Feasibility of postoperative diffusion-weighted imaging to assess representations of spinal cord microstructure in cervical spondylotic myelopathy.

OBJECTIVE: Diffusion basis spectrum imaging (DBSI) has shown promise in evaluating cervical spinal cord structural changes in patients with cervical spondylotic myelopathy (CSM). DBSI may also be valuable in the postoperative setting by serially tracking spinal cord microstructural changes following decompressive cervical spine surgery. Currently, there is a paucity of studies investigating this topic, likely because of challenges in resolving signal distortions from spinal instrumentation. Therefore, the objective of this study was to assess the feasibility of DBSI metrics extracted from the C3 spinal level to evaluate CSM patients postoperatively. METHODS: Fifty CSM patients and 20 healthy controls were enrolled in a single-center prospective study between 2018 and 2020. All patients and healthy controls underwent preoperative and postoperative diffusion-weighted MRI (dMRI) at a 2-year follow-up. All CSM patients underwent decompressive cervical surgery. The modified Japanese Orthopaedic Association (mJOA) score was used to categorize CSM patients as having mild, moderate, or severe myelopathy. DBSI metrics were extracted from the C3 spinal cord level to minimize image artifact and reduce partial volume effects. DBSI anisotropic tensors evaluated white matter tracts through fractional anisotropy, axial diffusivity, radial diffusivity, and fiber fraction. DBSI isotropic tensors assessed extra-axonal pathology through restricted and nonrestricted fractions. RESULTS: Of the 50 CSM patients, both baseline and postoperative dMR images with sufficient quality for analysis were obtained in 27 patients. These included 15 patients with mild CSM (mJOA scores 15-17), 7 with moderate CSM (scores 12-14), and 5 with severe CSM (scores 0-11), who were followed up for a mean of 23.5 (SD 4.1, range 11-31) months. All preoperative C3-level DBSI measures were significantly different between CSM patients and healthy controls (p < 0.05), except DBSI fractional anisotropy (p = 0.31). At the 2-year follow-up, the same significance pattern was found between CSM patients and healthy controls, except DBSI radial diffusivity was no longer statistically significant (p = 0.75). When assessing change (i.e., postoperative - preoperative values) in C3-level DBSI measures, CSM patients exhibited significant decreases in DBSI radial diffusivity (p = 0.02), suggesting improvement in myelin integrity (i.e., remyelination) at the 2-year follow-up. Among healthy controls, there was no significant difference in DBSI metrics over time. CONCLUSIONS: DBSI metrics derived from dMRI at the C3 spinal level can be used to provide meaningful insights into representations of the spinal cord microstructure of CSM patients at baseline and 2-year follow-up. DBSI may have the potential to characterize white matter tract recovery and inform outcomes following decompressive cervical surgery for CSM.

Perioperative imaging in patients treated with resection of brain metastases: a survey by the European Association of Neuro-Oncology (EANO) Youngsters committee.

BACKGROUND: Neurosurgical resection represents an important treatment option in the modern, multimodal therapy approach of brain metastases (BM). Guidelines for perioperative imaging exist for primary brain tumors to guide postsurgical treatment. Optimal perioperative imaging of BM patients is so far a matter of debate as no structured guidelines exist. METHODS: A comprehensive questionnaire about perioperative imaging was designed by the European Association of Neuro-Oncology (EANO) Youngsters Committee. The survey was distributed to physicians via the EANO network to perform a descriptive overview on the current habits and their variability on perioperative imaging. Chi square test was used for dichotomous variables. RESULTS: One hundred twenty physicians worldwide responded to the survey. MRI was the preferred preoperative imaging method (93.3%). Overall 106/120 (88.3%) physicians performed postsurgical imaging routinely including MRI alone (62/120 [51.7%]), postoperative CT (29/120 [24.2%]) and MRI + CT (15/120 [12.5%]). No correlation of postsurgical MRI utilization in academic vs. non-academic hospitals (58/89 [65.2%] vs. 19/31 [61.3%], p = 0.698) was found. Early postoperative MRI within ≤72 h after resection is obtained by 60.8% of the participants. The most frequent reason for postsurgical imaging was to evaluate the extent of tumor resection (73/120 [60.8%]). In case of residual tumor, 32/120 (26.7%) participants indicated to adjust radiotherapy, 34/120 (28.3%) to consider re-surgery to achieve complete resection and 8/120 (6.7%) to evaluate both. CONCLUSIONS: MRI was the preferred imaging method in the preoperative setting. In the postoperative course, imaging modalities and timing showed high variability. International guidelines for perioperative imaging with special focus on postoperative MRI to assess residual tumor are warranted to optimize standardized management and adjuvant treatment decisions for BM patients.

