Suspected acute pulmonary embolism: evaluation with multi-detector row CT versus digital subtraction pulmonary arteriography

Has the Coronavirus Disease 2019 Pandemic Played a Role in the Early Detection of Pulmonary Embolism in Children?

OBJECTIVE

Pulmonary embolism (PE) poses a significant threat to children, and nonspecific symptoms lead to delayed diagnosis. The emergence of coronavirus disease 2019 (COVID-19) has increased the complexity as it is associated with similar symptoms and increased risk of thrombotic complications. This study aimed to assess the risk factors, clinical presentations, and diagnostic features of PE in pediatric patients and to examine the impact of the COVID-19 pandemic on children with PE.

MATERIALS AND METHODS

We conducted a retrospective descriptive study examining the clinical and diagnostic data of 44 pediatric patients with radiologically confirmed PE. The study compared and analyzed patients diagnosed before and during the COVID-19 pandemic.

RESULTS

In the study, 21 of 44 pediatric patients were diagnosed in the 4 years before the COVID-19 pandemic, and 23 were diagnosed with PE during the COVID-19 pandemic. The mean time to diagnosis was 8 (2 to 14) days before the pandemic and 1 (1 to 2) days during the pandemic ( P < 0.001). The most common associated condition in both groups was infection (65.9%). Dyspnea (65.9%) and tachypnea (50.0%) were common symptoms. Except for deep vein thrombosis, there were no significant differences according to associated conditions between the groups ( P = 0.001). Pulmonary emboli were anatomically detected using computed tomography angiography, showing bilateral involvement in 45.4% of patients, segmental artery involvement in 38.6%, and main artery involvement in 15.9%.

CONCLUSION

The COVID-19 pandemic heightened suspicion of pediatric PE and accelerated diagnosis. Standardized diagnostic guidelines are increasingly necessary to balance accurate diagnosis with avoiding excessive imaging.

An overview of systematic reviews on imaging tests for diagnosis of pulmonary embolism applying different network meta-analytic methods

PURPOSE

This study aimed to apply different methods of diagnostic test accuracy network meta-analysis (DTA-NMA) for studies reporting results of five imaging tests for the diagnosis of suspected pulmonary embolism (PE): pulmonary angiography (PA), computed tomography angiography (CTPA), magnetic resonance angiography (MRA), planar ventilation/perfusion (V/Q) scintigraphy and single-photon emission computed tomography ventilation/perfusion (SPECT V/Q).

METHODS

We searched four databases (MEDLINE [via PubMed], Cochrane CENTRAL, Scopus, and Epistemonikos) from inception until June 2, 2022 to identify systematic reviews (SRs) describing diagnostic accuracy of PA, CTPA, MRA, V/Q scan and SPECT V/Q for suspected PE. Study-level data were extracted and pooled using a hierarchical summary receiver operating characteristic (HSROC) meta-regression approach and two DTA-NMA models to compare accuracy estimates of different imaging tests. Risk of bias was assessed using the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies-2) tool and certainty of evidence using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) framework.

RESULTS

We identified 13 SRs, synthesizing data from 33 primary studies and for four imaging tests (PA, CTPA, MRA and V/Q scan). The HSROC meta-regression model using PA as the reference standard showed that MRA had the best overall diagnostic performance with sensitivity of 0.93 (95% confidence interval [CI]: 0.76, 1.00) and specificity of 0.94 (95% CI: 0.84, 0.99). However, DTA-NMA models indicated that V/Q scan had the highest sensitivity, while CTPA was most specific.

CONCLUSION

Selecting a different DTA-NMA method to assess multiple diagnostic tests can affect estimates of diagnostic accuracy. There is no established method, but the choice depends on the data and familiarity with Bayesian statistics.

Pediatric Pulmonary Embolism: Imaging Guidelines and Recommendations

In contrast with the algorithms and screening criteria available for adults with suspected pulmonary embolism, there is a paucity of guidance on the diagnostic approach for children. The incidence of pulmonary embolism in the pediatric population and young adults is higher than thought, and there is an urgent need for updated guidelines for the imaging approach to diagnosis in the pediatric population. This article presents an up-to-date review of imaging techniques, characteristic radiologic findings, and an evidence-based algorithm for the detection of pediatric pulmonary embolism to improve the care of pediatric patients with suspected pulmonary embolism.

Is COVID Evolution Due to Occurrence of Pulmonary Vascular Thrombosis?

In this hypothesis paper, we suggest that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may induce intravascular pulmonary thrombosis, which may result in the rapid worsening of clinical conditions and, eventually, exitus. Previously published papers have demonstrated that increased levels of D-dimer at hospital admission correlate with a more severe disease (0.5 mg/L) or occurrence of death (1 mg/L). The potential prothrombotic action of the SARS-CoV-2 is supported by the topographical involvement of the lung regions with a predilection for the lower lobe with peripheral involvement. If this hypothesis is demonstrated, this could suggest the benefit of using antithrombotic/coagulation regimens for SARS-CoV-2 and, at the same time, the urgency to identify drugs that could alter the inflammatory storm, thus protecting the vessel wall.

Diagnostic accuracy of true fast imaging with steady-state precession, MR pulmonary angiography and volume-interpolated body examination for pulmonary embolism compared with CT pulmonary angiography

The diagnostic performance of magnetic resonance (MR) sequences for displaying different levels of pulmonary artery involvement in pulmonary embolism (PE) has rarely been reported but is essential for critically ill and emergency patients. The aim of the present study was to analyze the diagnostic accuracy of true fast imaging with steady-state precession (true FISP), MR pulmonary angiography (MRPA) and volume-interpolated body examination (VIBE) for PE detection in comparison to CT pulmonary angiography (CTPA), which is the reference standard. A total of 21 patients with confirmed deep venous thrombosis suspected of having PE were enrolled. Emboli were evaluated on per-patient and per-vessel bases. The evidence of PE on a per-vessel basis was classified into central, lobar and segmental levels, and 27 vessel segments per patient were analyzed for a total of 567 vessel segments in all patients. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated. Receiver operating characteristic curves were drawn to compare differences in sequences. A total of 158 pulmonary vessels were involved with emboli on CTPA, 58 of which were identified by true FISP, 63 by MRPA and 94 by VIBE. On per-patient and per-vessel bases, the sensitivity was 81.3 and 36.7%, respectively, for true FISP, 82.4 and 56.3%, respectively, for MRPA, and 94.4 and 68.1%, respectively, for VIBE; the specificity was 80.0 and 99.8%, respectively, for true FISP, 100 and 99.2%, respectively, for MRPA, and 100 and 99.2%, respectively, for VIBE. The respective PPV was 92.9 and 98.3% for true FISP, 100 and 95.5% for MRPA, 100 and 96.9% for VIBE. The NPV was 57.1 and 80.3%, respectively, for true FISP, 50.0 and 88.2%, respectively, for MRPA, and 75.0 and 89.8%, respectively, for VIBE. In conclusion, enhanced VIBE surpassed the other two sequences in revealing PE, particularly in segmental analysis, which is essential for emergency patients who have contraindications for receiving iodinated contrast and those who have concerns about the ionizing radiation.

