Medical Imaging: Difference between revisions

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<div class="editorbox"> '''Original Editor '''- [[User:Rachael Lowe|Rachael Lowe]] '''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}}</div>
<div class="editorbox"> '''Original Editor '''- [[User:Rachael Lowe|Rachael Lowe]] '''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}}</div>
== Overview  ==
== Overview  ==
[[File:Structural MRI animation.ogv.jpg|right|frameless]]
[[File:Cardiac MRI flow.gif|alt=|thumb| Cardiac MRI flow ]]
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Medical imaging is often perceived to designate the set of techniques that noninvasively produce images of the internal aspect of the body. It is the techniques and processes used to create images of the human body for clinical purposes such as seeking to reveal, diagnose or examine injury, dysfunction or pathology. As a discipline and in its widest sense,it incorporates radiology, tomography, endoscopy, thermography, medical photography and microscopy (e.g. for human pathological investigations).<br>
Medical imaging refers to all diagnostic and therapeutic investigations/interventions conducted in a typical radiology department. It encompasses different imaging modalities and processes to obtain images of the human body for diagnostic, treatment and follow up purposes.  
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In the clinical context, medical imaging is generally equated to radiology and the medical practitioner responsible for interpreting (and sometimes acquiring) the images is a radiologist. The radiographer or radiologic technologist is usually responsible for acquiring medical images of diagnostic quality, although some radiological interventions are performed by radiologists.  
Imaging investigations have improved significantly over the years and play in important role in diagnostics. It also plays an important role in initiatives to improve public health through screening for certain conditions<ref name=":2">WHO [https://www.who.int/diagnostic_imaging/en/ Diagnostic Imaging] Available from: https://www.who.int/diagnostic_imaging/en/<nowiki/>(accessed 7.4.2021)</ref>. Imaging does however need to be utilised with caution and sound clinical reasoning in order to avoid the potential harms of medical imaging, such as radiation and iatrogenic pain.  
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== Types of Imaging ==
* [[X-Rays|'''X-rays''']] (including plain radiographs, [[DEXA Scan|DEXA]] scans and fluoroscopy): Allows upright and dynamic imaging; assesses bony structures and can help to detect pulmonary pathology, abnormal growths, factures, oedema and deformities.
* [[MRI Scans|'''Magnetic resonance imaging''']] (MRI): Advanced imaging of soft tissue structure
* [[Ultrasound Scans|'''Ultrasound''']] (US)
* [[CT Scans|'''Computed tomography''']] (CT): More accurate assessment of bony structures
* '''[[Nuclear Medicine|Nuclear medicine]]:''' is the practice of utilising microscopic amounts of radioactive substances to diagnose, monitor and treat disease.<ref>Radiopedia Nuclear medicine Available:https://radiopaedia.org/articles/nuclear-medicine (accessed 8.10.20220</ref>
* '''PET''' (positron emission tomography) scan: an imaging test that involves the intravenous injection of a positron-emitting radiopharmaceutical, waiting to allow for systemic distribution, and then scanning for detection and quantification of patterns of radiopharmaceutical accumulation in the body. Used to diagnose a variety of diseases (for example tumours, heart disease, brain disorders). Provides a picture of the body working.<ref>Radiopedia PET Available: https://radiopaedia.org/articles/positron-emission-tomography<nowiki/>(accessed 8.10.2022)</ref>
* '''SPECT''' (Single photon emission computed tomography) similar to PET,  is a nuclear medicine imaging techniques which provide metabolic and functional information unlike CT and MRI.<ref>Radiopedia SPECT vs PET Available:https://radiopaedia.org/articles/spect-vs-pet (accessed 8.10.2022)</ref>
=== Hybrid Imaging ===
[[File:PET-MRI.jpeg|thumb|300x300px|PET-MRI]]
Hybrid Imaging is the fusion of two (or more) imaging modalities to form a new technique<ref>Radiopedia [https://radiopaedia.org/articles/modality?lang=us Modalities] Available from:https://radiopaedia.org/articles/modality?lang=us (accessed 7.4.2021)</ref>. By combining the innate advantages of the fused imaging technologies synergistically, usually a new and more powerful modality comes into being. Existing hybrid imaging modalities include: PET-CT, SPECT-CT, MRI-PET, MRI-SPECT
The general benefits of hybrid imaging include: Increased diagnostic accuracy, precise monitoring of interventional procedure and reduced radiation exposure, e.g. dynamic US after obtaining CT map.
=== Photoacoustic Imaging (PA) ===
[[File:PA.png|thumb|Schematic illustration of PA imaging]]
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Imaging is a useful resource for musculoskeletal conditions and is an invaluable tool for physical therapists when used appropriately. Imaging such as MRI, X-ray, CT scans, and bone scans are prime examples of practical diagnostic imaging that facilitates accurate diagnosis, prognosis, intervention, and assessment of injuries and dysfunctions that physical therapists address on a daily basis. It is important to know when imaging is appropriate, as unnecessary imaging will squander financial resources and increase potential for premature surgery. In many cases, studies indicate diagnostic imaging is under-utilized such as x-rays identifying fractures or bone scans identifying osteoporosis<ref>Van Tulder MW, Tuut M, Pennick V, Bombardier C, Assendelft WJJ. Quality of primary care guidelines for acute low back pain. Spine. 2004;29(17):E357-62. Available at: [https://www.ncbi.nlm.nih.gov/pubmed/15534397 http://www.ncbi.nlm.nih.gov/pubmed/15534397].</ref>. There are also studies indicating over utilization of imaging, such as x-rays or MRI’s for acute and uncomplicated low back pain.<ref>Freeborn DK, Shye D, Muttooty JP, Eraker S, Romeo J. Primary Care Physicians ’ Use of Lumbar Spine. Journal of General Internal Medicine.3-9.</ref><ref>Carey TS, Garrett J, Back C, Project P. Patterns of Ordering Diagnostic Tests for Patients with Acute Low Back Pain. Medicine. 1996.</ref><ref>Anon. Isaacs_MRI_2004.</ref><br>
Also known as Optoacoustic Imaging, is an upcoming biomedical imaging modality availing the benefits of optical resolution and acoustic depth of penetration. Optoacoustic imaging has demonstrated promising potential in a wide range of preclinical and clinical applications.<ref name=":1">Amalina Binte Ebrahim Attia, Ghayathri Balasundaram, Mohesh Moothanchery, U.S. Dinish, Renzhe Bi, Vasilis Ntziachristos, Malini Olivo, A review of clinical photoacoustic imaging: Current and future trends,
{{#ev:youtube|https://www.youtube.com/watch?v=Dm9iaq8uMkI|width}}<ref>The Audiopedia What is MEDICAL IMAGING? What does MEDICAL IMAGING mean? MEDICAL IMAGING meaning & explanation Available from: https://www.youtube.com/watch?v=Dm9iaq8uMkI (last accessed 1.10.19)</ref>
Photoacoustics, Volume 16, 2019, 100144, ISSN 2213-5979, obtained from https://www.sciencedirect.com/science/article/pii/S2213597919300679 doi: 10.1016/j.pacs.2019.100144
</ref> Clinical applications of optoacoustic imaging include: Musculoskeletal Imaging; Gastrointestinal Imaging; Breast imaging; Dermatologic Imaging eg Skin cancer; Vascular Imaging; Carotid Vessel Imaging.<ref name=":1" />
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Studies have showed the potential use of optoacoustic imaging in the assessment, diagnosis and monitoring of treatment in patients with inflammatory arthritis<ref>Jo J, Tian C, Xu G, et al. Photoacoustic tomography for human musculoskeletal imaging and inflammatory arthritis detection. ''Photoacoustics''. 2018;12:82–89. Published 2018 Jul 27 obtained from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6306364/ doi:10.1016/j.pacs.2018.07.004
</ref> as well as limb and muscle ischemia.<ref>Chen L, Ma H, Liu H, et al. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5446508/ Quantitative photoacoustic imaging for early detection of muscle ischemia injury]. ''Am J Transl Res''. 2017;9(5):2255–2265. Published 2017 May 15 obtained from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5446508/</ref>
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== Necessity of Medical Imaging ==
[[File:CT spinal cord.jpg|alt=|thumb|CT spinal cord]]Medical imaging is crucial in a variety of medical setting and at all major levels of health care. In public health and preventive medicine as well as in both curative and palliative care, effective decisions depend on correct diagnoses. Though clinical reasoning may be sufficient prior to treatment of many conditions, the use of diagnostic imaging services is paramount in confirming, correctly assessing and documenting courses of many diseases as well as in assessing responses to treatment.
== Caution with Imaging ==
Imaging is a useful resource for many conditions and is an invaluable tool for clinicians/physiotherapists when used appropriately. It is important to know when imaging is appropriate, as unnecessary imaging will squander financial resources and increase the potential for premature surgery/ iatrogenic effects.


