Standard Computed Tomography Pulmonary Angiography Research Articles

Diagnostic test accuracy of imaging modalities for adults with acute pulmonary embolism: A systematic review and meta-analysis

ObjectivesThis systematic review and meta-analysis aimed to evaluate the current literature on diagnostic test accuracy (DTA) of imaging modalities for adults with acute pulmonary embolism (APE). BackgroundMedical imaging plays an integral role in evaluating and managing those with APE. Guidance for imaging modality use for APE diagnosis varies due to a lack of clinical standardisation. Despite this, CTPA remains the first-line imaging modality used by clinicians. MethodsA literature search of PubMed, EMBASE, Trove and Mednar databases (2012-2020; English language) was performed. Studies assessing the DTA of imaging modalities for APE diagnosis were included. DTA studies methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2 tool). Results of eligible studies were pooled using random or fixed effects modelling the calculate the pooled DTA of explored imaging modalities for APE. The Higgins I2 test were performed to assess between study heterogeneity. Results10 Studies, involving 998 participants, were enrolled and pooled using the random effects model. Of the explored modalities, magnetic resonance imaging (MRI), specifically pulmonary MRI and magnetic resonance pulmonary angiography (MRPA) exhibited the highest pooled DTA. Sensitivity, specificity, negative likelihood ratio, positive likelihood ratio and diagnostic odds ratio for MRPA were 0.952 (95% CI, 0.881 to 0.987), 0.857 (95% CI, 0.637 to 0.97), 5.631 (95% CI, 2.163 to 14.659), 0.06 (95% CI, 0.007 to 0.537) and 80.310 (95% CI, 15.607 to 413.25) respectively. Based on the QUADAS-2 criteria, most studies presented low to moderate risk of bias and concern regarding applicability. ConclusionThe explored ultrasound and MRI protocols which exhibit a lower radiation burden when compared to the current gold standard computed tomography pulmonary angiography (CTPA), have acceptable diagnostic accuracy for APE and can be useful in certain situations.

Dual-energy computed tomography pulmonary angiography with ultra-low dose contrast administration: Comparison of image quality with standard computed tomography pulmonary angiography.

This study aims to compare quantitative and qualitative image quality between standard computed tomography pulmonary angiography and dual-energy computed tomography pulmonary angiography protocols. Between September 2017 and August 2018, a total of 91 consecutive patients (34 males, 57 females; mean age: 65.9±15 years; range, 37 to 91 years) who were referred for computed tomography pulmonary angiography were randomly imaged with either a standard or dual-energy protocol. Standard protocol (n=49) was acquired with a 64-slice multidetector computed tomography scanner using 60 mL contrast media (18 g iodine). A third-generation dual-energy computed tomography scanner was utilized to acquire dual-energy computed tomography pulmonary angiography and simultaneous lung perfusion imaging (n=42), which required 40 mL contrast media (12 g iodine). Two radiologists reviewed images separately to determine interobserver variability. Attenuation and noise in three central and two segmental pulmonary arteries were measured; signal-to-noise ratio and contrast-to-noise ratio were calculated. A five-point scale was utilized to evaluate image quality and image noise qualitatively. The standard protocol required a significantly higher amount of iodine. Comparison of two groups employing quantitative measurements (attenuation value in five pulmonary arteries, mean attenuation value, mean background noise, signal-to-noise ratio, and contrast-to-noise ratio) and employing qualitative measurements (five-point scale scores of image quality and image noise) revealed no significant difference between dual-energy and standard groups (p>0.05). Qualitative and quantitative evaluations demonstrated low interobserver variability. Dual-energy computed tomography pulmonary angiography protocol delivers image quality equal to standard protocol, while requiring less amount of iodinated contrast medium and providing simultaneous lung perfusion imaging to contribute the diagnosis of pulmonary embolism.

