CT Simulated Exam 3

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CT Simulated Exam 3
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2015-10-12 15:02:31
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CT Registry Review Simulated Exam
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CT Registry Review Simulated Exam 3
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  1. 1. During CT exams of the chest and abdomen, the highly radiosensitive breast tissue can be protected with minimal image artifact with the use of specialized shielding composed of:
    A. barium
    B. lead
    C. bismuth
    D. aluminum
    C. bismuth

    In-plane bismuth shielding of particularly radiosensitive areas such as the orbits, thyroid, and breast tissue can substantially reduce effective radiation dose.
    (this multiple choice question has been scrambled)
  2. 2. The use of water as an oral contrast material for CT of the abdomen and/or pelvis has several potential advantages, including:
    1. increased palatability and improved patient comfort
    2. better demonstration of enhancing bowel wall
    3. no interference with 3D application
    A. 1 only
    B. 1 and 2 only
    C. 1 and 3 only
    D. 1, 2, and 3
    D. 1, 2, and 3

    The use of water as a negative contrast agent is becoming increasingly common for many CT applications for the abdomen and pelvis.
    (this multiple choice question has been scrambled)
  3. 3. If all other technical factors remain constant, which of the following would serve to decrease patient radiation dose during a helical exam?
    A. increased matrix size
    B. increased pitch
    C. decreased scan field of view
    D. decreased filtration
    B. increased pitch

    With a SSCT system, pitch equals the ratio of the table speed with the section thickness. As the detector pitch is increased, the patient translates through the gantry at a greater rate relative to each rotation of the x-ray tube, resulting in the acquisition of a given volume of anatomy with fewer tube-detector rotations and shorter scan times. Increases in pitch therefore allow for reduced pt radiation dose while covering the necessary anatomic area.
    (this multiple choice question has been scrambled)
  4. 4. A patients blood pressure is measured as 140/70 mm Hg. The number 140 represents:
    A. the pressure within the arterial vessels during contraction of the heart
    B. the pressure exerted on the chambers of the heart while relaxed
    C. the pressure within the arterial vessels while the heart is relaxed
    D. the pressure exerted on the chambers of the heart during a contraction
    A. the pressure within the arterial vessels during contraction of the heart

    The top number of a blood pressure measurement is the systolic pressure. This is a measure of the pressure exerted on the arterial walls during a contraction of the heart.
    (this multiple choice question has been scrambled)
  5. 5. A(n) ______ contrast material may be described as one that does not dissociate into charged particles in solution.
    A. osmolar
    B. neutral
    C. non-ionic
    D. ionic
    C. non-ionic

    Non-ionic contrast materials do not dissociate into charged particle (ions) when placed in solution. Ionic contrast materials are salts that form independent particles in aqueous solutions.
    (this multiple choice question has been scrambled)
  6. 6. Which of the following radiation dose indices is a measure of the total radiation exposure for an entire series of CT images?
    A. dose length product (DLP)
    B. multiple scan average dose (MSAD)
    C. CTDI100
    D. CTDIvol
    A. dose length product (DLP)

    The CTDIvol is a measure of dose to each slice along a helically acquired volume. The dose length product (DLP) is calculated by multiplying the CTDIvol by the total scan length.
    (this multiple choice question has been scrambled)
  7. 7. Proper immobilization during a CT procedure a CT procedure may involve the use of:
    1. soft, hook-and-loop (velco) immobilization straps
    2. adhesive medical tape
    3. good patient communication
    A. 1 and 3 only
    B. 1 only
    C. 1 and 2 only
    D. 1, 2, and 3
    A. 1 and 3 only

    CT manufacturers routinely supply comfortable, nonadhesive straps and cushions to help maintain motion-free pt positioning. Adhesive tape should not be routinely used because of the abrasive effects of tape removal. Good pt communication is a key immobilization technique. Proper instructions for remaining still, suspending respiration, not swallowing, and so on, help ensure pt cooperation and yield higher quality CT examinations.
    (this multiple choice question has been scrambled)
  8. 8. The normal range of glomerular filtration rate (GFR) for men is:
    A. 80 ± 10mL/min/m²
    B. 70 ± 14mL/min/m²
    C. 50 ± 14mL/min/m²
    D. 60 ± 10mL/min/m²
    B. 70 ± 14mL/min/m²

    Normal range of GFR is 70 ± 14 mL/min/m² for men and 60 ± 10 mL/min/m² for women.
    (this multiple choice question has been scrambled)
  9. 9. Effective dose is a relative radiation dose measurement term that accounts for the:
    A. tissue radiosensitvity
    B. beam pitch
    C. collimation
    D. detector pitch
    A. tissue radiosensitivity

    Effective dose accounts for the type of tissue that radiation is deposited in. Different tissues are assigned weighting factors on the basis of their individual radiosensitivities.
    (this multiple choice question has been scrambled)
  10. 10. Risk factors for contrast-induced nephrotoxicity (CIN) include:
    1. diabetes
    2. advanced age
    3. hematuria
    A. 1 only
    B. 1 and 2 only
    C. 3 only
    D. 1, 2, and 3
    B. 1 and 2 only

    Risk factors for contrast-induced nephrotoxicity (CIN) include pre-existing compromise of renal function, dehydration, diabetes, myeloma, advanced age, and cardiovascular disease.
    (this multiple choice question has been scrambled)
  11. 11. The reduction in number of infectious organisms without a complex elimination is termed.
    A. immunization
    B. sterilization
    C. medical asepsis
    D. surgical asepsis
    C. medical asepsis

    Medical asepsis is the reduction in number of infectious agents without the complete elimination of the organisms. It is accomplished through the use of soap, water, and many other types of disinfectant materials.
    (this multiple choice question has been scrambled)
  12. 12. Which of the following is the preferred range for patient heart rate for optimal cardiac CT studies?
    A. 75-85 bpm
    B. 65-75 bpm
    C. 85-95 bpm
    D. > 100 bpm
    B. 65-75 bpm

    Pt's with slower heart rates exhibit longer diastolic phases, which yield higher-quality cardiac CT exams. The preferred heart rate for optimal imaging on most MSCT systems is 65 beats per minute (bpm). Newer systems at the 64-slice level and beyond are capable of acquiring adequate cardiac CT images at higher heart rates.
    (this multiple choice question has been scrambled)
  13. 13. Late effects of radiation, such as genetic mutations, may occur with even small doses of radiation and are termed:
    A. stochastic
    B. nonstochastic
    C. somatic
    D. chronic
    A. stochastic

    A stochastic, or random, effect of radiation exposure is one having no threshold dose. Common examples of stochastic radiation effects are genetic mutations and cancer.
    (this multiple choice question has been scrambled)
  14. 14. Urticaria is which of the following:
    A. bronchospasm
    B. hives
    C. severe nausea with associated vomiting
    D. urinary tract infection
    B. hives

