Comparison of contrast-enhanced ct angiography and gadolinium-enhanced MR angiography in the detection of subsegmental-sized pulmonary embolism. An experimental study in a pig model

Purpose: 
To compare contrast-enhanced CT angiography (CTA) and gadolinium-enhanced MR angiography (MRA) for the detection of subsegmental-sized pulmonary emboli in a pig model. Material and Methods: 
In 5 anesthetized pigs, 3-mm diameter embolic materials made of Konjac, a semisolid food, were introduced through the internal jugular vein into pulmonary arteries. After embolization, CTA and MRA images were obtained. Respiration was suspended during CTA and MRA image acquisition. Two readers reviewed the CTA and MRA images to detect emboli. The pigs were sacrificed, and sliced specimens of inflated lung served as the gold standard. Results: 
Thirty-six emboli were detected within peripheral arteries. The sensitivity (and 95% confidence intervals) of CTA for the two readers were 57% (39-74%) and 66% (48-81%), and 88% (69-98%) and 92% (74-94%) for MRA. The specificity of CTA was 95% (91-97%) and 98% (96-99%), and that of MRA was 85% (74-93%) and 90% (80-96%). Interobserver agreement was higher for MRA (kappa 0.898) than CTA (kappa 0.574). Conclusion: 
For the detection of subsegmental pulmonary emboli, MRA was superior to CTA, with a higher sensitivity and interobserver agreement by demonstrating perfusion deficits.     

Pulmonary embolism: comparison of gadolinium-enhanced MR angiography with contrast-enhanced spiral CT in a porcine model

RATIONALE AND OBJECTIVES: The purpose of this study was to compare gadolinium-enhanced magnetic resonance (MR) angiography with contrast material-enhanced computed tomography (CT) for the detection of small (4-5-mm) pulmonary emboli (PE), with a methacrylate cast of the porcine pulmonary vasculature used as the diagnostic standard. MATERIALS AND METHODS: In 15 anesthetized juvenile pigs, colored methacrylate beads (5.2 and 3.8 mm diameter-the size of segmental and subsegmental emboli in humans) were injected via the left external jugular vein. After embolization, MR angiographic and CT images were obtained. The pigs were killed, and the pulmonary arterial tree was cast in clear methacrylate, allowing direct visualization of emboli. Three readers reviewed CT and MR angiographic images independently and in random order. RESULTS: Forty-nine separate embolic sites were included in the statistical analysis. The mean sensitivity (and 95% confidence intervals) for CT and MR angiography, respectively, were 76% (68%-82%) and 82% (75%-88%) (P > .05); the mean positive predictive values, 92% (85%-96%) and 94% (88%-97%) (P > .05). In this porcine model, PE were usually seen as parenchymal perfusion defects (98%) with MR angiography and as occlusive emboli (100%) with CT. CONCLUSION: MR angiography is as sensitive as CT for the detection of small PE in a porcine model.     

Sensitivity and specificity of perfusion scintigraphy combined with chest radiography for acute pulmonary embolism in PIOPED II

We used the archived Prospective Investigation of Pulmonary Embolism Diagnosis II (PIOPED II) data and images to test the hypothesis that reading perfusion scans with chest radiographs but without ventilation scans, and categorizing the perfusion scan as "pulmonary embolism (PE) present" or "PE absent," can result in clinically useful sensitivity and specificity in most patients. METHODS: Patients recruited into PIOPED II were eligible for the present study if they had a CT angiography (CTA) or digital subtraction angiography (DSA) diagnosis, an interpretable perfusion scan and chest radiographs, and a Wells' score. Four readers reinterpreted the perfusion scans and chest radiographs of eligible patients. Two readers used the modified PIOPED II criteria and 2 used the Prospective Investigative Study of Pulmonary Embolism Diagnosis (PISAPED) criteria. The chest radiographs were read as "normal/near normal," "abnormal," or "nondiagnostic," and the perfusion scans were read as "PE present," "PE absent," or "nondiagnostic." The primary analysis used a composite reference standard: the PIOPED II DSA result or, if there was no definitive DSA result, CTA results that were concordant with the Wells' score as defined in PIOPED II (CTA positive and Wells' score > 2, or CTA negative and Wells' score < 6). RESULTS: The prevalence of PE in the sample was 169 of 889 (19%). Using the modified PIOPED II criteria, the sensitivity of a "PE present" perfusion scan was 84.9% (95% confidence interval [CI], 80.1%-88.8%), and the specificity of "PE absent" was 92.7% (95% CI, 91.1%-94.1%), excluding "nondiagnostic" results, which occurred in 20.6% (95% CI, 18.8%-22.5%). Using PISAPED criteria, the sensitivity of a "PE present" perfusion scan was 80.4% (95% CI, 75.9%-84.3%) and the specificity of "PE absent" was 96.6% (95% CI, 95.5%-97.4%), whereas the proportion of patients with "nondiagnostic" scans was 0% (95% CI, 0.0%-0.2%). CONCLUSION: Perfusion scintigraphy combined with chest radiography can provide diagnostic accuracy similar to both CTA and ventilation-perfusion scintigraphy, at lower cost and with lower radiation dose. With modified PIOPED II criteria, a higher proportion of scans were nondiagnostic than with CTA, and with PISAPED criteria none were nondiagnostic.     

