A 28-Year-Old Woman With Severe Headaches
A 28-year-old woman presents to the emergency room with the worst headache of her life. Her medical history is unremarkable except for a several-year history of mild occasional headaches that respond to analgesics. However, 2 weeks ago, she developed a different type of headache that was much more severe and occurred daily. Noncontrast CT of the brain is performed. The representative images are shown in Figure 1.


(Enlarge Image)

Noncontrast CT scan of the brain. Representative axial slices are shown at the level of the third ventricle (left) and lateral ventricular bodies (right).

CT imaging relies on:

1. 
   Nonionizing radiation
   
2. 
   Radiofrequency pulses
   
3. 
   Differences in tissue attenuation of x-ray beams
   
4. 
   Uptake of radiotracers by cells
   
5. 
   Passage of air into the cerebrospinal fluid
   

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<p>Differences in tissue attenuation of x-ray beams</p>


The units of measure of the data generated by CT are:

1. 
   Roentgen units
   
2. 
   Oldendorf units
   
3. 
   Larmor units
   
4. 
   Mazziotta units
   
5. 
   Hounsfield units
   

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<p>Hounsfield units</p>


Which of the following is an advantage of CT over MRI?

1. 
   Not affected by beam hardening artifact
   
2. 
   Lack of ionizing radiation
   
3. 
   Safer in pregnancy
   
4. 
   Sensitivity for white matter disease
   
5. 
   Visualization of bony lesions
   

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<p>Visualization of bony lesions</p>


Which is true of the findings in Figure 1?

1. 
   Diffuse cerebral edema
   
2. 
   Subarachnoid hemorrhage
   
3. 
   Subdural hemorrhage
   
4. 
   Cerebral venous thrombosis
   
5. 
   Normal findings
   

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<p>Cerebral venous thrombosis</p>