Lecture 15 & 16 - Medical Imaging & Cartilage Flashcards
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)
Where is hyaline cartilage found?
- Cartilage of nose
- Intervertebral discs
- Larynx, trachea
- Pubic symphysis
Desc. growth of hyaline cartilage
- Perichondrium (dense connective tissue)–> chondroblasts –> chondrocytes
- Growth from periphery = appositional growth
- Growth from centre = interstitial growth
(Regions: Dense connective tissue –> perichondral –> maturing chondral –> mature chondral]
What happens to hyaline cartilage in RA?
- Cartilage damaged –> X repair –> fibroblasts lay down scar tissue
- Calcifies w age (lose flexibility)
[macrophage remove old cartilage]
What cell type in elastic cartilage? Function and location?
- Chondrocyte ONLY
- Contains elastic fibres
- Found in pinna of ear, eustachian tube, epiglottis
(stains darker, has jagged lines, messy looking)
What cell type in fibrous cartilage? Function and location?
- Chondrocytes and Fibroblasts (dense regular connective tissue)
- Parallel fibres, no perichondrium
- Act as a shock absorber, resists shearing forces
- Found in: cartilage of intervertebral discs, pubic symphysis
(elongated nuclei, nice neat rows of fibres)
Desc. dev. of femur
- Calcified cartilage extends from epiphyseal growth plates and become mineralised
1. Zone of reserve cartilage (no cellular proliferation)
2. Zone of proliferation (actively dividing, cells enlarge and secrete matrix)
3. Zone of hypertrophy
4. Zone of calcified cartilage (enlarged cells degenerate and matrix calcifies)
5. Zone of resorption (dying chondrocytes leave calcified cartilage –> bone laid)
How does joint paint occur in osteoarthritis?
yellow slide, not in ILO
- Degeneration of hyaline and fibrous cartilage
- Narrowing of joint space
- Growth of osteophytes (bony spurs) –> inflammation
Why don’t chondrocytes regenerate in adult?
- Replaced w scar tissue
- Avascular nature
