Imaging processing for CT angiography of the cervicocranial arteries: evaluation of reformatting technique

PURPOSE: The aim of this study was to compare computed tomography angiography (CTA) sliding-thin-slab (STS) multiplanar reformatting (MPR), STS maximum intensity projection (MIP) and three-dimensional (3D) volume rendering (VR) reformatting techniques in the evaluation of cervicocranial arteries. MATERIALS AND METHODS: Twenty patients examined with multislice CT were included in this study. CTA images were reformatted as STS-MIP, STS-MPR and 3DVR in orthogonal planes and in the oblique-coronal plane. Images were evaluated in consensus by two radiologists, with a third radiologist to resolve discordances in grading image quality parameters. The Spearman correlation analysis was performed to compare results and to obtain the correlation between scores resulting from the evaluation of parameters considered with the different techniques used (STSMIP, STS-MPR and 3DVR). RESULTS: STS-MIP images were significantly superior to STSMPR images for all parameters considered (p<0.05). Obliquecoronal 3DVR images were significantly superior to obliquecoronal STS-MIP images in the evaluation of vertebrobasilar vessels (p<0.05); in all other cases, 3DVR images were equivalent to STS-MIP images. CONCLUSION: STS-MIP images should be the primary reformatting technique for CTA of the cervicocranial arteries in addition to viewing the source images; 3DVR images can play an important role after a previsional diagnosis is made on the STS-MIP images.     

CT in vascular pathologies

Since the introduction of helical scanners, CT angiography (CTA) has achieved an essential role in many vascular applications that were previously managed with conventional angiography. The performance of CTA is based on the accurate selection of collimation width, pitch, reconstruction spacing and scan delay, which must be modulated on the basis of the clinical issue. However, the major improvement of CT has been provided by the recent implementation of many post-processing techniques, such as multiplanar reformatting, shaded surface display, maximum intensity projections, 3D perspectives of surface and volume rendering, which simulate virtual intravascular endoscopy. The integration of the potentialities of the scanner and of the image processing techniques permitted improvement of: (a) the evaluation of aneurysms, dissection and vascular anomalies involving the thoracic aorta; (b) carotid artery stenosis; (c) aneurysms of abdominal aorta; (d) renal artery stenosis; (e) follow-up of renal artery stenting; and (f) acute or chronic pulmonary embolism. Our experience has shown that the assessment of arterial pathologies with CTA requires the integration of 3D post-processing techniques in most applications. Received 23 December 1997; Accepted 2 January 1998     

Intimal tears in thoracic aortic dissection: appearance on MDCT with virtual angioscopy

OBJECTIVE: The location, number, size, and configuration of intimal tears in aortic dissection have important therapeutic and prognostic implications. Planning of procedures to treat complications of aortic dissection may require precise delineation of the intimal tears. The purpose of this article is to illustrate the ability of MDCT using multiplanar image reformatting and virtual angioscopy to depict the location and appearance of intimal tears and fenestrations within dissection flaps in cases of thoracic aortic dissection. CONCLUSION: MDCT with virtual angioscopy can depict the configuration of intimal tears in cases of thoracic aortic dissection, which may facilitate therapeutic planning.     

Spiral CT angiography of aortic dissection

Spiral CT angiography (CTA) is one of the newest imaging techniques used for the evaluation of aortic dissection. Current spiral CT scanners with high-performance tubes and subsecond scanning allow increased regions of coverage. Large volumes of data are rapidly acquired through the aorta during maximum contrast enhancement. Multiplanar reformat (MPR), curved planar reformat (CPR), and 3-D rendering techniques including shaded surface display (SSD) and maximum intensity projection (MIP) are then applied to the data to generate CT angiographic images of the aorta. Emergent spiral CTA may be performed in patients with suspected aortic dissection who are hemodynamically stable. Postprocessing is performed immediately following data acquisition and can provide additional information for aortic dissection diagnosis and clinical management. The technique, applications, and limitations of spiral CTA for the evaluation of aortic dissection will be discussed relative to the role of other imaging modalities.     