Evaluation of carotid artery stenosis with multisection CT and MR imaging: influence of imaging modality and postprocessing

BACKGROUND AND PURPOSE: We prospectively evaluated the influence of different imaging techniques (time-of-flight MR angiography [TOF-MRA], contrast-enhanced MR angiography [CE-MRA], multisection CT angiography [CTA]) and postprocessing methods (maximum intensity projection [MIP], multiplanar reformation [MPR]) on carotid artery stenosis grading. MATERIALS AND METHODS: Fifty patients (34 men, 16 women) with symptomatic stenosis of the internal carotid artery were examined with a 16-section spiral CT and a 1.5T MR unit. Two MRA techniques were applied: 3D-TOF and CE-MRA. MPR was used for postprocessing with all modalities; MIP was used only with MRA. Four readers measured and calculated the percentage diameter stenosis independently according to NASCET criteria. The Wilcoxon test was used to measure interobserver variability, and the Friedman test was used to test the null-hypothesis of equality of the modalities. RESULTS: The hypothesis for global equality was rejected (P < .001). TOF-MRA and CTA assessed with MPR showed the highest concordance (difference, 0.6%; confidence interval [CI], -3.0, 4.3%), and CE-MRA with MIP and CTA showed the lowest concordance in stenosis grading (difference, 7.0%; CI, 3.4, 10.6%). MPR resulted in lower degrees of stenosis than MIP for both MRA sequences, although not statistically significant (CE, -3.0%; CI, -6.6, 0.6%; TOF, -2.2%; CI, -5.8, 1.4%). When only studies with good or excellent image quality were considered, the differences decreased, but the trends remained. CONCLUSION: Stenosis grading is dependent on the examination method and postprocessing technique. CTA and TOF-MRA evaluated with MPR revealed highest concordance.     

Downstream Imaging Utilization After MR Angiography Versus CT Angiography for the Initial Evaluation of Pulmonary Embolism

ObjectiveTo compare the proportion of emergency department (ED) patients who undergo subsequent chest CT or MR within 1 year of an initially negative scan for pulmonary embolism (PE).MethodsThis single-center, retrospective, observational study examined the use of chest CT or MR for ED patients with MR angiography (MRA) negative for PE during April 2008 to March 2013. We compared the 1-year scan utilization for these cases to an age- and sex-matched cohort of patients who underwent CT angiography (CTA). We also calculated time to first follow-up scan and mean radiation dose in each arm. Trained data abstractors used a standardized protocol and electronic case report form to gather all outcomes of interest. Results are reported as means or proportions with their associated confidence intervals (CIs).ResultsIn all, 717 ED patients (430 MRAs and 287 CTAs) were included. At 1 year, the proportion undergoing subsequent imaging (MRA 16.7%, CTA 15.3%; difference = 1.4%, 95% CI 4.05%-6.86%) and time to first follow-up scan (difference = 13 days, 95% CI −22.69-48.7) did not differ between arms. Mean radiation dose per patient at 1 year was significantly higher in the CTA arm (9.82 mSv; 95% CI 9.12-10.53) compared with 2.92 mSv (95% CI 1.86-3.98) with MRA. Those with an index MRA were more likely to undergo subsequent MRAs (odds ratio 3.68; 95% CI 1.22-11.12) than those with an index CTA. However, in both arms, the majority (85%) of subsequent scans were CTAs.ConclusionsWhen comparing patients initially undergoing MRA versus CTA for the evaluation of PE, there was no difference in downstream chest CT or MR use at 1 year.     