    Urticaria is a common adverse reaction to iodinated intravenous contrast material. Characterized by the presence of wheals or localized skin eruptions, it is commonly referred to as "hives"
    (this multiple choice question has been scrambled)
  15. 15. Which of the following type(s) of oral contrast material could cause peritonitis if leakage from the digestive tract occurs from perforation?
    A. effervescent granules
    B. barium sulfate
    C. diatrizoate (hypaque)
    D. iopamidol (gastrografin)
    B. barium sulfate

    Barium sulfate is not water soluble and is not easily absorbed by the body. If it leaks out of the digestive tract because of perforation, this agent may cause peritonitis.
    (this multiple choice question has been scrambled)
  16. 16. Which of the following is not an advantage of an automatic power injector over the manual bolus method of IV contrast agent administration?
    A. shorter injection times
    B. consistent contrast agent of administration for all patients
    C. decreased risk of contrast induced nephrotoxicity (CIN)
    D. uniform contrast enhancement throughout the exam
    C. decreased risk of contrast induced nephrotoxicity (CIN)

    The use of automatic injectors does not decrease the risk of CIN in comparison with the manual bolus technique. Automatic injectors do offer shorter injection times, more consistent administration, and greater enhancement.
    (this multiple choice question has been scrambled)
  17. 17. Which of the following is/are severe adverse reaction(s) to iodinated IV contrast media?
    1. anaphylaxsis
    2. urticaria
    3. vomiting
    A. 1 and 3 only
    B. 1, 2, and 3
    C. 1 only
    D. 1 and 2 only
    C. 1 only

    Severe reactions to iodinated contrast material include anaphylaxis, shock, cardiac arrest, and death. Urticaria and vomiting may be considered mild or moderate reactions, depending on their severity.
    (this multiple choice question has been scrambled)
  18. 18. Which of the following laboratory values is the most dependable measure of renal failure?
    A. PT
    B. PTT
    C. creatinine
    D. BUN
    C. creatinine

    Serum creatinine levels are the most accurate and dependable laboratory measures of renal function. The blood urea nitrogen (BUN) level may be affected by many variables and is not a suitable test of renal function by itself. BUN levels are usually evaluated in conjunction with creatinine levels for a more accurate measurement of renal function.
    (this multiple choice question has been scrambled)
  19. 19. Which of the following angiocatheter sizes may be safely used for the automated power injection of iodinated contrast agents at flow rates higher than 3 mL/sec?
    1. 18 gauge
    2. 20 gauge
    3. 22 gauge
    A. 3 only
    B. 1, 2, and 3
    C. 1 only
    D. 1 and 2 only
    D. 1 and 2 only

    22-gauge angiocatheters are sufficient for flow rates up to 3 mL/sec. 20-gauge or larger angiocatheters should be utilized whenever flow rates exceed 3 mL/sec.
    (this multiple choice question has been scrambled)
  20. 20. Which of the following portions of the electrocardiogram (ECG) corresponds to the period of atrial systole?
    A. alpha wave
    B. P wave
    C. T wave
    D. QRS complex
    B. P wave

    Atrial systole refers to the contraction of the left and right atria. The onset of the P wave on an ECG corresponds to atrial systole.
    (this multiple choice question has been scrambled)
  21. 21. Which of the following statements is true regarding the relationship between multiple scan average dose (MSAD) and image spacing during axial (step-and-shoot) scanning?
    A. MSAD increases with noncontiguous scans
    B. MSAD increases with overlapping scans
    C. MSAD equals the product of image spacing and pitch
    D. MSAD decreases with overlapping scans
    B. MSAD increases with overlapping scans

    During axial scanning, overlapping scans increase the pt radiation dose, whereas gaps between slices decrease the dose.
    (this multiple choice question has been scrambled)
  22. 22. Which of the following terms is used to describe the IV injection of medication or contrast agent in one complete dose over a short time?
    A. infusion
    B. infus-a-port
    C. IV drip
    D. bolus
    D. bolus

    A bolus injection is one in which the entire volume of medication or contrast agent is administered at once over a short period.
    (this multiple choice question has been scrambled)
  23. 23. Used in determining the biologic effect of iodinated contrast media, the term ____ refers to the number of ions formed when a substance dissociates in solution.
    A. iodination
    B. concentration
    C. solubility
    D. osmolality
    D. osmolality

    Osmolality or osmotic concentration is the number of ions or particles formed when a substance (solute) dissociates in a given solution. It is described as the number of particles in solution per kg of water.
    (this multiple choice question has been scrambled)
  24. 24. The dosimetry index used to approximate the radiation dose for CT sections acquired during a helical scan is called the:
    A. CTDIvol
    B. effective dose
    C. CTDIw
    D. equivalent dose
    A. CTDIvol

    CTDIvol is used to approximate the dose from a helical scan. It corresponds to the axially acquired CTDIw divided by the helical pitch. Whereas CTDIw approximates dose along the x- and y-axes of the acquired CT image, CTDIvol also includes dose along the z-axis of the scan acquisition. As pitch increases, the dose per section, or CTDIvol, decreases.
    (this multiple choice question has been scrambled)
  25. 25. The injection rate of an automatic injector is set at 1.5mL/sec. What is the injection time for a contrast agent volume of 150mL?
    A. 90 seconds
    B. 120 seconds
    C. 60 seconds
    D. 100 seconds
    D. 100 seconds

    150ml of contrast divided by 1.5mL/sec = 100 seconds.
    (this multiple choice question has been scrambled)
  26. 26. Which of the following must be included when one is obtaining informed consent for an invasive procedure?
    1. explanation of the exam technique
    2. the possible risks and benefits of the exam
    3. alternatives to the procedure involved
    A. 1, 2, and 3
    B. 1 and 2 only
    C. 1 and 3 only
    D. 1 only
    A. 1, 2, and 3

    Informed consent must be obtained from the pt prior to any invasive procedure. The components of informed consent are thorough explanations of the procedure, any possible risks in addition to the proposed benefits, and alternatives to the procedure.
    (this multiple choice question has been scrambled)
  27. 27. Which of the following techniques may be employed to reduce patient radiation dose during a cardiac CT exam?
    A. retrospective ECG gating
    B. z-axis interpolation
    C. prospective ECG gating
    D. multisegment reconstruction
    C. prospective ECG gating

    During MSCT cardiac studies, prospective gating can be used to reduce pt dose. In this technique, ECG-triggered tube current modulation allows for pulses of x-ray energy to be used rather than continuous exposure. Both retrospective ECG gating and multisegment reconstruction require constant radiation exposure throughout multiple heartbeats.
    (this multiple choice question has been scrambled)
  28. 28. Which of the following may be considered a low-osmolar contrast medium?
    1. iothalamte meglumine
    2. diatrizoate sodium
    3. iohexol
    A. 3 only
    B. 1, 2, and 3
    C. 1 only
    D. 1 and 2 only
    A. 3 only

