Visualization Of Brain Tumors Research Articles

Visualization of Brain Tumors with Infrared-Labeled Aptamers for Fluorescence-Guided Surgery.

Gliomas remain challenging brain tumors to treat due to their infiltrative nature. Accurately identifying tumor boundaries during surgery is crucial for successful resection. This study introduces an innovative intraoperative visualization method utilizing surgical fluorescence microscopy to precisely locate tumor cell dissemination. Here, the focus is on the development of a novel contrasting agent (IR-Glint) for intraoperative visualization of human glial tumors comprising infrared-labeled Glint aptamers. The specificity of IR-Glint is assessed using flow cytometry and microscopy on primary cell cultures. In vivo effectiveness is studied on mouse and rabbit models, employing orthotopic xenotransplantation of human brain gliomas with various imaging techniques, including PET/CT, in vivo fluorescence visualization, confocal laser scanning, and surgical microscopy. The experiments validate the potential of IR-Glint for the intraoperative visualization of gliomas using infrared imaging. IR-Glint penetrates the blood-brain barrier and can be used for both intravenous and surface applications, allowing clear visualization of the tumor. The surface application directly to the brain reduces the dosage required and mitigates potential toxic effects on the patient. The research shows the potential of infrared dye-labeled aptamers for accurately visualizing glial tumors during brain surgery. This novel aptamer-assisted fluorescence-guided surgery (AptaFGS) may pave the way for future advancements in the field of neurosurgery.

Meningiomas with CNS invasion.

CNS invasion has been included as an independent criterion for the diagnosis of a high-grade (WHO and CNS grade 2 and 3) meningioma in the 2016 and more recently in the 2021 WHO classification. However, the prognostic role of brain invasion has recently been questioned. Also, surgical treatment for brain invasive meningiomas may pose specific challenges. We conducted a systematic review of the 2016-2022 literature on brain invasive meningiomas in Pubmed, Scopus, Web of Science and the Cochrane Library. The prognostic relevance of brain invasion as a stand-alone criterion is still unclear. Additional and larger studies using robust definitions of histological brain invasion and addressing the issue of sampling errors are clearly warranted. Although the necessity of molecular profiling in meningioma grading, prognostication and decision making in the future is obvious, specific markers for brain invasion are lacking for the time being. Advanced neuroimaging may predict CNS invasion preoperatively. The extent of resection (e.g., the Simpson grading) is an important predictor of tumor recurrence especially in higher grade meningiomas, but also - although likely to a lesser degree - in benign tumors, and therefore also in brain invasive meningiomas with and without other histological features of atypia or malignancy. Hence, surgery for brain invasive meningiomas should follow the principles of maximal but safe resections. There are some data to suggest that safety and functional outcomes in such cases may benefit from the armamentarium of surgical adjuncts commonly used for surgery of eloquent gliomas such as intraoperative monitoring, awake craniotomy, DTI tractography and further advanced intraoperative brain tumor visualization.

Study of the diagnostic efficiency of single-photon emission computed tomography with [<sup>99m</sup>Tc]Tc-1-THIO-D-glucose in visualization of brain tumors

