Physics Flashcards
(21 cards)
Benefit of 3D TOF vs. 2D
Higher signal to noise shorter imaging time less intravoxel dephasing more saturation effects smoother vessel contours
Acute Radiation Syndrme- Bone Marrow
>2 Gy Latent period 1-6 weeks
Acute Radiation Syndrome- GI
>8 Gy Latent Period- 5-7 days Death within 2 weeks
Acute Radiation Syndrome- CNS
>20-50 Gy Latent Period- 4-6 hours Death within 3 days
First symptom of acute radiation syndrome?
Vomiting
Phase Contrast vs. TOF
Less saturation effect but longer imaging time Velocity/Flow information Not affected by thrombus
What MR method is typically used to visualize the carotids?
2D TOF
What method is used to visualize the Circle of Willis
3D TOF
What MRA sequence is best for evaluating slow flow or venous flow?
Phase contrast
What is the standard dose of gadolinium in MRA?
0.1 mmol/kg
What MR sequence is best for calculating cardiac EF in short axis?
Short-axis gradient-echo image (flip angle 15 degrees), balanced gradient echo
What does an increase in field strength (Bo) do to chemical shift artifact?
Increases it
How is chemical shift reduced?
Increase bandwidth or use fat suppression
Most common radiation induced thyroid cancer?
papillary
Which leukemia has NOT been show to have increased incidence with radiation?
CLL
What is the doubling dose?
1 Gy per generation (dose to double spontaneous mutations)
Weighting factor for gonads?
0.08
Which tissues have a weighting factor of 0.12?
Bone marrow, stomach, colon, lungs, breasts
Mental retardation and brain development most at risk during?
Most at risk from 8-15 weeks
Threshold for diminished IQ during 8-15 weeks?
100 mGY
Dose threshold for increase in childhood cancer?
10 mGy