    Low-osmolar contrast media (LOCM) are non-ionic agents that do not dissociate into charged particles (ions) in solution. Examples of LOCM are iohexol (Omnipaque), iopamidol (Isovue), and ioversol (Optiray).
    (this multiple choice question has been scrambled)
  29. 29. Following the intrathecal injection of an iodinated contast agent for a post-myelography CT study of the lumbar spine, the patient should be instructed to:
    A. resume normal activity
    B. rest for 8-24 hours with the head slightly elevated
    C. take a cleansing enema
    D. rest for 8-24 hours in the trendelenburg position
    B. rest for 8-24 hours with the head slightly elevated

    In an effort to reduce the possibility of headaches after a CT examination involving an intrathecal injection of contrast material, the pt should rest for 8-24 hours with the head slightly elevated (35-45 degrees).
    (this multiple choice question has been scrambled)
  30. 30. Compared with single slice CT (SSCT), patient radiation dose during a multidetector CT study may be higher because of:
    1. use of a cone beam of radiation
    2. acquisition at thinner sections widths
    3. higher powered x-ray tubes
    A. 1 only
    B. 1 and 2 only
    C. 1 and 3 only
    D. 1, 2, and 3
    B. 1 and 2 only

    Dose can be considerably higher with MSCT owing to a decrease in the focal spot-detector distance, the use of a cone beam instead of a more z-axis-collimated fan beam, an increase in number of imaging phases enable by shorter scan times, and the acquisition of thinner sections for improvement of 3D and MPR images.
    (this multiple choice question has been scrambled)
  31. 31. Which of the following pharmaceuticals ma be administered prior to a cardiac CT procedure in an effort to improve visualization of the coronary vessels?
    1. β-blocker
    2. nitoglycerin
    3. metformin
    A. 2 only
    B. 1 and 2 only
    C. 1, 2, and 3
    D. 1 only
    B. 1 and 2 only

    β-Adrenergic receptor blocking agents (β-blockers) may be used to reduce pt's heart rate,and sublingual nitrogylcerin may be administered to cause dilation of the coronary vessels. The use of these pharmaceuticals may improve the overall visualization of the coronary vessels during a cardiac CT examination. Please consult the physician and/or department protocol for further information regarding pharmaceutical administration for cardiac CT procedures.
    (this multiple choice question has been scrambled)
  32. 32. A _____ is a benign, highly vascular mass commonly found in the liver.
    A. hemogenic carcinoma
    B. hemangioma
    C. vasculoma
    D. hematoid
    B. hemangioma

    A hemangioma is a congenital, benign mass containing blood-filled spaces. It is commonly found in the liver and spleen.
    (this multiple choice question has been scrambled)
  33. 33. Which of the following is the preferred contrast enhancement phase for CT acquision of the spleen?
    A. equilibrium phase
    B. portal venous phase
    C. pre-contrast phase
    D. arterial phase
    B. portal venous phase

    The preferred timing for CT acquisition of the spleen is the portal venous phase (60-70 seconds), when a more homogenous pattern of enhancement is demonstrated.
    (this multiple choice question has been scrambled)
  34. 38. Which of the following terms describes the appearance of an acute subdural hematoma on a CT image of the brain?
    A. isodense
    B. hyperdense
    C. radiolucent
    D. hypodense
    B. hyperdense

    Subdural hematomas are collections of blood that occur throughout the subdural space after traumatic injury to the head. An acute subdural hematoma is one that has manifested clinically during the first 24 hours after the injury. During this stage, the hematoma appears hyperdense compared with normal brain tissue because of the initial clotting that has occured and the concentration of hemoglobin in fresh blood.
    (this multiple choice question has been scrambled)
  35. 39. The angiographic assessment known as a "CT run-off" evaluates the peripheral arterial tree from the renal arteries through the:
    A. aortic bifurcation
    B. aortic arch
    C. superior mesenteric artery
    D. distal lower extremity
    D. distal lower extremity

    The angiographic assessment of the peripheral arterial tree from the renal arteries through the feet is commonly referred to as a "CT runoff"
    (this multiple choice question has been scrambled)
  36. 40. During a PET-CT exam, the amount of FDG uptake in an anatomic region is directly proportional to the areas:
    A. size
    B. central vs peripheral location
    C. metabolic activity
    D. radiosensitivity
    C. metabolic acitivity

    Malignant cells demonstrate an increase in metabolic activity and glucose utilization. Once administered, fludeoxyglucose F18 (FDG) mimics glucose and is taken up by normal and abnormal tissue. The amount of FDG uptake is directly proportional to the area's metabolic activity. Malignant cells will take up a disproportionately larger amount of FDG than metabolically normal tissue.
    (this multiple choice question has been scrambled)
  37. 44. Accurate demonstration of _____ would most likely require the IV injection of an iodinated contrast agent during a CT study of the chest.
    A. a dissecting aortic aneurysm
    B. asbestosis
    C. a solitary pulmonary nodule
    D. pneumonia
    A. a dissection aortic aneurysm

    Intravenous administration of an iodinated contrast agent is vital to making an accurate diagnosis of a dissecting aortic aneurysm. The contrast agent helps outline the wall of the aorta and improves visualization of any division within it. Because of differences in blood flow, CT numbers within the actual lumen of the aorta are different from those in the dissected portion.
    (this multiple choice question has been scrambled)
  38. 45. Vascular components of the brain's blood supply known as the Circle of Willis include the:
    1. internal carotid arteries
    2. basilar artery
    3. anterior communication artery
    A. 1 and 3 only
    B. 1, 2, and 3
    C. 1 and 2 only
    D. 2 only
    A. 1 and 3 only

    The Circle of Willis is composed of the anterior cerebral, anterior communicating, internal carotid, posterior cerebral, and posterior communicating arteries. The basilar artery is an important vessel supplying blood to the brain, but it is not part of the Circle of Willis.
    (this multiple choice question has been scrambled)
  39. 46. The benign mass of the eighth cranial nerve known as a vestibular schwannoma may be also termed a(n):
    A. olfactory neuroblastoma
    B. acoustic neuroma
    C. optic nerve glioma
    D. hypoglossal adenoma
    B. acoustic neuroma

    This type of mass most often involves the vestibular portion of the nerve bundle, with deleterious effects on balance and equilibrium. The eighth cranial nerve is the vestibulocochlear nerve responsible for both hearing and balance.
    (this multiple choice question has been scrambled)
  40. 51. The thick, layered portion of the peritoneum responsible for attaching portions of the intestines to the bowel wall is called the:
    A. gerota fascia
    B. mesentery
    C. falciform ligament
    D. ligamentum teres
    B. mesentery

    The mesentery is a double fold of the peritoneum that attaches the jejunum and ileum of the small bowel to the abdominal wall.
    (this multiple choice question has been scrambled)
  41. 52. After initiation of rapid bolus administration of an iodinated contrast agent, the nephrographic phase of renal contrast enhancement occurs at approximately:
    A. 30-40 seconds
    B. 70-90 seconds
    C. 20-25 seconds
    D. 3 - 5 minutes
    B. 70-90 seconds

