Using intraoperative dynamic contrast-enhanced T1-weighted MRI to identify residual tumor in glioblastoma surgery

Comparison of lung lesion assessment using free-breathing dynamic contrast-enhanced 1.5-T MRI with a golden-angle radial stack-of-stars VIBE sequence and CT

BACKGROUND

Few studies have investigated the feasibility of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using a free-breathing golden-angle radial stack-of-stars volume-interpolated breath-hold examination (FB radial VIBE) sequence in the lung.

PURPOSE

To investigate whether DCE-MRI using the FB radial VIBE sequence can assess morphological and kinetic parameters in patients with pulmonary lesions, with computed tomography (CT) as the reference.

MATERIAL AND METHODS

In total, 43 patients (30 men; mean age = 64 years) with one lesion each were prospectively enrolled. Morphological and kinetic features on MRI were calculated. The diagnostic performance of morphological MR features was evaluated using a receiver operating characteristic (ROC) curve. Kinetic features were compared among subgroups based on histopathological subtype, lesion size, and lymph node metastasis.

RESULTS

The maximum diameter was not significantly different between CT and MRI (3.66 ± 1.62 cm vs. 3.64 ± 1.72 cm; P = 0.663). Spiculation, lobulation, cavitation or bubble-like areas of low attenuation, and lymph node enlargement had an area under the ROC curve (AUC) >0.9, while pleural indentation yielded an AUC of 0.788. The lung cancer group had significantly lower Ktrans, Ve, and initial AUC values than the other cause inflammation group (0.203, 0.158, and 0.589 vs. 0.597, 0.385, and 1.626; P < 0.05) but significantly higher values than the tuberculosis group (P < 0.05).

CONCLUSION

Morphology features derived from FB radial VIBE have high correlations with CT, and kinetic analyses show significant differences between benign and malignant lesions. DCE-MRI with FB radial VIBE could serve as a complementary quantification tool to CT for radiation-free assessments of lung lesions.

Intraoperative MR Imaging during Glioma Resection

One of the major issues in the surgical treatment of gliomas is the concern about maximizing the extent of resection while minimizing neurological impairment. Thus, surgical planning by carefully observing the relationship between the glioma infiltration area and eloquent area of the connecting fibers is crucial. Neurosurgeons usually detect an eloquent area by functional MRI and identify a connecting fiber by diffusion tensor imaging. However, during surgery, the accuracy of neuronavigation can be decreased due to brain shift, but the positional information may be updated by intraoperative MRI and the next steps can be planned accordingly. In addition, various intraoperative modalities may be used to guide surgery, including neurophysiological monitoring that provides real-time information (e.g., awake surgery, motor-evoked potentials, and sensory evoked potential); photodynamic diagnosis, which can identify high-grade glioma cells; and other imaging techniques that provide anatomical information during the surgery. In this review, we present the historical and current context of the intraoperative MRI and some related approaches for an audience active in the technical, clinical, and research areas of radiology, as well as mention important aspects regarding safety and types of devices.

[Intraoperative magnetic resonance imaging in surgery of brain gliomas]

Intraoperative magnetic resonance imaging (iMRI) is used in surgery of supratentorial gliomas to assess resection quality, as well as in neoplasm biopsy to control the needle position. Scanners coupled with operating table ensure fast intraoperative imaging, but they require the use of non-magnetic surgical tools. Surgery outside the scanner 5G line allows working with conventional instruments, but patient transportation takes time. Portable iMRI systems do not interfere with surgical workflow but these scanners have poor resolution. Positioning of MRI scanners in adjacent rooms allows imaging simultaneously for several surgeries. Low-field MRI scanners are effective for control of contrast-enhanced glioma resection quality. However, these scanners are less useful in demarcation of residual low-grade tumors. High-field MRI scanners have no similar disadvantage. These scanners ensure fast detection of residual gliomas of all types and functional imaging. Artifacts during iMRI are usually a result of iatrogenic traumatic brain injury and contrast agent leakage. Ways of their prevention are discussed in the review.

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.

