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NMTCB(CT) practice questions

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Question 1Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

For power-injected iodinated contrast in an adult CT study, which peripheral IV catheter size is generally considered the minimum acceptable?

  1. 26-gauge
  2. 24-gauge
  3. 22-gauge
  4. 20-gauge Correct answer.

Explanation

Power injectors deliver contrast at high flow rates and pressures, so a 20-gauge or larger catheter in a suitable peripheral vein is the accepted minimum; smaller catheters cannot reliably tolerate typical injection rates and carry a higher risk of extravasation.

Question 2Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

During a contrast-enhanced CT, the technologist observes swelling and pain at the injection site while contrast is still being delivered. What is the first action?

  1. Stop the injection immediately Correct answer.
  2. Apply a warm compress while finishing the injection
  3. Reduce the flow rate by half and continue the study
  4. Reposition the patient's arm and continue the injection

Explanation

Extravasation is managed first by halting the injection so no additional contrast enters the soft tissues; the site is then assessed and local measures and follow-up are arranged according to severity.

Question 3Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which combination of technical adjustments best reduces radiation dose for a pediatric chest CT while preserving diagnostic image quality?

  1. Remove beam-shaping filtration and lengthen rotation time
  2. Lower kVp with tube-current modulation and iterative reconstruction Correct answer.
  3. Increase mAs and reduce slice thickness
  4. Increase kVp and reduce pitch

Explanation

Lowering kVp from adult settings reduces dose and increases iodine contrast, while automatic tube-current modulation and iterative reconstruction offset the added noise so that much lower mAs values remain diagnostic.

Question 4Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A patient with an eGFR of 25 mL/min/1.73 m2 takes metformin and is scheduled for a contrast-enhanced CT. What is the recommended management?

  1. Discontinue metformin permanently before any contrast study
  2. Give the contrast and double the metformin dose the following day
  3. No change is needed because metformin does not interact with iodinated contrast
  4. Withhold metformin at the time of contrast and for 48 hours afterward Correct answer.

Explanation

When renal function is reduced, iodinated contrast can precipitate acute kidney injury and impair metformin clearance, risking lactic acidosis; guidelines advise withholding metformin at contrast administration and for 48 hours, then restarting once renal function is confirmed stable.

Question 5Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A pregnant patient requires a medically indicated CT of the abdomen and pelvis. Which statement about fetal risk is most accurate?

  1. The fetal dose from a single abdominal CT typically exceeds 500 mGy
  2. Any fetal exposure above 1 mGy warrants immediate termination counseling
  3. Fetal anomaly risk is not measurably increased at doses below about 50 mGy Correct answer.
  4. Fetal dose is independent of scanned anatomy and technique factors

Explanation

Epidemiologic data show no measurable increase in congenital anomalies or pregnancy loss at fetal doses below roughly 50 mGy, and typical abdominal CT fetal doses fall well below that level, so a medically indicated study should not be withheld.

Question 6Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A patient is prescribed oral prednisone at 13 hours, 7 hours, and 1 hour before a contrast-enhanced CT. Which additional agent is commonly given 1 hour before contrast?

  1. Diphenhydramine Correct answer.
  2. Atropine
  3. Glucagon
  4. Metoclopramide

Explanation

Standard corticosteroid premedication is paired with an H1-receptor antihistamine, typically diphenhydramine 50 mg orally 1 hour before contrast, to reduce the frequency and severity of allergic-like reactions.

Question 7Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Minutes after contrast injection, a patient develops stridor, hypotension, and diffuse urticaria. Which medication is the first-line treatment?

  1. Intramuscular epinephrine Correct answer.
  2. Intravenous furosemide
  3. Sublingual nitroglycerin
  4. Oral diphenhydramine

Explanation

Stridor, hypotension, and urticaria indicate a severe anaphylactoid reaction, for which intramuscular epinephrine into the anterolateral thigh is first-line therapy; antihistamines and corticosteroids are adjuncts that work too slowly to reverse bronchospasm or shock.

Question 8Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which CT dose descriptor represents the dose averaged over a single rotation and normalized to the pitch over the scanned volume?

