Multi-slice 3D-CTA - an improvement over single slice helical CTA for cerebral aneurysms

Comparison of metal artifact reduction using single-energy CT and dual-energy CT with various metallic implants in cadavers

OBJECTIVES

The purpose of this study was to compare the effectiveness of metal artifact reduction using Single Energy Metal Artifact Reduction (SEMAR) and Dual Energy CT (DECT).

MATERIALS AND METHODS

Six cadavers containing metal implants in the head, neck, abdomen, pelvis, and extremities were scanned with Standard, SEMAR, and DECT protocols on a 320-slice CT scanner. Four specialized radiologists blinded to acquisition methods rated severity of metal artifacts, visualization of anatomic structures, diagnostic interpretation, and image preference with a 5-point grading scale.

RESULTS

Scores were significantly better for SEMAR than Standard images in the hip, knee, pelvis, abdomen, and maxillofacial scans (3.25 ± 0.88 versus 2.14 ± 0.93, p < 0.001). However, new reconstruction artifacts developed in SEMAR images that were not present in Standard images. Scores for severity of metal artifacts and visualization of smooth structures were significantly better for DECT than Standard images in the cervical spine (3.50±0.50 versus 2.0±0.58, p < 0.001) and was preferred over Standard images by one radiologist. In all other cases, radiologists preferred the Standard image over the DECT image due to increased image noise and reduced low-contrast resolution with DECT. In all cases, SEMAR was preferred over Standard and DECT images.

CONCLUSION

SEMAR was more effective at reducing metal artifacts than DECT. Radiologists should be aware of new artifacts and review both the original and SEMAR images. When the anatomy or implant is relatively small, DECT may be superior to SEMAR without additional artifacts. However, radiologist should be aware of a reduction in soft tissue contrast.

Preoperative Localization of the Carotid Bifurcation for Cervical Carotid Exposure Using the Mastoid-Hyoid Line

Background and Importance:

The location of the carotid bifurcation (CB) is highly variable, which makes precise exposure of the cervical carotid artery difficult, especially in transverse incisions. The method for preoperative localization of the CB is not well established. We used the distance from the mastoid-hyoid (M-H) line to the CB, measured preoperatively with computed tomography angiography, to localize the location of the transverse skin incision. We describe and evaluate the accuracy of a method for preoperative localization of the CB for cervical carotid exposure.

Methods:

The researchers retrospectively evaluated 16 patients with aneurysms arising from the internal carotid artery (ICA) who had received cervical carotid exposure using the localization method of incision and were retrospectively evaluated from February 2018 to November 2019. The method of measurement and localization of the skin incision are described, and two illustrative cases are demonstrated.

Results:

Saccular aneurysms of the ophthalmic (C2) segment and communicating (C1) segment of the ICA were found in 8 and 8 patients, respectively. Nine patients had left-sided exposure, and 7 patients had right-sided exposure. The mean distance from the M-H line to the CB was 2.1 cm (range 0.5–3.5 cm). The accuracy of this method was 93.8%. No paralysis of the depressor anguli oris or the depressor labii inferioris was found postoperatively.

Conclusion:

The distance from the M-H line to the CB can be used to estimate transverse skin incisions for cervical carotid exposure.

Three-dimensional visualization of aneurysm wall calcification by cerebral angiography: Technical case report

BACKGROUND

We describe on a 57-year-old man with an incidental middle cerebral artery (MCA) aneurysm in whom a preoperative standard three-dimensional rotational angiogram (3D-RA) was used to depict luminal morphology along with 3D density rendering to precisely locate aneurysm wall calcification.

METHODS

To detect aneurysm calcification, a native 3D rotational angiogram was acquired for calcium density visualization, followed by an intraarterial contrast-enhanced 3D rotational angiogram in the same location. Both data sets were postprocessed obtaining a 3D calcium volume rendering on a 3D-RA.

RESULTS

Depiction of both the MCA luminal aneurysm morphology as well as calcium-rich components in the aneurysm wall was valuable to determine treatment strategy towards surgery.

CONCLUSION

Imaging of luminal morphology and calcification within the same angiographic procedure allows for a plain and simple estimation of the degree and distribution of brain aneurysm wall calcification with limited amount of additional radiation dosage.

Metal Artifact Reduction for Orthopedic Implants: Brain CT Angiography in Patients with Intracranial Metallic Implants

BACKGROUND

The purpose of this study was to qualitatively and quantitatively evaluate the effects of a metal artifact reduction for orthopedic implants (O-MAR) for brain computed tomographic angiography (CTA) in patients with aneurysm clips and coils.

METHODS

The study included 36 consecutive patients with 47 intracranial metallic implants (42 aneurysm clips, 5 coils) who underwent brain CTA. The computed tomographic images with and without the O-MAR were independently reviewed both quantitatively and qualitatively by two reviewers. For quantitative analysis, image noises near the metallic implants of non-O-MAR and O-MAR images were compared. For qualitative analysis, image quality improvement and the presence of new streak artifacts were assessed.

RESULTS

Image noise was significantly reduced near metallic implants (P < 0.01). Improvement of implant-induced streak artifacts was observed in eight objects (17.0%). However, streak artifacts were aggravated in 11 objects (23.4%), and adjacent vessel depiction was worsened in eight objects (17.0%). In addition, new O-MAR-related streak artifacts were observed in 32 objects (68.1%). New streak artifacts were more prevalent in cases with overlapping metallic implants on the same axial plane than in those without (P = 0.018). Qualitative assessment revealed that the overall image quality was not significantly improved in O-MAR images.

CONCLUSION

In conclusion, the use of the O-MAR in patients with metallic implants significantly reduces image noise. However, the degree of the streak artifacts and surrounding vessel depiction were not significantly improved on O-MAR images.

