Diagnosis of Pulmonary Embolism: Conventional Ventilation/Perfusion SPECT Is Superior to the Combination of Perfusion SPECT and Nonenhanced CT

Abstract

Background: Ventilation/perfusion single-emission photon CT (V/P-SPECT) is widely used to detect pulmonary embolism (PE). Any pathological deficit on P-SPECT with a corresponding unremarkable V-SPECT is considered an embolism. This means that a deficit on P-SPECT with a corresponding deficit on the ventilation scan correlates with other lung pathologies such as pneumonia, bullous emphysema or tumor. In principle, it is possible to identify any of these lung pathologies on nonenhanced chest CT and so this technique has the potential to replace V-SPECT in the diagnosis of PE. Today, SPECT/CT hybrid imaging systems are increasingly applied in clinical routines. Objectives: We investigated whether embolism can be diagnosed using a combined P-SPECT/CT hybrid imaging approach without V-SPECT. Methods: Ninety-three patients with clinically suspected embolism were investigated with standard V/P-SPECT and a nonenhanced CT scan on a combined SPECT/CT system. A diagnosis of embolism was based on V/P-SPECT (gold standard). P-SPECT/CT datasets were blinded and analyzed without any knowledge of the V-SPECT data. The accuracy of P-SPECT/CT was compared to the gold standard. Results: Embolism was diagnosed in 24/93 patients using V/P-SPECT. In total, 57 lung lobes were affected. P-SPECT/CT significantly (p < 0.01) overdiagnosed embolism in nonaffected patients. In total, 36 cases with 88 affected lung lobes were shown. The sensitivity was 95.8%, the specificity 82.6%, the false-negative rate 4.2% and the false-positive rate 17.3%. Conclusions: Our results demonstrate that a nonenhanced CT scan in a novel hybrid imaging system cannot replace V-SPECT in the scintigraphy-based diagnosis of PE. V-SPECT increases specificity and reduces the number of false-positive results when compared to ‘perfusion-only' SPECT/CT.

Software-Based Hybrid Perfusion SPECT/CT Provides Diagnostic Accuracy When Other Pulmonary Embolism Imaging Is Indeterminate

“…This is especially advantageous when CTPA and routine V/Q scans are indeterminate/ nondiagnostic. Some authors have reported that V/Q SPECT or V/Q SPECT/CT is superior to Q SPECT/CT alone in diagnosing PE [34,35]. In some scenarios, adding V SPECT would be helpful for more accurate diagnosis: for example, asthma exacerbations, hypoxic vasoconstrictive responses to reduced ventilation and some obstructive airway diseases can show perfusion defects without CT abnormalities and may cause a false-positive diagnosis of PE on Q SPECT/CT.…”

Lung scintigraphy in differential diagnosis of peripheral lung cancer and community-acquired pneumonia

“…Main cause of challenges consists in similarity of clinical presentation of CAP and other diseases manifesting with development of infiltrative processes in the lungs (malignant neoplasms, infiltrative pulmonary tuberculosis, pulmonary embolism, etc.) [3][4][5][6]. The process for developing a differential diagnosis between CAP and peripheral lung cancer is associated with particular difficulties [3].…”

“…Due to this, radionuclide methods of study are of special interest for clinicians because they allow for evaluating not only anatomical structures, but also functional features of the pathological process in respiratory organs [5,8,9].…”

“…Radionuclide pulmonary studies proved their diagnostic value in pulmonary embolism and in nonspecific acute and chronic lung diseases [2,5,10]. Noninvasiveness, relatively low radiation exposure, convenience for patients, and comparative simplicity of the procedure allow for administering this study even at an outpatient stage [11].…”

“…The weight of evidence suggests that ventilation/perfusion scintigraphy may be considered an essential approach for acquiring additional information in establishing the differential diagnosis at a stage of infiltrative changes in pulmonary parenchyma in CAP and in peripheral lung cancer [5,8,9].…”