Intraindividual comparison of gadolinium- and iodine-enhanced 64-slice multidetector CT pulmonary angiography for the detection of pulmonary embolism in a porcine model

This study is an evaluation of the diagnostic accuracy of gadolinium-enhanced computed tomography pulmonary angiography (CTPA) for the detection of pulmonary embolism (PE) in comparison with iodine-enhanced CTPA. PE was induced in five anesthetized pigs by administration of blood clots through an 11-F catheter inside the jugular vein. Animals underwent CTPA in breathhold with i.v. bolus injection of 50 ml gadopentetate dimeglumine (0.4 mmol/kg, 4 ml/s). Subsequently, CTPA was performed using the same imaging parameters but under administration of 70 ml nonionic iodinated contrast material (400 mg/ml, 4 ml/s). All images were reconstructed with 1 mm slice thickness. A consensus readout of the iodium-enhanced CTPAs by both radiologists served as reference standard. Gadolinium-enhanced CTPAs were evaluated independently by two experienced radiologists, and differences in detection rate between both contrast agents were assessed on a per embolus basis using the Wilcoxon signed-rank test. Interobserver agreement was determined by calculation of қ values. PE was diagnosed independently by both readers in all five pigs by the use of gadolinium-enhanced CTPA. Out of 60 pulmonary emboli detected in the iodine-enhanced scans, 47 (78.3%; reader 1) and 44 (62.8%; reader 2) emboli were detected by the use of gadolinium. All 13 (100%) emboli in lobar arteries (by both readers) and 26 (reader 1) and 25 (reader 2) out of 27 emboli (96.3% and 92.6%) in segmental arteries were detected by the use of the gadolinium-enhanced CTPA. In subsegmental arteries, only 8 (40%; reader 1) and 6 (30%; reader 2) out of 20 emboli were detected by the gadolinium-enhanced CTPA. By comparing both scans on a per vessel basis (Wilcoxon test), Gd-enhanced CTPA was significantly inferior in emboli detection on subsegmental level (P < 0.0001). The interobserver agreement was excellent on lobar and segmental level (қ = 1.0 and 0.93, respectively), whereas readers only reached moderate agreement for PE evaluation on subsegmental level (қ = 0.56). Compared to conventional CTPA with iodinated contrast media, gadolinium-based contrast agents achieve an equivalent diagnostic accuracy in detection of PE down to segmental level. Gadolinium-enhanced CTPA may be considered as an alternative for the diagnostic workup of acute pulmonary embolism in patients with contraindications to iodinated contrast agents.     

Intracranial vascular stenosis and occlusive disease: evaluation with CT angiography, MR angiography, and digital subtraction angiography

BACKGROUND AND PURPOSE: Although digital subtraction angiography (DSA) provides excellent visualization of the intracranial vasculature, it has several limitations. Our purpose was to evaluate the ability of helical CT angiography (CTA) to help detect and quantify intracranial stenosis and occlusion compared with DSA and MR angiography (MRA). METHODS: Twenty-eight patients underwent CTA, DSA, and 3D time-of-flight (TOF) MRA for suspected cerebrovascular lesions. All three studies were performed within a 30-day period. Two readers blinded to prior estimated or calculated stenoses, patient history and clinical information examined 672 vessel segments. Lesions were categorized as normal (0-9%), mild (10-29%), moderate (30-69%), severe (70-99%), or occluded (no flow detected). DSA was the reference standard. Unblinded consensus readings were obtained for all discrepancies. RESULTS: A total of 115 diseased vessel segments were identified. After consensus interpretation, CTA revealed higher sensitivity than that of MRA for intracranial stenosis (98% versus 70%, P < .001) and occlusion (100% versus 87%, P = .02). CTA had a higher positive predictive value than that of MRA for both stenosis (93% versus 65%, P < .001) and occlusion (100% versus 59%, P < .001). CTA had a high interoperator reliability. In 6 of 28 patients (21%), all 6 with low-flow states in the posterior circulation, CTA was superior to DSA in detection of vessel patency. CONCLUSION: CTA has a higher sensitivity and positive predictive value than MRA and is recommended over TOF MRA for detection of intracranial stenosis and occlusion. CTA has a high interoperator reliability. CTA is superior to DSA in the evaluation of posterior circulation steno-occlusive disease when slow flow is present. CTA results had a significant effect on patient clinical management.     