== Radiographic Imaging    ==
Early or unnecessary referral for imaging may be influenced by patient expectations and clinician concerns, or may be used as way to reassure patients. These factors need to be managed with good communication and evidence based guidelines.<ref name=":0" />
[[File:Pneumothorax_xray_marked.jpg|right|frameless|200x200px]]
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Radiography is the use of ionizing electromagnetic radiation such as X-rays to view objects.&nbsp;This imaging modality utilizes a wide beam of x rays for image acquisition and is the first imaging technique available in modern medicine. Various forms of radiographic images are in use in medical imaging.
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Also see: [[Diagnostic Imaging: Best Practice|Diagnostic Imaging Best Practice]]
'''X rays [[X-Rays|(Projectional Radiography]])''' The term x-ray refers to the radiation beam and x-ray particles, not to the film plate itself. X-ray films should be referred to as films, plain films, radiographs, or a plain film study when dialoguing within the medical community.<ref name=":0">Biederman, R. E., Wilmarth, M. A., & Editor, C. M. D. T. (n.d.). Diagnostic Imaging in Physical Therapy Avoiding the Pitfalls. Diagnostic Imaging.</ref>
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X rays are often used to determine the type and extent of a fracture as well as for detecting pathological changes in the lungs. With the use of radio-opaque contrast media, such as barium, they can also be used to visualize the structure of the stomach and intestines.
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Radiography uses X-rays to view non-uniformly composed material. In the medical field, radiography is used to diagnose or treat patients through the recording of images of the internal structure of the body. These images assess the presence or absence of disease, foreign objects, and structural damage or anomaly.
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Potential areas for film and/or processing errors:
* Heel effect – a source of visual error related to x-ray production, due to the fact that x-rays released by the machine are not uniform. There are two ends to an x-ray machine, a cathode end and anode end. The cathode end releases more photons than the anode end, which results in over-exposure of the film at the cathode end and under-exposure at the anode end. Due to this fact, technicians will position the patient on the table in a manner such that the thickest portion of the body region being studied is placed nearest the cathode end of the tube and the thinner end is placed near the anode end.
* Artefact – An error in the perception of the visual image of the radiograph, usually seen as an abnormal finding or foreign body. Artifacts occur when the cassettes that house the x-ray film plates get exposed to finger prints or small debris.
* Exposure – A measure of the amount of ionising radiation determined by 3 factors: time, x-ray energy, and the quantity of the x-ray photons. Exposure can be manipulated by the technician to highlight structures of interest. Over-penetration will tend to enhance bone visibility, while under-penetration will enhance soft tissue visibility.
* Movement – A blurring in the image as a result of movement by the patient the moment the x-ray exposure is made.
* Film processing – An error that occurs during the processing of the film can result in disturbances in the contrast, detail, or density of the image displayed.
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Radiodensity is a representation of the relative tissue density, based on the appearance of the tone of the tissue (white, gray, or black). The following structures may be found on a medical radiograph (in order of increasing radiodensity):<ref name=":0" />
* Air – black appearance, often seen in structures such as the lungs, bowels, trachea
* Fat – dark grey appearance, often seen in structures such as thicker adipose tissue
* Muscle, tendon, organ tissue – appears “neutral” or mid-grey
* Bone – cancellous bone appears as light grey, while cortical bone appears as white
* Contrast media - white appearance
* Metal – white appearance, often seen in structures such as jewellery, dental fillings, or orthopaedic hardware
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Caution to the radiograph viewer/interpreter – There is an inherent error that occurs when a 2-dimensional image is created to depict 3-dimensional structures that are often superimposed on one-another. Due to this fact, radiographic studies of specific body regions often include 3 or more views from different angles.
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Four principle sources of radiographic error:<ref name=":0" />
* Enlargement occurs because the x-ray beams exit the machine in an expanding conical pattern (similar to a flashlight beam). As a result, objects placed closer to the beam source appear larger than objects placed further away from the beam source.
* Elongation is produced by the increased beam angle at the periphery of the x-ray beam cone. As a result of the increased beam angle, objects in the periphery of the x-ray beam appear smeared or spread compared to objects in the centre of the beam.
* Foreshortening is the opposite effect of elongation. This occurs when the body region to be studied is placed at an angle to the primary x-ray beam, resulting in the appearance of decreased length.
* Superimposition occurs because anatomic structures are often stacked on one another, forcing the x-ray beam to penetrate multiple structures before arriving at the film plate. Superimposition can create the appearance of increased density of structures, or the appearance of novel structures altogether.
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=== Other uses of X rays for Imaging ===
=== Iatrogenic Effects ===
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Abnormal radiologic findings of the musculoskeletal system can be very common. Not all abnormalities are relevant to a patient's complaint and over-emphasising radiologic findings can have harmful effects.
'''Fluoroscopy:''' produces real-time images of internal structures of the body in a similar fashion to radiography, but employs a constant input of x-rays, at a lower dose rate to provide moving projection radiographs of lower quality. Contrast media, such as barium, iodine, and air are used to visualize internal organs as they work. Fluoroscopy is mainly performed to view movement (of tissue or a contrast agent), or to guide a medical intervention, such as angioplasty, pacemaker insertion, or joint repair/replacement.&nbsp; Fluoroscopy is also used in image-guided procedures when constant feedback during a procedure is required such as intra-operative and catheter guidance.
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Fluoroscopy can be used to examine the digestive system using a substance which is opaque to X-rays, (usually barium sulfate or gastrografin), which is introduced into the digestive system either by swallowing or as an enema. This is normally as part of a double contrast technique, using positive and negative contrast. Barium sulfate coats the walls of the digestive tract (positive contrast), which allows the shape of the digestive tract to be outlined as white or clear on an X-ray. Air may then be introduced (negative contrast), which looks black on the film. <br> <br>'''Angiography''' is the use of fluoroscopy to view the cardiovascular system. An iodine-based contrast is injected into the bloodstream and watched as it travels around. Since liquid blood and the vessels are not very dense, a contrast with high density (like the large iodine atoms) is used to view the vessels under X-ray. Angiography is used to find aneurysms, leaks, blockages (thromboses), new vessel growth, and placement of catheters and stents. Balloon angioplasty is often done with angiography.
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'''Dual Energy X-ray Absorptiometry''' (or DEXA, or bone densitometry) is used primarily for osteoporosis tests. It is not projection radiography, as the X-rays are emitted in 2 narrow beams that are scanned across the patient, 90 degrees from each other. Usually the hip (head of the femur), lower back (lumbar spine) or heel (calcaneum) are imaged, and the bone density (amount of calcium) is determined and given a number (a T-score). It is not used for bone imaging, as the image quality is not good enough to make an accurate diagnostic image for fractures, inflammation etc. It can also be used to measure total body fat, though this isn't common. The radiation dose received from DEXA scans is very low, much lower than projection radiography examinations.
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[[CT Scans|'''Computed Tomography (CT)''']] or CT scan (previously known as CAT scan, the "A" standing for "axial") uses a high amount of ionizing radiation (in the form of X-rays) in conjunction with a computer to create images of both soft and hard tissues.&nbsp; It is a helical tomography which traditionally produces a 2D image of the structures in a thin section of the body.&nbsp; These images look as though the patient was sliced like bread (thus, "tomography"-- "tomo" means "slice").&nbsp; It has a greater ionizing radiation dose burden than projection radiography; repeated scans must be limited to avoid health effects.&nbsp;&nbsp;&nbsp; Contrast agents are often used, depending on the tissues needing to be seen.<br>
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== Magnetic Resonance Imaging (MRI) ==
* '''Routine MRI''' reports produce worse functional outcomes compared to a 'clinical report' (which includes reassurance of incidental findings) in patients with low back pain.<ref>Rajasekaran S, Dilip Chand Raja S, Pushpa BT, Ananda KB, Ajoy Prasad S, Rishi MK. The catastrophization effects of an MRI report on the patient and surgeon and the benefits of ‘clinical reporting’: results from an RCT and blinded trials. European Spine Journal. 2021 Jul;30:2069-81.</ref>
[[File:Knee MRI 0025 07 pdfs t1 t2 59f.jpg|right|frameless|200x200px]]
* '''Early-MRI''' in acute low back pain results in longer length of disability, higher medical cost and worse outcomes regardless of radiculopathy (even after controlling for severity and demographics)<ref name=":0">Webster BS, Bauer AZ, Choi Y, Cifuentes M, Pransky GS. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4235393/ Iatrogenic consequences of early magnetic resonance imaging in acute, work-related, disabling low back pain.] Spine. 2013 Oct 15;38(22):1939-46.</ref>
see [[MRI Scans|Magnetic resonance imaging]] 