腹部小动脉夹层64层螺旋CT血管造影表现

目的探讨腹部小动脉夹层64层螺旋CT血管造影（CTA）的表现。方法回顾性分析11例腹部小动脉夹层患者CT原始及后处理图像,主要应用容积显示（VR）、曲面重组（CPR）、最大密度投影（MIP）、多平面重组（MPR）等后处理技术,进行腹腔干、肠系膜上动脉、肾动脉图像重建观察夹层情况。结果MSCTA能清晰显示腹部小动脉夹层,其中肠系膜上动脉夹层5例,腹腔干夹层4例,肾动脉夹层2例。结论64层CT及其后处理技术对腹部小动脉夹层及相关疾病有很好的诊断价值,为临床诊断和治疗提供了依据。     

Thoracic aortic stent graft: comparison of contrast-enhanced MR angiography and CT angiography in the follow-up: initial results

The objective of this study was to compare contrast-enhanced magnetic resonance angiography (CE MRA) and multislice computed tomographic angiography (MS CTA) in the follow-up of thoracic stent-graft placement. The CE MRA and MS CTA were performed following nitinol stent-graft treatment due to thoracic aneurysm (n=4), intramural bleeding (n=2) and type-B aortic dissection (n=5). Corresponding evaluation of arterial-phase imaging characteristics focused on the stent-graft morphology and leakage assessment. Stent-graft and aneurysm extensions were comparable between both techniques. Complete exclusion (aneurysm, n=4; dissection, n=2) was assessed with high confidence with CE MRA and MS CTA. Incomplete exclusion (intramural bleeding, n=2; dissection, n=3) was assigned to lower confidence scores on CE MRA compared with MS CTA. On CE MRA the stent-graft lumen demonstrated an inhomogeneous signal, the stent struts could not be assessed. The CE MRA can be used as alternative non-invasive imaging for follow-up of nitinol stent grafts. Arterial-phase leak assessment can be less evident in CE MRA compared with MS CTA studies; therefore, the use of late-phase imaging seems to be necessary. The diagnostic gap of stent-graft fracture evaluation using MRA may be filled with plain radiographs.     

64层CTA对急性非外伤性蛛网膜下腔出血的应用价值

目的：用64层螺旋CTA评价急性非外伤性蛛网膜下腔出血（SAH）病因并选择治疗方法。方法：对68例急性非外伤性SAH患者发病7天内行CTA检查,明确病因,根据CTA结果选择治疗方法并评价疗效。图像处理采用MPVR、MIP及3DVR重建。结果：68例SAH患者均经DSA及外科手术证实。其中45例为动脉瘤破裂所致,1例血管炎,2例动脉硬化,1例夹层动脉瘤,19例动脉无明显异常。68例SAH中64例由CTA做出病因诊断（准确率94．1％、敏感性91．8％、特异性100％、阳性预测值100％、阴性预测值82．6％）。CTA直接显示43例动脉瘤,1例血管炎及1例夹层动脉瘤。43例动脉瘤有42例根据CTA结果选择治疗（97．7％）。其中栓塞29例,有26例（89．7％）栓塞满意。13例行外科手术钳闭。结论：64层CTA能准确评价SAH病因及动脉瘤的特征。对选择治疗方法十分有价值。     

Incidental myocardial perfusion defect detected on ECG-gated CT aortogram

We report the case of a 49-year-old man with a history of diabetes and hypertension who presented to the emergency room with intermittent chest pain radiating to the back for one day. An electrocardiogram-gated CT aortogram excluded the emergency department's primary consideration of aortic dissection, but incidentally revealed a myocardial perfusion defect and corresponding coronary artery stenosis. Cardiac catheterization performed the following day confirmed the CT findings and the patient underwent angioplasty and stent placement. We show that despite a different protocol than coronary CTA or myocardial perfusion CT, a gated CTA for dissection (CT aortogram) is capable of detecting resting perfusion abnormalities in patients presenting to the emergency room with chest pain.     