The aim of the study was to evaluate the feasibility of using single-photon emission computed tomography (SPECT) with [99mTc]Tc-1-THIO-D-glucose in the detection of brain tumor malignancy. Material and methods. The study included 70 patients diagnosed with grade II–Iv malignant brain tumors and 10 patients with benign brain tumors. The control group consisted of 20 patients who had no pathological changes in the brain at the time of diagnosis. All patients underwent single-photon emission computed tomography of the brain 40 minutes after intravenous injection of [99mTc]Tc-1-THIO-D-glucose at a dose of 500 MBq. The [[99mTc]Tc-1-THIO-D-glucose radiopharmaceutical was prepared directly in the nuclear medicine department in strict accordance with the instructions. The head and neck of the patient fell into the field of view of the detectors of the gamma camera, 32 projections were recorded in a matrix of 256×256 pixels without hardware magnification. High-resolution low-energy collimators were used. Results. In patients with verified diagnosis of malignant brain tumors, SPECT with [99mTc]Tc-1-THIO-D-glucose correctly visualized tumors in all cases. The tumor was visualized as a zone of increased accumulation of [99mTc]Tc-1-THIO-D-glucose of varying intensity and size. However, benign brain lesions did not show [99mTc]Tc-1-THIO-D-glucose uptake. Physiological accumulation of [99mTc]Tc-1-THIO-D-glucose was observed in soft tissues of the aponeurotic helmet, the choroid of the brain, the mucous membranes of the nasal cavity, and the sinuses of the skull bones. Pathological changes in the brain revealed by SPECT were confirmed by MRI with contrast enhancement. Conclusion. The study demonstrated a high efficiency of SPECT with [99mTc]Tc-1-THIO-D-glucose in visualization of malignant brain tumors. The sensitivity, specificity and accuracy of SPECT with [99mTc]Tc-1-THIO-D-glucose in the imaging of malignant brain tumors were 93–100 %, 65–100 %, 95–100 %, respectively. The data obtained suggest that [99mTc]Tc-1-THIO-D-glucose SPECT as an additional method for the detection of malignant brain tumors can increase access to radionuclides for this group of patients and improve the quality of cancer care.

Brain tumor visualization for magnetic resonance images using modified shape-based interpolation method

<span>3D visualization plays an essential role in medical diagnosis and setting treatment plans especially for brain cancer. There have been many attempts for brain tumor reconstruction and visualization using various techniques. However, this problem is still considered unsolved as more accurate results are needed in this critical field. In this paper, a sequence of 2D slices of brain magnetic resonance Images was used to reconstruct a 3D model for the brain tumor. The images were automatically segmented using a wavelet multi-resolution expectation maximization algorithm. Then, the inter-slice gaps were interpolated using the proposed modified shape-based interpolation method. The method involves three main steps; transferring the binary tumor images to distance images using a suitable distance function, interpolating the distance images using cubic spline interpolation and thresholding the interpolated values to get the reconstructed slices. The final tumor is then visualized as a 3D isosurface. We evaluated the proposed method by removing an original slice from the input images and interpolating it, the results outperform the original shape-based interpolation method by an average of 3% reaching 99% of accuracy for some slice images.</span>

Improved Protoporphyrin IX-Guided Neurosurgical Tumor Detection with Frequency-Domain Fluorescence Lifetime Imaging

Precise intraoperative brain tumor visualization supports surgeons in achieving maximal safe resection. In this sense, improved prognosis in patients with high-grade gliomas undergoing protoporphyrin IX fluorescence-guided surgery has been demonstrated. Phase fluorescence lifetime imaging in the frequency-domain has shown promise to distinguish weak protoporphyrin IX fluorescence from competing endogenous tissue fluorophores, thus allowing for brain tumor detection with high sensitivity. In this work, we show that this technique can be further improved by minimizing the crosstalk of autofluorescence signal contributions when only detecting the fluorescence emission above 615 nm. Combining fluorescence lifetime and spectroscopic measurements on a set of 130 ex vivo brain tumor specimens (14 low- and 56 high-grade gliomas, 39 meningiomas and 21 metastases) coherently substantiated the resulting increase of the fluorescence lifetime with respect to the detection band employed in previous work. This is of major interest for obtaining a clear-cut distinction from the autofluorescence background of the physiological brain. In particular, the median fluorescence lifetime of low- and high-grade glioma specimens lacking visual fluorescence during surgical resection was increased from 4.7 ns to 5.4 ns and 2.9 ns to 3.3 ns, respectively. While more data are needed to create statistical evidence, the coherence of what was observed throughout all tumor groups emphasized that this optimization should be taken into account for future studies.