Ophthalmic artery visualization and morphometry by computed tomography angiography

We assessed the feasibility of using computed tomography angiography (CTA) to visualize the opthalmic artery (OA) and conducted three-dimensional (3D) morphometry. A retrospective analysis of 171 patients was performed using CTA-confirmed normal internal carotid arteries. To identify the OA, multiplanar CT reformations were performed. The OA diameter was compared in patients of different age groups and between males and females. All ophthalmic arteries were detected by 3D volume-rendering (VR) CTA. Bone subtraction was successful in all patients. The mean OA diameter was 1.37 ±0.25 mm in men, 1.35 ±0.16 mm in women (P = 0.188 for gender), 1.38 ±0.25 mm in the <40 years-old group, 1.37 ±0.14 mm in the 40-49 years-old group, 1.36 ±0.16 mm in the 50-59 years-old group, 1.38 ±0.19 mm in the 60-69 years-old group, and 1.34 ±0.17 mm in the > 70 years-old group (P = 0.662 for age group). CTA is a reliable method for visualizing the ophthalmic artery (OA). There are no major differences in OA diameter among gender or age.

Prediction of the microsurgical window for skull-base tumors by advanced three-dimensional multi-fusion volumetric imaging

The surgery of skull base tumors (SBTs) is difficult due to the complex and narrow surgical window that is restricted by the cranium and important structures. The utility of three-dimensional multi-fusion volumetric imaging (3-D MFVI) for visualizing the predicted window for SBTs was evaluated. Presurgical simulation using 3-D MFVI was performed in 32 patients with SBTs. Imaging data were collected from computed tomography, magnetic resonance imaging, and digital subtraction angiography. Skull data was processed to imitate actual bone resection and integrated with various structures extracted from appropriate imaging modalities by image-analyzing software. The simulated views were compared with the views obtained during surgery. All craniotomies and bone resections except opening of the acoustic canal in 2 patients were performed as simulated. The simulated window allowed observation of the expected microsurgical anatomies including tumors, vasculatures, and cranial nerves, through the predicted operative window. We could not achieve the planned tumor removal in only 3 patients. 3-D MFVI afforded high quality images of the relevant microsurgical anatomies during the surgery of SBTs. The intraoperative déjà-vu effect of the simulation increased the confidence of the surgeon in the planned surgical procedures.

Presurgical simulation with advanced 3-dimensional multifusion volumetric imaging in patients with skull base tumors

BACKGROUND

Despite recent diagnostic and technical advancements in the field of neurosurgery, surgical treatment for tumors in the skull base region, ie, skull base tumors (SBTs), remains a challenge.

OBJECTIVE

To validate the utility of presurgical simulation for the treatment of SBTs by 3-dimensional multifusion volumetric imaging (3D MFVI), including volume rendering and image fusion, to combine data from various imaging modalities.

METHODS

We performed presurgical simulation using 3D MFVI for 21 SBTs (acoustic neurinomas, jugular neurinomas, meningiomas, chordomas, and others) in 20 patients. We collected targeted data from computed tomography, magnetic resonance imaging, computed tomography or magnetic resonance angiography, and digital subtraction angiography and combined these data using image-analyzing software. The simulations were used to assess the 3D relationships among the microsurgical anatomical components, the appropriate surgical approach, and the resectable parts of the tumor. Finally, we compared the results of the simulation with the operative results.

RESULTS

In all patients, the 3D MFVI techniques enabled adequate visualization of the microsurgical anatomy and facilitated presurgical simulation, thereby allowing the surgeons to determine an appropriate and feasible surgical approach. All procedures to open the bone window were performed in accordance with the simulations, except for the surgical exposure of the acoustic canal for 2 acoustic neurinomas. In 3 of the 21 cases, tumor removal could not be performed according to the simulations because of unexpected bleeding or other restrictions.

CONCLUSION

The 3D MFVI technique was of a sufficiently high quality to enable visualization of the 3D microsurgical anatomy. This promising method can facilitate determination of the most appropriate approach and safe and precise surgical procedures for SBTs.

Detection and Characterization of Intracranial Aneurysms with Dual-Energy Subtraction CTA: Comparison with DSA

BACKGROUND

to investigate the diagnostic performance of dual-energy subtraction CTA in evaluating intracranial aneurysms by comparison with DSA.

METHODS

ninety-seven patients with suspected intracranial aneurysms were included into our study and completed both 64-section dual-energy subtraction CTA and DSA examinations. Two independent readers retrospectively reviewed all subtraction CTA images in a blinded manner. Sensitivity, specificity, positive predictive value and negative predictive value of subtraction CTA and DSA were calculated on a per-patient and per-aneurysm basis.

RESULTS

according to the reference standard, 96 aneurysms were present in 81 patients and no aneurysm was found in 16 patients. The overall sensitivity, specificity, positive predictive value and negative predictive value of subtraction CTA on a per-aneurysm basis were 98.9, 100, 100 and 94.1%, respectively. DSA prospectively detected 88 aneurysms in 79 of 81 patients. On a per-aneurysm basis, the sensitivity, specificity, positive predictive value and negative predictive value of DSA were 91.7, 100, 100 and 66.7%, respectively.

CONCLUSION

the diagnostic accuracy of 64-section dual-energy subtraction CTA is promising in detection and characterization of intracranial aneurysms. In most cases, it may substitute for conventional DSA as the primary imaging method in the diagnostic work-up of intracranial aneurysms.

[Non-helical overlapping scan (NHOS) for the application of 3D-CT angiography of cerebral blood vessels]

To improve of cerebral blood vessel visualization and reduce cone beam artifacts from high absorbance materials such as bone structure in 3D-CTA of cerebral blood vessels, we suggest that a non-helical overlapping scan (NHOS) be used. We found that the NHOS and the conventional helical scan optimized the conditions for clinical use of the NHOS. Z-resolution in the NHOS was much higher than that in the non-helical scan without slice overlap. FWHM of the NHOS were thin, about 47%, in comparison with that of the helical scan, and NHOS was superior in Z-resolution to that of the helical scan. Moreover, the NHOS had very few artifacts caused by the skull, and was useful for 3D-CTA of cerebral blood vessels.

