2. 2
Position of heart & lungs in thorax
Review of Respiratory System (1)
2
1
Cardiac notch
(cardiac silhouette)
3. 3
Lobes of the Lung
Review of Respiratory System (1)
Right, left lungs:
-apex, base
- lobes, segments
- cardiac impression
(Cardiac silhouette/ cardiac
notch)
11
7. 7
Airways
Review of Respiratory System (1)
- Larynx
- Trachea
- carina
- left, right
main bronchus
- Secondary bronchi
- Bronchioles
- alveoli
7
8. 8
Pulmonary Circulation
Review of Respiratory System (1)
Circulatory system:
superior/inferior vena cava, right atrium, right ventricle, pulmonary arteries,
lungs, pulmonary veins, left atrium, left ventricle, aorta
8
11. 11
Effect of Gravity on Pulmonary Circulation
• At or below level of heart (Zone 2 & Zone 3), arterial pressure in smaller
vessels greater so effect of gravity less noticeable
• Lung apices are above level
of heart, so not well perfused.
The reason is PA > Pa
resulting in collapsed small
vessels
As a general rule, blood flow
through a capillary in an alveoli
occurs only if: Pulmonary
artery pressure (Pa) > Alveloar
pressure (PA) & Pulmonary
vein pressure (Pv)
Upright
Thus Zone 1 is ventilated but not
perfused in compromised
individuals
Review of Respiratory System (1)
12
12. 12
Effect of Gravity on Pulmonary Circulation
– Apices of lung and heart about at same level, so effect of
gravity minimized
– Apical blood flow increases to equal to the blood flow to
bases of lung (Pa > Pv > PA)
– Clinical implication: Administer radiopharmaceutical used to
demonstrate lung perfusion with patient supine
Supine
Review of Respiratory System (1)
16. 16
Respiration
Includes processes of:
- ventilation
- gas exchange
- gas transport
- regulation of ventilation
- can be monitored with
nuclear medicine
techniques
The transport of O2 to and CO2 from cells
Review of Respiratory System (1)
15
17. 17
In a healthy lung, ventilation (V) and perfusion (Q) are
matched for efficient and optimal gas exchange (V/Q
ratio = 1)
The disparity between alveoli
surface area and volume of
blood in pulmonary capillaries
affected by gravity, regulatory
mechanisms, and disease
Review of Respiratory System (1)
16
18. 18
Patients on whom nuclear medicine lung examinations
are ordered may suffer from hypoxia.
• Hypoxia: insufficient
oxygen due to
decreased lung function
and/or decreased
oxygen supply to tissues
caused by decreased
blood flow or decreased
cardiac output
• Symptoms of hypoxia:
– Lethargy
– Dyspnea
– Cyanosis
Review of Respiratory System (1)
20. 20
Lung Perfusion Imaging
Clinical Indications
Radiopharmaceutical used
Dosage & Administration
Technique
The Normal Scan
Artifacts & Pitfalls
21. 21
Pulmonary Embolsm
• Rule out/follow-up
pulmonary embolism
–Most often a blood clot in
the lung resulting from a
thrombus in the veins of
the pelvis/leg
Clinical Indications
1
22. 22
• Evaluate COPD
(chronic obstructive pulmonary
disease)
Clinical Indications
- Any disease that causes decreased ability
of lungs to perform ventilatory function
- Symptoms:
persistent dyspnea on exertion
chronic cough
23. 23
• Evaluate lung perfusion
– In area of tumor
– To contralateral lung prior to surgery
• Other lung pathologies
Clinical Indications
26. 26
• None
• However, ask scheduling physician’s office
for any contraindications:
- Severe pulmonary hypertension
- In patients with ‘right to left’ cardiac
shunt reduce injected particles to
100,000
Patient preparation (before arrival)
Technique
27. 27
Patient preparations (after arrival)
1) ID patient; verify order; review clinical indication
for exam
2) Verify that patient has had a recent chest x-ray
- needed for interpretation of NM images
- rules out other possible causes of patient’s symptoms and
increases the specificity of perfusion lung imaging
- a normal chest x-ray increases the likelihood of PE
Technique
28. 28
Relevant Medical History
for Lung Imaging
• Symptoms of PE: chest pain
(location, duration), SOB,
cyanosis, hemoptysis, fever
• Medications/dietary
supplements/birth control
pills
• Surgery, esp recent
• Malignancies
• History of prior PE or
thrombophlebitis
• Chronic/acute lung disease
• Cardiac history: CHF,
pericarditis, cardiomegaly
• Lifestyle: smoking, physical
activity
• Previous medical imaging
• Lab results
• Pregnancy
Technique
29. 29
Administration
• Intravenous
• Administer with patient in supine position
• Invert syringe before injection
• Do not draw blood into syringe
• Inject slowly
• Have patient take a few deep breaths
Dosage & Administration
33. 33
Labeled Blood Clots
If blood and MAA particles remain in the syringe for extended periods,
radioactive clots may form and appear as “hot spots” on the images
Artifacts & Pitfalls
8
34. 34
Artifacts & Pitfalls
If the radiopharmaceutical is not administered
while the patient is in the supine position, the
apices of the lung may show decreased tracer
accumulation. This biodistribution could be
misleading to the physician interpreting the
images.
