Free Computed Tomography Practice Test

1. Which CT Procedure requires Prothrombin Time (PT) and Partial Thromboplastin Time (PTT) laboratory results prior to starting the procedure?

a. CT abdomen and pelvis with IV contrast
b. CTA PE chest
c. CT guided liver biopsy
d. CT soft tissue neck with IV contrast

2. What type of contrast is often used to enhance CT images of the large intestines and the pelvic organs?

a. Oral barium sulfate
b. Rectal contrast
c. Intrathecal contrast
d. Oral water soluble prep

3. What adrenal pathology may precipitate a hypertensive crisis if IV contrast is utilized?

a. Multiple myeloma
b. Diabetes
c. Pheochromocytoma
d. Renal insufficiency

4. What process reduces the longest wave length photons creating a more monochromatic beam and reducing patient radiation dose?

a. Filtration
b. Detector collimation
c. Slip rings
d. None of the above

5. The development of what electromechanical device consisting of circular electrical conductive rings and brushes allowed for helical scanning capabilities?

a. Amplifier
b. Array processor
c. Electron gun
d. Slip rings

6. What is the atomic number of Tungsten?

a. 74
b. 128
c. 62
d. 80

7. Bolus timing for Soft Tissue Neck CT's can be difficult due to many different structures enhancing at varied times. What contrast injection technique helps address the contradictory timing goals for imaging the neck?

a. Split bolus
b. Venous and arterial scans
c. Decrease injection rate
d. Increase delay times

8. What are the two phases of the Non-Equilibrium Phase utilized for Bi-Phasic studies of the pancreas and liver?

a. Hepatic arterial and portal venous
b. Bolus and equilibrium
c. Hepatic arterial and bolus
d. Portal venous and equilibrium

9. A routine liver abdomen CT is often scanned is one portal venous phase. What is an indication to scan the liver bi-phasic?

a. Hyper-vascular lesions
b. Hepatic vascular anatomy
c. Hemangiomas
d. All of the above

10. What is a typical mAs used in routine abdomen CT studies on an average sized patient?

a. 400-500 mAs
b. 25-100 mAs
c. 200-300 mAs
d. 100-150 mAs

Answers and Explanations

1. C: If the patient is having any kind of interventional procedure with CT Guidance, lab tests to determine the blood's ability to coagulate need to be done. The imaging staff need to be sure that the patient's blood has the correct clotting ability so the patient doesn't bleed internally. Such procedures may include all types of CT Guided Biopsies of any area, CT Guided drainages, and Ablations. If the PT or PTT are abnormal, the procedure may be cancelled.

2. B: Imaging locations vary by type and volume, but rectal contrast is often used to enhance the large intestines and pelvic organs. The rectal contrast helps to increase the sensitivity of the CT exam by outlining the large intestines, bladder, uterus, prostate and other organs. Rectal contrast is utilized for rectal pathology, or when a patient has lower GI symptoms but cannot tolerate oral prep. The contrast may be given using an enema tip attached to a bag or inserted manually using a tip and syringes.

3. C: Pheochromocytoma is a rare (usually benign) tumor of adrenal gland tissue. It results in the release of too much epinephrine and norepinephrine, hormones that control heart rate, metabolism, and blood pressure. An injection of IV Contrast material in patients with this condition can invoke a hypertensive crisis, so in most cases it is a contraindication to IV contrast injections. If it is approved by the Radiologist and imperative to the CT exam, careful blood pressure monitoring before during and after the CT contrast injection will be crucial.

4. A: Filtration helps a polychromatic beam become monochromatic. It reduces the longest wave lengths or lower energy wave lengths. Thus the radiation dose to the patient is reduced without a significant decrease in the measured signal. The remaining x-rays are less prone to beam hardening and artifacts caused by beam hardening.

5. D: The development of Slip Rings allow for helical scanning capability. They are housed within the gantry. First and second generation CT scanners had cables that needed to be unwound to continue scanning. Continuous rotation scanners apply to third and fourth generation CT scanners when the development of slip rings eliminated the start and stop process with cables. The circular electrical conductive rings and brushes transmit energy across a rotating surface. Slip rings allow for faster scan times and continuous (helical) acquisition.

6. A: Tungsten is often used for the anode target material. It produces a higher intensity x-ray beam. Tungsten has an atomic number of 74.

7. A: When imaging the neck, it is important to allow sufficient time after contrast injection for the pathologic tissue, lymph nodes, and mucosa to enhance (or not enhance). However, the vasculature needs to remain opacified so neoplastic and inflammatory processes are detected. If the scan is too long after the contrast injection, the vessels will no longer be opacified, but the other tissues will be enhanced. One injection technique utilized is called a split bolus. This technique splits the total contrast dose. The first dose is given (usually half of volume), then a 2 minute delay, followed by a second bolus, and then the patient is scanned. This allows time for the structures that are slower to enhance to be opacified, and the second injection allows the vessels to be opacified as well.

8. A: There are 3 phases of contrast enhancement: Bolus, Non-Equilibrium, and Equilibrium Phases. The first phase of enhancement is the Bolus phase. This is an optimal phase for CTAs. There is a significant density difference between the abdominal aorta and IVC. The second phase is the Non-Equilibrium phase. During this phase, the bolus disperses into the capillaries and then into the veins. The two phases of enhancement within this phase are the Hepatic Arterial (typically about 25 seconds post-contrast injection) and Portal Venous. The Non-Equilibrium phase provides the best differentiation of structures in soft tissue, like the liver and pancreas. The third phase is Equilibrium. During this phase, the concentration of contrast in the veins and arteries are similar and soft tissue differentiation becomes diminished.

9. D: Bi-Phasic liver scanning is usually done for any hyper vascular lesions or vascular hepatic anatomy. The liver receives about 25% of its blood supply from the hepatic artery and the remaining percentage of blood from the portal vein. There are several possible phases of contrast enhancement for the liver due to its dual blood supply. Different types of masses will enhance differently depending on that tumor's particular blood supply.

10. C: Depending on the scanner and the patient's habitus, the 200-300 mAs range is commonly utilized to image a routine abdomen CT. If the technologist selected thinner slices, the technique may need to be increased to reduce noise.

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Last Updated: 03/01/2017


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