Radiology Thoracic Imaging

[Thoracic Imaging] Estimating Long-term Effectiveness of Lung Cancer Screening in the Mayo CT Screening Study

2008-06-19

Purpose: To use individual-level data provided from the single-arm study of helical computed tomographic (CT) screening at the Mayo Clinic (Rochester, Minn) to estimate the long-term effectiveness of screening in Mayo study participants and to compare estimates from an existing lung cancer simulation model with estimates from a different modeling approach that used the same data.

Materials and Methods: The study was approved by institutional review boards and was HIPAA compliant. Deidentified individual-level data from participants (1520 current or former smokers aged 50–85 years) in the Mayo Clinic helical CT screening study were used to populate the Lung Cancer Policy Model, a comprehensive microsimulation model of lung cancer development, screening findings, treatment results, and long-term outcomes. The model predicted diagnosed cases of lung cancer and deaths per simulated study arm (five annual screening examinations vs no screening). Main outcome measures were predicted changes in lung cancer–specific and all-cause mortality as functions of follow-up time after simulated enrollment and randomization.

Results: At 6-year follow-up, the screening arm had an estimated 37% relative increase in lung cancer detection, compared with the control arm. At 15-year follow-up, five annual screening examinations yielded a 9% relative increase in lung cancer detection. The relative reduction in cumulative lung cancer–specific mortality from five annual screening examinations was 28% at 6-year follow-up (15% at 15 years). The relative reduction in cumulative all-cause mortality from five annual screening examinations was 4% at 6-year follow-up (2% at 15 years).

Conclusion: Screening may reduce lung cancer–specific mortality but may offer a smaller reduction in overall mortality because of increased competing mortality risks associated with smoking.

[Thoracic Imaging] Management of Small (3-5-mm) Pulmonary Nodules at Chest CT: Global Survey of Thoracic Radiologists

Jeudy, J., White, C. S., Munden, R. F., Boiselle, P. M. — 2008-05-16

Purpose: To prospectively determine management strategies used by international thoracic radiologists in evaluation of small (3–5-mm) pulmonary nodules at chest computed tomography (CT).

Materials and Methods: Institutional review board exemption was granted for this study, which included consenting participants. An electronic survey was sent to members of major thoracic radiology societies in North America, Europe, and Asia. The main part of the survey consisted of four management questions with clinical scenarios. Associations between recommendations and years of experience, location in a region endemic for granulomatous disease, country, and practice type were assessed. Univariate analysis was performed to determine differences in follow-up recommendations on the basis of patient characteristics, percentage of chest CT scans obtained at follow-up, years of experience in radiology, and professional society affiliation of respondents. Differences in categorical variables were examined by using Pearson ² and Fisher exact tests.

Results: Two hundred two (25%) of approximately 800 online surveys were completed. Surveys from respondents from the United States comprised 61% of completed surveys. Median experience of respondents was 11–20 years. Fifty-two percent practice in an area endemic for granulomatous disease. Only 35% of practices have a policy in place for nodule management. In scenarios in which patients had a low likelihood of malignancy, respondents' preferential recommendation was short-term CT follow-up (3–6 months) rather than intermediate-term CT follow-up (12 months) for patients older than 40 years compared with their recommendation in patients younger than 40 years, in whom recommendations for short- or intermediate-term follow-up were roughly equal. In scenarios in which patients had a high risk of malignancy, follow-up was also strongly favored instead of biopsy, with short-term follow-up more commonly advocated. Location in an area endemic for granulomatous disease and years of experience also influenced recommendations.

Conclusion: Globally, the most common recommendation for CT evaluation of nodules is short-term follow-up, with a tendency toward less aggressiveness in scenarios in which patients had lower risk of malignancy and increased aggressiveness in scenarios in which patients had higher risk of malignancy.

Supplemental material: http://radiology.rsnajnls.org/cgi/content/full/2473061514/DC1

[Thoracic Imaging] D-Dimer Assay to Exclude Pulmonary Embolism in High-Risk Oncologic Population: Correlation with CT Pulmonary Angiography in an Urgent Care Setting

King, V., Vaze, A. A., Moskowitz, C. S., Smith, L. J., Ginsberg, M. S. — 2008-05-16

Purpose: To prospectively evaluate (a) the diagnostic performance of D-dimer assay for pulmonary embolism (PE) in an oncologic population by using computed tomographic (CT) pulmonary angiography as the reference standard, (b) the association between PE location and assay sensitivity, and (c) the association between assay results and clinical factors that raise suspicion of PE.

Materials and Methods: This HIPAA-compliant study had institutional review board approval; informed consent was obtained. Five hundred thirty-one consecutive patients were clinically suspected of having PE; 201 were enrolled (72 men, 129 women; median age, 61 years) and underwent CT pulmonary angiography and D-dimer assay. Relevant clinical history, symptoms, and signs were recorded. CT images were interpreted, and the location of emboli was recorded. The negative predictive value (NPV), positive predictive value (PPV), sensitivity, specificity, and diagnostic likelihood ratios of the D-dimer assay results were calculated.

Results: Forty-three patients (21%) had pulmonary emboli at CT. D-Dimer results were positive in 171 patents (85%). The NPV and sensitivity were 97% and 98%, respectively. The specificity and PPV were 18% and 25%, respectively. No association was shown between clinical history, symptoms, or signs and NPV, PPV, sensitivity, or specificity or between location of PE and sensitivity.