Frequency and Anatomical Distribution of Pulmonary Embolism on CT Pulmonary Angiography

Background: Pulmonary embolism, with its growing prevalence, has become a potentially life-threatening medical condition with crucial symptoms. However, prognosis is good if timely diagnosis is made and to the level of segmental and sub segmental arteries as well. Standard computed tomography pulmonary angiography (CTPA) is thus used to diagnose acute pulmonary embolism. Objective: The primary objective of the current study was to determine and investigate the anatomical distribution frequency of pulmonary emboli, where segmental, sub segmental, and lobar arteries on CT pulmonary angiography are included. Methodology: In a descriptive cross-sectional study, single-centered studies and CTPA scans of 98 patients were included. Data was obtained from Shalimar Hospital and University of Lahore – Teaching Hospital, Lahore, Pakistan. Sample size included patients of all age groups with suspected pulmonary embolism, with no differentiation of male or female samples. Results: According to statistics and analysis, the current study results indicated the presence of pulmonary embolism in 36 patients and its absence in 62 patients. Results indicated that amongst the 98 patients scanned, the highest frequency of pulmonary emboli was found in the pulmonary trunk and lobar artery in 8 patients (8.2%). Furthermore, CTPA of the participants detected pulmonary emboli in segmental and sub-segmental arteries of 5 patients (5.1%), with another 2 patients showing pulmonary emboli in only the sub-segmental artery (2.0%). Another 2-2 patients showed pulmonary emboli in lobar and segmental artery and lobar, segmental and sub-segmental artery respectively (2.0%, 2.0%). Conclusion: The largest number of pulmonary emboli were found in the pulmonary trunk, followed by emboli of segmental and lobar arteries in patients. It is concluded that CTPA evaluates pulmonary embolism with great precision and anatomical distribution localized main trunk, and pulmonary artery emboli along with lobar, segmental and sub-segmental artery emboli. Keywords: Computed Tomography Pulmonary Angiography (CTPA), pulmonary emboli, segmental artery, sub segmental artery, lobar arteries DOI: 10.7176/JHMN/100-02 Publication date: May 31 st 2022

Comparison of high-pitch prospective electrocardiogram-gated pulmonary CT angiography with standard CT pulmonary angiography on dual-source CT for detection of subsegmental pulmonary embolism in patients suspected of acute pulmonary embolism.

PurposeObjective of this study was to compare high-pitch prospective electrocardiogram (ECG)-gated computed tomography (CT) pulmonary angiography (HP-PECG-gated CTPA) with standard-pitch non-ECG-gated CT pulmonary angiography (SP-NECG-gated CTPA) on 128-slice dual-source CT (DSCT) for the detection of subsegmental pulmonary embolism (SSPE) in patients suspected of acute pulmonary embolism (APE) with radiation and contrastoptimized protocols. Cardiac-related motion artefacts, lung image quality, and quantitative parameter (pulmonary arterial enhancement, radiation exposure, and contrast) volumes were also compared.Material and methodsThis prospective study enrolled 87 patients clinically suspected of APE and randomly distributed to either group by software. Two radiologists blinded to each other interpreted the images for assessment of SSPE, image quality, and quantitative parameters.ResultsSSPE was diagnosed in 15/44 (34.09%) patients in HP-PECG-gated CTPA, in comparison to 8/43 (18.60%) patients in SP-NECG-gated CTPA. Cardiac motion-related artefacts (blurring of bronchovascular structures and double-line artefacts) were statistically significantly less, with p-value < 0.05. Lung image quality was also better, with p-value < 0.001. Effective radiation dose and contrast volume in HP-PECG-gated CTPA were (2.54 ± 0.80 mSv, 45.05 ± 6 ml) versus SP-NECG-gated CTPA (3.17 ± 1.20 mSv, 74.19 ± 7.63 ml) with p-values of 0.007 and 0.001, respectively.ConclusionsRadiation and contrast volume-optimized HP-PECG-gated CTPA provides reduced cardiac motion related artefacts of pulmonary arteries, which allows enhanced detection of SSPE. It also provides better image quality of lung and parenchyma with lower radiation exposure and less contrast volume

Diagnostic Performance of a Contrast-Enhanced Ultra-Low-Dose High-Pitch CT Protocol with Reduced Scan Range for Detection of Pulmonary Embolisms

