Radiographic Evaluation of a Radiographic Evaluation of a Pulmonary EmbolismPulmonary Embolism

Dr Mohamed El Safwany, MD.Dr Mohamed El Safwany, MD.

Intended learning outcomeIntended learning outcome

The student should learn at the end of this The student should learn at the end of this lecture principles of Radiological lecture principles of Radiological evaluation of Pulmonary Embolism.evaluation of Pulmonary Embolism.

PresentationPresentation

DyspneaDyspnea

Pleuritic chest painPleuritic chest pain

Low-grade feverLow-grade fever

TachycardiaTachycardia

EvaluationEvaluation

ABG – Respiratory alkalosis, hypoxiaABG – Respiratory alkalosis, hypoxia

ECG – Sinus tachycardia & S1Q3T3ECG – Sinus tachycardia & S1Q3T3

D-Dimer – A negative result rules out PED-Dimer – A negative result rules out PE

CXRCXR

V/Q ScanV/Q Scan

Spiral CT with contrastSpiral CT with contrast

AngiogramAngiogram

CXRCXR

Initial CXR usually normal.Initial CXR usually normal.

May progress to show atelectasis, plueral May progress to show atelectasis, plueral effusion and elevated hemidiaphram.effusion and elevated hemidiaphram.

Hampton’s hump and Westermark sign Hampton’s hump and Westermark sign are classic findings but are not usually are classic findings but are not usually present.present.

CXRCXRHampton’s Hump – Hampton’s Hump – consists of a pleura consists of a pleura based shallow wedge-based shallow wedge-shaped consolidation in shaped consolidation in the lung periphery with the lung periphery with the base against the the base against the pleural surface.pleural surface.

CXRCXR

Westermark signWestermark sign – Dilatation – Dilatation of pulmonary vessels proximal of pulmonary vessels proximal to embolism along with to embolism along with collapse of distal vessels, often collapse of distal vessels, often with a sharp cut off.with a sharp cut off.

V/Q ScanV/Q Scan

Ventilation-perfusion scanning is a radiological Ventilation-perfusion scanning is a radiological procedure which is often used to confirm or exclude the procedure which is often used to confirm or exclude the diagnosis of pulmonary embolism. It may also be used to diagnosis of pulmonary embolism. It may also be used to monitor treatment.monitor treatment.Ventilation (V) – Achieved by the inhalation of Ventilation (V) – Achieved by the inhalation of Technetium DTPA. DTPA is an elongated version of Technetium DTPA. DTPA is an elongated version of EDTA and is a heavy metal chelator. Ventilation is EDTA and is a heavy metal chelator. Ventilation is assessed under a gamma camera.assessed under a gamma camera.Perfusion (Q) – Achieved by injecting the patient with Perfusion (Q) – Achieved by injecting the patient with Technetium 99m, which is coupled with macro Technetium 99m, which is coupled with macro aggregated albumin (MAA). An embolus shows up as a aggregated albumin (MAA). An embolus shows up as a cold area when the patient is placed under a gamma cold area when the patient is placed under a gamma camera.camera.

Abnormal V/Q ScanAbnormal V/Q Scan

Abnormal V/Q ScanAbnormal V/Q Scan

Perfusion Ventilation

V/Q Scan ResultsV/Q Scan Results

Clinical probability of emboliClinical probability of emboli

Scan Scan CategoryCategory

HighHigh IntermediateIntermediate LowLow

HighHigh 9595 8686 5656

IntermediateIntermediate 6666 2828 1515

LowLow 4040 1515 44

Normal or Normal or near normalnear normal

00 66 22

Likelihood of pulmonary embolism according to scan category and clinical probability in PIOPED study

Spiral CTSpiral CT

Spiral CT first introduced in 1990sSpiral CT first introduced in 1990s

In older CT scanners, the X-ray source would move in a In older CT scanners, the X-ray source would move in a circular fashion to acquire a single slice. Once the slice circular fashion to acquire a single slice. Once the slice had been completed, the scanner table would move to had been completed, the scanner table would move to position the patient for the next slice.position the patient for the next slice.