    The nephrographic phase occurs between 70-90 seconds after the start of injection. Enhancement of the renal cortex and medulla reaches equilibrium, providing optimal sensitivity for parenchymal lesions.
    (this multiple choice question has been scrambled)
  42. 53. Retrospective ECG gating utilizes which of the following portions of the cardiac cycle for image reconstruction?
    1. atrial systole
    2. ventricular systole
    3. cardiac diastole
    A. 1 and 2 only
    B. 3 only
    C. 2 only
    D. 2 and 3 only
    B. 3 only

    Complete cardiac diastole is the period of relaxation after heart contraction. Diastole is the portion of the cardiac cycle when coronary artery motion is the slowest and cardiac motion is at its lowest. For evaluation of the coronary arteries, the MDCT system utilizes only the diastolic portion of the acquisition in the reconstruction process.
    (this multiple choice question has been scrambled)
  43. 58. Which of the following is a common complication of CT-guided biopsy of the lung?
    A. pulmonary embolism
    B. pneumothorax
    C. pneumoconiosis
    D. aspiration
    B. pneumothorax

    Pneumothorax is one of the most common complications of CT-guided needle biopsy of the lung. The term pneumothorax describes a collection of air in the pleural space. A pneumothorax causes a portion of the lung to collapse, often resulting in the placement of a chest tube to re-inflate the lung.
    (this multiple choice question has been scrambled)
  44. 59. An enema is indicated prior to a CT exam of the pelvis to administer positive contrast material into the large bowel. Which of the following dosages would be sufficient to opacify the rectosigmoid region?
    A. 500-750 mL
    B. 300-500 mL
    C. 900-1100 mL
    D. 150-250 mL
    D. 150-250 mL

    Positive contrast material can be administered into the large bowel via enema to achieve thorough opacification. A dosage of 150-250 mL should be sufficient to opacify the rectosigmoid region. Doses of 300 to 500 mL may be necessary to opacify the large bowel in its entirety.
    (this multiple choice question has been scrambled)
  45. 60. A CT exam of the lumbar spine reveals a herniated disc at the level of L2-L3. Which of the following reformation planes would best demonstrate posterior compression of the disc material onto the spinal cord?
    A. oblique
    B. sagittal
    C. coronal
    D. axial
    B. sagittal

    A sagittally reformatted image would demonstrate the relationship of the disc material as it protrudes posteriorly into the spinal cord.
    (this multiple choice question has been scrambled)
  46. 64. A common formula used to calculate the maximum dosage of IV iodinated contrast material used in any CT exam is:
    A. 5mg per kg of body weight
    B. 2mL per kg of body weight
    C. 5mL per lb of body weight
    D. 1mL per lb of body weight
    B. 2mL per kg of body weight

    Dosage calculations for intravenous contrast agent administration should adhere to the general guiding principle of injecting the smalles quantity of contrast agent possible to meet the technical requirements of the examination. The maximum dose for any procedure should not exceed 2 mL per kg of body weight.
    (this multiple choice question has been scrambled)
  47. 65. Which of the following MDCT exams may include endobrachial views?
    A. CTA of the aorta
    B.HRCT of the lungs
    C. virtual bronchoscopy
    D. virtual colonoscopy
    C. virtual bronchoscopy

    CT bronchography is a 3D examination of the tracheobronchial tree. It may include detailed endobrachial views, on which the viewer has the perspective of flying through the trachea and bronchi, as in conventional bronchoscopy. These specialized 3D reconstructions are commonly referred to as virtual bronchoscopy.
    (this multiple choice question has been scrambled)
  48. 66. The Stanford type A dissecting aneurysm affects which portion of the aorta?
    a. ascending thoracic
    d. descending thoracic
    c. abdominal
    d. bifurcation
    a. ascending thoracic

    • Stanford type A dissecting aneurysms affect the ascending aorta. Stanford type B dissecting aneurysms affect the descending aorta.
  49. 67. During the HRCT of the lungs, edematous changes in the posterior lungs may be differentiated by positioning of the patient in the ____ position.
    A. supine
    B. prone
    C. left lateral decubitus
    D. right lateral decubitus
    B. prone

    HRCT images with the pt in the prone position can be acquired to differentiate the dependant edematous changes often seen in the lung bases.
    (this multiple choice question has been scrambled)
  50. 68. The firm, outer portion of each intervertebral disc is called the:
    A. nucleus pulposus
    B. nucleus prepositus
    C. anulus stapedius
    D. anulus fibrosus
    D. anulus fibrosus

    The outer portion of an intervertebral disc is the anulus fibrosus.
    (this multiple choice question has been scrambled)
  51. 72. Which of the following refers to the surgical resection of the pancreas and duodenum for treatment of pancreatic carcinoma?
    A. Roux-en-Y anastomosis
    B. endoscopic retrograde cholangiopancreatography (ERCP)
    C. cholecystectomy
    D. Whipple procedure
    D. Whipple procedure

    Whipple procedure is the surgical resection of the pancreas and duodenum (pancreaticoduodenectomy) for the treatment of pancreatic carcinoma.
    (this multiple choice question has been scrambled)
  52. 73. During which of the following IV contrast phases does the bladder wall enhance?
    A. corticomedullary
    B. nephrographic
    C. excretory
    D. early arterial
    B. nephrographic

    Nephrographic (70-90 seconds) imaging provides enhancement of the bladder wall, which is used to evaluate the extent of tumor infiltration.
    (this multiple choice question has been scrambled)
  53. 74. Coronary artery calcium (CAC) quantitation by MDCT exam is used primarily to assess:
    A. aortic aneurysm
    B. ejection fraction
    C. coronary artery stenosis
    D. atherosclerotic disease
    D. atherosclerotic disease

    The primary clinical indication for MDCT coronary artery calcium (CAC) quantitations is the assessment of atherosclerotic disease. The presence of coronary artery calcium (CAC) is a specific indicator of atherosclerotic disease.
    (this multiple choice question has been scrambled)
  54. 79. A specialized CT exam involving the administration of an enteral contrast agent directly into the small bowel via nasogastric tube is called:
    A. CT colonoscopy
    B. CT enterography
    C. CT enteroclysis
    D. CT colonography
    C. CT enteroclysis

    CT enteroclysis is a specialized evaluation of the small bowel whereby a nasogastric catheter is placed into the duodenum under fluoroscopic guidance. 1.5-2.0 L of enteral contrast agent is administered directly into the small intestine for maximal opacification. Non-IV contrast, thin-section (0.6-1.25 mm) CT images are acquired through the abdomen and pelvis.
    (this multiple choice question has been scrambled)
  55. 80. The epithelial lining of the urinary tract is called the:
    A. pyelocalyx
    B. haustrum
    C. urothelium
    D. omentum
    C. urothelium

