Chest radiograph: Difference between revisions

|Caption = A normal posteroanterior (PA) chest radiograph. of someone without any signs of injury. [[Anatomical terms of location#Medial and lateral|Dx and Sin stand for "right" and "left"]] respectively.

A '''chest radiograph''', colloquially called a '''chest X-ray''' ('''CXR'''), or ''' chest film''', is a [[Projectional radiography|projection radiograph]] of the [[chest]] used to diagnose conditions affecting the chest, its contents, and nearby structures. Chest radiographs are the most common film taken in medicine.

Like all methods of [[radiography]], chest radiography employs [[ionizing radiation]] in the form of [[X-ray]]s to generate images of the chest. The mean [[radiation]] dose to an adult from a chest radiograph is around 0.02 [[Sievert|mSv]] (2 [[Roentgen equivalent man|mrem]]) for a front view (PA, or posteroanterior) and 0.08 mSv (8 mrem) for a side view (LL, or latero-lateral).<ref>Fred A. Mettler, Walter Huda, Terry T. Yoshizumi, Mahadevappa Mahesh: "Effective Doses in Radiology and Diagnostic Nuclear Medicine: A Catalog" – Radiology 2008;248:254–263</ref> Together, this corresponds to a [[background radiation equivalent time]] of about 10 days.<ref name=radiologyinfo>{{cite web|title=Radiation Dose in X-Ray and CT Exams|url=https://www.radiologyinfo.org/en/info.cfm?pg=safety-xray|website=radiologyinfo.org by the [[Radiological Society of North America]]|accessdateaccess-date=2017-08-10}}</ref>

Chest radiographs are used to diagnose many conditions involving the chest wall, including its bones, and also structures contained within the [[thoracic cavity]] including the [[lung]]s, [[heart]], and [[great vessel]]s. [[Pneumonia]] and [[congestive heart failure]] are very commonly diagnosed by chest radiograph. Chest radiographs are also used [[Screening (medicine)|to screen]] for job-related lung disease in industries such as mining where workers are exposed to dust.<ref>[https://www.cdc.gov/niosh/blog/nsb060209_chest-radiography.html Using Digital Chest Images to Monitor the Health of Coal Miners and Other Workers] {{Webarchive|url=https://web.archive.org/web/20190128083122/https://www.cdc.gov/niosh/blog/nsb060209_chest-radiography.html |date=2019-01-28 }}. National Institute for Occupational Safety and Health.</ref>

Required projections can vary by country and hospital, although an erect posteroanterior (PA) projection is typically the first preference. If this is not possible, then an anteroposterior view will be taken. Further imaging depends on local protocols which is dependent on the hospital protocols, the availability of other imaging modalities and the preference of the image interpreter. In the UK, the standard chest radiography protocol is to take an erect posteroanterior view only, and a lateral one only on request by a radiologist.<ref>{{cite web|title=Chest X-ray quality – Projection|url=http://radiologymasterclass.co.uk/tutorials/chest/chest_quality/chest_xray_quality_projection.html#top_forth_img|website=Radiology Masterclass|accessdateaccess-date=27 January 2016}}</ref> In the US, chest radiography includes a PA and Lateral with the patient standing or sitting up. Special projections include an AP in cases where the image needs to be obtained [[List_of_abbreviations_used_in_medical_prescriptions#stat|stat]] (immediately) and with a portable device, particularly when a patient cannot be safely positioned upright. Lateral decubitus may be used for visualization of air-fluid levels if an upright image cannot be obtained. Anteroposterior (AP) Axial Lordotic projects the clavicles above the lung fields, allowing better visualization of the apices (which is extremely useful when looking for evidence of primary [[tuberculosis]]).

*[[Decubitus]] – taken while the patient is lying down, typically on his or hertheir side. Useful for differentiating [[pleural effusion]]s from consolidation (e.g. pneumonia) and loculated effusions from free fluid in the [[pleural cavity|pleural space]]. In effusions, the fluid ''layers out'' (by comparison to an up-right view, when it often accumulates in the [[costophrenic angle]]s).

*[[Lordotic]] view – used to visualize the [[apex of the lung]], to pick up abnormalities such as a [[Pancoast tumourtumor]].

*[[Oblique projection|Oblique]] view – useful for the visualization of the ribs and sternum. Although it's is necessary to do the appropriate adaptations to the x-ray dosage to be used.

Localization of lesions or inflammatory and infectious processes can be difficult to discern on chest radiograph, but can be inferencedinferred by [[silhouette sign|silhouetting]] and the [[hilum overlay sign]] with adjacent structures. If either [[hemidiaphragm]] is blurred, for example, this suggests the lesion to be from the corresponding lower lobe. If the right heart border is blurred, than the pathology is likely in the right middle lobe, though a [[pectus excavatum|cavum]] deformity can also blur the right heard border due to indentation of the adjacent sternum. If the left heart border is blurred, this implies a process at the [[lingula (lung)|lingula]].<ref>{{cite book|last1=Gandhi|first1=Sanjay|title=Chest Radiology: Exam Revision Made Easy|date=December 7, 2013|publisher=JMD Books|pages=541 pages|edition=1st|accessdate=}}</ref>

A pulmonary[[lung nodule]] is a discrete opacity in the lung which may be caused by:

* Infection: roundish[[round pneumonia]]

** Doubling time of six to 18 months: benign tumourtumor/malignant granuloma

Fluid in space between the lung and the chest wall is termed a [[pleural effusion]]. There needs to be at least 75 mL of pleural fluid in order to blunt the [[costophrenic angle]] on the lateral chest radiograph, and 200 mL of pleural fluid in order to blunt the [[costophrenic angle]] on the posteroanterior chest radiograph. On a lateral decubitus, amounts as small as 50ml of fluid are possible. Pleural effusions typically have a [[Meniscus (anatomy)|meniscus]] visible on an erect chest radiograph, but loculated effusions (as occur with an [[empyema]]) may have a [[lens (geometry)|lenticular]] shape (the fluid making an [[obtuse angle]] with the chest wall).

**nodular (lots ofmany small dots)

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File:Projectional rendering of CT scan of thorax (thumbnail).gif|Projectionally rendered [[CT scan]], showing the transition of thoracic structures between the anteroposterior and lateral view.

* [http://www.empacs.org/ Database of chest radiology related to emergency medicine] {{Webarchive|url=https://web.archive.org/web/20080725014041/http://www.empacs.org/ |date=2008-07-25 }}