Early postoperative MRI after resection of brain metastases-complete tumour resection associated with prolonged survival.

BACKGROUND: This study aimed to investigate the incidence of residual tumour after resection of brain metastases using early postoperative magnetic resonance imaging (MRI) and the influence of residual tumour on overall patient survival. METHODS: Data from 72 consecutive adult patients undergoing surgery for cerebral metastases over an 18-month study period were retrospectively collected. Early postoperative MRI was used to determine the presence of postoperative residual tumour. Patients were divided into three groups according to the presence of tumour remnant on early postoperative MRI: "no residual tumour", "non-measurable residual tumour" and "measurable residual tumour". Survival analysis (mean estimate survival time) was performed using the Kaplan-Meier and log-rank (mantel cox) tests and compared between groups. Surgical reports were evaluated with regard to the surgeon statement about intraoperative extent of resection (EOR) and compared with the presence of tumour remnant found on the early postoperative MRI. RESULTS: Sixty-eight procedures were followed by early postoperative MRI. MRI verified the presence of "measurable residual tumour" following 15 procedures (22%). MRI confirmed complete resection in 57%. Gross total resection was described by the operating surgeon in 85% of the procedures. There was a significant difference in survival time after surgery between the group having no residual tumour on MRI and the group with measurable residual tumour (p = 0.025). This difference could not be explained by the differences in postoperative radiation therapy. The longest survival was found in patients with non-measurable and no residual tumour on early postoperative MRI, who also received postoperative radiotherapy. CONCLUSION: Residual tumour was seen on MRI after 22% of the procedures. The intraoperative assessment of EOR performed by the surgeon diverged from the early postoperative MRI in 40% of procedures. Correct assessment of residual tumour thus requires early postoperative MRI. Measurable residual tumour on early postoperative MRI was associated with shorter overall survival independent on postoperative radiotherapy.

Timing of postoperative magnetic resonance imaging (MRI) following glioma resection: Shattering the 72 hour window.

Extent of enhancing tumour resection is correlated with progression free survival following glioma surgery. Historically, a contrast enhanced MRI has been recommended within 72 hours following surgery to evaluate for residual disease. This theoretical window was established amidst conflicting evidence to avoid reactive enhancement. Recent studies with better designs and better imaging quality have sought to challenge this window with a more pragmatic method of evaluating residual disease.

Predictors for a further local in-brain progression after re-craniotomy of locally recurrent cerebral metastases.

Treatment of recurrent cerebral metastases is an emerging challenge due to the high local failure rate after surgery or radiosurgery and the improved prognosis of patients with malignancies. A total of 36 patients with 37 metastases who underwent surgery for a local in-brain progression of a cerebral metastasis after previous metastasectomy were retrospectively analyzed. Degree of surgical resection on an early postoperative MRI within 72 h after surgery was correlated with the local in-brain progression rate and overall survival. Complete surgical resection of locally recurrent cerebral metastases as confirmed by early postoperative MRI could only be achieved in 37.8%. Detection of residual tumor tissue on an early MRI following recurrent metastasis surgery correlated with further local in-brain progression when defining a significance level of p = 0.05 but not after Sidák or Bonferroni significance level correction for multiple testing: However, definite local tumor control could finally be achieved in 91.9% after adjuvant therapy. Overall survival after recurrent metastasectomy was significantly higher as predicted by diagnosis-specific graded prognostic assessment (12.9 ± 2.3 vs. 8.4 ± 0.7 months; p < 0.0001). However, our series involved a limited number of heterogeneous patients. A larger, prospective, and controlled study is required. Considering the adequate local tumor control achieved in the vast majority of patients, surgery of recurrent metastases may represent one option in a multi-modal treatment approach of patients suffering from locally recurrent cerebral metastases.

Pitfalls and pearls in MRI of the knee.

OBJECTIVE: The purpose of this article is to review the common pitfalls in MRI of the knee and pearls on how to avoid them. CONCLUSION: MRI of the knee is highly accurate in evaluation of internal derangements of the knee. However, a variety of potential pitfalls in interpretation of abnormalities related to the knee have been identified, particularly in evaluation of the menisci, ligaments, and articular cartilage.

Single brain metastases - prognostic factors and impact of residual tumor burden on overall survival.