=== Ultrasound Imaging ===
It is therefore very important to carefully consider whether imaging is indicated, and to always view the results in the context of an in depth history and physical examination. This will help to discern whether findings correlate with the patient's complaint, or are in fact incidental and negligible.  
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[[Ultrasound Scans|Ultrasound]] uses high frequency broadband sound waves in the megahertz range that are reflected by tissue to varying degrees to produce (up to 3D) images. This is commonly associated with imaging the fetus in pregnant women. Uses of ultrasound are much broader, however. Other important uses include imaging the abdominal organs, heart, breast, muscles, tendons, arteries and veins. See also [[Ultrasound Scans]]
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While it may provide less anatomical detail than techniques such as CT or MRI, it has several advantages which make it ideal in numerous situations, in particular that it studies the function of moving structures in real-time, emits no ionizing radiation, and contains speckle that can be used in elastography. It is very safe to use and does not appear to cause any adverse effects, although information on this is not well documented. It is also relatively inexpensive and quick to perform. Ultrasound scanners can be taken to critically ill patients in intensive care units, avoiding the danger caused while moving the patient to the radiology department. The real time moving image obtained can be used to guide drainage and biopsy procedures. Doppler capabilities on modern scanners allow the blood flow in arteries and veins to be assessed.  
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==Bone Scan==
=== Radiation ===
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Even though most imaging techniques use low doses of radiation, large, repeated doses have a cumulative effect and can be harmful to human health (including cancer and tissue damage). '''"Image gently"''' and '''"Image wisely"''' are initiatives that promote practices that reduce radiation exposure by eliminating unnecessary procedures (see resource section).<ref>Ford B, Dore M, Moullet P. [https://www.aafp.org/pubs/afp/issues/2021/0101/p42.pdf Diagnostic imaging: appropriate and safe use.] American Family Physician. 2021 Jan 1;103(1):42-50.</ref>Modern techniques have also resulted in reductions in radiation exposure during imaging.
'''''Bone scan''''' is an imaging technique that uses a radioactive compound to identify areas of healing within the bone. Bone scans work by drawing blood from the patient and tagging it with a bone seeking radiopharmaceutical. This radioactive compound emits gamma radiation. The blood is then returned to the patient intravenously. As the body begins its metabolic activity at the site of the injury, the blood tagged by the radioactive compound is absorbed at the bone and the gamma radiation at the site of the injury can be detected with an external gamma camera. A bone scan can be beneficial in determining injury to the bone within the first 24-48 hours of injury or when the displacement is too small to be detected by an x-ray or CT scan.<ref name="Swain">Swain J, Bush K. Diagnostic Imaging for Physical Therapists. St. Louis: Saunders Elsevier; 2009</ref>
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'''Indications for Bone Scans:'''
Factors that should be considered include a patient's age and lifetime exposure to radiation, as well as whether the benefit of the diagnostic test outweighs the risk. CT-scans have higher radiation risk than x-rays, whereas no ionising radiation is produced during MRI or ultrasound scans.<ref name=":3">Mafraji, M.A. Risk of Radiation in Medical Imaging [Internet]. Merck Manuals. 2023 [updated 2023 November; cited 2024 March]. Available from: https://www.msdmanuals.com/home/special-subjects/common-imaging-tests/computed-tomography-ct  </ref>  
#Primary and metastatic bone neoplasms.
#Disease progression or response to therapy.
#Paget’s disease of bone.
#Stress and/or occult fractures.
#Trauma – accidental and non-accidental.
#Osteomyelitis.
#Musculoskeletal inflammation or infection.
#Bone viability (grafts, infarcts, osteonecrosis).
#Metabolic bone disease.
#Arthritides.
#Prosthetic joint loosening and infection.
#Pain of suspected musculoskeletal etiology.
#Myositis ossificans.
#Complex regional pain syndrome (CRPS 1). Reflex sympathetic dystrophy.
#Abnormal radiographic or laboratory findings.
#Distribution of osteoblastic activity prior to administration of therapeutic radio-pharmaceuticals for treating bone pain.<ref>College A. ACR PRACTICE GUIDELINE FOR THE PERFORMANCE OF ADULT AND PEDIATRIC SKELETAL SCINTIGRAPHY ( BONE SCAN ). North. 2007:1-5.</ref>


