Imaging Modalities

Topics in this chapter

• Imaging Physics and Modality Principles
• Computed Tomography and Radiation
• MRI Principles and Safety
• Ultrasound and Bioeffects
• Nuclear Medicine and PET
• Advanced Imaging Applications
• Imaging in Pregnancy and Pediatrics

Practice questions

1. Question 1Q-1A13C1

   A 45-year-old man undergoes an emergency MRI for suspected spinal cord compression. As he enters the scanner room, he experiences a severe panic attack and attempts to flee, inadvertently carrying a heavy iron-framed oxygen cylinder that gets violently pulled into the bore of the magnet. This phenomenon is primarily related to which physical property of the MRI scanner?

   1. A.Spatial gradient of the static magnetic field
   2. B.Radiofrequency (RF) power deposition (SAR)
   3. C.Rapidly switching gradient magnetic fields
   4. D.Permanent fringe magnetic field outside the shielding
   See the answer and solution
2. Question 2Q-940629

   Which of the following modalities utilizes ionizing radiation and relies on differences in photon attenuation coefficients of various tissues to generate cross-sectional grayscale images?

   1. A.Magnetic Resonance Imaging
   2. B.Computed Tomography
   3. C.Ultrasonography
   4. D.Thermography
   See the answer and solution
3. Question 3Q-529018

   A 30-year-old pregnant female at 12 weeks gestation requires imaging for acute right lower quadrant abdominal pain. Ultrasound is inconclusive for appendicitis. Which of the following imaging modalities is the safest next step?

   1. A.Abdominal CT with intravenous contrast
   2. B.Abdominal CT without contrast
   3. C.Magnetic Resonance Imaging (MRI) without gadolinium
   4. D.Abdominal radiography series
   See the answer and solution
4. Question 4Q-65A757

   In diagnostic ultrasound, acoustic impedance (Z) is defined as the product of tissue density and the speed of sound within that medium. When an ultrasound beam encounters a boundary between two media with a large difference in acoustic impedance, what is the primary consequence?

   1. A.Complete absorption of the sound wave
   2. B.Large reflection and minimal transmission
   3. C.Forward scattering without reflection
   4. D.Severe acoustic enhancement distal to the boundary
   See the answer and solution
5. Question 5Q-2F0755

   Which of the following radiotracers is most commonly used in Positron Emission Tomography (PET) imaging for oncological staging and metabolic evaluation?

   1. A.Technetium-99m (99mTc)
   2. B.Fluorine-18 fluorodeoxyglucose (18F-FDG)
   3. C.Iodine-131 (131I)
   4. D.Gallium-67 (67Ga)
   See the answer and solution