Age-related incidence of pulmonary embolism and additional pathologic findings detected by computed tomography pulmonary angiography

Objective

To compare the incidence of pulmonary embolism (PE) and additional pathologic findings (APF) detected by computed tomography pulmonary angiography (CTPA) according to different age-groups.

Materials and methods

1353 consecutive CTPA cases for suspected PE were retrospectively reviewed. Patients were divided into seven age groups: ≤29, 30–39, 40–49, 50–59, 60–69, 70–79 and ≥80 years. Differences between the groups were tested using Fisher's exact or chi-square test. A p-value < 0.0024 indicated statistical significance when Bonferroni correction was used.

Results

Incidence rates of PE ranged from 11.4% to 25.4% in different age groups. The three main APF were pleural effusion, pneumonia and pulmonary nodules. No significant difference was found between the incidences of PE in different age groups. Furthermore, APF in different age groups revealed no significant differences (all p-values > 0.0024).

Conclusion

The incidences of PE and APF detected by CTPA reveal no significant differences between various age groups.     

Spatial domain image filtering in computed tomography: feasibility study in pulmonary embolism

Our objective was to evaluate the clinical feasibility of spatial domain filtering as an alternative to additional image reconstruction using different kernels in chest CT. Spatial domain filtering generates smooth images from sharp images and thus avoids the need for additional reconstructions when two sets of images are desired. Forty adult patients with clinical suspicion of pulmonary embolism were examined utilizing multi-slice CT (Somatom Volume Zoom, Siemens, Germany). Derived from thin collimated source images (100 mAs, collimation 4×1 mm, rotation time 0.5 s, table speed 7 mm/rotation), two sets of images [effective slice thickness (S_eff) 5 mm, reconstruction increment (RI) 5 mm) were generated using lung (Siemens B50) and soft tissue (Siemens B30) kernels. Additionally, B50 images were filtered in the spatial domain, producing images largely equivalent to B30 images. Firstly, diagnostic accuracy was assessed on spatial domain filtered images regarding central, segmental, and subsegmental pulmonary embolism. In a second step, diagnostic accuracy was assessed for the initially reconstructed B30 images. The results were compared with thin axial slices from the same data set, which were considered as the gold standard in this respect (S_eff 1.25 mm, RI 0.8 mm; B30). Initially reconstructed B30 slices and secondary filtered images were rated for subjective image quality, using a five-point scale (1=excellent, 2=good, 3=moderate, 4=poor, 5=non-diagnostic). Finally, quantitative measurements were assessed using the region of interest (ROI) methodology. In 20 patients pulmonary embolism was proven. Five-millimeter images revealed 10 of 10 central emboli, 18 of 19 segmental thrombi, and 18 of 20 emboli on the subsegmental level. Pulmonary embolism was excluded in 18 of 20 subjects, and in 2 patients a false-positive result was obtained in subsegmental arteries. These findings were concordant for reconstructed and filtered images. Quantitative density measurements provided comparable Hounsfield units in this respect. Subjective gradings of image quality, based on soft tissue settings, were 1.30 (±0.61) for reconstructed slices vs 1.35 (±0.62) for filtered images (weighted kappa coefficient 0.6117; 95% confidence intervals 0.3298–0.8935). Spatial domain filtering has proved to be feasible. Compared with conventional soft tissue reconstructions for central, segmental, and subsegmental pulmonary embolism, no significant difference in the diagnostic value of spatial domain filtered images was found. Online modifications of image sharpness and pixel noise in real time leads to a considerable reduction of processing time and cost saving for storage of CT images. Despite different data processing methods, thin effective slice thicknesses and overlapping reconstruction increments are mandatory for detailed CT analysis of pulmonary embolism on the segmental and subsegmental level. Electronic Publication     

MDCT for suspected pulmonary embolism: multi-institutional survey of 16-MDCT data acquisition protocols