  1. Size-specific dose estimate
  2. Dose-length product
  3. Volume CT dose index Correct answer.
  4. Cumulative effective dose

Explanation

CTDIvol is the weighted CT dose index divided by pitch, describing dose per unit volume for the acquisition; the dose-length product is then obtained by multiplying CTDIvol by the scanned length.

Question 9Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which instruction best prepares a cooperative adult patient for the breath-hold used in a routine chest CT?

  1. Exhale fully and hold at end expiration
  2. Hold the breath with the mouth open
  3. Take several rapid breaths immediately before holding
  4. Inhale fully and hold the breath without exhaling Correct answer.

Explanation

Chest CT is acquired at full inspiration, which maximizes air-filled lung volume and minimizes atelectasis; the patient is coached to take a full breath in and hold it without exhaling or breathing out.

Question 10Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Glucagon is sometimes given to reduce bowel peristalsis during abdominal CT. In which patient should it be avoided?

  1. A patient with chronic kidney disease
  2. A patient with type 2 diabetes mellitus
  3. A patient with mild hypertension
  4. A patient with pheochromocytoma Correct answer.

Explanation

Glucagon can stimulate catecholamine release from a pheochromocytoma and provoke a hypertensive crisis, so it is avoided in these patients; insulinoma is another contraindication because glucagon can precipitate hypoglycemia.

Question 11Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

In a patient without known kidney disease, which eGFR value is generally used as the threshold below which iodinated contrast is considered to increase the risk of contrast-associated acute kidney injury?

  1. 45 mL/min/1.73 m2
  2. 60 mL/min/1.73 m2
  3. 90 mL/min/1.73 m2
  4. 30 mL/min/1.73 m2 Correct answer.

Explanation

An eGFR below 30 mL/min/1.73 m2 identifies patients at increased risk for contrast-associated acute kidney injury and prompts a risk-benefit review and preventive measures such as hydration.

Question 12Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A breastfeeding patient asks whether she must interrupt breastfeeding after receiving IV iodinated contrast. What is the most appropriate response?

  1. She must discard pumped milk for 48 hours
  2. She must wean because contrast is excreted into milk at high levels
  3. She can continue breastfeeding without interruption Correct answer.
  4. She should pump and discard for 24 hours

Explanation

Iodinated contrast enters breast milk in very small amounts and is poorly absorbed by the infant's gastrointestinal tract, so current guidance supports continuing breastfeeding without interruption.

Question 13Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which intervention is best supported for reducing the risk of contrast-associated acute kidney injury in an at-risk patient scheduled for contrast-enhanced CT?

  1. Mannitol infusion during the scan
  2. Oral furosemide before the scan
  3. Intravenous isotonic saline hydration Correct answer.
  4. Use of a high-osmolar contrast agent

Explanation

Peri-procedural intravenous isotonic saline maintains renal perfusion and is the best-supported preventive measure; diuretics have not shown benefit and may worsen renal injury, and low- or iso-osmolar agents are preferred.

Question 14Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which site is preferred for power-injected contrast in a patient with a functioning left-arm hemodialysis arteriovenous fistula?

  1. A right antecubital vein Correct answer.
  2. The left basilic vein proximal to the fistula
  3. The fistula itself
  4. The left cephalic vein distal to the fistula

Explanation

A limb with a dialysis access should not be used for venipuncture or contrast injection because of the risk of thrombosis or injury to the fistula, so the contralateral arm is preferred.

Question 15Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

How does automatic exposure control reduce patient dose in CT?

  1. By shortening the scanned length to the visible anatomy
  2. By selecting a smoother reconstruction kernel
  3. By modulating tube current according to patient attenuation Correct answer.
  4. By increasing pitch automatically for every protocol

Explanation

Automatic exposure control estimates attenuation from the localizer and adjusts tube current along the scan to maintain a target noise level, lowering dose in less attenuating regions and in smaller patients.

Question 16Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

What does current guidance say about routine use of bismuth breast shields in chest CT?

  1. They should be applied to every female patient regardless of age
  2. They may reduce surface dose but can degrade images and are used selectively Correct answer.
  3. They are required by accreditation standards for all chest CT
  4. They eliminate internal scatter dose to the breast tissue

Explanation

Bismuth shields lower superficial breast dose but can create artifacts and, when exposure control is active, may actually raise tube output; guidelines therefore call for selective rather than routine use.