Label-free detection of brain tumors in a 9L gliosarcoma rat model using stimulated Raman scattering-spectroscopic optical coherence tomography

SIGNIFICANCE

In neurosurgery, it is essential to differentiate between tumor and healthy brain regions to maximize tumor resection while minimizing damage to vital healthy brain tissue. However, conventional intraoperative imaging tools used to guide neurosurgery are often unable to distinguish tumor margins, particularly in infiltrative tumor regions and low-grade gliomas.

AIM

The aim of this work is to assess the feasibility of a label-free molecular imaging tool called stimulated Raman scattering-spectroscopic optical coherence tomography (SRS-SOCT) to differentiate between healthy brain tissue and tumor based on (1) structural biomarkers derived from the decay rate of signals as a function of depth and (2) molecular biomarkers based on relative differences in lipid and protein composition extracted from the SRS signals.

APPROACH

SRS-SOCT combines the molecular sensitivity of SRS (based on vibrational spectroscopy) with the spatial and spectral multiplexing capabilities of SOCT to enable fast, spatially and spectrally resolved molecular imaging. SRS-SOCT is applied to image a 9L gliosarcoma rat tumor model, a well-characterized model that recapitulates human high-grade gliomas, including high proliferative capability, high vascularization, and infiltration at the margin. Structural and biochemical signatures acquired from SRS-SOCT are extracted to identify healthy and tumor tissues.

RESULTS

Data show that SRS-SOCT provides light-scattering-based signatures that correlate with the presence of tumors, similar to conventional OCT. Further, nonlinear phase changes from the SRS interaction, as measured with SRS-SOCT, provide an additional measure to clearly separate tumor tissue from healthy brain regions. We also show that the nonlinear phase signals in SRS-SOCT provide a signal-to-noise advantage over the nonlinear amplitude signals for identifying tumors.

CONCLUSIONS

SRS-SOCT can distinguish both spatial and spectral features that identify tumor regions in the 9L gliosarcoma rat model. This tool provides fast, label-free, nondestructive, and spatially resolved molecular information that, with future development, can potentially assist in identifying tumor margins in neurosurgery.

Minimizing OCT quantification error via a surface-tracking imaging probe

OCT-based quantitative tissue optical properties imaging is a promising technique for intraoperative brain cancer assessment. The attenuation coefficient analysis relies on the depth-dependent OCT intensity profile, thus sensitive to tissue surface positions relative to the imaging beam focus. However, it is almost impossible to maintain a steady tissue surface during intraoperative imaging due to the patient's arterial pulsation and breathing, the operator's motion, and the complex tissue surface geometry of the surgical cavity. In this work, we developed an intraoperative OCT imaging probe with a surface-tracking function to minimize the quantification errors in optical attenuation due to the tissue surface position variations. A compact OCT imaging probe was designed and engineered to have a long working distance of ∼ 41 mm and a large field of view of 4 × 4 mm2 while keeping the probe diameter small (9 mm) to maximize clinical versatility. A piezo-based linear motor was integrated with the imaging probe and controlled based upon real-time feedback of tissue surface position inferred from OCT images. A GPU-assisted parallel processing algorithm was implemented, enabling detection and tracking of tissue surface in real-time and successfully suppressing more than 90% of the typical physiologically induced motion range. The surface-tracking intraoperative OCT imaging probe could maintain a steady beam focus inside the target tissue regardless of the surface geometry or physiological motions and enabled to obtain tissue optical attenuation reliably for assessing brain cancer margins in challenging intraoperative settings.

Initial Experience Using Intraoperative Magnetic Resonance Imaging During a Trans-Sulcal Tubular Retractor Approach for the Resection of Deep-Seated Brain Tumors: A Case Series

BACKGROUND

Treatment of deep-seated subcortical intrinsic brain tumors remains challenging and may be improved with trans-sulcal tubular brain retraction techniques coupled with intraoperative magnetic resonance imaging (iMRI).

OBJECTIVE

To conduct a preliminary assessment of feasibility and efficacy of iMRI in tubular retractor-guided resections of intrinsic brain tumors.

