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Original Research: Pulmonary Vascular Disease |

Noncontrast Perfusion Single-Photon Emission CT/CT ScanningA New Test for the Diagnosis of Pulmonary Embolism: A New Test for the Expedited, High-Accuracy Diagnosis of Acute Pulmonary Embolism FREE TO VIEW

Yang Lu, MD, PhD; Alice Lorenzoni, MD; Josef J. Fox, MD; Jürgen Rademaker, MD; Nicholas Vander Els, MD; Ravinder K. Grewal, MD; H. William Strauss, MD; Heiko Schöder, MD
Author and Funding Information

From the Molecular Imaging and Therapy Service (Drs Lu, Lorenzoni, Fox, Grewal, Strauss, and Schöder) and Body Imaging Section (Dr Rademaker), Department of Radiology and Pulmonary Disease Service (Dr Vander Els), Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY.

Correspondence to: Heiko Schöder, MD, Molecular Imaging and Therapy Service, Memorial Sloan-Kettering Cancer Center, 1275 York Ave, New York, NY 10065; e-mail: schoderh@mskcc.org


Dr Lu is currently at the University of Illinois Hospital and Health Sciences System (Chicago, IL).

Dr Lorenzoni is currently at the University of Pisa (Pisa, Italy).

Funding/Support: The authors have reported to CHEST that no funding was received for this study.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2014;145(5):1079-1088. doi:10.1378/chest.13-2090
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Background:  Standard ventilation and perfusion (V˙/Q˙ ) scintigraphy uses planar images for the diagnosis of pulmonary embolism (PE). To evaluate whether tomographic imaging improves the diagnostic accuracy of the procedure, we compared noncontrast perfusion single-photon emission CT (Q˙ -SPECT)/CT scans with planar V˙/Q˙ scans in patients at high risk for PE.

Methods:  Between 2006 and 2010, most patients referred for diagnosis of PE underwent both Q˙ -SPECT/CT scan and planar V˙/Q˙ scintigraphy. All scans were reviewed retrospectively by four observers; planar scans were read with modified Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) II and Prospective Investigative Study of Pulmonary Embolism Diagnosis (PISA-PED) criteria. On Q˙ -SPECT/CT scan, any wedge-shaped peripheral perfusion defect occupying > 50% of a segment without corresponding pulmonary parenchymal or pleural disease was considered to show PE. The final diagnosis was established with a composite reference standard that included ECG, ultrasound of lower-extremity veins, D-dimer levels, CT pulmonary angiography (when available), and clinical follow-up for at least 3 months.

Results:  One hundred six patients with cancer and mean Wells score of 4.4 had sufficient follow-up; 22 patients were given a final diagnosis of PE, and 84 patients were given a final diagnosis of no PE. According to PIOPED II, 13 studies were graded as intermediate probability. Sensitivity and specificity for PE were 50% and 98%, respectively, based on PIOPED II criteria; 86% and 93%, respectively, based on PISA-PED criteria; and 91% and 94%, respectively, based on Q˙ -SPECT/CT scan. Seventy-six patients had additional relevant findings on the CT image of the Q˙ -SPECT/CT scan.

Conclusions:  Noncontrast Q˙ -SPECT/CT imaging has a higher accuracy than planar V˙/Q˙ imaging based on PIOPED II criteria in patients with cancer and a high risk for PE.

Figures in this Article

The annual incidence of acute pulmonary embolism (PE) ranges from 23 to 69 cases per 100,000 people.1,2 Approximately 5% of patients discharged from a medical service (many with cancer) present with symptomatic DVT or PE within 90 days3 of discharge. A review of data from 1979 to 1998 reported an age-adjusted death rate for PE of 94 per 1,000,000 individuals.4 Anticoagulant therapy can reduce the risk of death, but unnecessary anticoagulation therapy can increase the risk of bleeding.