Aneurysmal subarachnoid hemorrhage diagnosis with computed tomographic angiography and OsiriX

PURPOSE

Recent advances in computed tomographic angiography (CTA) have resulted in its replacing digital subtraction angiography (DSA). However, CTA requires a powerful workstation and experienced technicians for image postprocessing. OsiriX, a free open-source medical imaging software with powerful three-dimensional (3D) capability, enables neurosurgeons to perform 3D rendering without extensive training. In this study, we examined the sensitivity and specificity of CTA with OsiriX as the primary diagnostic tool for intracranial aneurysms.

METHOD

From May 2006 to March 2009, 121 patients with spontaneous subarachnoid hemorrhage (SAH) underwent CTA. The CTA source images were 3D rendered by neurosurgeons using OsiriX. All the possible locations for aneurysms were carefully reviewed. DSA was performed on every patient in any of the following conditions: for negative CTA findings, after surgical clipping of aneurysms or before transarterial embolization of aneurysms.

RESULT

Of the 121 patients, 8 were excluded because DSA data were not available. In the remaining 113 patients, 20 patients had negative CTA findings. CTA with OsiriX detected 106 aneurysms in 93 patients, of which 103 were confirmed by DSA or postoperative DSA; 3 infundibular dilated pouches of small arteries were mistaken for aneurysms. Two anterior communicating artery aneurysms (1.5 mm and 1 mm) were missed by CTA from among all 113 patients. The sensitivity and specificity of CTA for detecting aneurysms on a per-patient basis were 98.9% and 100%, respectively. The sensitivity and specificity of CTA for detecting aneurysms on a per-aneurysm basis for detecting aneurysms were 98.1% and 86.3%, respectively.

CONCLUSION

CTA with OsiriX enables accurate detection of intracranial aneurysms. Cerebral DSA should be reserved for those patients with negative CTA findings.

Dual Energy CT and Its Use in Neuroangiography

The dual energy CT (DECT) technology has been recently employed in the form of two X-ray sources of different energies to enhance the contrast between adjacent structures. Its use in the cardiac arena has been widely highlighted due to the higher temporal resolution. However, it may also be used in the craniocervical and peripheral vasculature for better differentiation between contrast-enhanced vascular lumina and calcified plaques, in the characterisation of ureteric stones, and in the evaluation of hepatic lesions. The objective of this paper is to revisit DECT physics, review the literature and discuss its use in CT neuroangiography with case illustrations from our institution, and impact on dose savings. Key words: Craniocervical CT angiography, Intracranial aneurysms, Radiation dosage, Vascular stenosis

Perioperative evaluation of carotid endarterectomy by 3D-CT angiography with refined reconstruction: preliminary experience of CEA without conventional angiography

Three-dimensional CT angiography (3D-CTA) was employed for perioperative evaluation of carotid endarterectomy (CEA) as an alternative to conventional angiography. A total of 62 carotid arteries were examined before and after CEA, 26 with an early 3D-CT system and 36 with multidetector helical CT allowing sophisticated reconstruction by a personal workstation. In addition to patients who had undergone conventional angiography at other institutes, 10 subjects underwent CEA on the basis of 3D-CTA findings alone. The findings provided detailed information with an excellent view of carotid stenoses. Volume rendering images comprehensively visualized lesions and surrounding structures as well as calcifications, which were also well depicted by maximum intensity projection images. Evaluation of the cerebral circulation is one problem that still requires solution, although cerebral vessels were delineated by 3D-CTA. One patient experienced transient hemiparesis, but no significant permanent deficit. We conclude that 3D-CTA is a safe and accurate modality that is a practical alternative to conventional perioperative angiography.

Multidetector row CT angiography in spontaneous lobar intracerebral hemorrhage: a prospective comparison with conventional angiography

BACKGROUND AND PURPOSE

The aim of our study was to assess the accuracy of multidetector row CT angiography (MDCTA) in the detection of the underlying vascular abnormalities causing spontaneous lobar intracerebral hemorrhage (ICH) compared with conventional digital subtraction angiography (DSA).

MATERIALS AND METHODS

Seventy-eight patients who underwent MDCTA with use of a 16-detector row scanner and DSA were prospectively included in this study. Each study was assessed by 2 independent blinded neuroradiologists; decisions were made in consensus. Findings on CT angiograms, including the original axial data, multiplanar reformations, and volume-rendered images with and without automated bone segmentation, were used to identify the underlying causes of ICH.

RESULTS

Twenty-two of the 78 patients (28.2%) exhibited angiographic abnormalities, including aneurysms of the proximal arteries (n = 9), arteriovenous malformations (n = 7), Moyamoya disease (n = 4), and aneurysms of the distal arteries (n = 2). MDCTA detected the underlying vascular abnormalities in 21 patients except 1 case of small arteriovenous malformation. Overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MDCTA for detection of underlying vascular abnormalities were 95.5%, 100%, 100%, 98.2%, and 98.7%, respectively.

CONCLUSIONS

MDCTA is a highly accurate imaging technique in the diagnosis of underlying vascular abnormalities in patients with spontaneous lobar ICH.