METHODS

Assessment of this technique and impact upon outcomes were assessed in a preliminary series of brain tumor patients from 2 centers.

RESULTS

Ten patients underwent resection with a tubular retractor system and iMRI. Mean age was 53.2 ± 9.0 yr (range: 37-61 yr, 80% male). Lesions included 6 gliomas (3 glioblastomas, 1 recurrent anaplastic astrocytoma, and 2 low-grade gliomas) and 4 brain metastases (1 renal cell, 1 breast, 1 lung, and 1 melanoma). Mean maximal tumor diameter was 2.9 ± 0.95 cm (range 1.2-4.3 cm). The iMRI demonstrated subtotal resection (STR) in 6 of 10 cases (60%); additional resection was performed in 5 of 6 cases (83%), reducing STR rate to 2 of 10 cases (20%), with both having tumor encroaching on eloquent structures. Seven patients (70%) were stable or improved neurologically immediately postoperatively. Three patients (30%) had new postoperative neurological deficits, 2 of which were transient. Average hospital length of stay was 3.4 ± 2.0 d (range: 1-7 d).

CONCLUSION

Combining iMRI with tubular brain retraction techniques is feasible and may improve the extent of resection of deep-seated intrinsic brain tumors that are incompletely visualized with the smaller surgical exposure of tubular retractors.

Combining Functional Studies with Intraoperative MRI in Glioma Surgery

Maximal safe resection is the cornerstone of treatment for low-grade and high-grade gliomas. In addition to high-resolution anatomic MRI studies that highlight tumor architecture, it is important to determine the relationship of the tumor to the eloquent cortical and subcortical areas to avoid introducing or exacerbating a neurologic deficit. The goal of this review was to highlight imaging modalities that provide functional information and can be integrated with intraoperative MRI navigation to maximize the extent of resection while preserving a patient's neurologic function.

Intraoperative resection control using arterial spin labeling - Proof of concept, reproducibility of data and initial results

Objectives

Intraoperative magnetic resonance imaging is a unique tool for visualizing structures during resection and/or for updating any kind of neuronavigation that might be hampered as a result of brain shift during surgery. Advanced MRI techniques such as perfusion-weighted imaging have already proven to be important in the initial diagnosis preoperatively, but can also help to differentiate between tumor and surgically induced changes intraoperatively. Commonly used methods to visualize brain perfusion include contrast agent administration and are therefore somewhat limited. One method that uses blood as an internal contrast medium is arterial spin labeling (ASL), which might represent an attractive alternative.

Materials and methods

Ten healthy volunteers were examined using three different scanners and coils within 1 h (3T Achieva MRI using 32-channel head coil, 1.5T Achieva MRI using a 6-channel head coil, 1.5 Intera Scanner using 2 surface coils, Philips, Best, The Netherlands) and quantitative CBF values were calculated and compared between the different setups. Additionally, in eight patients with glioblastoma multiforme, ASL was used pre-, intra-, and postoperatively to define tumor tissue and the extent of resection in comparison to structural imaging.

Results

A high correlation (r = 0.91–0.96) was found between MRI scanners and coils used. ASL was as reliable as conventional MR imaging if complete resection was already achieved, but additionally provided valuable information regarding residual tumor tissue in one patient.

Conclusions

Intraoperative arterial spin-labeling is a feasible, reproducible, and reliable tool to map CBF in brain tumors and seems to give beneficial information compared to conventional intraoperative MR imaging in partial resection.

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The use of arterial spin labeling intraoperatively during neurosurgical interventions is presented.

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Reproducibility and comparability using various field strengths were successfully proven in a volunteer cohort.

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Detection of residual tumor in patients was compared to contrast-enhanced imaging.

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Residual tumor could be identified with a high accuracy.