Question 17Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A CT technologist learns she is pregnant. What is the most appropriate action?

  1. Declare the pregnancy so work assignments and fetal dose monitoring can be arranged Correct answer.
  2. Wear a lead apron over the abdomen and continue without a dosimeter
  3. Stop working with any ionizing radiation immediately
  4. Avoid entering the scan room for any reason

Explanation

Declaring the pregnancy allows the facility to review workload, issue a fetal dosimeter, and keep occupational dose well below recommended limits while the technologist continues to work.

Question 18Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which set of findings most suggests a vasovagal reaction rather than an anaphylactoid reaction to contrast?

  1. Widespread urticaria with normal blood pressure
  2. Hypotension with bradycardia and no urticaria Correct answer.
  3. Hypotension with tachycardia and bronchospasm
  4. Laryngeal edema with inspiratory stridor

Explanation

Vasovagal reactions produce hypotension accompanied by bradycardia and typically lack urticaria or bronchospasm, whereas anaphylactoid reactions cause tachycardia, urticaria, and airway edema.

Question 19Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Why should the scanned range in CT be limited to the clinically indicated anatomy?

  1. It reduces the number of contrast phases required
  2. It shortens reconstruction time
  3. It lowers the effective mAs delivered per slice
  4. It reduces dose from overranging and from irradiating uninvolved tissue Correct answer.

Explanation

Tissue outside the reconstructed volume receives dose without contributing diagnostic information, and helical overranging at the beginning and end of the scan adds further dose, so the range should match the clinical question.

Question 20Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

What is the primary benefit of warming iodinated contrast to body temperature before power injection?

  1. It increases the iodine concentration
  2. It lowers viscosity and may reduce extravasation risk Correct answer.
  3. It prolongs the duration of enhancement
  4. It reduces the osmolality of the solution

Explanation

Warming lowers contrast viscosity, which reduces the pressure needed to achieve a given flow rate and may decrease the likelihood of extravasation; iodine concentration and osmolality are essentially unchanged.

Question 21Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Immediately before contrast administration, which verification is part of the pre-scan time-out?

  1. Confirmation of the patient's insurance coverage
  2. Confirmation of patient identity, ordered study, allergies, and renal function Correct answer.
  3. Confirmation of the patient's fasting blood glucose
  4. Confirmation of the number of prior CT examinations performed

Explanation

The pre-procedure time-out confirms patient identity, the correct study and protocol, allergy history, renal function, and pregnancy status before contrast is administered.

Question 22Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which patient most warrants continuous monitoring during moderate sedation for a CT-guided procedure?

  1. A 30-year-old with a sprained ankle
  2. A 45-year-old with well-controlled asthma
  3. A 55-year-old taking a statin
  4. A 70-year-old with obstructive sleep apnea Correct answer.

Explanation

Obstructive sleep apnea increases the risk of airway obstruction and respiratory depression under sedation, so continuous pulse oximetry, capnography where available, and close observation are required.

Question 23Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

What is the primary advantage of iterative reconstruction compared with filtered back projection in CT?

  1. It eliminates the need for tube-current modulation
  2. It removes the need for iodinated contrast
  3. It permits diagnostic image quality at a lower radiation dose Correct answer.
  4. It shortens the required breath-hold

Explanation

Iterative reconstruction reduces image noise through repeated modeling steps, so tube current and therefore dose can be lowered while maintaining acceptable image quality compared with filtered back projection.

Question 24Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which oral agent is preferred when a neutral, low-attenuation oral contrast is desired for CT enterography?

  1. Effervescent granules alone
  2. Dilute barium sulfate suspension
  3. Iodinated oral contrast
  4. Water Correct answer.

Explanation

Neutral agents such as water distend the bowel without high attenuation, allowing wall enhancement and mucosal detail to be evaluated; positive barium or iodine agents can obscure those findings.

Question 25Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A patient with a prior moderate allergic-like reaction to iodinated contrast has been premedicated and now develops urticaria during the injection. What is the most appropriate management?

