Diffusion MRI is a MRI method that produces ______ images of biological tissues weighted with the local microstructural characteristics of water diffusion, which is capable of showing connections between ______ regions.
in vivo; brain
In DWI, each image voxel has an image intensity that reflects a single best measurement of the rate of _________ at that location. This measurement is more sensitive to early changes after a ______ than more traditional MRI measurements such as T1/T2 rela
water diffusion; stroke
By rearranging the formula to isolate the diffusion-coefficient, it's possible to obtain an idea of the properties of diffusion occurring within a particular ______. These values called _______ can then be mapped as an image, using diffusion as the contra
voxel; apparent diffusion coefficients (ADC)
A _______(FA) map displays the anisotropic character of the diffusion in relationship to the average overall diffusion.
fractional anisotropy
water molecules move the same way in every direction
isotropic diffusion
water molecules clearly move in a preferred direction
anisotropic diffusion
Isotropic diffusion is displayed ______, anisotropic diffusion is displayed ______.
dark, bright
The FA map is one of the parametric maps for:
diffusion tensor imaging
The first successful clinical application of DWI as in imaging the brain following stroke in adults. Areas which were injured during a stroke showed up _____ on an ADC map compared to healthy tissue.
darker
Diffusion is the thermally induced motion of _____ molecules in tissues.
water
The amount of diffusion weighting is determined by the _____ of the diffusion gradients, ______ of the gradients, and the ______ between the gradient pulses.
strength, duration, time
The measurement of the rate of water diffusion (Brownian motion) is more sensitive than:
T1 or T2
A selectable parameter in DWI is the B-value. Higher b-values lead to ______ signal loss.
increased
The final result in a perfusion study is a set of calculated images which indicate various ______ characteristics.
flow
Unit of measurement in perfusion imaging
relative Cerebral Blood Volume (rCBV)
rCBV is proportional to degree of:
neovascularity or capillary density
- differentiating tumor from non-tumor, and primary brain neoplasm from secondary lesions
- glioma grading
- stereotactic biopsy guidance
- differentiating tumor recurrence from radiation necrosis
uses of perfusion
- ultra fast gradient echo sequence w/ bolus injection of IV Gad @ 4cc/sec
- exponential time curves generated on separate workstation, w/ multiple ROI's generated to calculate specific rCBV's
- NAWM (normal appearing white matter) established as the cont
perfusion imaging protocol
DSC aka _______, utilized in brain perfusion studies, or better known as:
dynamic susceptibility contrast, T2* gradient echo Perfusion Imaging
DCE aka _______, or basic _____ imaging (pituitary or prostate dynamic sequences, longer acquisition times/dynamic compared to DSC)
dynamic contrast enhancement, T1 perfusion
the imaging technique that employs a very rapid pulse sequence while the patient is at rest or performing a task is:
functional MRI
allows doctors to obtain biochemical information about the chemical components in tissues of the human body in a non-invasive way
spectroscopy (MRS)
The final result of a spectroscopy study is a spectrum of specific _______ detected.
metabolites
A normal brain tissue 1H (Hydrogen) spectrum contains the metabolites:
Choline, Lactate, Creatine, and N-acetyl Aspartic Acid (NAA)
The _____ of the peak on an MR spectrum correlates to the _____ of a substance that was detected.
height, amount
N-acetyl aspartate (NAA): with its major resonance peak at _____, decreased levels of NAA indicate loss/damage to ______ tissue, which results from many types of insults to the brain. Its presence in normal conditions indicates neuronal and axonal integri
2.02ppm, neuronal
Choline: with its major peak at _____, it's known to be assoc w/ membrane turnover, or ______ in cell division. Increased choline indicates increase in cell production or membrane breakdown, which can suggest demyelination or presence of _______.
3.2ppm, increase, malignant tumors
Creatine & phosphocreatine: with its major peak at ______, creatine marks metabolism of brain energy. Gradual loss of creatine in conjunction w/ other major metabolites indicates tissue _____ or major cell death resulting from disease, injury, or lack of
3.0pp, death, cranialcerebral
Lipids: with their major aliphatic peaks located in the ______ range, increase in lipids is seen is also indicative of _____. These spectra are easily contaminated, as lipids are not only present in the brain, but also in other biological tissue such as _
0.9-1.5ppm, necrosis, fat
Lactate: reveals itself as a doublet at ______. Normally lactate is not visible for its concentration is lower than the detection limit of MRS, however presence of this peak indicates ______ has been initiated in an oxygen deficient environment. Several c
1.3ppm, glycolysis
myo-inositol: with its major peak at _______, an increase in Myo-inositol has been seen in patients with:
3.56ppm; Alzheimer's, dementia, and HIV
Glutamate and Glutamine: these amino acids are marked by a series of resonance peaks between ______. 2 major conditions that result in elevated levels of glutamine and glutamate are:
2.2-2.4ppm; hyperammonemia and hepatic encephalopathy