Imaging - MRI Flashcards
MRI - General Hx
Non-ionizing imaging modality; used since the 1970s
Strong magnetic field causes hydrogen protons’ axes to all line up.
Uniform alignment creates magn vector oreinted along the axis of the Scanner
Radiofrequency waves then added to the magnetic field
results in a radio wave signal being emitted.
different tissues have different relaxation times and can be identified separately.
intensity of the signals are captured, amplified, then plotted on a grey scale and cross sectional images are built up
images are made up from a series of pulse sequences
MRI - Indication
Brain, spinal cord, intervertebral disk patho
musculoskeletal: cartilage, ligament, tendon, muscle assessment
soft tissue masses
ABD organs is CT is contraindicated
Many MRI studies do not require contrast administration.
IV for CNS tumor assessment and staging, pituitary disease, acoustic neuromas, CNS aneurysms, vascular malformations
MRI - Limitations
Size restrictions of Pt
Claustrophobia
Time and availability
Presence of Ferrus Metals,
Pacemaker
Cost
US - general
non-iodizing modality
1940s and formalized in 1991
high freq sound waves are bounced off structures.
Speed and intensity at which the waves return to the transducer are used to create a cross-sectional image of the tissues along the projected plane of the transducer
Interpretation relies on the recognition of the structure patterns and relationships:
fluids = black, high density (bone, fb) white, homogeneous density (organs) various shades of grey.
US- Terminology
Anechoic - fluid filled area void of any material
hypoechoic - a darker area compared to surrounding tissue
hyperechoic - a brighter area compared to surrounding tissue
fanning - tilting the probe while maintaining the same position on the skin
acoustic shadow - area on the screen void of US return due to an overlying obstructive structure
color flow doppler: assesses blood flow
US - indications
GB for stones and infection
pelvic for uterus, ovaries, fetus
Appendicitis - mostly for ped’s
cardiac - wall motion, valves, effusion
Vascular - flow and aneurysm
Neurological - Nerve blocks
POC - ocular, lung, Soft tissue (abcess, fb, tendon), vascular access, thoracoabd trauma
US - Adv/Disadv
Advantages:
No radiation, real-time motion images, procedural assistance
Disadvantages:
body habitus (body build/physique) restrictions
availability
interpretation more dependent on ability and competency and prob orientation.
Nuclear Medicine - General
Imaging utilizing radio-pharmaceuticals and assesses their uptake by different organs
Special camera or scanner is used to locate amount and timing of radioisotope []s
assessment of physiology not morphology
assesses for hyper v hypo vascularity or activity
Scans can assess static of dynamic processes
Nuclear Medicine - Indications
Lung V/Q to check for PE
Liver HIDA scan for gallbladder duct obstruction
Bone scan for CA, Fx, avascular necrosis, infections, Paget’s
Thyroid RAIU for hyper/hypo, nodules
Heart - myocardial perfusion scintigraphy (perfusion and function); Multigated acquisition scan (contractillity and EF measurement
PET for CA workup
Nuclear Medicine - Adv/Disadv
Adv:
Tx option for various types of CA
head to toe scanning if srs dz is suspected
assessment of organ function
less radiation than CT
Disadvantages
Very small exposure to ionizing radiation
potential for allergic Rxns
Availability
EKG
P is atrial depolarization; with subsequent delay at AV node s/p depol
QRS is ventricular depolarization and Atrial repol.
s-t ventricular depol. is complete
T is ventricular repol.