Comprehensive exploration of long-wave emission carbon dots for brain tumor visualization

Carbon dot (CD)-based tumor imaging has been proven to be a reliable nanodiagnostic technique. Although abundant types of CDs have been developed, it is still a major challenge to synthesize long-wavelength CDs with high quality and superior repetition due to the complicated synthetic process. Here, stable long-wavelength red-light emission carbon dots (R-CDs) have been synthesized using appropriate carbon sources via a solvothermal method, which enables effective visualization of deep brain glioblastoma (GBM) by a liposome-formulated delivery system. The luminescence phenomenon and structural growth characteristics of R-CDs have been fully investigated and it has been found that R-CDs exhibit different optical behaviors in different pH and solvent environments. In vitro and in vivo models have proved their excellent cell targeting capacity, bioluminescence imaging potential, and biosafety for GBM visualization. Considering their stability and biocompatibility, the in-depth tissue imagining and other extensive applications of R-CDs are strongly recommended.

5-ALA in Suspected Low-Grade Gliomas: Current Role, Limitations, and New Approaches

Radiologically suspected low-grade gliomas (LGG) represent a special challenge for the neurosurgeon during surgery due to their histopathological heterogeneity and indefinite tumor margin. Therefore, new techniques are required to overcome these current surgical drawbacks. Intraoperative visualization of brain tumors with assistance of 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) fluorescence is one of the major advancements in the neurosurgical field in the last decades. Initially, this technique was exclusively applied for fluorescence-guided surgery of high-grade glioma (HGG). In the last years, the use of 5-ALA was also extended to other indications such as radiologically suspected LGG. Here, we discuss the current role of 5-ALA for intraoperative visualization of focal malignant transformation within suspected LGG. Furthermore, we discuss the current limitations of the 5-ALA technology in pure LGG which usually cannot be visualized by visible fluorescence. Finally, we introduce new approaches based on fluorescence technology for improved detection of pure LGG tissue such as spectroscopic PpIX quantification fluorescence lifetime imaging of PpIX and confocal microscopy to optimize surgery.

Intraoperative real-time near-infrared optical imaging for the identification of metastatic brain tumors via microscope and exoscope.

As chemotherapy and radiotherapy have developed, the role of a neurosurgeon in the treatment of metastatic brain tumors is gradually changing. Real-time intraoperative visualization of brain tumors by near-infrared spectroscopy (NIRS) is feasible. The authors aimed to perform real-time intraoperative visualization of the metastatic tumor in brain surgery using second-window indocyanine green (SWIG) with microscope and exoscope systems. Ten patients with intraparenchymal brain metastatic tumors were administered 5 mg/kg indocyanine green (ICG) 1 day before the surgery. In some patients, a microscope was used to help identify the metastases, whereas in the others, an exoscope was used. NIRS with the exoscope and microscope revealed the tumor location from the brain surface and the tumor itself in all 10 patients. The NIR signal could be detected though the normal brain parenchyma up to 20 mm. While the mean signal-to-background ratio (SBR) from the brain surface was 1.82 ± 1.30, it was 3.35 ± 1.76 from the tumor. The SBR of the tumor (p = 0.030) and the ratio of Gd-enhanced T1 tumor signal to normal brain (T1BR) (p = 0.0040) were significantly correlated with the tumor diameter. The SBR of the tumor was also correlated with the T1BR (p = 0.0020). The tumor was completely removed in 9 of the 10 patients, as confirmed by postoperative Gd-enhanced MRI. This was concomitant with the absence of NIR fluorescence at the end of surgery. SWIG reveals the metastatic tumor location from the brain surface with both the microscope and exoscope systems. The Gd-enhanced T1 tumor signal may predict the NIR signal of the metastatic tumor, thus facilitating tumor resection.

Comparison of Panitumumab-IRDye800CW and 5-Aminolevulinic Acid to Provide Optical Contrast in a Model of Glioblastoma Multiforme.

