Ventilation/perfusion lung scintigraphy: what is still needed? A review considering technetium-99m-labeled macro-aggregates of albumin

Abstract

Lung perfusion scintigraphy (LPS) with technetium-99m-labeled macro-aggregates of albumin (Tc-99m-MAA) is well established in the diagnostic of pulmonary embolism (PE). In the last decade, it was shown that single-photon emission computer tomography (SPECT) acquisition of LPS overcame static scintigraphy. Furthermore, there are rare indications for LPS, such as preoperative quantification of regional lung function prior to lung resection or transplantation, optimization of lung cancer radiation therapy, quantification of right-left shunt, planning of intra-arterial chemotherapy, and several rare indications in pediatrics. Moreover, LPS with Tc-99m-MAA is a safe method with low radiation exposure. PE can also be diagnosed by spiral computer tomography (CT), ultrasound, magnetic resonance angiography, or pulmonary angiography (PA, former gold standard). The present review considers all these methods, especially spiral CT, and compares them with LPS with respect to sensitivity and specificity and gives an overview of established and newer publications. It shows that LPS with Tc-99m-MAA represents a diagnostic method of continuing value for PE. In comparison with spiral CT and/or PA, LPS is not to be defeated as mentioned also by the most actual Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) II reports. This applies in particular to chronic or recurring embolisms, whereas currently spiral CT may be of greater value for major or life-threatening embolisms. At present, LPS cannot be replaced by other methods in some applications, such as pediatrics or in the quantification of regional pulmonary function in a preoperative context or prior to radiation therapy. LPS still has a place in the diagnostics of PE and is irreplaceable in several rare indications as described earlier.

PulmoBind, an Adrenomedullin-Based Molecular Lung Imaging Tool

“…Lung perfusion scintigraphy with 99m Tclabeled macroaggregates of albumin ( 99m Tc-MAA) is generally con- sidered to be the method of choice for the diagnosis of pulmonary embolism. However, this imaging technique relies on the capture of 99m Tc-MAA in the pulmonary bloodstream causing temporary microembolisms in a sufficient amount to generate a good image (24). If the pulmonary circulation is already compromised, as in patients with severe pulmonary hypertension, this procedure could have deleterious effects; some safety issues have been pointed out for patients with pulmonary hypertension or a right-left shunt (24).…”

“…However, this imaging technique relies on the capture of 99m Tc-MAA in the pulmonary bloodstream causing temporary microembolisms in a sufficient amount to generate a good image (24). If the pulmonary circulation is already compromised, as in patients with severe pulmonary hypertension, this procedure could have deleterious effects; some safety issues have been pointed out for patients with pulmonary hypertension or a right-left shunt (24). Thus, a lung imaging agent such as an AM derivative would expand the clinical relevance of lung scintigraphy because of its ability to image all sizes of vascular beds without any blockade.…”

Diagnosing venous thromboembolism in pregnancy

“…5 PE may be identified or excluded by several diagnostic and clinical tests. These include clinical scores (modified Wells' score 6 ), plasma D-dimer measurement, CT pulmonary angiography (CTPA) and ventilation/perfusion (VQ) scanning, [7][8][9] although the diagnostic performance of some of these, e.g. plasma Ddimer 10 and CTPA, [11][12][13][14][15] is impaired during pregnancy.…”

Pulmonary-Vein Stenosis Can Mimic Massive Pulmonary Embolism After Radiofrequency Ablation for Atrial Fibrillation

“…7,9 Also, V /Q mismatch or perfusion defect of a certain lobe on V /Q scan occurs in 80% of pulmonary-vein-stenosis patients, and a higher percentage in pulmonary-embolism patients. [10][11][12][13][14] Thus, it is hard to distinguish between pulmonary-vein stenosis and pulmonary embolism based on symptoms and V /Q scan. CTPA is more sensitive for differentiation because it shows the positions of vein stenosis and pulmonary embolus separately.…”