(1) Background: To evaluate the diagnostic performance of a simulated ultra-low-dose (ULD), high-pitch computed tomography pulmonary angiography (CTPA) protocol with low tube current (mAs) and reduced scan range for detection of pulmonary embolisms (PE). (2) Methods: We retrospectively included 130 consecutive patients (64 ± 16 years, 69 female) who underwent clinically indicated high-pitch CTPA examination for suspected acute PE on a 3rd generation dual-source CT scanner (SOMATOM FORCE, Siemens Healthineers, Forchheim, Germany). ULD datasets with a realistic simulation of 25% mAs, reduced scan range (aortic arch—basal pericardium), and Advanced Modeled Iterative Reconstruction (ADMIRE®, Siemens Healthineers, Forchheim, Germany) strength 5 were created. The effective radiation dose (ED) of both datasets (standard and ULD) was estimated using a dedicated dosimetry software solution. Subjective image quality and diagnostic confidence were evaluated independently by three reviewers using a 5-point Likert scale. Objective image quality was compared using noise measurements. For assessment of diagnostic accuracy, patients and pulmonary vessels were reviewed binarily for affection by PE, using standard CTPA protocol datasets as the reference standard. Percentual affection of pulmonary vessels by PE was computed for disease severity (modified Qanadli score). (3) Results: Mean ED in ULD protocol was 0.7 ± 0.3 mSv (16% of standard protocol: 4.3 ± 1.7 mSv, p < 0.001, r > 0.5). Comparing ULD to standard protocol, subjective image quality and diagnostic confidence were comparably good (p = 0.486, r > 0.5) and image noise was significantly lower in ULD (p < 0.001, r > 0.5). A total of 42 patients (32.2%) were affected by PE. ULD protocol had a segment-based false-negative rate of only 0.1%. Sensitivity for detection of any PE was 98.9% (95% CI, 97.2–99.7%), specificity was 100% (95% CI, 99.8–100%), and overall accuracy was 99.9% (95% CI, 98.6–100%). Diagnoses correlated strongly between ULD and standard protocol (Chi-square (1) = 42, p < 0.001) with a decrease in disease severity of only 0.48% (T = 1.667, p = 0.103). (4) Conclusions: Compared to a standard CTPA protocol, the proposed ULD protocol proved reliable in detecting and ruling out acute PE with good levels of image quality and diagnostic confidence, as well as significantly lower image noise, at 0.7 ± 0.3 mSv (84% dose reduction).

Task-based assessment on various optimization protocols of computed tomography Pulmonary Angiography examination

This prospective study was designed to assess CT performance by using the task-based image quality assessment and to identify the influence of iterative reconstruction (IR) algorithm, tube potential and pitch factor selection on dose and image quality during Computed Tomography Pulmonary Angiography (CTPA) examination. An image quality phantom, Catphan-600 was utilized in this study for assessing the image quality of CTPA protocols under 128-multislice CT scanner (Philips Brilliance iCT, USA). The standard CTPA protocols were altered on its tube potential, pitch factor and iterative reconstruction algorithm (IR). Three different levels of iDose, an IR algorithm were measured in this study. The result was presented in term of signal to noise ratio (SNR), contrast to noise ratio (CNR), noise power spectrum (NPS) and target transfer function (TTF). A massive improvement of the CNR and distortion of noise texture were observed with increasing the IR algorithm level. Noise value reduction was significantly achieved by increasing the tube potential selection although there are no changes in TTF values. The alteration of pitch factor provides some fluctuation on both NPS and TTF values. In conclusion, the task-based measurement was performed, and this technique allow for characterizing the image quality with a different type of quantitative measurement for local CTPA protocols.

Diagnostic accuracy of combined thoracic and cardiac sonography for the diagnosis of pulmonary embolism: A systematic review and meta-analysis.

Computed tomography pulmonary angiography (CTPA) is the diagnostic standard for pulmonary embolism (PE), but is unavailable in many low resource settings. We evaluated the evidence for point of care ultrasound as an alternative diagnostic. Using a PROSPERO-registered, protocol-driven strategy (https://www.crd.york.ac.uk/PROSPERO, ID = CRD42018099925), we searched MEDLINE, EMBASE, and CINHAL for observational and clinical trials of cardiopulmonary ultrasound (CPUS) for PE. We included English-language studies of adult patients with acute breathlessness, reported according to PRISMA guidelines published in the last two decades (January 2000 to February 2020). The primary outcome was diagnostic accuracy of CPUS compared to reference standard CTPA for detection of PE in acutely breathless adults. We identified 260 unique publications of which twelve met all inclusion criteria. Of these, seven studies (N = 3872) were suitable for inclusion in our meta-analysis for diagnostic accuracy (two using CTPA and five using clinically derived diagnosis criterion). Meta-analysis of data demonstrated that using cardiopulmonary ultrasound (CPUS) was 91% sensitive and 81% specific for pulmonary embolism diagnosis compared to diagnostic standard CTPA. When compared to clinically derived diagnosis criterion, CPUS was 52% sensitive and 92% specific for PE diagnosis. We observed substantial heterogeneity across studies meeting inclusion criteria (I2 = 73.5%). Cardiopulmonary ultrasound may be useful in areas where CTPA is unavailable or unsuitable. Interpretation is limited by study heterogeneity. Further methodologically rigorous studies comparing CPUS and CTPA are important to inform clinical practice.