    The urothelium lines most of the urinary tract, including the renal pelvis, ureters, and bladder. The transitional portion of the urothelium can be the site of transitional cell carcinoma (TCC), a common malignancy of the bladder, ureters, and kidneys.
    (this multiple choice question has been scrambled)
  56. 81. A common area for inflammation, the primary drainage opening within the sinus cavities is referred to as the:
    A. ostiomeatal complex
    B. mucosal fossa
    C. external olfactory canal
    D. adenovestibular complex
    A. ostiomeatal complex

    The ostiomeatal complex is an important sinus opening that allows for drainage of the frontal, ethmoid, and maxillary sinuses. It is a common area for sinusitis, or inflammation of the sinuses.
    (this multiple choice question has been scrambled)
  57. 87. During a CT exam of the chest, the administration of a saline flush following the bolus injection of iodinated IV contrast media helps alleviate artifact from dense contrast in the:
    A. descending aorta
    B. inferior vena cava
    C. superior vena cava
    D. ascending aorta
    C. superor vena cava

    The use of a saline flush reduces artifact from dense contrast in the superior vena cava. The streaking artifact can hamper visualization of the upper mediastinum and surrounding lung tissue.
    (this multiple choice question has been scrambled)
  58. 88. Delayed post-contrast acquisition of the lower extremities following a CTA of the pulmonary arteries is termed:
    A. femoral CTA
    B. iliac CTA
    C. CT perfusion
    D. CT venography
    D. CT venography

    Shortly after a CTPA study, CT venography (CTV) of the lower extremities for the identification of deep vein thrombosis (DVT) may also be performed. After the CTPA acquisition, a delay of 2-3 minutes is employed, and an acquisition is made from the iliac crest to the ankles.
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  59. 93. The overall quality of MPR and volume-rendered 3D images for a carotid artery CTA may be improved by:
    1. reducing the kVp for an increase in displayed vessel opacification and contrast
    2. retrospective reconstruction with a 50% overlap in section increment
    3. bolus-tracking software to maximize contrast enhancement
    A. 1 and 2 only
    B. 1, 2, and 3
    C. 2 and 3 only
    D. 2 only
    B. 1, 2, and 3

    Reductions in kVp, overlapping axial sections, and precise bolus timing are all important factors in the production of high-quality CTA examinations.
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  60. 94. Which of the following is the most common sign of GI pathology on CT images?
    A. air distention
    B. wall thickening
    C. fluid collection
    D. dense fecal matter
    B. wall thickening

    The most important identifying sign of GI pathology on CT examination is wall thickening. The ability to evaluate the gastric and bowel walls is a crucial component of the successful CT evaluation of the GI system. Distention and opacification with oral media, coupled with contrast enhancement through IV administration, offer the best demonstration of the GI wall.
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  61. 95. Often evaluated during body CTA examinations, the branches of the celiac axis are the:
    1. left gastric artery
    2. common hepatic artery
    3. splenic artery
    A. 2 and 3 only
    B. 3 only
    C. 1, 2, and 3
    D. 1 only
    C. 1, 2, and 3

    The branches of the celiac axis are the left gastric artery, common hepatic artery, and splenic artery.
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  62. 100. Vital components of a CT urogram (CT-IVP) protocol include:
    1. administration of 1200 to 1500mL of a positive oral contast agent 90 minutes prior to exam
    2. thin-section excretory phase of imaging of the entire urinary tract
    3. volume-rendered 3D and maximum intensity projection (MIP) imaging of the urinary tract
    A. 1, 2, and 3
    B. 2 only
    C. 2 and 3 only
    D. 1 and 2 only
    C. 2 and 3 only

    Water is the preferred oral contrast for CT urograms, because its use avoids the interference seen with denser materials when one is producing volume-rendered and MIP images. Additional protocol considerations include pre-contrast acquisition of the urinary tract and post-contrast nephrographic phase imaging. Excretory phase imaging occurs after a delay of 5-15 mins and may be aided by the IV drip administration of approx. 250 mL of normal (0.9%) saline to improve urinary tract opacification.
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  63. 101. Arterial phase CT imaging of the liver is used to optimally demonstrate which of the following?
    A. hepatic cyst
    B. fatty infiltration
    C. portal vein thrombosis
    D. hepatocellular carcinoma (HCC)
    D. hepatocellular carcinoma (HCC)

    Hepatocelluar carcinomas (HCCs) are hypervascular lesions that appear hyperdense in comparison with surrounding normal hepatic parenchyma during the arterial phase of contrast enhancement.
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  64. 102. Non-contrast CT of the urinary tract is a valuable tool in the investigation of:
    A. ureteral duplication
    B. transitional cell carcinoma (TCC)
    C. urinary tract lithiasis
    D. renal artery stenosis
    C. urinary tract lithiasis

    Lithiasis refers to the presence of stones. Unenhanced helical CT of the urinary tract has become the standard for the investigation of urinary tract lithiasis.
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  65. 103. Which of the following techniques may be used to improve visualization of the vocal cords during a CT exam of the neck?
    1. oral administration of thick barium paste
    2. CT acquisition with the mouth open as widely as tolerable
    3. scanning while the patient phonates the letter "e"
    A. 2 only
    B. 1, 2, and 3
    C. 1 and 3 only
    D. 3 only
    D. 3 only

    Phonation during acquisition may be used to demonstrate abnormal mobility of the vocal cord(s). A thin-section (0.5-2 mm) sequence is obtained during which the pt is instructed to phonate a low, steady "E" sound during the entire scan duration.
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  66. 107. Percutaneous drainage under CT guidance may be used for the aspiration of which of the following pathologic process?
    A. chronic sudbural hematoma
    B. dissecting aortic aneurysm
    C. hydrocephalus
    D. abdominal abscess
    D. abdominal abscess

    CT is commonly used during percutaneous aspiration and drainage procedures. CT images enable the radiologist to view the precise location of abnormal fluid collections and allow for accurate planning of a safe access route for the aspiration procedure. When performed properly, CT-guided aspiration of an abscess can be a valuable nonsurgical therapeutic technique. This type of procedure can also be used to reduce other types of abnormal fluid collections, including cysts, bilomas, urinomas, and lymphoceles.
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  67. 108. The device contructed to house the x-ray tube and date acquisition system (DAS) for a CT scanner is called the:
    A. generator
    B. array processor
    C. CPU
    D. gantry
    D. gantry

    The x-ray tube and data acquisition system (DAS) are housed within the gantry of a CT scanner. The gantry aperture is the circular opening through which the pt moves during scanning.
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  68. 109. Third generation CT scanners use which of the following scan geometries?
    A. rotate-stationary
    B. transaxial
    C. rotate-rotate
    D. translate-rotate
    C. rotate-rotate

    Both the x-ray tube and detector array rotate around the pt during scanning with a 3rd generation CT unit.
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  69. 110. A quality control procedure determines that the low contrast resolution of a CT scanner is extremely poor. Likely causes are:
    1. tube arcing
    2. increased electronic noise
    3. decreased tube output
    A. 2 and 3 only
    B. 1 only
    C. 1 and 3 only
    D. 1, 2, and 3
    A. 2 and 3 only

