while additionally offering advantages of noninvasiveness and immediate availability. Secondary to these advantages, CTA has supplanted arteriography for initial radiographic evaluation of peripheral vascular injuries at our Level I trauma center. This study supports CTA as an effective alternative to conventional arteriography in assessing extremity vascular trauma.

Flattening the abdominal aortic tree for effective visualization

We developed a novel visualization method for providing an uncluttered view of the abdominal aorta and its branches. The method abstracts the complex geometry of vessels using a convex primitive, and uses a sweep line algorithm to find a suboptimal placement of the primitive. The method was evaluated using 10 CT angiography datasets and resulted in a clear visualization with all cluttering intersections removed. The method can be used to convey clinical findings, including lumen patency and lesion locations, in a single two-dimensional image.

Semiautomated quantification of the mass and distribution of vascular calcification with multidetector CT: method and evaluation

Institutional review board approval was obtained for this HIPAA-compliant study. Informed consent was obtained for prospective evaluation in 21 asymptomatic volunteers (10 women, 11 men; mean age, 60 years) but waived for retrospective (10 patients with and five patients without disease) evaluation. Prospective validation was in phantoms. Quantification of mass and calcium distribution was performed with fast semiautomated method, without calibration. For actual versus measured mass in phantoms, R(2) was 0.98; absolute and percentage errors were 1.2 mg and 9.1%, respectively. In asymptomatic volunteers, mean interscan variability for calcium mass quantification in extracoronary arteries was 24.9 mg; mean was 991 units for Agatston scoring. In coronary arteries, mean variability was 5.5 mg; mean Agatston variability was 27.7 units. At retrospective computed tomography, mean total calcified mass was 321.3 mg. Accurate quantification of mass and distribution of calcification in simulated arteries with this method can be applied in vivo, with low interscan variability.

Ethnic differences in coronary artery calcium in a healthy cohort aged 60 to 69 years

Measurement of coronary artery calcium (CAC) has been proposed as a screening tool, but CAC levels may differ according to race and gender. Racial/ethnic and gender distributions of CAC were examined in a randomly selected cohort of 60- to 69-year-old healthy subjects. Demographic, race/ethnicity (R/E), and clinical characteristics and assessment of CAC were collected. There were 723 white/European, 105 African-American, 73 Hispanic, and 67 East Asian subjects (597 men, 369 women) included in this analysis. Men had a significantly higher prevalence of any CAC (score>10) than women (76% vs 41%; p<0.0001). For men, the unadjusted odds of having any CAC was 2.2 (95% confidence interval [CI] 1.3 to 3.8) for whites compared with African-Americans. For women, CAC scores were not significantly different across ethnic groups. After adjustment for coronary risk factors, African-American and East Asian R/E remained associated with a lower prevalence of CAC in men (adjusted odds ratios [ORs] 0.33 and 0.47, respectively), as well as older age (OR 1.2, 95% CI 1.1 to 1.3), known hyperlipidemia (OR 1.7, 95% CI 1.1 to 2.7), and history of hypertension (OR 2.2, 95% CI 1.4 to 3.3). In women, Asian R/E (OR 2.5, 95% CI 1.1 to 5.7), history of smoking (adjusted OR 2.8, 95% CI 1.3 to 6.1), and known hyperlipidemia (adjusted OR 2.0, 95% CI 1.3 to 3.1) were associated with a higher prevalence of CAC independent of other risk factors. In conclusion, our data indicate that the presence of CAC varied significantly across selected race/ethnic groups independent of traditional cardiovascular risk factors.

Registration of lung nodules using a semi-rigid model: method and preliminary results

The tracking of lung nodules across computed tomography (CT) scans acquired at different times for the same patient is helpful for the determination of malignancy. We are developing a nodule registration system to facilitate this process. We propose to use a semi-rigid method that considers principal structures surrounding the nodule and allows relative movements among the structures. The proposed similarity metric, which evaluates both the image correlation and the degree of elastic deformation amongst the structures, is maximized by a two-layered optimization method, employing a simulated annealing framework. We tested our method by simulating five cases that represent physiological deformation as well as different nodule shape/size changes with time. Each case is made up of a source and target scan, where the source scan consists of a nodule-free patient CT volume into which we inserted ten simulated lung nodules, and the target scan is the result of applying a known, physiologically based nonrigid transformation to the nodule-free source scan, into which we inserted modified versions of the corresponding nodules at the same, known locations. Five different modification strategies were used, one for each of the five cases: (1) nodules maintain size and shape, (2) nodules disappear, (3) nodules shrink uniformly by a factor of 2, (4) nodules grow uniformly by a factor of 2, and (5) nodules grow nonuniformly. We also matched 97 real nodules in pairs of scans (acquired at different times) from 12 patients and compared our registration to a radiologist's visual determination. In the simulation experiments, the mean absolute registration errors were 1.0+/-0.8 mm (s.d.), 1.1+/-0.7 mm (s.d.), 1.0+/-0.7 mm (s.d.), 1.0+/-0.6 mm (s.d.), and 1.1+/- 0.9 mm (s.d.) for the five cases, respectively. For the 97 nodule pairs in 12 patient scans, the mean absolute registration error was 1.4+/-0.8 mm (s.d.).