Background: Brain metastases (BM) are a common and challenging issue, with their incidence on the rise due to advancements in systemic therapies and increased patient survival. Most patients present with single BM, some of them without any further extracranial metastasis (i.e., solitary BM). The significance of postoperative intracranial tumor volume in the treatment of singular and solitary BM is still debated. Objective: This study aimed to determine the impact of resection and postoperative tumor burden on overall survival (OS) in patients with single BM. Methods: Patients with surgically treated single BM between 04/2007-01/2020 were retrospectively included. Residual tumor burden (RTB) was determined by manual segmentation of early postoperative brain MRI (72 h). Survival analyses were performed using Kaplan-Meier estimates for univariate analysis and Cox regression proportional hazards model for multivariate analysis, using preoperative Karnofsky performance status scale (KPSS), age, sex, RTB, incomplete resection and singular/solitary BM as covariates. Results: 340 patients were included, median age 64 years (54-71). 119 patients (35%) had solitary BM, 221 (65%) singular BM. Complete resection (RTB=0) was achieved in 73%, median preoperative tumor burden was 11.2 cm3 (5-25), and RTB 0 cm3 (0-0.2). Median OS of patients with singular BM was 13 months (4-33) vs 20 months (5-92) for solitary BM; p=0.062. Multivariate analysis revealed singular BM as independent risk factor for poorer OS: HR 1.840 (1.202-2.817), p=0.005. Complete vs. incomplete resection showed no significant OS difference (13 vs. 13 months, p=0.737). When focusing on solitary BM, complete resection led to a longer OS than incomplete resection (21 vs. 8 months), without statistical significance(p=0.250). Achieving RTB=0 resulted in higher OS for patients with solitary BM compared to singular BM (21 vs. 12 months, p=0.027). Patients who received postoperative radiotherapy (RT) had significantly longer OS compared to those without it (14 vs. 4 months, p<0.001), with favorable OS in those receiving stereotactic radiosurgery (SRS) (15 months (3-42), p<0.001) or hypofractionated stereotactic radiotherapy (HSRT). Conclusion: When complete intracranial tumor resection RTB=0 is achieved, patients with solitary BM have a favorable outcome compared to singular BM. Singular BM was confirmed as independent risk factor. There is a strong presumption that complete resection leads to an improved oncological prognosis. Patients with solitary BM tend to benefit with a favorable outcome following complete resection. Hence, surgical resection should be considered as a treatment option for patients presenting with either no or minimal extracranial disease. Furthermore, the highly favorable impact of postoperative RT on OS was demonstrated and confirmed, especially with SRS or HSRT.

Current Aspects of Intraoperative High-Field (3T) Magnetic Resonance Imaging in Pediatric Neurosurgery: Experiences from a Recently Launched Unit at a Tertiary Referral Center.

OBJECTIVE: To evaluate the neurosurgical and economic effectiveness of a newly launched intraoperative high-field (3T) magnetic resonance imaging (MRI) suite for pediatric tumor and epilepsy neurosurgery. METHODS: Altogether, 148 procedures for 124 pediatric patients (mean age, 8.7 years; range, 0-18 years) within a 2.5-year period were undertaken in a 2-room intraoperative MRI (iopMRI) suite. Surgery was performed mainly for intractable epilepsy (n = 81; 55%) or pediatric brain tumors (n = 65; 44%) in the supine (n = 113; 76%) and prone (n = 35; 24%) positions. The mean time of iopMRI from draping to re-surgery was 50 minutes. RESULTS: IopMRI was applied not in all but in 64 of 148 procedures (43%); in 45 procedures (31%), iopMRI was estimated unnecessary at the end of surgery based on the leading surgeon's decision. In the remaining 39 procedures (26%), ultra-early postoperative MRI was carried out after closure with the patient still sterile in the head coil. Of the 64 procedures with iopMRI, second-look surgery was performed in 26% (in epilepsy surgery in 17%, in tumor surgery in 9%). We did not encounter any infections, wound revisions, or position-related or anesthesiology-related complications. CONCLUSIONS: We used iopMRI in less than half of pediatric tumor and epilepsy surgery for which it was scheduled initially. Therefore, high costs argue against its routine use in pediatric neurosurgery, although it optimized surgical results in one quarter of patients and met high safety standards.

Cytoreduction of Residual Tumor Burden Is Decisive for Prolonged Survival in Patients with Recurrent Brain Metastases-Retrospective Analysis of 219 Patients.

