Modern optical and spectral technologies represent powerful approaches for a molecular characterization of tissues enabling delineating pathological tissues but also a label-free grading and staging of tumors in terms of computer-assisted histopathology. First, currently used tools for intraoperative tumor assessment are described. Next, the requirements for intraoperative tissue visualization from a medical and optical point of view are specified. Then, optical and spectral techniques are introduced that are already approved or close to being used in standard clinical practice for ex vivo and in vivo monitoring, and proof-of concept studies utilizing linear and nonlinear spectroscopy and imaging modalities are presented. Combining several spectroscopic mechanisms in multi-contrast approaches constitutes further advances. Modern artificial intelligence and deep learning concepts have emerged to analyze spectroscopic and imaging datasets and have contributed to the progress of each technique. Finally, an outlook for opportunities and prospects of clinical translation is given.

Background: The aim of surgery for skull base meningiomas is maximal resection with minimal damage to the involved cranial nerves and cerebral vessels; thus, implementation of technologies for improved orientation in the surgical field, such as neuronavigation and augmented reality (AR), is of interest. Methods: Included in the study were 39 consecutive patients (13 male, 26 female, mean age 64.08 ± 13.5 years) who underwent surgery for skull base meningiomas using microscope-based AR and automatic patient registration using intraoperative computed tomography (iCT). Results: Most common were olfactory meningiomas (6), cavernous sinus (6) and clinoidal (6) meningiomas, meningiomas of the medial (5) and lateral (5) sphenoid wing and meningiomas of the sphenoidal plane (5), followed by suprasellar (4), falcine (1) and middle fossa (1) meningiomas. There were 26 patients (66.6%) who underwent gross total resection (GTR) of the meningioma. Automatic registration applying iCT resulted in high accuracy (target registration error, 0.82 ± 0.37 mm). The effective radiation dose of the registration iCT scans was 0.58 ± 1.05 mSv. AR facilitated orientation in the resection of skull base meningiomas with encasement of cerebral vessels and compression of the optic chiasm, as well as in reoperations, increasing surgeon comfort. No injuries to critical neurovascular structures occurred. Out of 35 patients who lived to follow-up, 33 could ambulate at their last presentation. Conclusion: A microscope-based AR facilitates surgical orientation for resection of skull base meningiomas. Registration accuracy is very high using automatic registration with intraoperative imaging.

Multiple factors can affect the accuracy of neuronavigation, that is a relevant issue, particularly for frameless stereotactic procedures, where precision and optimal image-guidance is crucial for the surgical performance, workflow, and outcome. To investigate the impact of AIRO Mobile Computer Tomography in frameless stereotactic approaches. A retrospective study on 12 patients was performed. All the procedures were deployed using a frameless stereotactic technique, both for the collection of biopsy pathological specimens for diagnosis and insertion of drainage in the treatment of intracranial cystic lesions. Twelve patients (eight males, four females) underwent the frameless stereotactic procedure. Mean age at surgery was 55 (±5 SE). The mean volume of the lesion was 23.85 cm³ (±3.13). Six diagnostic biopsies and six cyst drainages were performed. The mean trajectory length was 75.9 ± 11.8 mm. Three posterior fossa lesions (27%) were approached through a retro-sigmoidal burr-hole. A craniotomy for draining a haematoma was performed after detection with AIRO-CT. No permanent neurological dysfunction, in-hospital or 30-day mortality were recorded. The AIRO-CT resulted feasible with a potential utility for stereotactic procedures. We showed how it could grant the efficacy of the stereotactic procedures reducing some technical and physical sources of inaccuracy, also enhancing safety and allowing prompt detection and management of intraoperative complications.