The purpose of this study was to determine the extent to which a consensus exists on multidetector row computed tomography (MDCT) protocol parameters for suspected pulmonary embolism (PE). In August of 2004, a questionnaire addressing a number of body MDCT protocols was mailed to 99 fellows of the Society of Computed Body Tomography, representing a total of 46 institutions. In May 2005, this was followed up with a second mailing. The survey requested details pertaining to protocols for the most advanced MDCT scanner in the department. The overall survey response rate of 37% (17/46) yielded 15 protocols for 16-MDCT imaging of suspected PE. This data was tabulated and revealed a consensus for the use of bolus tracking, rapid contrast infusion, caudo-cranial scanning, the narrowest detector row collimation, and thin (<2 mm) reconstruction sections. However, contrast infusion timing, contrast concentration, and implementation of radiation dose modulation were variable. This compilation of protocols reflects recently published studies advocating the use of narrow acquisition collimation and reconstruction sections for MDCT of suspected PE. Future studies are necessary to elucidate the optimal intravenous contrast infusion parameters and further assess the efficacy of reduced radiation dose protocols.     

Multislice computed tomography perfusion imaging for visualization of acute pulmonary embolism: animal experience

The purpose of our animal study was to evaluate a new computed tomography (CT) subtraction technique for visualization of perfusion defects within the lung parenchyma in subsegmental pulmonary embolism (PE). Seven healthy pigs were entered into a prospective trial. Acute PE was artificially induced by fresh clot material prior to the CT scans. Within a single breath-hold, whole thorax CT scans were performed with a 16-slice multidetector-row CT scanner (SOMATOM Sensation 16; Siemens, Forchheim, Germany) before and after intravenous application of 80 ml of contrast medium with a flow rate of 4 ml/s, followed by a saline chaser. The scan parameters were 120 kV and 100 mAs_eff, using a thin collimation of 16×0.75 mm and a table speed/rotation of 15–18 mm (pitch, 1.25–1.5; rotation time, 0.5 s). Axial source images were reconstructed with an effective slice thickness of 1 mm (overlap, 30%). A new automatic subtraction technique was used. After 3D segmentation of the lungs in the plain and contrast-enhanced series, threshold-based extraction of major airways and vascular structures in the contrast images was performed. This segmentation was repeated in the plain CT images segmenting the same number of vessels and airways as in the contrast images. Both scans were registered onto each other using nonrigid registration. After registration both image sets were filtered in a nonlinear fashion excluding segmented airways and vessels. After subtracting the plain CT data from the contrast data the resulting enhancement images were color-encoded and overlaid onto the contrast-enhanced CT angiography (CTA) images. This color-encoded combined display of parenchymal enhancement of the lungs was evaluated interactively on a workstation (Leonardo, Siemens) in axial, coronal and sagittal plane orientations. Axial contrast-enhanced CTA images were rated first, followed by an analysis of the combination images. Finally, CTA images were reread focusing on areas with perfusion deficits indicating PE on the color-coded enhancement display. Subtraction was feasible for all seven studies. In one animal, opacification of the pulmonary arteries was suboptimal owing to heart insufficiency. In the remaining six pigs, a total of 37 perfusion defects were clearly assessable downstream of occluded subsegmental arteries, showing lower or missing enhancement compared with normally perfused lung parenchyma. Indeterminate findings from CTA showed typical PE perfusion defects in four out of six cases on CT subtraction. Additionally, 22 peripheral triangular-shaped enhancement defects were delineated. Nine of these findings were reclassified as definitely being caused by PE on second reading of the CTA data sets. Our initial results have shown that this new subtraction technique for perfusion imaging of PE is feasible, using routine contrast delivery. Dedicated examination protocols are mandatory for adequate opacification of the pulmonary arteries and for optimization of data sets for subsequent subtraction. Perfusion imaging allows a comprehensive assessment of morphology and function, providing more accurate information on acute PE.This paper contains data on behalf of the Amersham Health Research Fellowship Grant, ECR 2003.     

