Flashcards in Introduction to Radiology Deck (46):
What is radiology?
Use of medical imaging to diagnose and treat diseases within the body.
What are the types of medical imagine that is used most commonly in radiology?
X-ray (Mammography and fluoroscopy included)
Nuclear medicine (PET/SPECT)
What kind of radiation are X-rays?
Electromagnetic generated by firing electrons at a metal anode within vacuum tube
How can an image be generated by X-ray?
X-ray is either passed through the body (very high energy)
Can be absorbed by the body
Can be scattered in tissue
These interactions generate x-ray image
What do less dense objects look like on x-ray?
They are black (Air or gas)
What do more dense objects look like on x-ray?
They appear white for example: bone or metal
What would X-ray imaging show in bones?
Pathological processes such as cancer
What would x-ray imaging show in soft tissue?
Infection (common first request)
Blockages (Bowel obstruction, constipation, etc)
Trauma (Pneumothorax, pneumoperitoneum)
Pathological changes (CCF, cancer)
How is a mammography different to typical X-ray?
Specialized x-ray equipment for breast tissue
Uses low intensity X-rays (25 - 30kV)
Requires compression of the breast to reduce overlap of structures and to reduce X-ray dose
What is fluoroscopy?
Live x-ray imaging used for theatre imaging and functional studies/assessments (Dysphagia)
Oftem employs the use of contrast
What is x-ray contrast?
Use of high attentuating solution intravenously or orally to observe structures filled with that liquid
What fluid is used for IV contrast?
Iodine based solutions
What fluid is used for oral contrast?
Barium based solutions
What is important to note regarding use of IV contrast?
Can cause serious allergic reactions and extravasation.
It can be toxic to the kidneys when processed by them.
What are the advantages and disadvantages of using X-ray?
Excellent for bony pathology
Radiation dose (can be problematic in pregnant women and children)
2D, overlapping structures
Relatively poor soft tissue visualization
How does CT help solve the issues associated with using X-ray?
It takes x-ray images around the patient creating a 3D image allowing visualization of neighbouring structures and to create 3D models.
How are images of a CT scan shown?
Transverse view (Looking up from patient's feet)
Coronal (From the front)
Sagittal (From the left side)
What are the uses of CT scans?
Soft tissue (Volumetric scans for cancer detection, first line imagine for stroke)
Bones (Occult fractures and degenerative diseases)
Angiography with contrast imagine COW to see blockages in cerebral vessels.
What does a non-enhanced CT scan allow us to see?
Stones in the kidney, ureter and CBD
Calcifications in the liver and pancreas
Fat in liver tumours
Fat in adrenal adenoma or myelolipoma
What does contrast dye allow us to see on CT scan?
15 - 20 seconds: Demarcation of vessels and allows detection of aortic dissection as well as arterial bleeding
35 - 40 seconds (late arterial phase): hypervascular lesions, stomach, bowel, pancreas parenchyma, spleen, kidney outer cortex, liver Hepatic Cell Carcinoma, FNH, adenoma, bowel ischaemia, pancreatic cancers
What is the phase after 35 - 40 seconds of injecting dye for CT scan called?
Late arterial phase
What is the phase 15 - 20 seconds after dye injection called?
Early arterial phase
What is the phase called after 70 - 80 seconds of dye injection?
What does the hepatic phase indicate?
enhances hepatic parenchyma
Hypovascular liver lesions: cysts, abscesses, and most metastases
What is the phase called after 100 seconds of injecting dye?
What is enhanced after 100 seconds of dye?
Renal parenchyma including medulla
Renal cell carcinomas can be detected at this stage
What is the phase called after 6 minutes of dye injection?
What shows in the delayed phase on CT?
Enhancement of kidneys and urinary collecting system
Kidney transitional cell carcinoma
What are the advantages and disadvantages of using CT scans?
3D modelling, windowing and reformatting of images
Analysis of impact on neighbouring structures
Fast, available, relatively cheap
Patient compliance is important (staying still)
How does MRI work?
Uses powerful magnet to align magnetic moments of protons in tissue then flips them with RF pulse and image is formed by measuring energy emitted as protons return to alignment.
What is MRI used for?
1st line imaging choice for brain and spinal cord problems
Musculoskeletal imaging (cartilage, tendon, and ligament tears)
What is used for emergency situations when looking for bony abnormalities?
CT scans because they are faster and superior for bone. If not possible MRI can be used.
What are the cons for using MRIs?
Long scan times
Metal extremely prone to force generated by magnet. (prostheses, metallic foreign bodies, conductors, etc)
Not available 24 hours
Not available everywhere
Longer scan times/patient compliance issues
What are the advantages and to using MRI?
High quality images of soft tissue structures such as ligaments and cartilage
No radiation dose
How does ultrasound work?
Uses sound wave pulses to generate images.
Waves echo off interfaces between structures and return to detector to generate images
Images describe echogenicity
What are ultrasounds used for?
All soft tissue imaging (muscles, tendons, ligaments)
Blood flow analysis (doppler imaging)
Abdominal organ pathology
What are the pros and cons of using ultrasounds?
Good for soft tissue and measuring blood flow
Can't image well through air
Difficult to interpret without extensive training
What is nuclear medicine (PET/SPECT)?
Use of radioactive substances to generate images
What are the most common radioisotopes used for PET scans?
PET = FDG
PLANAR/SPECT = Technitium 99m (gamma emitter)
How are nuclear imaging techniques used?
Combined with CT/MRI to provide high resolution images.
What is NM used for?
Staging and identifying cancer
When are PET and SPECT used?
PET is very expensive so used when better contrast and spatial resolution is required
PET uses positron emitting isotope
SPECT is cheaper and uses gamma emitting isotope.
What is interventional radiology?
Use of imaging to direct minimally invasive procedures
What types of procedures use interventional radiology?
Vascular procedures - Stenting, Angioplasty, aneurysm coiling, embolization
Joint/nerve injections - Facet joints, nerve roots, steroid joint injections.
Biopsies, fine needle aspirates
Does high detail imaging necessarily mean improved outcomes?
No, indidental findings can trigger unnecessary anxiety