Overview and Description
Radiography is performed by transmitting ionizing electromagnetic radiation through bony structures and soft tissue, producing an image based on the absorption of X-ray photons. It is the most commonly used diagnostic imaging study. Radiography refers to multiple modalities: mammography and dual energy X-ray absorptiometry (DEXA) are examples of low energy projectional radiography, fluoroscopy and angiography are special applications used for real time imaging, and computed tomography (CT) uses computed reconstruction to generate a cross sectional image. This article will focus on plain radiography, known colloquially as X-ray imaging.
Plain radiographs use a heterogeneous beam of X-rays projected toward a detector, creating an image based on the density and composition of the intervening objects. X-ray photons are the main source of ionizing electromagnetic radiation used in medical radiography. They are generated by bombarding an anode with high energy electrons emitted from a hot cathode. Detection methods include radiosensitive amplifying screens, image intensifiers, and digital detectors that reconstruct the image.1
Tissue density is reflected by the capacity to absorb X-rays. X-rays are unable to easily penetrate more dense tissue. The more dense a tissue is, the brighter and whiter it will appear on plain radiography.2 The following are listed in order of increasing radio-opacity:
- Air (trachea, lungs, intestine, paranasal sinuses).
- Soft tissues (heart, kidney, muscles).
- Calcium rich tissue (skeleton).
- Enamel of the teeth.
- Dense foreign bodies (metallic fillings), and radio-opaque contrast media (barium).
While there are few true contraindications, X-rays produce ionizing radiation as they deposit enough energy to eject an electron from an atom, potentially altering tissue at the molecular level. Ionizing radiation is carcinogenic, and cumulative exposure may increase the risk of cancer and therefore should be used judiciously in young children and pregnant women. Risk factors for tissue damage include radiation dose, younger age, female gender, and imaging radiosensitive regions.1
Radiation at high doses can be harmful to tissues and is typically measured in milli-Sieverts (mSv). An X-ray of the spine is equivalent to 1.5 mSv, or 6 months of natural background radiation, whereas an extremity X-ray is 0.001 mSV, or 3 hours of natural background radiation. For reference, people living in Colorado receive an extra 1.5 mSv per year than sea level, and a coast-to-coast flight exposes travelers to roughly 0.03 mSv. It would take roughly 38 chest X-rays to equal the amount of normal background radiation one receives over the course of a year.3
Relevance to Clinical Practice
Specific features of clinical application
X-ray imaging is a relatively low cost, widely available, and highly utilized modality for the evaluation of various pathological states. It can assist the physiatrist in the diagnosis and evaluation of numerous conditions. Consideration should be given to cost in those without health insurance.
In general, plain radiography is used in the context of a thorough clinical history and physical examination to confirm a diagnosis, establish severity or progression of a disease, evaluate anatomic alignment and enhance patient treatment.
Common applications include, but are not limited to:
- Diagnosis of fractures or joint dislocation
- Demonstration of proper alignment and stabilization of bony fragments following fracture treatment
- Guidance for interventional pain procedures, orthopedic surgery, such as spine repair, spine fusion, joint replacement, and fracture reduction
- Assessment for trauma, including skeletal injury or sequelae such as pneumothorax or aortic dissection
- Evaluation of osteomyelitis
- Diagnosis and evolution of pneumonia, atelectasis, pleural effusion, asthma, COPD, chronic bronchitis, bronchiolitis, and other pulmonary pathology.
- Evaluation of clinical cardiomegaly or heart failure
- Evaluation of arthritis, abnormal bone growth, and bony changes seen in metabolic conditions
- Evaluation of suspected bowel obstruction or perforation
- Diagnosis and evaluation of scoliosis
- Detection of bone cancer, a large number of patients diagnosed with asymptomatic myeloma may have radiographically occult myeloma deposits. At least 30% cancellous bone loss is required to visualize an intramedullary destructive process, such as myeloma, with radiographs and no extramedullary disease can be shown.4
- Evaluation of non-accidental injury, plagiocephaly, or craniosynostosis in children
- Evaluation of growth plates and skeletal maturity
- Location of foreign objects in soft tissues
- Diagnosis of retropharyngeal abscess
X-ray films are oftentimes ordered in more than one projection to optimize visualization of anatomic structures and determine alignment. Commonly utilized views are anteroposterior (AP) and lateral, however there are other views that may be obtained depending on the clinical circumstances.