Suspected pulmonary embolism and deep venous thrombosis: A comprehensive MDCT diagnosis in the acute clinical setting

Both pulmonary arterial and peripheral venous sides of venous thromboembolism (VTE) can now be efficiently and safely investigated by multi-detector CT (MDCT) at the same time by a combined CT angiography/CT venography protocol. In the emergency setting, the use of such a single test for patients suspected of suffering from VTE on a clinical grounds may considerably shorten and simplify diagnostic algorithms. The selection of patients to be submitted to MDCT must follow well-established clinical prediction rules in order to avoid generalized referral to CT on a generic clinical suspicion basis and excessive population exposure to increased ionizing radiation dose, especially in young patients. Clinical and anatomical wide-panoramic capabilities of MDCT allow identification of underlying disease that may explain patients' symptoms in a large number of cases in which VTE is not manifest. The analysis of MDCT additional findings on cardiopulmonary status and total thrombus burden can lead to better prognostic stratification of patients and influence therapeutic options. Some controversial points such as optimal examination parameters, clinical significance of subsegmentary emboli, CT pitfalls and/or possible falsely positive diagnoses, and outcome of untreated patients in which VTE has been excluded by MDCT without additional testing, must of course be taken into careful consideration before the definite role of comprehensive MDCT VTE "one-stop-shop" diagnosis in everyday clinical practice can be ascertained.     

CT lower extremity venography in suspected pulmonary embolism in the ED

The purpose of this study was to evaluate the added benefit of computed tomography lower extremity venography (CTLV)—performed following CT pulmonary angiography (CTPA)—in the emergency department (ED) patient suspected of pulmonary embolism (PE). A retrospective review of 427 consecutive patients having both CTPA and CTLV performed to evaluate patients suspected of PE at two community hospitals was conducted. Three-month follow-up was performed on all patients to ensure that no case of PE or deep venous thrombosis (DVT) was missed. Forty patients were positive for PE, and 11 were positive for DVT. There were 6 CTPA studies read as indeterminate for PE and 11 CTLV studies indeterminate for DVT. Only 1 patient was positive for DVT, who did not have a concurrent PE identified by CTPA. The estimated charges for detecting the single case of isolated DVT was US $206,400. In our ED setting, the additional benefit of adding CTLV to the standard ED work-up of PE was minimal.     

Eighty-peak kilovoltage 16-channel multidetector computed tomography and reduced contrast-medium doses tailored to body weight to diagnose pulmonary embolism in azotaemic patients

The aim of this study was to assess the feasibility of minimising contrast-medium (CM) doses using 80-peak kilovoltage (kVp) 16-channel multidetector computed tomography (MDCT) with CM dose tailored to body weight, when diagnosing pulmonary embolism (PE) in azotaemic patients. Twenty-nine patients (68–93 years; 38–79 kg) with an estimated glomerular filtration rate of 12–49 ml/min underwent 80 kVp MDCT at a median dose of 200 mg iodine (I)/kg and 15 s injection time. Pulmonary artery (PA) enhancement where compared with our own reference material using 320 mg I/kg at 120 kVp and with reported figures in the literature at 120–140 kVp and a 42 g iodine CM dose. Median (1st and 3rd quartiles) values regarding CM dose were 12.2 (9.9–12.8) g iodine; density of left main and lower lobe segmental PA 339 (275–395) Hounsfield units (HU) and 354 (321–442) HU, respectively. Those enhancement values were similar to those obtained from the reference population at 120 kVp and those reported in the literature at 120–140 kVp. One patient had a transient increase in plasma creatinine. Three months’ follow-up revealed deep venous thrombosis among 1/18 patients with negative results from computed tomography (CT). We conclude that 80 kVp 16-channel MDCT to diagnose PE in azotaemic patients may be performed with markedly reduced CM doses, implying a lesser risk for CM-induced nephropathy.     

Logistic regression model for identification of right ventricular dysfunction in patients with acute pulmonary embolism by means of computed tomography

Purpose

Diagnosis of right ventricular dysfunction in patients with acute pulmonary embolism (PE) is known to be associated with increased risk of mortality. The aim of the study was to calculate a logistic regression model for reliable identification of right ventricular dysfunction (RVD) in patients diagnosed with computed tomography pulmonary angiography.