Computed tomography angiography study of the azygos vein course and termination into superior vena cava: gender and age impact

PURPOSE

The study highlights azygos vein (AV) topography, arrangement and confluence morphometry in dyspnoea and tachycardia patients of extrapulmonary and extracardiac aetiology.

METHOD

Computed-tomography angiography of 25 male and 26 female patients (mean age 66.5 years) were studied for: thoracic vertebral (T) height of AV- superior vena cava-SVC confluence, AV course and deviations from vertebral column (VC) midline, AV and SVC diameters, distance (AV arch- lower border of carina) and gender and age impact.

RESULTS

Commonest heights of the AV-SVC confluence were T5 (56.9%), T4 (31.4%), T6 (9.8%) and T3 (2%). The AV terminated into SVC after crossing the left side of VC midline in 56.9%, slightly deviated right of the midline in 37.3% and coursed right of VC in 5.9%. Mean AV and SVC diameters were 0.96 ± 0.18 cm and 1.86 ± 0.27 cm. Male predominance in AV and SVC diameters and a slight AV diameter significant increase with the age were found. The (AV highest point-lower border of carina) mean distance was 2.05 ± 0.44 cm and male predominance existed.

CONCLUSION

The commonest termination height of the AV was T5, while T3 was the rarest one. Aging induces the AV leftward displacement, while gender had no impact. AV and SVC diameters had higher significant values in males, while ageing had a significant impact only in AV diameter. The AV higher diameters will be used as predictors for higher values of SVC diameter and mediastinum pathology. Such findings can be useful in mediastinal surgery, mediastinoscopy and surgery of VC deformations, neurovascular surgery of retroperitoneal organs, disc herniation and T fractures.

Acute pulmonary embolism multimodality imaging prior to endovascular therapy

The manuscript discusses the application of CT pulmonary angiography, ventilation–perfusion scan, and magnetic resonance angiography to detect acute pulmonary embolism and to plan endovascular therapy. CT pulmonary angiography offers high accuracy, speed of acquisition, and widespread availability when applied to acute pulmonary embolism detection. This imaging modality also aids the planning of endovascular therapy by visualizing the number and distribution of emboli, determining ideal intra-procedural catheter position for treatment, and signs of right heart strain. Ventilation–perfusion scan and magnetic resonance angiography with and without contrast enhancement can also aid in the detection and pre-procedural planning of endovascular therapy in patients who are not candidates for CT pulmonary angiography.

Radiologist Performance in the Detection of Pulmonary Embolism: Features that Favor Correct Interpretation and Risk Factors for Errors

PURPOSE

This study aimed to assess the factors contributing toward accurate detection and erroneous interpretation of pulmonary embolism (PE).

MATERIALS AND METHODS

Over 13 months, all computed tomography pulmonary angiography studies were retrospectively rereviewed by a chest radiologist. Two additional chest radiologists assessed cases with disagreement between the first interpretation and rereview. The number, extent, and location of PE and specialty training, experience, time of study, kV, resident prelim, use of iterative reconstruction, signal to noise ratio (SNR), and reports describing the study as "limited" were recorded. Parametric and nonparametric statistical testing was performed (significance P<0.05).

RESULTS

Of 2555 computed tomography pulmonary angiography cases assessed, there were 230 true positive (170 multiple, 60 single PE), 2271 true negative, 35 false-negative (15 multiple and 20 single PE), and 19 false-positive studies. The overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy of radiologists was 86.8%, 99.2%, 92.4%, 98.5%, and 97.9%. Sensitivity for the detection of multiple and central PE was significantly higher than the detection of single and peripheral PE, respectively (P<0.01 for both). The sensitivity of thoracic radiologists (91.7%) was higher than nonthoracic (82.8%) and reached significance for single PE (89.2% vs. 61.4%, P<0.02). Errors were more likely in cases with lower SNR (P=0.04) and those described as limited (P<0.001). Misses occurred more frequently in the upper lobe posterior and lower lobe lateral segments and subsegments (P=0.038).

CONCLUSIONS

The accuracy for PE detection is high, but errors are more likely in studies with single PE interpreted by nonthoracic radiologists, especially when located in certain segments and in cases with low SNR or described as limited.

Facing the challenge of venous thromboembolism prevention in patients undergoing major abdominal surgical procedures for gastrointestinal cancer

Venous thromboembolism (VTE) refers to a hypercoagulable state that remains an important and preventable factor in the surgical treatment of malignancies. VTE includes two identical entities with regards to deep vein thrombosis and pulmonary embolism. The incidence of VTE after major abdominal interventions for gastro-intestinal, hepato-biliary and pancreatic neoplastic disorders is as high as 25% without prophylaxis. Prophylactic use of classic or low-molecular-weight heparin, anti-Xa factors, antithrombotic stocking, intermittent pneumatic compression devices and early mobilization have been described. Nevertheless, thromboprophylaxis is often discontinued after discharge, although a serious risk may persist long after the initial triggering event, as the coagulation system remains active for at least 14 d post-operatively. The aim of this review is to evaluate the results of the current practice of VTE prevention in cancer patients undergoing major abdominal surgical operations, with special attention to adequately elucidated guidelines and widely accepted protocols. In addition, the recent literature is presented in order to provide an update on the current concepts concerning the surgical management of the disease.

Rivaroxaban and Acetylsalicylic Acid for Prevention of Venous Thromboembolism Following Total Knee Arthroplasty in Korean Patients

Purpose

To investigate the incidence of venous thromboembolism (VTE) after total knee arthroplasty (TKA) with chemoprophylaxis using acetylsalicylic acid (AA) or rivaroxaban in Korean patients.