Maximal safe resection of malignant tissue is associated with improved progression-free survival and better response to radiation and chemotherapy for patients with glioblastoma (GBM). 5-Aminolevulinic acid (5-ALA) is the current FDA-approved standard for intraoperative brain tumor visualization. Unfortunately, autofluorescence in diffuse areas and high fluorescence in dense tissues significantly limit discrimination at tumor margins. This study is the first to compare 5-ALA to an investigational new drug, panitumumab-IRDye800CW, in the same animal model. A patient-derived GBM xenograft model was established in 16 nude mice, which later received injections of 5-ALA, panitumumab-IRDye800CW, IRDye800CW, 5-ALA and IRDye800CW, or 5-ALA and panitumumab-IRDye800CW. Brains were prepared for multi-instrument fluorescence imaging, IHC, and quantitative analysis of tumor-to-background ratio (TBR) and tumor margin accuracy. Statistical analysis was compared with Wilcoxon rank-sum or paired t test. Panitumumab-IRDye800CW had a 30% higher comprehensive TBR compared with 5-ALA (P = 0.0079). SDs for core and margin regions of interest in 5-ALA-treated tissues were significantly higher than those found in panitumumab-IRDye800CW-treated tissues (P = 0.0240 and P = 0.0284, respectively). Panitumumab-IRDye800CW specificities for tumor core and margin were more than 10% higher than those of 5-ALA. Higher AUC for panitumumab-IRDye800CW indicated strong capability to discriminate between normal and malignant brain tissue when compared with 5-ALA. This work demonstrates that panitumumab-IRDye800CW shows potential as a targeting agent for fluorescence intraoperative detection of GBM. Improved margin definition and surgical resection using panitumumab-IRDye800 has the potential to improve surgical outcomes and survival in patients with GBM compared with 5-ALA.

Blood-Brain Barrier, Blood-Brain Tumor Barrier, and Fluorescence-Guided Neurosurgical Oncology: Delivering Optical Labels to Brain Tumors.

Recent advances in maximum safe glioma resection have included the introduction of a host of visualization techniques to complement intraoperative white-light imaging of tumors. However, barriers to the effective use of these techniques within the central nervous system remain. In the healthy brain, the blood-brain barrier ensures the stability of the sensitive internal environment of the brain by protecting the active functions of the central nervous system and preventing the invasion of microorganisms and toxins. Brain tumors, however, often cause degradation and dysfunction of this barrier, resulting in a heterogeneous increase in vascular permeability throughout the tumor mass and outside it. Thus, the characteristics of both the blood-brain and blood-brain tumor barriers hinder the vascular delivery of a variety of therapeutic substances to brain tumors. Recent developments in fluorescent visualization of brain tumors offer improvements in the extent of maximal safe resection, but many of these fluorescent agents must reach the tumor via the vasculature. As a result, these fluorescence-guided resection techniques are often limited by the extent of vascular permeability in tumor regions and by the failure to stain the full volume of tumor tissue. In this review, we describe the structure and function of both the blood-brain and blood-brain tumor barriers in the context of the current state of fluorescence-guided imaging of brain tumors. We discuss features of currently used techniques for fluorescence-guided brain tumor resection, with an emphasis on their interactions with the blood-brain and blood-tumor barriers. Finally, we discuss a selection of novel preclinical techniques that have the potential to enhance the delivery of therapeutics to brain tumors in spite of the barrier properties of the brain.

Near-infrared intraoperative molecular imaging with conventional neurosurgical microscope can be improved with narrow band "boost" excitation.

Intraoperative visualization of brain tumors with near-infrared (NIR)-fluorescent dyes is an emerging method for tumor margin approximation but are limited by existing fluorescence detection platforms. We previously showed that a dedicated NIR imaging platform outperformed a state-of-the-art neurosurgical microscope in fluorescence signal characteristics. This study examined whether conventional neurosurgical microscope NIR signal could be improved with the addition of a narrow wavelength excitation source. Imaging was conducted with a broad-spectrum neurosurgical microscope and commercial near-infrared module. Addition of an 805-nm laser was used to "boost" NIR excitation of indocyanine green (ICG). In vitro quantification was performed on serial dilutions of ICG. Patients underwent tumor resection with delayed 24-h imaging of ICG infusion. NIR fluorescence of dura, cortex, or tumor was quantified from images prior to (pre-boost) and following added excitation with the laser (post-boost). Signal to background ratio (SBR) of pre- and post-boost was calculated as a readout of image enhancement. In vitro, excitation boost effected a 29% increase in mean SBR in six serial dilutions of ICG. Intraoperative boost was performed in 11 patients including meningioma, glioblastoma multiforme, and metastases. Increase in tumor fluorescence was pronounced under direct tumor visualization. Across all patients, boost excitation resulted in 35% mean improvement from pre-boost SBR (p < 0.001). Neurosurgical microscopes remain the preferred method of visualizing tumor during intracranial surgery. However, current modalities for NIR signal detection are suboptimal. We demonstrate that augmentation of a fluorescence microscope module with a focused excitation source is a simple mechanism of improving NIR tumor visualization. NCT03262636.