Material and methods

Ninety-seven consecutive patients with acute pulmonary embolism were divided into groups with and without RVD basing upon echocardiographic measurement of pulmonary artery systolic pressure (PASP). PE severity was graded with the pulmonary obstruction score. CT measurements of heart chambers and mediastinal vessels were performed; position of interventricular septum and presence of contrast reflux into the inferior vena cava were also recorded. The logistic regression model was prepared by means of stepwise logistic regression.

Results

Among the used parameters, the final model consisted of pulmonary obstruction score, short axis diameter of right ventricle and diameter of inferior vena cava. The calculated model is characterized by 79% sensitivity and 81% specificity, and its performance was significantly better than single CT-based measurements.

Conclusion

Logistic regression model identifies RVD significantly better, than single CT-based measurements.     

Computer-assisted detection of pulmonary embolism: performance evaluation in consensus with experienced and inexperienced chest radiologists

The value of a computer-aided detection tool (CAD) as second reader in combination with experienced and inexperienced radiologists for the diagnosis of acute pulmonary embolism (PE) was assessed prospectively. Computed tomographic angiography (CTA) scans (64 × 0.6 mm collimation; 61.4 mm/rot table feed) of 56 patients (31 women, 34–89 years, mean = 66 years) with suspected PE were analysed by two experienced (R1, R2) and two inexperienced (R3, R4) radiologists for the presence and distribution of emboli using a five-point confidence rating, and by CAD. Informed consent was obtained from all patients. Results were compared with an independent reference standard. Inter-observer agreement was calculated by kappa, confidence assessed by ROC analysis. A total of 1,116 emboli [within mediastinal (n = 72), lobar (n = 133), segmental (n = 465) and subsegmental arteries (n = 455)] were included. CAD detected 343 emboli (sensitivity = 30.74%, correct-positive rate = 6.13/patient; false-positive rate = 4.1/patient). Inter-observer agreement was good (R1, R2: κ = 0.84, 95% CI = 0.81–0.87; R3, R4: κ = 0.79, 95% CI = 0.76–0.81). Extended inter-observer agreement was higher in mediastinal and lobar than in segmental and subsegmental arteries (κ = 0.84–0.86 and κ = 0.51–0.58 for mediastinal/lobar and segmental/subsegmental arteries, respectively P < 0.05). Agreement between experienced and inexperienced readers was improved by CAD (κ = 0.60–0.62 and κ = 0.69–0.72 before and after CAD consensus, respectively P < 0.05). The experienced outperformed the inexperienced readers (Az = 0.95, 0.93, 0.89 and 0.86 for R1–4, respectively, P < 0.05). CAD significantly improved overall performances of readers 3 and 4 (Az = 0.86 for R3, R4 and Az = 0.89 for R3, R4 with CAD, P < 0.05), by enhancing sensitivities in segmental/subsegmental arteries. CAD improved experienced readers’ sensitivities in segmental/subsegmental arteries (sens. = 0.93 and 0.90 for R1, R2 before and 0.97 and 0.94 for R1, R2 after CAD consensus, P < 0.05), without significant improvement of their overall performances (P > 0.05). Particularly inexperienced readers benefit from consensus with CAD data, greatly improving detection of segmental and subsegmental emboli. This system is advocated as a second reader.     

Pulmonary embolism, right ventricular strain, and intracardiac thrombus-in-transit: Evaluation using comprehensive cardiothoracic computed tomography

A 67-year-old woman presented with symptoms of exertional chest discomfort and dyspnea that had been progressive over the past few days. Her initial evaluation was significant of a mildly elevated troponin-T level and T-wave inversion in leads V₁-V₂ on an electrocardiogram (ECG). Initial suspicion was for acute coronary syndrome. However, a transthoracic echocardiogram showed normal left ventricular systolic function, moderate right ventricular enlargement with moderate decrease in systolic function, possible left atrial mass or thrombus, and a possible right atrial mass or thrombus versus a prominent Chiari network. ECG-gated comprehensive cardiothoracic computed tomography (CT) with a 64-slice multidetector CT was done to assess for pulmonary embolism or acute coronary syndrome and to further evaluate the possible right and left atrial masses. This showed large bilateral pulmonary embolism, interatrial thrombus in transit through a patent foramen ovale, and minimal coronary atherosclerosis. Dynamic imaging showed right ventricular enlargement with severe systolic dysfunction. The patient underwent successful pulmonary thromboembolectomy, removal of intracardiac thrombus, and closure of patent foramen ovale.     