== Electron Microscopy  ==
Radiation risk is of particular concern in the following scenarios:<ref name=":3" />:
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The electron microscope is a microscope that can magnify very small details with high resolving power due to the use of electrons as the source of illumination, magnifying at levels up to 2,000,000 times.
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Electron microscopy is employed in anatomic pathology to identify organelles within the cells. Its usefulness has been greatly reduced by immunhistochemistry but it is still irreplaceable for the diagnosis of kidney disease, identification of immotile cilia syndrome and many other tasks.
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== Nuclear Medicine  ==
* During infancy and early childhood
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* During pregnancy (especially early)
Nuclear medicine on a whole encompasses both the diagnosis and treatment of disease using nuclear properties. In imaging, the energetic photons emitted from radioactive nuclei are used for enhancing and viewing various pathologies. 
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Gamma cameras are used in nuclear medicine to detect regions of biological activity that are often associated with diseases. A short lived isotope, such as 123I is administered to the patient. These isotopes are more readily absorbed by biologically active regions of the body, such as tumors or fracture points in bones.
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=== Positron Emission Tomography ===
=== Asymptomatic Findings ===
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<p align="justify">Although advanced imaging is generally very sensitive, it can be very non-specific. Various studies have found that imaging findings and symptoms often do not correlate. Consider the table below - these findings provide evidence that what we regard as pathology may not be that significant. Also see the pages on imaging of specific body regions for more detail:</p>
Positron emission tomography (PET) is primarily used to detect diseases of the brain and heart. Similarly to nuclear medicine, a short-lived isotope, such as 18F, is incorporated into a substance used by the body such as glucose which is absorbed by the tumor of interest. PET scans are often viewed alongside computed tomography scans, which can be performed on the same equipment without moving the patient. This allows the tumors detected by the PET scan to be viewed next to the rest of the patient's anatomy detected by the CT scan.
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=== Single Photon Emission Computed Tomography ===
* [[Diagnostic Imaging of the Foot and Ankle for Physical Therapists|Foot and Ankle]]
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* [[Diagnostic Imaging of the Knee for Physical Therapists|Knee]]
Another 3D tomographic technique is SPECT but uses gamma camera like method for reconstruction.
* [[Diagnostic Imaging of the Hip for Physical Therapists|Hip]]
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* [[Common Diagnostic Imaging of the Lumbar Spine|Lumbar spine]]
* [[Diagnostic Imaging of the Shoulder|Shoulder]]


