Distribution of ventilation/perfusion ratios in pulmonary embolism: an adjunct to the interpretation of ventilation/perfusion lung scans.

Diagnosis of pulmonary embolism (PE) by visual interpretation of ventilation/perfusion (V/Q) scans is limited by the high percentages of patients classified in the intermediate- and low-probability categories. This study proposes a quantitative analysis of the distribution of V/Q ratios to better identify patients with PE. METHODS: We studied 99 consecutive patients who underwent dual-isotope (81m)Kr/(99m)Tc-macroaggregate V/Q scanning and arterial blood gas analysis within 48 h. The 8-view V/Q scans were visually analyzed by 2 observers according to the revised criteria of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) (normal scan or low, intermediate, or high probability of PE). Quantitative analysis of the posterior-view distribution histogram of V/Q ratios was performed using dedicated software. Briefly, regions of interest were drawn around the lungs on the matched V/Q images, smooth filtering was applied, normalized regional V/Q ratios were calculated within each pixel, and a distribution histogram was built. RESULTS: Patients with normal scans (n = 16) had a predominance of V/Q ratios (63.3% +/- 13.0%) between 0.8 and 1.2. They had only 9.8% +/- 5.8% of ratios > 1.2, and the remaining 26.9% +/- 7.5% of ratios were <0.8. By contrast, patients with PE (n = 34) were characterized by a significant increase (15.5 +/- 10.0%, P = 0.04) in high V/Q ratios (>1.2) and a significant increase (34.5% +/- 8.2%, P = 0.003) in low V/Q ratios (<0.8). Interestingly, a similar pattern was found in patients with a high PIOPED probability of PE, 21.3% +/- 11.0% and 37.5% +/- 9.2%, respectively. Within the nondiagnostic group (intermediate- + low-probability scans, n = 58), 17 patients were finally diagnosed with PE. Analysis of the distribution histogram in this group allowed the identification of 5 patients with PE (specificity, 78%). CONCLUSION: A quantitative approach to lung scan interpretation, based on the distribution histogram of V/Q ratios, may be helpful for categorizing patients with suspected PE.     

Combination of clinical and V/Q scan assessment for the diagnosis of pulmonary embolism: a 2-year outcome prospective study

With the aim of evaluating the efficiency of our diagnostic approach in patients with suspected acute pulmonary embolism (PE), we prospectively studied 143 patients investigated by means of a ventilation/perfusion (V/Q) lung scan. A pre-test clinical probability of PE (Pclin) was assigned to all patients by the clinicians and scans were interpreted blinded to clinical assessment. A 2-year follow-up of our patients was systematically performed and possible in 134 cases. Distribution of clinical probabilities was high Pclin in 22.5%, intermediate Pclin in 24% and low Pclin in 53.5%, whereas the distribution of scan categories was high Pscan in 14%, intermediate Pscan in 18%, low Pscan in 57% and normal Pscan in 11%. The final prevalence of PE was 24.5%. High Pscan and normal Pscan were always conclusive (19 and 15 cases respectively). Low Pscan associated with low Pclin could exclude PE in 43/45 cases (96%). None of the patients in whom the diagnosis of PE was discarded had a major event related to PE during the 2-year follow-up. Overall, the combined assessment of clinical and scintigraphic probabilities allowed confirmation or exclusion of PE in 80% of subjects (107/134) and proved to be a valuable tool for selecting patients who needed pulmonary angiography, which was required in 20% of our patients (27/134).     

Combination of clinical and V/Q scan assessment for the diagnosis of pulmonary embolism: a 2-year outcome prospective study

With the aim of evaluating the efficiency of our diagnostic approach in patients with suspected acute pulmonary embolism (PE), we prospectively studied 143 patients investigated by means of a ventilation/perfusion (V/Q) lung scan. A pre-test clinical probability of PE (P_clin) was assigned to all patients by the clinicians and scans were interpreted blinded to clinical assessment. A 2-year follow-up of our patients was systematically performed and possible in 134 cases. Distribution of clinical probabilities was high P_clin in 22.5%, intermediate P_clin in 24% and low P_clin in 53.5%, whereas the distribution of scan categories was high P_scan in 14%, intermediate P_scan in 18%, low P_scan in 57% and normal P_scan in 11%. The final prevalence of PE was 24.5%. High P_scan and normal P_scan were always conclusive (19 and 15 cases respectively). Low P_scan associated with low P_clin could exclude PE in 43/45 cases (96%). None of the patients in whom the diagnosis of PE was discarded had a major event related to PE during the 2-year follow-up. Overall, the combined assessment of clinical and scintigraphic probabilities allowed confirmation or exclusion of PE in 80% of subjects (107/134) and proved to be a valuable tool for selecting patients who needed pulmonary angiography, which was required in 20% of our patients (27/134).     