TO USE OR NOT USE PATIENT SHIELDING ON PREGNANT WOMEN UNDERGOING CT PULMONARY ANGIOGRAPHY: A PHANTOM STUDY.

Pregnancy increases the risk of pulmonary embolism. Computed tomography pulmonary angiography (CTPA) is used for diagnosis. CT generates ionising radiation, and thus, abdominal shielding may be used. This phantom study investigated the effects of patient shielding and scan length reduction on the fetal and maternal ionising radiation dose from CTPA. The absorbed dose to the fetus was measured using thermoluminescent dosemeters. Estimated effective doses to the pregnant patient were based on the dose-length products. Shielding increased both the effective dose to the patient by 47% and the mean absorbed dose to the fetus (0.10 vs. 0.12 mGy; p < 0.001) compared with unshielded standard CTPA, as it affected the automatic exposure control. Shielded short CTPA marginally lowered only the mean fetal absorbed dose (0.03 vs. 0.02 mGy; p = 0.018). Shortening the scan reduced the fetal absorbed dose most effectively by 70% (0.10 vs. 0.03 mGy; p = 0.006), compared with the standard unshielded scan. Shielding modestly reduces fetal radiation dose but may compromise automatic exposure control, possibly increasing the maternal and fetal radiation dose. Shortening the scan is beneficial, assuming anatomical coverage is secured.

Arterial attenuation in individualized computed tomography pulmonary angiography injection protocol adjusted based on the patient's body mass index

Background:The aim of this study was to optimize computed tomography pulmonary angiography (CTPA) protocols with regard to improve vascular attenuation without increasing contrast media (CM) volumes. Therefore, we compared the standard CTPA protocol to an individualized contrast media injection protocols adjusted for the patient's body mass index (BMI).Materials and Methods:Two groups of 295 patients with suspected pulmonary embolism (PE) have been receiving CTPA. Group 1 received a standard protocol without taking patient's BMI into account. Group 2 received a CTPA scan, where dose and flow rate of CM injections were adjusted for the patient's BMI. Images were retrospectively analyzed by drawing regions of interests in defined positions in the superior vena cava, descending aorta, the pulmonary main trunk as well as the left and right lower lobe arteries. Intravascular attenuation, contrast volumes, and flow rates were compared using unpaired t-tests. Furthermore, a qualitative image analysis was performed by two experienced readers blinded for the protocol used for image acquisition to evaluate the image quality and arterial attenuation.Results:Patient's BMI was similar in both the groups (27.5 ± 1.5 kg/m2 vs. 28.4 ± 2.1 kg/m2; P = 0.67). Contrast volumes were lower (54.2 ± 4.8 ml vs. 55 ml; P < 0.05), and flow rates (4.1 ± 0.3 ml/s vs. 3.5 ml/s; P < 0.05) were significantly higher in the individualized protocol. The qualitative image analysis yielded an agreement on diagnostic interpretability in the individualized and standard group of 49% and 51% (95% Wilson confidence interval for mean), respectively.Conclusion:An individualized CTPA protocol based on the patient's BMI reduced the contrast media volume and led to an increased pulmonary artery enhancement improving image quality, particularly in the evaluation of the peripheral pulmonary arteries. Thus, contrast media volumes in CTPA should be adjusted for the patient's BMI.

Usefulness of standard computed tomography pulmonary angiography performed for acute pulmonary embolism for identification of chronic thromboembolic pulmonary hypertension: results of the InShape III study.

