Lung Scan &

Rdn. Venography

Jiraporn Sriprapaporn, M.D.

Nuclear Medicine,

Siriraj Hospital

Last updated on 21 JAN 2017

Copy Right By J Sriprapaporn

Contents

Anatomy

Physiology

Mechanism

Technique

Indications

Interpretation

Radionuclide venography

V/Q Lung scans

Respiratory System

Perfusion lung scan Tc-99m MAA

Ventilation lung scan

Xe-133, Tc-99m aerosol, Technegas

Anatomy

Right lung & left lung

Bronchopulmonary segments

(artery, vein, & bronchus)

Right Lung: 3 lobes; RUL,RML, & RLL

Left Lung: 2 lobes; LUL (Lingular segments) & LLL

Adults: Pulmonary arterioles 280 million

(Children adult number ~ 8 yr)

Bronchopulmonary Segments

http://www.anatomychartee.us/anatomy-lung-segments-diagram-system/lung-segmental-anatomy/

http://radiologykey.com/pulmonary-scintigraphy/

Blood Supply

2 Systems:

Pulmonary arteries: 95%

Bronchial arteries: 5%

Physiology

AIR Respiratory tract: trachea bronchi bronchioles alveoli

Function: Gas exchange

Distribution of Q & V from apex to base is not uniform in the upright position (gravity effect)

Gravity effects the distribution of both Q & V (affects perfusion > ventilation)

Effects of Gravity (Upright Position)

APEX VENTILATION PERFUSION V/Q RATIO

BASE 1.5-2 folds 3-5 folds

Pathophysiology

Ventilation abnormality redistribution of

pulmonary perfusion

Hypoventilation reflex vasoconstriction hypoperfusion

Acute hypoperfusion rarely produces

hypoventilation or minimal; not clinically significant

Lung Scan

PERFUSION LUNG SCAN (Q)

Tc-99m MAA

VENTILATION LUNG SCAN (V)

Xe-133, Xe-127, Kr- 81m

Tc-99m DTPA/ phytate aerosol

Technegas

Indications of V/Q Lung Scan

Acute pulmonary embolism*

Pulmonary hypertension

Right-to-left shunt

Prior to thoracic surgery

Pulmonary Embolism

Most important complication of DVT

Symptomatic, fatal*

Asymptomatic (silent)

Origin: Leg DVT (70-80%)

DIAGNOSIS OF PULMONARY EMBOLISM

Clinicals : Inaccurate Lab tests : D-dimer Arterial Blood Gases: Hypoxemia, A-A gradient ECG : Classic S1Q3T3 pattern CXR : Normal or mild abn (*R/O other

diseases) V/Q lung scan : V/Q mismatched

defects Pulmonary Angiography*** Gold

standard Pulmonary CTA Others: MRI

Perfusion Lung Scan: Principle

Tracer: Tc-99m MAA, particle size=20-40 u

Mechanism: Capillary blockade in proportion to regional blood flow

Number of particles: minimum 100,000; optimal 200,000-600,000

Less than 1/1000 capillaries are blocked

Biological T1/2 = 2-4 hr Reticuloendothelial (RE) system

Defects from PE

// bronchopulmonary

segments

Essentials Nucl Med

Reduced Number of Particles Injected

Pediatric patients

Patients with suspected or known Rt-to-Lt

shunt

Patients with pulmonary hypertension

Patients with prior pneumonectomy

Patients with single lung transplant

Perfusion Lung Scan: Techniques

Radiopharm: Tc-99m MAA Dose 3-5 mCi for adults IV injection in supine

position Do not draw blood into

syringe; “hot spots” in Q scan

Imaging techniques Static planar images 6-8

views, 500 kcts SPECT imaging

Ventilation Lung Scan: Principle

Particle size: Smaller go deeper!

Tracers

Inert gas: 133Xe, 127Xe, 81mKr

Aerosol*: 99mTc-DTPA/ phytate [Tc-99m

aerosol particle size = 0.5-3 um]

Technegas: particle size = 0.02-0.2 um

Ventilation Agents

Xe-133 Xe-127 Kr-81m Tc-99m radioaerosol

Technegas/ Pertechnegas

T1/2 5.3d 36.4d 13s 6h 6h

energy 80 203 190 140 140

Status Gas Gas Gas Aerosol (0.5-3 um)

Gas-like (0.02-0.2 um)

Cost Low High High Low High

Before/After Q scan

B A A B B

Multiple V N N Y Y Y

Ventilation Lung Scan: Techniques

Patient preparation: None

Techniques:

Inhalation, upright position is preferred.

