Density patterns in the normal lung as determined by computed tomography.

Rosenblum, Lawrence; Mauceri, R; Wellenstein, David E.; Thomas, F; Bassano, Daniel A.; Raasch, B N; Chamberlain, C. C.; Heitzman, E. Robert

doi:10.1148/radiology.137.2.7433674

Cited by 197 publications

(92 citation statements)

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“…24 This implies that we may have overestimated visual assessments in our study, because the contrast between a lesion and air is higher than that between a lesion and normal lung parenchyma. Thus, we might not be able to directly apply our results to low-dose CT screening for lung cancer.…”

Section: Discussionmentioning

confidence: 71%

Low-dose CT screening using hybrid iterative reconstruction: confidence ratings of diagnoses of simulated lesions other than lung cancer

Sakai

Yabuuchi

Kondo

et al. 2015

BJR

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Objective: To evaluate the confidence ratings of diagnoses of simulated lesions other than lung cancer on low-dose screening CT with hybrid iterative reconstruction (IR). Methods: Simulated lesions (emphysema, mediastinal masses and interstitial pneumonia) in a chest phantom were scanned by a 320-row area detector CT. The scans were performed by 64-row and 160-row helical scans at various dose levels and were reconstructed by filtered back projection (FBP) and IR. Emphysema, honeycombing and reticular opacity were visually scored on a four-point scale by six thoracic radiologists. The ground-glass opacity as a percentage of total lung volume (%GGO), CT value and contrast-to-noise ratio (CNR) of mediastinal masses were calculated. These scores and values were compared between FBP and IR. Wilcoxon's signed-rank test was used (p , 0.05). Interobserver agreements were evaluated by k statistics.Results: There were no significant differences in visual assessment. Interobserver agreement was almost perfect. CT values were almost equivalent between FBP and IR, whereas CNR with IR was significantly higher than that with FBP. %GGO significantly increased at low-dose levels with FBP; however, IR suppressed the elevation. Conclusion: The confidence ratings of diagnoses of simulated lesions other than lung cancer on low-dose CT screening were not degraded with hybrid IR compared with FBP. Advances in knowledge: Hybrid IR did not degrade the confidence ratings of diagnoses on visual assessment and differential diagnoses based on CT value of mediastinal masses, and it showed the advantage of higher GGO conspicuity at low-dose level. Radiologists can analyse images of hybrid IR alone on low-dose CT screening for lung cancer. INTRODUCTIONRecently, there have been discussions regarding the efficacy of lung cancer screening using low-dose CT. For example, the National Lung Screening Trial research team's 1 randomized clinical trial comparing the efficacies of chest radiographs and low-dose CT. They found that lung cancer screening using low-dose CT reduces lung cancer-related mortality in groups at high risk of lung cancer. With regard to dose-reduction techniques in CT, a new method of image reconstruction, iterative reconstruction (IR), has been developed and is now widely used for various clinical purposes. This technique has an advantage over the filtered back projection (FBP) method of image reconstruction in that FBP contains quantum noise; IR reduces this quantum noise by repeatedly comparing projection data, including quantum noise or primary reconstruction image data, with ideal anatomical and statistical models.

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Section: Discussionmentioning

confidence: 71%

Low-dose CT screening using hybrid iterative reconstruction: confidence ratings of diagnoses of simulated lesions other than lung cancer

Sakai

Yabuuchi

Kondo

et al. 2015

BJR

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“…Lung density varies between individuals, especially in cases of respiratory disease. Even for healthy patients, lung density and corresponding attenuation values depend on respiratory and body position (24), age, or smoking habits (25).…”

Section: Discussionmentioning

confidence: 99%

MRI-Based Attenuation Correction for Whole-Body PET/MRI: Quantitative Evaluation of Segmentation- and Atlas-Based Methods

Hofmann¹,

Bezrukov²,

Mantlik³

et al. 2011

J Nucl Med

259

211

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PET/MRI is an emerging dual-modality imaging technology that requires new approaches to PET attenuation correction (AC). We assessed 2 algorithms for whole-body MRI-based AC (MRAC): a basic MR image segmentation algorithm and a method based on atlas registration and pattern recognition (AT&PR). Methods: Eleven patients each underwent a whole-body PET/ CT study and a separate multibed whole-body MRI study. The MR image segmentation algorithm uses a combination of image thresholds, Dixon fat-water segmentation, and component analysis to detect the lungs. MR images are segmented into 5 tissue classes (not including bone), and each class is assigned a default linear attenuation value. The AT&PR algorithm uses a database of previously aligned pairs of MRI/CT image volumes. For each patient, these pairs are registered to the patient MRI volume, and machine-learning techniques are used to predict attenuation values on a continuous scale. MRAC methods are compared via the quantitative analysis of AC PET images using volumes of interest in normal organs and on lesions. We assume the PET/CT values after CT-based AC to be the reference standard. Results: In regions of normal physiologic uptake, the average error of the mean standardized uptake value was 14.1% 6 10.2% and 7.7% 6 8.4% for the segmentation and the AT&PR methods, respectively. Lesion-based errors were 7.5% 6 7.9% for the segmentation method and 5.7% 6 4.7% for the AT&PR method. Conclusion: The MRAC method using AT&PR provided better overall PET quantification accuracy than the basic MR image segmentation approach. This better quantification was due to the significantly reduced volume of errors made regarding volumes of interest within or near bones and the slightly reduced volume of errors made regarding areas outside the lungs.

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“…Alterations in regional blood flow affect lung density by increasing or decreasing blood volume in the capillary bed. Physiologic changes in blood flow secondary to gravitational effects have been well described [3]. In the supine patient the anterior-to-posterior gradient difference may be greater than 200 H. It is reasonable to assume that similar, if not greater, differences would be apparent in cases of mosaic oligemia due to occlusive pulmonary vascular disease.…”

Section: Casementioning

confidence: 98%