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Flashcards in SP9:Respiratory System Scintigraphy Deck (48)
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1
Q

In general how many capillaries are blocked when a perfusion lung scan using 99mTc is performed?
(a)Fewer than 1 in 1000

(b) <0.1%
(c) Both (a) and (b)
(d) None of the above

A

(c) More than 80% of particles are removed on the first pass, blocking less than 1 in 1000 capillaries (<0.1%).

2
Q

Which of the following should be considered when injecting MAA?
(a)Patient position

(b) Blood in syringe
(c) Filters in intravenous lines
(d) All of the above

A

(d) When injecting a patient for a perfusion study, he or she should assume a supine position to ensure uniform distribution of particles. If blood is withdrawn into the syringe to confirm venous access, the radiopharmaceutical should be injected immediately as aggregated albumin and blood will form clots if left to sit. Intravenous lines or indwelling catheters that have filters should also be avoided to ensure that the particles reach the lung capillaries.

3
Q

The distribution of aerosol particles in the lungs is influenced by all of the following except:
(a)Turbulent air flow

(b) Amount of technetium added
(c) Rate of air flow
(d) Particle size

A

(b) The amount of technetium added to the kit will not affect the distribution of the aerosol particles, but only a small portion of the activity administered will actually be delivered to the patient. (It is estimated that of 25-35 mCi added to the nebulizer, a patient will receive 1-5 mCi. Therefore, it is important to do the ventilation scan first when planning both ventilation with aerosol and perfusion imaging.) The distribution of the particles may be altered if the patient has COPD (which impedes flow rate and causes turbulence) or if the aerosol particle size is large. Breathing the aerosol in the supine position will improve uniformity of distribution.

4
Q

During the equilibrium phase of a ventilation study, the patient:
(a)Inhales O2 and exhales 133Xe

(b) Inhales and exhales 133Xe
(c) Inhales 133Xe and exhales O2
(d) Inhales and exhales a mixture of 133Xe and O2

A

(d) The possibility to study the single breath, equilibrium, and washout phases is an advantage of 133Xe ventilation imaging. During the single breath phase, the patient exhales as completely as possible and then inhales 133Xe and holds it while an image is taken. During equilibrium, the patient breathes a mixture of 133Xe and oxygen. During the washout phase, fresh air is inhaled, and 133Xe is exhaled from the lungs.

5
Q

What best describes the normal blood flow to the lungs in a supine patient?
(a)Largely uniform

(b) Decreased flow to apices relative to bases
(c) Increased flow to upper lobes
(d) None of the above

A

(a) Patients should be injected for perfusion scans while supine to ensure uniform distribution to the lungs.

6
Q

What best describes the normal blood flow to the lungs in an erect patient?
(a)Largely uniform

(b) Decreased flow to apices relative to bases
(c) Increased flow to upper lobes
(d) None of the above

A

(b) Patients should be injected for perfusion scans while supine to ensure uniform distribution to the lungs.

7
Q

During a lung perfusion study, activity is noted in the head and in the area of the kidneys. This represents:
(a)Incorrect particle size

(b) Probable metastases
(c) Free technetium in the MAA
(d) Right to left shunt

A

(d) Normally the first capillary bed that the radiopharmaceutical encounters is in the lungs. If there is a right-to-left cardiac shunt, renal activity will be present, and the head should be imaged to confirm.

8
Q

What is the method of localization for a perfusion lung study?
(a)Sequestration

(b) Compartmental containment
(c) Active transport
(d) Capillary blockade

A

(d) The method is mechanical, based on the size of the particles in the radiopharmaceutical being too large to pass through the capillaries.

9
Q

Hot spots in the lungs on a perfusion study indicate:
(a)A perfusion defect.

(b) Turbulent air flow.
(c) Tracer injection into a supine patient.
(d) Improper particle size.
(e) Blood was withdrawn into injection syringe.

A

(e) Clots formed when albumin is allowed to contact sitting blood will create hot spots on perfusion images. This can happen if the radiopharmaceutical is not promptly injected after blood was withdrawn into the syringe.