Value of automatic bone subtraction in cranial CT angiography: comparison of bone-subtracted vs. standard CT angiography in 100 patients

Non-contrast-enhanced cranial computed tomography (NECT) and CT angiography (CTA) are the most frequently used modalities in the triage of patients with acute ischemic and hemorrhagic stroke. CTA bone removal can improve the delineation of vasculature closely adjacent to bony structures, which is sometimes limited in standard CTA. The aim of this study was the evaluation of the clinical benefit of bone subtraction (BS) regarding delineation of cerebral vasculature, reading time and depiction of vascular pathologies compared to standard CTA without BS. A total of 100 patients who underwent NECT and supraaortic CTA on a 64-slice CT system were retrospectively included in the study. Bone removal was performed by subtraction of the NECT data from the CTA data using a dedicated workstation. Standard and BS CTA of each patient was reviewed for delineation of cerebral vasculature (grading scale from 1 = "excellent delineation" to 10 = "hardly any delineation"), reading time and depiction of vascular pathologies (standardized catalog) by two blinded readers. For BS data sets, the quality of BS was rated by a combination of the criteria complete bone removal, depiction of vascular structures and sufficient quality for diagnostic evaluation. The use of BS significantly reduced reading time from 4.60 min to 3.49 min (p<0.001). Performing BS, the quality of vascular delineation of the cerebral arteries, cerebral veins and cavernous segment of the ICA increased significantly as compared to standard CTA (1.70 vs. 2.70; 2.60 vs. 4.12; 2.35 vs. 4.40, all p<0.001). Consensus reading showed 41 pathologies in 35 patients. Diagnosis was missed or wrong overall in 15 cases, with 3 missed aneurysms (CTA: 2 vs. BS: 1), 8 wrong stenotic findings (CTA: 3 vs. BS: 5) and 4 missed partial thromboses (CTA: 2 vs. BS: 2). Performing BS in supraaortic CTA for the evaluation of cerebral vasculature reduces reading time and improves delineation of vessels. Diagnostic accuracy in general is not improved by BS, as the diagnostic accuracy of stenotic vessel alterations is reduced by potential truncation artifacts, but the detection rate of cerebral aneurysms slightly increases.

High-concentration contrast media (HCCM) in CT angiography of the carotid system: impact on therapeutic decision making

BACKGROUND

CT angiography (CTA) is a minimally invasive technique that enables precise delineation of extracranial and intracranial vascular anatomy and pathology based on high intravascular density. With a 64-slice MDCT scanner, improved first-pass vascular visualization can be obtained with HCCM (400 mg I/ml) using 25 ml for combined intra-and extracranial studies and 20 ml for intracranial examinations alone. We reviewed 23 patients with extra-cranial stenoocclusive disease and 12 patients with intra-cranial aneurysms. Two additional patients presented with a mycotic aneurysm and a micro arteriovenous malformation (micro-AVM).

RESULTS

In 23 patients with 27 significant (> or =70%) vascular stenoses, high intraluminal contrast density and optimal projection of the stenosis profile facilitated precise delineation of the residual lumen in all vessels affected. Pseudoocclusion was present in 3 of the 27 vessels (11%) and ulceration in 5 (18.5%). CTA, in contrast to digital subtraction angiography (DSA) and magnetic resonance angiography (MRA), was able to delineate the mural constituents of stenoses, particularly marked calcification (present in 17 of 27 vessels, 62.9%). Eccentric vessel wall narrowing indicated dissection in three vessels (11%) and circular postradiation fibrosis was found in two vessels (7.4%). High-quality CTA obviated the need for DSA for diagnostic purposes in every patient. The decision regarding surgical treatment in nine vessels (33%) was influenced by the location of the stenosis relative to the carotid bifurcation, the length of the stenosis, and the level of the carotid bifurcation. Endovascular treatment in 12 vessels (44.4%) and the appropriate choice and placement of endovascular devices was affected by the anatomic configuration of the supraaortic vessels, and by the intrastenotic dimensions relative to the dimensions of the vessel proximal and distal to the stenosis. The anatomic availability of collaterals, relevant for both treatments, was determined via the anterior communicating artery (ACoA) in 91.3% of patients and the posterior communicating artery (PCoA) in 80.4% of patients. Intracranial CTA displayed the lesion location, configuration, size, and orientation in each of the 12 patients with intracranial aneurysms and in the two patients with a micro-AVM and a mycotic aneurysm. The correct diagnosis was established prior to DSA in each patient. Following CTA, the role of DSA was relegated to endovascular therapy in three aneurysms. For surgical candidates, DSA served to exclude potential multiplicity in ten saccular aneurysms and in one mycotic aneurysm. CTA provided information supplementary to DSA in 11 of the 13 aneurysms (84.6%). Delineation of blebs, calcification, thrombus, or incorporation of branches facilitated risk stratification with respect to rupture and to surgical or endovascular treatment.

CONCLUSION

Advantages of CTA, such as virtual independence from the hemodynamic situation, delineation of landmarks and vessel wall calcification, and the ability to quantify vessels and aneurysms, distinguish this technique from other noninvasive vascular imaging techniques and DSA. Acquired with the use of iodinated HCCM, CT angiograms permit excellent recognition of appropriate diagnostic and interventional treatment paths, thereby facilitating improved decision-making regarding endovascular or surgical treatment.

The study of edge detection of cerebrovascular image based on gabor filter

In order to analyze and process the cerebrovascular image, we research the frame characteristic of the filter's imaginary part based on the analysis of the basic character of the Gabor filter algorithm. In detecting the edge of cerebrovascular image, we introduce the imaginary part of the Gabor filter algorithm as the new image characters of cerebrovascular image, and get a better experiment result by using the analysis strategy of weighted average. At the same time, in order to accelerate the pick process, we improve the Gabor filter algorithm special condition and reduce the timecomplexity of the algorithm greatly.

Multislice computed tomography angiography screening for new aneurysms in patients with previously clip-treated intracranial aneurysms: Feasibility, positive predictive value, and interobserver agreement

OBJECT

Multislice computed tomography (CT) angiography may be useful for screening patients with intracranial aneurysms that are treated with clip occlusion. However, cobalt clips produce much more artifact on CT scans than titanium clips, which may hamper the evaluation of the image obtained at the clip site.