    The scanner's reduced low-contrast resolution is most likely the cause of increased noise. When the noise level of a CT image increases, the low-contrast resolution decreases. Decreased pt dose implies that the signal-to-noise ratio has decreased, thus raising the noise level of the image. The same situation would apply for an increase in electronic noise.
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  70. 111. When one is viewing a maximum intensity projection (MIP) image, each pixel represents:
    A. the maximum attenuation occuring within the voxel
    B. the average attenuation occuring within the voxel
    C. the minimum attenuation occuring within the voxel
    d. all attenuation occuring within the voxel above a set threshold value
    A. the maximum attenuation occuring within the voxel

    MIP images display only the maximum pixel value along a ray traced through the object to the viewer's assumed perspective in front of the viewing monitor. As the viewer faces a MIP image, each pixel represents the maximum attenuation that occurs in the associated voxel.
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  71. 112. A CT image is reconstructed using a 512² squared matrix and a display field of view of 40 cm. What is the linear dimension of each pixel?
    A. 0.78 mm
    B. 1.28 mm
    C. 0.08 mm
    D. 0.0015 mm
    A. 0.78 mm

    400 mm/512 mm= 0.78 mm

    field of view/matrix size=linear pixel dimension

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  72. 113. Which of the following statements about collimation of the CT x-ray beam is FALSE?
    A. collimation of the beam occurs in the z-axis, thus affecting slice thickness
    B. increases in collimation increase the intensity of the primary beam
    C. collimation of the CT x-ray beam is used to limit the detection of scatter radiation
    D. collimation of the x-ray beam occurs both before and after the patient
    B. increases in collimation increase the intensity of the primary beam

    Collimation occurs as lead shutters close down upon the beam, limiting its projected area. Constructed of lead, the collimator shutters absorb portions of the primary beam, thereby reducing its intensity.
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  73. 114. Which of the following terms may be used to describe the quantity of radiation emitted from the CT x-ray tube toward the patient?
    A. constant mAs
    B. photon fluence
    C. effective mAs
    D. photon flux
    B. photon fluence

    Photon fluence may be described as the quantity of x-radiation passing through a unit area.
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  74. 115. Which of the following mathematical techniques is used exclusively for image reconstruction with helical CT scanners?
    A. convolution
    B. back-projection
    C. interpolation
    D. iterative techniques
    C. interpolation

    Interpolation is a mathematical technique used in helical CT. In interpolation, approximations of information above and below a section level are made to overcome the fact that a complete revolution of tube and detectors was not performed for each image.
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  75. 116. Which of the following is the most common type of noise found in the CT image?
    A. electronic noise
    B. quantum noise
    C. filter noise
    D. artifactual noise
    B. quantum noise

    The most common cause of CT image noise is the fluctuation in the number of x-ray photons measured by the detectors. When a CT scanner attempts to reconstruct an image from an insufficient amount of transmitted radiation measurements, quantum noise occurs.
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  76. 117. A picture archival and communications system (PACS) is connected with imaging modalities and other peripheral devices on a computerized communication system called a:
    A. network
    B. radiology information system (RIS)
    C. hospital information system (HIS)
    D. web
    A. network

    A computer network is a communication system designed to facilitate the transfer of data between computers. A PACS works on a network, which connects each of the involved imaging modalities, viewing stations, printers, and so on.
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  77. 121. The major disadvantage of the back-projection method of image reconstruction is the appearance of the:
    A. star artifact
    B. Gibb phenomenon
    C. partial volume effect
    D. ring artifact
    A. star artifact

    The star artifact was an unwanted by-product of the back-projection method of image reconstruction used in older CT scanners. It is now removed by the process of convolution used in the modern reconstruction method known as filtered back-projection.
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  78. 122. The most effective method of reducing involuntary motion on a CT image is:
    A. immobilization
    B. thorough explanation of the exam to the patient
    C. physical restraints
    D. reduced scan times
    D. reduced scan times

    Involuntary motion is beyond control of the pt and includes peristalsis, cardiac contraction, and tremors. Many scanners offer segmenting or "half-scan" options whereby images may be reconstructed after a partial revolution of the tube-detector system. In the case of digestive involuntary motion, glucagon administration is an additional option.
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  79. 123. Soft copies of CT images are stored on which of the following media:
    1. hard drives
    2. magnetic optical disk
    3. laser film
    A. 3 only
    B. 1 and 2 only
    C. 2 and 3 only
    D. 1 and 3 only
    B. 1 and 2 only

    Storage of CT images in digital file format is referred to as soft copies. Hard copies of CT images are those stored on laser film.
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  80. 124. The process of displaying CT images in a different orientation from the one used in the original reconstruction process is called:
    A. multiplanar reformation
    B. retropective reconstruction
    C. prospective reconstruction
    D. multisegment reconstruction
    A. multiplanar reformation

    Multiplanar reformation (MPR) describes the process of displaying CT images in a different orientation from the one used in the original reconstruction process. Unlike retrospective reconstruction, reformation does not change the makeup of the image voxels. Reformation merely alters the viewing perspective of the images to a different anatomic plane.
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  81. 125. The process of gray-scale mapping of the CT image may be referred to as:
    A. windowing
    B. prospective reconstruction
    C. retrospective reconstruction
    D. analog-to-digital conversion
    A. windowing

    Windowing is used to describe the process of gray-scale mapping the CT image, during which the display system assigns a shade of gray to an individual pixel on the basis of its CT number (HU).
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  82. 126. In the formula used to calculate the linear attenuation coefficient, I=I0e-μx, the symbol I0 identifies:
    A. transmitted intensity
    B. incident intensity
    C. absorber thickness
    D. Euler constant
    B. incident intensity

    The Lambert-Beer law, I=I0e-μx is used to calculate the attenuation coefficient of a volume of material. The symbol "I0" represents the intensity of the radiation incident upon the tissue being imaged. It is compared with the intensity of the radiation passing through the tissue (I) during the calculation of the linear attenuation coefficient.
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  83. 127. First generation CT scanners possess which of the following characteristics?
    A. nutating detector array
    B. silver halide detectors
    C. pencil thin x-ray beam
    D. rotate-rotate geometry
    C. pencil thin x-ray beam

    The x-ray beam of a 1st generation CT scanner was highly collimated to the size of a single detector. It was often referred to as a "pencil beam"
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  84. 128. The intensity of the x-ray beam after it passes through an object to a detector is called the:
    A. primary beam
    B. incident intensity
    C. ray
    D. transmitted intensity
    D. transmitted intensity

    The transmitted intensity is the amount of energy that passes through the pt onto a detector.
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  85. 129. An accurate, modern CT scanner possesses a spatial resolution up to:
    A. 10 lp/mm
    B. 10 lp/cm
    C. 25 lp/cm
    D. 25 lp/mm
    C. 25 lp/cm