Materials and Methods

Between May 2011 and November 2013, 268 TKA patients (330 cases) were randomly allocated to 3 groups (group A: subcutaneous injection of 5,000 IU low-molecular-weight heparin for 2 days followed by oral administration of 100 mg AA for 5 days; group X7: oral administration of 10mg rivaroxaban for 7 days; and group X10: oral administration of 10 mg rivaroxaban for 10 days). Multidetector-row computed tomography (MDCT) was performed at 10 days and 3 months postoperatively to evaluate VTE changes.

Results

The VTE incidence was 38.2%, 20.0%, and 10.0% in groups A, X7, and X10, respectively (p<0.001). Pulmonary embolism (PE) was identified in 19.1%, 10.0%, and 2.7% in groups A, X7, and X10, respectively (p<0.001). Proximal or symptomatic deep vein thrombosis (DVT) occurred primarily in group A, but the incidence was not significantly different among groups. On follow-up MDCT, PE was resolved completely with treatment in 29/30 (96.7%), and so was asymptomatic distal DVT in 24/27 (88.8%) without treatment.

Conclusions

Rivaroxaban had a lower incidence of overall VTE than AA, but no difference was observed in symptomatic VTE. The 10-day course of rivaroxaban had a lower incidence of overall VTE than the 7-day course.

Incidental pulmonary emboli in stage IV melanoma patients: Prevalence in CT staging examinations and improved detection with vessel reconstructions based on dual energy CT

OBJECTIVES

Malignancy is the strongest predictor for venous thromboembolism. Dual energy CT (DECT) can support assessment of pulmonary emboli (PE) by providing vessel reconstructions (DECT-VR) and highlighting thrombi. Purpose was to determine prevalence and risk factors of PE in staging examinations of stage IV-melanoma patients and to evaluate the potential of DECT-VR to improve PE diagnosis.

MATERIAL AND METHODS

This retrospective study was approved by IRB. Contrast-enhanced, conventional grey scale CT (cCT) and DECT-VR of 200 stage IV-melanoma patients were reviewed by three radiologists in consensus. Overall prevalence was determined. One-sided Wilcoxon-test was performed to compare the number of detected emboli between cCT and cCT with supplementary DECT-VR. Frequencies of risk factors were compared with χ2 test.

RESULTS

On cCT, 9 PE were detected (6 patients, correlating to 3% of the study population with 0.05 emboli per patient). With the supplementary DECT-VR, number of diagnosed emboli increased from 9 to 17 (p < 0.05) (in total 9 patients, correlating to 0.09 emboli per patient). Emboli on DECT-VR were mainly subsegmentally (7 of 8). There was no significant difference in the frequency of risk factors.

CONCLUSIONS

The prevalence of pulmonary emboli in our cohort of 200 stage IV melanoma patients was 5%. DECT-VR improved significantly diagnosis of PE, especially when located subsegmentally.

Pulmonary thromboembolism: new diagnostic imaging techniques

The accurate diagnosis of pulmonary thromboembolism is essential to reducing the morbidity and mortality associated with the disease. The diagnosis of pulmonary thromboembolism is challenging because of the nonspecific nature of the clinical profile and the risk factors. Imaging methods provide the definitive diagnosis. Currently, the imaging method most commonly used in the evaluation of pulmonary thromboembolism is computed tomography. The recent development of dual-energy computed tomography has provided a promising tool for the evaluation of pulmonary perfusion through iodine mapping. In this article, we will review the importance of diagnosing pulmonary thromboembolism, as well as the imaging methods employed, primarily dual-energy computed tomography.

Outcomes following a negative computed tomography pulmonary angiography according to pulmonary embolism prevalence: a meta-analysis of the management outcome studies

Essentials Computed tomographic pulmonary angiography (CTPA) is used to exclude pulmonary embolism. This meta-analysis explores the occurrence of venous thromboembolic events (VTE) after a CTPA. Occurrence of VTE after a negative CTPA is ˜8% in study subgroups with a prevalence of PE ≥ 40%. CTPA may be insufficient to safely rule out VTE as a stand-alone diagnostic test for this subgroup.

SUMMARY

Background Outcome studies have reported the safety of computed tomographic pulmonary angiography (CTPA) as a stand-alone imaging technique to rule out pulmonary embolism (PE). Whether this can be applied to all clinical probabilities remains controversial. Objectives We performed a meta-analysis to determine the proportion of patients with venous thromboembolic events (VTE) despite a negative CTPA according to pretest PE prevalence. Methods We searched MEDLINE, EMBASE and the Cochrane Library (January 1990 to May 2017) for outcome studies recruiting patients with suspected PE using CTPA as a diagnostic strategy. The primary outcome was the cumulative occurrence of VTE at 3 months following a negative CTPA. Results Twenty-two different studies were identified. VTE was confirmed in 2.4% of patients (95% CI, 1.3-3.8%) either at the time of the index event or in the 3 months follow-up. Subgroup analyses suggested that the cumulative occurrence of VTE was related to pretest prevalence of PE, as VTE occurred in 1.8% (95% CI, 0.5-3.7%), 1.4% (95% CI, 0.7-2.3%), 1.0% (95% CI, 0.5-1.8%) and 8.1% (95% CI, 3.5-14.5%) of subgroups of patients with a PE prevalence < 20%, 20-29%, 30-39% and ≥ 40%, respectively. This was further confirmed using meta-regression analysis. Conclusions The negative predictive value of CTPA for VTE varies according to pretest prevalence of PE, and is likely to be insufficient to safely rule out VTE as a stand-alone diagnostic test amongst patients at the highest pretest probability of VTE. Prospective studies are required to validate the appropriate diagnostic algorithm for this subgroup of patients.