10
Q

Which of the following describes the correct order in which air would pass through the respiratory anatomy?
(a)Trachea, right bronchus, right upper lobe bronchus, bronchioles, alveoli

(b) Trachea, left bronchus, left middle lob bronchus, bronchioles, alveoli
(c) Trachea, right bronchus, left lower lobe bronchus, bronchioles, alveoli
(d) Trachea, right bronchus, right lower lob bronchus, alveoli, bronchioles

A

(a) The trachea branches to two bronchi, which in turn branch into the bronchioles, the smallest of which branch into the alveoli.

11
Q

Which radiopharmaceutical will be most useful in detecting delayed washout in a patient with COPD?
(a)99mTc MAA

(b) 99mTc DTPA
(c) 81mKr
(d) 133Xe
(e) 99mTc MAG3

A

(d) The distribution of the particles may be altered if the patient has COPD (which impedes flow rate and causes turbulence)

12
Q

On lung ventilation images, activity is seen in the trachea and the stomach. This indicates:
(a)A right to left shunt

(b) Incorrect particle size
(c) That the study was performed with 99mTc DTPA
(d) That the study was performed with 133Xe
(e) A contaminated aerosol delivery system

A

(c) Activity in the central airway (often due to turbulent flow in patients with COPD) and stomach (from swallowed droplets) is often present on ventilation scans using aerosolized radiopharmaceuticals.

13
Q

Which of the following describes the correct procedure for injection of 99mTc MAA for a perfusion lung study?
(a)Injection should be made through an existing IV line if possible.

(b) Ensure that a minimum of 800,000 MAA particles are injected.
(c) Small amount of blood should be withdrawn into the syringe to ensure venous access before injection.
(d) Patient should be in the supine position.

A

(d) It is preferable to inject directly into the vein (if an indwelling catheter is used, it should be flushed following injection), and 800,000 particles are beyond the recommended dose. Supine positioning during injection increases the uniformity of particle distribution.

14
Q

Advantage of using 81mKr for ventilation lung scans include:
(a)Ability to perfectly match perfusion and ventilation positioning.

(b) Short half-life decreases exposure to technologist if patient removes mask.
(c) Ventilation and perfusion studies can be acquired simultaneously.
(d) All of the above.
(e) (a) and (b) only.

A

(d) 81mKr is useful for ventilation imaging. Its short half-life (13 s) and slightly higher photon energy allow the technologist to perform ventilation before or after perfusion imaging or, as a simultaneous scan, positioning once, imaging one isotope after another before moving the patient to the next position. The short half-life of 81mKr (13 s) may result in less exposure for technologist (in the event that the patient removes the ventilation mask) than with 133Xe.

15
Q

It is advisable to wait one-half hour following injection of 99mTc MAA before scanning to allow time for radiopharmaceutical clearance from the circulation.
(a)True

(b)False

A

(b) Since most particles will be cleared by the lung capillaries on the first pass, no wait is needed.

16
Q

Increased risk of pulmonary embolism is associated with:
(a)Smoking

(b) Use of oral contraceptives
(c) Recent surgery
(d) All of the above
(e) (a) and (c) only

A

(d) Risk factors for pulmonary embolism include oral contraceptive use or hormone therapy, prolonged inactivity (e.g., bed rest), recent surgery, and being postpartum. Some, but not all, sources cite smoking and obesity as risk factors.

17
Q

The number of particles injected during a perfusion lung scan should be decreased for:
(a)The elderly

(b) Those with a high risk of pulmonary embolus
(c) Patients with severe pulmonary hypertension
(d) Asthmatics

A

(c) Those who should be considered for lower particle doses are the young, those with pulmonary hypertension, or those with right-to-left shunting.

18
Q

Which dose would be the best choice to administer for a ventilation scan with 99mTc DTPA aerosol?
(a)1-2 mCi

(b) 3-5 mCi
(c) 8-15 mCi
(d) 20 mCi

A

(d) The dose administered with aerosolized 99mTc DTPA will be much higher than the dose the patient actually receives. The Society of Nuclear Medicine Guidelines state that of 25-35 mCi administered, the patient will receive only 0.5-1 mCi.

19
Q

Lung quantitation is often used to assist physicians in the diagnosis of pulmonary embolism.
(a)True

(b)False

A

(b) Lung quantitation may be used preoperatively in patients for whom lung resection is planned.