Background: The aim of our study was to evaluate the additional benefit of intraoperative computed tomography (iCT), intraoperative computed tomography angiography (iCTA), and intraoperative computed tomography perfusion (iCTP) in the intraoperative detection of impending ischemia to established methods (indocyanine green videoangiography (ICGVA), microDoppler, intraoperative neuromonitoring (IONM)) for initiating timely therapeutic measures. Methods: Patients with primary aneurysms of the anterior circulation between October 2016 and December 2019 were included. Data of iCT modalities compared to other techniques (ICGVA, microDoppler, IONM) was recorded with emphasis on resulting operative conclusions leading to inspection of clip position, repositioning, or immediate initiation of conservative treatment strategies. Additional variables analyzed included patient demographics, aneurysm-specific characteristics, and clinical outcome. Results: Of 194 consecutive patients, 93 patients with 100 aneurysms received iCT imaging. While IONM and ICGVA were normal, an altered vessel patency in iCTA was detected in 5 (5.4%) and a mismatch in iCTP in 7 patients (7.5%). Repositioning was considered appropriate in 2 patients (2.2%), where immediate improvement in iCTP could be documented. In a further 5 cases (5.4%), intensified conservative therapy was immediately initiated treating the reduced CBP as clip repositioning was not considered causal. In terms of clinical outcome at last FU, mRS0 was achieved in 85 (91.4%) and mRS1-2 in 7 (7.5%) and remained mRS4 in one patient with SAH (1.1%). Conclusions: Especially iCTP can reveal signs of impending ischemia in selected cases and enable the surgeon to promptly initiate therapeutic measures such as clip repositioning or intraoperative onset of maximum conservative treatment, while established tools might fail to detect those intraoperative pathologic changes.

This article discusses intraoperative imaging techniques used during high-grade glioma surgery. Gliomas can be difficult to differentiate from surrounding tissue during surgery. Intraoperative imaging helps to alleviate problems encountered during glioma surgery, such as brain shift and residual tumor. There are a variety of modalities available all of which aim to give the surgeon more information, address brain shift, identify residual tumor, and increase the extent of surgical resection. The article starts with a brief introduction followed by a review of with the latest advances in intraoperative ultrasound, intraoperative MRI, and intraoperative computed tomography.

Maximal safe resection can improve patient outcomes for a variety of brain tumor types including low- and high-grade gliomas, pituitary adenomas, and other pathologies. Numerous intraoperative adjuncts exist to guide surgeons with maximizing extent of resection. Three distinct strategies exist including: 1) surgical navigation; 2) intraoperative imaging; and 3) tumor fluorescence. Surgical navigation involves registration of high-resolution three-dimensional imaging to the patient's cranial surface anatomy, allowing real-time localization of tumor and brain structures. Intraoperative imaging devices like intraoperative magnetic resonance imaging (iMRI), intraoperative computed tomography (iCT), 3-D fluoroscopy, and intraoperative ultrasonography (iUS) allow near real time visualization to assess the extent of resection. Intraoperative fluorescence via intravenous fluorescein or oral 5-aminolevulinic acid (5-ALA) causes brain tumors to "light up", which can be viewed through surgical optics using selective filters and specific wavelength light sources. A general overview, as well as implementation and utilization of some of these image guidance strategies at Washington University and by Siteman Cancer Center neurosurgeons at Barnes Jewish Hospital, is discussed in this review.

Introducción: La cirugía de los tumores cerebrales se ha implementado en los últimos años con nuevas técnicas de imagen intraoperatoria, que tratan de mejorar la resección tumoral, aunque conllevan un aumento de recursos. Con el fin de hacer una actualización de este tema, se ha elaborado este manuscrito desde el grupo de tumores de la Sociedad Española de Neurocirugía. Material y métodos Se ha propuesto a expertos en el uso de cada una de las técnicas intraoperatorias más empleadas en la cirugía de los tumores cerebrales, la descripción de la técnica y una breve revisión de la literatura. Se describirán indicaciones de uso, sus ventajas e inconvenientes basados en la experiencia clínica y en lo publicado en la literatura. Resultados: La técnica de imagen intraoperatoria más consistente sería la resonancia de bajo y alto campo, pero a su vez es la que supone un mayor gasto de recursos. La ecografía intraoperatoria navegada es portátil y tiene un menor coste, aunque discrimina peor los tumores de alto grado y es observador-dependiente. Las técnicas de fluorescencia más empleadas son el 5-aminolevulínico para gliomas de alto grado y la fluoresceína, de utilidad en lesiones que rompen la barrera hematoencefálica. Por último, la TAC intraoperatoria es la más versátil en el quirófano de neurocirugía, pero tiene menos indicaciones en la cirugía neurooncológica Conclusiones: Las técnicas de imagen intraoperatoria se emplean cada vez con más frecuencia en la cirugía de los tumores cerebrales, y el neurocirujano debe valorar su posible uso en función de sus recursos y las necesidades de cada paciente. Introduction: New intraoperative imaging techniques, which aim to improve tumour resection, have been implemented in recent years in brain tumour surgery, although they lead to an increase in resources. In order to carry out an update on this topic, this manuscript has been drafted by a group from the Sociedad Española de Neurocirugía (Spanish Society of Neurosurgery). Material and methods Experts in the use of each one of the most-used intraoperative techniques in brain tumour surgery were presented with a description of the technique and a brief review of the literature. Indications for use, their advantages and disadvantages based on clinical experience and on what is published in the literature will be described. Results: The most robust intraoperative imaging technique appears to be low- and high-field magnetic resonance imaging, but this is the technique which results in the greatest expenditure. Intraoperative ultrasound navigation is portable and less expensive, but it provides poorer differentiation of high-grade tumours and is observer-dependent. The most-used fluorescence techniques are 5-aminolevulinic acid for high-grade gliomas and fluorescein, useful in lesions which rupture the blood-brain barrier. Last of all, intraoperative CT is more versatile in the neurosurgery operating theatre, but it has fewer indications in neuro-oncology surgery. Conclusions: Intraoperative imaging techniques are used with increasingly greater frequency in brain tumour surgery, and the neurosurgeon should assess their possible use depending on their resources and the needs of each patient.