  1. Premedication guarantees protection, so the injection should continue unchanged
  2. The reaction means the patient is now permanently ineligible for iodinated contrast
  3. Breakthrough reactions can occur, so the injection is stopped and the patient is assessed and treated Correct answer.
  4. Only the corticosteroid dose should be doubled and the injection continued

Explanation

Premedication reduces but does not eliminate allergic-like reactions; a breakthrough reaction is managed by stopping the injection, assessing the airway and vital signs, and treating according to the severity of the reaction.

Question 26Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Before IV iodinated contrast is administered, which practice best verifies patient identity?

  1. Checking that the requisition lists the referring physician
  2. Asking the patient to state the scheduled examination time
  3. Confirming the patient's room number with the transporter
  4. Matching the patient's name and date of birth to the order Correct answer.

Explanation

Two independent identifiers, typically the patient's name and date of birth, must be matched to the order and wristband before contrast. Room number, appointment time, and physician name are not unique patient identifiers.

Question 27Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

During power injection of contrast, the technologist sees swelling at the IV site. What is the first action?

  1. Increase the injection rate to clear the line
  2. Stop the injection immediately Correct answer.
  3. Flush the IV with 10 mL of saline
  4. Massage the site to disperse the contrast

Explanation

Swelling during power injection indicates extravasation, so the injection must be stopped at once to limit the volume delivered into the tissue. Massaging or flushing adds fluid and can worsen tissue injury.

Question 28Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A patient reports a shellfish allergy before a contrast-enhanced CT. How should this be managed?

  1. Premedicate with diphenhydramine and prednisone
  2. Switch to gadolinium-based contrast
  3. Cancel the CT because shellfish allergy is an absolute contraindication
  4. Proceed, because shellfish allergy does not predict iodinated contrast reaction Correct answer.

Explanation

Shellfish allergy reflects sensitivity to shellfish proteins, not to iodine, and it does not predict an allergic-like reaction to iodinated contrast. It is not an indication for premedication or cancellation.

Question 29Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A female patient of childbearing age is unsure whether she is pregnant before an abdominal CT. What is the most appropriate action?

  1. Assume she is not pregnant if she has no symptoms
  2. Ask about last menstrual period and follow facility pregnancy testing policy Correct answer.
  3. Refuse to scan until she brings a note from her obstetrician
  4. Proceed without discussion because CT uses no ionizing radiation

Explanation

Pregnancy status should be assessed through history, last menstrual period, and pregnancy testing according to facility policy. This supports informed decision-making and allows the protocol to be optimized if pregnancy is present.

Question 30Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A patient taking metformin has an eGFR of 45 mL/min/1.73 m2 and is scheduled for IV contrast CT. What is the recommended approach?

  1. Withhold metformin for 48 hours before and after contrast
  2. Give half the usual contrast volume
  3. Cancel the study because metformin is an absolute contraindication
  4. Proceed with contrast and continue metformin Correct answer.

Explanation

When eGFR is at least 30 mL/min/1.73 m2, metformin can generally be continued around iodinated contrast administration. Withholding is reserved for acute kidney injury or eGFR below 30.

Question 31Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which IV catheter is appropriate for power injection of iodinated contrast at 3 mL/sec?

  1. 24-gauge in a forearm vein
  2. 20-gauge in an antecubital vein Correct answer.
  3. 22-gauge in a hand vein
  4. Butterfly needle in the wrist

Explanation

Power injection requires a sturdy catheter, generally 20-gauge or larger, in a proximal vein such as the antecubital fossa. Small hand or wrist catheters carry a higher risk of extravasation at high flow rates.

Question 32Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which radiation dose quantity is expressed in millisieverts (mSv)?

  1. CT dose index volume (CTDIvol)
  2. Dose-length product (DLP)
  3. Effective dose Correct answer.
  4. Tube current-time product (mAs)

Explanation

Effective dose is expressed in millisieverts and reflects the overall stochastic risk from a partial-body exposure. CTDIvol is in mGy, DLP is in mGy·cm, and mAs is a tube output parameter.

Question 33Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which approach best reduces radiation dose for a small child undergoing chest CT?

  1. Increase the pitch to 0.5
  2. Use the same adult protocol for consistency
  3. Add bismuth shielding over the entire chest
  4. Adjust tube voltage and current to the child's size Correct answer.