Clinical application of the Innovance D-dimer assay in the diagnosis of acute pulmonary thromboembolism

Patients with acute pulmonary thromboembolism (APTE) have a high short-term mortality rate. The current study aimed to investigate the use of D-dimer in the diagnosis of APTE in suspected APTE patients. All suspected APTE patients were classified into diagnosis or control groups according to the results of a computed tomography pulmonary angiogram. Mann-Whitney U and Kruskal-Wallis H tests were used to evaluate the association between D-dimer values and APTE. Area under the curve (AUC) values and the Youden Index were used to determine D-dimer cut-off levels for the prediction of APTE. The data of 112 suspected APTE patients (54.8% women; mean age, 70.5 years) were analyzed prospectively. There were no significant differences in age (74.5 vs. 73.5 years, P=0.538) or gender distribution (female ratio 56.5 vs. 53.0%, P=0.847) between the diagnosis and control groups. The incidence of symptoms including dyspnea (67.4 vs. 33.3%; P<0.01), chest distress (47.8 vs. 25.8%; P<0.05) and elevated D-dimer (8.49 vs. 0.97 mg/l; P<0.001) were significantly higher in patients with APTE compared with the control group. D-dimer values >3.32 mg/l fibrinogen equivalent units (FEU) were indicative of APTE and the Youden Index was 0.69. The maximum AUC was 0.87 (95% CI: 0.79-0.92), the sensitivity and specificity were 89.13 and 80.30%, respectively, the positive and negative likelihood ratios were 4.53 and 0.14, respectively, and the positive and negative predictive values were 75.90 and 91.40%, respectively. A D-dimer value <0.60 mg/l FEU was the optimal threshold for excluding APTE diagnosis, with a sensitivity of 100.0% and a specificity of 28.79%. The positive and negative likelihood ratios were 1.40 and 0.00, respectively, and the positive and negative predictive values were 49.50 and 100.00%, respectively. Thus, D-dimer levels, combined with clinical assessment, yield high sensitivity and specificity in diagnosing APTE.

Low dose computed tomography pulmonary angiography protocol for imaging pregnant patients: Can dose reduction be achieved without reducing image quality?

OBJECTIVE

To assess the effect of low dose computed tomography pulmonary angiography (CTPA) on radiation dose in pregnant patients.

MATERIALS AND METHODS

An old CTPA protocol for pregnant patients was compared to a new protocol. Protocol changes included: decreased kVp; increased contrast injection rate; imaging after shallow inspiration. Patients undergoing CTPA before (phase 1 group) or after (phase 2 group) the protocol change, were assessed.

RESULTS

Effective dose was lower in the phase 2 group (0.95 v 1.66 mSv; p<0.001). Quantitative noise was lower in the phase 1 group (p<0.001).

CONCLUSION

Low dose CTPA tailored for pregnancy reduces dose in pregnant patients.

CT pulmonary angiography using different noise index values with an iterative reconstruction algorithm and dual energy CT imaging using different body mass indices: Image quality and radiation dose

OBJECTIVE

To investigate the differences in imaging quality and radiation dose in CT pulmonary angiography (CTPA) by using fast-kV switching dual energy CT imaging and 3D Smart mA modulation at different body mass indices (BMIs) and at different noise index (NI) values with an adaptive statistical iterative reconstruction (ASIR) algorithm.

METHODS

Four hundred patients who underwent CTPA were equally divided into two groups: A (18.5 kg/m2 ≦ BMI <24.9 kg/m2) and B (24.9 kg/m2 ≦ BMI ≦ 4.9 kg/m2). The groups were randomly subdivided into four subgroups (n = 50): A1-A4 and B1-B4. The patients in subgroups A1 and B1 underwent fast-kV switching dual energy CT imaging. The other patients underwent 3D Smart mA modulation with the ASIR algorithm at NI values 26, 36, and 46 for A2/B2, A3/B3, and A4/B4, respectively. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all images were calculated after CTPA. Images were then subjectively evaluated using a 5-point scale. The volume CT dose index and dose-length product (DLP) were recorded and their means calculated. The DLP was converted to the effective dose (ED).

RESULTS

In group A, the SNR, CNR, and subjective image scores showed no statistical differences (P > 0.05). The ED in subgroup A4 was 67.12% and 31.53% lower than that in A1 and A2, respectively. In group B, the variables showed no significant differences between the subgroups B3, B1, and B2 (P > 0.05). The ED in subgroup B3 was 50.12% and 35.95% lower than that in B1 and B2, respectively.

CONCLUSIONS

Setting different NI values according to BMIs and applying the ASIR algorithm can more effectively reduce the radiation dose in CTPA than in fast-kV switching dual energy CT, while maintaining image quality. Imaging may be performed at NI = 46 in patients with lower BMI (group A) and at NI = 36 in patients with higher BMI (group B).

CT Pulmonary Angiography Using Automatic Tube Current Modulation Combination with Different Noise Index with Iterative Reconstruction Algorithm in Different Body Mass Index: Image Quality and Radiation Dose

RATIONALE AND OBJECTIVES

This study aimed to determine the appropriate body mass index (BMI)-dependent noise index (NI) setting in computed tomography pulmonary angiography (CTPA) with automatic tube current modulation with adaptive statistical iterative reconstruction (ASiR).

MATERIALS AND METHODS

A total of 480 patients who had a CTPA were divided into group A (18.5 kg/m² ≤ BMI < 25 kg/m²), group B (25 kg/m² ≤ BMI < 30 kg/m²), and group C (BMI ≥ 30 kg/m²), according to their BMI values; each group had 160 patients. The three groups were further randomly divided into four subgroups: A1, A2, A3, A4; B1, B2, B3, B4; and C1, C2, C3, C4, with corresponding NI values of 26, 36, 40, and 46, respectively. All images were restructured with the ASiR algorithm, and the images with the lowest NI (26 Hounsfield units) in each group were used as reference standard. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for the pulmonary artery of each group were calculated. Subjective image quality was evaluated using a five-score method by two independent radiologists. The CT dose index of volume and dose-length product were recorded and were converted to effective dose (ED). SNR and CNR in the group A, B, and C subgroups were compared to repeated measures analysis of variance, and the subjective score, Volumetric CT dose index of volume, dose-length product, and ED were compared to one-way analysis of variance.

RESULTS

For groups A and B, the SNR, CNR, and subjective scores of the images in their subgroups showed no statistical differences (P >.05). The ED in subgroups A4 and B4 was significantly lower than that in subgroups A1 (by 33.24%) and B1 (by 34.47%) (P <.01). For group C, there was no significant difference in the SNR, CNR, and the subjective image scores between subgroups C3 and C1 (P >.05). The ED in subgroup C3 was significantly lower than the ED in subgroup C1 (by 47.75%) (P <.01) CONCLUSIONS: Patient BMI-dependent NI settings that are higher than the recommended value may be used in CTPA with automatic tube current modulation and ASiR to effectively reduce radiation dose while maintaining diagnostic image quality.

CT Pulmonary Angiography at Reduced Radiation Exposure and Contrast Material Volume Using Iterative Model Reconstruction and iDose4 Technique in Comparison to FBP

Purpose

To assess image quality of CT pulmonary angiography (CTPA) at reduced radiation exposure (RD-CTPA) and contrast medium (CM) volume using two different iterative reconstruction (IR) algorithms (iDose⁴ and iterative model reconstruction (IMR)) in comparison to filtered back projection (FBP).