Multidetector computed tomography (MDCT) in the diagnosis of pulmonary embolism: interobserver agreement among radiologists with varied levels of experience

Purpose: To assess the interobserver variability of radiologists with varied levels of experience in the interpretation of multidetector computed tomography (MDCT) pulmonary angiographies.

Material and Methods: Review of CT pulmonary angiographies performed on patients included in a diagnostic study evaluating a decision-based algorithm for diagnosing pulmonary embolism (PE). Five radiologists, three board-certified general radiologists and two radiology trainees with 2 years' experience, participated in the study.

Results: According to the consensus reading, PE was present in 91 (31%) and absent in 194 (67%) patients, while in five patients (1.7%) the interpretations were regarded as equivocal. The per-patient agreement on the diagnosis of PE achieved by each of the four readers compared to the consensus reading was very good (κ range 0.85-0.92), but peripheral emboli were missed in four to six patients by three of four observers. The agreement on the most proximal level of PE (per-proximal level) assessed by mean κ value was 0.83 (κ range 0.68-0.91) for the detection of proximal emboli, 0.61 for segmental emboli (κ range 0.40-0.80), and 0.38 for emboli in the subsegmental vessels (κ range 0.0-0.89).

Conclusion: The overall agreement on the diagnosis of PE by MDCT for general radiologists and radiology trainees is very good, and we therefore believe that the initial management of patients with suspected PE could be based on the preliminary assessment performed by on-call radiologists with 2 years of experience.     

CT venography vs ultrasound in the diagnosis of thromboembolic disease in patients with clinical suspicion of pulmonary embolism

To assess the reliability of indirect computed tomography venography (CTV) in the detection of deep venous thrombosis (DVT) in patients with clinical suspicion of pulmonary embolism (PE). 235 consecutive patients with suspicion of PE underwent an imaging protocol composed of a CT pulmonary angiography (CTPA), a CTV and an ultrasound study of the deep venous system, which was considered the “gold standard.” Sensitivity, specificity, and predictive values were calculated for CTV. ith CTV, 30 (12.8%) cases of DVT were detected, 9 (3.8%) of them without pulmonary embolism in CTPA, increasing the diagnosis of thromboembolic disease in 3.8%. However, six of these nine diagnoses were false positives, and CTV missed six cases of DVT. CTV rendered a sensitivity of 58.8%, specificity of 95.0%, a positive predictive value of 66.7%, and a negative predictive value of 93.2%. In patients with clinical suspicion of pulmonary embolism, ultrasound is preferred to CTV for the detection of DVT.     

Multi-detector row computed tomography: imaging in acute aortic syndrome

Acute aortic syndromes (AAS) encompass a spectrum of emergencies. These include those non-traumatic disease entities of the aorta namely, penetrating atherosclerotic ulcer, intramural haematoma, dissection and aneurysm rupture. The various types of AAS cannot be reliably differentiated on clinical grounds alone. Acute thoracic aortic injury is usually included in this group even though clinical presentation is different, i.e., in the context of trauma, the imaging features are very similar. Differentiation of AAS from acute coronary syndrome (ACS) is important, however, it must be remembered that ACS may occur as a result of AAS. Now electrocardiogram (ECG)-gating technology is widely available, ECG-gated multi-detector row computed tomography (MDCT) is a powerful clinical tool in the acute emergency setting, which enables rapid and specific diagnosis of aortic pathology. ECG-gated MDCT significantly reduces motion artefact, avoids potential pitfalls in diagnosis and often provides diagnostic information about the coronary arteries. It should be used as a first-line imaging technique. This article examines the role of MDCT imaging and cardiac gating in the assessment of AAS and discusses the differentiation of this spectrum of aortic diseases with reference to the key imaging findings as obtained by experience in our institution.     

