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General Clinical Specialties: PulmonaryPET, Ventilation-Perfusion |
1 Nuclear Medicine, Royal North Shore Hospital, St Leonards, New South Wales, Australia
363
Objectives: A potential advantage of CTPA in the assessment of pulmonary embolism (PE) is its ability to characterise the lung parenchyma and assess other conditions which may give a similar clinical presentation. Hybrid SPECT/CT technology allows low dose CT scans to be done concurrently with V/Q SPECT, although the clinical impact is unknown. The aim of this study was to determine whether the addition of a low dose CT scan can improve the diagnostic accuracy of V/Q scintigraphy in the assessment of suspected PE.
Methods: We evaluated a total of 48 patients with suspected PE in whom final diagnosis could be confidently determined. The patient group comprised patients selected at random with or without co-existent lung disease. All had a low dose CT (30-50mAs) scan immediately following a V/Q SPECT scan (Technegas ventilation, Tc-99m MAA perfusion) using a hybrid scanner (Philips). Studies were reported blindly by 2 (or 3 if there was disagreement) experienced Nuclear Medicine physicians who viewed the V/Q SPECT study initially and then the co-registered SPECT/CT scan using Hermes Multimodality fusion software.
Results: Of the 16 patients (33%) with PE, V/Q SPECT was positive in 15 (94%). Of the 32 patients (67%) without PE, 6 (19%) V/Q SPECT scans were reported as PE positive. Of these, 3 (50%), were correctly reclassified as PE negative when the SPECT/CT scan was viewed.
Conclusions: The addition of low dose CT to V/Q SPECT improves diagnostic accuracy by reducing false positive scan results (by 50% in this series). VQ SPECT/CT can characterise the cause of non-embolic perfusion abnormalities in some patients.
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