Tomographic imaging in the diagnosis of pulmonary embolism: a comparison between V/Q lung scintigraphy in SPECT technique and multislice spiral CT.

Although ventilation/perfusion (V/Q) lung scintigraphy is a well-accepted and frequently performed procedure in the diagnosis of pulmonary embolism, there is growing controversy about its relevance, particularly due to the increasing competition between scintigraphy and CT. Even though comparative studies between both modalities have already been performed, their results were highly inconsistent. Remarkably, in most of those studies, conventional planar perfusion scans were compared with tomographic images acquired using state-of-the-art CT scanners-a study design that cannot give impartial results. Hence, the aim of our study was a balanced comparison between V/Q lung scintigraphy and CT angiography using advanced imaging techniques for both modalities. METHODS: A total of 83 patients with suspected pulmonary embolism were examined using V/Q lung scintigraphy in SPECT technique as well as 4-slice spiral CT. Ventilation scans were done using an ultrafine aerosol. Additionally, planar images in 8 views were extracted from the V/Q SPECT datasets. Two experienced referees assessed each of the 3 modalities. The final diagnosis was made at a consensus meeting while taking into account all of the imaging modalities, laboratory tests, clinical data, and evaluation of a follow-up period. RESULTS: In the course of the consensus conference, pulmonary embolism was diagnosed in 37 of the 83 patients (44.6%). Compared with planar scintigraphy, SPECT raised the number of detectable defects at the segmental level by 12.8% (+11 defects; P = 0.401) and at the subsegmental level by 82.6% (+57 defects; P < 0.01). The sensitivity/specificity/accuracy of planar V/Q scintigraphy and V/Q SPECT was 0.76/0.85/0.81 and 0.97/0.91/0.94, respectively, compared with 0.86/0.98/0.93 for multislice CT. CONCLUSION: SPECT and ultrafine aerosols are technical advancements that can substantially improve lung scintigraphy. Using advanced imaging techniques, V/Q scintigraphy and multislice spiral CT both yield an excellent and, in all aspects, comparable diagnostic accuracy, with CT leading in specificity while SPECT shows a superior sensitivity. Even though planar lung scintigraphy yields satisfactory results for a nontomographic modality, it does not compare with tomographic imaging.     

Investigation of perfusion defects by Q-SPECT/CT in patients with mild-to-moderate course of COVID-19 and low clinical probability for pulmonary embolism

Annals of Nuclear Medicine - Pulmonary embolism is a severe source of mortality and morbidity in patients with severe and critical coronavirus disease 2019. It is not yet clear whether the tendency...     

Incremental diagnostic quality gain of CTA over V/Q scan in the assessment of pulmonary embolism by means of a Wells score Bayesian model: results from the ACDC collaboration

Objective

Our objective was to evaluate the diagnostic value of computed tomography angiography (CTA) and ventilation perfusion (V/Q) scan in the assessment of pulmonary embolism (PE) by means of a Bayesian statistical model.

Methods

Wells criteria defined pretest probability. Sensitivity and specificity of CTA and V/Q scan for PE were derived from pooled meta-analysis data. Likelihood ratios calculated for CTA and V/Q were inserted in the nomogram. Absolute (ADG) and relative diagnostic gains (RDG) were analyzed comparing post- and pretest probability. Comparative gain difference was calculated for CTA ADG over V/Q scan integrating ANOVA p value set at 0.05.

Results

The sensitivity for CT was 86.0% (95% CI: 80.2%, 92.1%) and specificity of 93.7% (95% CI: 91.1%, 96.3%). The V/Q scan yielded a sensitivity of 96% (95% CI: 95%, 97%) and a specificity of 97% (95% CI: 96%, 98%). Bayes nomogram results for CTA were low risk and yielded a posttest probability of 71.1%, an ADG of 56.1%, and an RDG of 374%, moderate-risk posttest probability was 85.1%, an ADG of 56.1%, and an RDG of 193.4%, and high-risk posttest probability was 95.2%, an ADG of 36.2%, and an RDG of 61.35%. The comparative gain difference for low-risk population was 46.1%; in moderate-risk 41.6%; and in high-risk a 22.1% superiority. ANOVA analysis for LR+ and LR? showed no significant difference (p = 0.8745, p = 0.9841 respectively).