METHODS

The authors screened 415 patients with previously ruptured aneurysms that had been treated using cobalt clips. Screening was performed using multislice CT angiography. The feasibility of this modality for screening these patients (based on the complication risk, CT angiography quality, and artifact avoidance) and interobserver agreement were evaluated. Patients in whom the presence of an aneurysm was suspected based on results of CT angiography studies underwent digital subtraction (DS) angiography. False-negative and false-positive findings were recorded, and the positive predictive value (PPV) was calculated. Eight patients (1.9%) had allergies to the contrast material. The quality of the CT angiography image was suboptimal in 14%. In 52%, clip artifacts hampered evaluation of the clip site. In 65 patients who underwent DS angiography, there were nine false-positive and eight false-negative reports related to aneurysms that were either small, located at the clip site, or were infundibula. The PPV on a per-patient basis was 86% (95% confidence interval [CI] 75-94%); for aneurysms at the clip site it was 83% (95% CI 61-95%); and for aneurysms at different locations it was 91% (95% CI 81-97%). The interobserver agreement was good (kappa = 0.69; 95% CI 0.60-0.78).

CONCLUSIONS

Except for the evaluation of images from the clip site, CT angiography has good feasibility with good PPV and interobserver agreement. Drawbacks are that very small aneurysms can be missed and that visualization is poor at the clip site in patients in whom cobalt clips have been placed for occlusion. This second problem can be expected to resolve with the increasing use of titanium clips.

Venous loop mimicking middle cerebral artery bifurcation aneurysm on computed tomographic angiography—case report

BACKGROUND

CT angiography has been widely used for the detection of cerebral aneurysm. However, there are still limitations despite improving CT angiographic techniques. We describe the unusual case of the detection of a false-positive aneurysm on CT angiography.

CASE DESCRIPTION

A 64-year-old man presented with a 14-day history of severe headache and nuchal rigidity. Brain CT demonstrated no subarachnoid hemorrhage, but cerebrospinal fluid appeared xanthochromic in 3 successive tubes after lumbar puncture. Subsequent CT angiography suggested an aneurysm at the bifurcation of the left MCA. However, at operation, prominent sylvian vein superimposed on the bifurcation of the left MCA, and there was no aneurysm. Follow-up monitoring with conventional angiography at 2 weeks showed no abnormal findings. The patient recovered uneventfully.

CONCLUSION

The case demonstrates that although CT angiography has a reportedly high specificity and sensitivity for the detection of intracranial aneurysm, careful interpretation is required to diagnose intracranial aneurysms.

Postoperative three-dimensional CT angiography after cerebral aneurysm clipping with titanium clips: detection with single detector CT. Comparison with intra-arterial digital subtraction angiography

AIM

To assess the significance of three-dimensional computed tomography angiography (3D-CTA) in detecting remnant necks after cerebral aneurysm clipping.

MATERIALS AND METHODS

A total of 59 patients (77 aneurysms) underwent surgery using titanium clips. Two blinded observers independently evaluated the presence of neck remnants on shaded-surface display (SSD) imaging, volume rendered (VR) imaging, and intra-arterial digital subtraction angiography (IADSA).

RESULTS

Mean sensitivity and specificity for detecting neck remnants were 50.0 and 74.2% for SSD imaging, 61.5 and 82.8% for VR imaging, and 92.3 and 92.2% for IADSA, respectively. Receiver operating characteristic (ROC) analysis revealed excellent diagnostic performance for IADSA [mean area under ROC curve (Az)=0.97], and good diagnostic performance for 3D-CTA (Az=0.70 and 0.76 for SSD and VR, respectively). Specificity of VR was better than that SSD (p=0.082), however, there was no significant difference between them.

CONCLUSION

Use of 3D-CTA techniques can facilitate postoperative evaluation.

Visualization of the intracisternal angioarchitecture at the posterior fossa by use of image fusion

OBJECTIVE

Magnetic resonance (MR) images most clearly visualize intracranial tissues but have some limitations in terms of detailed analysis of the intracisternal vasculature. To compensate for these shortcomings, an image fusion of three-dimensional digital subtraction angiography (DSA) and MR images, DSA-MR fusion, has been developed. The goal of this study was to evaluate the usefulness of DSA-MR fusion for the visualization of the intracisternal arteries and veins at the posterior fossa.

METHODS

Ten consecutive patients (five with neurovascular compression syndrome and five with brain tumors) underwent preoperative DSA-MR fusion. The DSA-MR fusion images were compared with intraoperative findings.

RESULTS

Image fusion was performed within 20 minutes, and the registration error was insignificant in all cases. Image fusion successfully visualized the clear three-dimensional relationships among the intracisternal arteries and veins, cranial nerves, brain tissues, and a lesion, and a specific vessel was easily identified. The findings of the DSA-MR fusion images were surgically confirmed in all patients.

CONCLUSION

Using this advanced image fusion technique coupled with its reasonable postprocessing time, neurosurgeons may more easily and precisely understand the surgical anatomy before surgery than analyzing three-dimensional DSA and MR images separately.

Traumatic arterial injuries of the extremities: initial evaluation with MDCT angiography

OBJECTIVE

The purpose of this study was to retrospectively assess the accuracy of MDCT angiography as the initial diagnostic technique to depict arterial injury in patients with extremity trauma.

MATERIALS AND METHODS

Over 36 months, 87 patients (16 females and 71 males; age range, 16-87 years) with clinically suspected arterial injury after extremity trauma underwent 4-MDCT angiography and 67 ultimately underwent surgery. Eighty patients had blunt injuries, and seven had penetrating injuries. The presence of arterial involvement was investigated prospectively by the radiologist in charge and retrospectively by two independent radiologists. Each detected arterial lesion was then characterized as a spasm, stenosis, occlusion, or rupture. The standard of reference was surgery in 67 patients, angiography in two patients, and clinical and radiologic follow-up findings in 18 patients. MDCT angiography was assessed by means of receiver operating characteristic (ROC) curve analysis for lesion detection and Spearman's rank correlation test for lesion characterization. Image quality, lesion depiction, and artifacts were subjectively assessed.

