Background
Ventilation/perfusion (V/Q) single‐photon emission computed tomography (SPECT) has largely replaced conventional planar V/Q scan in nuclear medicine departments for pulmonary embolism (PE) ...diagnosis. However, the diagnostic performance of the test and its role in the diagnostic management of acute PE are still a matter of debate.
Objective
The primary aim was to establish the diagnostic accuracy (sensitivity, specificity) of V/Q SPECT for PE diagnosis. The secondary aim was to review the clinical outcomes of patients investigated for PE suspicion with a standardized algorithm based on V/Q SPECT.
Methods
We conducted a systematic review of diagnostic accuracy and management outcome studies involving patients evaluated with V/Q SPECT for suspected acute PE. We searched from inception to June 23, 2020, MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials for diagnostic accuracy studies, randomized controlled trials, and observational cohort studies. The methodological quality and risk of bias of eligible studies were assessed using the Quality Assessment of Diagnostic Accuracy Studies‐2 (QUADAS‐2) and the Risk of Bias in Nonrandomized Studies of Interventions tools.
Results
We identified 13 accuracy studies and one prospective outcome study. Eleven diagnostic accuracy studies were deemed at high risk of bias in at least two of the four domains of QUADAS‐2 evaluation and a further two studies raised concerns regarding the applicability of results, precluding the meta‐analysis for accuracy indices. The only prospective cohort study demonstrated critical risk of bias.
Conclusions
Although V/Q SPECT has been widely implemented in daily clinical practice, the exact diagnostic performance of V/Q SPECT for PE is still unknown. This systematic review clearly identifies knowledge gaps and sets the agenda for future research.
Objective
To assess the diagnostic accuracy of iodine map computed tomography pulmonary angiography (CTPA), for segment-based evaluation of lung perfusion in patients with acute pulmonary embolism ...(PE), using perfusion single-photon emission CT (SPECT) imaging as a reference standard.
Methods
Thirty participants who have been diagnosed with acute pulmonary embolism on CTPA underwent perfusion SPECT/CT within 24 h. Perfusion SPECT and iodine map were independently interpreted by 2 nuclear medicine physicians and 2 radiologists. For both modalities, each segment was classified as normoperfused or hypoperfused, as defined by a perfusion defect of more than 25% of a segment. The primary end point was the diagnostic accuracy (sensitivity and specificity) of iodine map for segment-based evaluation of lung perfusion, using perfusion SPECT imaging as a reference standard. Following blinded interpretation, a retrospective explanatory analysis was performed to determine potential causes of misinterpretation.
Results
The median time between CTPA with iodine maps and perfusion SPECT was 14 h (range 2–23 h). A total of 597 segments were analyzed. Sensitivity and specificity of iodine maps with CTPA for the detection of segmental perfusion defects were 231/284 = 81.3% (95% CI 76.4 to 85.4%) and 247/313 = 78.9% (95% CI 74.1 to 83.1%), respectively. In retrospect, false results were explained in 48.7%.
Conclusion
Iodine map CTPA showed promising results for the assessment of pulmonary perfusion in patients with acute PE, with sensitivity of 81.3% and specificity of 78.9%, respectively. Recognition of typical pitfalls such as atelectasis, fissures, or beam-hardening artifacts may further improve the accuracy of the test.
Key Points
• Sensitivity and specificity of iodine subtraction maps for the detection of segmental perfusion defects were 81.3% (95% CI 76.4 to 85.4%) and 78.9% (95% CI 74.1 to 83.1%), respectively.
• Recognition of typical pitfalls such as atelectasis, fissures, or beam-hardening artifacts may further improve the diagnostic accuracy of the test.
Purpose
Point-spread function (PSF) or PSF + time-of-flight (TOF) reconstruction may improve lesion detection in oncologic PET, but can alter quantitation resulting in variable standardized uptake ...values (SUVs) between different PET systems. This study aims to validate a proprietary software tool (EQ.PET) to harmonize SUVs across different PET systems independent of the reconstruction algorithm used.
Methods
NEMA NU2 phantom data were used to calculate the appropriate filter for each PSF or PSF+TOF reconstruction from three different PET systems, in order to obtain EANM compliant recovery coefficients. PET data from 517 oncology patients were reconstructed with a PSF or PSF+TOF reconstruction for optimal tumour detection and an ordered subset expectation maximization (OSEM3D) reconstruction known to fulfil EANM guidelines. Post-reconstruction, the proprietary filter was applied to the PSF or PSF+TOF data (PSF
EQ
or PSF+TOF
EQ
). SUVs for PSF or PSF+TOF and PSF
EQ
or PSF+TOF
EQ
were compared to SUVs for the OSEM3D reconstruction. The impact of potential confounders on the EQ.PET methodology including lesion and patient characteristics was studied, as was the adherence to imaging guidelines.