Patients with acute PE may present with a wide spectrum of symptoms. Those with a moderate or high likelihood for PE, established by modified Wells criteria or the simplified revised Geneva score (e-Tables 1, 2), usually undergo imaging tests to substantiate the clinical impression. Multidetector CT pulmonary angiography (CTPA) provides direct visualization of clots (filling defects) in the pulmonary arteries5 and has become the preferred test for detecting PE in many institutions.69 However, CTPA is contraindicated in patients with renal insufficiency, multiple myeloma, or allergy to IV contrast. Radionuclide imaging of lung ventilation and perfusion (V˙/Q˙ ) offers an alternative approach to the diagnosis of PE in these patients.1014 Furthermore, concerns regarding the high radiation dose from CTPA (approximately 15 mSv), particularly in women (breast organ dose) and young individuals, have led to a resurgence of V˙/Q˙ scintigraphy in some institutions.15 A typical V˙/Q˙ scan in the United States delivers only 2.2 mSv. The widely used Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) criteria for interpretation of V˙/Q˙ scans compare the size of a perfusion abnormality to the size of a radiographic or ventilation abnormality on planar images.12 However, the limited angular sampling and overlap of structures in planar images make it difficult to compare regional ventilation to regional perfusion (especially in patients with significant airway disease). As a result, up to one-third of V˙/Q˙ scans are considered indeterminate.13 Furthermore, V˙/Q˙ scans are lengthy procedures, lasting upward of 45 min, which may be prohibitive for unstable or disoriented patients. The Prospective Investigative Study of Pulmonary Embolism Diagnosis (PISA-PED) criteria have been suggested as a simplified approach to the scintigraphic evaluation of PE, using only the shape and location of defects on planar perfusion scans and eliminating ventilation imaging.16V˙/Q˙ single-photon emission CT (SPECT) imaging may have greater sensitivity and specificity than planar imaging for the detection of PE.1721 In some studies, V˙/Q˙ SPECT imaging and CTPA performed with similar overall accuracy: V˙/Q˙ SPECT imaging showed relatively high sensitivity, and CTPA showed relatively high specificity.22

The growing availability of hybrid SPECT/CT scanners offers a novel approach to detect PE.23 SPECT imaging performed in conjunction with a coregistered low-dose CT scan can directly assess the architecture of the airways, lung parenchyma, and pleural space in relation to the overlaid perfusion images. In theory, areas of decreased perfusion without corresponding structural abnormality are likely to represent a PE. We hypothesized that perfusion SPECT (Q˙ -SPECT)/CT imaging provides greater overall accuracy for the diagnosis of PE than traditional V˙/Q˙ scintigraphy while reducing the number of nondiagnostic studies. To test this hypothesis, we retrospectively compared the performance characteristics of simultaneously performed Q˙ -SPECT/CT scans and planar V˙/Q˙ scans in patients with at least 3 months of follow-up.

Patients

This retrospective study was approved by the Memorial Sloan-Kettering Cancer Center Institutional Review Board/Privacy Board with a waiver of authorization (Project approval number: WA0294-09); patient consent was not required). All patients referred for V˙/Q˙ scans to assess for PE from 2006 to 2010 in our center were reviewed. Patients who underwent both planar V˙/Q˙  and Q˙ -SPECT/CT imaging on the same day, with at least 3 months of clinical follow-up, were included in this analysis. Q˙ -SPECT/CT imaging is routinely performed at our center when the camera is available. All patients had cancer.

Imaging Protocols

Planar images were recorded in standard projections with large field of view dual-detector SPECT cameras (SKYLight; Koninklijke Philips NV), using parallel-hole, high-resolution, low-energy collimators with an energy window of 20% at a center line of 140 keV. For ventilation imaging, patients inhaled a radioactive aerosol (99mTc-diethylene triamine pentaacetic acid) until the count rate in the posterior view was 1,000 counts/s (200,000 counts/view; matrix size, 512 × 512 × 16 pixels). For perfusion imaging, 4.0 mCi of 99mTc macroaggregated albumin IV was injected with the patient supine during tidal respiration.

Q˙ -SPECT/CT imaging data were recorded with the Philips Precedence SPECT/CT scanning system. Low-dose CT scans were recorded at 120 kVp, 15 to 30 mAs, without IV contrast during continuous tidal respiration (3-mm slice thickness). Following the CT scan, SPECT images of the chest were recorded for 20 s/step, with 3° steps, in a 128 × 128 matrix. Q˙ -SPECT imaging data were reconstructed with an iterative ordered subset expectation maximization algorithm. The resulting images were displayed in transaxial, coronal, and sagittal planes and were fused with the corresponding CT image slices.