RESULTS

Sixty-two traumatic arterial lesions were confirmed at surgery in 55 patients. MDCT angiography yielded high accuracy in detection (area under the ROC curve [Az] = 0.96; p < 0.001) and characterization (r = 0.94; p < 0.001) of traumatic arterial injuries and in recognizing an underlying dissection (Az= 0.82; p < 0.001). Prospective sensitivity and specificity were 95% and 87%, respectively, and retrospective sensitivity and specificity were 99% and 87%, respectively. MDCT angiography was considered to be sufficient for a reliable diagnosis in 83 patients (p < 0.001). Image quality and lesion depiction on MDCT angiograms were considered to be good and artifacts were considered mild with substantial interobserver agreement (kappa, 0.62-0.69).

CONCLUSION

MDCT angiography provides significant and reproducible technique for the detection and characterization of arterial injuries to the extremities with high image quality and vascular delineation.

Yield of Short-Term Follow-up CT/MR Angiography for Small Aneurysms Detected at Screening

Background and Purpose— Patients with a history of subarachnoid hemorrhage (SAH) or familial intracranial aneurysms (FIA) are at increased risk for aneurysm formation and rupture. Small aneurysms detected at screening may be left untreated and followed over time. The yield of follow-up CT/MR angiography (CTA/MRA) 1 or 2 years after detection to evaluate growth of these aneurysms is unknown.

Methods— We prospectively followed patients with small aneurysms detected at screening at a 1-year interval using CTA or MRA. We assessed size, site, and number of the aneurysms and risk factors such as smoking, alcohol use, and hypertension. We evaluated the short-term growth and rupture rate and possible risk factors for growth and rupture.

Results— Ninety-three patients (67 with a history of SAH, 16 with FIA, and 10 with a history of both SAH and FIA) with 125 aneurysms underwent CTA/MRA follow-up. Sixty-five patients were followed up once, and 28 patients were followed up twice (median follow-up time, 1.3 years). In 3 of the 93 patients (3.2%), an aneurysm enlarged slightly (0.5 to 1.5 mm). Two patients (2.2%) had a SAH: 1 from an aneurysm at the clip-site from a previous operation that ruptured without enlargement and the other from a newly developed dissecting aneurysm. The only statistically significant risk factor for growth and rupture was a history of both SAH and FIA (relative risk, 10.1; 95% CI, 1.3 to 81.9).

Conclusions— The yield of early follow-up of small aneurysms in patients with a history of SAH or FIA is small and does not eliminate the risk of rupture. Whether follow-up at intervals >1 year is useful requires further study.

Modern cross-sectional imaging in the diagnosis and follow-up of intracranial aneurysms

Digital subtraction angiography (DSA) is still considered the gold standard for most applications in neurovascular imaging. However, with the ongoing development of cross-sectional imaging modalities DSA is increasingly being replaced by less invasive methods. This contribution describes the diagnostic value and the increasing potential of computed tomography angiography (CTA) and magnetic resonance angiography (MRA) in the diagnosis and follow-up of intracranial aneurysms. The main role of CTA is in the diagnosis and therapy planning of ruptured aneurysms; in contrast, MRA plays an increasingly important role in the screening for asymptomatic aneurysms (especially in cases of familial subarachnoid hemorrhage) and in the follow-up after endovascular therapy with coils and/or intracranial stents. Technical issues concerning examination technique are covered here as well as an approach to advanced postprocessing of the image data. Furthermore, a brief outlook on the impact of new developments (MRA with parallel imaging and at 3.0 T) is given.

Computed tomography angiography for the detection and characterization of intra-cranial aneurysms: Current status

Multidetector computed tomography angiography (MD-CTA) of the intra-cranial vessels is now a routine examination, and is becoming fully integrated into the imaging and treatment algorithm of patients presenting with acute subarachnoid haemorrhage in many centres in the UK and Europe. The development and current status of CTA for cerebral aneurysms, and the strengths and limitations of this technique are herein reviewed.

Clinical evaluation of bone-subtraction CT angiography (BSCTA) in head and neck imaging

Fifty-one patients were examined with bone subtraction CT angiography (BSCTA). Data were acquired on 4-and 64-slice spiral CT systems. The post-processing method is based on fully automatic registration of non-enhanced and contrast-enhanced CT data and subsequent selective bone removal. Vascular structures and brain tissue are retained with the original CTA noise level. Image quality and delineation of the pathologic process were assessed and artifacts introduced by the bone removal process recorded. The bone subtraction algorithm worked successfully in all examinations. The processing time was 6 min on average. Image quality was rated excellent in 20 (39%), good in 26 (51%) and acceptable in 5 (10%) patients. Ophthalmic arteries were visible in 12 (24%) patients bilaterally, in 13 (25%) patients unilaterally and in 26 (51%) patients at least at the origin. BSCTA improved visualization of the infraclinoid ICA and the vertebral arteries. The depiction of stenosis of the extracranial ICA and supraclinoid aneurysms was not significantly improved. In patients with suspicion of sinus thrombosis, BSCTA and conventional CTA yielded similar results. To conclude, BSCTA improves the visualization of vessels with close contact to bone and can improve the diagnostic accuracy and therapy planning of infraclinoid aneurysms.

3-Dimensional computed tomographic angiography for use of surgery planning in patients with intracranial aneurysms

BACKGROUND

After subarachnoid haemorrhage (SAH) diagnostic evaluation of the underlying cause is warranted since the rebleeding rate is high. The objective of the study was to answer the question, whether 3-Dimensional computed tomographic angiography (3D-CTA) is able to accurately determine the surgical indications in patients with intracranial aneurysms.

METHODS

After performing 3D-CTA the size of the aneurysm, direction of the aneurysmal dome, neck position and variants of the circle of Willis were analysed. Surgery was performed solely on CTA data in those cases, where the aneurysm was clearly visible. If the findings were negative or inconclusive, intra-arterial digital subtraction angiography (DSA) was also done.