Materials and Methods

52 patients (body weight < 100 kg, mean BMI: 23.9) with suspected pulmonary embolism (PE) underwent RD-CTPA (tube voltage: 80 kV; mean CTDIvol: 1.9 mGy) using 40 ml CM. Data were reconstructed using FBP and two different IR algorithms (iDose⁴ and IMR). Subjective and objective image quality and conspicuity of PE were assessed in central, segmental, and subsegmental arteries.

Results

Noise reduction of 55% was achieved with iDose⁴ and of 85% with IMR compared to FBP. Contrast-to-noise ratio significantly increased with iDose⁴ and IMR compared to FBP (p<0.05). Subjective image quality was rated significantly higher at IMR reconstructions in comparison to iDose⁴ and FBP. Conspicuity of central and segmental PE significantly improved with the use of IMR. In subsegmental arteries, iDose⁴ was superior to IMR.

Conclusions

CTPA at reduced radiation exposure and contrast medium volume is feasible with the use of IMR, which provides improved image quality and conspicuity of pulmonary embolism in central and segmental arteries.

Incidence of actionable findings on contrast enhanced magnetic resonance angiography ordered for pulmonary embolism evaluation

PURPOSE

To determine the incidence of actionable findings on contrast-enhanced magnetic resonance angiography (MRA) scans performed for the primary diagnosis of pulmonary embolism (PE).

MATERIALS AND METHODS

This was a HIPAA-compliant and IRB-approved single center, retrospective study of consecutive series of patients evaluated with contrast-enhanced MRA for PE. The final radiology report of each MRA was reviewed. All technically adequate negative exams were included in the analysis. The findings were divided into three types: those requiring further action (actionable-Type 1) those not requiring follow-up (non-actionable-Type 2) and normal exams. We compared our results with the literature regarding the use of computed tomographic angiography (CTA) in this scenario using Fisher's exact test.

RESULTS

580 MRA scans for PE were performed. There were 561/580 (97%) technically adequate exams. Of these, 514/580 (89%) were negative and 47/580 (8%) were positive for PE. In the PE negative group of 514 exams, Type 1 findings were identified in 85/514 (17%), 188/514 (36%) cases were Type 2 and 241/514 (47.0%) were Type 3. There was no significant difference between the incidence of Type 1 and the combination of Type 2 and Type 3 findings on MRA and the reported incidence of actionable findings derived from CTA negative exams for PE (p<0.5).

CONCLUSION

MRA as a first-line test for PE can identify actionable findings in those patients without PE, with an incidence similar to that reported in the literature for CTA.

Split-Bolus Single-Pass Multidetector-Row CT Protocol for Diagnosis of Acute Pulmonary Embolism

Background:

Currently computed tomography pulmonary angiography (CTPA) has become a widely accepted clinical tool in the diagnosis of acute pulmonary embolism (PE).

Objectives:

To report split-bolus single-pass 64-multidetector-row CT (MDCT) protocol for diagnosis of PE.

Patients and Methods:

MDCT split-bolus results in 40 patients suspicious of PE were analyzed in terms of image quality of target pulmonary vessels (TPVs) and occurrence and severity of flow-related artifact, flow-related artifact, false filling defect of the pulmonary veins and beam hardening streak artifacts. Dose radiation to patients was calculated.

Results:

MDCT split-bolus protocol allowed diagnostic images of high quality in all cases. Diagnosis of PE was obtained in 22 of 40 patients. Mean attenuation for target vessels was higher than 250 HU all cases: 361 ± 98 HU in pulmonary artery trunk (PAT); 339 ± 93 HU in right pulmonary artery (RPA); 334 ± 100 HU in left pulmonary artery (LPA). Adequate enhancement was obtained in the right atrium (RA):292 ± 83 HU; right pulmonary vein (RPV): 302 ± 91 HU, and left pulmonary vein (LPV): 291 ± 83 HU. The flow related artifacts and the beam hardening streak artifacts have been detected respectively in 4 and 25 patients. No false filling defect of the pulmonary veins was revealed.

Conclusion:

MDCT split-bolus technique by simultaneous opacification of pulmonary arteries and veins represents an accurate technique for diagnosis of acute PE, removes the false filling defects of the pulmonary veins, and reduces flow related artifacts.

Qualitative evaluation of pulmonary CT angiography findings in pregnant and postpartum women with suspected pulmonary thromboembolism

Background:

Considering the importance of using more appropriate imaging technique for accurate diagnosis of pulmonary thromboembolism (PTE) with less side effects, we aimed to evaluate the quality of pulmonary 64-multidetector computed tomographic (MDCT) angiography in pregnant and postpartum women with suspected PTE in Isfahan.

Materials and Methods:

In this descriptive study, radiological findings of pregnant and postpartum women with suspected PTE who underwent pulmonary 64-MDCT angiography were evaluated. Prevalence of PTE in pregnant and postpartum women, mean of pulmonary arteries density for right and left pulmonary arteries, and their lobar and segmental branches, diagnostic quality of the pulmonary arteries density and their scoring, frequency of diagnostic and nondiagnostic images, mean of radiation dose and mean of bolus time, and the correlation between the quality of the vascular density with the peak density of the pulmonary artery were determined.

Results:

In this study, 44 pregnant and postpartum women with suspected PTE were selected. The overall prevalence of PTE was 9.1% (4/44). PTE was diagnosed in 1 (3.7%) pregnant and 3 (17.5%) postpartum women (P = 0.14). Mean density of pulmonary trunk was 278.81± 108.16 Hounsfield unit (HU) and 308.41 ± 59.30 HU in pregnant and postpartum women, respectively. Mean of bolus timing, kilovoltage peak (kVp), tube current, and dose length product (DLP) were 12.53 ± 2.36 s, 105.22± 45.71 milliamperage (MA), 382.9 ± 173.5 MA, and 317.98 ± 78.92 mGy/cm, respectively. The rate of nondiagnostic images was 4.5%.

Conclusion:

Our findings indicated that pulmonary 64-MDCT angiography is an appropriate imaging method for diagnosing PTE in pregnant and postpartum women with suspected PTE. It seems that, using fast CT systems (64-MDCT), in accordance with high flow rate, high contrast medium concentration and low kVp could explain the obtained appropriate quality of images more efficiently than computed tomographic pulmonary angiography (CTPA).