Specific diagnostic criteria that justify the use of radiography
Plain radiography is best utilized in the context of a patient-specific clinical history and physical examination, in relation to the chief complaint. Clinical decision-making rules have been developed in some specific situations (e.g., Ottawa ankle and foot rules) to improve the diagnostic accuracy.2
- Quality, character, aggravating/alleviating factors
- Neurological concerns
- Associated symptoms
- Radiation of pain / pain referral pattern
Radiographic examinations are most effective when performed in conjunction with a standard physical examination of the affected region, consisting of
- Range of motion
- Auscultation (if indicated)
- Neurological examination
- Special tests
There are few contraindications to plain radiography, though caution should be taken in young children and pregnant women, and providers need to weigh the risks and benefits of imaging. Cumulative radiation dosage should be monitored in the case of frequent imaging.
The patient’s ability to tolerate the exam should always be considered prior to ordering.
Radiography can improve patient outcome by offering precise diagnostic and treatment localizations, often without significant delays or high costs seen with other imaging modalities.
One advantage of plain radiography is that it can be conducted in the inpatient or outpatient setting, with portable application for patients who cannot undergo standing exams.
Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills
While readily available, radiography should be used judiciously, as an extension of a thorough history and physical examination with an adequate pre-test probability.
Cutting Edge/ Emerging and Unique Concepts and Practice
Radiography is a historically well-established modality, and most of the innovation in radiologic studies surrounds magnetic resonance imaging (MRI), CT scan, PET, fluoroscopy and ultrasound. However, recent advances in plain radiography include the use of artificial-intelligence (AI) assisted interpretation, computer-aided diagnosis, digital mobile radiography, radiation dose reduction and tomosynthesis.
Due to the high-volume usage of plain radiography, particularly for chest x-rays and musculoskeletal ailments, AI assisted interpretation has emerged as a high interest area of study to increase efficiency and accuracy of reading.5 This approach has proven effective in detecting pneumothoraxes, pleural effusions, tuberculosis, lines and tubes, fractures, and osteoarthritis. AI was shown to increase sensitivity and positive predictive value of detecting COVID-19 changes on a chest X-ray.6 AI was even comparable to level of performance of third-year radiology residents in reading chest X-rays.7
Another topic of interest includes computer-aided detection and diagnosis. This entails the assistance of a computer in detecting abnormalities seen on imaging, most commonly used to detect breast or pulmonary nodules.8
There has also been an emerging usage of portable/mobile x-ray usage outside the hospital. Current common use settings include nursing homes, group homes, and homeless shelters.9 In theory, this method could increase efficiency and patient satisfaction without suffering a change in cost effectiveness or image quality.
As stated previously, the greatest hazard of repeated X-rays relates to radiation exposure. In a recent study, there was no difference in image quality of full spine images when comparing standard radiation doses to 50% standard dose.10
Some practitioners have been using breast tomosynthesis in lieu of mammography, where 10 X-rays are taken with 1/10th of the radiation dose per sequence, and the images are taken at different angles so the diagnostician can “scroll” through the tissue. This is thought to increase the sensitivity for detecting masses and further reduces radiation exposure compared to CT.11
More recently, tomosynthesis has been used in the detection of bone erosions in patients with established rheumatoid arthritis. One study found that tomosynthesis had a higher sensitivity in detecting bone erosions, increased by 14% when compared to plain radiography, with an almost equivalent radiation burden.12 Tomosynthesis has also been shown to be a great middle ground between plain film x-ray and CT in detecting fractures, assessing bone healing and evaluating hardware placement.13
Gaps in Knowledge/ Evidence Base
X-rays are limited in the evaluation of soft tissue. Often CT, MRI, or nuclear medicine studies are needed to confirm the diagnosis. In general, plain radiography is an extremely well-established modality, and continues to be the most commonly used diagnostic imaging modality in medical practice.
- Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2 |The National Academies Press. (n.d.). Retrieved August 23, 2022, from https://www.nap.edu/read/11340/chapter/1
- Magee, D. J., Manske, R. C., “Orthopedic physical assessment. Principles and concepts” (2021).
- ICRP, 2007. The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103. Ann. ICRP 37 (2-4).
- Mulligan, Michael. Multiple Myeloma Imaging. https://link.zixcentral.com/u/5a75939d/pu8VacJw7RGid2AMh3soMg?u=https%3A%2F%2Femedicine.medscape.com%2Farticle%2F391742-overview 2019.
- Adams SJ, Henderson RDE, Yi X, Babyn P. Artificial Intelligence Solutions for Analysis of X-ray Images. Can Assoc Radiol J. 2021 Feb;72(1):60-72. doi: 10.1177/0846537120941671. Epub 2020 Aug 6. PMID: 32757950.
- Rangarajan, K., Muku, S., Garg, A.K. et al. Artificial Intelligence–assisted chest X-ray assessment scheme for COVID-19. Eur Radiol 31, 6039–6048 (2021). https://doi.org/10.1007/s00330-020-07628-5
- Wu JT, Wong KCL, Gur Y, et al. Comparison of Chest Radiograph Interpretations by Artificial Intelligence Algorithm vs Radiology Residents. JAMA Netw Open. 2020;3(10):e2022779. doi:10.1001/jamanetworkopen.2020.22779
- Yanase, J., & Triantaphyllou, E. (2019). A systematic survey of computer-aided diagnosis in medicine: Past and present developments. Expert Systems with Applications. doi: 10.1016/j.eswa.2019.112821.
- Toppenberg, M.D., Christiansen, T.E.M., Rasmussen, F. et al. Mobile X-ray outside the hospital: a scoping review. BMC Health Serv Res 20, 767 (2020). https://doi.org/10.1186/s12913-020-05564-0
- Jeon MR, Park HJ, Lee SY, Kang KA, Kim EY, Hong HP, Youn I. Radiation dose reduction in plain radiography of the full-length lower extremity and full spine. Br J Radiol. 2017 Dec;90(1080):20170483. doi: 10.1259/bjr.20170483. Epub 2017 Oct 27. PMID: 28936890; PMCID: PMC6047650.
- ACR Statement on Breast Tomosynthesis. American College of Radiology | American College of Radiology. (2014, November 24). Retrieved August 23, 2022, from https://www.acr.org/About-Us/Media-Center/Position-Statements/Position-Statements-Folder/20141124-ACR-Statement-on-Breast-Tomosynthesis
- Simoni PA, Gerard LA, Kaiser MJ et al. Use of Tomosynthesis for Detection of Bone Erosions of the Foot in Patients With Established Rheumatoid Arthritis: Comparison With Radiography and CT. American Journal of Roentgenology. http://www.ajronline.org/doi/abs/10.2214/AJR.14.14120
- Blum A, Noël A, Regent D, Villani N, Gillet R, Gondim Teixeira P. Tomosynthesis in musculoskeletal pathology. Diagn Interv Imaging. 2018 Jul-Aug;99(7-8):423-441. doi: 10.1016/j.diii.2018.05.001. Epub 2018 May 30. PMID: 29859831.
Original Version of the Topic
Peter Torberntsson, MD, Dustin Anderson, MD. Plain Radiography, 8/4/2017
Lindsay Burke, MD
Nothing to Disclose
Crystal Graff, MD
Nothing to Disclose
Dustin Anderson, MD
Nothing to Disclose