Image Interpretation and Final Diagnosis

Images were interpreted on an integrated GE PACS AW Suite workstation (General Electric Company). Three nuclear medicine physicians with 3, 4, and > 30 years experience in V˙/Q˙ scan interpretation read the 106 sets of scans independently. The planar and SPECT/CT scan datasets were read on separate occasions to avoid recall bias. A fourth reader with 20 years of experience was the final arbiter of the imaging studies.

Planar scans were analyzed according to modified PIOPED II24,25 and PISA-PED16,26 criteria and categorized (e-Table 3). PIOPED II categories were (1) PE present (high-probability V˙/Q˙ scan), (2) PE absent (normal or very-low-probability V˙/Q˙ scans), and (3) nondiagnostic (all other findings). PISA-PED categories were (1) PE present (abnormal perfusion scan compatible with PE [ie, wedge-shaped defect]), (2) PE absent (normal, near-normal, abnormal perfusion scan not compatible with PE [ie, defects other than peripheral and wedge shaped]), and (3) nondiagnostic (cannot classify as PE present or absent).

Q˙ -SPECT/CT scans were interpreted independently of the planar images in a binary fashion. PE present indicated at least one wedge-shaped peripheral defect estimated as ≥ 50% of a pulmonary segment27 without corresponding CT image abnormality and clearly seen in all three orthogonal planes (Fig 1).28 In addition, to account for commonly encountered inhomogeneities in intensity, we required macroaggregated albumin uptake to be visually reduced by > 70% compared with normally perfused lung. PE absent indicated any perfusion defect with a corresponding CT image abnormality (eg, mass, consolidation, effusion, emphysema, fibrosis) or perfusion defects involving < 50% of a segment without a corresponding abnormality on CT scan. Slight irregularities of the outer lung contours are frequently seen on Q˙ -SPECT images and may be secondary to respiration during image acquisition.

Figure Jump LinkFigure 1. Concordant planar ventilation and perfusion single-photon emission CT (Q˙ -SPECT)/CT image study. A, Planar PERF images in the ANT, POST, RAO and LAO, and RPO and LPO projections (arrows indicate perfusion defects). B, Planar VENT images in the ANT, POST, RAO and LAO, and RPO and LPO projections. C, Single-photon emission CT (SPECT) image, fused SPECT/CT image, and CT image (top to bottom) perfusion images in the coronal, sagittal, and axial planes (left to right). Planar perfusion images show multiple wedge-shaped defects; the ventilation study is normal except for a minor linear reduction in the region of the right-side oblique fissure. The planar images are consistent with a high probability for pulmonary embolism (based on Prospective Investigation of Pulmonary Embolism Diagnosis [PIOPED] II criteria) or a pulmonary embolism present pattern (based on Prospective Investigative Study of Pulmonary Embolism Diagnosis criteria). Q˙ -SPECT images show several characteristic pleural-based wedge-shaped perfusion defects without associated parenchymal abnormality on the coregistered CT scan (mismatched). ANT = anterior; LAO = left anterior oblique; LPO = left posterior oblique; PERF = perfusion; POST = posterior; RAO = right anterior oblique; RPO = right posterior oblique; VENT = ventilation.Grahic Jump LocationGrahic Jump Location

A chest radiologist independently reviewed the low-dose CT scans and recorded all pulmonary and pleural abnormalities. A clinical pulmonologist independently reviewed the clinical and laboratory data to determine the pretest likelihood for PE. The ultimate confirmation or exclusion of PE (ie, final diagnosis) was determined by consensus of the pulmonologist and the imaging arbiter who used a composite of all clinical information, including ECG, D-dimer levels, physical examination, lower-extremity Doppler echocardiography studies, and other imaging studies as well as a clinical follow-up of at least 3 months.

Statistical Analyses

The characteristics of the study population were expressed as the mean ± SD. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated as the evaluation of diagnostic performance. Interobserver agreement was evaluated with the κ test. Statistical analyses were performed with SPSS, version 19.0 (IBM) software.

