Imaging of the skeleton Flashcards
how does an X-ray work and why can they be harmful?
produces 2D static image
X-rays are a form electromagnetic radiation (ionising radiation= harmful as it can alter atoms + turn them into ions, including DNA)
N.B. AS ATOMIC NUMBER OF AN ATOM INCREASES THE AMOUNT OF X RAY IT ABSORBS ALSO INCREASES, MORE RAYS IT ABSORBS THE MORE VISIBLE IT IS ON THE X RAY
- Produced in an x-ray tube when a massive voltage passed through a (usually tungsten) filament causing it to get so incandescently hot it starts expelling electrons in a process called thermionic emission
- These electrons are repelled away from this filament and accelerate towards a target at the other end of the tube
- When they interact with the atoms at the other end of the tube 1% their excess energy from the collision is converted into x-rays which are directed towards the patient (99% is converted to heat)
N.B. X-ray is produced when a negatively charged electrode is heated by electricity and electrons are released, thereby producing energy. That energy is directed toward a metal plate, or anode, at high velocity and an X-ray is produced when the energy collides with the atoms in the metal plate
2D representation of 3D structures
Something that looks normal from one angle, may look abnormal from another
Static image
advantages + disadvantages of X-ray
Advantages of X-rays:
○ Diagnostic Clarity: Effective for imaging bones and detecting skeletal issues.
○ Non-Invasive and Quick: No surgery needed, fast process.
○ Widely Accessible: Available in most medical facilities.
○ Cost-Effective: Cheaper than other imaging methods like MRI or CT scans.
○ Treatment Planning: Helps in planning surgeries and treatments.
Disadvantages of X-rays:
○ Radiation Exposure: Small risk of cancer, especially with repeated use.
○ Limited Soft Tissue Imaging: Less effective for organs, muscles, or ligaments.
○ Risk During Pregnancy: Potentially harmful to developing fetuses.
○ Contrast Allergies: Possible allergic reactions to substances used in some X-rays.
Not Suitable for All Conditions: Inadequate for certain diagnoses needing detailed imaging.
what is contrast media?
X-ray contrast media are chemically inert drugs which are given intravascularly in very high amounts within a very short time period. Although they are regarded as relatively safe drugs, adverse reactions can occur.
Contrast materials help distinguish or “contrast” selected areas of the body from surrounding tissue. This helps physicians diagnose medical conditions by improving the visibility of specific organs, blood vessels, or tissues.
what is a CT scan + advantages/disadvantages
produces 3D static image
Computed tomography (CT)
Tomography = cross-section/slices
Image contrast provided by x-rays
Capture radiographs with rotating x-ray beam which can be reformatted to give 3D representation of structures
- uses computer so we can manipulate/contrast to see structures
Use of CT Scan
CT scans are used for a detailed examination of internal structures. They are particularly useful for visualizing complex bone fractures, tumors, blood clots, internal bleeding, and detecting various diseases in organs such as the lungs, liver, and heart.
Advantages
Highly Detailed Images: Provides more detailed images than regular X-rays, particularly of soft tissues and blood vessels.
Speed: Fast scanning time, making it suitable for emergencies.
Precise Detection and Diagnosis: Helps in accurately detecting and diagnosing various conditions, including cancer, cardiovascular diseases, infectious diseases, trauma, and musculoskeletal disorders.
Guides Procedures: Useful in guiding surgical, biopsy, and radiation therapy planning.
Disadvantages
Radiation Exposure: Involves higher radiation doses compared to standard X-rays, which increases the risk of cancer.
Contrast Reactions: Some CT scans require a contrast dye, which can cause allergic reactions in some patients.
Limited Use in Pregnant Women: Generally avoided in pregnancy, especially in the first trimester, due to the radiation risk to the fetus.
Cost: More expensive than conventional X-rays.