Chronic thromboembolic pulmonary hypertension (CTEPH) is often diagnosed after a long delay, even though signs may already be present on the computed tomography pulmonary angiogram (CTPA) used to diagnose a preceding acute pulmonary embolism (PE). In this setting of suspected acute PE, we evaluated the diagnostic accuracy of dedicated CTPA reading for the diagnosis of already existing CTEPH. Three blinded expert radiologists scored radiologic signs of CTEPH on initial CTPA scans with confirmed acute PE in 50 patients who were subsequently diagnosed with CTEPH during follow-up (cases), and in 50 patients in whom sequential echocardiograms performed >2 years after the acute PE diagnosis did not show any signs of pulmonary hypertension (controls). All 50 control index CTPA scans had signs of right ventricular (RV) overload. Sensitivity and specificity of expert CTPA reading was calculated, and best-predicting radiologic parameters were identified. The overall expert reading yielded a sensitivity of 72% (95% confidence interval [CI] 58%-84%) and a specificity of 94% (95% CI 83%-99%) for CTEPH diagnosis. Multivariate analysis identified 6 radiologic parameters as independent predictors: intravascular webs; pulmonary artery retraction or dilatation; bronchial artery dilatation; right ventricular (RV) hypertrophy; and interventricular septum flattening. The presence of 3 or more these parameters was associated with a sensitivity of 70% (95% CI 55%-82%), a specificity of 96% (95% CI 86%-100%), and a c-statistic of 0.92. Standardized reading of CTPA scans performed for acute PE can be useful for the diagnosis of CTEPH when structured identification of 6 characteristics is employed during interpretation. The use of this strategy may help reduce diagnostic delay of CTEPH.

Magnetic resonance angiography imaging of pulmonary embolism using agents with blood pool properties as an alternative to computed tomography to avoid radiation exposure

PurposeTo evaluate the feasibility and accuracy of a combined magnetic resonance angiography (MRA) - magnetic resonance venography (MRV) protocol using contrast agents with blood pool properties, gadofosveset trisodium and gadobenate dimeglumine, in the evaluation of pulmonary embolus (PE) and deep venous thrombosis (DVT) as compared to the standard clinical reference imaging modalities; computed tomography pulmonary angiography (CTPA) and color-coded Duplex ultrasound (DUS). Materials and methodsThis prospective clinical study recruited patients presenting to the emergency department with clinical suspicion for PE and scheduled for a clinically indicated CTPA. We performed both MRA of the chest for the evaluation of PE as well as MRV of the pelvis and thighs to evaluate for DVT using a single contrast injection. MRA-MRV data was compared to the clinical reference standard CTPA and DUS, respectively. ResultsA total of 40 patients were recruited. The results on a per-patient basis comparing MRA to CTPA for pulmonary embolus yielded 100% sensitivity and 97% specificity. There was a small subset of patients that underwent clinical DUS to evaluate for DVT, which demonstrated a sensitivity and specificity of 100% for MRV. ConclusionsThis single-center, preliminary study using contrast agents with blood pool properties to perform a relatively rapid combined MRA-MRV exam to image for PE and above knee DVT shows potential as an alternative imaging choice to CTPA. Further large-scale, multicentre studies are warranted.

P1625Identification of chronic thromboembolic pulmonary hypertension on standard computed tomography pulmonary angiography for suspected acute pulmonary embolism

Background: Chronic thromboembolic pulmonary hypertension (CTEPH) is often diagnosed after a long delay, even though signs of CTEPH may already be present on the computed tomography pulmonary angiogram (CTPA) used to diagnose a preceding acute pulmonary embolism (PE). Diagnostic delay may be associated with worse prognosis. In this study we evaluated the diagnostic accuracy of extensive CTPA reading for predicting a future CTEPH diagnosis after acute PE. Method(s): Three expert radiologists scored radiological signs of CTEPH on CTPA performed for suspected acute PE in 50 PE patients who were subsequently diagnosed with CTEPH during follow-up with right heart catheterisation (cases), and in 50 PE patients, in whom sequential echocardiograms performed >2 years after the acute PE diagnosis had not shown any signs of pulmonary hypertension (controls). Cases and controls were matched on RV-to-LV ratio on baseline CTPA. Sensitivity and specificity of expert CTPA reading for predicting future CTEPH was calculated, and best predicting radiological parameters were identified by conditional backward multivariate analysis. Result(s): 75% of cases had signs of acute PE and 94% signs of chronic PE and/or PH. The overall expert adjudication yielded a sensitivity of 72% (95% CI 58-84%) and a specificity of 94% (95% CI 83-99%) for a future CTEPH diagnosis. We identified six objective, independent radiological predictors of CTEPH: intravascular webs, pulmonary artery retraction or dilatation, bronchial artery dilatation, right ventricle hypertrophy and interventricular septum flattening (Figure 1). The presence of >=3 of these parameters was associated with a sensitivity of 70% (95% CI 55-82%), a specificity of 96% (95% CI 86-100%) and a c-statistic of 0.92. Conclusion(s): In our cohort, expert radiologists identified 36 out of 50 PE patients with a future CTEPH diagnosis. The most probable explanation is that most of them already had CTEPH at the moment of the PE diagnosis. Our findings support the hypothesis that dedicated CTPA reading in patients with confirmed PE may lead to faster CTEPH diagnosis.