Venous thrombosis in pancreaticobiliary tract cancer: outcome and prognostic factors

BACKGROUND

The differences in outcome among cancer patients with incidental vs. symptomatic venous thromboembolism (VTE) are unknown. In this study, patients with extrahepatic pancreaticobiliary tract cancer (PBC) were selected for a prospective cohort study between February 2008 and February 2011.

METHODS

At the time of cancer diagnosis, all patients were examined for deep vein thrombosis with bilateral compression ultrasonography (biCUS). Computed tomography pulmonary angiography was also performed to diagnose pulmonary embolisms. After inclusion, the patients were followed up with clinical examinations, blood collections, and biCUS.

RESULTS

A total of 121 PBC patients were enrolled. At the time of cancer diagnosis, 15 patients had experienced a VTE (12.4%, 95% confidence interval [CI] 7.1-19.6), including six symptomatic and nine incidental cases. A total of 25 first-time VTE events were identified (20.7%; 95% CI 13.8-29.0). Patients with a VTE had reduced survival, with a median overall survival (OS) of 4.4 months (95% CI 2.2-11.5). The median OS of the patients with incidental VTE was 3.0 months (95% CI 0.1-15.0), which was not different from the median OS of the patients with symptomatic VTE (5.0 months; 95% CI 2.1-14.5). The median OS was 11.9 months (95% CI 8.1-14.7) in the PBC patients with no VTEs.

CONCLUSION

The occurrence of a VTE event in a PBC patient within the first months of the disease is associated with significantly increased mortality.

Treatment-related frequency of venous thrombosis in lower esophageal, gastro-esophageal and gastric cancer--a clinical prospective study of outcome and prognostic factors

INTRODUCTION

Prospective studies of chemotherapy-associated VTE in cancer patients undergoing neoadjuvant chemotherapy in combination with curative intended surgery have not been reported for upper gastrointestinal cancer. In this clinical prospective study, we sought to estimate the incidence of VTE in esophagogastric cancer (OEC) patients scheduled for a specific perioperative chemotherapy regime: oxaliplatin, capecitabine, and epirubicin, (EXE) and curative intended surgery.

MATERIAL AND METHODS

A total of 129 consecutive OEC patients were examined using state-of-the-art bilateral compression ultrasound (biCUS) for deep vein thrombosis (DVT) before undergoing preoperative chemotherapy, surgery, and postoperative chemotherapy. In addition 79 were also consecutively scanned at baseline for pulmonary embolism (PE) using state-of-the-art computer tomography pulmonary angiography (CTPA).

RESULTS

There were 21 VTE cases throughout the course of treatment (16%, 95% confidence interval [95% CI]: 10 - 24%) among the patients examined using both biCUS and CTPA. Fourteen of 21 VTE was incidental (68%, 95% CI: 43 -85) and 7 VTE events was symptomatic (33%, 15 - 57). The median overall survival was 18months (95% CI: 13 - 24) in patients without any VTE and 14months (95% CI: 7 -30, P = 0.820) in patients with VTE. The cancer stage (adjusted odds ratio [OR]: 5.2, 95% CI: 1 - 21, p=0.002) and gastric cancer (OR 6.4, 95% CI: 2 - 21, P = 0.002) was a significant predictor of VTE.

CONCLUSION

The incidence of VTE in patients undergoing EXE neoadjuvant chemotherapy was high, particularly among patients with initial stage III and IV cancers. In addition, a substantial number of chemotherapy-related VTE cases were asymptomatic.

Computed tomography pulmonary angiography: more than a screening tool for pulmonary embolus

BACKGROUND

Traumatically injured patients have multiple causes for acute respiratory decompensation. We reviewed the use of computed tomography pulmonary angiography (CTPA) in critically injured patients to evaluate the results and impact on patient care.

METHODS

The charts of trauma patients (age >16 years) admitted to our intensive care unit for greater than 48 hours, who underwent CTPA for acute respiratory decompensation, were reviewed to determine the results of these studies and the effect on patient care.

RESULTS

We identified 188 patients who underwent CTPA for acute physiologic changes. Pertinent clinical finding were identified in 95% of studies and included atelectasis/collapse (56%), pleural effusion (18%), pneumonia (15%), and pulmonary embolus (18%). These results prompted interventions designed to improve patient outcome. The most frequent interventions were modifications of ventilator therapy (52%), antibiotic therapy (28%), mini-bronchoalveolar lavage (15%), or bronchoscopy (15%). Diagnostic agreement between chest x-ray and CTPA was poor to moderate (κ = 0.013-0.512).

CONCLUSIONS

Computed tomography pulmonary angiography is valuable in the evaluation of cardiopulmonary deterioration in critically ill traumatically injured patients. Computed tomography pulmonary angiography offers the ability to identify causes of acute physiologic changes not detected using standard chest x-ray. The results of these studies provide insight into the underlying pathophysiology and offer an opportunity to direct subsequent patient care.

Performance of perfusion-weighted Fourier decomposition MRI for detection of chronic pulmonary emboli

PURPOSE

To evaluate the test performance of perfusion-weighted Fourier-decomposition (pw-FD) magnetic resonance imaging (MRI) in comparison to dynamic contrast-enhanced (DCE)-MRI as a reference standard in patients with known or suspected chronic pulmonary embolism (PE).

MATERIALS AND METHODS

In 64 patients, chronic PE was ruled out or confirmed by DCE-MRI using a time-resolved angiography with stochastic trajectories (TWIST) sequence in one breath-hold. Pw-FD-MRI was performed using a 2D fast low-angle shot (FLASH) sequence in free-breathing. After a nonrigid image registration, FD was applied to generate pw-images. Lungs were scored by two radiologists (2 and 12 years of lung MRI experience) visually for each lobe and segment for hypoperfused areas. For intra- and interobserver variability, the MR images were analyzed 2 months after the first analysis, blinded to the results of the first reader.

RESULTS

PE was diagnosed by DCE-MRI in 39 patients. For the pw-FD MRI sensitivity, specificity, accuracy, and positive and negative predictive value for diagnosis of PE were 100%, 95%, 98%, 98%, and 100% on a per-patient basis, 94%, 94%, 94%, 95%, 94% on a per-lobe basis, and 82%, 92%, 88%, 88%, 88% on a segmental basis, respectively. Detection of subsegmental and segmental hypoperfusion using pw-FD MRI showed a moderate agreement with DCE-MRI (kappa of 0.68; 95% confidence interval: 0.64; 0.72).

