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49 Cards in this Set
- Front
- Back
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Indications of a Lung Scan
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PE, pre-surgical evaluation, and right to left cardiac shunt.
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Gold Standard for a definite diagnosis of PE =
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Pulmonary Angiography = expensive test, very invasive & time consuming
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Common route of diagnosing PE
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Ventilation- Perfusion Scan (V/Q) Lung scan, echocardiography, venous ultra sound, electrocardiogram, chest roentgenography and lab test.
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Chest Radiography
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Not an accurate means, it is needed for further information such as pneumonia, congestive heart failure, cause of dyspnea, symptoms that might suggest a PE.
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The CXR should be compared to a V-Q lung scan. Using high quality PA and lateral film
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Most doctors want this X-Ray and no older then CXR that are 1 day old are acceptable.
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Perfusion Imaging
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Blood from the right ventricle
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Radiopharmaceutical
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Tc-99m MAA 2-4 Mci (1 Mci if performed prior or first to ventilation study)
- # of particles should be in the range of 200,000 to 700,000 - MMA particles will settle in vial, agitate before drawing up dose. |
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The introduction of MAA will induce microembolization
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of the radio-labeled particles in the pulmonary arterioles.
- The # of particles which impact in a particular volume of the lung is proportional to the pulmonary arterial blood flow to that region. |
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It is a visual representation of the regional distribution of pulmonary
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blood flow at the time of injection.
- Only in lungs for 3 hours |
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Tc99m MAA
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Withdraw aseptically using an 18-21 g needle.
- If blood is drawn into the syringe, any unnecessary delay prior to injection may lead to blood clot formation in syringe. Do not back flush/draw back on needle. - Patient supine -Deep breaths while injecting |
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Views: 4-8 views
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anterior, posterior, right
and left lateral, right and left posterior oblique, right and left anterior oblique. |
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Image for 500-1000k counts, except for
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lateral.
Image first lateral at 500,000 check time and image other lateral for same amount of time. |
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Image for maximum 500,00 counts all views.
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Lateral Shine through in 1/3 of all laterals.
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Normal Scan
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No perfusion
defects, perfusion exactly outlines the shape of the lungs as seen on chest radiographs. |
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As long as the perfusion image
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normal the ventilation
and/or CXR may be abnormal. |
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Radioactive compound is injected into the vein, travels to lung tissues in blood vessels.
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PE is a blood clot in a pulmonary artery, no injected material won't reach a specific region of the lung.
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Mismatch of inhaled and injected compounds on the lung scan =
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PE
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Perfusion Scan
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Blood Flow to lung
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Ventilation Imaging
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Direct comparison to perfusion imaging.
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Aerosol
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Tc99m DTPA (diethylenetriamine-pentaacectic acid)
25-35 mCi in a nebulizer, patient receives approximately 1 mCi. |
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Inhalation in upright or supine position. Utilizes small particles rather than a gas. Patient should breath tidally for 5-7 minutes to obtain 130-180k cpm. To obtain uniform apex-to-base images the
study should be performed with the patient in the supine position. |
Multiple projections possible.
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Xenon-133
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(80 keV 5.2 days T½) gas: single breath,
equilibrium (3-6 mins), washout images – provide for a more complete characterization of ventilation and a more sensitive test for obstructive airway disease. |
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Xenon ( Image Room at negative Pressure)
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Position upright in front of camera (supine is
acceptable). Posterior or best view if following perfusion. Bacteria filter used to trap exhaled xenon. 5-20 mCi administered. The ventilation apparatus includes a tightly sealed mask or mouthpiece, tubing with intake and exhaust valves, a spirometer and a shielded charcoal filter. |
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Xe Views
Single Breadth |
, hold for 10 - 20 seconds for a static image
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Washout
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serial images 30-60 seconds images
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Breadth hold
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Equilibrium- washout
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If Perfusion first, then
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1-15 mCi vial of Xe, 5 day half life
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Dual head camera does allow imaging anterior.
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but apparatus can be in the way.
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Xenon imaged 1st or second?!?!
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Depends on hospital
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All three steps of a Pulmonex II Xenon study
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(start up, equilibrium imaging and washout) are
controlled by a single valve handle on the front panel |
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Views: Single (first) breath (breath hold)
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100,000 counts or 10 - 15 seconds obtained at administration of xenon gas.
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Equilibrium images while patient breathes into a closed
spirometer system for three views at 75 seconds each. |
Radiopharmaceutical distribution corresponding to the aerated
lung volume. |
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Washout images while patient breaths ambient air three images
at 45 seconds. |
Washout from normal lungs show rapid and
symmetrical clearance, usually within 90 seconds. |
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Image in posterior, although alternating oblique views may be
obtained for equilibrium and washout phases. |
Oblique views are
obtained for better visualization of abnormal lung volume and xenon retention with respect to their anterior and posterior locations. |
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The right lung is bigger then the
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left lung!
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Posterior View
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Looking at screen!
Right Lung will be on the right and will be bigger the the left lung |
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Anterior View
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Looking at the screen!
Right lung will be on the left (bigger) then the left lung which is on the right! |
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Left lung has more of a defined
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crest shape
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Xenon Study
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During the washout; their was a spot retention during the wash out = air way problem!
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Perfusion Study has
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6 views
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Washout is only with
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Xenon
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Perfusion
abnormalities which involve an entire lung or an entire lobe only should lower the suspicion of pulmonary embolism. Pulmonary embolism which could cause that extensive of an abnormality should be bilateral. |
Unilateral extensive
perfusion abnormality is much more commonly seen with compression of a pulmonary artery by fibrosing mediastinitis or by a lung cancer or other tumor. |
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troponin
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If present in the blood stream, evidence almost 100% of minor heart attack
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Slide 12 of reparatory 3 is a perfect example of where the ventilation study showed a normal wash in and washout
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Perfusion showed half of the left lung missing and small part of the right lung missing.
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Extensive acute pulmonary
embolism |
are seen within both lungs. PE are of this severity are not seen in just 1 lung!
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A Negative or Good Ventilation study:
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Xe-133 ventilation
images show a uniform distribution of activity on single-breath and washin images. There is minimal abnormal Xe-133 retention in the left lung during the washout phase. CT was performed the same day as the V/Q study utilizing the pulmonary embolism protocol with i.v. contrast. Extensive acute pulmonary embolism are seen within both lungs. |
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A Positive or Bad Perfusion study:
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images show absent
perfusion in the left lung except the apical posterior segment of the left upper lobe. There is also absence of perfusion in the right posterior basal segment. There is decreased perfusion in the anterior basal segment of the right lower lobe and the anterior segment of the right upper lobe. |
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decreased perfusion throughout left lung and wedge shaped defects in the right lung. Suspicious for emboli since these areas ventilate normally.
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Left Lung absence of ventilation raises possibility of pulmonary mass.
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Images demonstrate a single large mis-
matched segmental perfusion defect in the region of the anterior segment of the left lower lobe. |
Although suspicious for pulmonary embolism, this constitutes an intermediate probability for embolism
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