Dose reduction in cone-beam CT scanning for intracranial stent deployment before coil embolization of intracranial wide-neck aneurysms

Optimising image quality in intravenous cerebral cone beam computed tomography

INTRODUCTION

The efficacy of intravenous cerebral Cone Beam Computed Tomography (IV CBCT) is well established; however, image quality has only ever been authenticated by subjective evaluation. The aim of this study was to quantify the factors pertinent to achieving consistent and optimal image quality when performing IV CBCT.

METHODS

Between 1 March 2021 and 30 October 2022, 79 patients received IV CBCT. These candidates were divided into three main acquisition field size categories (22/32, 42 and 48 cm) according to the clinical indication. The images were analysed using both a quantitative assessment and a subjective evaluation. Here, a comparison of Hounsfield units (HUs), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and noise index was conducted for each study and compared relative to the acquisition field size. The subjective analysis was performed in a non-blinded fashion where the diagnostic value (DV) of the exam was determined according to a graded scale. A phantom analysis for each of the acquisition field sizes was conducted and modulation transfer function (MTF) graphed.

RESULTS

Significantly higher HU, SNR, CNR and lower noise indices were achieved with the 42-cm protocol than the 22/32 and 48-cm protocols. Here a greater DV was also reported. The MTF demonstrates marginally improved spatial resolution for the 22-cm protocol, but this is near equivocal for the 32-, 42 and 48-cm protocols.

CONCLUSION

The use of larger acquisition field sizes provides improved image quality when performing IV CBCT as an alternative to intra-arterial (IA) CBCT.

A Systematic Review of Intracranial Aneurysms in the Pregnant Patient - A Clinical Conundrum

Hemodynamic and hormonal changes during pregnancy can increase rates of formation, growth, and rupture of intracranial aneurysms (IA), and the increased incidence of subarachnoid hemorrhage (SA) in pregnant patients represents a risk to both mother and fetus. Despite this, management and treatment guidelines have not been defined for this patient population. In most instances, treatment decisions are made on a case-by-case basis with varying degrees of input from subspecialists. Important considerations, such as aneurysm location, morphology, size, growth pattern, and patient characteristics have not been presented in a management algorithm in the context of the pregnant patient. Given limited and controversial literature describing management of IAs in pregnant patients, we performed a systematic literature review. We then describe our multidisciplinary team approach and provide analysis of existing literature to provide guidelines for the management of the pregnant patient with an IA. A systematic review was undertaken to identify studies describing the management of IAs in the pregnant patient using the PubMed database. Overall maternal and fetal morbidity and mortality rates were determined. Data was analyzed for 1537 patients, including 1115 (73%) pregnant with ruptured intracranial aneurysms. In most cases, these aneurysms were managed conservatively (77%; 781/1013); however, when treatment was provided, surgical clipping was the most common modality (15%; 149/1013). Overall maternal outcomes were reported for 934 cases with morbidity and mortality rates of 5% (42/934) and 21% (194/934), respectively. Overall fetal outcomes were reported for 114 cases with morbidity and mortality rates of 10% (12/119) and 8% (9/119), respectively. Pregnancy-associated physiological changes likely elevate the risk of intracranial aneurysm formation, growth, and rupture. Treatment for aneurysms and SAs is safe and effective during pregnancy when risks are properly mitigated. Due to the complexity of care, such patients should be treated using a collaborative, interdisciplinary approach by a multidisciplinary team.

A new definition for wide-necked cerebral aneurysms

Background

Endovascular management of wide-necked aneurysms often requires assisted-techniques with adjunctive devices. Wide-necked aneurysm can be defined with a dome-to-neck ratio or aspect ratio; however, clinical definitions of wide-necked aneurysms vary. This study aimed to determine the most useful definition of wide-necked aneurysm to predict the need for an adjunctive device.

Methods

Among 552 cases of aneurysms, 343 (62.1%) and 209 (37.9%) cases of unruptured and ruptured aneurysms, respectively, were treated in a single institution. For each aneurysm, the (1) dome-to-neck ratio, (2) aspect ratio, and (3) K-ratio (defined as [dome height+maximum dome width]/[2×maximum neck width]) were measured. We statistically analyzed patient data to determine which of the three ratios was most predictive of the need for adjunctive devices.