CONCLUSION

Pw-FD of the lung is a feasible test to diagnose chronic PE on a per-patient level during free-breathing without the use of ionizing radiation or contrast agents.

Noncontrast perfusion single-photon emission CT/CT scanning: a new test for the expedited, high-accuracy diagnosis of acute pulmonary embolism

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 &gt; 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.

Clinical consequences of an indeterminate CT pulmonary angiogram in cancer patients

Our aim was to evaluate clinical management and outcomes in cancer patients who had an indeterminate Computed Tomographic Pulmonary Angiogram (CTPA) for the assessment of pulmonary embolus. We reviewed 1000 CTPA studies and identified 251 limited (indeterminate) CTPA. We examined follow-up imaging and reviewed clinical management decisions and any positive diagnosis of venous thromboembolic disease (VTE) within the subsequent 90 days. 60 patients (23.9%) had a follow-up imaging study within five days. 8 had a positive study for VTE disease within 5 days. 3 patients (1.2%) were placed on anticoagulation therapy based on the limited CT result.

Evaluation of imaging quality of pulmonary 64-MDCT angiography in pregnancy and puerperium

OBJECTIVE

The aim of this study was to quantitatively and qualitatively evaluate pulmonary 64-MDCT angiography image quality in pregnancy and puerperium, compared with female nonpregnant control subjects.

MATERIALS AND METHODS

The study group comprised 124 consecutive pregnant and postpartum women and 124 female nonpregnant control subjects who presented with suspected pulmonary embolism. The individual studies were evaluated for subjective and objective diagnostic quality.

RESULTS

Objective measurements of the arterial enhancement in the pulmonary trunk and left and right pulmonary arteries found that there was no statistically significant difference in attenuation values between the pregnant and puerperium group and the control group for pulmonary artery opacification. The mean attenuation in the pulmonary trunk was 270.54 HU in the pregnant group, 277.53 HU in the puerperium group, and 293.90 HU in the control group.

CONCLUSION

We found no significant difference in diagnostic quality of pulmonary CT angiography using MDCT between the study and control groups. The use of MDCT acquisition, faster injection rates, higher contrast medium concentration, and higher trigger levels may decrease the number of nondiagnostic studies in this population. MDCT may be a worthwhile investigation in the majority of pregnant patients with suspected pulmonary embolism.

Prevalence of venous thromboembolism at diagnosis of upper gastrointestinal cancer

BACKGROUND

Venous thromboembolism (VTE) in patients with upper gastrointestinal (GI) cancer increases morbidity and mortality. This study aimed to determine the prevalence of VTE at diagnosis of upper GI cancer.

METHODS

Patients admitted between February 2008 and February 2011 with upper GI cancer (pancreatic, extrahepatic biliary, lower oesophageal, gastro-oesophageal junction or gastric cancer) were investigated in a cross-sectional cohort study. At cancer diagnosis, all patients were examined for deep vein thrombosis (DVT) by means of bilateral compression ultrasonography. From February 2009 and onwards, computed tomographic pulmonary angiography (CTPA) was also performed for the diagnosis of pulmonary embolism (PE).

RESULTS

Some 250 patients had ultrasonography; CTPA was performed in 143 patients on admission. DVT was detected in 13 (5·2 per cent) of the 250 patients, eight (3·2 per cent) of whom were asymptomatic. DVT was correlated with tumour location in the pancreaticobiliary tract (odds ratio (OR) 6·27, 95 per cent confidence interval 1·18 to 33·38; P = 0·031) and tumour stage IV (OR 19·34, 2·33 to 160·70; P = 0·006). PE was detected in 11 (7·7 per cent) of 143 patients, eight (5·6 per cent) of whom were asymptomatic. PE embolism was also significantly more common in patients with pancreaticobiliary tract cancer (OR 7·81, 1·28 to 47·62; P = 0·026) and in those with stage IV disease (OR 17·19, 1·83 to 161·50; P = 0·013).

CONCLUSION

The prevalence of VTE at cancer diagnosis was significantly higher in patients with pancreaticobiliary tract cancer than in those with other forms of upper GI cancer, and in patients with advanced cancer stage.

Imaging diagnosis of acute pulmonary embolism

Pulmonary embolism represents a major public healthcare problem and it also imposes frequent clinical diagnostic issues. Despite the availability of the D-dimer tests, imaging remains the mainstay for its diagnosis. Computed tomography pulmonary angiography (CTPA) is now the most widely used diagnostic test and its utility has been well validated in a large number of trials. Nuclear medicine techniques, which are also well established, are now used significantly less frequently. Magnetic resonance pulmonary angiography is developing as an alternative to CTPA in patients who have contraindications to iodinated contrast media. Catheter pulmonary angiography remains the gold standard, although it is being used increasingly less frequently. In this article, we review the current knowledge on the imaging diagnosis of acute pulmonary embolism with special emphasis on the noninvasive techniques.

Dual-energy CT based vascular iodine analysis improves sensitivity for peripheral pulmonary artery thrombus detection: an experimental study in canines

PURPOSE

To evaluate the performance of dual-energy CT (DECT) based vascular iodine analysis for the detection of acute peripheral pulmonary thrombus (PE) in a canine model with histopathological findings as the reference standard.

MATERIALS AND METHODS

The study protocol was approved by our institutional animal committee. Thrombi (n = 12) or saline (n = 4) were intravenously injected via right femoral vein in sixteen dogs, respectively. CT pulmonary angiography (CTPA) in DECT mode was performed and conventional CTPA images and DECT based vascular iodine studies using Lung Vessels application were reconstructed. Two radiologists visually evaluated the number and location of PEs using conventional CTPA and DECT series on a per-animal and a per-clot basis. Detailed histopathological examination of lung specimens and catheter angiography served as reference standard. Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) of DECT and CTPA were calculated on a segmental and subsegmental or more distal pulmonary artery basis. Weighted κ values were computed to evaluate inter-modality and inter-reader agreement.