BACKGROUND: Despite advances in treatment for brain metastases (BMs), the prognosis for recurrent BMs remains poor and requires further research to advance clinical management and improve patient outcomes. In particular, data addressing the impact of tumor volume and surgical resection with regard to survival remain scarce. METHODS: Adult patients with recurrent BMs between December 2007 and December 2022 were analyzed. A distinction was made between operated and non-operated patients, and the residual tumor burden (RTB) was determined by using (postoperative) MRI. Survival analysis was performed and RTB cutoff values were calculated using maximally selected log-rank statistics. In addition, further analyses on systemic tumor progression and (postoperative) tumor therapy were conducted. RESULTS: In total, 219 patients were included in the analysis. Median age was 60 years (IQR 52-69). Median preoperative tumor burden was 2.4 cm3 (IQR 0.8-8.3), and postoperative tumor burden was 0.5 cm3 (IQR 0.0-2.9). A total of 95 patients (43.4%) underwent surgery, and complete cytoreduction was achieved in 55 (25.1%) patients. Median overall survival was 6 months (IQR 2-10). Cutoff RTB in all patients was 0.12 cm3, showing a significant difference (p = 0.00029) in overall survival (OS). Multivariate analysis showed preoperative KPSS (HR 0.983, 95% CI, 0.967-0.997, p = 0.015), postoperative tumor burden (HR 1.03, 95% CI 1.008-1.053, p = 0.007), and complete vs. incomplete resection (HR 0.629, 95% CI 0.420-0.941, p = 0.024) as significant. Longer survival was significantly associated with surgery for recurrent BMs (p = 0.00097), and additional analysis demonstrated the significant effect of complete resection on survival (p = 0.0027). In the subgroup of patients with systemic progression, a cutoff RTB of 0.97 cm3 (p = 0.00068) was found; patients who had received surgery also showed prolonged OS (p = 0.036). Single systemic therapy (p = 0.048) and the combination of radiotherapy and systemic therapy had a significant influence on survival (p = 0.036). CONCLUSIONS: RTB is a strong prognostic factor for survival in patients with recurrent BMs. Operated patients with recurrent BMs showed longer survival independent of systemic progression. Maximal cytoreduction should be targeted to achieve better long-term outcomes.

Comparison of EPI DWI and STEAM DWI in Early Postoperative MRI Controls After Resection of Tumors of the Central Nervous System.

PURPOSE: Diffusion-weighted imaging (DWI) is important for differentiating residual tumor and subacute infarctions in early postoperative magnetic resonance imaging (MRI) of central nervous system (CNS) tumors. In cases of pneumocephalus and especially in the presence of intraventricular trapped air, conventional echo-planar imaging (EPI) DWI is distorted by susceptibility artifacts. The performance and robustness of a newly developed DWI sequence using the stimulated echo acquisition mode (STEAM) was evaluated in patients after neurosurgical operations with early postoperative MRI. METHODS: We compared EPI and STEAM DWI of 43 patients who received 3­Tesla MRI within 72 h after a neurosurgical operation between 1 October 2019 and 30 September 2021. We analyzed susceptibility artifacts originating from air and blood and whether these artifacts compromised the detection of ischemic changes after surgery. The DWI sequences were (i) visually rated and (ii) volumetrically analyzed. RESULTS: In 28 of 43 patients, we found severe and diagnostically relevant artifacts in EPI DWI, but none in STEAM DWI. In these cases, in which artifacts were caused by intracranial air, they led to a worse detection of ischemic lesions and thus to a possible failed diagnosis or lack of judgment using EPI DWI. Additionally, volumetric analysis demonstrated a 14% smaller infarct volume detected with EPI DWI. No significant differences in visual rating and volumetric analysis were detected among the patients without severe artifacts. CONCLUSION: The newly developed version of STEAM DWI with highly undersampled radial encodings is superior to EPI DWI in patients with postoperative pneumocephalus.

Timing of Early Postoperative MRI following Primary Glioblastoma Surgery-A Retrospective Study of Contrast Enhancements in 311 Patients.

An early postoperative MRI is recommended following Glioblastoma surgery. This retrospective, observational study aimed to investigate the timing of an early postoperative MRI among 311 patients. The patterns of the contrast enhancement (thin linear, thick linear, nodular, and diffuse) and time from surgery to the early postoperative MRI were recorded. The primary endpoint was the frequencies of the different contrast enhancements within and beyond the 48-h from surgery. The time dependence of the resection status and the clinical parameters were analysed as well. The frequency of the thin linear contrast enhancements significantly increased from 99/183 (50.8%) within 48-h post-surgery to 56/81 (69.1%) beyond 48-h post-surgery. Similarly, MRI scans with no contrast enhancements significantly declined from 41/183 (22.4%) within 48-h post-surgery to 7/81 (8.6%) beyond 48-h post-surgery. No significant differences were found for the other types of contrast enhancements and the results were robust in relation to the choice of categorisation of the postoperative periods. Both the resection status and the clinical parameters were not statistically different in patients with an MRI performed before and after 48 h. The findings suggest that surgically induced contrast enhancements are less frequent when an early postoperative MRI is performed earlier than 48-h, supporting the recommendation of a 48-h window for an early postoperative MRI.

Brain metastases in the elderly - Impact of residual tumor volume on overall survival.