    The limiting resolution of a modern CT scanner is approx. 25 lp/cm. This resolution varies greatly with scan factors and is considerably less than that of projection radiography.
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  86. 130. A high-resolution comb is utilized by an MSCT detector array in an effort to reduce:
    A. scatter radiation
    B. high spatial frequency signal
    C. patient radiation dose
    D. low spatial frequency signal
    A. scatter radiation

    Post-patient collimation occurs through a high-resolution comb placed over the detector array. Functioning like a grid, it removes unwanted scatter radiation and off-axis photons that result from the more divergent nature of the MSCT beam.
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  87. 131. The distance between the centers of two adjacent reconstructed CT images is termed the:
    A. interpolation edge
    B. sampling rate
    C. section interval
    D. section width
    C. section interval

    Section interval describes the spacing between two adjacent CT images. It is measured as the distance between the center of one section and the center of the adjacent section.
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  88. 132. The maximum number of simultaneous sections an MSCT system can acquire per gantry rotation is controlled by the number of:
    A. X-ray tubes
    B. detector rows
    C. data channels
    D. focal spots
    C. data channels

    The number of data channels controls the number of sections the scanner can simultaneously acquire with each gantry rotation. For example, a 4-slice MSCT system has 16 1.25 mm detectors in its array. However, with only 4 data channels, the maximum number of sections that may be reconstructed from each gantry rotation is 4. The system combines transmission information from the individual detectors through its 4 data channels, resulting in the acquisition of 4 sections per gantry rotation.
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  89. 133. Matrix size describes which of the following?
    A. number of pixels used to display image
    B. the number of data channels available
    C. relationship between the field of view and the algorithm
    D. aperature size used during data acquisition
    A. number of pixels used to display image

    Consisting of an arrangement of pixels in rows and columns, the matrix is used to organize the attenuation information from the anatomic section into a digital image. The size of the matrix is given as the number of pixels across multiplied by the number of pixels down.
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  90. 135. An ROI measurement with an average CT number of zero is:
    A. blood
    B. air
    C. fat
    D. water
    D. water

    The CT number for water has an average value of zero.
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  91. 136. The implementation of corrective actions to improve any identified performance inadequacies of the CT system is referred to as:
    A. uniformity
    B. linearity
    C. quality control
    D. quality assurance
    C. quality control

    Quality control refers to the implementation of corrective actions to improve any identified performance inadequacies of the CT system found through quality assurance procedures.
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  92. 137. The major disadvantage of the fan- or cone-shaped x-ray beams used in modern CT units in comparison with the "pencil-thin" beams of older units is:
    A. greater patient radiation dose
    B. decreased transmission measurements
    C. excess tube wear
    D. increased transmission measurements
    A. greater patient radiation dose

    The use of a fan- or cone-shaped x-ray beam during CT increases the total volume of tissue irradiated, thereby increasing the amount of scatter radiation produced. This change results in a significantly higher pt radiation dose than the "pencil beam" radiation used in older CT scanners.
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  93. 138. When choosing a scan field of view(SFOV), the CT tech is controlling the:
    1. diameter of data acquisition
    2. number of activated detectors within the array
    3. correction factors for the specfic area of anatomic interest
    A. 1 and 2 only
    B. 2 only
    C. 1 and 3 only
    D. 1, 2, and 3
    D. 1, 2, and 3

    Each CT scanner has several choices for SFOV. The choice made by the tech activates a certain percentage of the detector array so that information is acquired from a circular portion of the anatomic section. Built into the SFOV selection are additional correction factors used to process different types of tissue. For example, a CT scanner may have a specific selection for scans of the head, which attempts to limit the artifact occuring at the delineation of bone from brain tissue.
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  94. 139. As the attenuation of a volume of tissue decreases, the transmitted intensity of a CT x-ray beam:
    A. remains unchanged
    B. increases
    C. decreases
    D. increases to a peak value and then rapidly decreases
    B. increases

    The transmitted intensity of a CT x-ray beam and the attenuation of the tissue imaged are inversely related. As the tissue begins to attenuate less radiation, the transmitted intensity of the beam increases. Areas of less dense tissue allow more radiation to pass onto the detectors, and vice versa.
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  95. 140. Which of the following parameters or factors is improved by the selection of a smaller x-ray tube filament?
    A. scan time
    B. signal-to-noise ratio
    C. heat rating
    D. spatial resolution
    D. spatial resolution

    Smaller focal spots improve the geometric efficiency of the x-ray beam, leading to greater spatial resolution.
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  96. 141. The geometric efficiency of a CT detector is influenced primarily by the:
    A. amount of interspace material between detectors
    B. atomic number of the detector material
    C. size of the detector material
    D. size of the tube filament
    A. amount of interspace material between detectors

    The geometric efficiency of a CT detector is influenced primarily by the amount of interspace materials necessary between adjacent detectors. Although valuable in limiting interference (cross talk) between adjacent detectors, the interspace material reduces geometric efficiency by absorbing transmitted x-ray energy.
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  97. 142. Which of the following factors may affect the attenuation of an object during CT data acquisition?
    A. mA
    B. kVp
    C. beam pitch
    D. algorithm
    B. kVp

    The degree of attenuation depends on multiple factors, including the x-ray energy and the atomic structure and density of the exposed tissue.
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  98. 143. An image that is reconstructed a second time with some change in technical factor is said to be:
    A. reformatted
    B. post-processed
    C. retrospective
    D. reiterated
    C. retrospective

    Retrospective reconstruction occurs when an image is reconstructed a second time with an adjustment in a technical factor. The scan data or "raw" data are used to reconstruct the image with a different display matrix, display field of view, algorithm, and so on.
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  99. 144. The Feldkamp-Davis-Kress (FDK) algorithm may be applied to MSCT acquisition data to overcome image artifacts from:
    A. partial volume averaging
    B. beam divergence
    C. patient motion
    D. beam hardening
    B. beam divergence

    The beam divergence inherent to the cone beam geometry of MSCT can cause difficulty during the image reconstruction process. Specific cone beam algorithms such as the Feldkamp-Davis-Kress (FDK) and advanced single-slice rebinning (ASSR) algorithms attempt to overcome the issues resulting from the divergent path of the x-ray beam from tube to the widened detector array.
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  100. 145. MSCT systems are typically capable of differeniating adjacent objects with attenuation differences as small as:
    A. 10 HU
    B. 3 HU
    C. 25 HU
    D. 60 HU
    B. 3 HU

    Each 1.0% difference in contrast between adjacent objects amounts to a difference in pixel value of approx. 10 HU. MSCT systems are typically capable of differentiating adjacent objects with attenuation differences as small as 3 HU.
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  101. 146. The ability of an MSCT system to freeze motion and provide an image free of blurring is called:
    A. longitudinal spatial resolution
    B. contrast resolution
    C. temporal resolution
    D. in-plane spatial resolution
    C. temporal resolution