Explanation

Size-based protocols lower tube voltage and current while preserving diagnostic image quality in children. Adult protocols overexpose small patients, and shielding does not reduce internal organ dose.

Question 34Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A 40 mL contrast extravasation occurred in the forearm. The site is swollen and painful. Which action is most appropriate after stopping the injection?

  1. Apply ice and massage the area
  2. Discharge the patient without instructions
  3. Place a tight tourniquet proximal to the site
  4. Elevate the arm and apply a warm compress Correct answer.

Explanation

After extravasation, elevate the affected extremity and apply a warm compress to promote absorption, then document and monitor the site. The patient should be given instructions to report worsening pain, swelling, or discoloration.

Question 35Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

What is the primary purpose of a saline flush immediately after contrast injection?

  1. To dilute the contrast that remains in the bladder
  2. To prevent nephrogenic systemic fibrosis from iodine
  3. To clear residual contrast from the tubing Correct answer.
  4. To chemically neutralize the contrast in the vein

Explanation

A saline flush clears the dead space of contrast from the tubing and vein, improving opacification and often allowing a lower contrast volume. It does not chemically neutralize contrast or prevent nephrogenic systemic fibrosis.

Question 36Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Why is a right antecubital IV often preferred for contrast-enhanced chest CT?

  1. The right arm has a lower risk of infiltration
  2. Contrast flows faster from the right arm
  3. It reduces streak artifact from dense contrast in the SVC Correct answer.
  4. Left-arm injections cannot be power injected

Explanation

Right-arm injection delivers a compact bolus through the superior vena cava with less mixing and streak artifact from the left brachiocephalic vein. Left-arm power injection is still possible when needed.

Question 37Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which finding is most typical of a late adverse reaction to iodinated contrast?

  1. A maculopapular rash appearing 6 hours to 2 days later Correct answer.
  2. Hypotension with bradycardia during injection
  3. Stridor within 5 minutes of injection
  4. Bronchospasm within 10 minutes

Explanation

Late contrast reactions are usually cutaneous, such as maculopapular rash or urticaria, and appear hours to days after administration. Immediate reactions occur within the first hour.

Question 38Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which practice helps prevent air embolism during power injection of contrast?

  1. Use a 24-gauge catheter to increase resistance
  2. Purge all air from the tubing before connecting Correct answer.
  3. Leave the syringe upright without priming
  4. Inject with the patient in a steep head-down position

Explanation

Careful priming and inspection of syringes and tubing removes air before it can enter the venous circulation. Patient position and catheter size do not reliably prevent air embolism.

Question 39Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

For moderate sedation during a CT-guided procedure, what is the recommended minimum fasting interval for clear liquids?

  1. 2 hours Correct answer.
  2. 30 minutes
  3. 6 hours
  4. 12 hours

Explanation

Standard sedation guidance recommends fasting from clear liquids for at least 2 hours before moderate sedation. A longer fast is generally recommended for light meals or fatty foods.

Question 40Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which element is essential for informed consent before contrast administration?

  1. The radiologist's years of experience
  2. Discussion of benefits, risks, and alternatives Correct answer.
  3. A guaranteed list of all possible side effects
  4. The cost of the contrast agent

Explanation

Informed consent requires disclosure of the benefits, risks, and alternatives, along with the patient's voluntary agreement. Cost and provider experience are not core consent elements.

Question 41Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which statement best describes the stochastic risk from a single diagnostic CT examination?

  1. The risk is certain and immediate
  2. The risk is small and increases with cumulative dose Correct answer.
  3. The risk is zero because CT uses nonionizing radiation
  4. The risk is high enough to contraindicate all CT in adults

Explanation

Stochastic effects such as cancer are probabilistic, with a small risk at diagnostic dose levels that increases with cumulative exposure. CT uses ionizing radiation, and medically indicated examinations are not generally contraindicated.

Question 42Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Before an FDG PET/CT, how long should a patient generally fast?

  1. At least 12 hours
  2. At least 4 to 6 hours Correct answer.
  3. At least 30 minutes
  4. No fasting is required

Explanation

Fasting for about 4 to 6 hours lowers blood glucose and insulin levels, improving tumor FDG uptake and reducing uptake in myocardium and skeletal muscle. Prolonged fasting beyond this is not routinely required.