Background: Due to demographic changes and an increased incidence of cancer with age, the number of patients with brain metastases (BMs) constantly increases, especially among the elderly. Novel systemic therapies, such as immunotherapy, have led to improved survival in recent years, but intracranial tumor progression may occur independently of a systemically effective therapy. Despite the growing number of geriatric patients, they are often overlooked in clinical trials, and there is no consensus on the impact of BM resection on survival. Objectives: The aim of this study was to analyze the impact of resection and residual tumor volume on clinical outcome and overall survival (OS) in elderly patients suffering from BM. Methods: Patients ≥ 75 years who had surgery for BM between April 2007 and January 2020 were retrospectively included. Residual tumor burden (RTB) was determined by segmentation of early postoperative brain MRI (72 h). Contrast-enhancing tumor subvolumes were segmented manually. "Postoperative tumor volume" refers to the targeted BMs. Impact of preoperative Karnofsky performance status scale (KPSS), age, sex and RTB on OS was analyzed. Survival analyses were performed using Kaplan-Meier estimates for the univariate analysis and the Cox regression proportional hazards model for the multivariate analysis. Results: One hundred and one patients were included. Median age at surgery was 78 years (IQR 76-81). Sixty-two patients (61%) had a single BM; 16 patients (16%) had two BMs; 13 patients (13%) had three BMs; and 10 patients (10%) had more than three BMs. Median preoperative tumor burden was 10.3 cm3 (IQR 5-25 cm3), and postoperative tumor burden was 0 cm3 (IQR 0-1.1 cm3). Complete cytoreduction (RTB = 0) was achieved in 52 patients (52%). Complete resection of the targeted metastases was achieved in 78 patients (78%). Median OS was 7 months (IQR 2-11). In univariate analysis, high preoperative KPSS (HR 0.986, 95% CI 0.973-0.998, p = 0.026) and small postoperative tumor burden (HR 1.025, 95% CI 1.002-1.047, p = 0.029) were significantly associated with prolonged OS. Patients with RTB = 0 survived significantly longer than those with residual tumor did (12 [IQR 5-19] vs. 5 [IQR 3-7] months, p = 0.007). Furthermore, prolongation of survival was significantly associated with surgery in patients with favorable KPSS, with an adjusted HR of 0.986 (p = 0.026). However, there were no significances regarding age. Conclusions: RTB is a strong predictor for prolonged OS, regardless of age or cancer type. Postoperative MRI should confirm the extent of resection, as intraoperative estimates do not warrant a complete resection. It is crucial to aim for maximal cytoreduction to achieve the best long-term outcomes for these patients, despite the fact the patients are advanced in age.

Day one postoperative MRI findings following electrode placement for deep brain stimulation: analysis of a large case series.

Objective: This study sought to characterize postoperative day one MRI findings in deep brain stimulation (DBS) patients. Methods: DBS patients were identified by CPT and had their reviewed by a trained neuroradiologist and neurosurgeon blinded to MR sequence and patient information. The radiographic abnormalities of interest were track microhemorrhage, pneumocephalus, hematomas, and edema, and the occurrence of these findings in compare the detection of these complications between T1/T2 gradient-echo (GRE) and T1/T2 fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) sequences was compared. The presence, size, and association of susceptibility artifact with other radiographic abnormalities was also described. Lastly, the association of multiple microelectrode cannula passes with each radiographic finding was evaluated. Ad-hoc investigation evaluated hemisphere-specific associations. Multiple logistic regression with Bonferroni correction (corrected p = 0.006) was used for all analysis. Results: Out of 198 DBS patients reviewed, 115 (58%) patients showed entry microhemorrhage; 77 (39%) track microhemorrhage; 44 (22%) edema; 69 (35%) pneumocephalus; and 12 (6%) intracranial hematoma. T2 GRE was better for detecting microhemorrhage (OR = 14.82, p < 0.0001 for entry site and OR = 4.03, p < 0.0001 for track) and pneumocephalus (OR = 11.86, p < 0.0001), while T2 FLAIR was better at detecting edema (OR = 123.6, p < 0.0001). The relatively common findings of microhemorrhage and edema were best visualized by T2 GRE and T2 FLAIR sequences, respectively. More passes intraoperatively was associated with detection of ipsilateral track microhemorrhage (OR = 7.151, p < 0.0001 left; OR = 8.953, p < 0.0001 right). Susceptibility artifact surrounding electrodes possibly interfered with further detection of ipsilateral edema (OR = 4.323, p = 0.0025 left hemisphere only). Discussion: Day one postoperative magnetic resonance imaging (MRI) for DBS patients can be used to detect numerous radiographic abnormalities not identifiable on a computed tomographic (CT) scan. For this cohort, multiple stimulating cannula passes intraoperatively was associated with increased microhemorrhage along the electrode track. Further studies should be performed to evaluate the clinical relevance of these observations.