During the study period, 107 patients underwent both planar V˙/Q˙  and Q˙ -SPECT/CT imaging. One patient was excluded from analysis because of insufficient follow-up. Among the remaining 106 patients, 47 were men (mean age, 63 years; range, 27-91 years), and 59 were women (mean age, 63.7 years; range, 31-92 years). The primary modality for evaluation of PE in our institution is CTPA. Most patients in the current study were referred for a V˙/Q˙  scan as a result of acute or chronic renal insufficiency with a creatinine level > 1.4 mg/dL (n = 49), contraindication to IV contrast (n = 36, wherein 33 patients were allergic to IV contrast, two had multiple myeloma, and one had paroxysmal nocturnal hemoglobinuria), or equivocal findings on CTPA (n = 8; interval between CTPA and V˙/Q˙ imaging, 4 days [range, 0-20 days]). All patients had a history of cancer. The mean Wells score29 was 4.4 ± 2.5 (range, 1.0-8.5). Based on our composite standard of reference, PE was ultimately confirmed in 22 patients and excluded in 84. Q˙ -SPECT imaging showed abnormalities in 20 of 22 patients (91%) and PISA-PED and PIOPED II criteria were met in 19 of 22 (86%) and 11 of 22 (50%), respectively. Based on PIOPED II criteria, 13 V˙/Q˙  scans (12.3%) were considered nondiagnostic; PE was ultimately confirmed in seven and excluded in six of these patients. Based on PISA-PED criteria and Q˙ -SPECT/CT imaging, none of the perfusion scans was considered nondiagnostic. The diagnostic performance of Q˙ -SPECT/CT imaging vs planar V˙/Q˙  scanning is further detailed in Table 1. Representative cases are shown in Figures 1 and 2. Interobserver agreement was moderate for planar scans (κ = 0.624, P < .001) and good for Q˙ -SPECT/CT scans (κ = 0.827, P < .001).

Table Graphic Jump Location
Table 1 —Diagnostic Performance of Various Techniques and Interpretation Criteria for Detection of PE

Data are presented as No. and absolute No. (95% CI). N/A = not applicable; NPV = negative predictive value; NS = not significant; PE = pulmonary embolism; PIOPED = Prospective Investigation of Pulmonary Embolism Diagnosis; PISA-PED = Prospective Investigative Study of Pulmonary Embolism Diagnosis; PPV = positive predictive value; Q˙ -SPECT = perfusion single-photon emission CT.

a 

P < .001 for sensitivity, NPV, and accuracy of Q˙ -SPECT scan vs PIOPED II criteria; P = NS for Q˙ -SPECT scan vs PISA-PED criteria.

b 

Denominator includes indeterminate scans because final diagnosis was established for all cases. Note the artificially high specificity of PIOPED II criteria, which reflects the fact that 13 scans were nondiagnostic.

Figure Jump LinkFigure 2. Clarification of indeterminate PIOPED II findings by SPECT/CT scan. A, Planar PERF images in the ANT, POST, RAO and LAO, and RPO and LPO show absent or severely decreased perfusion in the right lung apex (arrows indicate right apical perfusion defect). B, Planar VENT in the ANT, POST, RAO and LAO, and RPO and LPO (left to right). Normal ventilation in the apical segment of the right upper lobe is consistent with an intermediate probability for pulmonary embolism based on PIOPED II criteria. C, SPECT, fused SPECT/CT, and CT (top to bottom) perfusion images in the coronal, sagittal, and axial planes (left to right) show characteristic mismatched perfusion defect, upgrading the diagnosis to pulmonary embolism present. See Figure 1 legend for expansion of abbreviations.Grahic Jump LocationGrahic Jump Location

The low-dose CT scan was entirely normal in only 30 patients. In the remaining 76 patients, the CT scan provided additional diagnostic information, including pleural or pericardial effusions (n = 32), emphysema (n = 4), areas of postradiation fibrosis (n = 3), areas of consolidation (including atelectasis and pneumonia) (n = 15), nodules or masses (n = 21), other small opacities (n = 11), interstitial lung disease (n = 1), hilar lymphadenopathy (n = 1), chest wall mass (n = 1), and unilateral lung collapse (n = 1). Several patients had more than one of these findings (Fig 3).