The emerging role of multidetector row CT angiography in the diagnosis of cervical arterial dissection: preliminary study

Introduction Cervical artery dissection is an important cause of ischemic stroke, particularly in young patients. The diagnosis can be made with invasive catheter angiography or non-invasive imaging, either with MRI in conjunction with MR angiography (MRA) or CT angiography (CTA). Both modalities have been shown to have a high specificity and sensitivity. New developments such as multi-slice CTA (MSCTA) are emerging as an alternative methods for imaging the cervical and intracranial arteries. However, the contribution of modern MSCTA to carotid artery dissection has not been reported.Methods We present a retrospective series of seven patients in whom both MSCTA and cervical axial T1 MRI and MRA were performed in the acute to subacute setting of internal carotid artery dissection.Results Carotid artery dissection was identified in all seven patients by MSCTA. The combination of MRI and MRA identified dissection in five of the seven patients. Additionally, a pseudoaneurysm was identified by MSCTA that was missed by MRI and MRA.Conclusion Our findings confirm that MSCTA is a complementary technique in comparison to cervical axial T1 MRI and cervical MRA for diagnosing carotid artery dissection, and at times may provide additional information that can impact patient management.     

Computed tomographic coronary angiography in patients with surgically treated type A aortic dissection: preliminary results

Acute type A aortic dissection is a serious emergency with a mortality rate of up to 40% within the first 24 h when left untreated. Surgical therapy needs to be initiated promptly. Due to this urgent situation, preoperative evaluation of the coronary arteries is not routinely performed in these patients. The aim of this study was to evaluate the accuracy of 64-slice computed tomography angiography (CTA) for postoperative coronary artery assessment in these patients. Ten consecutive patients with two or more cardiovascular risk factors were prospectively enrolled. Patients had type A aortic dissection treated surgically with a supracoronary graft of the ascending aorta. Performance of CTA to exclude significant stenosis (>50% lumen narrowing) and/or coronary artery dissection was compared with quantitative coronary angiography. A total of 147 segments were evaluated. Three segments (2%) were excluded from analysis. CTA correctly assessed one of three significant stenoses in three patients and correctly excluded coronary artery disease (CAD) in six of ten patients. One patient was rated false positive. Overall accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CT for identifying coronary artery disease by segment was 98%, 33%, 99%, 50%, and 99%, respectively (P < 0.05). By patient, it was 70%, 33%, 86%, 50%, and 75%, respectively. No coronary artery dissection was found. Noninvasive CTA may be a viable alternative to conventional angiography for postoperative coronary artery evaluation in patients with surgically treated type A aortic dissection and cardiovascular risk factors. An NPV of 99% should allow for reliable exclusion of CAD. Further studies with higher patient numbers are warranted.     

Acute subarachnoid hemorrhage: using 64-slice multidetector CT angiography to “triage” patients’ treatment

Introduction To evaluate the clinical role of CT angiography (CTA) in patients with acute subarachnoid hemorrhage (SAH) for treatment decision-making.Methods Consecutive patients with acute SAH had CTA using a 64-slice scanner for initial clinical decision-making. Image processing included multiplanar volume reformatted (MPVR) maximum intensity projections (MIP) and 3D volume-rendered reconstructions. CTAs were used for (1) evaluating the cause of SAH, and (2) triaging aneurysm-bearing patients to the more appropriate management, either surgical clipping or endovascular coiling. CTA findings were confirmed by neurosurgical exploration or catheter angiography (digital subtraction angiography, DSA). Successful coiling provided evidence that triaging to endovascular treatment was correct.Results Included in the study were 73 patients. CTA findings were confirmed by DSA or neurosurgical operation in 65 patients, and of these 65, 47 had aneurysmal SAH, 3 had vasculitis, 1 had arterial dissection and 14 had no underlying arterial abnormality. The cause of SAH was detected with CTA in 62 out of the 65 patients (95.4%, sensitivity 94%, specificity 100%). CTA revealed the aneurysm in 46 of 47 patients (98%, sensitivity 98%, specificity 100%, positive predictive value 100%, negative predictive value 82.3%), 1 of 3 vasculitides and 1 of 1 dissection. Of the 46 patients with aneurysm, 44 (95.7%) were referred for treatment based on CTA. In 2 patients (2 of 46, 4.4%) CTA was not informative enough to choose treatment requiring DSA. Of the 44 patients, 27 (61.4%) were referred to endovascular treatment and successful coiling was achieved in 25 (25 of 27, 92.6%).Conclusion CTA using a 64-slice scanner is an accurate tool for detecting and characterizing aneurysms in acute SAH. CTA is useful in the decision process whether to coil or clip an aneurysm.     