Question 43Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A patient who is breastfeeding is scheduled for I-131 radioiodine therapy. What instruction is correct?

  1. Pump and discard for 24 hours, then resume
  2. Stop breastfeeding permanently before therapy Correct answer.
  3. Continue breastfeeding because I-131 does not enter breast milk
  4. Resume breastfeeding after 3 days

Explanation

I-131 concentrates in breast tissue and milk and can deliver significant dose to the infant thyroid. Breastfeeding must be discontinued permanently before radioiodine therapy.

Question 44Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which criterion is used to determine release of a patient after radioiodine therapy?

  1. Dose rate at 1 meter below the regulatory limit Correct answer.
  2. The patient's urine iodine concentration
  3. The total activity administered
  4. The patient's thyroid-stimulating hormone level

Explanation

Patient release after radioiodine therapy is based on measured exposure rate at 1 meter, typically below the regulatory limit, together with written safety instructions. Administered activity alone does not determine release.

Question 45Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which patient is at greatest risk of thyroid storm after iodinated contrast administration?

  1. A patient with uncontrolled hyperthyroidism Correct answer.
  2. A patient with a small goiter and normal thyroid function
  3. A patient with treated hypothyroidism
  4. A patient with a history of thyroidectomy

Explanation

An iodine load can precipitate thyroid storm in patients with uncontrolled hyperthyroidism. Contrast should be used only when necessary, with coordination and monitoring.

Question 46Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A CT abdomen/pelvis has a DLP of 500 mGy·cm. Using a conversion factor of 0.015 mSv/mGy·cm, what is the approximate effective dose?

  1. 7.5 mSv Correct answer.
  2. 75 mSv
  3. 500 mSv
  4. 0.075 mSv

Explanation

Effective dose is calculated as DLP multiplied by the conversion factor: 500 × 0.015 = 7.5 mSv. This is in the typical range for an abdominal CT examination.

Question 47Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A patient is found to be pregnant after being scheduled for I-131 therapy. What is the most appropriate action?

  1. Cancel therapy and consult radiation safety and the referring physician Correct answer.
  2. Proceed because the fetus is not at risk after 12 weeks
  3. Give therapy only if the patient signs a waiver
  4. Reduce the administered activity by half

Explanation

I-131 is contraindicated during pregnancy because the fetal thyroid concentrates iodine and can be permanently damaged. Therapy must be postponed or canceled, and the case should be reviewed with radiation safety and the referring clinician.

Question 48Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A pregnant patient requires an abdominal CT for suspected appendicitis. Which approach is most appropriate?

  1. Perform the CT without any dose optimization
  2. Perform the medically indicated CT with a dose-optimized protocol Correct answer.
  3. Delay until after delivery regardless of symptoms
  4. Refuse the CT because fetal risk is absolute

Explanation

Medically necessary CT should not be withheld solely because of pregnancy. The protocol should be optimized, the indication documented, and the risk-benefit discussion recorded.

Question 49Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

Which finding after contrast extravasation suggests compartment syndrome and requires urgent evaluation?

  1. A transient feeling of warmth
  2. Mild tenderness that resolves in 1 hour
  3. Severe pain, pallor, and decreased capillary refill Correct answer.
  4. A small area of erythema at the puncture site

Explanation

Severe pain out of proportion, pallor, paresthesia, and poor capillary refill suggest compartment syndrome, which requires urgent surgical evaluation. Minor tenderness or transient warmth is common and usually self-limited.

Question 50Patient Care, Safety, and Radiopharmaceutical/Contrast Considerations

A patient with a prior severe anaphylactoid reaction to iodinated contrast needs an emergent contrast-enhanced CT. What is the most appropriate action?

  1. Perform the CT with contrast and full resuscitation readiness Correct answer.
  2. Cancel the CT because prior severe reaction is an absolute contraindication
  3. Give contrast without monitoring to save time
  4. Premedicate with oral steroids and wait 4 hours before scanning

Explanation

In a life-threatening emergency, the diagnostic benefit may outweigh the risk of recurrent reaction. Contrast can be given with resuscitation equipment and personnel immediately available, and the event documented.