Plasma leptin levels and coronary artery calcification in older adults

CONTEXT

Leptin is associated with adiposity and insulin resistance and may play a direct role in vascular calcification. It is unclear, however, whether leptin is an independent predictor of atherosclerotic burden.

OBJECTIVE

The aim of this study was to examine the association between plasma leptin and coronary artery calcification (CAC) in an ethnically diverse cohort of older adult men and women free of clinical cardiovascular disease.

DESIGN

This was a cross-sectional study with data collection between January 2002 and February 2004 as part of the ADVANCE Study.

SETTING

The study was conducted at an integrated health care delivery system in Northern California.

PARTICIPANTS

Participants included 949 men and women aged 60-69 yr old.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURE

The main outcome measure was CAC by multidetector row computed tomography.

RESULTS

In ordinal logistic regression, plasma leptin levels were positively associated with extent of CAC independently of age, race/ethnicity, and smoking status in women (odds ratio of higher CAC for the sex-specific upper tertile vs. lower tertile = 1.81; 95% confidence interval, 1.10-3.00) but not in men (odds ratio = 1.29; 95% confidence interval = 0.89-1.86). However, this association was explained by metabolic risk factors and adiposity measures.

CONCLUSIONS

Our findings support a role of leptin on vascular calcification in women but, in our sample of older adults, the association between leptin and CAC was not independent of other cardiac risk factors.

CT Angiography of Peripheral Arterial Occlusive Disease

Lower extremity computed tomography angiography (CTA) is an effective, noninvasive, and robust imaging modality that is being used increasingly to evaluate patients with peripheral arterial occlusive disease (PAOD). It is important for vascular and interventional radiologists, and vascular surgeons to be familiar with the strengths and limitations, diagnostic accuracy, and practical application of lower extremity CTA. In this article, we review the technical principles of image acquisition, visualization techniques to effectively interpret the large volumetric datasets generated, and the current practical application of lower extremity CTA with respect to PAOD.

Fully automated system for three-dimensional bronchial morphology analysis using volumetric multidetector computed tomography of the chest

Recent advancements in computed tomography (CT) have enabled quantitative assessment of severity and progression of large airway damage in chronic pulmonary disease. The advent of fast multidetector computed tomography scanning has allowed the acquisition of rapid, low-dose 3D volumetric pulmonary scans that depict the bronchial tree in great detail. Volumetric CT allows quantitative indices of bronchial airway morphology to be calculated, including airway diameters, wall thicknesses, wall area, airway segment lengths, airway taper indices, and airway branching patterns. However, the complexity and size of the bronchial tree render manual measurement methods impractical and inaccurate. We have developed an integrated software package utilizing a new measurement algorithm termed mirror-image Gaussian fit that enables the user to perform automated bronchial segmentation, measurement, and database archiving of the bronchial morphology in high resolution and volumetric CT scans and also allows 3D localization, visualization, and registration.

An abdominal aortic aneurysm segmentation method: level set with region and statistical information

We present a system for segmenting the human aortic aneurysm in CT angiograms (CTA), which, in turn, allows measurements of volume and morphological aspects useful for treatment planning. The system estimates a rough "initial surface," and then refines it using a level set segmentation scheme augmented with two external analyzers: The global region analyzer, which incorporates a priori knowledge of the intensity, volume, and shape of the aorta and other structures, and the local feature analyzer, which uses voxel location, intensity, and texture features to train and drive a support vector machine classifier. Each analyzer outputs a value that corresponds to the likelihood that a given voxel is part of the aneurysm, which is used during level set iteration to control the evolution of the surface. We tested our system using a database of 20 CTA scans of patients with aortic aneurysms. The mean and worst case values of volume overlap, volume error, mean distance error, and maximum distance error relative to human tracing were 95.3% +/- 1.4% (s.d.); worst case = 92.9%, 3.5% +/- 2.5% (s.d.); worst case = 7.0%, 0.6 +/- 0.2 mm (s.d.); worst case = 1.0 mm, and 5.2 +/- 2.3 mm (s.d.); worst case = 9.6 mm, respectively. When implemented on a 2.8 GHz Pentium IV personal computer, the mean time required for segmentation was 7.4 +/- 3.6 min (s.d.). We also performed experiments that suggest that our method is insensitive to parameter changes within 10% of their experimentally determined values. This preliminary study proves feasibility for an accurate, precise, and robust system for segmentation of the abdominal aneurysm from CTA data, and may be of benefit to patients with aortic aneurysms.