3D Visualization of Brain Tumors Using MR Images: A Survey.

Three-Dimensional visualization of brain tumors is very useful in both diagnosis and treatment stages of brain cancer. It helps the oncologist/neurosurgeon to take the best decision in Radiotherapy and/or surgical resection techniques. 3D visualization involves two main steps; tumor segmentation and 3D modeling. In this article, we illustrate the most widely used segmentation and 3D modeling techniques for brain tumors visualization. We also survey the public databases available for evaluation of the mentioned techniques.

Augmented Reality Based Brain Tumor 3D Visualization

In this paper we present an augmented reality system for mobile devices that facilitates 3D brain tumor visualization in real time. The system uses facial features to track the subject in the scene. The system performs camera calibration based on the face size of the subject, instead of the common approach of using a number of chessboard images to calibrate the camera every time the application is installed on a new device. Camera 3D pose estimation is performed by finding its position and orientation based on a set of 3D points and their corresponding 2D projections. According to the estimated camera pose, a reconstructed brain tumor model is displayed at the same location as the subject’s real anatomy. The results of our experiment show the system was successful in performing the brain tumor augmentation in real time with a reprojection accuracy of 97%.

Current Progresses in Developing PET Radiopharmaceuticals for Patients in the Czech Republic

In Masaryk Memorial Cancer Institute (MMCI), there is a long-running intensive joint effort of the RECAMO project and commercial entities, involving mainly clinical evaluations of state-of-the-art PET radiopharmaceuticals leading to their future availability for Czech physicians and their patients. Recently, the PET tracers [11C]methionine and [18F]fluorocholine, among others, were developed in this cooperation, both of them tracers with high importance for oncologic positron emission tomography diagnostics. [11C]methionine, labeled by carbon-11 with a half-life of 20 min, is a proteosynthesis marker used primarily for brain tumor visualization, whereas [18F]fluorocholine, labeled by fluorine-18 with a half-life of 109 min, is a marker of synthesis of cellular membranes and cell proliferation, its primary use being PET diagnostics of prostate carcinoma.The results of clinical evaluations of both PET radiopharmaceuticals, performed on the basis of parameters agreed and approved beforehand in cooperation of MMCI, RECAMO and the manufacturer of said radiopharmaceuticals, aimed to prove the efficiency and suitability of both compounds for oncologic PET diagnostics for said tumors. In both cases, the radiopharmaceuticals were evaluated in regard to their major use.The obtained results prove the benefits and efficiency of both compounds in PET diagnostics of respective tumors. The results, in the form of clinical evaluation reports, will be used as part of the documentation required for marketing authorization of these compounds for use in the Czech Republic.Key words: positron emission tomography - radiopharmaceuticals - L-methyl-11C-methionine - 18F-fluorocholineThis work was supported by the project MEYS - NPS I - LO1413.The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study.The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 10. 6. 2016Accepted: 17. 6. 2016.

Synthesis and Biological Evaluation of an (18)Fluorine-Labeled COX Inhibitor--[(18)F]Fluorooctyl Fenbufen Amide--For Imaging of Brain Tumors.

