Lung scintigraphy for the diagnosis of acute pulmonary embolism

Pulmonary embolism (PE) remains a major diagnostic challenge due to its potentially life-threatening nature and the clinical burden associated with anticoagulation therapy. While computed tomography pulmonary angiography (CTPA) has become the dominant imaging modality for suspected PE, limitations including radiation exposure - particularly to breast tissue-iodinated contrast administration, and concerns about overdiagnosis have prompted renewed interest in alternative strategies. Ventilation-perfusion (V/Q) scintigraphy, grounded in physiological assessment of pulmonary ventilation and perfusion, offers a non-invasive approach with substantially lower radiation and an excellent safety profile. However, planar V/Q imaging is limited by a high proportion of nondiagnostic studies. Recent advances in single-photon emission computed tomography (SPECT) and hybrid SPECT/CT have significantly improved diagnostic accuracy, reduced inconclusive results, and enhanced the ability to distinguish embolic from non-embolic causes of perfusion defects. Despite widespread adoption, formal outcome validation of SPECT-based diagnostic algorithms has been lacking until the recent completion of the international SPECTACULAR randomized controlled trial, designed to compare planar V/Q, CTPA, and SPECT V/Q strategies using three-month thromboembolic recurrence as the reference for clinical safety. Results will be available shortly following presentation at SNMMI annual meeting 2025. Lung scintigraphy plays an essential role in specific populations, including pregnancy or contrast use is restricted. Moreover, ongoing developments in V/Q PET imaging and artificial intelligence-driven post-processing promise improved spatial resolution, quantification, and workflow efficiency, while advanced molecular tracers may enable characterization of thrombus biology. In summary, V/Q scintigraphy - particularly SPECT and SPECT/CT - remains a robust and clinically valuable modality for diagnosing acute PE, offering a radiation-sparing alternative to CTPA. Technological innovation and high-quality outcome evidence are likely to support its broader integration into future diagnostic pathways.