Robust and fast characterization of OCT-based optical attenuation using a novel frequency-domain algorithm for brain cancer detection

Cancer is known to alter the local optical properties of tissues. The detection of OCT-based optical attenuation provides a quantitative method to efficiently differentiate cancer from non-cancer tissues. In particular, the intraoperative use of quantitative OCT is able to provide a direct visual guidance in real time for accurate identification of cancer tissues, especially these without any obvious structural layers, such as brain cancer. However, current methods are suboptimal in providing high-speed and accurate OCT attenuation mapping for intraoperative brain cancer detection. In this paper, we report a novel frequency-domain (FD) algorithm to enable robust and fast characterization of optical attenuation as derived from OCT intensity images. The performance of this FD algorithm was compared with traditional fitting methods by analyzing datasets containing images from freshly resected human brain cancer and from a silica phantom acquired by a 1310 nm swept-source OCT (SS-OCT) system. With graphics processing unit (GPU)-based CUDA C/C++ implementation, this new attenuation mapping algorithm can offer robust and accurate quantitative interpretation of OCT images in real time during brain surgery.

Detection of human brain cancer infiltration ex vivo and in vivo using quantitative optical coherence tomography

More complete brain cancer resection can prolong survival and delay recurrence. However, it is challenging to distinguish cancer from noncancer tissues intraoperatively, especially at the transitional, infiltrative zones. This is especially critical in eloquent regions (for example, speech and motor areas). This study tested the feasibility of label-free, quantitative optical coherence tomography (OCT) for differentiating cancer from noncancer in human brain tissues. Fresh ex vivo human brain tissues were obtained from 32 patients with grade II to IV brain cancer and 5 patients with noncancer brain pathologies. On the basis of volumetric OCT imaging data, pathologically confirmed brain cancer tissues (both high- and low-grade) had significantly lower optical attenuation values at both cancer core and infiltrated zones when compared with noncancer white matter, and OCT achieved high sensitivity and specificity at an attenuation threshold of 5.5 mm(-1) for brain cancer patients. We also used this attenuation threshold to confirm the intraoperative feasibility of performing in vivo OCT-guided surgery using a murine model harboring human brain cancer. Our OCT system was capable of processing and displaying a color-coded optical property map in real time at a rate of 110 to 215 frames per second, or 1.2 to 2.4 s for an 8- to 16-mm(3) tissue volume, thus providing direct visual cues for cancer versus noncancer areas. Our study demonstrates the translational and practical potential of OCT in differentiating cancer from noncancer tissue. Its intraoperative use may facilitate safe and extensive resection of infiltrative brain cancers and consequently lead to improved outcomes when compared with current clinical standards.

Comparison of intravoxel incoherent motion diffusion-weighted MR imaging with dynamic contrast-enhanced MRI for differentiating lung cancer from benign solitary pulmonary lesions

BACKGROUND

To compare intravoxel incoherent motion (IVIM) and pharmacokinetic analysis dynamic contrast-enhanced MR imaging (DCE-MRI) in distinguishing lung cancer (LC) from benign solitary pulmonary lesions (SPL).

METHODS

This prospective study was approved by the institutional review board, and written informed consent was obtained. Eighty-one consecutive patients considered for SPL underwent DW-IVIM and DCE-3T MRI. ADC, D, D*, and f were calculated with mono- and bi-exponential models. K(trans) , kep , ve , and vp were calculated with the modified Tofts model. Receiver operating characteristic (ROC) analysis was constructed to determine the diagnostic performance of IVIM and DCE-MRI in discriminating LC from benignity.

