Critical review of SPECT imaging in pulmonary embolism

Abstract

Outcome studies have shown that pulmonary embolism can be safely excluded in patients with negative ventilation/perfusion (V/Q) single-photon emission computed tomography (SPECT). The effective radiation dose of V/Q SPECT is much less than with computed tomographic (CT) pulmonary angiography, which would make it preferable to CT angiography in many young female patients. The accuracy of V/Q SPECT, however, is difficult to assess, because most published investigations are limited by incorporation bias or partial verification bias, as well as other limitations in study design and reporting. Consequently, the accuracy of V/Q SPECT relative to planar V/Q scintigraphy or CT angiography has not been definitively determined. There is need for a prospective investigation of the accuracy of V/Q SPECT with consecutive patients, blinded interpretations, and an independent reference standard, or independent composite reference standard.Keywords Pulmonary embolism Á Venous thromboembolism Á Single-photon emission computed tomography Since the publication of the prospective investigation of pulmonary embolism diagnosis (PIOPED) in 1990 [1], there has been a decline in the use of ventilation/perfusion (V/Q) planar scintigraphy [2] and widespread adoption of computed tomographic (CT) pulmonary angiography for the diagnosis of acute pulmonary embolism (PE) [2]. The development of tomographic radionuclide imaging presents diagnostic possibilities that were not available at the time of publication of the PIOPED. In 2009, together with colleagues, we reviewed the use of single-photon emission computed tomography (SPECT) in acute PE [3]. Numerous observations with SPECT in the 5 years since then prompted us to conduct the present review of its potential role in evaluating patients with PE. One aim of this review is to present data that will allow physicians to make informed choices regarding the use of SPECT in patients with suspected PE.We searched PubMed using the following search terms: SPECT PE matched with accuracy (20 results), sensitivity (34 results), specificity (39 results); SPECT pulmonary embolism matched with accuracy (35 results), sensitivity (78 results), specificity (80 results); single-photon emission computed tomography pulmonary embolism matched with accuracy (30 results), sensitivity (71 results), specificity (72 results); single-photon emission computed tomography pulmonary embolism (174 results); SPECT pulmonary embolism (197 results). We also checked the references of relevant studies to identify additional investigations. The inclusion criteria were: studies in all languages related to the accuracy of SPECT that included [10 patients suspected of having acute PE and showed or allowed the reader to calculate sensitivity, specificity, and results of clinical follow-up. We identified 21 such articles and 2 preliminary articles with fewer patients that were of interest. Some addressed more than one topic.

Ventilation/perfusion SPECT for the diagnosis of pulmonary embolism: A systematic review

“…41 However, they have incorporated into the meta-analysis studies judged as having a high risk of bias, especially studies with an incorporation bias. 44 Surprisingly, although V/Q SPECT has been widely adopted in nuclear medicine departments in daily clinical practice, no management outcome study or clinical trial has been published.…”

“…A few systematic reviews and meta‐analyses on the diagnostic accuracy of V/Q SPECT have been published 41‐43 and concluded that V/Q SPECT was superior to planar imaging 41 and superior 43 or equal to CTPA 41 . However, they have incorporated into the meta‐analysis studies judged as having a high risk of bias, especially studies with an incorporation bias 44 …”

Pulmonary Scintigraphy for the Diagnosis of Acute Pulmonary Embolism: A Survey of Current Practices in Australia, Canada, and France

“…Furthermore, V/Q SPECT has not achieved the same standard of validation as others diagnostic tests including planar V/Q imaging (1,6-9), CTPA (28-30), or D-dimer testing (31,32), which may impede its widespread acceptance by clinicians. Indeed, although there is an extensive literature reporting the superior diagnostic performances of V/Q SPECT as compared with V/Q planar, the exact accuracy of V/Q SPECT for PE diagnosis is still unknown (20,23). Most importantly, although all diagnostic tests and strategies (including CTPA, planar V/Q, or Ddimer) for PE diagnosis have been validated in large management outcome studies, such a study with V/Q SPECT is still lacking.…”

“…Although V/Q SPECT has many proponents within the nuclear medicine community, publications from nonnuclear medicine specialists often still focus on planar imaging, in particular referring to its high rate of nondiagnostic examinations (21,22). Some have described V/Q SPECT as a new technology requiring definitive validation (10,23). Indeed, a large management outcome study based on the V/Q SPECT for PE diagnosis is lacking.…”