Week 9 Flashcards
what is STIR used for
fat suppression
what is CSF used for
fluid suppression
applications of spin-echo are __
any part of body except fast moving organs
applications of inversion recovery are __
- CNS (FLAIR)
- MSK (STIR)
applications of gradient-echo are __
fast imaging
advantages of spin-echo are __
- good image quality
- gold standard for image contrast & weighting
advantages of inversion recovery are __
- good image quality
- sensitive to pathology
advantages of gradient-echo are __
- short scan time
- improved SNR by more NEX
- sensitive to susceptibility
disadvantages of spin-echo are __
- long scan times
- motion artifacts
disadvantages of inversion recovery are __
- very long scan time
- motion artifacts
disadvantages of gradient-echo are __
- B0 inhomogeneity & susceptibility
- blooming artifacts
challenges of MRI abdomen
- Respiratory motion
- Organ location
- Peristalsis
- Artery pulsing
- Patient’s cooperativeness
- Breath hold time (10 – 20 s)
MRI abdomen patient position
- Headfirst supine
- Fasting 6 – 8 hours to distend gallbladder
- Breath hold instructions
- Power injector if dynamic scan is neeeded using 20 IV cannula
different methods to test arrival of MR contrast agent
- test bolus timing
- fluoroscopic trigger
- time resolved imaging
what is the disadvantage of fluoroscopic trigger
operator dependent
MRI abdomen axial range is __
diaphragm till iliac crest
MRI abdomen axial range for 3D pre & post contrast are __
diaphragm till lower poles of kidney
MRI abdomen coronal range is __
diaphragm till iliac crest
MRI abdomen 3D VIBE + C + BH coronal range is __
anterior liver through posterior kidney
what are fast spin echoes
multiple echoes in 1 TR where middle of K-spaces filled up first before filling up peripheries
In HASTE, all data from all K-spaces are obtained after __
single 90 degrees excitation pulse
HASTE creates __
mirror image
How does HASTE work
Uses multiple 180° pulse echoes with shortened interecho spacing to acquire all imaging data during TR
phase cycling formula
phase cycling = 1 / frequency offset
False vs True pelvis
False pelvis (whole pelvis) vs true pelvis (prostate, uterus, ovaries)
increasing bandwidth will __ blurriness by ___
decrease; reducing echo spacing to allow more quickly acquired data but higher fat signal
high receiver bandwidth advantages are __
- less chemical shift, metal / distortion / susceptibility artifacts
- shorter minimum TE/TR & echo spacing
high receiver bandwidth disadvantages are __
lower SNR, large FOV, more noise
MRI pelvis patient position
- Supine headfirst / feet first
- Posterior spine coil + anterior body / torso
- Superior edge of coil above iliac crest
- Female pelvis = 20G cannula, prostate dynamic = 18G cannula
- Empty bowels before imaging
MRI pelvis sagittal slice covers __
- entire pelvis from right to left acetabulum
- parallel to lumbosacral spine
what is the best plane to visualize uterus
MRI pelvis sagittal
MRI pelvis axial slice covers __
- position block perpendicular to endometrium
- slice covers entire uterus & ovaries
MRI pelvis coronal slice covers __
- position block parallel to endometrium
- slice covers entire uterus & ovaries
what pelvis is used to visualize pelvic organs
true pelvis
what pelvis is used for lymph node screening
false pelvis
what are the challenges of MRI pelvis
- Pelvis less sensitive to respiratory motion except upper pelvis
- Heterogenous region due to vessels / organs / bowel content / peristalsis
MRI rectum sagittal view covers __
position block parallel to interpubic cartilage & anal canal
MRI rectum axial view covers __
- position block parallel to right & left hip joints
- range = iliac crest to 1 inch below SP
MRI rectum axial oblique view covers __
position block perpendicular to rectum / any visible cancer
MRI rectum coronal oblique view covers __
- position block parallel to rectum & angled till horizontally across rectal cancer / parallel to right & left hip joint
- Slices cover entire rectum & pre-sacral space from SP to sacrum
