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J Med Imaging Radiat Oncol. 2016 Aug;60(4):492-7. doi: 10.1111/1754-9485.12471. Epub 2016 May 11.

SPECT-CT/VQ versus CTPA for diagnosing pulmonary embolus and other lung pathology: Pre-existing lung disease should not be a contraindication.

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Department of Medical Imaging, St Vincent's Hospital, Darlinghurst, New South Wales, Australia.
Department of Radiology, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia.



Single Photon Emission Computed Tomography-Ventilation-Perfusion (SPECT-VQ) with low-dose CT (SPECT-CT/VQ) has equivalent diagnostic accuracy to CTPA for diagnosing pulmonary embolus (PE) while using lower radiation doses, but is underutilized owing to perceived inaccuracy of scintigraphy in the setting of pre-existing lung disease. This study assesses the accuracy of SPECT-CT/VQ compared with CTPA for the diagnosis of PE, including in patients with pre-existing lung disease.


Retrospective non-inferiority cohort study of all patients who underwent SPECT-CT/VQ scanning at St Vincent's Hospital, NSW, from June 2012 to November 2013, who also had a CTPA within the same admission and <72 h apart (n = 102).


SPECT-CT/VQ had 100% sensitivity and 94.4% specificity when compared with CTPA. Of the 102 patients, 14 were lung transplant patients, and 27 had other pre-existing lung disease (41/102, 40.2%), with SPECT-CT/VQ having a sensitivity of 100% and specificity of 97.2% in this patient group. Non-inferiority of SPECT-CT/VQ was demonstrated at a significance level of 0.005.


SPECT-CT/VQ has high sensitivity and specificity for diagnosing PE compared with CTPA, even among patients with pre-existing lung disease, with lower radiation doses.


CTPA; SPECT; VQ; pulmonary embolus; radiation dose

[Indexed for MEDLINE]

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