Figure Jump LinkFigure 3. Q˙ -SPECT/CT images that do not show a pulmonary embolus but, instead, demonstrate incidental moderate-sized pericardial effusion and lung metastasis. A and B, Coronal and axial perfusion SPECT image slices show an enlarged cardiac silhouette. C and D, Axial CT image and fused SPECT/CT image show pericardial (arrowheads) and trace pleural effusions. E, A low-dose CT scan also reveals a metastasis from melanoma in right-side lung (arrow). See Figure 1 legend for expansion of abbreviations.Grahic Jump Location

This study demonstrates that Q˙ -SPECT/CT imaging has a higher diagnostic accuracy than conventional V˙/Q˙  planar imaging interpreted according to PIOPED II criteria (P < .001), with a substantially reduced number of false-negative and nondiagnostic scans. We also show that interpretation of Q˙ -SPECT/CT imaging is more reproducible among readers than planar imaging. By forcing a binary interpretation of PE present or PE absent, we conform to a trend in the literature attempting to simplify the interpretation of lung scintigraphy.30,31

A major limitation of the PIOPED criteria is the notoriously high rate of indeterminate scans, remaining as high as 17% for modified PIOPED II reads.24 PISA-PED criteria set the precedent for eliminating the ventilation scan, relying only on the shape and location of perfusion abnormalities, and in doing so, reduced the complexity of lung scintigraphy.16 In the present study, Q˙ -SPECT/CT scanning marginally outperformed PISA-PED interpretation. A distinct advantage of Q˙ -SPECT/CT scanning, however, is the anatomic information provided by the accompanying low-dose CT scan. Perfusion changes secondary to parenchymal conditions may mimic perfusion defects related to PE. Q˙ -SPECT/CT scanning leverages the integration of three-dimensional spatial information of function and structure to directly elucidate the cause of the perfusion defect. The low-dose CT scan readily shows nonembolic causes of abnormal perfusion, such as masses, effusions, and consolidations. This is particularly relevant for an elderly population or for patients with cancer in whom chest radiographs frequently are abnormal. Of note, studies reporting high accuracy for diagnosing PE with planar imaging only included patients with normal or near-normal chest radiographs.31 Moreover, although the purpose of V˙/Q˙ scanning aims primarily at diagnosing or excluding PE, a normal scan may be less clinically useful than is commonly believed, for even after PE is excluded with reasonable certainty, further workup may be needed to address the patient’s symptoms. The low-dose CT scan not only replaces the chest radiograph but also may reveal important structural abnormalities that would otherwise go undetected. In the present cohort, the low-dose CT scan exhibited additional diagnostic findings in approximately 72% of patients, providing in many instances a sufficient alternative explanation for the presenting symptoms (eg, infectious process, large effusions). The relatively high proportion of additional diagnostic findings on the low-dose CT scan in the present study (eg, compared with 21% in the study by van Belle et al6) probably reflects that we exclusively image patients with cancer. Notwithstanding, CT scan abnormalities related to pulmonary infarction may lead to false-negative interpretations of Q˙ -SPECT/CT scans.

An additional advantage of Q˙ -SPECT/CT imaging is reduced scan time. Planar V˙/Q˙ imaging requires approximately 45 min, whereas Q˙ -SPECT/CT imaging takes roughly one-half the amount of time (approximately 22 min). The total radiation exposure from a Q˙ -SPECT/CT scan is approximately 3.5 mSv, which is only 1.5 mSv more than a perfusion scan alone and only 1.2 mSv more than a V˙/Q˙ scan combined with a chest radiograph. By comparison, the radiation dose of a CTPA study (15 mSv) is more than fourfold larger than a complete Q˙ -SPECT/CT scanning procedure (e-Table 4).32

The specificity for Q˙ -SPECT/CT scanning in the present study was significantly higher than previously reported by Gutte et al33 possibly because we took into account both the size (minimum 50% of a segment) and the severity of a perfusion defect. Although the addition of ventilation SPECT scanning substantially improved on the specificity of Q˙ -SPECT/CT scanning in the aforementioned study (an increase from 51% to 100%), the incremental benefit in the present cohort would only be minimal in view of the already high specificity (94%) with Q˙ -SPECT/CT scanning alone. In our opinion, this minimal potential benefit does not warrant the added radiation dose and scan time necessitated by the ventilation scan.

Limitations of this study include its retrospective nature and the institutional preference for CTPA. An intrinsic problem with many retrospective studies is the lack of a clear gold standard. However, selective pulmonary angiography, the traditional gold standard, has been replaced de facto by CTPA, and most patients in this study were referred for V˙/Q˙ scintigraphy because they were ineligible for CTPA. We used a composite clinical outcome as our measure of reference for the diagnosis of PE, which included all clinical information, other imaging studies, and patient outcome. Similar composite references were used by Gutte et al33 and Glaser et al.31

There may have been patient referral bias in that the majority of patients at our institution continue to undergo CTPA when PE is clinically suspected. Thus, the data are based on a group of patients ineligible for CTPA or with equivocal findings on CTPA.

