V/Q SPECT and computed tomographic pulmonary angiography.

Area of Science:

• Radiology
• Nuclear Medicine
• Diagnostic Imaging

Background:

• Computed tomography pulmonary angiography (CTPA) has largely replaced planar ventilation/perfusion (V/Q) scintigraphy for pulmonary embolism (PE) diagnosis.
• CTPA offers reasonable sensitivity, good prognostic value in negative cases, and can provide alternative diagnoses.
• However, CTPA has limitations including suboptimal sensitivity (83% in PIOPED II), potential issues with predictive values, contrast-related risks, and radiation exposure.

Purpose of the Study:

• To evaluate V/Q single-photon emission computed tomography (SPECT) as a diagnostic tool for PE.
• To compare the efficacy and limitations of V/Q SPECT against CTPA for PE diagnosis.

Main Methods:

• Review of CTPA and V/Q SPECT techniques for diagnosing pulmonary embolism.
• Analysis of existing study data, including the Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II) study.
• Comparison of sensitivity, specificity, predictive values, and associated risks of both imaging modalities.

Main Results:

• V/Q SPECT has emerged as a mature technique with excellent sensitivity for PE diagnosis.
• V/Q SPECT is not associated with most of the limitations of CTPA, such as contrast nephropathy and radiation exposure.
• CTPA remains invaluable in specific scenarios, but V/Q SPECT is superior to planar V/Q and offers advantages over CTPA in many situations.

Conclusions:

• V/Q SPECT is a highly sensitive and effective modality for diagnosing PE, often superior to CTPA.
• V/Q SPECT can be used as an initial diagnostic tool for PE in various clinical settings.
• Limitations of V/Q SPECT exist in patients with severe COPD or abnormal chest X-rays, while CTPA has specific indications.