20
Q
A patient with lung cancer is scheduled to undergo resection of the right lower lobe. Given the counts obtained by ROI for each lung segment below, what percentage of respiratory function will be lost?
Right apical - 32,867
Right middle - 38,952
Right lower - 41,502
Left apical - 39,458
Left lower - 45,201
(a)17%

(b) 19%
(c) 21%
(d) 24%
(e) Cannot be determined from the information given

A

(c) The total counts are 197,980, Those from the right lower lobe are 41,502; this number is divided by total counts and multipled by 100 to find 20.9%.

21
Q

A perfusion lung scan shows a cold defect in the right base. If the ventilation study for the same patient is normal, what is the most probable explanation for the defect?
(a)COPD

(b) Pulmonary embolism
(c) Attenuation from the heart
(d) Pacemaker

A

(b) A mismatch, that is, a perfusion defect in the absence of a matching ventilation defect, often indicates pulmonary embolism.

22
Q

If a 5,000,000-particle MAA kit is reconstituted with 70 mCi of 99mTc in 4 ml, how many particles will be in 2 ml of the reconstituted kit?
(a)125,00

(b) 800,000
(c) 1,250,000
(d) 2,500,000

A

(d) The number of particles in 2 ml will be half of that in the kit of 4 ml.

23
Q

Regarding the reconstituted kit (5,000,000-particle MAA kit is reconstituted with 70 mCi of 99mTc in 4 ml), approximately how many particles will be administered to a patient who receives a 4 mCi dose?
(a)167,500

(b) 575,000
(c) 285,700
(d) 329,000

A

(c) The specific concentration is 17.5 mCi/ml. To administer 4 mCi, 0.23 ml would have to be injected (activity required/specific concentration). Since there are 1,250,000 particles per ml, the patient will receive 287,500 particles (particle concentration multiplied by ml injected).

24
Q

A patient with pulmonary embolism can have a negative chest X-ray.
(a)True

(b)False

A

(a) The chest x-ray may be normal or nonspecific in pulmonary embolism but may show other diseases that may aid interpretation of the lung scan. In any case, a recent chest x-ray should be performed before the scan.

25
Q

An MAA kit has an average of 8,000,000 particles and is reconstituted using 90 mCi of 99mTc in 5 ml at 8:00 a.m. Can the kit be used at 2 p.m. without injecting the patient with more than 800,000 particles?
(a)Yes

(b) No
(c) Cannot be determined from the information given

A

(a) At 2 p.m., the activity has decreased by one half-life, meaning that the activity is 45 mCi, and there are 8,000,000 particles in 5 ml provided no dose has been withdrawn from the vial. The concentration is now 1,600,000 particles per ml and 9 mCi per ml. If 0.4 ml is withdrawn into a syring, there will be 3.6 mCi and 640,000 particles in the dose.

26
Q

Over time, the number of particles per ml in a reconstituted MAA kit will change.
(a)True

(b)False

A

(b) The number of particles will not change because the particles and the volume remain constant, but the number of particles per mCi will change since the activity is decaying.

27
Q

A perfusion lung scan is being quantified. If counts obtained from an ROI around the left lung are 142,857 and the counts within the ROI about the right lung are 195,246, what percentage of perfusion is directed to the right lung?
(a)28%

(b) 42%
(c) 58%
(d) 65%
(e) 73%

A

(c) Total lung counts are 338,103. Right lung counts divided by total counts gives a percentage of 57.7%.

28
Q

The capillaries surrounding alveoli have a diameter of:
(a)0.3-1.0 um

(b) 0.4-2.0 um
(c) 7.0-10.0 um
(d) 5.0-10.0 mm
(e) 10.0-20.0 mm

A

(c) The capillaries surrounding the alveoli measure 0.7-10 um in adults. MAA particles measure 5-100 um, most are between 10 and 30 um. Particles greater than 10 um are trapped.

29
Q

When 99mTc MAA breaks down after injection into a patient, what happens to the particle fragments?
(a)They are excreted through the urine.

(b) They are excreted by the bowel.
(c) They are removed from the blood by the liver and spleen.
(d) They combine with other fragments in the bloodstream and are again stopped in the lung capillary bed.

A

(c) Particle fragments break down (some as soon as 30 min after injection), enter the bloodstream, and then are removed by the liver and spleen.