Conclusion: D-Dimer results have high NPV and sensitivity for PE in oncologic patients and, if negative, can be used to exclude PE in this population. Combining the assay with clinical symptoms and signs did not substantially change NPV, PPV, sensitivity, or specificity.

[Thoracic Imaging] Regional Heterogeneity of Air Trapping at Expiratory Thin-Section CT of Patients with Bronchiolitis: Potential Implications for Dose Reduction and CT Protocol Planning

Bankier, A. A., Mehrain, S., Kienzl, D., Weber, M., Estenne, M., Gevenois, P. A. — 2008-05-16

Purpose: To prospectively determine whether the regional distribution of air trapping in patients with suspected or overt bronchiolitis is heterogeneous, and to determine the effect that a simulated reduction of computed tomographic (CT) sections and of scanned anatomic regions would have on the assessment of the extent of air trapping.

Materials and Methods: For this Ethical Committee–approved study, multi–detector row CT (collimation, 4 x 1 mm; rotation time, 0.5 second; 140 kVp; and 80 effective mAs) was performed in 47 lung transplant recipients (23 women, 24 men; mean age, 41 years ± 12 [standard deviation]; 18 without bronchiolitis, 18 with potential bronchiolitis, and 11 with bronchiolitis, as determined by lung function measurements). Images were reconstructed with a thickness of 1 mm at an increment of 10 mm. The extent of air trapping in the upper, middle, and lower lung regions was correlated. Differences between regions and the interaction between patients and regions were tested with an analysis of variance. The extent of air trapping was calculated for six simulated examination protocols.

Results: Correlations between the upper and middle (r = 0.930), the upper and lower (r = 0.756), and the middle and lower lung regions (r = 0.863) were significant (P < .001). The extent of air trapping increased from the upper to the lower lung region, with significant differences between regions (P < .001). There was a significant interaction between patients and lung regions (P < .001). Simulated examination protocols resulted in significantly different extents of air trapping (P < .001).

Conclusion: The regional distribution of the extent of air trapping in suspected or overt bronchiolitis is heterogeneous. Because the extent of air trapping can depend on the examination protocol, identical protocols are needed when air trapping is being compared within and between patients.

[Thoracic Imaging] Central Veins of the Chest: Evaluation with Time-resolved MR Angiography

2008-04-22

Purpose: To retrospectively assess the diagnostic performance of time-resolved magnetic resonance (MR) angiography in the detection of stenoses and occlusions in the central veins of the chest, with angiographic and surgical findings and consensus readings serving as the reference standard.

Materials and Methods: Institutional review board approval was obtained, and the informed consent requirement was waived for this HIPAA-compliant study. Retrospective analysis was performed with 27 consecutive patients (12 male, 15 female; age range, 16–67 years) who underwent MR venography of the central veins. Six radiologists with varying levels of experience interpreted the studies. For each study, the readers were presented with time-resolved maximum intensity projection (MIP) images only, high-spatial-resolution images only, or both. Sensitivity and specificity were calculated for detection of stenoses and occlusions, as well as for confidence levels, study interpretation time, and determination of the side of the body on which upper extremity contrast material injection was performed.

Results: The addition of time-resolved angiographic images to the high-spatial-resolution images resulted in improved specificity in the detection of venous occlusions (0.99 vs 0.96, P = .03), in reader confidence (P < .001), and in the ability to infer the side of injection (83% correct compared with 32% correct, P < .001), without increasing the average time required for study interpretation. Use of time-resolved angiographic data sets as a stand-alone technique had high sensitivity (0.95) but only moderate specificity (0.56) in the detection of venous stenoses or occlusions.

Conclusion: Time-resolved angiographic images are a useful adjunct to high-spatial-resolution images in the evaluation of central venous stenoses and occlusions.

[Thoracic Imaging] Nonspecific Interstitial Pneumonia and Idiopathic Pulmonary Fibrosis: Changes in Pattern and Distribution of Disease over Time

2008-03-27

Purpose: To retrospectively assess the change in disease pattern of nonspecific interstitial pneumonia (NSIP) and idiopathic pulmonary fibrosis (IPF) findings seen at thin-section computed tomography (CT) at long-term follow-up and to compare the same with initial findings at CT.

Materials and Methods: The study included 48 patients (28 men, 20 women; mean age, 57.5 years) with biopsy-proved NSIP (n = 23) or IPF (n = 25) who underwent CT at initial diagnosis and at follow-up 34–155 months later. The CT scans were randomized and reviewed by two independent thoracic radiologists for pattern and distribution of ground-glass opacity (GGO), reticulation, traction bronchiectasis and bronchiolectasis, and honeycombing. Statistical analysis was performed by using nonparametric methods and univariate logistic regression.

Results: Follow-up CT in patients with NSIP showed marked decrease in the extent of GGO, increase in reticulation, and a greater likelihood of peripheral distribution (all P < .05). At presentation, the CT findings were interpreted as suggestive of NSIP in 18 of 23 patients with NSIP and indeterminate or suggestive of IPF in five. In five (28%) of 18 patients with initial findings suggestive of NSIP, the follow-up CT scans were interpreted as more suggestive of IPF. No CT features seen at presentation allowed distinction between patients with NSIP that maintained an NSIP pattern at follow-up and those that progressed to an IPF pattern.

Conclusion: At follow-up CT, 28% of patients with initial CT findings suggestive of NSIP progressed to findings suggestive of IPF. Similar initial CT findings for NSIP may have different imaging outcomes.