Chest imaging includes use of:
Nuclear scanning, including positron emission tomography (PET) scanning
(See also Principles of Radiologic Imaging.)
Conventional Chest Radiograph Techniques
Conventional radiograph techniques that are used to image the chest and surrounding structures include:
Plain radiographs
Fluoroscopy
Chest radiograph
Plain chest radiographs provide images of structures in and around the thorax and are most useful for identifying abnormalities in the heart, lung parenchyma, pleura, chest wall, diaphragm, mediastinum, and hilum. They are usually the initial test performed to evaluate the lungs.
The standard chest radiograph is taken from back to front (posteroanterior view) to minimize x-ray scatter that could artifactually enlarge the cardiac silhouette, and from the side of the thorax (lateral view).
Lordotic or oblique views can be obtained to evaluate pulmonary nodules or to clarify abnormalities that may be due to superimposed structures, although chest CT provides more information and has largely superseded these views.
Lateral decubitus views may be used to distinguish free-flowing from loculated pleural effusion, but chest CT or ultrasound can provide more information.
End-expiratory views can be used to detect small pneumothoraces.
Chest radiographs taken with portable machines (usually anteroposterior views) are almost always suboptimal and should be used only when patients are too ill to be transported to the radiology department.
Screening chest radiographs are almost never indicated; one exception is in asymptomatic patients with positive tuberculin skin test results, in whom a single posteroanterior chest radiograph without a lateral view is used to make decisions regarding additional diagnostic studies and/or treatment for pulmonary tuberculosis.
Chest fluoroscopy
Chest fluoroscopy is the use of a continuous x-ray beam to image movement. It is useful for detecting unilateral diaphragmatic paralysis. During a sniff test, in which the patient is instructed to forcibly inhale through the nose (or sniff), a paralyzed hemidiaphragm moves cranially (paradoxically) while the unaffected hemidiaphragm moves caudally.
Several ancillary procedures such as bronchoscopy can be performed with fluoroscopic guidance.
Chest Computed Tomography (CT)
CT defines intrathoracic structures and abnormalities more clearly than does a chest radiograph.
Chest CT is normally performed at full inspiration. Aeration of the lungs during imaging provides the best views of the lung parenchyma, airways, and vasculature, and of abnormal findings such as masses, infiltrates, or fibrosis.
Low dose chest CT is recommend annually to screen high risk patients for lung cancer.
Images obtained with the patient in the prone position can help differentiate dependent atelectasis (which changes with changes in body position) from lung disorders that cause ground-glass attenuation in the dependent dorsal parts of the lungs, which persists despite changes in patient position (eg, fibrosis due to idiopathic pulmonary fibrosis, asbestosis, or systemic sclerosis).
CT angiography
CT angiography uses a bolus of an IV radiopaque contrast agent to highlight the pulmonary arteries, which is useful in diagnosis of pulmonary embolism.
Contrast agent load is comparable to that with conventional angiography, but the test is quicker and less invasive. CT angiography provides sufficient accuracy for the detection of pulmonary emboli, and it is typically used instead of conventional pulmonary angiography except in patients unable to tolerate contrast agents, in whom ventilation/perfusion (V/Q) scanning may be used.
Magnetic Resonance Imaging (MRI) of the Chest
MRI has a relatively limited role in pulmonary imaging but is preferred over CT in specific circumstances, such as assessment of:
Superior sulcus tumors
Possible cysts
Lesions that abut the chest wall
MRI or magnetic resonance angiography (MRA) of the chest can also be used to diagnose aortic dissection.
In patients with suspected pulmonary embolism in whom IV contrast agents cannot be used, MRI can sometimes identify large proximal emboli but does not detect smaller or more distal emboli well.
Advantages include absence of radiation exposure, excellent visualization of vascular structures, lack of artifact due to bone, and excellent soft-tissue contrast.
Disadvantages include respiratory and cardiac motion, the time it takes to do the procedure, the expense of MRI, and the occasional presence of contraindications.
The presence of ferromagnetic objects in the patient's eye or brain typically preclude MRI. The presence of a permanent pacemaker or internal cardioverter-defibrillator (ICD), and some vascular coils and plugs, may be considered a relative contraindication and/or require specific safety protocols (see MRI Safety and the manufacturer's instructions for the specific implant). Many pacemakers and implanted cardioverter-defibrillators (ICDs) can be safely used in MRI machines under specific conditions (MRI-conditional) (1, 2), and many coils and plugs are MRI-safe. Even devices not labeled as MRI-conditional are often safe when proper protocols are followed (3). In addition to safety concerns, implanted metallic objects can cause imaging artifact.