The Impact of Postoperative Tumor Burden on Patients With Brain Metastases.

Background: Brain metastases were considered to be well-defined lesions, but recent research points to infiltrating behavior. Impact of postoperative residual tumor burden (RTB) and extent of resection are still not defined enough. Patients and Methods: Adult patients with surgery of brain metastases between April 2007 and January 2020 were analyzed. Early postoperative MRI (<72 h) was used to segment RTB. Survival analysis was performed and cutoff values for RTB were revealed. Separate (subgroup) analyses regarding postoperative radiotherapy, age, and histopathological entities were performed. Results: A total of 704 patients were included. Complete cytoreduction was achieved in 487/704 (69.2%) patients, median preoperative tumor burden was 12.4 cm3 (IQR 5.2-25.8 cm3), median RTB was 0.14 cm3 (IQR 0.0-2.05 cm3), and median postoperative tumor volume of the targeted BM was 0.0 cm3 (IQR 0.0-0.1 cm3). Median overall survival was 6 months (IQR 2-18). In multivariate analysis, preoperative KPSS (HR 0.981982, 95% CI, 0.9761-0.9873, p < 0.001), age (HR 1.012363; 95% CI, 1.0043-1.0205, p = 0.0026), and preoperative (HR 1.004906; 95% CI, 1.0003-1.0095, p = 0.00362) and postoperative tumor burden (HR 1.017983; 95% CI; 1.0058-1.0303, p = 0.0036) were significant. Maximally selected log rank statistics showed a significant cutoff for RTB of 1.78 cm3 (p = 0.0022) for all and 0.28 cm3 (p = 0.0047) for targeted metastasis and cutoff for the age of 67 years (p < 0.001). (Stereotactic) Radiotherapy had a significant impact on survival (p < 0.001). Conclusions: RTB is a strong predictor for survival. Maximal cytoreduction, as confirmed by postoperative MRI, should be achieved whenever possible, regardless of type of postoperative radiotherapy.

Deep learning-based automated segmentation of resection cavities on postsurgical epilepsy MRI.

Accurate segmentation of surgical resection sites is critical for clinical assessments and neuroimaging research applications, including resection extent determination, predictive modeling of surgery outcome, and masking image processing near resection sites. In this study, an automated resection cavity segmentation algorithm is developed for analyzing postoperative MRI of epilepsy patients and deployed in an easy-to-use graphical user interface (GUI) that estimates remnant brain volumes, including postsurgical hippocampal remnant tissue. This retrospective study included postoperative T1-weighted MRI from 62 temporal lobe epilepsy (TLE) patients who underwent resective surgery. The resection site was manually segmented and reviewed by a neuroradiologist (JMS). A majority vote ensemble algorithm was used to segment surgical resections, using 3 U-Net convolutional neural networks trained on axial, coronal, and sagittal slices, respectively. The algorithm was trained using 5-fold cross validation, with data partitioned into training (N = 27) testing (N = 9), and validation (N = 9) sets, and evaluated on a separate held-out test set (N = 17). Algorithm performance was assessed using Dice-Sørensen coefficient (DSC), Hausdorff distance, and volume estimates. Additionally, we deploy a fully-automated, GUI-based pipeline that compares resection segmentations with preoperative imaging and reports estimates of resected brain structures. The cross-validation and held-out test median DSCs were 0.84 ± 0.08 and 0.74 ± 0.22 (median ± interquartile range) respectively, which approach inter-rater reliability between radiologists (0.84-0.86) as reported in the literature. Median 95 % Hausdorff distances were 3.6 mm and 4.0 mm respectively, indicating high segmentation boundary confidence. Automated and manual resection volume estimates were highly correlated for both cross-validation (r = 0.94, p < 0.0001) and held-out test subjects (r = 0.87, p < 0.0001). Automated and manual segmentations overlapped in all 62 subjects, indicating a low false negative rate. In control subjects (N = 40), the classifier segmented no voxels (N = 33), <50 voxels (N = 5), or a small volumes<0.5 cm3 (N = 2), indicating a low false positive rate that can be controlled via thresholding. There was strong agreement between postoperative hippocampal remnant volumes determined using automated and manual resection segmentations (r = 0.90, p < 0.0001, mean absolute error = 6.3 %), indicating that automated resection segmentations can permit quantification of postoperative brain volumes after epilepsy surgery. Applications include quantification of postoperative remnant brain volumes, correction of deformable registration, and localization of removed brain regions for network modeling.