Patient posture
35. Lung Ventilation Imaging (3)
Clinical Indications
Radiopharmaceutical used
Dosage & Administration
Technique
The Normal Scan
Artifacts & Pitfalls
36. • Lung perfusion imaging is a sensitive,
but not specific technique.
• Its specificity is increased with
additional information from tests such
as chest x-ray and lung ventilation
imaging.
• Lung perfusion and ventilation imaging
are often performed together for this
reason.
Clinical Indications
38. A. The most common indication for lung scintigraphy is
to determine the likelihood of pulmonary embolism.
However, PE determination may not always require
the Ventilation component.
B. Less common indications
- Evaluate COPD (chronic obstructive pulmonary
disease)
- evaluation of lung transplantation
- preoperative evaluation
Clinical Indications
- Mostly same for both perfusion & ventilation studies
Do not let patients confuse our study with a ‘Pulmonary Function Test’!
39. Radiopharmaceutical used
Inert Gas
Gas Half-life Gamma Energy
Xenon-133 5.8 days 80 keV
Other less popular inert gas Ventilation agents : Xenon-127; Krypton – 81m
40. Radiopharmaceutical used
Inert Gas
Gas Half-life Gamma Energy
Xenon-133 5.8 days 80 keV
Aerosol (a suspension of fine solid or
liquid particles in a gas)
1) Tc-99m pentetate aerosols
(DTPA = diamine triethyl pentaacetic acid)
2) Technegas - ultrafine dispersion of Tc99m labeled carbon particles
(not marketed in the United States)
Other less popular inert gas Ventilation agents : Xenon-127; Krypton – 81m
41. Dosage
• Xe-133 gas : 5-20 mCi (adult dose)
• 99mTc-DTPA aerosol : The usual administered activity
of 99mTc DTPA is 25–35 mCi in the nebulizer, from
which the patient receives approximately 0.5–1.0mCi
to the lungs.
• Technegas : 10 to 15 mCi
Dosage & Administration
42. Administration
Dosage & Administration
• Both the gas and the aerosol are inhaled,
but each requires a different type of
administration equipment and a different
imaging protocol.
• It is important to elicit patient cooperation
by practicing with the equipment prior to
tracer administration.
43. Patient preparation
1) ID patient; verify physician’s order; review clinical
indication for exam; ascertain that recent chest x-
ray has been performed.
2) Explain procedure; obtain relevant medical history
(see medical history page for lung perfusion
imaging)
Technique
Before Arrival: None
After Arrival:
44. Relevant Medical History
for Lung Imaging
• Symptoms of PE: chest pain
(location, duration), SOB,
cyanosis, hemoptysis, fever
• Medications/dietary
supplements/birth control
pills
• Surgery, esp recent
• Malignancies
• History of prior PE or
thrombophlebitis
• Chronic/acute lung
disease
• Cardiac history: CHF,
pericarditis, cardiomegaly
• Lifestyle: smoking,
physical activity
• Previous medical imaging
• Lab results
• Pregnancy
45. Xenon-133 Gas Administration
Requires a closed breathing system
(xenon machine/xenon trap) to keep the
radioactive gas contained in the patient
or the xenon machine. Radioactive
xenon is a radiation hazard if it escapes
into the room.
Technique
Exam must be performed in a negatively pressurized room
to contain any xenon that may escape
46. Xenon Traps
Xenon traps utilizing
activated charcoal are
employed to prevent its
escape into the room
atmosphere and Xenon
trap monitors like the
ones show on the right
can monitor any escape.
Technique
47. Bacterial filters
Bacteria filters are used to reduce the possibility of cross contamination.