Conclusions

This Bayesian model demonstrated a superiority of CTA when compared to V/Q scan for the diagnosis of pulmonary embolism. Low-risk patients are recognized to have a superior overall comparative gain favoring CTA.

     

Abdominal CT scans in patients with blunt trauma: low yield in the absence of clinical findings.

This study undertook to determine the yield of abdominal CT scans ordered only because the patient's sensorium was decreased or general anesthesia was planned. The abdominal CT scans and hospital charts of 191 consecutive patients examined following blunt trauma were reviewed with respect to clinical indications prompting the study. In 143, some clinical or laboratory justification was in evidence. In this group, 55 patients (38.5%) were found to have trauma-related pathology at CT scan. In 48 patients, no clinical or laboratory suggestion of abdominal pathology was evident. Instead, the primary indications for ordering the CT scan were decreased sensorium (28 cases), the planning of general anesthesia for orthopedic procedures (8 cases), and a variety of non-abdominal-trauma-related reasons. In this group, only a single positive finding was identified (small pneumothorax), and in no case was the clinical course altered by findings at abdominal CT scan. Performance of abdominal CT scans without clinical or laboratory evidence of trauma, merely because of decreased patient sensorium or prophylactically prior to general anesthesia for non-abdomen-related surgery, is an extremely low yield study and should be discouraged. In the current study, no significant abdominal pathology would have been overlooked by omission of such scans. Similar findings have been reported in children. To our knowledge, this is the first such report in a largely adult population.     

Incidental pulmonary embolism in CT scans of oncological patients with metastatic disease undergoing clinical trials: frequency and linkage with onset of disease progression (PE-PD association)

Objectives:We aimed to analyze the association between the onsets of PE and of progressive disease (PD) in CT scans of oncological patients undergoing clinical trials.Methods:We retrospectively searched our oncological clinical trials database (1/2012 - 6/2017). We retrieved patients who underwent protocol baseline and follow-up CT scans. RECIST 1.1 categories of response were calculated for each scan at interpretation. The entire dataset was searched for reports with incidental PE.For patients with incidental PE, we collected all the scans conducted up to and including the scan with PE. For each scan, we retrieved the recorded RECIST 1.1 category. We excluded patients with PE at baseline.The frequency of incidental PE in oncological clinical trial patients was calculated. For patients with incidental PE, we evaluated the association between PE and PD.Results:During the study period, 1,070 patients underwent 3,818 CTs. The total number of follow-up months was 7,292 months. 18 patients developed incidental PE during follow-up. Thus, the frequency of incidental PE in oncological clinical trial patients was 3% per year of follow-up. Patients with incidental PE underwent 60 scans up to development of PE. Of 42 non-baseline scans, 6/6 (100%) PD showed PE, and 5/36 (13.9%) non-PD showed PE, making PE onset associated with PD onset (p < 0.001).Conclusion:In oncological clinical trials, the frequency of incidental PE is 3% per year of follow-up. The onset of incidental PE is linked to the onset of PD.Advances in knowledge:Incidental PE is associated with the onset of disease progression. Radiologists interpret oncological scans should be aware of the association between PE and PD.     

Lung volume reduction surgery for emphysema: correlation of CT and V/Q imaging with physiologic mechanisms of improvement in lung function

PURPOSE: To compare the relationship between computer-derived and visually assessed ventilation-perfusion (V/Q) scintigraphy and computed tomographic (CT) scores in evaluating disease severity and distribution in identifying optimal candidates for lung volume reduction surgery (LVRS) and to correlate these radiologic indices with physiologic measures of outcome. MATERIALS AND METHODS: In 39 patients, preoperative V/Q and CT scans were visually scored by two radiologists for disease severity and distribution. Results were compared with computer-derived scores for the same cohort. These indices were correlated with clinical improvement measured with forced expiratory volume in 1 second (FEV(1)), forced vital capacity (FVC), and ratio of FEV(1) to FVC. RESULTS: The disease distribution scores measured with the different methods correlated closely: computer-based and visually assessed CT scores (r = 0.89, P <.001), computer-based and visually assessed V/Q scores (r = 0.83, P <.001), visually assessed CT and V/Q scores (r = -0.50, P <.001), and computer-derived CT and V/Q scores (r = -0.57, P =.015). Similarly, a statistically significant correlation was noted between each of the radiologic methods and clinical outcome measurements (P <.001). CONCLUSION: CT and V/Q preoperative assessment, with either visual scoring or computer-based algorithms, are nearly equivalent in their utility in predicting improvement in FEV(1) measures.     