The Impact of an Ultra-Early Postoperative MRI on Treatment of Lower Grade Glioma.

The timing of MRI imaging after surgical resection may have an important role in assessing the extent of resection (EoR) and in determining further treatment. The aim of our study was to evaluate the time dependency of T2 and FLAIR changes after surgery for LGG. The Log-Glio database of patients treated at our hospital from 2016 to 2021 was searched for patients >18a and non-enhancing intra-axial lesion with complete MR-imaging protocol. A total of 16 patients matched the inclusion criteria and were thus selected for volumetric analysis. All patients received an intraoperative scan (iMRI) after complete tumor removal, an ultra-early postoperative scan after skin closure, an early MRI within 48 h and a late follow up MRI after 3-4 mo. Detailed volumetric analysis of FLAIR and T2 abnormalities was conducted. Demographic data and basic characteristics were also analyzed. An ultra-early postoperative MRI was performed within a median time of 30 min after skin closure and showed significantly lower FLAIR (p = 0.003) and T2 (p = 0.003) abnormalities when compared to early postoperative MRI (median 23.5 h), though no significant difference was found between ultra-early and late postoperative FLAIR (p = 0.422) and T2 (p = 0.575) images. A significant difference was calculated between early and late postoperative FLAIR (p = 0.005) and T2 (p = 0.019) MRI scans. Additionally, we found no significant difference between intraoperative and ultra-early FLAIR/T2 (p = 0.919 and 0.499), but we found a significant difference between iMRI and early MRI FLAIR/T2 (p = 0.027 and p = 0.035). Therefore, a postoperative MRI performed 24 h or 48 h might lead to false positive findings. An MRI scan in the first hour after surgery (ultra-early) correlated best with residual tumor at 3 months follow up. An iMRI with open skull, at the end of resection, was similar to an ultra-early MRI with regard to residual tumor.

Surgically Induced Contrast Enhancements on Intraoperative and Early Postoperative MRI Following High-Grade Glioma Surgery: A Systematic Review.

For the radiological assessment of resection of high-grade gliomas, a 72-h diagnostic window is recommended to limit surgically induced contrast enhancements. However, such enhancements may occur earlier than 72 h post-surgery. This systematic review aimed to assess the evidence on the timing of the postsurgical MRI. PubMed, Embase, Web of Science and Cochrane were searched following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Only original research articles describing surgically induced contrast enhancements on MRI after resection for high-grade gliomas were included and analysed. The frequency of different contrast enhancement patterns on intraoperative MRI (iMRI) and early postoperative MRI (epMRI) was recorded. The search resulted in 1443 studies after removing duplicates, and a total of 12 studies were chosen for final review. Surgically induced contrast enhancements were reported at all time points after surgery, including on iMRI, but their type and frequency vary. Thin linear contrast enhancements were commonly found to be surgically induced and were less frequently recorded on postoperative days 1 and 2. This suggests that the optimal time to scan may be at or before this time. However, the evidence is limited, and higher-quality studies using larger and consecutively sampled populations are needed.

Second window ICG predicts gross-total resection and progression-free survival during brain metastasis surgery.

OBJECTIVE: Metastases are the most common intracranial malignancies and complete resection can provide relief of neurological symptoms and reduce recurrence. The authors' prospective pilot study in 2017 demonstrated promising results for the application of high-dose, delayed imaging of indocyanine green (ICG), known as second window ICG (SWIG), in patients undergoing surgery for brain metastases. In this prospective cohort study, the authors evaluated intraoperative imaging and clinical outcomes of treatment using SWIG. METHODS: Patients were prospectively enrolled in an approved study of high-dose, delayed ICG (SWIG) and received 5 mg/kg (2014-2018) or 2.5 mg/kg (2018-2019) ICG 24 hours preoperatively. Intraoperatively, near-infrared (NIR) imaging was performed using a dedicated NIR exoscope. NIR images were analyzed and the signal-to-background ratio (SBR) was calculated to quantify fluorescence. Residual fluorescence on the postresection NIR view was compared and correlated to the residual gadolinium enhancement on postoperative MRI. Patient survival and predictive factors were analyzed. RESULTS: In total, 51 intracranial metastases were surgically treated in 47 patients in this cohort. All 51 metastatic tumors demonstrated strong NIR fluorescence (mean SBR 4.9). In tumors ≤ 10 mm from the cortical surface, SWIG with 5 mg/kg ICG produced enhanced transdural tumor visibility (91.3%) compared to 2.5 mg/kg (52.9%; p = 0.0047). Neoplastic margin detection using NIR fluorescence compared to white light improved sensitivity, albeit lowered specificity; however, increasing the SBR cutoff for positive fluorescence significantly improved specificity without sacrificing sensitivity, increasing the overall accuracy from 57.5% to 72.5%. A lack of residual NIR fluorescence after resection was closely correlated with a lack of residual enhancement on postoperative MRI (p = 0.007). Among the 16 patients in whom tumor recurred at the site of surgery, postoperative MRI successfully predicted 8 cases, whereas the postresection NIR view predicted 12 cases. Progression-free survival rate at 12 months was greater for patients without residual NIR fluorescence (38%) than for those without residual enhancement on postoperative MRI (29%). CONCLUSIONS: The current study demonstrates the clinical benefits of the SWIG technique in surgery for patients with brain metastases. Specifically, this technique allows for dose-dependent, transdural localization of neoplasms and improved sensitivity in neoplastic margin detection. Postresection residual fluorescence can be a powerful tool to evaluate extent of resection in conjunction with MRI, and it may guide decisions on brain metastasis management.