The single-use filter is placed in line between a delivery tube and
disposable mouthpiece or face mask. Electrostatically charged filter media
is 99.9% effective in bacteria/virus retention while maintaining low
breathing resistance. Two filters can be piggy-backed together for potential
high-risk studies.
Technique
48. Face Mask
• The syringe luer locks tightly to
the direct dose tube, away from
the patient’s face.
• The one-way valve prevents
the gas from reversing through the
mask luer connector, allowing the
technologist to disconnect
immediately after injecting.
Technique
49. CO2 & Moisture Absorbers
The Carbon Dioxide absorber
and moisture absorber cartridges
are located in the upper cabinet
Soda lime absorbs
exhaled carbondioxide“Drierite”, “Dry-All” –
absorbs exhaled
moisture
(calcium sulfate +
cobalt chloride; turns
from blue to pink as it
absorbs moisture)
O2 or air must be added to the system
because it is closed to surrounding air
Technique
50. Connectors for the bore hose and Valve
assembly are located on the back panel.
• Patient wears nose clamps and breathes Xe/O2 through
a mouthpiece connected by tubing to the xenon
administration machine.
Technique
51. Xenon Imaging Protocol
• View: single, usually posterior projection, upright
or supine
• Three stage dynamic acquisition:
– Wash in – patient inhales Xe/O2 (initial single breath and
breath hold)
– Equilibrium – Xe rebreathed until concentration in lungs
and rebreathing system is constant (Xenon is distributed
throughout the lungs)
– Wash out – patient exhales Xe and rebreathes O2 until Xe
cleared from lungs
Technique
Single breath phase bypassed for patients too sick to hold their breath
52. Operation
Front panel controls
Position One:
Start - Patient breathes room air. System is charged
with oxygen.
Position Two:
Single breath and equilibrium imaging - This is when
you add Xe-133, either a bolus or a homogeneous
mixture. When the patient equilibrates, the user
switches the handle to washout position.
Position Three:
Washout - The patient is now breathing room air
from a one-way valve through the delivery system
and exhaling into the built-in charcoal trap. During
washout a pump draws the patient's expired breath
through the activated charcoal trap. The xenon is
stripped away and only clean air leaves the trap exit
port.
Technique
53. Tc-99m Pentetate Aerosol Administration
• A nebulizer is used to break the
liquid tracer into small particles by
directing a stream of air or O2
through the liquid; the gas moves
the particles forward and the
patient breathes them in
• Patient breathes the aerosol
through a mouthpiece or face
mask connected by tubing to the
nebulizer; the patient is
disconnected from the nebulizer
after inhaling the aerosol
Technique
54. Nebulizer Used to Generate
Radioaerosols
Pharmaceutical practice - Arthur J. Winfield, R. Michael E. Richards
Technique
55. • The size of the aerosol particles must be small
enough to be inhaled down into the smaller airways;
particle size/deposition is controlled by rate of gas
flow, pressure, tubing diameter and length, and
other factors
• Radiation safety considerations:
– Contamination of floor, patient’s upper chest, and area
around nose/mouth
– Coaching the patient before and during the exam has
shown to decrease the amount of contamination
Technique
56. Tc-99m Pentetate Imaging Protocol
• Tc99m DTPA aerosol must have correct oxygen flow rate
through nebulizer (at least 8 to 10 L/min)
• Take precautions not to allow contamination of patient’s nose,
mouth, upper chest, floor under patient and camera
• Views: multiple views; same as acquired for perfusion portion
of the exam
• All images are equilibrium images and no single breath or
washout images possible; wash out images are not possible
because the particles become stuck in the lung once they are
inhaled.
Technique
57.
58.
59. Technegas Generator
• Vapourises Tc99m
Pertechnetate injected into a
carbon crucible in the
presence of argon.
• Generates Technetium
labeled carbon nano-particle
suspended in argon gas.
• The gas inhaled by patient
through a disposable breather
kit.
• 1-3 breaths delivers the
required full dose
Technique
61. Distribution Patterns – Normal
Perfusion Xenon Aerosol
Greater activity
central lung area
(greatest tissue
mass)
Slightly decreased
activity lung
apices (normal
thinning)
Well defined
cardiac impression
Uniform tracer
distribution
throughout lungs
90% clearance
(washout)
3-4 min post
administration
Symmetric tracer
distribution from
apex to base in
both lungs
62. • Gut activity due to pt. swallowing
• Upper esophagus activity
• Improper breathing through mask/mouth
piece
• Missing proper start time on computer for
Xenon breath hold image
• Patient motion
Artifacts & Pitfalls