Simultaneous assessment of coronary stenosis, myocardial perfusion, and ventricular function in a patient with acute myocardial infarction

Cardiac CT angiography (CTA) is an ideal tool to investigate cardiac and noncardiac causes of acute chest pain. In this case, careful planning of the CTA acquisition and reconstruction limits permitted not only the exclusion of aortic dissection and provided high resolution images of coronary anatomy but also showed a concordant abnormality in myocardial perfusion and ventricular function in the setting of an acute coronary syndrome. Detailed planning of every CTA acquisition reconstruction protocol is essential to obtain the information necessary for clinical decision-making strategies and interventions in the patient with chest pain.     

Rational radiologic after-care of endoluminal aortic bypass

Goal. To identify essential and relevant diagnostic algorithms in the follow-up of stent-grafts placed for aortic dissections and aneurysms based on our 7 years experience including the use of more than 10 different devices. Material and Methods. Evaluation of conventional biplane imaging, angiography, sonography, CT and MR in the efficacy of demonstrating endoleaks, sac shrinkage, changes of stent-graft integrity and, with special reference to MR-compatibility of various stent-graft devices. Results. Endoleaks are found in 20–30% of patients after endovascular exclusion of abdominal aortic aneurysms. However, this rate neither necessarily reflects the clinical course nor the onset and course of sac shrinkage. Physical long-term integrity of the devices is seen best on conventional bi-plane radiographs. Sonography is helpful only in selected patients (non-obese, good compliance) otherwise not providing information precisely enough for sac control. As gold standard both CT (CTA) and MR (MRA) are equally effective in the follow-up of endovascular stent-grafts, allowing 3D control of sac geometry in aneurysmal disease or hemodynamic changes in stent-grafts for aortic dissection. MRI is considered to be more effective in the detection of small endoleaks. Angiography is inferior to CT and MRI in the diagnosis of endoleaks and thus is required only for intervention planning in patients with suspected endoleaks. Two of 8 evaluated stent-graft devices proved to be prohibitive for MRI because of their severe artifacts productions (Life-path, Zenith) as a result of their thick metallic meshwork. Conclusion. CT including CTA with 2D and 3D reformatting is the method of choice for the follow up of stent-graft treatment of aortic disease. Depending on availability, MRI may be used alternatively. In young patients and for those with contraindications to iodinated contrast media MRI is a perfectly equivalent alternative. Especially in patients with known contraindications to iodinated contrast media the MR-compatibility should be taken into consideration in the choice of the endovascular device.     

Role of Computed Tomography Angiography in Setting of Spontaneous Coronary Artery Dissection

Spontaneous coronary artery dissection (SCAD) is an infrequent cause of acute coronary syndrome, predominantly affecting young women. Catheter-based coronary angiography is the gold standard diagnostic test, especially when coupled with intracoronary imaging. Conservative management in stable patients is the preferred approach given the increased risk of complications associated with percutaneous interventions. Noninvasive coronary computed tomography angiography (CTA) has a potential role in the diagnosis and follow-up of SCAD. CTA also plays a role in screening for extracoronary vascular abnormalities frequently associated with SCAD. The goal of this article is to review the potential role of CTA in evaluating SCAD.     

Comparison of multidetector CT angiography and MR imaging of cervical artery dissection