Gadolinium-enhanced MR angiography of visceral arteries in patients with suspected chronic mesenteric ischemia

The purpose of this study was to evaluate accuracy of dynamic gadolinium-enhanced MR angiography (MRA) of the celiac, superior, and inferior mesenteric arteries in patients with suspected mesenteric ischemia compared with catheter angiography or surgery. Sixty-five patients with suspected mesenteric ischemia underwent three-dimensional spoiled gradient-recalled acquisition in the steady state (GRASS) gadolinium-enhanced MRA. Correlative studies were performed on 14 patients, catheter angiography alone was performed on 12 patients, and surgery alone was performed on two patients. Six patients had mesenteric ischemia. In all patients, the celiac artery (CA) and superior mesenteric artery (SMA) were seen well enough to evaluate; however, the inferior mesenteric artery (IMA) could be evaluated in only 9 of the 14 patients. MRA showed severe stenosis (>75%) or occlusion of the celiac axis in seven patients, of the SMA in six patients, and of the IMA in four patients. The overall sensitivity and specificity were 100% and 95%, respectively, compared with catheter angiography and surgery. The two errors were caused by overgrading the severity of IMA disease. Three-dimensional gadolinium-enhanced MRA can accurately demonstrate the origins of the CA and SMA and is useful in evaluation of patients with suspected mesenteric ischemia.     

Gadolinium-enhanced 3D MR angiography of renal artery stenosis: a pilot comparison of maximum intensity projection, multiplanar reformatting, and 3D volume-rendering postprocessing algorithms

RATIONALE AND OBJECTIVES: The authors compared diagnostic accuracy of maximum intensity projection (MIP), multiplanar reformatting (MPR), and three-dimensional (3D) volume rendering (VR) in the evaluation of gadolinium-enhanced 3D magnetic resonance (MR) angiography of the renal arteries. They hypothesized that VR is as accurate as or more accurate than MIP and MPR at depicting renal artery stenosis. MATERIALS AND METHODS: The study group comprised 28 consecutive patients who underwent gadolinium-enhanced 3D MR angiography of the renal arteries. Studies were postprocessed to display images in MIP, MPR, and VR formats. Digital subtraction angiography (DSA), when performed (nine of 28 patients), was the standard for comparison. For each main renal artery, an estimate of percentage stenosis was made for any stenoses detected by three independent radiologists. For calculation of sensitivity, specificity, and accuracy, MR angiographic stenosis estimates were categorized as mild (0%-39%), moderate (40%-69%), or severe (> or = 70%). DSA stenosis estimates of 70% or greater were considered hemodynamically significant. RESULTS: Analysis of variance demonstrated MIP estimates of stenosis were statistically greater than VR estimates in two readers and greater than MPR estimates in all readers for all patients. MIP images also showed the largest mean difference from DSA stenosis estimates for all three readers. For both VR and MPR, mean differences between MR angiographic stenoses estimates and DSA estimates reached significance for only one reader, whereas, for MIP versus DSA, mean differences reached significance for all three readers. Although not statistically significant compared with DSA, accuracies of VR (87%) and MPR (89%) were greater than that of MIP (81%). CONCLUSION: In this pilot study, MIP was the least accurate of the three image display algorithms tested. VR and MPR yielded similar values for each method of comparison.     

The non-invasive detection of intracranial aneurysms: are neuroradiologists any better than other observers?

Can non-neuroradiologists detect intracranial aneurysms as well as neuroradiologists, using CT and MR angiography? Sixty patients undergoing intra-arterial digital subtraction angiography (IADSA) to detect aneurysms also underwent computed tomographic angiography (CTA) and time-of-flight magnetic resonance angiography (MRA). Consensus review of IADSA by two neuroradiologists was the reference standard. Two neuroradiologists, a neurosurgeon, a neuroradiographer and a general radiologist blinded to IADSA, plain CT and clinical data, independently reviewed hard-copy base and reconstructed maximum intensity projection images of the CTA and MRA studies. Thirty patients had a total of 63 aneurysms, 71.4% were 相似文献   

Multidetector spiral CT renal angiography in the diagnosis of renal artery fibromuscular dysplasia