The prevalence of PE in the present study population is higher than that reported from other studies. For instance, Glaser et al31 reported a prevalence of about 8.4% compared with 20% in the current study. This higher prevalence possibly reflects a combination of the relatively high pretest probability in a cancer center (based on Wells score) and largely appropriate patient selection by referring physicians.

There may have been verification bias such that in clinical practice, decisions often are based on probability. If the risk of and probability for PE is sufficiently high, patients receive thrombolytic therapy.5 Our composite standard of reference considered all available evidence, and in clinical practice, the interpretation of the original V˙/Q˙  scans would have influenced clinical decision-making. However, this bias is present in most of the prior studies on this subject. Our minimum follow-up time was similar to that in prior studies.6,31

Finally, the population in the present study is highly selected (eg, patients with cancer), and further testing is required to determine whether the results can be extrapolated to the general population. Nevertheless, the high prevalence of parenchymal and pleural disease in this patient population would, if anything, be expected to complicate the interpretation of both planar and SPECT/CT images. Therefore, we believe that Q˙ -SPECT/CT scanning will perform with even greater accuracy in the general population, as seen in most EDs across the United States.

In conclusion, this study suggests that Q˙ -SPECT/CT scanning has high diagnostic accuracy for detecting PE in a cancer population and may be ready to supplant traditional planar V˙/Q˙ scintigraphy. The accompanying low-dose CT scan yields clinically relevant information in the majority of cases. Prospective validation by multiple investigators and head-to-head comparison with CTPA are required before Q˙ -SPECT/CT scanning can be firmly recommended for the general population.

Author contributions: Dr Schöder had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Dr Lu: contributed to the study concept and design; data acquisition, analysis, and interpretation; and drafting, critical revision for important intellectual content, and final approval of the manuscript.

Dr Lorenzoni: contributed to the study concept and design; data acquisition, analysis, and interpretation; and drafting, critical revision for important intellectual content, and final approval of the manuscript.

Dr Fox: contributed to the study concept and design; data acquisition, analysis, and interpretation; and drafting, critical revision for important intellectual content, and final approval of the manuscript.

Dr Rademaker: contributed to the study concept and design; data acquisition, analysis, and interpretation; and drafting, critical revision for important intellectual content, and final approval of the manuscript.

Dr Vander Els: contributed to the study concept and design; data acquisition, analysis, and interpretation; and drafting, critical revision for important intellectual content, and final approval of the manuscript.

Dr Grewal: contributed to the study concept and design; data acquisition, analysis, and interpretation; and drafting, critical revision for important intellectual content, and final approval of the manuscript.

Dr Strauss: contributed to the study concept and design; data acquisition, analysis, and interpretation; and drafting, critical revision for important intellectual content, and final approval of the manuscript.

Dr Schöder: contributed to the study concept and design; data acquisition, analysis, and interpretation; and drafting, critical revision for important intellectual content, and final approval of the manuscript.

Financial/nonfinancial disclosures: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Additional information: The e-Tables can be found in the “Supplemental Materials” area of the online article.

CTPA

CT pulmonary angiography

PE

pulmonary embolism

PIOPED

Prospective Investigation of Pulmonary Embolism Diagnosis

PISA-PED

Prospective Investigative Study of Pulmonary Embolism Diagnosis

Q˙ -SPECT

perfusion single-photon emission CT

SPECT

single-photon emission CT

V˙/Q˙ 

ventilation and perfusion

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Sostman HD, Miniati M, Gottschalk A, Matta F, Stein PD, Pistolesi M. Sensitivity and specificity of perfusion scintigraphy combined with chest radiography for acute pulmonary embolism in PIOPED II. J Nucl Med. 2008;49(11):1741-1748. [CrossRef] [PubMed]
 
Sostman HD, Stein PD, Gottschalk A, Matta F, Hull R, Goodman L. Acute pulmonary embolism: sensitivity and specificity of ventilation-perfusion scintigraphy in PIOPED II study. Radiology. 2008;246(3):941-946. [CrossRef] [PubMed]
 