== Optoacoustic Imaging ==
{| class="wikitable"
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|+Pathologies in asymptomatic subjects
Also known as Photoacoustic Imaging, is an upcoming biomedical imaging modality availing the benefits of optical resolution and acoustic depth of penetration. With its capacity to offer structural, functional, molecular and kinetic information making use of either endogenous contrast agents like hemoglobin, lipid, melanin and water or a variety of exogenous contrast agents or both, Optoacoustic imaging has demonstrated promising potential in a wide range of preclinical and clinical applications.<ref name=":1">Amalina Binte Ebrahim Attia, Ghayathri Balasundaram, Mohesh Moothanchery, U.S. Dinish, Renzhe Bi, Vasilis Ntziachristos, Malini Olivo, A review of clinical photoacoustic imaging: Current and future trends,
!'''Pathology'''
Photoacoustics, Volume 16, 2019, 100144, ISSN 2213-5979, https://doi.org/10.1016/j.pacs.2019.100144  obtained from https://www.sciencedirect.com/science/article/pii/S2213597919300679
!'''Prevalence among asymptomatic population'''
</ref>
|-
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|Lumbar disc herniation and/or spinal stenosis
|20- 75%
|-
|Cervical disc bulging
|75 - 90%<ref>Nakashima H, Yukawa Y, Suda K, Yamagata M, Ueta T, Kato F. Abnormal findings on magnetic resonance images of the cervical spines in 1211 asymptomatic subjects. Spine. 2015 Mar 15;40(6):392-8.</ref>
|-
|Cervical spinal cord compression
|7 - 35% <ref>Smith SS, Stewart ME, Davies BM, Kotter MR. The prevalence of asymptomatic and symptomatic spinal cord compression on magnetic resonance imaging: a systematic review and meta-analysis. Global spine journal. 2021 May;11(4):597-607.</ref>
|-
|Rotator cuff tendinopathy
|25 - 89% <ref name=":4">Girish G, Lobo LG, Jacobson JA, Morag Y, Miller B, Jamadar DA. Ultrasound of the shoulder: asymptomatic findings in men. American Journal of Roentgenology. 2011 Oct;197(4):W713-9.</ref>
|-
|Mild glenohumeral or acromioclavicular OA 12
|50 - 70%<ref name=":4" />
|-
|Hip labrum tear 13/14
|54% <ref>Heerey, J.J., Kemp, J.L., Mosler, A.B., Jones, D.M., Pizzari, T., Souza, R.B. and Crossley, K.M., 2018. What is the prevalence of imaging-defined intra-articular hip pathologies in people with and without pain? A systematic review and meta-analysis. ''British Journal of Sports Medicine'', ''52''(9), pp.581-593.</ref>
|-
|Knee Meniscal abnormalities and OA 19
|60% <ref>Englund M, Guermazi A, Gale D, Hunter DJ, Aliabadi P, Clancy M, Felson DT. Incidental meniscal findings on knee MRI in middle-aged and elderly persons. New England Journal of Medicine. 2008 Sep 11;359(11):1108-15.</ref>
|}