OBJECTIVE: The aim of this study was to evaluate the role and detection rate of multidetector spiral CT renal angiography (CTA) as compared with conventional angiography (CA), the commonly accepted gold standard, in the diagnosis of renal artery fibromuscular dysplasia (FMD). In addition, the role of CTA reconstructions (multiplanar reformatted images (MPR), maximum intensity projections (MIP) and shaded-surface display (SSD)) in the detection of FMD was also evaluated. MATERIALS AND METHODS: CTA results were retrospectively reviewed in 21 hypertensive patients with CA-proven FMD. Clinical indications for referral included resistant hypertension (requiring greater than three antihypertensive medications), labile hypertension, hypertension in combination with renal impairment and the presence of abdominal bruits in the context of systemic hypertension. In some cases, these clinical indications were supplemented by positive results in other tests, including plasma renin assay, captopril scintigraphy and/or Doppler ultrasound. The findings of CA in these 21 patients were compared to CTA. RESULTS: Mean patient age was 62.33+14.32 years (range 24-85 years). CTA identified all 42 main renal arteries (100%) and all 10 accessory renal arteries (100%) visualized on CA. In the diagnosis of FMD, CTA detected all 40 (100%) lesions detected by CA. No single CTA reconstruction technique was able to detect all lesions noted on corresponding CA, however, upon review of all CTA reconstructions (MPR, MIP and SSD) in each case, every lesion was correctly identified by CTA. CONCLUSION: Our experience suggests that CTA is a non-invasive, reliable and accurate method for the diagnosis of renal artery fibromuscular dysplasia. Moreover, in our experience CTA has many advantages as a diagnostic screening tool over CA, including accessibility, speed, lower complication profile, versatility and cost-effectiveness. CTA shows great potential as a guiding tool for directing subsequent procedures such as CA+balloon angioplasty.     

Intracranial stenoocclusive disease: double-detector helical CT angiography versus digital subtraction angiography.

BACKGROUND AND PURPOSE: To our knowledge, no large-scale studies comparing the accuracy of CT angiography (CTA) to intraarterial digital subtraction angiography (DSA) of intracranial stenosis have been reported. We attempted to determine the diagnostic value of intracranial CT angiography (CTA) of normal vasculature and variants as well as of stenoocclusive disease. METHODS: One-hundred and twelve patients underwent CTA and intraarterial angiography, and 2205 vascular segments were examined to ascertain presence, visibility, and degree of arterial stenoses (n = 105) as well as anatomic variants. Source, maximum intensity projection (MIP), and MIP-generated multiplanar reformatted (MPR) images were evaluated. RESULTS: All 55 anatomic variants were identified correctly. Visibility of small-vessel segments was increased from 75% to 83% by using source images. MPR was helpful in differentiating distal vertebral hypoplasia from stenosis and in overcoming artifacts. All 43 occlusive segments were graded correctly (sensitivity = 100%, predictive value = 93.4%) as follows: severely stenotic ([n = 23], sensitivity = 78%, predictive value = 81.8%); moderately stenotic ([n = 36], sensitivity = 61%, predictive value = 84.6%); and mildly stenotic ([n = 3], sensitivity = 66%, predictive value = 28%). Normal segments (n = 2100) had a sensitivity of 99.5%, and CTA evinced a specificity of 99% for detecting stenoocclusive disease. Approximately one-third of wrong assessments were related to the petrous segment of the carotid artery. CONCLUSION: CTA with double-detector technology and advanced postprocessing algorithms, including MPR, is about as reliable as MRA in depicting the vasculature of the anterior and posterior circulation and in grading intracranial stenoocclusive lesions, with the exception of the petrous segment of the carotid artery. CTA might be superior to MRA in the evaluation of poststenotic low-flow segments.     

16层螺旋CT肺血管造影在肺动脉栓塞诊断中的应用

目的　研究 16层螺旋CT肺血管造影在肺动脉栓塞诊断中的应用价值。方法　使用 16层螺旋CT扫描机 (SiemensSensation 16 )对临床拟诊肺栓塞的 4 9例患者进行前瞻性研究。采用层厚 3mm行胸部增强扫描。利用原始数据行层厚 1mm的轴面及多平面重建 (MPR)。比较层厚 3mm、1mm的轴面图像及MPR图像。结果　CT诊断肺栓塞 4 2例。病变共累及肺动脉 35 2支。对于主肺动脉及肺叶动脉栓塞 ,三种图像检出结果一致。但对于肺段及亚段动脉栓塞 ,层厚 1mm较 3mm显示率高 ,差异有显著意义 (P <0 0 1) ,1mm的MPR较轴面图像显示率高 ,但差异无显著性意义 (P >0 0 5 )。结论　 16层螺旋CT肺血管造影无创、快速、敏感性高 ,应当作为肺栓塞的首选检查方法。     