    The stop-motion capability of a CT system is referred to as temporal resolution. Temporal resolution quantifies the CT system's ability to freeze motion and provide an image free of blurring.
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  102. 147. Ring artifacts on the CT image are associated with which of the following tube-detector geometries?
    A. rotate-rotate
    B. translate-rotate
    C. rotate-stationary
    D. rotate-nutate
    A. rotate-rotate

    Ring artifacts are associated with the use of 3rd generation CT scanners. Both the x-ray tube and the detector array rotate around the pt with 3rd gen scanners. A malfunctioning detector or series of detectors in a 3rd gen CT scanner causes a ring artifact to appear on the image as a result of the rotational nature of the detector array.
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  103. 148. What is the maximum beam collimation for an MSCT system with 16 rows of 1.25mm detectors?
    A. 5.0mm
    B. 20.0mm
    C. 40.0mm
    D. 2.5mm
    B. 20.0 mm

    16 rows x 1.25mm= 20.0mm
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  104. 149. The polyenergetic x-ray beam emitted from a CT x-ray tube is susceptible to artifacts due to the phenomenom known as:
    A. kerma
    B. density bloom
    C. partial volume
    D. beam hardening
    D. beam hardening

    The polyenergetic CT x-ray beam consists of photons of varying energy. As the beam traverses the pt, low-energy photons are absorbed first, increasing the average intensity of the beam as it travels along its path. This change, referred to as beam hardening, can have an artifactual result on the CT image.
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  105. 150. In an MSCT system, which of the following technical parameters determines the reconstructed section width?
    A. beam collimation
    B. number of data channels
    C. detector collimation
    D. detector pitch
    C. detector collimation

    With MSCT, detector collimation determines the width of the reconstructed section. By electronically adjusting the detector dimension, the operator can control the width of the x-ray beam contributing to a reconstructed section. Beam collimation no longer directly controls section width.
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  106. 151. Daily air or water calibration of the CT system is performed to evaluate which of the following components of image quality?
    A. uniformity
    B. linearity
    C. temporal resolution
    D. contrast resolution
    B. linearity

    The accuracy between calculated CT numbers and their respective linear attenuation coefficients is termed linearity. Daily system calibration and routine vendor maintenance procedures work to establish and maintain CT system linearity.
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  107. 152. The reduction in intensity of an x-ray beam as it interacts with matter is called:
    A. transmission
    B. attenuation
    C. luminescence
    D. scatter
    B. attenuation

    Attenuation is the reduction in intensity of an x-ray beam as it interacts with matter. Several interactions are responsible for the attenuation of primary radiation, including Compton scatter and photoelectric effect. Each of these interactions reduces the energy and/or number of the x-ray photons in a primary beam.
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  108. 153. Pixels whose average attenuation coefficients are less than the coefficient of water have which of the following types of CT number values?
    A. high positive
    B. negative
    C. extremely large
    D. high contrast
    B. negative

    When a formula comparing the attenuation coefficient of tissue with that of water is used, materials whose coefficients are less than that of water are assigned negative CT numbers.
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  109. 154. Which of the following actions would serve to magnify the CT image on the display monitor?
    A. increase display field of view
    B. decrease display field of view
    C. decrease matrix size
    D. increase scan field of view
    B. decrease display field of view

    Referred to as targeting, decreasing the display field of view (DFOV) causes an increase in the image size on the monitor. The DFOV controls te amount of scanned information to be displayed on the matrix. If a small portion of information is to be displayed on the entire matrix, it will appear larger to the viewer.
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  110. 155. The bit depth of a digital imaging system defines the number of information bits contained within each:
    A. axial image
    B. pixel
    C. matrix
    D. multiplanar reformation (MPR)
    B. pixel

    The bit depth of a digital imaging system defines the number of information bits contained within each pixel. This parameter ultimately controls the total range of CT values that may be assigned to a given pixel. For example, a bit depth of 12 results in 4096 possible CT values (212 = 4096).
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  111. 156. The technical factor(s) necessary for the acquistion of an isotropic data set is/are:
    1. thin detector collimation
    2. high mA setting
    3. small DFOV
    A. 1 only
    B. 2 and 3 only
    C. 1, 2, and 3
    D. 1 and 3 only
    D. 1 and 3 only

    Isotropic voxels have equal dimensions along the x-, y-, and z-axes. Use of a thin reconstructed section width and small DFOV minimizes each voxel dimension.
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  112. 160. In multislice CT (MSCT), the combined thicknesses of all of the sections simultaneously acquired with each gantry rotation are called the:
    A. detector pitch
    B. detector configuration
    C. beam pitch
    D. total collimation
    D. total collimation

    Total collimation equals the combined thickness of all the sections that are simultaneously acquired with each gantry rotation. For example, a given MSCT system has an array of 64 detectors, each 0.625 mm wide. If the beam is collimated to expose the entire array, the total collimation for the acquisition is equal to 0.625 mm x 64, or 40 mm.
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  113. 161. MSCT systems typically employ which of the following types of detectors?
    A. gas ionization
    B. tungsten ring
    C. charged-couple device (CCD)
    D. solid state scintillation
    D. solid state scintillation

    All modern MSCT systems utilize solid-state detectors consisting primarily of a scintillating crystal material. Solid-state detectors are preferred for MSCT because of their ability to accurately record incident x-ray energy from any angle. This flexibility is important when one considers the widened cone beam geometry inherent to MSCT systems.
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  114. 162. Which of the following technical adjustments may be employed to reduce step artifact in a multiplanar reformation CT image?
    1. acquisition of an isotropic data set
    2. overlapping section increment
    3. increase in effective mAs
    A. 1 and 2 only
    B. 1 only
    C. 1, 2, and 3
    D. 2 and 3 only
    A. 1 and 2 only

    In modern MSCT systems, the highest-quality 3D and multiplanar reformation (MPR) images are obtained with the acquisition of an isotropic or near-isotropic data set. The other equally important piece is an overlapping data set, for which the reconstruction interval is less than the section width.
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  115. 163. Which of the following is a manifestation of the partial volume artifact?
    A. aliasing
    B. streaking
    C. Hounsfield Bar
    D. cupping
    D. cupping

    The cupping artifact that occurs at the superior portion of the skull is another form of partial volume artifact. The dense skull table averages with the low-attenuating brain tissue, causing an artifact by which the brain parenchyma may appear abnormally dense.
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  116. 164. During volumetric CT acquisition, the slice sensitivity profile (SSP) graphically represents the:
    A. beam width
    B. effective section width
    C. detector collimation
    D. dose profile
    B. effective section width

    The effective section width corresponds to the SSP of the reconstructed section in consideration of the widening that occurs during helical data acquisition.
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  117. 165. An increase in the sampling rate during CT data acquisition corresponds to an increase in:
    A. matrix size
    B. views per rotation
    C. patient radiation dose
    D. image noise
    B. views per rotation

    The sampling rate may be quantified as views per rotation (VPR). As the sampling rate rises, the number of views per rotation (VPR) increases.
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