RESULTS

Thirteen dogs were enrolled for final image analysis (experimental group = 9, control group = 4). Histopathological results revealed 237 emboli in 45 lung lobes in 9 experimental dogs, 11 emboli in segmental pulmonary arteries, 49 in subsegmental pulmonary arteries, 177 in fifth-order or more distal pulmonary arteries. Overall sensitivity, specificity, accuracy, PPV, and NPV for CTPA plus DECT were 93.1%, 76.9%, 87.8%, 89.4%, and 84.2% for the detection of pulmonary emboli. With CTPA versus DECT, sensitivities, specificities, accuracies, PPVs, and NPVs are all 100% for the detection of pulmonary emboli on a segmental pulmonary artery basis, 88.9%, 100%, 96.0%, 100%, and 94.1% for CTPA and 90.4%, 93.0%, 92.0%, 88.7%, and 94.1% for DECT on a subsegmental pulmonary artery basis; 23.8%, 96.4%, 50.4%, 93.5%, and 36.7% for CTPA and 95.9%, 75.5%, 88.2%, 86.5%, and 91.9% on a sub-subsegmental and more distal pulmonary artery basis, respectively. Good inter-modality (κ = 0.65, P<0.001) and inter-reader (κ = 0.70, P<0.001) agreement were observed.

CONCLUSION

With histopathological findings as the reference standard, DECT based vascular iodine analysis improves the sensitivity for detecting peripheral PE compared with CTPA, albeit at the price of decreased specificity and PPV.

The role of thoracic ultrasonography in the diagnosis of pulmonary embolism

OBJECTIVES:

The diagnosis of pulmonary embolism (PE) is still a problem especially at emergency units. The purpose of study was to determine the diagnostic accuracy of thoracic ultrasonography (TUS) in patients with PE.

METHODS:

In this prospective study, 50 patients with suspected PE were evaluated in Department of Pulmonary Diseases of a Training and Reasearch Hospital between January 2010 and July 2011. At the begining, TUS was performed by a chest physician, subsequently for definitive diagnosis computed tomography pulmonary angiography were performed in all cases as a reference method. Other diagnostic procedures were examination of serum d-dimer levels, echocardiography, and venous doppler ultrasonography of the legs. Both chest physician and radiologist were blinded to the results of other diagnostic method. Diagnosis of PE was suggested if at least one typical pleural-based/subpleural wedge-shaped or round hypoechoic lesion with or without pleural effusion was reported by TUS. Presence of pure pleural effusion or normal sonographic findings were accepted as negative TUS for PE.

RESULTS:

PE was diagnosed in 30 patients. It was shown that TUS was true positive in 27 patients and false positive in eight and true negative in 12 and false negative in three. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of TUS in diagnosis of PE for clinically suspected patients were 90%, 60%, 77.1%, 80%, and 78%, respectively.

CONCLUSIONS:

TUS with a high sensitivity and diagnostic accuracy, is a noninvasive, widely available, cost-effective method which can be rapidly performed. A negative TUS study cannot rule out PE with certainty, but positive TUS findings with moderate/high suspicion for PE may prove a valuable tool in diagnosis of PE at bedside especially at emergency setting, for critically ill and immobile patients, facilitating immediate treatment decision.

Iterative reconstructed ultra high pitch CT pulmonary angiography with cardiac bowtie-shaped filter in the acute setting: effect on dose and image quality

PURPOSE

To evaluate the effect of a cardiac bowtie-shaped filter in an ultra high pitch CTPA protocol at 100 kV on image quality and radiation dose.

MATERIALS AND METHODS

Retrospective study of 100 patients referred for CTPA. 50 patients scanned with a standard 100 kV protocol at pitch 2.8 (Protocol A) and 50 patients scanned with a 100 kV protocol at pitch 3.2 with a cardiac bowtie-shaped filter (Protocol B). All other scanning parameters kept constant. Images from both groups reconstructed with filtered back projection and iterative reconstruction. Central pulmonary vessel attenuation and background noise were quantitatively measured and signal-to-noise (SNR) and contrast-to-noise (CNR) were calculated. Two radiologists performed qualitative assessment grading visualization of the pulmonary vasculature and noise level. CTDIvol and DLP were recorded and effective dose was calculated.

RESULTS

CTDIvol, DLP and effective dose were significantly (p<0.0001) lower in Protocol B (2.3 ± 0.5 mGy, 78.4 ± 16.5 mGycm, 1.4 ± 0.3 mSy, respectively) compared to Protocol A (4.3 ± 0.5 mGy, 152.0 ± 19.6 mGycm, 2.7 ± 0.3 mSy, respectively). Protocol B had significantly (p<0.0001) higher noise than Protocol A (23.8 ± 6.9 HU vs 36.8 ± 7.3 HU) and lower SNR (11.8 ± 3.7 HU vs 19.2 ± 8.1 HU) and CNR (10.3 ± 3.7 HU vs 24.9 ± 13.4 HU) but there was no significant difference in the subjective visualization of the pulmonary vasculature (p=0.63). Furthermore, iterative reconstruction significantly (p<0.0001) improves image noise (29.4 ± 5.5 HU from 36.8 ± 7.3 HU).

CONCLUSION

The addition of a cardiac bowtie-shaped filter with an ultra high pitch CTPA protocol at 100 kV resulted in a 48% dose reduction without significantly affecting diagnostic image quality. In addition, the use of iterative reconstruction significantly improves image quality by reducing noise permitting the possibility for further dose reduction strategies.

Prognostic value of computed tomographic pulmonary angiography and the pulmonary embolism severity index in patients with acute pulmonary embolism

Pulmonary embolism is a serious and potentially fatal disorder. Pulmonary embolism risk stratification may allow early hospital discharge and outpatient treatment for low-risk patients. Also, it may prevent death by early medical intervention in high-risk groups. We evaluated objectively confirmed pulmonary embolism in 126 patients by multidetector computed tomographic pulmonary angiography at a single center from January 2008 to January 2010. The Pulmonary Severity Embolism Index (PESI), the right ventricle (RV) to left ventricle (LV) diameter (RV/LV) ratio and the vascular obstruction index (VOI) were derived from data extracted from electronic hospital records and image database. A total of six out of 96 patients (6.3%) died during follow-up. There was an association between PESI and mortality (P-value < 0.001 χ² test). PESI class I-II had a 100% negative predictive value for death in 90 days. No association was found between the RV/LV ratio, the VOI and mortality (P-value > 0.05 χ² test). Also, no association was found between the RV/LV ratio and the VOI and PESI (P-value > 0.05 χ² test). PESI is an accurate tool for pulmonary embolism prognostic stratification. It safely discriminates low-risk from high-risk patients regarding death outcome. We were unable to demonstrate an association between image scores and mortality.