Molecular imaging of brain tumors remains a great challenge, despite the advances made in imaging technology. An anti-inflammatory compound may be a useful tool for this purpose because there is evidence of inflammatory processes in brain tumor micro-environments. Fluorooctylfenbufen amide (FOFA) was prepared from 8-chlorooctanol via treatment with potassium phthalimide, tosylation with Ts2O, fluorination with KF under phase transfer catalyzed conditions, deprotection using aqueous hydrazine, and coupling with fenbufen. The corresponding radiofluoro product [18F]FOFA, had a final radiochemical yield of 2.81 mCi and was prepared from activated [18F]F− (212 mCi) via HPLC purification and concentration. The radiochemical purity was determined to be 99%, and the specific activity was shown to exceed 22 GBq/μmol (EOS) based on decay-corrected calculations. Ex-vivo analysis of [18F]FOFA in plasma using HPLC showed that the agent had a half-life of 15 min. PET scanning showed significant accumulation of [18F]FOFA over tumor loci with reasonable contrast in C6-glioma bearing rats. These results suggest that this molecule is a promising agent for the visualization of brain tumors. Further investigations should focus on tumor micro-environments.

Near-infrared fluorescence heptamethine carbocyanine dyes mediate imaging and targeted drug delivery for human brain tumor

Brain tumors and brain metastases are among the deadliest malignancies of all human cancers, largely due to the cellular blood–brain and blood–tumor barriers that limit the delivery of imaging and therapeutic agents from the systemic circulation to tumors. Thus, improved strategies for brain tumor visualization and targeted treatment are critically needed. Here we identified and synthesized a group of near-infrared fluorescence (NIRF) heptamethine carbocyanine dyes and derivative NIRF dye-drug conjugates for effective imaging and therapeutic targeting of brain tumors of either primary or metastatic origin in mice, which is mechanistically mediated by tumor hypoxia and organic anion-transporting polypeptide genes. We also demonstrate that these dyes, when conjugated to chemotherapeutic agents such as gemcitabine, significantly restricted the growth of both intracranial glioma xenografts and prostate tumor brain metastases and prolonged survival in mice. These results show promise in the application of NIRF dyes as novel theranostic agents for the detection and treatment of brain tumors.

Preoperative Detection and Intraoperative Visualization of Brain Tumors for More Precise Surgery: A New Dual-Modality MRI and NIR Nanoprobe.

In clinical practice, it is difficult to identify tumor margins during brain surgery due to its inherent infiltrative character. Herein, a unique dual-modality nanoprobe (Gd-DOTA-Ag2S QDs, referred as Gd-Ag2S nanoprobe) is reported, which integrates advantages of the deep tissue penetration of enhanced magnetic resonance (MR) imaging of Gd and the high signal-to-noise ratio and high spatiotemporal resolution of fluorescence imaging in the second near-infrared window (NIR-II) of Ag2S quantum dots (QDs). Due to the abundant tumor angiogenesis and the enhanced permeability and retention effect in the tumor, a brain tumor (U87MG) in a mouse model is clearly delineated in situ with the help of the Gd assisted T1 MR imaging and the intraoperative resection of the tumor is precisely accomplished under the guidance of NIR-II fluorescence imaging of Ag2S QDs after intravenous injection of Gd-Ag2S nanoprobe. Additionally, no histologic changes are observed in the main organs of the mouse after administration of Gd-Ag2S nanoprobe for 1 month, indicating the high biocompatibility of the nanoprobe. We expect that such a novel "Detection and Operation" strategy based on Gd-Ag2S nanoprobe is promising in future clinical applications.

Photodynamic therapy: a review of applications in neurooncology and neuropathology.