Needs patient’s cooperation

Xe-133 Ventilation Lung Scan

Single view-3 phases: Washin-Equilibrium-Washout

Radio-aerosol Ventilation Lung Scan

O2

• Imaging of multiple views

• Relatively large particles central

airway deposition !

TECHNEGAS

Technegas Ventilation Scan

• Ultrafine particles

• Ideal for ventilation lung SPECT

Figure 1. Normal V/Q SPECT. using Technegas and Tc-99 m MAA are aligned and displayed in transverse, coronal and sagittal planes

Roach PJ, et al SNM08

V/Q SPECT

V/P SPECT/CT images

A wedge-shaped pleural-based large mismatched perfusion defect is seen anteriorly in the left lung (yellow arrows) on the axial (upper row), coronal (middle row) and sagittal (lower row) projections.

No other explanations for the perfusion defect can be seen on the normal ventilation scan and low-dose CT images

2014, PMCID: PMC4003400

Interpretation of Lung Scan

1. Pretest clinical probability

2. Perfusion lung Scan (Q)

3. Ventilation lung Scan (V)

4. CXR (within 24 hrs)

Normal Lung Scan

Uniform distribution of the radioactivity

No V/Q defect

1. Nonuniform distribution

2. Perfusion and/ or ventilation defect

Nonsegmental defect

Segmental defect: wedged-shaped & pleural-based defect Large defect: > 75% of segment

Moderate defect: 25-75% of segment

Small defect: < 25% of segment

Abnormal Lung Scan

V/Q Match vs Mismatch

V/Q matched defect: Abn both Q & V

V/Q mismatch defect: Abn Q, Normal V

Pulmonary Embolism

Segmental Non-segmental

Pulmonary embolism

Pulmonary infarct

Tumors

Pleural effusion

Cardiomegaly

Mediastinal or hilar adenopathy

Pneumonia

Bullae

Metal artifacts

Non-PE Diseases/Conditions

Findings:

Patchy distribution

Nonsegmental defect

Matched V/Q defect(s)

Abnormal CXR finding corresponding to the area of V/Q defect

Causes

COPD

Blebs, bullae

Pulmonary edema, CHF

Pleural effusion

Asthma

Pulmonary trauma

Mucous plug

Bronchogenic CA

Pneumonia

V/Q Matched Abnormalities

V/Q Mismatches: Causes

Acute PE

Previous PE

Bronchogenic carcinoma

Vasculitis

Previous radiation therapy

Pulmonary vasc anormalies

Typical Scintigraphic Findings For PE

Multiple segmental perfusion defects

Normal ventilation

Usually normal CXR

“Mismatched V/Q defects”

V/P SPECT/CT images for PE

A wedge-shaped pleural-based large mismatched perfusion defect is seen anteriorly in the left lung (yellow arrows) on the axial (upper row), coronal (middle row) and sagittal (lower row) projections.

No other explanations for the perfusion defect can be seen on the normal ventilation scan and low-dose CT images

2014, PMCID: PMC4003400

Interpretation of Acute PE

PIOPED

Modified PIOPED II

Perfusion-only modified PIOPED II

Perfusion-only PISAPED

PIOPED " The Prospective Investigation of Pulmonary Embolism Diagnosis "

PIOPED

" The Prospective Investigation of Pulmonary Embolism Diagnosis “

Used pulmonary angiogram as a gold standard.

The criteria were developed in late 1983

The largest study of accuracy of lung scan in the Dx of acute PE

6 medical centers in U.S.A.

PIOPED II CTA PIOPED III MRA

PIOPED I V/Q Lung scan

“PIOPED CRITERIA” for Interpretation of Acute PE

Normal Exclude significant PE !, with an incidence of 2% to 4% &

the chance of significant morbidity or mortality from PE is < 1%.