In helical CT the X-ray source and detectors are In helical CT the X-ray source and detectors are attached to a freely rotating gantry. During a scan, the attached to a freely rotating gantry. During a scan, the table moves the patient smoothly through the scanner. table moves the patient smoothly through the scanner. The name derives from the helical or spiral path traced The name derives from the helical or spiral path traced out by the X-ray beam.out by the X-ray beam.

Spiral CTSpiral CT

Major advantage of Spiral CT is speed:Major advantage of Spiral CT is speed:– Often the patient can hold their breath for the entire Often the patient can hold their breath for the entire

study, reducing motion artifacts.study, reducing motion artifacts.– Allows for more optimal use of intravenous contrast Allows for more optimal use of intravenous contrast

enhancement.enhancement.– Spiral CT is quicker than the equivalent conventional Spiral CT is quicker than the equivalent conventional

CT permitting the use of higher resolution acquisitions CT permitting the use of higher resolution acquisitions in the same study time.in the same study time.

Contraindicated in cases of renal disease.Contraindicated in cases of renal disease.Sensitive for PE in the proximal pulmonary Sensitive for PE in the proximal pulmonary arteries, but less so in the distal segments.arteries, but less so in the distal segments.

CT AngiogramCT Angiogram

Quickly becoming the test of choice for initial evaluation Quickly becoming the test of choice for initial evaluation of a suspected PE.of a suspected PE.CT unlikely to miss any lesion.CT unlikely to miss any lesion.CT has better sensitivity, specificity and can be used CT has better sensitivity, specificity and can be used directly to screen for PE.directly to screen for PE.CT can be used to follow up “non diagnostic V/Q scans.CT can be used to follow up “non diagnostic V/Q scans.

CT AngiogramCT Angiogram

Chest computed Chest computed tomography scanning tomography scanning demonstrating demonstrating extensive embolization extensive embolization of the pulmonary of the pulmonary arteries.arteries.

Pulmonary angiogramPulmonary angiogram

Gold Standard.Gold Standard.

Positive angiogram provides 100% Positive angiogram provides 100% certainty that an obstruction exists in the certainty that an obstruction exists in the pulmonary artery.pulmonary artery.

Negative angiogram provides > 90% Negative angiogram provides > 90% certainty in the exclusion of PE.certainty in the exclusion of PE.

Pulmonary angiogramPulmonary angiogram

Left-sided pulmonary Left-sided pulmonary angiogram showing extensive angiogram showing extensive filling defects within the left filling defects within the left pulmonary artery and its pulmonary artery and its branches.branches.

Plain chest radiograph – Usually normal Plain chest radiograph – Usually normal and non-specific signs.and non-specific signs.

Radionuclide ventilation-perfusion lung Radionuclide ventilation-perfusion lung scan.scan.

CT Angiography of the pulmonary arteries CT Angiography of the pulmonary arteries – Quickly becoming method of choice.– Quickly becoming method of choice.

Pulmonary angiography – Gold standard Pulmonary angiography – Gold standard but invasive.but invasive.

Text BookText Book

David Sutton’s RadiologyDavid Sutton’s Radiology

Clark’s Radiographic positioning and Clark’s Radiographic positioning and techniquestechniques

AssignmentAssignment

Two students will be selected for Two students will be selected for assignment.assignment.

QuestionQuestion

Describe value of CT in evaluation of Describe value of CT in evaluation of pulmonary embolis?pulmonary embolis?

Thank YouThank You

ReferencesReferences

Up to date Online. Diagnosis of Acute Pulmonary Up to date Online. Diagnosis of Acute Pulmonary Embolism. Last revised March 7, 2007.Embolism. Last revised March 7, 2007.

Pulmonary Embolism. http://www.e-radiography.netPulmonary Embolism. http://www.e-radiography.net