CT REGISTRY STUDY GUIDE QUESTIONS

CT REGISTRY STUDY GUIDE QUESTIONS

WITH CORRECT ANSWERS FOR GARANTEED

PASS What determines how much and what section of the collected raw data is used to create an image - Correct Answer Display field of view The "string of beads" artifact is most closely associated with which of the following? - Correct Answer Maximum intensity projection images A patient has a severe vagal reaction to iodinated contrast material that includes bradycardia should be given a treatment of - Correct Answer *treatment includes increasing blood pressure with IV fluids *intravenous administration of atropine to block vagal stimulation of the heart An MDCT image is reconstructed using a 512x512 matrix and a display field of view of 44 cm. If the detector collimation is set to a section width of 2.5 mm what is the volume of each voxel - Correct Answer How to solve: The linear dimension of the pixel must first be calculated by dividing the DFOV, in mm, by the matrix. This linear pixel dimension is squared to yield the pixel area in mm^2. The volume of the voxel may be calculated by multiplying the pixel area by the section width step 1. 44 cm/ 512 =0.0859 step 2. 0.0859*2.5 mm = 0.2148 step 3. move the decimal point =2.15 mm^3 For a particular CT scanner's beam quality, the linear attenuation coefficient for water is 0.20 cm-1 and for a certain tumor is 0.21 cm-1. What is the CT number of the tumor? - Correct Answer Equation (.21-.20/.21) × 1000= 50 A CT system measures the average linear attenuation coefficient of a voxel of tissue to be 0.189. The linear coefficient of water for this scanner is 0.181. The CT number assigned to the pixel representing this tissue is - Correct Answer 44 HU use equation above A CT scanner capable of producing an image that is a perfect reproduction of the actual anatomic section is said to have an MTF modulator transfer function of - Correct Answer 1 1 / 2

For an increase from 200 mA to 400 mA in a CT exam, the result would be to - Correct Answer increase low contrast resolution The major controlling factor of exam quality for coronary CTA is - Correct Answer patients heart rate... 65-70 beats per minute yield the best results What is the atomic number of xenon gas? - Correct Answer 54 The exaggeration of displayed calcification within the coronary arteries during cardiac MDCT study is referred to as - Correct Answer blooming

• the potential overestimation of vessel calcification due to partial volume artifact

a wide window setting (1500) or improving spatial resolution could help mitigate this effect Which of the following section widths would cause the greatest amount of partial volume averaging

• 1 mm
• 3 mm
• 5 mm
• 10 mm - Correct Answer D. 10 mm
• Large section widths result in long voxel lengths with possibly several tissue types accounted for

within the voxel. When a CT number is assigned to the representative pixel, the density of all the tissue types is averaged, yielding one attenuation coefficient. Narrow section widths tend to reduce partial volume effect What reduces partial volume effect? - Correct Answer narrow section widths Patient is having a severe vagal reaction to contrast including brachycardia and hypotension.. what should be done? - Correct Answer Iv fluids to raise blood pressure atrophine administration to block vagal stimulation of the heart.What type of reconstruction technique was used in the first CT scanners? - Correct Answer Iterative form of reconstruction

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