Very low probability

Low probability

Intermediate

High probability: > 2 large segmental mismatched V/Q defects,

negative CXR

Ventilation, Perfusion, and Radiographic Interpretive Criteria for PE

(SNM guideline v4, 2012)

PIOPED Modified PIOPED II

High LR [> 80% risk]

- >2 large mismatched (V:Q)

segmental defects*

High LR [85-90% risk]

- > 2 large mismatched (V:Q) segmental defects*

Borderline high LR

- 2 large mismatched (V:Q)

segmental defects*

Intermediate LR [20-80% risk]

- 2 moderate or 1 large mismatched

(V:Q) defect*

- Difficult to categorize as high or low

Nondiagnostic [20-80% risk]

- All other findings

Borderline low LR

- 1 matched (V:Q) defect, CXR-negative

Low LR [< 20% risk]

- Nonsegmental perfusion defects†

- Q defect substantially < CXR defect

- Matched (V:Q) defects, CXR-negative

- Any number of small Q defects*

Very low LR [< 10 % risk]

- Nonsegmental†

- Q defect < CXR lesion

- 1–3 small segmental*defects

- Solitary matched (V:Q:CXR) defect (#1 segment) in mid

or upper lung

- Stripe sign‡

- Solitary large pleural effusion§

- > 2 matched (V:Q) defects, regionally normal CXR

Normal

- No Q defects

Normal

- No Q defects

*Or equivalent where large segmental defect, >75% of segment, equals 1 segmental equivalent; moderate defect, 25%–75% of segment, equals 0.5 segmental equivalent; small defect, < 25%, is not counted.

Very Low Probability

• Nonsegmental defects*

• Q defect < CXR lesion

• 1-3 small segmental defects

• Single triple matched defect (V, Q, CXR) in mid or upper zone

• Stripe sign

• Solitary large pleural effusion

• ≥2 matched defects, normal CXR

< 10% chance for

PE

"Stripe Sign" = A thin line (stripe) of activity (perfusion) at the pleural surface of a Q defect.

The finding is associated is likely related to spared perfusion in the cortex of the lung [Sostman HD, Gottschalk A. Radiology 1992 ]

"Stripe Sign" is suggested to indicate very low probability = 7% of lung zones with the stripe sign had PE present on PAG in the PIOPED study [Gottschalk A, et al. J Nucl Med 1993]

STRIPE SIGN

PPV of V/Q Lung Scan in Diagnosis of PE

Clinical Probability

Scan Category 80-100% 20-79% 0-19%

High 95% 85% 83%

Intermediate 71% 29% 14%

Low 43% 16% 4%

Normal/NN 0% 7% 2%

[PIOPED JAMA 1990, Sostman HD Radiology 1994]

Comparison of Interpretive Schema for Acute Pulmonary Emboli

Method Sensitivity (%) Specificity (%)

PIOPED 41 97

Modified PIOPED II 85 93

PISAPED 80-86 93-97

MDCT 83 96

Essentials in NM

2014, PMCID: PMC4003400

V/Q Lung Scan Classification

High Prob

Nondiagnostic

Very low prob

Normal

Management Guideline

Normal Rule out clinically significant PE

Very-low probability Find out other causes of

symptoms.

Nondiagnostic Cannot rule out PE and needs

further investigations such as ultrasound for DVT.

High prob The patient can be treated for PE.

Pulmonary Embolism: Before & After Anticoagulant Rx

Acute Pulmonary Embolism

Perfusion-Ventilation lung scan ***

Multiple segmental V/Q mismatched defects , no radiographic abnormality

Increasing no. of defects increasing specificity

Pulmonary angiography is the original gold standard, now usually being replaced with CTPA.

V/Q scan cannot DDx acute from chronic PE, so F/U scan to evaluate the lung status post Rx *** (Baseline for the new episode, if any)

V/Q Lung Scan for Dx PE

Advantages

Simple, noninvasive, safe, and economical

High specificity (98%) esp. increasing no. of defects

The usefulness is well documented.

Disadvantages

Not widely available

Minimal radiation

Low sensitivity (41%)

Limitation in abn CXR

V/Q scan cannot DDx acute from chronic PE need F/U scan

Applications for Non-embolic Lung Disorders

Rt-to-Lt shunt

Intracardiac shunt

Intrapulmonary shunt

Evaluate lung function prior thoracic surgery eg. lung cancer

Quantitative lung function study

Right-to-left Shunt Systemic Circulation

Presence of Tc-99m MAA in the systemic circulation; brain & kidneys

Technique: Limited MAA particles.