Clinical applications of optoacoustic imaging include:<ref name=":1" />
== Health Care Team ==
* Breast imaging
Imaging for medical purposes involves a team which includes the service of radiologists, radiographers (x-ray technologists), sonographers (ultrasound technologists), medical physicists, nurses, biomedical engineers, and other support staff working together. Appropriate use of medical imaging requires a multidisciplinary approach.<ref name=":2" />
* Dermatologic Imaging
** Pilosebaceous units
** Skin cancer
** Inflammatory skin diseases
* Vascular Imaging
** Cutaneous miscrovasculature
** Vascular Dysfunction
** Wound Imaging
* Carotid Vessel Imaging
* Musculoskeletal Imaging
* Gastrointestinal Imaging
* Adipose Tissue Imaging


<p align="justify">
== Conclusion ==
Recent studies showed the potential use of optoacoustic imaging in the assessment, diagnosis and monitoring of treatment in patients with inflammatory arthritis<ref>Jo J, Tian C, Xu G, et al. Photoacoustic tomography for human musculoskeletal imaging and inflammatory arthritis detection. ''Photoacoustics''. 2018;12:82–89. Published 2018 Jul 27. doi:10.1016/j.pacs.2018.07.004 obtained from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6306364/
Medical imaging is a crucial component of healthcare and provide a valuable tool for diagnosis, screening and treatment. It is however important to follow [[Diagnostic Imaging: Best Practice|best practice guidelines]] with a particular focus on avoiding unnecessary imaging and ensuring appropriate, evidence-based interpretation of results. '''We treat whole, complex persons - not images and scans.'''
</ref> as well limb and muscle ischemia.<ref>Chen L, Ma H, Liu H, et al. Quantitative photoacoustic imaging for early detection of muscle ischemia injury. ''Am J Transl Res''. 2017;9(5):2255–2265. Published 2017 May 15 obtained from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5446508/</ref>
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==Diagnostic Imaging for Body Regions==
==Diagnostic Imaging for Body Regions==

Latest revision as of 16:41, 21 March 2024

Original Editor - Rachael Lowe Top Contributors - Rachael Lowe, Lucinda hampton, Donald John Auson, Admin, Melissa Coetsee, Kim Jackson, Naomi O'Reilly, Adam Vallely Farrell and Karen Wilson

Overview[edit | edit source]

Cardiac MRI flow

Medical imaging refers to all diagnostic and therapeutic investigations/interventions conducted in a typical radiology department. It encompasses different imaging modalities and processes to obtain images of the human body for diagnostic, treatment and follow up purposes.

Imaging investigations have improved significantly over the years and play in important role in diagnostics. It also plays an important role in initiatives to improve public health through screening for certain conditions[1]. Imaging does however need to be utilised with caution and sound clinical reasoning in order to avoid the potential harms of medical imaging, such as radiation and iatrogenic pain.