Helical CTPA in the investigation of pulmonary embolism: a 6-year review

AIM: To assess the change in practice and resulting diagnostic outcome in the radiological investigation of pulmonary embolism (PE) since the introduction of helical CTPA in a large teaching hospital. MATERIALS AND METHODS: A retrospective review was undertaken of all radiological investigations performed over a 6-year period before and after the introduction of CTPA (protocols 1 and 2, respectively) as an integral part of the imaging protocol in the investigation of clinically suspected PE. The total numbers and results of all investigations are assessed for each protocol. RESULTS: A substantial increase in both the total number of patients and the number of investigations performed for the investigation of PE since the introduction of CTPA occurred. Five hundred and twenty-six patients underwent 617 investigations in 1995-1996, and 760 patients underwent 805 investigations in 2001-2002. There was a significant decrease in the number of investigations per patient, 1.17 in 1995-1996 versus 1.06 in 2001-2002. Primary investigation showed a significant decrease in indeterminate examinations from 25.7 to 8.5% and an increase in positive results for PE from 18 to 24%. CONCLUSION: In the study population there was a significant increase in the number of patients being investigated for PE, with a decrease in both the number of non-diagnostic investigations and the total investigations per patient since the introduction of helical CTPA. This is probably due to the ready availability of a new imaging technique and physicians awareness that CTPA has significantly improved specificity, which encourages the referral of patients for investigation.     

Magnetic resonance imaging of acute pulmonary embolism

Pulmonary embolism (PE) is a very common and potentially life-threatening disease. In comparison with CT, the clinical relevance of magnetic resonance imaging (MRI) for the assessment of PE is low. Nevertheless, as there are some potential advantages of MRI over CT (e.g. radiation free method, better safety profile of MR contrast media, capability of functional imaging). In certain patient, groups MRI might therefore be considered as a valuable alternative in the assessment of suspected PE. This article reviews the relevant MRI techniques for the evaluation of PE and gives an overview of the current literature for contrast-enhanced MR angiography of PE.     

Role of multidetector computed tomography (MDCT) in diagnosis of subhepatic appendicitis

Background

Acute appendicitis is a common surgical condition that is usually managed with early surgery, and is associated with low morbidity and mortality. However, some patients may have atypical symptoms and physical findings that may lead to a delay in diagnosis and increased complications.Ascending subhepatic appendicitis presenting with right upper abdominal pain may be clinically indistinguishable from acute pathology in the gallbladder, liver, biliary tree, right kidney and right urinary tract.

Aim of the work

To study the role of multidetector computed tomography in diagnosis of subhepatic appendicitis.

Subjects & methods

In the current study, we included fifteen patients diagnosed radiologically and confirmed surgically as subhepatic appendicitis.Ultrasonography followed by multidetector computed tomographic examination were performed to all patients before surgery.

Results

The clinical diagnosis of the patients included in this study at presentation was acute cholecystitis in four patients, pyelonephritis in three, and ureteric colic in three. Five patients were referred with uncertain diagnosis.The presence of subhepatic appendicitis was confirmed sonographically only in two patients. Computed tomography (CT) identified correctly subhepatic appendicitis in all cases.

Conclusion

Our study indicates the usefulness of multidetector CT in diagnosing atypical ascending subhepatic appendicitis.     

Blueprint of the certification examination in cardiovascular computed tomography

Physician certification is critical in all areas of cardiovascular imaging to assure optimal performance and interpretation of quality studies for patient diagnosis and management. This is especially important in the field of cardiovascular computed tomography where practitioners have varied training and expertise that may not cover the full range of skills in the technical, image interpretative and clinical application of the results for patient management. The Certification Board of Cardiovascular Computed Tomography was developed to test the minimal level of competence of physicians performing cardiovascular computed tomography. In this article, the process of defining the content areas, determining candidate eligibility and the process of examination development and testing will be defined.     