Miniati M, Sostman HD, Gottschalk A, Monti S, Pistolesi M. Perfusion lung scintigraphy for the diagnosis of pulmonary embolism: a reappraisal and review of the Prospective Investigative Study of Acute Pulmonary Embolism Diagnosis methods. Semin Nucl Med. 2008;38(6):450-461. [CrossRef] [PubMed]
 
Howarth DM, Booker JA, Voutnis DD. Diagnosis of pulmonary embolus using ventilation/perfusion lung scintigraphy: more than 0.5 segment of ventilation/perfusion mismatch is sufficient. Intern Med J. 2006;36(5):281-288. [CrossRef] [PubMed]
 
Lu Y, Fox JJ. Acute pulmonary embolism detected by perfusion SPECT/CT masquerading as an intermediate probability planar V/Q scan. Clin Nucl Med. 2010;35(12):941-943. [CrossRef] [PubMed]
 
Wells PS, Anderson DR, Rodger M, et al. Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer. Ann Intern Med. 2001;135(2):98-107. [CrossRef] [PubMed]
 
Bajc M, Neilly JB, Miniati M, Schuemichen C, Meignan M, Jonson B. EANM guidelines for ventilation/perfusion scintigraphy: Part 2. Algorithms and clinical considerations for diagnosis of pulmonary emboli with V/P(SPECT) and MDCT. Eur J Nucl Med Mol Imaging. 2009;36(9):1528-1538. [CrossRef] [PubMed]
 
Glaser JE, Chamarthy M, Haramati LB, Esses D, Freeman LM. Successful and safe implementation of a trinary interpretation and reporting strategy for V/Q lung scintigraphy. J Nucl Med. 2011;52(10):1508-1512. [CrossRef] [PubMed]
 
Mettler FA Jr, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology. 2008;248(1):254-263. [CrossRef] [PubMed]
 
Gutte H, Mortensen J, Jensen CV, et al. Detection of pulmonary embolism with combined ventilation-perfusion SPECT and low-dose CT: head-to-head comparison with multidetector CT angiography. J Nucl Med. 2009;50(12):1987-1992. [CrossRef] [PubMed]
 

Figures

Figure Jump LinkFigure 1. Concordant planar ventilation and perfusion single-photon emission CT (Q˙ -SPECT)/CT image study. A, Planar PERF images in the ANT, POST, RAO and LAO, and RPO and LPO projections (arrows indicate perfusion defects). B, Planar VENT images in the ANT, POST, RAO and LAO, and RPO and LPO projections. C, Single-photon emission CT (SPECT) image, fused SPECT/CT image, and CT image (top to bottom) perfusion images in the coronal, sagittal, and axial planes (left to right). Planar perfusion images show multiple wedge-shaped defects; the ventilation study is normal except for a minor linear reduction in the region of the right-side oblique fissure. The planar images are consistent with a high probability for pulmonary embolism (based on Prospective Investigation of Pulmonary Embolism Diagnosis [PIOPED] II criteria) or a pulmonary embolism present pattern (based on Prospective Investigative Study of Pulmonary Embolism Diagnosis criteria). Q˙ -SPECT images show several characteristic pleural-based wedge-shaped perfusion defects without associated parenchymal abnormality on the coregistered CT scan (mismatched). ANT = anterior; LAO = left anterior oblique; LPO = left posterior oblique; PERF = perfusion; POST = posterior; RAO = right anterior oblique; RPO = right posterior oblique; VENT = ventilation.Grahic Jump LocationGrahic Jump Location
Figure Jump LinkFigure 2. Clarification of indeterminate PIOPED II findings by SPECT/CT scan. A, Planar PERF images in the ANT, POST, RAO and LAO, and RPO and LPO show absent or severely decreased perfusion in the right lung apex (arrows indicate right apical perfusion defect). B, Planar VENT in the ANT, POST, RAO and LAO, and RPO and LPO (left to right). Normal ventilation in the apical segment of the right upper lobe is consistent with an intermediate probability for pulmonary embolism based on PIOPED II criteria. C, SPECT, fused SPECT/CT, and CT (top to bottom) perfusion images in the coronal, sagittal, and axial planes (left to right) show characteristic mismatched perfusion defect, upgrading the diagnosis to pulmonary embolism present. See Figure 1 legend for expansion of abbreviations.Grahic Jump LocationGrahic Jump Location
Figure Jump LinkFigure 3. Q˙ -SPECT/CT images that do not show a pulmonary embolus but, instead, demonstrate incidental moderate-sized pericardial effusion and lung metastasis. A and B, Coronal and axial perfusion SPECT image slices show an enlarged cardiac silhouette. C and D, Axial CT image and fused SPECT/CT image show pericardial (arrowheads) and trace pleural effusions. E, A low-dose CT scan also reveals a metastasis from melanoma in right-side lung (arrow). See Figure 1 legend for expansion of abbreviations.Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1 —Diagnostic Performance of Various Techniques and Interpretation Criteria for Detection of PE