Results
For the 1380 tumour lesions studied, Bland-Altman analysis showed a mean ratio between PSF or PSF+TOF and OSEM3D of 1.46 (95 %CI: 0.86–2.06) and 1.23 (95 %CI: 0.95–1.51) for SUV
max
and SUV
peak
, respectively. Application of the proprietary filter improved these ratios to 1.02 (95 %CI: 0.88–1.16) and 1.04 (95 %CI: 0.92–1.17) for SUV
max
and SUV
peak
, respectively. The influence of the different confounding factors studied (lesion size, location, radial offset and patient’s BMI) was less than 5 %. Adherence to the European Association of Nuclear Medicine (EANM) guidelines for tumour imaging was good.
Conclusion
These data indicate that it is not necessary to sacrifice the superior lesion detection and image quality achieved by newer reconstruction techniques in the quest for harmonizing quantitative comparability between PET systems.
The aim of this work was to compare anatomic and functional dose-volume parameters as predictors of acute radiation-induced lung toxicity (RILT) in patients with lung tumors treated with stereotactic ...body radiation therapy.
Fifty-nine patients treated with stereotactic body radiation therapy were prospectively included. All patients underwent gallium 68 lung perfusion positron emission tomography (PET)/computed tomography (CT) imaging before treatment. Mean lung dose (MLD) and volumes receiving x Gy (VxGy, 5-30 Gy) were calculated in 5 lung volumes: the conventional anatomic volume (AV) delineated on CT images, 3 lung functional volumes (FVs) defined on lung perfusion PET imaging (FV50%, FV70%, and FV90%; ie, the minimal volume containing 50%, 70%, and 90% of the total activity within the AV), and a low FV (LFV; LFV = AV - FV90%). The primary endpoint of this analysis was grade ≥2 acute RILT at 3 months as assessed with National Cancer Institute Common Terminology Criteria for Adverse Events version 5. Dose-volume parameters in patients with and without acute RILT were compared. Receiver operating characteristic curves assessing the ability of dose-volume parameters to discriminate between patients with and without acute RILT were generated, and area under the curve (AUC) values were calculated.
Of the 59 patients, 10 (17%) had grade ≥2 acute RILT. The MLD and the VxGy in the AV and LFV were not statistically different between patients with and without acute RILT (P > .05). All functional parameters were significantly higher in acute RILT patients (P < .05). AUC values (95% CI) for MLD AV, LFV, FV50%, FV70%, and FV90% were 0.66 (0.46-0.85), 0.60 (0.39-0.80), 0.77 (0.63-0.91), 0.77 (0.64-0.91), and 0.75 (0.58-0.91), respectively. AUC values for V20Gy AV, LFV, FV50%, FV70%, and FV90% were 0.65 (0.44-0.87), 0.64 (0.46-0.83), 0.82 (0.69-0.95), 0.81 (0.67-0.96), and 0.75 (0.57-0.94), respectively.
The predictive value of PET perfusion-based functional parameters outperforms the standard CT-based dose-volume parameters for the risk of grade ≥2 acute RILT. Functional parameters could be useful for guiding radiation therapy planning and reducing the risk of acute RILT.
We aimed to determine the prevalence of residual pulmonary vascular obstruction (RPVO) after symptomatic pulmonary embolism (PE) and to identify risk factors for RPVO.
On the basis of a prospective ...cohort of patients with a documented symptomatic venous thromboembolism, we included patients who had an acute PE and underwent a ventilation/perfusion lung scan at 3 to 24 months during the follow-up after PE. RPVO score was assessed for each patient. Initial pulmonary vascular obstruction at PE diagnosis was also assessed when available. Univariable and multivariable analyses were performed with preselected data to identify predictors for persistent defect defined as RPVO ≥ 5%.
Among the 537 included patients, 278 (51.8%) had RPVO ≥ 5%, and 191 (35.6%) had RPVO ≥ 10%. In primary multivariate analysis on overall population, age ≥ 65 years (odds ratio OR 2.25, 95% CI, 1.45–3.52) and chronic respiratory failure (OR 3.19, 95% CI, 1.22–10.04) were independent predictors of RPVO ≥ 5%. In secondary multivariate analysis restricted to 256 patients with available initial pulmonary vascular obstruction score at index PE (IPVO), age ≥ 65 years (OR 2.78, 95% CI, 1.41–5.53), unprovoked PE (OR 2.11, 95% CI, 1.11–4.07) and IPVO ≥ 20% (OR 2.94, 95% CI, 1.68–5.20) were found to be independent risk factors for RVPO ≥5%.