RESULTS

There were 29 patients with a total of 48 benign SPL and 52 LCs: 4 small cell carcinomas (SCLC), 19 squamous cell carcinomas (SCC), and 29 adenocarcinomas (Adeno-Ca). Both Adeno-Ca (ADC: 1.19 ± 0.23 × 10(-3) mm(2) /s; D:1.12 ± 0.35 × 10(-3) mm(2) /s; ve :0.27 ± 0.13; K(trans) :0.24 ± 0.09 min(-1) ; kep :0.90 ± 0.45 min(-1) ) and SCC (1.13± 0.28 × 10(-3) mm(2) /s; 1.02 ± 0.32 10(-3) mm(2) /s; 0.32 ± 0.14; 0.26 ± 0.08 min(-1) ; 0.90 ± 0.48 min(-1) ) had significantly lower ADC, D, ve and larger K(trans) , kep than benignity (1.37 ± 0.38 × 10(-3) mm(2) /s; 1.34 ± 0.45 × 10(-3) mm(2) /s; 0.42 ± 0.19; 0.19 ± 0.08 min(-1) ; 0.53 ± 0.26 min(-1) ). D (72.2%) had significantly higher accuracy (72.2%) and higher sensitivity (91.3%) than other imaging indices (accuracy: 55.5-68.0%; sensitivity: 41.3-78.3%; all P < 0.01) except for accuracy in kep (70.8%; P > 0.05) in discriminating LC from benignity. K(trans) exhibited significantly higher specificity (84.6%) than the other indices (38.5-73.1%; P < 0.01). These results can be improved by combined D and K(trans) , leading to a sensitivity, specificity and accuracy of 94.2%, 92%, and 93.5%, respectively.

CONCLUSION

IVIM-derived D and DCE-derived K(trans) are two promising parameters for differentiating LC from benignity.

Intraoperative MR Imaging in Neurosurgery

Intraoperative magnetic resonance imaging (iMRI) has dramatically expanded and nowadays presents state-of-the-art technique for image-guided neurosurgery, facilitating critical precision and effective surgical treatment of various brain pathologies. Imaging hardware providing basic imaging sequences as well as advanced MRI can be seamlessly integrated into routine surgical environments, which continuously leads to emerging indications for iMRI-assisted surgery. Besides the obvious intraoperative diagnostic yield, the initial clinical benefits have to be confirmed by future-controlled long-term studies.

Intraoperative perfusion magnetic resonance imaging: Cutting-edge improvement in neurosurgical procedures

The goal in brain tumor surgery is to remove the maximum achievable amount of the tumor, preventing damage to “eloquent” brain regions as the amount of brain tumor resection is one of the prognostic factors for time to tumor progression and median survival. To achieve this goal, a variety of technical advances have been introduced, including an operating microscope in the late 1950s, computer-assisted devices for surgical navigation and more recently, intraoperative imaging to incorporate and correct for brain shift during the resection of the lesion. However, surgically induced contrast enhancement along the rim of the resection cavity hampers interpretation of these intraoperatively acquired magnetic resonance images. To overcome this uncertainty, perfusion techniques [dynamic contrast enhanced magnetic resonance imaging (DCE-MRI), dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI)] have been introduced that can differentiate residual tumor from surgically induced changes at the rim of the resection cavity and thus overcome this remaining uncertainty of intraoperative MRI in high grade brain tumor resection.

Neurosurgical oncology: advances in operative technologies and adjuncts

Modern glioma surgery has evolved around the central tenet of safely maximizing resection. Recent surgical adjuncts have focused on increasing the maximum extent of resection while minimizing risk to functional brain. Technologies such as cortical and subcortical stimulation mapping, intraoperative magnetic resonance imaging, functional neuronavigation, navigable intraoperative ultrasound, neuroendoscopy, and fluorescence-guided resection have been developed to augment the identification of tumor while preserving brain anatomy and function. However, whether these technologies offer additional long-term benefits to glioma patients remains to be determined. Here we review advances over the past decade in operative technologies that have offered the most promising benefits for glioblastoma patients.

Dynamic contrast-enhanced magnetic resonance imaging: applications in oncology

Dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) allows functional characterisation of tissue perfusion characteristics and acts as a biomarker for tumour angiogenesis. It involves serial acquisition of MRI images before and after injection of contrast, as such, tissue perfusion and permeability can be assessed based on the signal enhancement kinetics. The ability to evaluate whole tumour volumes in a non-invasive manner makes DCE MRI especially attractive for potential oncological applications. Here we provide an overview of the current research involving DCE MRI as a biomarker for the diagnosis and characterisation of malignancies, prediction of the therapeutic response and survival outcomes, as well as radiation therapy planning.