Lecture 15 & 16 - Medical Imaging & Cartilage Flashcards
(32 cards)
Desc:
- Coronal view
- Sagittal
- Transverse
- Proximal & Distal
- Lateral & Medial
- Superior/Cephalic & Inferior
- Posterior/Dorsal
- Anterior/Ventral
- Caudal
- Coronal view: Put on crown, straight at it
- Sagittal: Side
- Transverse: cross-section
- Proximal & Distal: distal = further away
- Lateral & Medial= lateral further from midline
- Superior/Cephalic & Inferior= superior is head, inferior feet
- Posterior/Dorsal= back
- Anterior/Ventral= front
- Caudal= tail
How is an X-Ray image produced?
jus know concept
- X-ray tube: Photons accelerated toward metal target–> pass through patient, hit detector –> some rays absorbed by patient
- Amount of attenuation: density of tissue/energy of X-ray
Arrange air, soft tissue, metal, bone & fat in order of attenuation of X-ray (aka black –> white)
Air (darkest, no X-ray absorbed) –> fat –> soft tissue –> bone –> metal
How to interpret X-ray?
jus know
Airway: any obstruction? trachea central? Breathing: do lungs look the same? Circulation: heart normal size? Disability: fractures or metastasis Everything else
What are some clinical uses of X-Rays?
- Check for fractures of bone
- Follow up/Post procedure
Advantages and disadvantages of X-Ray
- Advantages: fast, portable, cheap, easy
- Disadvantages: radiation (relatively low), cannot see all pathology, poor soft tissue imaging
Desc mechanism of fluoroscopy. Clinical uses?
- Continuous x-rays to create real-time moving images
- Images enhanced using contrast (barium/iodine)
- Clinical uses: Angiography (check for embolism), barium swallow
Advantages & Disadvantages of Fluoroscopy?
- Advantages: Real time imaging, carry out intervention, quick
- Disadvantages: High radiation, one plane, radiation exposure to clinician, poor soft tissue imaging (muscle,skin,lung), cannot see all pathology
Desc. mechanism of CT (Computed Tomography)
- X-ray tube and detectors move around patient to create cross-sectional images
- Uses CT Number/Hounsfield Units (Water = 0)
- Less attenuating = negative HU (air, fat)
- More attenuating = (+) HU (bone, metal)
- 1 CT scan = background radiation of 1
Clinical uses of CT
- Diagnosis/further investigation & management: infection, cancer
- Directly guiding an intervention: radiotherapy
- Monitor conditions: cancer
- CT scan of head: check for oedema/tumours
[Hypodense (dark) = oedema/infection, Hyperdense (bright) = calcifications/haemorrhage]
Advantages & Disadvantages of CT Scan?
- Advantages: quick, good spatial resolution, can scan most parts
- Disadvantages: radiation, affected by artefact, requires breath holding, incidental findings, contrast reactions (patient allergic to contrast agents)
What is nuclear med? Mechanism
- Use of radiopharmaceutical (ingestion, inhalation) for imaging
- Tissue of interest emit gamma radiation which is detected by gamma camera. Has scintillator (convert signal to light)
What is the mechanism of PET (Positron Emission Tomography) ?
- Radionuclides emit positrons during decay
- E.g of radionuclides: fluorine-18
- Combined w CT/MRI
Clinical use of PET
- Oncology: detection/staging of cancer
- Early diagnosis of Alzheimer’s
- Detect inflammation
Advantages & Disadvantages of PET
- Advantages: good contrast & spatial resolution, analyse anatomy
- Disadvantages: radiation dose to patient, radioactive waste, expensive, time consuming
Desc. mechanism of MRI
only one that is green
- Patient placed in strong magnetic field –> magnet aligns spin of H atoms in body
- Some H atoms spin parallel to magnetic field and some antiparallel causing unmatched atoms
- Radiofrequency pulse applied
- Unmatched atoms absorb energy from Rf pulse and flip in opp. direction
- Rf turned off
- Unmatched ions go back to initial position and release energy –> detected by MRI sensor –> image
*Hypointense (dark), hyperintense (bright)
What is MRI ‘Weighting’?
- H atoms in diff tissues relax at diff speeds –> diff signals formed
- By adjusting time intervals btw Rf pulses –> max. contrast can be created
E.g T1 weighting: Fat bright, water dark
T2: Fat quite bright, water vv bright
Clinical uses of MRI
- Scan CNS (brain tumour)
- Gallstones
- Spine
- Bones and joints
- Used in pregnancy to avoid radiation
Advantages & Disadvantages of MRI?
- Advantages: X radiation, good contrast esp soft tissues
- Disadvantages: expensive, time consuming, remove all metal (pacemaker, cochlear implants), contrast reactions, overheating
Mechanism of ultrasound
- Utilise soundwaves –> travel thru and reflected back from tissues –> converts sound to electrical signal –> image
Clinical uses of ultrasound
- Check fetal growth
- Check for gallstones
- Check hollow structures (tubes) for obstruction
Advantages & Disadvantages of ultrasound?
- Advantages: X radiation, cheap, portable
- Disadvantages: no bone/gas penetration, difficult w obese/frail patients
Desc. 3 types of cartilages and similarities
Similarities: all matrix contain proteoglycan and hyaluronic acid & chondrocytes
- Hyaline cartilage: Contain type II collagen. Proteoglycan.
- Elastic cartilage: Many elastic fibre and type II collagen (flexible but tough)
- Fibrous: Type I (mainly), type II collagen
What cell type in hyaline cartilage? Function and structure?
- Chondrocyte ONLY: (present in isogenous groups) produce extracellular matrix
[hyaluronic acid ⬆️resilience = absorb H2O] - Precursor for bones that develop by endochondral ossification
- Avascular: loose matrix allows for diffusion of materials
(uniform appearance (neat), chondrocytes in lacunae)