Types of Imaging[edit | edit source]

  • X-rays (including plain radiographs, DEXA scans and fluoroscopy): Allows upright and dynamic imaging; assesses bony structures and can help to detect pulmonary pathology, abnormal growths, factures, oedema and deformities.
  • Magnetic resonance imaging (MRI): Advanced imaging of soft tissue structure
  • Ultrasound (US)
  • Computed tomography (CT): More accurate assessment of bony structures
  • Nuclear medicine: is the practice of utilising microscopic amounts of radioactive substances to diagnose, monitor and treat disease.[2]
  • PET (positron emission tomography) scan: an imaging test that involves the intravenous injection of a positron-emitting radiopharmaceutical, waiting to allow for systemic distribution, and then scanning for detection and quantification of patterns of radiopharmaceutical accumulation in the body. Used to diagnose a variety of diseases (for example tumours, heart disease, brain disorders). Provides a picture of the body working.[3]
  • SPECT (Single photon emission computed tomography) similar to PET, is a nuclear medicine imaging techniques which provide metabolic and functional information unlike CT and MRI.[4]

Hybrid Imaging[edit | edit source]

PET-MRI

Hybrid Imaging is the fusion of two (or more) imaging modalities to form a new technique[5]. By combining the innate advantages of the fused imaging technologies synergistically, usually a new and more powerful modality comes into being. Existing hybrid imaging modalities include: PET-CT, SPECT-CT, MRI-PET, MRI-SPECT

The general benefits of hybrid imaging include: Increased diagnostic accuracy, precise monitoring of interventional procedure and reduced radiation exposure, e.g. dynamic US after obtaining CT map.

Photoacoustic Imaging (PA)[edit | edit source]

Schematic illustration of PA imaging

Also known as Optoacoustic Imaging, is an upcoming biomedical imaging modality availing the benefits of optical resolution and acoustic depth of penetration. Optoacoustic imaging has demonstrated promising potential in a wide range of preclinical and clinical applications.[6] Clinical applications of optoacoustic imaging include: Musculoskeletal Imaging; Gastrointestinal Imaging; Breast imaging; Dermatologic Imaging eg Skin cancer; Vascular Imaging; Carotid Vessel Imaging.[6]

Studies have showed the potential use of optoacoustic imaging in the assessment, diagnosis and monitoring of treatment in patients with inflammatory arthritis[7] as well as limb and muscle ischemia.[8]

Necessity of Medical Imaging[edit | edit source]

CT spinal cord

Medical imaging is crucial in a variety of medical setting and at all major levels of health care. In public health and preventive medicine as well as in both curative and palliative care, effective decisions depend on correct diagnoses. Though clinical reasoning may be sufficient prior to treatment of many conditions, the use of diagnostic imaging services is paramount in confirming, correctly assessing and documenting courses of many diseases as well as in assessing responses to treatment.

Caution with Imaging[edit | edit source]

Imaging is a useful resource for many conditions and is an invaluable tool for clinicians/physiotherapists when used appropriately. It is important to know when imaging is appropriate, as unnecessary imaging will squander financial resources and increase the potential for premature surgery/ iatrogenic effects.

Early or unnecessary referral for imaging may be influenced by patient expectations and clinician concerns, or may be used as way to reassure patients. These factors need to be managed with good communication and evidence based guidelines.[9]

Also see: Diagnostic Imaging Best Practice

Iatrogenic Effects[edit | edit source]

Abnormal radiologic findings of the musculoskeletal system can be very common. Not all abnormalities are relevant to a patient's complaint and over-emphasising radiologic findings can have harmful effects.

  • Routine MRI reports produce worse functional outcomes compared to a 'clinical report' (which includes reassurance of incidental findings) in patients with low back pain.[10]
  • Early-MRI in acute low back pain results in longer length of disability, higher medical cost and worse outcomes regardless of radiculopathy (even after controlling for severity and demographics)[9]

It is therefore very important to carefully consider whether imaging is indicated, and to always view the results in the context of an in depth history and physical examination. This will help to discern whether findings correlate with the patient's complaint, or are in fact incidental and negligible.

Radiation[edit | edit source]

Even though most imaging techniques use low doses of radiation, large, repeated doses have a cumulative effect and can be harmful to human health (including cancer and tissue damage). "Image gently" and "Image wisely" are initiatives that promote practices that reduce radiation exposure by eliminating unnecessary procedures (see resource section).[11]Modern techniques have also resulted in reductions in radiation exposure during imaging.

Factors that should be considered include a patient's age and lifetime exposure to radiation, as well as whether the benefit of the diagnostic test outweighs the risk. CT-scans have higher radiation risk than x-rays, whereas no ionising radiation is produced during MRI or ultrasound scans.[12]

Radiation risk is of particular concern in the following scenarios:[12]:

  • During infancy and early childhood
  • During pregnancy (especially early)

Asymptomatic Findings[edit | edit source]

Although advanced imaging is generally very sensitive, it can be very non-specific. Various studies have found that imaging findings and symptoms often do not correlate. Consider the table below - these findings provide evidence that what we regard as pathology may not be that significant. Also see the pages on imaging of specific body regions for more detail:

Pathologies in asymptomatic subjects
Pathology Prevalence among asymptomatic population
Lumbar disc herniation and/or spinal stenosis 20- 75%
Cervical disc bulging 75 - 90%[13]
Cervical spinal cord compression 7 - 35% [14]
Rotator cuff tendinopathy 25 - 89% [15]
Mild glenohumeral or acromioclavicular OA 12 50 - 70%[15]
Hip labrum tear 13/14 54% [16]
Knee Meniscal abnormalities and OA 19 60% [17]

Health Care Team[edit | edit source]

Imaging for medical purposes involves a team which includes the service of radiologists, radiographers (x-ray technologists), sonographers (ultrasound technologists), medical physicists, nurses, biomedical engineers, and other support staff working together. Appropriate use of medical imaging requires a multidisciplinary approach.[1]

Conclusion[edit | edit source]

Medical imaging is a crucial component of healthcare and provide a valuable tool for diagnosis, screening and treatment. It is however important to follow best practice guidelines with a particular focus on avoiding unnecessary imaging and ensuring appropriate, evidence-based interpretation of results. We treat whole, complex persons - not images and scans.