Accuracy and reproducibility of CT right-to-left ventricular diameter measurement in patients with acute pulmonary embolism.

BackgroundRight ventricular (RV) dysfunction caused by acute pulmonary embolism (PE) is associated with poor short- and long-term prognosis. RV dilatation as a proxy for RV dysfunction can be assessed by calculating the right-to-left ventricle diameter (RV/LV) ratio on standard computed tomography pulmonary angiography (CTPA) images. It is unknown whether dedicated training is required to accurately and reproducibly measure RV/LV ratio therefore we aimed to assess these parameters in residents in internal medicine without experience in CTPA reading.MethodsCTPA images of 100 patients with PE were assessed by three residents after single instruction, and one experienced thoracic radiologist. Maximum diameters were evaluated in the axial view by measuring the distance between the ventricular endocardium and the interventricular septum, perpendicular to the long axis of the heart. RV dilatation was defined as a ratio of ≥1.0. Interobserver accuracy and reproducibility was determined using Kappa statistics, Bland-Altman analysis and Spearman's rank correlation.ResultsThe kappa statistic for the presence of RV dilatation of the residents compared to the experienced radiologist ranged from 0.83–0.94. The average interobserver difference in calculated RV/LV ratio’s (±SD) between the three residents was: -0.01 (SD0.11), 0.07 (SD0.14) and 0.06 (SD0.18) with an overall mean RV/LV diameter ratio of 1.04. In line with this, Spearman's rank correlation coefficients were 0.92, 0.88 and 0.85 respectively indicating very good correlation (p<0.01 for all).ConclusionAfter simple instruction, RV/LV diameter ratio assessment on CTPA images by clinical residents is accurate and reproducible, which is of help in identifying PE patients at risk.

Optimisation of CT pulmonary angiography by applying cardiac CT techniques

Purpose – To reduce effective dose to patients by reducing dose length product (DLP) – To reduce intravenous contrast volume used for computed tomography pulmonary angiography (CTPA) studies – To improve image quality via increased pulmonary arterial enhancement (HU) Methods and materials Twenty-three patients with justified CTPA requests were randomly assigned to study group according to availability of supervising radiologist(s). Twenty-three further consecutive patients who underwent standard protocol CTPA examination were retrospectively assigned to control group during study period. Tube voltage was modified as per body mass index (BMI). Z-axis scan range was limited from lower margin of sternoclavicular joint to upper margin of lowest diaphragm. High flow fixed volume dual pump technique was used with breath hold. Images were acquired using 64 slice Phillips Brilliance CT scanner. Pulmonary arterial opacification was measured at centre of pulmonary trunk and first segmental lower lobar branch. Results All scans were of adequate diagnostic quality. The study group saw reductions in mean DLP of 21% (296.1 milliGray-centimetre [mGy-cm] vs 374.4 mGy-cm), intravenous contrast volume administered of 23% (60 millilitres [mls] vs 78mls). Mean pulmonary arterial opacification was improved by 49% (470 HU vs 316 HU) and mean segmental arterial opacification by 55% (471 HU vs 304 HU) over control group. Conclusion Reduction in CTPA radiation dose and intravenous contrast volume can be achieved by using established cardiac CT techniques while improving image quality at the same time. – To reduce effective dose to patients by reducing dose length product (DLP) – To reduce intravenous contrast volume used for computed tomography pulmonary angiography (CTPA) studies – To improve image quality via increased pulmonary arterial enhancement (HU) Twenty-three patients with justified CTPA requests were randomly assigned to study group according to availability of supervising radiologist(s). Twenty-three further consecutive patients who underwent standard protocol CTPA examination were retrospectively assigned to control group during study period. Tube voltage was modified as per body mass index (BMI). Z-axis scan range was limited from lower margin of sternoclavicular joint to upper margin of lowest diaphragm. High flow fixed volume dual pump technique was used with breath hold. Images were acquired using 64 slice Phillips Brilliance CT scanner. Pulmonary arterial opacification was measured at centre of pulmonary trunk and first segmental lower lobar branch. All scans were of adequate diagnostic quality. The study group saw reductions in mean DLP of 21% (296.1 milliGray-centimetre [mGy-cm] vs 374.4 mGy-cm), intravenous contrast volume administered of 23% (60 millilitres [mls] vs 78mls). Mean pulmonary arterial opacification was improved by 49% (470 HU vs 316 HU) and mean segmental arterial opacification by 55% (471 HU vs 304 HU) over control group. Reduction in CTPA radiation dose and intravenous contrast volume can be achieved by using established cardiac CT techniques while improving image quality at the same time.