Infectious mediastinitis after cardiovascular surgery: role of computed tomography

PURPOSE: The aim of this study was to evaluate the effectiveness of computed tomography (CT) findings in the diagnosis of mediastinitis after cardiovascular surgery with median sternotomy. MATERIAL AND METHODS: A total of 122 patients were divided into two groups: the early group (21 days after surgery). Among them, six patients were ultimately diagnosed with infectious mediastinitis. CT findings in each patient were evaluated. Mediastinal fluid collections or free gas bubbles were regarded as the primary findings of mediastinitis. RESULTS: In the early group, sensitivity and specificity of the primary CT findings were 100% and 39%, respectively. In the late group, the sensitivity was 100% and the specificity 85%. Mediastinal fluid collections were observed in all six patients with mediastinitis. CONCLUSION: Mediastinal fluid collections or free gas bubbles are not specific during the early postoperative period. However, after 2 21 days, these observations could be indicative of mediastinitis.     

Multidetector computed tomography (MDCT) evaluation of myocardial viability: intraindividual comparison of monomeric vs. dimeric contrast media in a rabbit model

To evaluate the influence of different types of iodinated contrast media on the assessment of myocardial viability, acute myocardial infarction (MI) was surgically induced in six rabbits. Over a period of 45 min, contrast-enhanced cardiac MDCT (64 × 0.6 mm, 80 kV, 680mAs_eff.) was repeatedly performed using a contrast medium dose of 600 mg iodine/kg body weight. Animals received randomized iopromide 300 and iodixanol 320, respectively. Attenuation values of healthy and infarcted myocardium were measured. The size of MI was computed and compared with nitroblue tetrazolium (NBT)-stained specimen. The highest attenuation differences between infarcted and healthy myocardium occurred during the arterial phase with 140.0 ± 3.5 HU and 141.0 ± 2.2 HU for iopromide and iodixanol, respectively. For iodixanol the highest attenuation difference on delayed contrast-enhanced images was achieved 3 min post injection (73.5 HU). A slightly higher attenuation difference was observed for iopromide 6 min after contrast medium injection (82.2 HU), although not statistically significant (p = 0.6437). Mean infarct volume as measured by NBT staining was 33.5% ± 13.6%. There was an excellent agreement of infarct sizes among NBT-, iopromide- and iodixanol-enhanced MDCT with concordance-correlation coefficients ranging from ρ_{(c)  =} 0.9928–0.9982. Iopromide and iodixanol both allow a reliable assessment of MI with delayed contrast-enhanced MDCT.     

Severity assessment of acute pulmonary embolism: evaluation using helical CT

The objective was to evaluate the helical CT (HCT) criteria that could indicate severe pulmonary embolism (PE). In a retrospective study, 81 patients (mean age 62 years) with clinical suspicion of PE explored by HCT were studied. The patients were separated into three different groups according to clinical severity and treatment decisions: group SPE included patients with severe PE based on clinical data who were treated by fibrinolysis or embolectomy (n=20); group NSPE included patients with non-severe PE who received heparin (n=30); and group WPE included patients without PE (n=31). For each patient we calculated a vascular obstruction index based on the site of obstruction and the degree of occlusion in the pulmonary artery. We noted the HCT signs, i.e., cardiac and pulmonary artery dimensions, that could indicate acute cor pulmonale. According to multivariate analysis, factors significantly correlated with the severity of PE were: the vascular obstruction index (group SPE: 54%; group NSPE: 24%; p<0.001); the maximum minor axis of the left ventricle (group SPE: 30.2 mm; group NSPE: 40.4 mm; p<0.001); the diameter of the central pulmonary artery (group SPE: 32.4 mm; group NSPE: 28.3 mm; p<0.001); the maximum minor axis of the right ventricle (group SPE: 47.5 mm; group NSPE: 42.7 mm; p=0.029); the right ventricle/left ventricle minor axis ratio (group SPE: 1.63; group NSPE: 1.09; p<0.0001). Our data suggest that hemodynamic severity of PE can be assessed on HCT scans by measuring four main criteria: the vascular obstruction index; the minimum diameter of the left ventricle; the RV:LV ratio; and the diameter of the central pulmonary artery.