[Asymptomatic atherosclerosis of the brachiocephalic arteries: Current approaches to diagnosis and treatment]

Acute cerebrovascular accident (ACVA) and transient ischemic attack are among the leading causes of morbidity, disability, and mortality in the Russian Federation and the world. Ischemic strokes account for 70-80% of all ACVAs, with 20-30% of them being associated with stenotic atherosclerosis of the brachiocephalic arteries (BCA). The paper describes modern views on the problem of asymptomatic BCA atherosclerosis and considers the possibilities of identifying risk groups among the patients with asymptomatic atherosclerosis of the BCA.

Diagnostic Impact of Bone-Subtraction CT Angiography for Patients with Acute Subarachnoid Hemorrhage

BACKGROUND AND PURPOSE

Detection and evaluation of ruptured aneurysms is critical for choosing an appropriate endovascular or neurosurgical intervention. Our aim was to assess whether bone-subtraction CTA is capable of guiding treatment for cerebral aneurysms in patients with acute SAH and could replace DSA.

MATERIALS AND METHODS

We prospectively studied 116 consecutive patients with SAH with 16-detector row bone-subtraction CTA and DSA before intracranial aneurysm treatment. Two independent neuroradiologists reviewed the bone-subtraction CTA blinded to DSA (reference standard). We determined the accuracy of bone-subtraction CTA for aneurysm detection and the measurement of aneurysm dimensions and compared the radiation doses of the 2 imaging modalities.

RESULTS

Seventy-one patients (61%) had 74 aneurysms on DSA. Bone-subtraction CTA detected 73 of these aneurysms, but it detected 1 additional aneurysm. On a per-aneurysm basis, sensitivity, specificity, and positive and negative predictive values for bone-subtraction CTA were 99%, 98%, and 99% and 98%, respectively. For aneurysms of ≤3 mm, sensitivity was 94% (95% CI, 73%-99%). Bone-subtraction CTA slightly overestimated neck and dome diameters by <0.2 mm and overestimated the dome-to-neck ratios by 2% on average. Dose-length product was 565 ± 201 mGy × cm for bone-subtraction CTA and 1609 ± 1300 mGy × cm for DSA.

CONCLUSIONS

Bone-subtraction CTA is as accurate as DSA in detecting cerebral aneurysms after SAH, provides similar information about aneurysm configuration and measures, and reduces the average effective radiation dose for vascular diagnostics by 65%. Diagnostic equivalence in association with dose reduction suggests replacing DSA with bone-subtraction CTA in the diagnostic work-up of spontaneous SAH.

Use of articulated registration for response assessment of individual metastatic bone lesions

Accurate skeleton registration is necessary to match corresponding metastatic bone lesions for response assessment over multiple scans. In articulated registration (ART), whole-body skeletons are registered by auto-segmenting individual bones, then rigidly aligning them. Performance and robustness of the ART in lesion matching were evaluated and compared to other commonly used registration techniques. Sixteen prostate cancer patients were treated either with molecular targeted therapy or chemotherapy. Ten out of the 16 patients underwent the double baseline whole-body [F-18]NaF PET/CT scans for test-retest (TRT) evaluation. Twelve of the 16 patients underwent pre- and mid-treatment [F-18]NaF PET/CT scans. Skeletons at different time points were registered using ART, rigid, and deformable (DR) registration algorithms. The corresponding lesions were contoured and identified on successive PET images based on including the voxels with the standardized uptake value over 15. Each algorithm was evaluated for its ability to accurately align corresponding lesions via skeleton registration. A lesion matching score (MS) was measured for each lesion, which quantified the per cent overlap between the lesion's two corresponding contours. Three separate sensitivity studies were conducted to investigate the robustness of ART in matching: sensitivity of lesion matching to various contouring threshold levels, effects of imperfections in the bone auto-segmentation and sensitivity of mis-registration. The performance of ART (MS = 82% for both datasets, p ≪ 0.001) in lesion matching was significantly better than rigid (MS(TRT)=53%, MS(Response)= 46%) and DR (MS(TRT)=46%, MS(Response)=45%) algorithms. Neither varying threshold levels for lesion contouring nor imperfect bone segmentation had significant (p~0.10) impact on the ART matching performance as the MS remained unchanged. Despite the mis-registration reduced MS for ART, as low as 67% (p ≪ 0.001), the performance remained to be superior to the rigid and DR algorithms. ART is not only robust to contouring threshold levels for bone lesions, but also outperforms rigid and DR algorithms in lesion matching. ART therefore enables the study of TRT variability and treatment assessment of individual bone lesions.

Automated subtraction CT angiography for visualization of the whole brain vasculature: a feasibility study

RATIONALE AND OBJECTIVES

To develop an automated computed tomography angiography (CTA) imaging protocol that allows visualization of the whole brain vasculature and evaluate the clinical usefulness of the technique for delineation of intracranial vessels in patients with cerebrovascular disorders.