Iodine Distribution Map in Dual-Energy Computed Tomography Pulmonary Artery Imaging with Rapid kVp Switching for the Diagnostic Analysis and Quantitative Evaluation of Acute Pulmonary Embolism

To assess the diagnostic value of dual-energy (DE) computed tomography pulmonary angiography (CTPA) for acute pulmonary embolism (PE) using a helical DE scan mode with rapid kVp switching. Seventy-six patients with suspected acute PE underwent DE CTPA. Two readers independently assessed and measured the iodine maps. CTPA images were assessed for the presence, location, and degree of PE as the standard of reference. Iodine maps were used to identify the perfusion defect (PD), and the diagnostic accuracy of iodine maps was calculated. The iodine concentrations of PDs and normal lung parenchyma were also measured and compared. A per-patient analysis showed the 84.6% sensitivity and 96.0% specificity of iodine map for PE, and on per-segment analysis, the sensitivity and specificity for PE were 82.9% and 99.6%, respectively. Intraobserver and interobserver variability correlations were excellent, with k values from 0.806 to 1.000. Quantitative analysis showed there was a significant difference for iodine concentration between circumscribed/patchy PDs or wedge-shaped PDs consistent with PE and normal lung parenchyma (P < .05). The intraobserver reliability of reader 1 was from 0.928 to 0.997, and reader 2 was from 0.912 to 0.995. And, the interobserver reliability between two readers was from 0.967 to 0.999. CTPA based on DE scanning with rapid kVp switching can provide both morphologic analysis and quantitative evaluation of PD related to acute PE in addition to standard CTPA data. Quantification of iodine concentration may be helpful for identifying the presence or absence of PE.

The validity of hyperdense lumen sign in non-contrast chest CT scans in the detection of pulmonary thromboembolism

It is possible to identify high-attenuation clots in pulmonary thromboembolism using non-contrast computed tomography (CT) of the chest. Such detection may be crucial for timely initiation of appropriate therapy. This study was undertaken to determine the validity of the hyperdense lumen (high-attenuation clot) sign in unenhanced chest CT in detecting pulmonary thromboembolism. Non-contrast and contrast-enhanced CT images of the chest of 121 patients who had undergone standard CT pulmonary angiography (pulmonary CTA) were reviewed separately. The absence or presence of luminal hyperdensities within the pulmonary arteries in the non-contrast images was determined. The average CT attenuation differences between the high attenuation clots and pulmonary arteries were computed. Findings in the non-contrast images were correlated with the contrast-enhanced images. Twenty-five patients were positive for pulmonary thromboembolism in the pulmonary CTAs. Of these 25 patients, nine were positive for the hyperdense lumen sign in the non-contrast CT images. The hyperdense lumen sign has an over-all sensitivity of 36.0%, specificity of 99.0%, PPV of 90.0%, and NPV of 85.6% (κ=0.449; P-value<0.001). In detecting central thromboembolism, the sensitivity, specificity, PPV, and NPV of this sign were 66.7, 99.1, 88.9, and 96.4%, respectively (κ=0.740; P-value<0.001). The sign was less sensitive in peripheral thromboembolism (κ=0.358; P-value<0.001). The mean (±SD) attenuation difference between the clot and pulmonary blood pool was 22.76 (±4.20) HU (P-value<0.001). The hyperdense lumen sign is a useful indicator of acute pulmonary thromboembolism in non-contrast chest CT scans particularly in cases involving the central pulmonary arteries.