30
Q

Ventilation images are usually performed:
(a)With the patient supine so that perfusion is relatively uniform throughout the lungs

(b) Anteriorly, because more emboli occur anteriorly than posteriorly
(c) Posteriorly to reduce soft tissue attenuation and decrease distance to detector
(d) With the patient erect, so that perfusion is relatively uniform throughout the lungs

A

(c) Ventilation images can be performed with the patient erect or supine. Posterior images reduce patient to detector distance and avoid breast attenuation, particularly important with lower-energy photon like that from 133Xe.

31
Q

The use of a nebulizer is required with which of the following radiopharmaceuticals during lung imaging?
(a)99mTc DTPA

(b) 99mTc MAA
(c) 127Xe
(d) 133Xe
(e) All of the above except b

A

(a) A nebulizer is used to create a mist from a liquid and is used for ventilation scanning without gas.As kryton and xenon are true gases, a nebulizer is not needed.

32
Q

Perfusion and ventilation lung imaging removes the need for a chest X-ray.
(a)True

(b)False

A

(b) The chest x-ray may be normal or nonspecific in pulmonary embolism but may show other diseases that may aid interpretation of the lung scan. In any case, a recent chest x-ray should be performed before the scan.

33
Q

When performing a V/Q lung study with 99mTc MAA and 133Xe, which portion of the exam should be performed first?
(a)Ventilation.

(b) Perfusion.
(c) Either may be performed first.
(d) They may be performed simultaneously.

A

(a)133Xe has a lower photon energy (81 keV) than 99mTc (140 keV), and ventilation scans are usually performed first when using this gas.

34
Q

Trapping systems for 133Xe should be installed at the level of the _____, because 133Xe is _____ than air.
(a)Ceiling, heavier

(b) Ceiling, lighter
(c) Floor, heavier
(d) Floor, lighter

A

(c) Since 133Xe is heavier than air, it will drop and can be trapped by a floor system. In addition, ventilation scans should be performed in a room at negative pressure to surrounding areas.

35
Q

Stomach visualization on a ventilation scan performed using 99mTc DTPA aerosol indicates:
(a)There was turbulent air flow.

(b) The nebulizer is not functioning properly,
(c) The patient is a smoker.
(d) The patient swallowed some of the radiopharmaceutical.
(e) The patient has a right to left cardiac shunt.

A

(d) The stomach is often seen on aerosol lung scans for this reason. Activity in the central airway (often due to turbulent flow in patients with COPD) and stomach (from swallowed droplets) is often present on ventilation scans using aerosolized radiopharmaceuticals.

36
Q

The radiopharmaceutical used for ventilation scanning with the highest administered dose is:
(a)133Xe gas

(b) 99mTc DTPA aerosol
(c) 127Xe gas
(d) 81mKr
(e) 99mTc MAA

A

(b) The dose administered with aerosolized 99mTc DTPA will be much higher than the dose the patient actually receives. The Society of Nuclear Medicine Guidelines state that of 25-35 mCi administered, the patient will receive only 0.5-1 mCi.

37
Q

Only half of the administered dose of 99mTc DTPA aerosol is delivered to the patient.
(a)True

(b)False

A

(b) Much less than half is delivered. For this reason, aerosol ventilation scans are usually performed before perfusion scans. The dose administered with aerosolized 99mTc DTPA will be much higher than the dose the patient actually receives. The Society of Nuclear Medicine Guidelines state that of 25-35 mCi administered, the patient will receive only 0.5-1 mCi.

38
Q

Patient education prior to a ventilation scan may:
(a)Improve image quality

(b) Relax the patient and thereby speed washout
(c) Reduce the radiation dose to the technologist
(d) All of the above
(e) (a) and (c) only

A

(e) A patient must understand the effect of cooperation on the quality of the exam and of the increased exposure to healthcare workers if the ventilation apparatus is removed prematurely.

39
Q

the liver may be seen in the washout phase of a ventilation study because:
(a)99mTc DTPA aerosol was swallowed and then entered the bloodstream via the stomach.

(b) 133Xe gas is fat soluble.
(c) Particle size is too small.
(d) Air flow is turbulent.

A

(b) Xenon is fat soluble and partially soluble in blood and often appears during the washout phase of the ventilation scan.