Not Suitable for Certain Patients: May not be recommended for patients with kidney problems, especially when contrast is used.
how does an MRI work; advantages + disadvantages
produces 3D static image
* * Radiofrequency pulse is applied 90 degrees to the main magnetic field causes 2 things:
* Hydrogen atoms align at 90 degrees to the strong magnetic field
* Hydrogen atoms “process” (spin) together at the same frequency - in phase
- Once the pulse switches off, those 2 things are reversed, which this gives us 2 signals
- Hydrogen atoms go back to being aligned with strong magnetic field – T1 signal
Hydrogen atoms go back to spinning randomly – T2 signal
- Hydrogen atoms go back to being aligned with strong magnetic field – T1 signal
MRIs employ powerful magnets which produce a strong magnetic field that forces protons in the body to align with that field. (magnet means not suitable for some e.g. metal implant fitted, such as a pacemaker or artificial joint)
SO different tissues have v specific + different T1+ T2 signals means MRI can distinguish virtually all tissue/bone
Enables MRI to image structures CT doesn’t image well -> nerve, joint structures
disavantages:
Noisy
Claustrophobic
Takes a long time
Much less readily available (expensive)
what is meant by the term ECHOGENICITY when refering to an ultrasound scan + what does echogenicity depend on?
Different shades of grey correspond to different strengths of echo = echogenicity
A structures echogenicity depends upon its stiffness
The proportion of x-rays reflected increases as the difference between the stiffness of the two adjacent tissues increases
fat and liver,
muscle and bone,
air to skin
what is an ultrasound; advantages/disadvantages
produces 2D dynamic image
Speed of sound in soft tissue is a constant
Probe emits a pulse of ultrasound (no ionising radiation)
Then “listens” for echo
Use time to return and speed of sound to determine depth
Note probe is mobile so we get a dynamic image
An ultrasound is a diagnostic imaging technique that uses high-frequency sound waves to create images of structures within the body. These sound waves are emitted from a transducer, which is a hand-held device, and they bounce off tissues, organs, and fluids in the body. The echoes are then captured and converted into images by a computer.
Uses of Ultrasound:
Checking a baby’s health in pregnancy.
Examining organs like the heart, liver, kidneys, and others.
Finding problems in muscles and joints.
Guiding doctors during certain medical procedures.
Advantages:
Safe: It doesn’t use radiation, unlike X-rays.
Non-invasive: No need for cuts or injections.
Painless: Comfortable for patients.
Real-time imaging: Shows movement and live function of internal organs.
Disadvantages:
Limited detail: It might not show all internal issues, especially in dense body parts.
Difficulty with obese patients: Harder to get clear images through thick tissue.
Operator dependent: The quality of the images can depend a lot on the skill of the person doing the ultrasound.
what is the difference between a static and dynamic image?
Static Images: These are still images that capture a single moment in time. They are like photographs. Static images are commonly used in X-rays, CT scans, and MRI scans. They provide a detailed view of the structures inside the body, such as bones, organs, and other tissues, but they don’t show movement or function.
Dynamic Images: These are moving images that show activity over time, like a video. Dynamic imaging is used in modalities like ultrasound and certain types of MRI and CT scans. This kind of imaging is particularly useful for observing the functioning of organs, blood flow, and other movements within the body.
what are the 3 different types of joint structure classifications
fibrous joint(Synarthroses): bone against bone. These joints are joined by dense connective tissue, mostly collagen. They are immovable or only allow minimal movement. Examples include the sutures in the skull and the syndesmosis joint between the tibia and fibula in the lower leg.
Cartilaginous Joints (Amphiarthroses): bone/cartillage/bone. In these joints, the bones are connected by cartilage. They allow more movement than fibrous joints but are less movable than synovial joints. Examples include the intervertebral discs in the spine and the pubic symphysis in the pelvis.
Synovial Joints (Diarthroses): bone with synovial fluid between bone. These are the most common and most movable type of joints. Synovial joints have a fluid-filled joint cavity and are surrounded by a joint capsule. The ends of the bones in these joints are covered with articular cartilage. Examples include the knee, hip, elbow, and shoulder joints. These joints allow for a wide range of movements, such as rotation, bending, and sliding.
can you identify the surgical vs anatomical neck of a humerus and other structures of body (look up an image to check this)