Diagnostic Imaging for Body Regions[edit | edit source]

References[edit | edit source]

  1. ↑ 1.0 1.1 WHO Diagnostic Imaging Available from: https://www.who.int/diagnostic_imaging/en/(accessed 7.4.2021)
  2. ↑ Radiopedia Nuclear medicine Available:https://radiopaedia.org/articles/nuclear-medicine (accessed 8.10.20220
  3. ↑ Radiopedia PET Available: https://radiopaedia.org/articles/positron-emission-tomography(accessed 8.10.2022)
  4. ↑ Radiopedia SPECT vs PET Available:https://radiopaedia.org/articles/spect-vs-pet (accessed 8.10.2022)
  5. ↑ Radiopedia Modalities Available from:https://radiopaedia.org/articles/modality?lang=us (accessed 7.4.2021)
  6. ↑ 6.0 6.1 Amalina Binte Ebrahim Attia, Ghayathri Balasundaram, Mohesh Moothanchery, U.S. Dinish, Renzhe Bi, Vasilis Ntziachristos, Malini Olivo, A review of clinical photoacoustic imaging: Current and future trends, Photoacoustics, Volume 16, 2019, 100144, ISSN 2213-5979, obtained from https://www.sciencedirect.com/science/article/pii/S2213597919300679 doi: 10.1016/j.pacs.2019.100144
  7. ↑ Jo J, Tian C, Xu G, et al. Photoacoustic tomography for human musculoskeletal imaging and inflammatory arthritis detection. Photoacoustics. 2018;12:82–89. Published 2018 Jul 27 obtained from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6306364/ doi:10.1016/j.pacs.2018.07.004
  8. ↑ Chen L, Ma H, Liu H, et al. Quantitative photoacoustic imaging for early detection of muscle ischemia injury. Am J Transl Res. 2017;9(5):2255–2265. Published 2017 May 15 obtained from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5446508/
  9. ↑ 9.0 9.1 Webster BS, Bauer AZ, Choi Y, Cifuentes M, Pransky GS. Iatrogenic consequences of early magnetic resonance imaging in acute, work-related, disabling low back pain. Spine. 2013 Oct 15;38(22):1939-46.
  10. ↑ Rajasekaran S, Dilip Chand Raja S, Pushpa BT, Ananda KB, Ajoy Prasad S, Rishi MK. The catastrophization effects of an MRI report on the patient and surgeon and the benefits of ‘clinical reporting’: results from an RCT and blinded trials. European Spine Journal. 2021 Jul;30:2069-81.
  11. ↑ Ford B, Dore M, Moullet P. Diagnostic imaging: appropriate and safe use. American Family Physician. 2021 Jan 1;103(1):42-50.
  12. ↑ 12.0 12.1 Mafraji, M.A. Risk of Radiation in Medical Imaging [Internet]. Merck Manuals. 2023 [updated 2023 November; cited 2024 March]. Available from: https://www.msdmanuals.com/home/special-subjects/common-imaging-tests/computed-tomography-ct
  13. ↑ Nakashima H, Yukawa Y, Suda K, Yamagata M, Ueta T, Kato F. Abnormal findings on magnetic resonance images of the cervical spines in 1211 asymptomatic subjects. Spine. 2015 Mar 15;40(6):392-8.
  14. ↑ Smith SS, Stewart ME, Davies BM, Kotter MR. The prevalence of asymptomatic and symptomatic spinal cord compression on magnetic resonance imaging: a systematic review and meta-analysis. Global spine journal. 2021 May;11(4):597-607.
  15. ↑ 15.0 15.1 Girish G, Lobo LG, Jacobson JA, Morag Y, Miller B, Jamadar DA. Ultrasound of the shoulder: asymptomatic findings in men. American Journal of Roentgenology. 2011 Oct;197(4):W713-9.
  16. ↑ Heerey, J.J., Kemp, J.L., Mosler, A.B., Jones, D.M., Pizzari, T., Souza, R.B. and Crossley, K.M., 2018. What is the prevalence of imaging-defined intra-articular hip pathologies in people with and without pain? A systematic review and meta-analysis. British Journal of Sports Medicine, 52(9), pp.581-593.
  17. ↑ Englund M, Guermazi A, Gale D, Hunter DJ, Aliabadi P, Clancy M, Felson DT. Incidental meniscal findings on knee MRI in middle-aged and elderly persons. New England Journal of Medicine. 2008 Sep 11;359(11):1108-15.
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