Intraoperative computer tomography (iCT) and advanced image fusion algorithms could improve the management of brainshift and the navigation accuracy. To evaluate the performance of an iCT-based fusion algorithm using clinical data. Ten patients with brain tumors were enrolled; preoperative MRI was acquired. The iCT was applied at the end of microsurgical resection. Elastic image fusion of the preoperative MRI to iCT data was performed by deformable fusion employing a biomechanical simulation based on a finite element model. Fusion accuracy was evaluated: the target registration error (TRE, mm) was measured for rigid and elastic fusion (R_f and E_f) and anatomical landmark pairs were divided into test and control structures according to distinct involvement by the brainshift. Intraoperative points describing the stereotactic position of the brain were also acquired and a qualitative evaluation of the adaptive morphing of the preoperative MRI was performed by 5 observers. The mean TRE for control and test structures with R_f was 1.81 ± 1.52 and 5.53 ± 2.46 mm, respectively. No significant change was observed applying E_f to control structures; the test structures showed reduced TRE values of 3.34 ± 2.10 mm after E_f (P< .001). A 32% average gain (range 9%-54%) in accuracy of image registration was recorded. The morphed MRI showed robust matching with iCT scans and intraoperative stereotactic points. The evaluated method increased the registration accuracy of preoperative MRI and iCT data. The iCT-based non-linear morphing of the preoperative MRI can potentially enhance the consistency of neuronavigation intraoperatively.

Surgery has long been established as the first-line treatment for the majority of symptomatic and enlarging meningiomas, and evidence for its success is derived from retrospective case series. Despite surgical resection, a subset of meningiomas display aggressive behavior with early recurrences that are difficult to treat. The decision to radically resect meningiomas and involved structures is balanced against the risk for neurological injury in patients. Radiation therapy has largely been used as a complementary and safe therapeutic strategy in meningiomas with evidence primarily stemming from retrospective, single-institution reports. Two of the first cooperative group studies (RTOG 0539 and EORTC 22042) evaluating the outcomes of adjuvant radiation therapy in higher-risk meningiomas have shown promising preliminary results. Historically, systemic therapy has resulted in disappointing results in meningiomas. However, several clinical trials are under way evaluating the efficacy of chemotherapies, such as trabectedin, and novel molecular agents targeting Smoothened, AKT1, and focal adhesion kinase in patients with recurrent meningiomas.

Intraoperative CT allows highly reliable navigation registration with low radiation exposure.

Intraoperative brain shift decreases the accuracy of neuronavigation systems based on preoperative images. In this paper, this problem is addressed by calculating an estimation of brain shift which can be employed to update the preoperative brain images. Therefore, the precision of navigation can be improved. In this regard, a brain shift estimation method is proposed using an atlas of brain deformations and constrained Kalman filter (ACKF). In addition, it is proven that the obtained ACKF estimation is the best unbiased minimax estimation when the risk function is the estimation error variance. Furthermore, a comparison is performed between the ACKF and two existing methods, namely, CKF and atlas-based method. The comparison demonstrates that the ACKF results in a more accurate estimation and needs less computation time. Finally, the supremacy of the proposed ACKF method with respect to the CKF and atlas-based method is illustrated through simulation.