Incomplete recovery of lung perfusion after 3 months in patients with acute pulmonary embolism treated with antithrombotic agents. THESEE Study Group. Tinzaparin ou Heparin Standard: Evaluation dans l'Embolie Pulmonaire Study.

We assessed the time course of lung perfusion after 3 mo of anticoagulant therapy for acute pulmonary embolism (APE) on the basis of perfusion lung scan (PLS) findings for 157 patients included in the Tinzaparin ou Heparin Standard: Evaluation dans l'Embolie Pulmonaire Study (THESEE), a multicenter, randomized, nonmasked trial comparing standard, continuous, adjusted-dose intravenous heparin with once-daily, subcutaneous, low-molecular-weight heparin in patients with APE. METHODS: We calculated the percentage-of-vascular-obstruction score (PVOs) on PLSs on the day of diagnosis of APE (PVOsD1), on day 8 (PVOsD8), and after 3 mo (PVOsM3) and the mean relative changes in PVOs on day 8 versus the day of diagnosis and after 3 mo versus the day of diagnosis. RESULTS: Mean PVOsD1 +/- SD was 49% +/- 20%, PVOsD8 was 29% +/- 18%, and PVOsM3 was 19% +/- 18%. PVOsD1 was at least 50% in 49% of patients. Reperfusion did not correlate with age, importance of initial obstruction, or clinical severity of disease at inclusion in THESEE. Relative change after 3 mo versus at diagnosis was lower in the 87 patients with associated prior cardiopulmonary disease than in those without. In the 43 patients with a history of thromboembolic disease, neither mean PVOsD1 nor the time course of PVOs was different from those in patients without a history of thromboembolic disease. Residual defects after 3 mo were observed in 104 patients (66%), including 13 with a PVOs of at least 50%. CONCLUSION: These results emphasize the need for a control PLS at completion of anticoagulant therapy for APE, even in patients with full resolution of symptoms.     

Preliminary clinical assessment of dynamic 18F-fluorodeoxyglucose positron emission tomography/computed tomography for evaluating lymph node metastasis in patients with lung cancer: a prospective study

Annals of Nuclear Medicine - We assessed the diagnostic capacity of dynamic fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and dual-time-point...     

Baseline/postnitrate tetrofosmin SPECT for myocardial viability assessment in patients with postischemic severe left ventricular dysfunction: new evidence from MRI.

The aim of this study was to compare (99m)Tc-tetrofosmin SPECT with contrast-enhanced MRI (ceMRI), a new direct sign of myocardial fibrosis. METHODS: We studied 21 patients (age, 60 +/- 11 y; 19 male) with previous myocardial infarction and severe left ventricular dysfunction (ceMRI EF, 29% +/- 6%). All patients underwent resting and postnitrate (intravenous isosorbide dinitrate) (99m)Tc-tetrofosmin gated SPECT as well as ceMRI. Scintigraphic analysis was performed using quantitative perfusion SPECT (QPS), providing the percentage radiotracer uptake and defect severity in a 20-segment model. Hyperenhancement was defined by the increase of ceMRI signal intensity 20 min after intravenous injection of gadolinium-diethylenetriaminepentaacetic acid and its regional extension as the percentage of the total segment area. RESULTS: In ceMRI dysfunctional segments, the correlation between the extent of hyperenhancement and both (99m)Tc-tetrofosmin uptake and defect severity was significantly better after nitrate administration rather than at rest (P < 0.0001). Using a ceMRI cutoff below 40%, 102 of 196 (52%) segments were viable, whereas 94 (48%) segments were not viable. According to receiver-operating characteristic curve analysis, diagnostic accuracies were higher for postnitrate (99m)Tc-tetrofosmin uptake as well as perfusion defect severity than using resting data (0.84 vs. 0.71, P < 0.001; 0.89 vs. 0.76, P < 0.001, respectively). CONCLUSION: After nitrate administration, (99m)Tc-tetrofosmin uptake and perfusion defect severity were closely related to ceMRI, demonstrating, in vivo, the existence of an inverse correlation between the transmural distribution of fibrosis and tracer delivery to the myocardium.