MATERIALS AND METHODS

We prospectively included 100 patients who underwent automated subtraction CTA for suspected cerebrovascular disorders. The nonenhanced and contrast enhanced scans were obtained with the same table feeding speed. The x-ray tube start angles of the two scans were matched to enable accurate registration and subtraction of the CTA datasets. Subtracted CTA datasets were reformatted as three-dimensional volume rendering and maximum intensity projection images for further review. Two independent readers assessed the quality of subtraction and delineation of intracranial vessels. The visibility of ophthalmic arteries was also assessed.

RESULTS

Subtraction was successful in all patients. The image quality of bone removal was rated excellent in 95 patients, with no or minimal bone remnants. Incomplete bone removal was observed in five patients because of severe motions between the scans. In 97 of 100 patients, arterial segments at the circle of Willis could be clearly visualized. Excellent delineation of bilateral ophthalmic arteries was possible in 81 of 100 patients.

CONCLUSIONS

The whole brain vasculature would be clearly visualized by using the optimized automated CTA protocol. Our automated, single-source, dual-energy subtraction CTA protocol is a fully automated subtraction method that is capable of delineating major intracranial vessels as well as very small arteries.

Improved arterial visualization in cerebral CT perfusion-derived arteriograms compared with standard CT angiography: a visual assessment study

BACKGROUND AND PURPOSE

Invasive cerebral DSA has largely been replaced by CTA, which is noninvasive but has a compromised arterial view due to superimposed bone and veins. The purpose of this study was to evaluate whether arterial visualization in CTPa is superior to standard CTA, which would eliminate the need for an additional CTA scan to assess arterial diseases and therefore reduce radiation dose.

MATERIALS AND METHODS

In this study, we included 24 patients with subarachnoid hemorrhage for whom CTA and CTP were available. Arterial quality and presence of superimposed veins and bone in CTPa were compared with CTA and scored by 2 radiologists by using a VAS (0%-100%). Average VAS scores were determined and VAS scores per patient were converted to a 10-point NRS. Arterial visualization was considered to be improved when the highest rate (NRS 10, VAS > 90%) was scored for arterial quality, and the lowest rate (NRS 1, VAS < 10%), for the presence of superimposed veins and bone. A sign test with continuity correction was used to test whether the number of cases with these rates was significant.

RESULTS

Average VAS scores in the proximal area were 94% (arterial quality), 4% (presence of bone), and 7% (presence of veins). In this area, the sign test showed that a significant number of cases scored NRS 10 for arterial quality (P < .02) and NRS 1 for the presence of superimposed veins and bone (P < .01).

CONCLUSIONS

Cerebral CTPa shows improved arterial visualization in the proximal area compared with CTA, with similar arterial quality but no superimposed bone and veins.

Bone subtraction CTA for transcranial arteries: intra-individual comparison with standard CTA without bone subtraction and TOF-MRA

AIM

To evaluate the impact of bone subtraction computed tomography angiography (BS-CTA) for the assessment of transcranial arteries in comparison with standard CTA (S-CTA) without bone removal and time-of-flight magnetic resonance angiography (TOF-MRA).

MATERIALS AND METHODS

Cranial unenhanced CT and S-CTA were performed in 53 patients with suspected cerebrovascular disease. BS-CTA datasets were reconstructed from the S-CTA and unenhanced CT source images. TOF-MRA was performed within 24h after CTA on a 1.5 T MRI system. Two radiologists, in consensus, evaluated the segments of the internal carotid artery (C2-C7), the vertebral artery (V4), and the basilar artery for the degree of stenosis. A five-step scale (0-49, 50-69, 70-89, 90-99% and occlusion) for the degree of stenosis was applied for all segments. Wilcoxon's signed rank test was used for statistical analysis.

RESULTS

Seven hundred and fifty vessel segments (ICA:636, VA:106, BA:53) were analysed. The degree of stenosis on S-CTA was consistent with TOF-MRA in all segments. BS-CTA showed a trend towards higher stenosis scores in cases of calcified plaques compared to S-CTA (p=0.11) and TOF-MRA (p=0.09), which was not statistically significant. In transcranial segments, BS-CTA revealed equivalent scores compared to S-CTA and TOF-MRA (p=0.25; p=0.20).

CONCLUSION

BS-CTA produced similar results to TOF-MRA and S-CTA and can be applied as a non-invasive imaging method for the transcranial arteries. However, BS-CTA shows a trend towards overestimation of the degree of stenosis.

Dual-energy CTA with bone removal for transcranial arteries: intraindividual comparison with standard CTA without bone removal and TOF-MRA

RATIONALE AND OBJECTIVES

Dual-source computed tomography enables bone removal on computed tomographic angiographic data on the basis of simultaneous dual-energy (DE) acquisition. The aim of this study was to evaluate the impact of this technique for the assessment of transcranial arteries. Therefore, the degree of stenosis of the transcranial arteries on DE computed tomographic angiography (CTA) with bone removal was compared to those on standard CTA and time-of-flight (TOF) magnetic resonance angiography (MRA).

