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PULMONARY EMBOLUS
Authored By: Brandon Peters and Akash Sharma.
Patient: 55 year old
History: 56 year old male with hypoxia
Image Size:[small][as-submitted]

Fig. 1
Xenon-133 lung ventilation images

Fig. 2
TC99m-MAA lung perfusion images

Fig. 3
Frontal chest radiograph

Fig. 4
Contrast enhanced axial CT

Fig. 5
Contrast enhanced axial CT

Fig. 6
Contrast enhanced axial CT

Fig. 7
Contrast enhanced axial CT
Image Size:[small][as-submitted]

Findings: Lung ventilation scan:  Normal

Lung perfusion scan:  Moderate sized mismatched defect in the lateral basal segment of the right lower lobe seen on RPO and posterior views.  No other defects seen.

Chest radiograph:  No interstitial or airspace opacities.

Chest CT:  Thrombus in the lateral segmental artery of the right lower lobe.
DDx: Single segmental mismatch:

1.  Pulmonary embolus
2.  Localized fibrosis
Diagnosis: Pulmonary embolus
General Discussion: This is a 56 year old male with myasthenia gravis who became acutely hypoxic. The patient had no previous history of thrombosis or pulmonary embolus.
Specific Discussion: The original PIOPED criteria listed a single segmental mismatch as low probability for pulmonary embolus.   However, it was seen that this abnormality was more accurately called intermediate probablity if the defect is moderate or large (>25% of a segment) as a not insignificant number of pulmonary emboli were seen in this group when compared to pulmonary angiography.  If the mismatched defect is single and less than 25% of a segment, it is appropriately labelled low probability for pulmonary embolus.  A single segmental defect that is clearly seen on two or more views must be either moderate or large therefore making the interpretation intermediate probability for pulmonary embolism.
References: Freitas JE.  Modified PIOPED criteria used in clinical practice.  J Nucl Med 1995;36: 1573-8.
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Additional Details:

Case Number: 94186Owner(s): Brandon Peters and Akash SharmaLast Updated: 02-07-2013
Anatomy: Cardiopulmonary   Pathology: Vascular
Modality: CT, Nuc MedAccess Level: Readable by all users, writable by NucMed Certifiers
Keywords: vqnm

Case has been viewed 64 times.
Certified by Akash Sharma on 03-10-2010

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