Intro to Medical Imagining Flashcards
What is Radiology ?
Branch of medicine concerned with the use of radiant energy or radioactive material in diagnosis and treatment of disease.
What is the difference between a radiology and a radiographer ?
Radiologist:
-Specially trained Dr to interpret diagnostic images and perform ultrasonography
Radiographer: Healthcare professional trained to take X-ray, MRI or CT Scan (if also ultrasound then sonographer)
What is an interventional radiologist ? What are examples of procedures do they undertake ?
Radiologist who specialises in utilising minimally invasive image guided procedures to diagnose and treat diseases. Such procedures include angioplasty, stenting, biopsies (often use needles, catheters or wires).
What is a radiation oncologist ?
Specialist physician using ionising radiation in treatment of cancer.
What are the different kinds of medical imaging ?
- Conventional X-ray
- Computerized Tomography
- Nuclear Medicine
- Magnetic Resonance Imaging
- Ultrasound imaginig
How do x-rays work ?
By focusing beam of high energy electron in x-ray tube onto tungsten target.
What is the name of the image produced by X-Ray ?
Radiograph
How do tissues of high density appear on X-rays ? Why ?
They appear light grey/white because they cause more x-ray beam attenuation.
What are the 5 principle densities on a plain radiograph ?
Black: Air (lungs, bowel)
Dark grey: Fat (subcutaneous tissue layer)
Light grey: Soft Tissues/water (solid organs…)
Off White: Bone
White: Metal/contrast material
How many planes does X ray uses ?
It it best done using 2 planes including joint below and above the area of concerned (usually anteroposterior and lateral radiography in trauma)
What is the difference between lateral, PA and AP radiography ?
Lateral:
-X-ray passes through thorax from side to reach x-ray film adjacent to person’s other side
PA:
- X-rays pass through thorax from back to reach x-ray film anterior to person
- usually performed
AP:
- projection from front
- performed if patient is unwell (and is lying down)
What is a problem with switching from AP to PA or vice versa ?
There is no size standardisation for the heart which may be problematic (apparent heart size is different).
What are some specific kinds of X-ray imaging techniques ?
Mammography
Fluoroscopy
Angiography
What is mammography ?
- Kind of X-ray imaging
- Uses low dose X-ray system designed for detailed images of breasts to detect early breast cancer (no sign of breast disease or diagnose breast disease (with signs of breast disease)
What is fluoroscopy ?
- Kind of X-ray imaging
- X-ray beam passes through body image transmitted to monitor so continuous movement of body part/instrument/agent seen in detail on fluorescent -screen.
- Used when real time examination of patient is necessary
- Uses include positioning of orthopaedic implants in surgery, pacemakers, viewing movement of contrast agents (Barium) etc.
What is an angiography ?
- Kind of X-ray imaging
- Used in examinations of arteries, veins and organs to diagnose blockages
- Uses catheter inserted in vein from groin or arm usually, and contrast agent added to make blood vessels visible.
What do CAT and CT stand for ?
Computerised Axial Tomography and Computed Tomography
What is tomography ?
- Method used to produce images of single tissue plane.
- Tomographic images are produced by motion of x-ray tube and film or by motion of patient to blur image except in a single plane.
What is CT/CAT ?
Radiological imagining using computer processing to generate image of tissue density (in slice as thin as 1 mm).
What is the main difference between X-ray and CT?
CT is cross-sectional (but still a variable of X-ray)
What are the pros of CT Scan ?
- Fast
- Readily Available
- Good imaging of bones, abdomen, and lungs.
What are the cons of CT Scan ?
- High radiation dose (may not want to do it to a child)
- Not good imagining of soft tissues (brain and spinal chord)
What are examples of Nuclear Medicine/Scintigraphy ?
Pet Scan, bone scan, thyroid scan, renal scan (e.g. showing scarring).
What is Nuclear Medicine/Scintigraphy and how does it work ?
The use of gamma radiation to form images following injections of radiopharmaceuticals (such as technetium 99mTc).
Gamma rays emitted from metastable radionuclides detected by gamma camera which converts absorbed energy of radiation to electrical signal. Signal then analysed and displayed by computer.
What is SPECT ?
Single photon emission CT is a scintigraphy technique where computer programmed to analyse data from single depth within patient.
Allows increased sensitivity in detection of subtle lesions overlain by other active structures.
May be fused with CT to provide enhanced sensitivity.
What is PET ?
- Positron Emission Tomography- combo of CT and scintillation scanning, mostly used in oncology.
- Utilises radionuclides (biological compound attached to isotope) which decay by positron emission
What are the Pros of Nuclear Medicine/Scintigraphy ?
- Good function information
- Good anatomical information
- Good localisation of pathology
- High sensitivity
What are the Cons of Nuclear Medicine/Scintigraphy ?
- High dose of radiation
- Not good at differentiating between different pathologies
What is Magnetic Resonance Imaging ?
The use of powerful magnetic field and radiofrequency pulses to produce detailed images of body’s internal structural as cross-sectional images.
Does MRI emit any ionising radiation ?
NO
How does MRI work ?
Superconducting magnet creates static magnetic field
Small gradient magnet allow field to be precisely altered (used to focus magnetic field on part of body to be scanned)
Radio signals turned on and off and energy absorbed by different atoms reflected back out of body (protons in body initially line up with applied field, then tipped over by radio wave, then when turned off reallign with magnetic field, releasing energy)
Coil measures radiowaves and computer calculates absorption of reflection to compile cross-sectional images
What are pros of MRI ?
- Gold standard of imaging
- No radiation
- Good localisation pathology
- Good differentiation between pathologies
- Excellent soft tissue imaging (brain, spinal chord)
What are the cons of MRI?
- Potentially dangerous strong magnet
- Not good for showing bones
- Cost
- Long duration of scanning
- Need for anaesthesia in younger children/uncooperative patients
What are the pros of ultrasound imaging ?
- Safe
- No ionising radiation
- Equipment required is portable, compact and relatively inexpensive
What are the cons of ultrasound imaging?
- Highly operator dependant (harder to interpret if performed by someone else than in other imaging techniques)
- Structures surrounded by bone do not give clinically useful images (like brain, spinal chord)
- Attenuation of ultrasound signal at air/tissue boundaries means technique not suitable for imaging structures in lung or abdominal organs obscured by gas in overlying bowel
What is ALARA ?
As low as reasonably achievable (to limit patient irradiation)