Photodynamic therapy (PDT) effect is a promising adjuvant modality for diagnosis and treatment of brain cancer. It is of importance that the bright fluorescence of most photosensitizers provides visualization of brain tumors. This is successfully used for fluorescence-guided tumor resection according the principle to see and treat. Non-oncologic application of PDT effect for induction of photothrombotic infarct of the brain tissue is a well-controlled and reproducible stroke model, in which a local brain lesion is produced in the predetermined brain area. Since normal neurons and glial cells may also be damaged by PDT and this can lead unwanted neurological consequences, PDT effects on normal neurons and glial cells should be comprehensively studied. We overviewed the current literature data on the PDT effect on a range of signaling and epigenetic proteins that control various cell functions, survival, necrosis, and apoptosis. We hypothesize that using cell-specific inhibitors or activators of some signaling proteins, one can selectively protect normal neurons and glia, and simultaneously exacerbate photodynamic damage of malignant gliomas. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE) (DOI:

Intraoperative visualization of brain tumors with 5-aminolevulinic acid-induced fluorescence

Precise histopathological diagnosis of brain tumors is essential for the correct patient management. Furthermore, complete resection of brain tumors is associated with an improved patient prognosis. However, histopathological undergrading and incomplete tumor removal are not uncommon, especially due to insufficient intra-operative visualization of brain tumor tissue. The fluorescent dye 5-aminolevulinic acid (5-ALA) is currently applied for fluorescence-guided resections of high-grade gliomas. The value of 5-ALA-induced protoporphyrin (PpIX) fluorescence for intra-operative visualization of other tumors than high-grade gliomas remains unclear. Within the frame of this thesis, we found a significantly higher rate of complete resections of our high-grade gliomas as compared to control cases by using the newly established 5-ALA fluorescence technology at our department. Additionally, we showed that MRI spectroscopy-based chemical shift imaging (CSI) is capable to identify intratumoral high-grade glioma areas (= anaplastic foci) during navigation guided resections to avoid histopathological undergrading. However, the accuracy of navigation systems with integrated pre-operative imaging data such as CSI declines during resections due to intra-operative brainshift. In two further studies, we found that 5-ALA induced PpIX fluorescence is capable as a novel intra-operative marker to detect anaplastic foci within initially suspected low-grade gliomas independent of brainshift. Finally, we showed that the application of 5-ALA is also of relevance in needle biopsies for intra-operative identification of representative brain tumor tissue. These data indicate that 5-ALA is not only of major importance for resection of high-grade gliomas, but also for intra-operative visualization of anaplastic foci as well as representative brain tumor tissue in needle biopsies unaffected by brainshift. Consequently, this new technique might become a novel standard in brain tumor surgery that optimizes the patient management and improves the patient prognosis by maximizing the extent of tumor resection and enabling a precise histopathological tumor diagnosis.

Engineered knottin peptide enables noninvasive optical imaging of intracranial medulloblastoma

Central nervous system tumors carry grave clinical prognoses due to limited effectiveness of surgical resection, radiation, and chemotherapy. Thus, improved strategies for brain tumor visualization and targeted treatment are critically needed. We demonstrate that mouse cerebellar medulloblastoma (MB) can be targeted and illuminated with a fluorescent, engineered cystine knot (knottin) peptide that binds with high affinity to αvβ3, αvβ5, and α5β1 integrin receptors. This integrin-binding knottin peptide, denoted EETI 2.5F, was evaluated as a molecular imaging probe in both orthotopic and genetic models of MB. Following tail vein injection, fluorescence arising from dye-conjugated EETI 2.5F was localized to the tumor compared with the normal surrounding brain tissue, as measured by optical imaging. The imaging signal intensity correlated with tumor volume. Due to its unique ability to bind to α5β1 integrin, EETI 2.5F showed superior in vivo and ex vivo brain tumor imaging contrast compared with other engineered integrin-binding knottin peptides and with c(RGDfK), a well-studied integrin-binding peptidomimetic. Next, EETI 2.5F was fused to an antibody fragment crystallizable (Fc) domain (EETI 2.5F-Fc) to determine if a larger integrin-binding protein could also target intracranial brain tumors. EETI 2.5F-Fc, conjugated to a fluorescent dye, illuminated MB following i.v. injection and was able to distribute throughout the tumor parenchyma. In contrast, brain tumor imaging signals were not detected in mice injected with EETI 2.5F proteins containing a scrambled integrin-binding sequence, demonstrating the importance of target specificity. These results highlight the potential of using EETI 2.5F and EETI 2.5-Fc as targeted molecular probes for brain tumor imaging.