Gadolinium, when used as a contrast agent for MRI, carries the risk of causing nephrogenic systemic fibrosis in patients with acute kidney injury, those with stage 4 or 5 chronic kidney disease, or those receiving kidney replacement therapy (dialysis) (4). Gadolinium may be harmful to a fetus and is generally avoided in pregnancy (5, 6).
Chest MRI references
1. Indik JH, Gimbel JR, Abe H, et al. 2017 HRS expert consensus statement on magnetic resonance imaging and radiation exposure in patients with cardiovascular implantable electronic devices. Heart Rhythm. 2017;14(7):e97-e153. doi:10.1016/j.hrthm.2017.04.025
2. Wan EY, Rogers AJ, Lavelle M, et al. Periprocedural Management and Multidisciplinary Care Pathways for Patients With Cardiac Implantable Electronic Devices: A Scientific Statement From the American Heart Association. Circulation. 2024;150(8):e183-e196. doi:10.1161/CIR.0000000000001264
3. Nazarian S, Hansford R, Rahsepar AA, et al. Safety of Magnetic Resonance Imaging in Patients with Cardiac Devices. N Engl J Med. 2017;377(26):2555-2564. doi:10.1056/NEJMoa1604267
4. Weinreb JC, Rodby RA, Yee J, et al. Use of Intravenous Gadolinium-based Contrast Media in Patients with Kidney Disease: Consensus Statements from the American College of Radiology and the National Kidney Foundation. Radiology. 2021;298(1):28-35. doi:10.1148/radiol.2020202903
5. American College of Radiology. ACR Manual on MR Safety. January 1, 2024. Accessed September 12, 2025.
6. Pedrosa I, Altman DA, Dillman JR, et al. American College of Radiology Manual on MR Safety: 2024 Update and Revisions. Radiology. 2025;315(1):e241405. doi:10.1148/radiol.241405
Thoracic Ultrasound
Ultrasound is often used to facilitate procedures such as thoracentesis and central venous catheter insertion.
Ultrasound is also very useful for evaluating the presence and size of pleural effusions. It is commonly used at the bedside to guide thoracentesis, and studies suggest a higher yield and fewer complications when ultrasound is used for thoracentesis (1, 2). Point-of-care ultrasound is widely used to diagnose pneumothoraces. Evidence suggests that lung ultrasound is more sensitive and specific than plain chest radiographs for the diagnosis of pleural effusions, pneumonia, and pneumothorax, and can be helpful in diagnosis of pulmonary edema (3–8).
Endobronchial ultrasound (EBUS) is often used in conjunction with flexible fiberoptic bronchoscopy to help localize masses and enlarged lymph nodes. Diagnostic yield of transbronchial lymph node aspiration is higher using EBUS than conventional unguided techniques, particularly in the evaluation of cancer and sarcoidosis (9, 10, 11, 12).
Ultrasound references
1. Brogi E, Gargani L, Bignami E, et al. Thoracic ultrasound for pleural effusion in the intensive care unit: a narrative review from diagnosis to treatment. Crit Care. 2017;21(1):325. Published 2017 Dec 28. doi:10.1186/s13054-017-1897-5
2. Nicholson MJ, Manley C, Ahmad D. Thoracentesis for the Diagnosis and Management of Pleural Effusions: The Current State of a Centuries-Old Procedure. J Respir. 2023; 3(4):208-222. doi: 10.3390/jor3040020
3. Gartlehner G, Wagner G, Affengruber L, et al. Point-of-Care Ultrasonography in Patients With Acute Dyspnea: An Evidence Report for a Clinical Practice Guideline by the American College of Physicians. Ann Intern Med. 2021 174(7):967-976. doi: 10.7326/M20-5504.