FINDINGS

Between January 2001 and December 2002 100 patients (68 F, 32 M) were examined and 123 aneurysms (86 ruptured and 37 unruptured) were diagnosed. All patients received CTA preoperatively and in 27 patients selective DSA was additionally performed. Postoperatively in 34 patients the operative result was checked by DSA. A good correlation between CTA and the intra-operative findings was present in 92 of 100 patients. One aneurysm was not seen on CTA, but was on DSA. In four cases we could confirm DSA findings in CTA after re-evaluation of the data. In three cases neither CTA nor DSA clearly showed an aneurysm, but it was confirmed during surgery. A good correlation between CTA and DSA was found in 60 of 61 patients (98%). The correlation between CTA and intra-operative findings was good as expected in 92 patients, in 5 patients an aneurysm was detected on re-evaluation. Only one aneurysm could not be demonstrated by CTA but in DSA.

CONCLUSION

CTA is less invasive, less time consuming, cheaper and easier to demonstrate the essential information regarding the aneurysm than DSA. We therefore recommend that following a careful analysis most aneurysms - 92% - can be operated solely on CTA data.

Assessment of real-time 3D visualization for cardiothoracic diagnostic evaluation and surgery planning

RATIONALE AND OBJECTIVES

Three-dimensional (3D) real-time volume rendering has demonstrated improvements in clinical care for several areas of radiological imaging. We test whether advanced real-time rendering techniques combined with an effective user interface will allow radiologists and surgeons to improve their performance for cardiothoracic surgery planning and diagnostic evaluation.

MATERIAL AND METHODS

An interactive combination 3D and 2D visualization system developed at the University of North Carolina at Chapel Hill was compared against standard tiled 2D slice presentation on a viewbox. The system was evaluated for 23 complex cardiothoracic computed tomographic (CT) cases including heart-lung and lung transplantation, tumor resection, airway stent placement, repair of congenital heart defects, aortic aneurysm repair, and resection of pulmonary arteriovenous malformation. Radiologists and surgeons recorded their impressions with and without the use of the interactive visualization system.

RESULTS

The cardiothoracic surgeons reported positive benefits to using the 3D visualizations. The addition of the 3D visualization changed the surgical plan (65% of cases), increased the surgeon's confidence (on average 40% per case), and correlated well with the anatomy found at surgery (95% of cases). The radiologists reported fewer and less major changes than the surgeons in their understanding of the case due to the 3D visualization. They found new findings or additional information about existing findings in 66% of the cases; however, they changed their radiology report in only 14% of the cases.

CONCLUSION

With the appropriate choice of 3D real-time volume rendering and a well-designed user interface, both surgeons and radiologists benefit from viewing an interactive 3D visualization in addition to 2D images for surgery planning and diagnostic evaluation of complex cardiothoracic cases. This study finds that 3D visualization is especially helpful to the surgeon in understanding the case, and in communicating and planning the surgery. These results suggest that including real-time 3D visualization would be of clinical benefit for complex cardiothoracic CT cases.

Prospective, multireader evaluation of image quality and vascular delineation of multislice CT angiography of the brain

The aim of this prospective, multireader trial was to investigate image quality and vascular delineation of cranial multislice CT angiography (MSCTA) to identify strengths and weaknesses of the method. Sixty consecutive patients underwent standardized cranial MSCTA. The mean estimated effective dose was 0.96+/-0.11 mSv. Three masked readers independently graded image quality parameters and vascular delineation on a 5-point scale. Vascular attenuation values and dose-length products were assessed quantitatively. Quantitative parameters were evaluated with a proportional odds regression model with bootstrapped standard errors to adjust the relevant standard errors for correlation within subjects and across readers. The non-parametric Wilcoxon sign-rank test was applied for quantitative measurements. Good to excellent ratings were observed regarding image quality parameters and vascular delineation. The delineation of veins was rated higher than that of arteries (OR 2.00). Smaller arterial segments were rated significantly less favorably than larger segments (OR up to 26.98). Moreover, the cavernous sinus, the C2 segment of the ICA and the communicating arteries demonstrated lower scores. Attenuation values were >240 HU and vessel-to-parenchyma ratios >7 in all vessels. Cranial MSCTA achieved high ratings regarding image quality and vascular delineation. Relative weaknesses were found in small arterial subsegments and in vessels in close topographical proximity to bone.

Multi-slice CT angiography of small cerebral aneurysms: is the direction of aneurysm important in diagnosis?

PURPOSE

Multi-slice CT (MSCT) has great potential in evaluation of vascular structures. Our purpose was to investigate if there is any difference in detection of superiorly, inferiorly and horizontally directed small cerebral aneurysms (<5 mm) on MSCTA compared to digital subtraction angiography (DSA) or surgery.

MATERIALS AND METHODS

One hundred and three consecutive patients who underwent MSCTA and DSA or surgery were included in the study. MSCTA and DSA results were evaluated independently by two different neuroradiologists who performed aneurysm detection, quantitation, and characterization using 2D multiplanar reconstructions, 3D maximum intensity projection and volume-rendered techniques.

FINDINGS

MSCTA detected 49 small cerebral aneurysms (<5 mm) in 37 (36%) of 103 patients. The overall sensitivity, specificity, and accuracy of MSCTA for detecting small aneurysms were 0.85, 0.65, and 0.79, respectively. There was moderate agreement between MSCTA and DSA/surgery for detecting small aneurysms (kappa: 0.51). The sensitivity of detecting small aneurysms directed superiorly, inferiorly and horizontally was 0.94, 0.84, and 0.75, respectively. There was no statistically significant difference in detection between small aneurysms directed superiorly, inferiorly and horizontally on MSCTA (P > 0.05).

CONCLUSION

The direction of small cerebral aneurysms is not important in diagnosis on multi-slice CT scanners, although the detection of small cerebral aneurysms with superior or inferior direction is slightly easier than the detection of horizontally directed aneurysms.

Multi-detector CT angiography of the intra-cranial circulation: normal anatomy and pathology with angiographic correlation

Multidetector computed tomography angiography (MD-CTA) of the intra-cranial circulation shows great potential in the evaluation of intra-cranial vascular disease. Interpreting these studies requires a detailed knowledge of the technique, its advantages and disadvantages, as well as a strong understanding of normal intra-cranial vascular anatomy. The purpose of this review is to describe the technique for MD-CTA, demonstrate normal anatomy, anatomic variants and vascular pathology with an emphasis on aneurysms.