Results

Among 552 cases of aneurysms, 277 (50.2%) and 275 (49.8%) cases were treated with and without adjunctive techniques, respectively. The mean dome-to-neck ratio, aspect ratio, and K-ratio were 1.17±0.39, 1.58±0.61, and 1.37±0.47, respectively. The K-ratio was the strongest predictor of the use of adjunctive devices (P<0.001), and 1.3 was the most appropriate K-ratio cut-off value (sensitivity, 72.9%; specificity, 63.6%).

Conclusions

K-ratio was the most useful predictor of the need for adjunctive devices in the treatment of endovascular aneurysms. These results suggest that the K-ratio may be used to define wide-necked aneurysms requiring complicated management via adjunctive devices.

Usefulness of Cone Beam Intra-Arterial CTA for Evaluation of Flow Diverters: A Practical Approach for Daily Use

Cone beam computed tomography (CBCT), initially used for evaluation of intraprocedural complications such as hemorrhage, has evolved to provide details of implanted devices such as flow diverters. The study aim is to present our experience in using CBCT with intra-arterial injection and provide a step-by-step approach for postprocessing in a practical protocol for daily use. IRB approval was obtained, and the neurointerventional database was retrospectively reviewed from July 2012 to June 2017. Patients who underwent cone beam intra-arterial CT angiography for evaluation of implanted flow diverter devices were reviewed. Patient demographics, aneurysm location (internal carotid artery [ICA]-cavernous, ICA-paraclinoid, and ICA-distal; middle cerebral artery [MCA], anterior cerebral artery [ACA]-acom, ACA-pericallosal, vertebral artery [VA]), type (saccular, dissecting fusiform, or blister) and size, device, injection technique (contrast dilution, rate, and volume), and reconstruction protocol were recorded. Acquired images were postprocessed using a Philips Xtravision workstation. Eighty patients (63 women and 17 men) met the inclusion criteria of our study. Age range was 25-80 years old. Treated aneurysms were located in the ICA-paraclinoid in 48 cases (60%), ICA-distal in 12 cases, ICA-cavernous in 8 cases, MCA in 4 cases, VA in 4 cases, ACA-acom in 2 cases, ACA-pericallosal in 2 cases; 69 were saccular, 8 fusiform, and 3 ruptured blister aneurysms. There were 52 small, 20 large, and 8 giant aneurysms. Pipeline (Medtronic, MN, USA) was the predominant device used in 77 procedures. Two injection techniques were used: 2.5 mL/s for a total volume of 55 mL with a 2-s imaging delay or 3 mL/s for a total volume of 70 mL with a 3-s imaging delay; contrast (Ioxilan 300 mgI/mL) dilution was 10-20% in all cases. The device's landing zones, conformability, presence of deformities, and wall apposition were successfully visualized in all cases. Metal artifact reduction program was applied in 9 coiled aneurysms, and this was satisfactory as well.

Quantitative Analysis of Conebeam CT for Delineating Stents in Stent-Assisted Coil Embolization

BACKGROUND AND PURPOSE

Innovative techniques and device-related advances have improved the outcomes of neuroendovascular treatment. 3D imaging has previously used 2 × 2 binning, but 1 × 1 binning has recently been made available. The aim of this study was to evaluate the quantitative ability of conebeam CT for stent delineation and to investigate its effectiveness in the clinical environment.

MATERIALS AND METHODS

Four acquisition groups of 3D MIP images acquired using conebeam CT with varying conditions (acquisition time, 10 or 20 seconds and binning, 1 × 1 or 2 × 2) were compared. Two methods of analysis were performed, a phantom study and an analysis of 28 randomly selected patients. The phantom study assessed the contrast-to-noise ratio and full width at half maximum values in conebeam CT images of intracranial stent struts. In the clinical subjects, we assessed contrast-to-noise ratio, full width at half maximum, and dose-area product.

RESULTS

In the phantom study, the contrast-to-noise ratio was not considerably different between 10- and 20-second acquisition times at equivalent binning settings. Additionally, the contrast-to-noise ratio at equivalent acquisition times did not differ considerably by binning setting. For the full width at half maximum results, equivalent acquisition times differed significantly by binning setting. In the clinical analyses, the 10-second/1 × 1 group (versus 20 second/2 × 2) showed a higher contrast-to-noise ratio (P < .05) and a dose-area product reduced by approximately 70% (P < .05), but the difference in full width at half maximum was not significant (P = .20).

CONCLUSIONS

For stent-assisted coil embolization, quantitative assessment of conebeam CT showed that 10 second/1 × 1 was equivalent to 20 second/2 × 2 for imaging deployed intracranial stents. Furthermore, the 10-second/1 × 1 settings resulted in a much smaller DAP.