BACKGROUND AND PURPOSE: Conventional angiography has been historically considered the gold standard for the diagnosis of cervical artery dissection, but MR imaging/MR angiography (MRA) and CT/CT angiography (CTA) are commonly used noninvasive alternatives. The goal of this study was to compare the ability of multidetector CT/CTA and MR imaging/MRA to detect common imaging findings of dissection.MATERIALS AND METHODS: Patients in the data base of our Stroke Center between 2003 and 2007 with dissections who had CT/CTA and MR imaging/MRA on initial work-up were reviewed retrospectively. Two neuroradiologists evaluated the images for associated findings of dissection, including acute ischemic stroke, luminal narrowing, vessel irregularity, wall thickening/hematoma, pseudoaneurysm, and intimal flap. The readers also subjectively rated each vessel on the basis of whether the imaging findings were more clearly displayed with CT/CTA or MR imaging/MRA or were equally apparent.RESULTS: Eighteen patients with 25 dissected vessels (15 internal carotid arteries [ICA] and 10 vertebral arteries [VA]) met the inclusion criteria. CT/CTA identified more intimal flaps, pseudoaneurysms, and high-grade stenoses than MR imaging/MRA. CT/CTA was preferred for diagnosis in 13 vessels (5 ICA, 8 VA), whereas MR imaging/MRA was preferred in 1 vessel (ICA). The 2 techniques were deemed equal in the remaining 11 vessels (9 ICA, 2 VA). A significant preference for CT/CTA was noted for VA dissections (P < .05), but not for ICA dissections.CONCLUSION: Multidetector CT/CTA visualized more features of cervical artery dissection than MR imaging/MRA. CT/CTA was subjectively favored for vertebral dissection, whereas there was no technique preference for ICA dissection. In many cases, MR imaging/MRA provided complementary or confirmatory information, particularly given its better depiction of ischemic complications.

Dissection of the extracranial arteries accounts for 10%–25% of strokes in young and middle-aged patients.¹ It may be spontaneous or traumatic and can cause a variety of clinical presentations, including stroke, headache, neck pain, tinnitus, Horner syndrome, and cranial neuropathies.^1-4 Dissections are typically diagnosed on the basis of a combination of the clinical presentation, imaging studies (conventional angiography, CT/CT angiography [CTA], MR imaging/MR angiography [MRA], and sonography), and exclusion of other arterial disease, particularly atherosclerosis.^1,2,5 In patients with mild or atypical symptoms, noninvasive imaging may facilitate earlier diagnosis and prevent embolic ischemic complications with the use of antithrombotic therapy.^3,6Conventional angiography has historically been considered the gold standard for dissection diagnosis, but it has limitations, which include its cost and invasiveness.^1,7,8 Although the angiographic appearance of dissection is often characteristic, it does not assess the vessel wall for intramural hematoma; because of this feature, dissections in unusual locations or with atypical morphology may be misclassified or attributed to other processes. MR imaging/MRA and CT/CTA have emerged as viable alternatives for both diagnosis and follow-up of dissection.^9-15 In general, the 2 techniques have different strengths and weaknesses. Diffusion-weighted MR imaging is a powerful technique for detecting acute stroke,¹⁶ which may then lead to increased scrutiny of the upstream arterial tree. Axial T1-weighted fat-suppressed images can detect the methemoglobin of the intramural hematoma within the false lumen, a finding referred to as a crescent sign.^9,13 Multidetector CT/CTA has enabled routine acquisition of thinner sections with rapid imaging times, facilitating multiplanar and volume reconstructions. Additionally, it is more widely available (especially at night), has fewer contraindications, and provides greater spatial resolution than MR imaging/MRA. However, the use of ionizing radiation in the relatively young population of patients with dissection is potentially concerning, especially given the often frequent follow-up studies in these patients.Only 1 study to date has compared CT/CTA with MR imaging/MRA for evaluation of dissection, retrospectively reviewing 7 internal carotid dissections and showing CTA to be marginally more effective in the identification of the dissected vessel.¹¹ To our knowledge, this current study is the largest comparative series of cervical artery dissection imaged with both tomographic techniques. Given the higher spatial resolution of CT/CTA, we hypothesized that CT/CTA may be particularly suited to visualize dissections within the smaller vertebral arteries. Additionally, we hypothesized that in a series of known dissections, CT/CTA would be more sensitive to identify specific imaging features associated with dissections.     

下肢动脉闭塞性病变的64层CT血管造影与DSA的对照研究

目的对照DSA,研究64层螺旋CT血管造影(CTA)对下肢动脉闭塞性病变诊断的临床应用价值。方法对31例下肢动脉闭塞性病变患者行64层螺旋CTA检查,检查后2周内行DSA。CT数据重建采用最大密度投影、容积重建及多平面重建技术。DSA采用步进跟踪造影技术或分段DSA进行下肢血管检查,将CTA与DSA结果比较。结果在216个动脉节段中,2种检查方法狭窄程度显示一致的有157个,被CTA高估13个,低估6个。CTA对下肢动脉狭窄程度≥50%诊断的灵敏度为98.21%,特异度96.15%,准确率97.22%,阳性预测值96.49%,阴性预测值98.04%。结论64层CT血管造影是下肢动脉闭塞性病变评估的可靠方法,可为制订介入治疗方案提供准确的参考依据。     

