Quantitative evaluation of the effects of flow diverter treatment on aneurysm hemodynamics using time-resolved rotational angiography.

BACKGROUND: There have been immense advancements in the hardware and software of digital subtraction angiography systems over the last several years. These advancements continue to make progress toward the goals of offering better visualization and reducing radiation exposure. A newer advancement in this arena is presenting three-dimension data over time resulting in four-dimensional-digital subtracted angiography visualization. We have evaluated these protocols related to the evaluation of the treatment of intracranial aneurysms with pipeline flow diversion. METHODS: Four-dimensional-digital subtracted angiography imaging was acquired on an Artis Q Biplane angiographic system (Siemens Healthcare AG, Forchheim, Germany). A six second four-dimensional-digital subtracted angiography protocol was performed pre and post flow diverter placement. Pre and post reconstructed images were sent through a dedicated prototype research workstation (Syngo X-Workplace; Siemens Healthineers AG) for further flow evaluation. RESULTS: The treatment of an aneurysm with flow diversion led to a filling delay of 0.278 ± 0.422 s inside the aneurysms, whereas distal to the aneurysms the filling of the vessel segment occurred earlier post procedural (negative filling delay of -0.15 ± 0.31 s. The flow ratio inside the aneurysm decreased to 63.6 ± 23% of its pre-treatment value and distal to the aneurysm the flow remained substantially the same (flow ratio: 95.6 ± 0.29%). Data showed a relative filling delay of the aneurysm normalized to the distal vessel of 0.43 ± 0.36 s. The relative flow ratio of the aneurysm in comparison to the distal parent vessel was 72.2 ± 31%. CONCLUSIONS: Analysis of a four-dimensional-digital subtracted angiography acquisition allows assessment of the effects of flow diversion treatment on aneurysm hemodynamic parameters and shows a significant decrease in flow inside the aneurysm compared to the parent vessel distal to the aneurysm.

Endoscopic Endonasal Treatment of a Sinonasal Vascular Neoplasm in the Postnatal Period: Case Report and Review of Literature.

OBJECTIVES: Congenital vascular lesions commonly present in the head and neck, and most are managed conservatively. Location and rapid growth, however, may necessitate surgical intervention. Endoscopic endonasal surgery (EES) in the pediatric population has emerged as a viable option in treating sinonasal and skull base lesions. Utilizing these techniques in newborns carries unique challenges. The objective of this report is to describe the successful use of direct intralesional embolization followed by endoscopic endonasal resection of a venous malformation in a postnatal patient. METHODS: We reviewed the case reported and reviewed the pertinent literature. RESULTS: A 6-week-old infant was found to have a large right-sided sinonasal lesion confirmed as a venous malformation. Rapid growth, impending orbital compromise, and potential long-term craniofacial abnormalities demanded the need for urgent surgical intervention. Risk of bleeding was mitigated with direct intralesional embolization. Immediately afterward, the patient underwent endoscopic endonasal resection of the lesion. EES in the very young presents multiple challenges both anatomically and behaviorally. A multidisciplinary approach lead to a successful outcome. CONCLUSION: We report a case of a 6-week-old infant, the youngest reported patient to the authors' knowledge, who successfully underwent direct intralesional embolization followed by endoscopic endonasal resection of a sinonasal vascular malformation. This report highlights the challenges of this technique in the very young and demonstrates it as a viable treatment strategy for sinonasal vascular anomalies in this population.

Trimodal embolization of juvenile nasopharyngeal angiofibroma with intracranial extension.