CT Angiography of Intracranial Aneurysms: A Focus on Postprocessing

Computed tomographic (CT) angiography is a well-known tool for detection of intracranial aneurysms and the planning of therapeutic intervention. Despite a wealth of existing studies and an increase in image quality due to use of multisection CT and increasingly sophisticated postprocessing tools such as direct volume rendering, CT angiography has still not replaced digital subtraction angiography as the standard of reference for detection of intracranial aneurysms. One reason may be that CT angiography is still not a uniformly standardized method, particularly with regard to image postprocessing. Several methods for two- and three-dimensional visualization can be used: multiplanar reformation, maximum intensity projection, shaded surface display, and direct volume rendering. Pitfalls of CT angiography include lack of visibility of small arteries, difficulty differentiating the infundibular dilatation at the origin of an artery from an aneurysm, the kissing vessel artifact, demonstration of venous structures that can simulate aneurysms, inability to identify thrombosis and calcification on three-dimensional images, and beam hardening artifacts produced by aneurysm clips. Finally, an algorithm for the safe and useful application of CT angiography in patients with subarachnoid hemorrhage has been developed, which takes into account the varying quality of equipment and software at different imaging centers.

Detection of intracranial aneurysms with multislice CT: comparison with conventional angiography

We assessed the diagnostic accuracy of multislice CT in detection of intracranial aneurysms in patients presenting with subarachnoid or intracranial haemorrhage. Multislice CT and multiplanar digital subtraction angiography (DSA) images were obtained in 50 consecutive patients presenting with subarachnoid (SAH) and/or intracranial haemorrhage and reviewed by three neuroradiologists for the number, size and site of any aneurysms. The CT data were assessed using multiplanar reformats (MPR), maximum-intensity projections (MIP), surface-shaded display (SSD) and volume-rendering (VRT). In conventional angiography 51 aneurysms were detected in 41 patients. CT angiography (CTA) showed up to 48 aneurysms in 39 patients, depending on the observer. The overall sensitivity of multislice CT was 83.3% for small (< 4 mm), 90.6% for medium-size (5-12 mm) and 100% for large (> 13 mm) aneurysms. The sensitivity of multislice CTA to medium-size and large intracranial aneurysm is within the upper part of the range reported for helical single-slice CT. However, as small aneurysms may not be found, DSA remains the standard technique for investigation of SAH.

Detection of Intracranial Aneurysms with Two-dimensional and Three-dimensional Multislice Helical Computed Tomographic Angiography

OBJECTIVE

Computed tomographic angiography (CTA) has become a diagnostic method for the detection of intracranial aneurysms in cases of subarachnoid bleeding. We sought to evaluate the detection of aneurysms with CTA with a novel multislice helical computed tomographic scanner.

METHODS

Prospectively, 179 patients underwent multislice CTA, followed by digital subtraction angiography (DSA) of both carotid arteries with or without the posterior circulation, DSA of one carotid artery with or without the posterior circulation, or DSA of the posterior circulation alone. The total number of carotid arteries studied was 298, and the number of vertebrobasilar arteries studied was 124.

RESULTS

Of 178 aneurysms verified with DSA or intraoperatively, CTA failed to detect 7 aneurysms of 1 to 2 mm and 1 partially thrombosed, 4-mm aneurysm. The sensitivity and specificity of CTA for aneurysm detection were 0.96 and 0.97, respectively.

CONCLUSION

The first generation of multislice computed tomographic technology does not improve CTA to surpass DSA for the detection of small aneurysms of 1 to 2 mm. In practice, however, CTA is superior as a fast noninvasive method without complications.

Comparison between perimesencephalic nonaneurysmal subarachnoid hemorrhage and subarachnoid hemorrhage caused by posterior circulation aneurysms

OBJECT

Some authors have questioned the need to perform cerebral angiography in patients presenting with a benign clinical picture and a perimesencephalic pattern of subarachnoid hemorrhage (SAH) on initial computerized tomography (CT) scans, because the low probability of finding an aneurysm does not justify exposing patients to the risks of angiography. It has been stated, however, that ruptured posterior circulation aneurysms may present with a perimesencephalic SAH pattern in up to 10% of cases. The aim of the present study was twofold: to define the frequency of the perimesencephalic SAH pattern in the setting of ruptured posterior fossa aneurysms, and to determine whether this clinical syndrome and pattern of bleeding could be reliably and definitely distinguished from that of aneurysmal SAH.

METHODS

Twenty-eight patients with ruptured posterior circulation aneurysms and 44 with nonaneurysmal perimesencephalic SAH were selected from a series of 408 consecutive patients with spontaneous SAH admitted to the authors' institution. The admission unenhanced CT scans were evaluated by a neuroradiologist in a blinded fashion and classified as revealing a perimesencephalic SAH or a nonperimesencephalic pattern of bleeding. Of the 28 patients with posterior circulation aneurysms, five whose grade was I according to the World Federation of Neurosurgical Societies scale were classified as having a perimesencephalic SAH pattern on the initial CT scan. The data show that the likelihood of finding an aneurysm on angiographic studies obtained in a patient with a perimesencephalic SAH pattern is 8.9%. Conversely, ruptured aneurysms of the posterior circulation present with an early perimesencephalic SAH pattern in 16.6% of cases.

CONCLUSIONS

This study supports the impression that there is no completely sensitive and specific CT pattern for a nonaneurysmal SAH. In addition, the authors believe that there is no specific clinical syndrome that can differentiate patients who have a perimesencephalic SAH pattern caused by an aneurysm from those without aneurysms. Digital subtraction angiography continues to be the gold standard for the diagnosis of cerebral aneurysms and should be performed even in patients who have the characteristic perimesencephalic SAH pattern on admission CT scans.