40
Q

An advantage of 127Xe over 133Xe is that:
(a)It has a shorter half-life.

(b) It is inexpensive.
(c) It can be used after a 99mTc MAA perfusion study.
(d) It requires no special trapping because of the short half-life.

A

(c) The ventilation can be performed after the perfusion scan because of the higher photon energy of 127Xe relative to 99mTc (203 keV vs. 140 keV), and, therefore, the ventilation scan may be canceled if the perfusion is negative. It has a 36-day half-life and is expensive and is therefore not often used.

41
Q

When used in conjunction with 99mTc, 81mKr can be used to perform ventilation imaging:
(a)Before

(b) During
(c) After
(d) All of the above

A

(d) 81mKr can be used at any time relative to 99mTc, but it is most efficient to do the scans in tandem.

42
Q

133Xe can be used to perform ventilation scans with a portable camera in the intensive care unit.
(a)True

(b)False

A

(b) Since 133Xe is heavier than air, it will drop and can be trapped by a floor system. In addition, ventilation scans should be performed in a room at negative pressure to surrounding areas. It is not likely that the safe conditions will be present in the ICU

43
Q

A V/Q scan can be used:
(a)To determine the likelihood of pulmonary embolism

(b) To evaluate resolution of pulmonary embolism
(c) To quantify differential pulmonary function before pulmonary surgery
(d) To evaluate cardiac shunts
(e) All of the above

A

(e) In addition, a V/Q scan can be used to evaluate hepatic pulmonary syndrome and lung transplants.

44
Q

When performing an aerosol 99mTc DTPA aerosol V/Q scan, which of the following is correct:
(a)99mTc DTPA aerosol ventilation imaging can be performed before or after perfusion imaging.

(b) The dose used for the ventilation imaging is much higher than the perfusion imaging.
(c) The dose delivered to the lungs of patient for the ventilation imaging is much higher than the perfusion imaging.
(d) The count rate of the second imaging should be three to four times the count rate of the first imaging.
(e) Both (b) and (d)
(f) Both (c) and (d)

A

(e) The dose used for ventilation imaging is about 30 mCi 99mTc DTPA, but only ~1 mCi is delivered to the lungs. 99mTc MAA dose is ~5 mCi and thus has to be performed after ventilation.

45
Q

When performing a 133Xe V/Q scan, which of the following is not correct:
(a)Perfusion scintigraphy can be performed first, and if normal, ventilation scintigraphy can be omitted.

(b) The biological half-life of the MAA in the lungs is approximately 1.5-3 h.
(c) 99mTc MAA particles may settle in the vial with times; thus, the vial should be agitated and the syringe should be inverted prior to injection.
(d) The number of MAA particles should no less than 500,000.

A

(d) In most cases, the number of particles should be in the range of 200,000-700,000 in adults, but for patients with pulmonary hypertension or right-to left shunting, the number may be reduced to 100,000-200,000 particles in adults. All other answers are correct.

46
Q

When performing a 99mTc DTPA aerosol V/Q scan, which of the following is not correct:
(a)An aerosol ventilation allows multiple projection imaging to match those obtained for perfusion imaging.

(b) Aerosol ventilation imaging can be performed at the bedside because no special requirement for radioactive gas exhaust.
(c) Aerosol ventilation imaging is not affected by turbulent flow in patients with COPD.
(d) SPECT images can be obtained.

A

(c) One of the major disadvantages of aerosol ventilation imaging is that aerosol deposition is altered by turbulent flow, causing central deposition and suboptimal imaging.

47
Q

Advantages of V/Q scan over CTA include the following except:
(a)Can be performed in patients with poor renal function

(b) Can be performed in patients with pregnancy
(c) Have more incidental findings to explain patient’s symptoms
(d) Lower radiation exposure

A

(c) In fact, CTA has more incidental finding to explain patient’s symptoms.

48
Q

When performing a Tc-99 m MAA lung perfusion scan to evaluate possible right to left shunting, which of the following is correct:
(a)Multiple planar images of the chest, with stomach and kidneys included.

(b) Multiple planar images of the chest, with thyroid included.
(c) Multiple planar images of the chest, with both kidneys and thyroid included.
(d) Images must include the brain.

A

(d) Tracer uptake in the thyroid, stomach, and kidneys could be due to free TcO4-