Non-invasive assessment of epiaortic vessels. Comparison of magnetic resonance angiography with gadolinium, spiral computerized tomography angiography, and digital angiography

PURPOSE: The aim of the study was to compare gadolinium-enhanced MRA (Gd-MRA), Computed Tomography angiography (CTA) and digital subtraction angiography (DSA) in the evaluation of carotid stenosis. MATERIAL AND METHODS: Thirty patients with US-proven internal carotid artery stenosis over 50%, underwent Gd-MRA, CTA and DSA. Gd-MRA was acquired using the keyhole technique. RESULTS: The overall agreement was 90% for Gd-MRA and 93% for CTA. Gd-MRA and CTA overestimated 5 and 4 cases of mild stenosis and 1 case each of moderate stenosis, respectively. Gd-MRA better delineated ulcerated plaques, tandem lesions and pseudo-occlusions. DISCUSSION AND CONCLUSIONS: Because of the high speed acquisition breath-hold is no longer necessary for Gd-MRA and more delayed phases were analysed when necessary. The main limitation of Gd-MRA was represented by insufficient volume coverage that allowed the visualisation of supraaortic vessels from the arch only in 57% of the cases. Calcified plaques were very well detected by CTA and not by Gd-MRA. In our experience Gd-MRA represents the second step non invasive tool in patients with US-proven carotid stenosis. This leads to avoid conventional angiography in most cases.     

MR angiography with parallel acquisition for assessment of the visceral arteries: comparison with conventional MR angiography and 64-detector-row computed tomography

The purpose of the study was to retrospectively compare three-dimensional gadolinium-enhanced magnetic resonance angiography (conventional MRA) with MRA accelerated by a parallel acquisition technique (fast MRA) for the assessment of visceral arteries, using 64-detector-row computed tomography angiography (MDCTA) as the reference standard. Eighteen patients underwent fast MRA (imaging time 17 s), conventional MRA (29 s) and MDCTA of the abdomen and pelvis. Two independent readers assessed subjective image quality and the presence of arterial stenosis. Data were analysed on per-patient and per-segment bases. Fast MRA yielded better subjective image quality in all segments compared with conventional MRA (P = 0.012 for reader 1, P = 0.055 for reader 2) because of fewer motion-induced artefacts. Sensitivity and specificity of fast MRA for the detection of arterial stenosis were 100% for both readers. Sensitivity of conventional MRA was 89% for both readers, and specificity was 100% (reader 1) and 99% (reader 2). Differences in sensitivity between the two types of MRA were not significant for either reader. Interobserver agreement for the detection of arterial stenosis was excellent for fast (κ = 1.00) and good for conventional MRA (κ = 0.76). Thus, subjective image quality of visceral arteries remains good on fast MRA compared with conventional MRA, and the two techniques do not differ substantially in the grading of arterial stenosis, despite the markedly reduced acquisition time of fast MRA.     

Pulmonary MRA: Differentiation of pulmonary embolism from truncation artefact

Purpose

Truncation artefact (Gibbs ringing) causes central signal drop within vessels in pulmonary magnetic resonance angiography (MRA) that can be mistaken for emboli, reducing diagnostic accuracy for pulmonary embolism (PE). We propose a quantitative approach to differentiate truncation artefact from PE.

Methods

Twenty-eight patients who underwent pulmonary computed tomography angiography (CTA) for suspected PE were recruited for pulmonary MRA. Signal intensity drops within pulmonary arteries that persisted on both arterial-phase and delayed-phase MRA were identified. The percent signal loss between the vessel lumen and central drop was measured. CTA served as the reference standard for presence of pulmonary emboli.

Results

A total of 65 signal intensity drops were identified on MRA. Of these, 48 (74 %) were artefacts and 17 (26 %) were PE, as confirmed by CTA. Truncation artefacts had a significantly lower median signal drop than PE on both arterial-phase (26 % [range 12–58 %] vs. 85 % [range 53–91 %]) and delayed-phase MRA (26 % [range 11–55 %] vs. 77 % [range 47–89 %]), p?<?0.0001 for both. Receiver operating characteristic (ROC) analyses revealed a threshold value of 51 % (arterial phase) and 47 % signal drop (delayed phase) to differentiate between truncation artefact and PE with 100 % sensitivity and greater than 90 % specificity.