Lung Scan in Rt-to-Lt Shunt

Prior Thoracic Surgery

Quantitative lung function study

To evaluate regional lung function and predict residual lung function post surgical resection

Lung cancer

Other lung diseases

VENOUS SYSTEM

Leg Veins

Deep Vein Thrombosis

Incidence: 2.5 million in US Risks: Stasis Symptoms: Leg swelling/

pain/tender/warm/red Complication: most important

= pulmonary embolism Dx of DVT

Clinical Dx is unreliable Noninvasive tests Invasive tests

Diagnosis of DVT

Clinicals : Unreliable

Lab tests : D-Dimer

Impedance Plethysmography (IPG)

Doppler ultrasonography

Color Duplex Imaging

Radionuclide Venography

In-111 labeled platelet

In-111 labeled antifibrin Ab

Tc-99m labeled peptides (Acutect)

Contrast Venography *** [Gold standard]

CTV

MRV

Radionuclide Venography

Ascending Radionuclide Venography (RNV) Tc-99m phytate/ SC

Tc-99m MAA* (+Q scan)

Tc-99m labeled RBC Radionuclide Venography

Tc-99m labelled peptide venography

Ascending RNV

Principle: Direct injection of the radiotracer in to

foot veins

Mechanism: To evaluate venous flow; venous

occlusion or evidence of collateral circulation

Anatomy: calf veins*, popliteal vein, femoral, ext

iliac & common iliac, IVC

Ascending RNV: Techniques

Radiopharm: Tc-99m phytate/ sulfur colloid, Tc-99m MAA* (+ Q lung scan)

Inject a tracer via (bilateral) foot veins

On tourniquets above ankles to visualize deep veins and off tourniquets for superficial veins

Ascending RNV: Interpretation

Bilateral comparison, on & off TQ

Normal: Good flow without signs of venous occlusion

Abnormal: Obliteration of flow, filling defect, asymmetric flow +/-collaterals

Normal Asc RNV

Whole-body Images

phytate

Multiple Static Images

Normal vs Abnormal RNV

DVT WITH PE

Accuracy of Asc RNV

Authors Year No. (studies)

Sen (%)

Spec (%)

Corr (%)

Site of DVT

Webber (12) 1974 30 65 92 77 Overall Henkin (13) 1974 25 100 86 96 Proximal Van Kirk (14) 1976 19 100 95 95 Overall Vlahos (15) 1976 52 100 100 100 Pelvis 98 89 100 97 Thigh 98 92 97 95 Calf Ennis (16) 1977 154 90 89 95 Overall

Cordoba (17) 1977 44 100 80 94 Overall Ryo (18) 1977 47 89 66 89 Overall Gomes (19) 1982 51 88 65 67 Overall Mohamadiyeh(20) 1993 32 90 73 89 Proximal

Mangkharak 1998 72 88 96 90 Overall 55 95 97 96 Pelvic 72 95 100 90 Thigh 72 77 96 83 Calf

Mangkharak J, et al. J Med Assoc Thai 1998;81:432-441

RNV-upper Extremities

Normal

Abnormal

Advantages & Disadvantages

Contrast Venography

Most reliable for Dx (gold

std.)

Need skilled team

Good anatomic visualization

(calf iliac veins & IVC)

More Invasive

Potential risks

Not suitable for frequent F/U

Not provide information about

associated PE

Radionuclide Venography

Reliable results esp. proximal

vein

Simpler

Poorer anatomic details

(good only for proximal v.)

Less invasive

Safe

More suitable for frequent F/U

Provide information about

associated PE (Tc-99m MAA)

Tc-99m labeled RBC Radionuclide Venography

Or blood-pool radionuclide venography

equilibrium stage

Inject the radiotracer via any vein

Need high-resolution collimator

Image quality depends on labeling efficiency

Normal Tc-99m RBC RNV

Tc-99m RBC RNV

Whole-body vs

multiple overlapping static images

Tc-99m Labeled RBC vs Ascending RNV

Advantages

Do not need foot vein access, easier

Possible less painful

Disadvantages

Image quality depends on labeling efficiency

Not direct evaluation of venous flow

Less anatomical details

Concomitant Q lung scan is impossible.

Both cannot DDx acute vs chronic DVT !

Summary

Diagnosis of Ac PE needs clinical and other diagnostic tests eg. venous US, VQ, CTA.

Lung and vascular scintigraphy has an important role in evaluation of patients with suspected PE &/or DVT in an appropriate setting esp. normal CXR, C/I for CTA.

Tc-99m MAA can be used to evaluate DVT & PE in the same setting.

It can be used not only for the diagnosis but also for the follow-up after treatment.

References

Essentials in Nuclear Medicine, 2013

The Requisites in Nuclear Medicine, 2014

Pulmonary embolism http://emedicine.medscape.com/article/300901-overview

Online Radiography Continuing Education for Radiologic X ray Technologist. https://www.ceessentials.net/article12.html

Lung scan guideline v 4.0: http://interactive.snm.org/DOCS/LUNG_SCINTIGRAPHY_V4_FINAL.PDF