OBJECTIVES/PURPOSE: 1. Understand three different techniques for embolization of juvenile nasal angiofibroma (JNA) and assess their combined efficacy. 2. Perform successful endoscopic intralesional embolization of highly vascular sinonasal neoplasms. METHODS: In this study, we present the case of a 10-year-old male patient diagnosed with juvenile nasal angiofibroma (JNA) who successfully underwent trimodal embolization and resection at a tertiary academic medical center after failed coil embolization in his home country. We examine the clinical details of the case and a review of pertinent literature. RESULTS: Preoperative embolization is common in the treatment of JNA, but there is little consensus as to the proper timeframe and techniques utilized. In our case, preoperative imaging revealed a vascular tumor with intracranial extension consistent with UPMC Stage V JNA. Diagnostic angiogram revealed significant arborization from the internal and external carotid systems. A trimodal embolization technique, utilizing transarterial, percutaneous, and direct endoscopic intralesional injection of n-Butyl Cyanoacrylate (n-BCA) was performed. A two-staged endoscopic and open resection was subsequently performed one week later with minimal blood loss. In our case, combining intralesional embolization with traditional transarterial techniques resulted in an improved operative field and a successful clinical result. CONCLUSION: Embolization of highly vascular sinonasal tumors with n-BCA is not limited to endovascular techniques, but can be safely combined with percutaneous and endoscopic intralesional embolization up to one week prior to surgical resection.

Modeling, characterizing, and accommodating static birefringence in circular and linear dichroism spectroscopy.

Nearly all circular dichroism (CD) and linear dichroism (LD) spectrometers use a photoelastic modulator (PEM) in which an optical element is stressed using a high-tension voltage (HT) signal to induce birefringence. The birefringence consequently produces a phase difference between perpendicular polarization states of light passing through the PEM that is appropriate to CD or LD measurements. However, even without external stress (i.e., at zero HT) the PEM exhibits an inherent static birefringence. This article discusses the characterization of the static birefringence inherent to a PEM and its effect on the measurement of CD and LD, as well as the development and implementation of a novel model that accommodates for the presence of static birefringence. The model is validated with CD and LD experiments using purely chiral or linearly structured molecules (camphorsulfonic acid and chrysazin).

Novel technique for improvement in calibration of the photoelastic modulator in circular and linear dichroism spectroscopy.

Both the voltage-induced and the inherent (static) birefringence of a photoelastic modulator (PEM) affect the phase difference between orthogonal components of light passing through the PEM. This phase difference determines the polarization state of the light and is essential for determining true circular and linear dichroism (CD and LD, respectively) spectroscopy. Presented here are a more complete theoretical model of CD and LD and a new technique to determine the phase difference and static birefringence of a PEM in CD and LD. The intensity of the light for various configurations of the analyzer is interpreted (by using Mueller matrices and Stokes parameters) to calibrate the voltage-induced phase difference and to characterize the static birefringence in the photoelastic modulator. The effects of the static birefringence as well as intermediate polarization states (between left- and right-circularly polarized light) on LD and CD are characterized. Appropriate adjustments to the voltage applied to the PEM in order to mitigate these effects are discussed. It is expected that the techniques presented here will have a broad impact on the calibration of CD and LD spectrometers.

Noise characterization in circular dichroism spectroscopy.

Circular dichroism (CD), defined as the difference in absorption between left and right circularly polarized light, is used to spectroscopically study the structures of chiral materials. In this article, various methodologies are presented for characterizing the performance of CD spectrometers to determine (1) experimental conditions for optimal data collection, (2) noise characteristics dependent on machine parameters, (3) the relative significance of spectral data as a function of detector gain, and (4) stray light and dark current as a function of wavelength. The results of case studies of two commercial CD spectrometers (specifically, Jasco J810 and J815) are described. The analyses show that the variation of CD signal is Poisson distributed and hence can be considered shot noise. Also, optimum scan parameters are established and a weighting function of CD data significance is produced so that wavelength-dependent gain (as determined by the high tension, HT, voltage applied to the photomultiplier tube, PMT, detector) can be accommodated. Lastly, the amount of stray light and dark current for the photomultiplier tube is determined. Though specific to the Jasco CD spectrometers characterized in this study, it is expected that all CD spectrometers exhibit similar behavior and the methodology described here can be usefully applied to characterize CD spectrometers independent of manufacturer.