4. Hansell L, Milross M, Delaney A, Tian DH, Ntoumenopoulos G. Lung ultrasound has greater accuracy than conventional respiratory assessment tools for the diagnosis of pleural effusion, lung consolidation and collapse: a systematic review. J Physiother. 2021;67(1):41-48. doi:10.1016/j.jphys.2020.12.002
5. Hendin A, Koenig S, Millington SJ. Better With Ultrasound: Thoracic Ultrasound. Chest. 2020;158(5):2082-2089. doi:10.1016/j.chest.2020.04.052
6. Mayo PH, Copetti R, Feller-Kopman D, et al. Thoracic ultrasonography: a narrative review. Intensive Care Med. 2019;45(9):1200-1211. doi:10.1007/s00134-019-05725-8
7. McLario DJ, Sivitz AB. Point-of-Care Ultrasound in Pediatric Clinical Care. JAMA Pediatr. 2015;169(6):594-600. doi:10.1001/jamapediatrics.2015.22
8. Ye X, Xiao H, Chen B, Zhang S. Accuracy of Lung Ultrasonography versus Chest Radiography for the Diagnosis of Adult Community-Acquired Pneumonia: Review of the Literature and Meta-Analysis. PLoS One 2015;10(6):e0130066. doi:10.1371/journal.pone.0130066
9. Adams K, Shah PL, Edmonds L, et al. Test performance of endobronchial ultrasound and transbronchial needle aspiration biopsy for mediastinal staging in patients with lung cancer: systematic review and meta-analysis. 2009. In: Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet]. York (UK): Centre for Reviews and Dissemination (UK); 1995-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK77899/
10. Bonifazi M, Tramacere I, Zuccatosta L, et al. Conventional versus Ultrasound-Guided Transbronchial Needle Aspiration for the Diagnosis of Hilar/Mediastinal Lymph Adenopathies: A Randomized Controlled Trial. Respiration. 2017;94(2):216-223. doi:10.1159/000475843
11. Herth F, Becker HD, Ernst A. Conventional vs endobronchial ultrasound-guided transbronchial needle aspiration: a randomized trial. Chest. 2004;125(1):322-325. doi:10.1378/chest.125.1.322
12. Tremblay A, Stather DR, MacEachern P, Khalil M, Field SK. A randomized controlled trial of standard vs endobronchial ultrasonography-guided transbronchial needle aspiration in patients with suspected sarcoidosis. Chest. 2009;136(2):340-346. doi:10.1378/chest.08-2768
Nuclear Lung Scanning
Nuclear scanning techniques used to image the chest include:
Ventilation/perfusion (V/Q) scanning
Positron emission tomography (PET)
V/Q scanning
V/Q scanning uses inhaled radionuclides to detect ventilation and IV radionuclides to detect perfusion. Areas of ventilation without perfusion, perfusion without ventilation, or matched increases and decreases in both can be detected with 6 to 8 views of the lungs.
V/Q scanning is most commonly used for diagnosing pulmonary embolism, but it has largely been replaced by CT angiography. However, V/Q scanning is still indicated in the diagnostic evaluation for chronic thromboembolic pulmonary hypertension (1).
Split-function ventilation scanning, in which the degree of ventilation is quantified for each lobe, is used to predict the effect of placement of endobronchial valves and the effect of lobar or lung resection on pulmonary function.
Positron emission tomography (PET) of the lungs
PET uses radioactively labeled glucose (fluorodeoxyglucose) to measure metabolic activity in tissues. It is used in pulmonary disorders to determine:
Whether lung nodules or mediastinal lymph nodes harbor tumor (metabolic staging)
Whether cancer is recurrent in previously irradiated, scarred areas of the lung
Although PET alone is superior to CT alone for mediastinal staging of newly diagnosed lung cancer, combined PET- CT is the recommended method, and is particularly useful in detecting both mediastinal and extrathoracic disease (2, 3, 4). Biopsy, typically with EBUS-guided needle aspiration, is generally indicated prior to surgical resection due to the possibility of false positives (eg, in inflammatory lesions, such as granulomas) with PET. Slowly growing tumors (eg, bronchoalveolar carcinoma, neuroendocrine tumors, some metastatic cancers) may cause false-negative results.
Nuclear lung scanning references
1. Teerapuncharoen K, Bag R. Chronic Thromboembolic Pulmonary Hypertension. Lung. 2022;200(3):283-299. doi:10.1007/s00408-022-00539-w
2. Gould MK, Kuschner WG, Rydzak CE, et al. Test performance of positron emission tomography and computed tomography for mediastinal staging in patients with non-small-cell lung cancer: a meta-analysis. Ann Intern Med 2003;139(11):879-892. doi:10.7326/0003-4819-139-11-200311180-00013
3. Expert Consensus Panel, Kidane B, Bott M, et al. The American Association for Thoracic Surgery (AATS) 2023 Expert Consensus Document: Staging and multidisciplinary management of patients with early-stage non-small cell lung cancer. J Thorac Cardiovasc Surg. 2023;166(3):637-654. doi:10.1016/j.jtcvs.2023.04.039
4. Spicer JD, Cascone T, Wynes MW, et al. Neoadjuvant and Adjuvant Treatments for Early Stage Resectable NSCLC: Consensus Recommendations From the International Association for the Study of Lung Cancer. J Thorac Oncol. 2024;19(10):1373-1414. doi:10.1016/j.jtho.2024.06.010