Conclusion

Quantitative signal drop is an objective tool to help differentiate truncation artefact and pulmonary embolism in pulmonary MRA.

Key points

? Inexperienced readers may mistake truncation artefacts for emboli on pulmonary MRA ? Pulmonary emboli have non-uniform signal drop ? 51 % (arterial phase) and 47 % (delayed phase) cut-off differentiates truncation artefact from PE ? Quantitative signal drop measurement enables more accurate pulmonary embolism diagnosis with MRA     

CT angiography in the assessment of carotid artery atherosclerosis

Objective: The aim of the study was to evaluate the ability of CT angiography (CTA) to detect atherosclerosis of the carotid arteries in comparison with 3D time-of-flight MR angiography (3D TOF MRA), using contrast angiography and intravascular ultrasound (IVUS) as a reference.Material and Methods: Contrast angiography and CTA were performed in 31 patients (mean age 65 years, range 45-79). The image quality was evaluated, atherosclerotic lesions were registered, and diameter stenosis degree was visually estimated from axial source images of CTA and 3D TOF MRA (21 patients), and results of interpretations were compared. The comparison of quantitative measurements was performed using IVUS as a reference.Results: Contrast angiography detected 51 lesions (mean diameter stenosis 50%, range 10-100%), and CTA detected all same lesions. CTA provided better image quality and consistency of image interpretation than 3D TOF MRA. IVUS verified 29 atherosclerotic lesions with a mean diameter stenosis of 35%, (range 4-40%). CTA yielded a sensitivity of 96% to 100% (≤10% or ≤20% diameter stenosis regarded as normal) for the detection of lesions with reference to IVUS.Conclusion: CTA seems feasible and accurate for the detection of atherosclerosis in carotid arteries.     

Gadolinium-enhanced pulmonary magnetic resonance angiography in the diagnosis of acute pulmonary embolism: a prospective study on 48 patients

OBJECTIVE: Gadolinium-enhanced pulmonary magnetic resonance angiography (MRA) can be an option in patients with a history of previous adverse reaction to iodinated contrast material and renal insufficiency. Radiation is also avoided. The aim of this study is to prospectively compare the diagnostic value of MRA with that of a diagnostic strategy, taking into account catheter angiography, computed tomography angiography (CTA), and lung scintigraphy [ventilation-perfusion (VQ)]. MATERIAL AND METHODS: Magnetic resonance angiography was done in 48 patients with clinically suspected pulmonary embolism (PE) using fast gradient echo coronal acquisition with gadolinium. Interpretation was done with native coronal images and multiplanar maximum intensity projection reconstructions. Results were compared to catheter angiography (n=15), CTA (n=34), VQ (n=45), as well as 6-12 months clinical follow-ups, according to a sequenced reference tree. RESULTS: The final diagnosis of PE was retained in 11 patients (23%). There were two false negatives and no false positive results with MRA. Computed tomography angiography resulted in no false negatives or false positives. Magnetic resonance angiography had a sensitivity of 82% and a specificity of 100%. CONCLUSION: In our study, pulmonary MRA had a sensitivity of 82% and a specificity of 100% for the diagnosis of PE, with slightly less sensitivity than CTA. In the diagnostic algorithm of PE, pulmonary MRA should be considered as an alternative to CTA when iodine contrast injection or radiation is a significant matter.     

40层螺旋CT在肺动脉栓塞诊断中的应用价值

目的:探讨40层螺旋CT在肺动脉栓塞中的应用价值.方法:使用40层螺旋CT扫描机(Siemens Defination AS 40)对临床初步诊断肺动脉栓塞的38例患者进行研究.采用层厚5 mm行胸部增强扫描.利用3D后处理工作站进行重建为0.75 mm的轴面及多平面重建(MPR).比较层厚5 mm和1mm的轴面图像及MPR图像.结果:CT诊断肺动脉栓塞31例.病变共累计肺动脉260支.对于主肺动脉及肺叶动脉栓塞,3种图像检出结果一致.但对于肺段及亚段肺动脉栓塞的显示,层厚0.75 mm优于5 mm,差异有显著性意义(P<0.01),0.75 mm的MPR与轴面图像间差异无显著性意义(P＞0.05).结论:40层螺旋CT在肺动脉栓塞诊断中具有无创、快速、敏感性高的优点,应当作为肺动脉栓塞的首选检查方法.