Near-Infrared Imaging with Second-Window Indocyanine Green in Newly Diagnosed High-Grade Gliomas Predicts Gadolinium Enhancement on Postoperative Magnetic Resonance Imaging.

PURPOSE: Intraoperative molecular imaging with tumor-targeting fluorophores offers real-time detection of neoplastic tissue. The second window indocyanine green (SWIG) technique relies on passive accumulation of indocyanine green (ICG), a near-infrared fluorophore, in neoplastic tissues. In this study, we explore the ability of SWIG to detect neoplastic tissue and to predict postoperative magnetic resonance imaging (MRI) findings intraoperatively. PROCEDURES: Retrospective data were collected from 36 patients with primary high-grade gliomas (HGG) enrolled as part of a larger trial between October 2014 and October 2018. Patients received systemic ICG infusions at 2.5-5 mg/kg 24 h preoperatively. Near-infrared fluorescence was recorded throughout the case and from biopsy specimens. The presence/location of residual SWIG signal after resection was compared to the presence/location of residual gadolinium enhancement on postoperative MRI. The extent of resection was not changed based on near-infrared imaging. RESULTS: All 36 lesions demonstrated strong near-infrared fluorescence (signal-to-background = 6.8 ± 2.2) and 100 % of tumors reaching the cortex were visualized before durotomy. In 78 biopsy specimens, near-infrared imaging demonstrated higher sensitivity and accuracy than white light for diagnosing neoplastic tissue intraoperatively. Furthermore, near-infrared imaging predicted gadolinium enhancement on postoperative MRI with 91 % accuracy, with visualization of residual enhancement as small as 0.3 cm3. Patients with no residual near-infrared signal after resection were significantly more likely to have complete resection on postoperative MRI (p value < 0.0001). CONCLUSIONS: Intraoperative imaging with SWIG demonstrates highly sensitive detection of HGG tissue in real time. Furthermore, post-resection near-infrared imaging correlates with postoperative MRI. Overall, our findings suggest that SWIG can provide surgeons with MRI-like results in real time, potentially increasing resection rates.

Postoperative Magnetic Resonance Imaging After Surgery of Brain Metastases: Analysis of Extent of Resection and Potential Risk Factors for Incomplete Resection.

BACKGROUND: Extent of resection (EOR) constitutes a crucial factor for patient prognosis in surgery of brain metastases (BMs). According to early studies using postoperative magnetic resonance imaging (MRI), an unexpected residual tumor was not uncommon. Knowledge of potential risk factors for incomplete BM resection would be of major importance to optimize surgical strategies. The aim of this study was to evaluate EOR in a large cohort and analyze potential risk factors for incomplete BM resection. METHODS: Patients with BM resection and available postoperative MRI were included. Intraoperative estimation of EOR by the neurosurgeon was noted. Additionally, EOR was determined by postoperative MRI. Potential risk factors for incomplete resection were investigated. RESULTS: There were 145 patients with 163 BMs included. According to postoperative MRI, complete resection was achieved in 103 (63%) BMs, and resection was incomplete in 44 (27%) BMs. Postoperative MRI detected unexpected residual tumor in 32 (25%) BMs, and a misjudgment of the EOR by the neurosurgeon was found in 29% of cases. Regarding risk factors for incomplete resection, preoperative tumor volume was significantly larger in incompletely resected BMs compared with completely resected BMs (P = 0.011). All other analyzed risk factors had no significant influence on EOR. CONCLUSIONS: Our data indicate that postoperative MRI is able to detect a high portion of unexpected residual tumors after surgery of BMs. Preoperative tumor volume in particular represents an important risk factor for incomplete resection, and hence neurosurgeons should pay special attention to avoid residual tumor tissue.