In this selected population of patients with an acute PE, age ≥ 65 years, unprovoked PE and IPVO ≥ 20% at PE diagnosis appeared to be risk factors for residual pulmonary vascular obstruction measured at three to 24 months.
Differences between computed tomography pulmonary angiography and ventilation-perfusion lung scanning in pregnant patients with suspected acute pulmonary embolism are not well-known, leading to ...ongoing debate on which test to choose. We searched in PubMed, EMBASE, Web of Science and the Cochrane Library databases and identified all relevant articles and abstracts published up to October 1, 2017. We assessed diagnostic efficiency, frequency of non-diagnostic results and maternal and fetal exposure to radiation exposure. We included 13 studies for the diagnostic efficiency analysis, 30 for the analysis of non-diagnostic results and 22 for the radiation exposure analysis. The pooled rate of false negative test results was 0% for both imaging strategies with overlapping confidence intervals. The pooled rates of non-diagnostic results with computed tomography pulmonary angiography and ventilation-perfusion lung scans were 12% (95% confidence interval: 8-17) and 14% (95% confidence interval: 10-18), respectively. Reported maternal and fetal radiation exposure doses were well below the safety threshold, but could not be compared between the two diagnostic methods given the lack of high quality data. Both imaging tests seem equally safe to rule out pulmonary embolism in pregnancy. We found no significant differences in efficiency and radiation exposures between computed tomography pulmonary angiography and ventilation-perfusion lung scanning although direct comparisons were not possible.
Although widely validated, current tests for pulmonary embolism (PE) diagnosis, i.e. computed tomography pulmonary angiography (CTPA) and V/Q planar scintigraphy, have some limitations. Drawbacks of ...CTPA include the radiation dose, some contra indications and a rising concern about a possible overdiagnosis/overtreatment of PE. On the other hand, V/Q planar scintigraphy has a high rate of non-diagnostic tests responsible for complex diagnostic algorithms.
Since the PIOPED study, imaging equipment and radiopharmaceuticals have greatly evolved allowing the introduction of techniques that improve imaging of lung ventilation and perfusion. Single photon emission computed tomography (SPECT) and SPECT/CT techniques are already largely used in daily practice and have been described to have greater diagnostic performance and much fewer non-diagnostic tests as compared with planar scintigraphy. However, they have not yet been firmly validated in large scale prospective outcome studies. More recently, it has also been proposed to image pulmonary perfusion and ventilation using positron emission tomography (PET), which has an inherent technical superiority as compared to conventional scintigraphy and may provide new insight for pulmonary embolism. Regardless of modality, these new thoracic imaging modalities have to be integrated into diagnostic strategies.
The other major challenge for venous thromboembolism diagnosis may be the potential additional value of molecular imaging allowing specific targeting of thrombi in order, for example, to differentiate venous thromboembolism from tumor or septic thrombus, or acute from residual disease.
In this article, the new imaging procedures of lung ventilation perfusion imaging with SPECT, SPECT/CT and PET/CT are discussed. We also review the current status and future challenge of molecular imaging for the in vivo characterization of venous thromboembolism.
•SPECT V/Q has been described to have greater diagnostic performance as compared with planar V/Q.•Large scale prospective outcome studies validating SPECT V/Q are still lacking.•V/Q PET offers great perspectives for PE given the high performance of PET technology.•Labeling in vivo venous clot components is one of the future challenges of nuclear medicine.
We aimed to identify risk factors for recurrent venous thromboembolism (VTE) after unprovoked pulmonary embolism.Analyses were based on the double-blind randomised PADIS-PE trial, which included 371 ...patients with a first unprovoked pulmonary embolism initially treated during 6 months who were randomised to receive an additional 18 months of warfarin or placebo and followed up for 2 years after study treatment discontinuation. All patients had ventilation/perfusion lung scan at inclusion (
at 6 months of anticoagulation).During a median follow-up of 41 months, recurrent VTE occurred in 67 out of 371 patients (6.8 events per 100 person-years). In main multivariate analysis, the hazard ratio for recurrence was 3.65 (95% CI 1.33-9.99) for age 50-65 years, 4.70 (95% CI 1.78-12.40) for age >65 years, 2.06 (95% CI 1.14-3.72) for patients with pulmonary vascular obstruction index (PVOI) ≥5% at 6 months and 2.38 (95% CI 1.15-4.89) for patients with antiphospholipid antibodies. When considering that PVOI at 6 months would not be available in practice, PVOI ≥40% at pulmonary embolism diagnosis (present in 40% of patients) was also associated with a 2-fold increased risk of recurrence.After a first unprovoked pulmonary embolism, age, PVOI at pulmonary embolism diagnosis or after 6 months of anticoagulation and antiphospholipid antibodies were found to be independent predictors for recurrence.
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