CT angiography of peripheral arterial disease

Lower-extremity computed tomographic (CT) angiography (ie, peripheral CT angiography) is increasingly used to evaluate patients with peripheral arterial disease. It is therefore increasingly important for all vascular specialists to become familiar with the strengths and limitations of this new technique. The aims of this review are to explain the principles of scanning and injection technique for a wide range of CT scanners, to explain and illustrate the properties of current image postprocessing tools for effective visualization and treatment planning, and to provide an overview of current clinical applications of peripheral CT angiography.

Angiographic imaging of the lower extremities with multidetector CT

Multidetector CT (MDCT) has improved imaging of the arteries in the lower extremities. The main advantages of this novel technology are the exceptionally fast scan times, high spatial resolution, increased anatomic coverage, and capability to generate high-quality multiplanar reformations and three-dimensional (3-D) renderings from raw data that can be reprocessed easily and quickly. The applications of MDCT in imaging the lower extremities are multiple and varied. They include the evaluation of peripheral arterial occlusive and aneurysmal disease, the patency and integrity of bypass grafts, and arterial injury owing to trauma. This article describes the techniques of lower extremity MDCT angiography and its use in a few clinical applications.

Detection of endograft fractures with multidetector row computed tomography

Delayed endograft metallic strut failures detected in vivo with multidetector row computed tomography (MDCT) are reported in two patients who underwent endovascular abdominal aortic aneurysm repair with AneuRx and Talent endografts. In both instances, nitinol fractures were associated with proximal migration and type I endoleak. In both cases, the metallic strut fractures were detected with transverse sections from 16-channel MDCT angiograms and confirmed by using volume rendering. These cases highlight the previously unreported ability of thin-section, high-resolution MDCT angiography to detect endograft strut fractures.

Primary Interpretation of Thoracic MDCT Images Using Coronal Reformations

OBJECTIVE

The objective of this study was to evaluate the accuracy and efficiency of primary interpretation of thoracic MDCT using coronal reformations as compared with transverse images.

SUBJECTS AND METHODS

Fifty patients (18 females, 32 males; age range, 15-93 years; mean age, 63.6 years) underwent 4-MDCT of the chest (detector width, 1 mm; beam pitch, 1.5). Contrast material was administered in 20 of the 50 patients. Coronal and transverse sections were reformatted into 5-mm-thick sections at 3.5-mm intervals. All available image and clinical data consensually reviewed by two thoracic radiologists served as the reference standard. Subsequently, three other thoracic radiologists independently evaluated reformatted coronal and transverse images at two separate review sessions. Each image set was assessed in 58 categories for abnormalities of the lungs, mediastinum, pleura, chest wall, diaphragm, abdomen, and skeleton. Interpretation times and number of images assessed were recorded. Sensitivity, specificity, and interobserver concordance were calculated. Differences in mean sensitivities and specificities were evaluated with Wilcoxon's signed rank test.

RESULTS

The most common findings identified were pulmonary nodules (n = 73, transverse images; n = 72, coronal images) and emphysema (n = 45, transverse; n = 40, coronal). The mean detection sensitivity of all lesions was significantly (p = 0.001) lower on coronal (44% +/- 26% [SD]) than on transverse (51% +/- 22%) images, whereas the mean detection specificity was significantly (p = 0.005) higher (96% +/- 5% vs 95% +/- 6%, respectively). Reporting findings for significantly (p < 0.001) fewer coronal images (mean, 63.0 +/- 4.6 images) than transverse images (mean, 91.9 +/- 8.8 images) took significantly (p = 0.025) longer (mean, 263 +/- 56 sec vs 238 +/- 45 sec, respectively).

CONCLUSION

Primary interpretation of thoracic MDCT is less sensitive and more time-consuming using 5-mm-thick coronal reformations as compared with transverse images.