MATERIALS AND METHODS

DE-CTA was performed using a dual-source computed tomographic scanner in 50 patients with suspected cerebrovascular disease. From the source images on DE-CTA, data sets with and without bone removal were reconstructed. TOF-MRA was performed on a 1.5-T scanner. Two blinded radiologists evaluated the segments of the internal carotid artery (C2-C7), the vertebral artery (V4), and the basilar artery for degree of stenosis. A five-step scale (0%-49%, 50%-69%, 70%-89%, 90%-99%, and 100% [occlusion]) for degree of stenosis was applied. Wilcoxon's signed-rank test was used for statistical analysis.

RESULTS

The degrees of stenosis on standard CTA were consistent with those on TOF-MRA in all segments. In contrast, DE-CTA showed significantly higher degrees of stenosis compared to standard CTA and TOF-MRA in both C2 segments (P < .001). In addition, DE-CTA revealed a significantly higher degree of stenosis compared to standard CTA and TOF-MRA in the left C4 segment (P < .01 and P < .005, respectively). All other segments showed no significant differences of stenosis among TOF-MRA, DE-CTA, and standard CTA.

CONCLUSIONS

Compared to TOF-MRA, standard CTA showed similar results. In contrast, DE-CTA revealed significant overestimation of stenosis for segments with close relations to bony structures as well as in calcified stenosis. Consequently, such findings on DE-CTA require confirmation with standard CTA or MRA to eliminate false-positive results.

Interobserver variability in the detection of cerebral venous thrombosis using CT venography with matched mask bone elimination

OBJECTIVES

Computed tomography venography (CTV) has proven to be a reliable imaging method in the evaluation of cerebral venous thrombosis with good correlation to magnetic resonance (MR) imaging and digital subtraction angiography (DSA). It is fast and widely accessible, especially in the emergency setting. For better visualization of vascular structures bone is often removed from the images. The purpose of this study was to evaluate the quality of a fully automatic bone removal method, matched mask bone elimination (MMBE), and to assess the interobserver variability of the CTV technique.

PATIENTS AND METHODS

Fifty patients with clinical suspicion of cerebral venous thrombosis underwent multislice CTV with MMBE post-processing. Axial source images and maximum intensity projections were retrospectively evaluated by two neuroradiologists for quality of bone removal and for the presence or absence of thrombosis in nine dural sinuses and five deep cerebral veins. A per sinus/vein and a per patient analysis (thrombosis in at least one sinus or vein) was performed and interobserver agreement was assessed.

RESULTS

Both observers considered bone removal good in all patients (100%). Interobserver agreement per patient was excellent (kappa=0.83), with a full agreement in 47 of 50 patients (94%). The interobserver agreement per sinus or vein was good (kappa=0.76), with a full agreement in 679 of 700 sinuses or veins (97%).

CONCLUSION

CTV aided with MMBE is a robust technique for visualization of the intracranial venous circulation, removing bone effectively. CTV has high interobserver agreement for presence or absence of cerebral venous thrombosis.

Cranial computed tomography angiography with automated bone subtraction: a feasibility study

OBJECTIVES

Computed tomography angiography (CTA) is becoming an increasingly accepted noninvasive alternative to catheter angiography. To display continuous vessel contours without superimposed bone in a similar manner, postprocessing of the CTA data is necessary. Threshold-based techniques often fail in regions of close vessel-bone contact, which frequently requires user interaction to optimize the results. This may be laborious and time consuming. The aim of this study was to assess the feasibility of a fully automated algorithm for bone subtraction in cranial CT angiography.

MATERIALS AND METHODS

Forty-nine patients underwent cranial CT angiography on 64 slice CT systems. Two scans were performed, one before (mask) and one after (CTA) contrast agent administration. Images were processed with commercially available subtraction software. Two examiners rated the success of overall bone removal and image quality of different vessel segments (n = 34) with a 4-point scale (1 = poor; 4 = excellent); original CTA data served as the reference.

RESULTS

Subtraction was performed successfully in all cases, overall subtraction quality was high (82% of cases were rated good or excellent). Only 50 of 1666 arterial segments (3%) were rated nondiagnostic. No relevant artificial stenoses of the internal carotid artery (ICA) or vertebral artery along their way through the skull base were detected when comparing CTA source images to bone subtraction computed tomography angiography (BSCTA) images.

CONCLUSIONS

Automatic subtraction provides diagnostic image quality for 3D visualization of intracranial vessels, free from over projecting bone in a fully automatic way. Aneurysms can be evaluated from all angles, and ICA stenoses at the skull base were easily visualized.