Data are presented as No. and absolute No. (95% CI). N/A = not applicable; NPV = negative predictive value; NS = not significant; PE = pulmonary embolism; PIOPED = Prospective Investigation of Pulmonary Embolism Diagnosis; PISA-PED = Prospective Investigative Study of Pulmonary Embolism Diagnosis; PPV = positive predictive value; Q˙ -SPECT = perfusion single-photon emission CT.

a 

P < .001 for sensitivity, NPV, and accuracy of Q˙ -SPECT scan vs PIOPED II criteria; P = NS for Q˙ -SPECT scan vs PISA-PED criteria.

b 

Denominator includes indeterminate scans because final diagnosis was established for all cases. Note the artificially high specificity of PIOPED II criteria, which reflects the fact that 13 scans were nondiagnostic.

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Sostman HD, Miniati M, Gottschalk A, Matta F, Stein PD, Pistolesi M. Sensitivity and specificity of perfusion scintigraphy combined with chest radiography for acute pulmonary embolism in PIOPED II. J Nucl Med. 2008;49(11):1741-1748. [CrossRef] [PubMed]
 
Sostman HD, Stein PD, Gottschalk A, Matta F, Hull R, Goodman L. Acute pulmonary embolism: sensitivity and specificity of ventilation-perfusion scintigraphy in PIOPED II study. Radiology. 2008;246(3):941-946. [CrossRef] [PubMed]
 
Miniati M, Sostman HD, Gottschalk A, Monti S, Pistolesi M. Perfusion lung scintigraphy for the diagnosis of pulmonary embolism: a reappraisal and review of the Prospective Investigative Study of Acute Pulmonary Embolism Diagnosis methods. Semin Nucl Med. 2008;38(6):450-461. [CrossRef] [PubMed]
 
Howarth DM, Booker JA, Voutnis DD. Diagnosis of pulmonary embolus using ventilation/perfusion lung scintigraphy: more than 0.5 segment of ventilation/perfusion mismatch is sufficient. Intern Med J. 2006;36(5):281-288. [CrossRef] [PubMed]
 
Lu Y, Fox JJ. Acute pulmonary embolism detected by perfusion SPECT/CT masquerading as an intermediate probability planar V/Q scan. Clin Nucl Med. 2010;35(12):941-943. [CrossRef] [PubMed]
 
Wells PS, Anderson DR, Rodger M, et al. Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer. Ann Intern Med. 2001;135(2):98-107. [CrossRef] [PubMed]
 
Bajc M, Neilly JB, Miniati M, Schuemichen C, Meignan M, Jonson B. EANM guidelines for ventilation/perfusion scintigraphy: Part 2. Algorithms and clinical considerations for diagnosis of pulmonary emboli with V/P(SPECT) and MDCT. Eur J Nucl Med Mol Imaging. 2009;36(9):1528-1538. [CrossRef] [PubMed]
 
Glaser JE, Chamarthy M, Haramati LB, Esses D, Freeman LM. Successful and safe implementation of a trinary interpretation and reporting strategy for V/Q lung scintigraphy. J Nucl Med. 2011;52(10):1508-1512. [CrossRef] [PubMed]
 
Mettler FA Jr, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology. 2008;248(1):254-263. [CrossRef] [PubMed]
 
Gutte H, Mortensen J, Jensen CV, et al. Detection of pulmonary embolism with combined ventilation-perfusion SPECT and low-dose CT: head-to-head comparison with multidetector CT angiography. J Nucl Med. 2009;50(12):1987-1992. [CrossRef] [PubMed]
 
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