64层螺旋CT血管造影在急重症胸痛诊断中的应用

目的 探讨64层螺旋CT血管造影在胸心部血管性病变所致急重症胸痛诊断中的价值. 方法 回顾性分析34例行64层螺旋CT血管造影检查并经证实的由血管性病变引起的急重症胸痛患者,利用多平面重建、最大密度投影、曲面重建以及容积再现技术进行图像后处理并分析其影像学特点. 结果 CT血管造影显示急性主动脉夹层13例,急性肺动脉栓塞9例,急性冠状动脉综合征12例,所有病例最终经过临床证实. 结论 64层螺旋CT血管造影在急重症胸痛诊断中有重要的实际应用价值,可以作为急重症胸痛的重要检查手段.     

Coronary CTA co-registration for guiding antegrade dissection re-entry in chronic total occlusion percutaneous coronary intervention

The simultaneous display of the proximal cap and distal CTO segment (including the localization of calcifications) on CTA offers the unprecedented opportunity for influencing ADR.² Herein, we present the emerging application of CTA co-registration for guiding ADR strategy in CTO PCI by: 1) clarification of proximal cap ambiguity, 2) navigation of intra-CTO dissection trajectory and 3) selection of the most optimal re-entry site. We believe that wider adoption of CTA might improve the efficiency and success rates of ADR.     

A novel application of CT angiography to detect extracoronary vascular abnormalities in patients with spontaneous coronary artery dissection

BackgroundSpontaneous coronary artery dissection (SCAD) is associated with extracoronary vascular abnormalities, which depending on type and location may warrant treatment or provide additional diagnostic or prognostic information about this uncommon entity. Fibromuscular dysplasia (FMD), aneurysms, and dissections have been detected in multiple vascular territories by magnetic resonance angiography, CT angiography (CTA), and catheter angiography. The optimal modality to detect extracoronary vascular abnormalities is unknown. We highlight the technique and feasibility of a novel CTA protocol to detect extracoronary vascular abnormalities in these patients, incorporating patient safety and convenience.MethodsThe complete CTA protocol consisting of a single CTA of the neck, chest, abdomen, and pelvis was performed on 39 SCAD outpatients. All examinations were performed with 200 mL of low-osmolar contrast agent and used radiation dose modulation techniques. Average volume CT dose index was 9 mGy for the chest, abdomen, and pelvis portions and 21 mGy for the neck portion. Studies were independently reviewed by 2 senior vascular radiologists.ResultsTwo patients had nondiagnostic CTA neck evaluation because of technical acquisition errors. Extracoronary vascular abnormalities were detected in 27 of 39 patients (69%). Catheter angiography detected brachial artery FMD in 1 patient, a vascular bed not included in the SCAD CTA protocol. Extracoronary vascular abnormalities were common, including FMD, aneurysms, dissection, and aortic tortuosity, and were seen in the iliac (36%), carotid and/or vertebral (31%), splanchnic (10%), and renal (26%) arteries and in the thoracic and/or abdominal aorta (10%).ConclusionsThe frequency of extracoronary vascular abnormalities and extent of territories identified the CTA protocol in our cohort are high. A tailored CTA may be the optimal imaging technique for detecting extracoronary vascular abnormalities in patients with suspected underlying vasculopathy. Although the clinical significance of extracoronary vascular abnormalities remains unclear, detection of these abnormalities has identified patients in whom cerebral imaging and serial monitoring have been recommended.     

三维DSA在主动脉夹层腔内隔绝术中的应用

目的 探讨旋转三维重建数字减影血管成像(3D DSA)在主动脉夹层腔内隔绝术中的应用价值.方法 2006年1月至2010年5月,25例胸主动脉夹层患者接受腔内隔绝术治疗,其中5例患者CTA以及常规DSA均不能显示破口位置,我们对其采用了3D DSA检查.结果 通过3D DSA清楚显示破口,成功实施支架置入术.结论 3D...