Computed tomography of thorax basics and its interpretation (1)

Presented by Dr. Radhika Ghongane
KMC, Manipal

1. Computed tomography of thorax- basics and its interpretation BY - Dr Radhika MODERATOR – Dr Rahul Magazine

2. INTRODUCTION CT is based on precise measurement of attenuation of a thinly collimated x-ray beam Attenuation : reduction in the intensity of the beam occurs due to scattering and absorption of x-ray photons by tissue Denoted by Hounsfield units

3. Types of CT-Scan

4. H igh resolution CT (HRCT) scan Performed using conventional CT scanner   Imaging parameters are chosen to maximize spatial resolution Takes widely spaced thin sections IV   contrast  are not used for HRCT   Technique is unsuitable for assessment of the soft tissue and blood vessels Plain CT HRCT

5. CT number ( Hounsfield units) x 1000 X -ray attenuation of each pixel is normalized to that of a test object containing pure water   CT number Tissue −1000 Air −700 to −900 Normal lung −100 Fat Water 20 to 60 Most soft tissues +100 Blood clot +1000 Bone

6. BASIC INTERPRETATION ( L ung window) Appearance/pattern Location Distribution Additional findings

7. CT APPERANCE/PATTERN 4 categories : Increased attenuation - Ground-glass opacity and consolidation Decreased attenuation Linear opacities Nodular opacities

8. Ground glass opacity ACUTE CAUSES – Pulmonary edema Pulmonary haemorrhage Pneumonia Increase in lung attenuation not obscuring underlying vessels Maybe physiological

9. Ground glass opacity CHRONIC CAUSES – Organizing pneumonia Pulmonary alveolar proteinosis Bronchoalveolar carcinoma

10. Consolidation Homogenous opacities with obscuration of pulmonary vessel Little/no volume loss Associated with air bronchogram Poorly defined margins HALO SIGN : Focal consolidation surrounded by GGO Eg . aspergillosis

11. Emphysema B ronchiectasis Sarcoidosis Hypersensitivity pneumonitis Vasculitis Air-trapping Decreased lung attenuation

12. Decreased lung attenuation Cystic disease Lymphangioleiomyomatosis Langerhans cell histiocytosis L ymphocytic interstitial pneumonitis P neumocystis pneumonia

13. CYLINDRICAL VARICOSE CYSTIC Decreased lung attenuation Types of Bronchiectasis

14. Reticular opacities Thickening of interstitial fibers of lung by fluid, fibrous tissue or cells CAUSES - ILD Pulmonary edema Lymphangitic spread of tumor Sarcoidosis

15. Nodular opacities Single/multiple CAUSES - Malignancy Silicosis, CWP Endobronchial spread of infection Garnuloma Location- centrilobular , perilymphatic or random

16. Location Centrilobular Perilymphatic R andom

17. 1. Centrilobular In or near the center of the secondary pulmonary lobule Spares pleural surfaces Indicative of endobronchial spread Small airway inflammatory diseases - Poorly defined, poorly marginated GGO Bronchiolar filling - Mucoid impaction in bronchioles

18. Centrilobular BRONCHIOLAR FILLING ;TREE-IN-BUD SMALL AIRWAY INFLAMMATORY DISEASES ( RB-ILD )

19. 2. Perilymphatic Within interstitial septa and bronchovascular compartments Subpleural location, particularly in relation to the fissures

20. Lymphatic system involvement 1. Pulmonary interstitial edema 2. Sarcoidosis 3. Lymphangitic carcinomatosis SUB-PLEURAL PERI-BRONCHOVASCULAR

21. 3. Random Hematogenous dissemination of metastases or infection Example - Miliary tuberculosis

22. DISTRIBUTION According to lobes – Upper Lower Diffuse According to region – Central Peripheral

23. Upper lobe predominant Langerhans cell histiocytosis Sarcoidosis Silicosis Coal workers’ pneumoconiosis (CWP) Tuberculosis Cystic fibrosis Centrilobular emphysema

24. Lower lobe predominant ILD-UIP/IPF Asbestosis Organizing pneumonia Alveolar haemorrhage Pulmonary edema Panlobular emphysema

25. Diffuse involvement Hypersensitivity pneumonitis Lymphangioleiomyomatosis Lymphangitic spread of tumor

26. Central Sarcoidosis Silicosis CWP Lymphangitic spread of tumor Pulmonary alveolar proteinosis

27. Peripheral ILD-UIP/IPF ILD-NSIP Acute interstitial pneumonia Hematogenous metastasis Pulmonary embolism

28. Mediastinal window

29. Mediastinal window Lymph node stations

30. Mediastinal staging

31. REFERENCES Fishman’s pulmonary diseases and disorders 5 th edition Murray and Nadel’s textbook of respiratory medicine 6 th edition Radiopedia.org

32. THANK YOU !