Integration of functional brain information into stereotactic irradiation treatment planning using magnetoencephalography and magnetic resonance axonography

Predicting progression-free survival using dynamic contrast-enhanced imaging-based radiomics in advanced nasopharyngeal carcinoma patients treated with nimotuzumab

PURPOSE

The purpose of this study was to explore the potential value of the radiomics model based on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), compared with the clinical model mostly based on the epidermal growth factor receptor (EGFR) expression, in predicting progression-free survival (PFS) in patients with locally advanced nasopharyngeal carcinoma (LA-NPC) treated with nimotuzumab (NTZ).

METHODS

A total of 136 patients with LA-NPC who received NTZ treatment between January 2018 and June 2022 were included in this study. Patients were randomly divided into training (n = 95) and validation (n = 41) groups in a 7:3 ratio. DCE-MRI radiomics, clinical, and clinical-radiomics models were built to predict PFS. The relationship between EGFR expression levels and NTZ efficacy was assessed using Kaplan-Meier curves. Model performance was assessed using the area under the curve, calibration, and DeLong tests. Decision curve analysis evaluated net clinical benefit. Patients were stratified into high- and low-risk groups based on optimal model radiomic scores, and prognoses were compared using Kaplan-Meier curves.

RESULTS

Univariate Cox regression analysis demonstrated that EGFR expression level was the only independent predictive factor of PFS (p < 0.05). Patients with EGFR 3+ receiving NTZ therapy had significantly longer PFS than those with EGFR 1+ (hazard ratio = 3.025, p < 0.05). The clinical-radiomics model exhibited superior predictive efficacy, compared with the radiomics and clinical models (training set: 0.887 vs. 0.845, 0.654; validation set: 0.831, 0.824 vs. 0.567, all p < 0.001).

CONCLUSIONS

The clinical-radiomics models using DCE-MRI and EGFR levels can effectively predict NTZ efficacy in LA-NPC patients, providing objective evidence for personalized treatment adjustments.

KEY POINTS

Question How can the response to nimotuzumab treatment in patients with locally advanced nasopharyngeal carcinoma be accurately predicted using non-invasive imaging methods? Findings A combined clinical and radiomic model using dynamic contrast-enhanced magnetic resonance imaging showed improved predictive performance for progression-free survival in patients treated with nimotuzumab. Clinical relevance The study provides evidence for using a combined clinical and radiomic approach, offering a non-invasive method to predict treatment response and guide personalized treatment strategies for patients with locally advanced nasopharyngeal carcinoma, potentially improving patient outcomes.

OAR sparing 3D radiotherapy planning supported by fMRI brain mapping investigations

The human brain as an organ has numerous functions; some of them can be visualized by functional imaging techniques (e.g., functional MRI [fMRI] or positron emission tomography). The localization of the appropriate activity clusters requires sophisticated instrumentation and complex measuring protocol. As the inclusion of the activation pattern in modern self-tailored 3D based radiotherapy has notable advantages, this method is applied frequently. Unfortunately, no standardized method has been published yet for the integration of the fMRI data into the planning process and the detailed description of the individual applications is usually missing. Thirteen patients with brain tumors, receiving fMRI based RT planning were enrolled in this study. The delivered dose maps were exported from the treatment planning system and processed for further statistical analysis. Two parameters were introduced to measure the geometrical distance Hausdorff Distance (HD), and volumetric overlap Dice Similarity Coefficient (DSC) of fMRI corrected and not corrected dose matrices as calculated by 3D planning to characterize similarity and/or dissimilarity of these dose matrices. Statistical analysis of bootstrapped HD and DSC data was performed to determine confidence intervals of these parameters. The calculated confidence intervals for HD and DSC were (5.04, 7.09), (0.79, 0.86), respectively for the 40 Gy and (5.2, 7.85), (0.74, 0.83), respectively for the 60 Gy dose volumes. These data indicate that in the case of HD < 5.04 and/or DSC > 0.86, the 40 Gy dose volumes obtained with and without fMRI activation pattern do not show a significant difference (5% significance level). The same conditions for the 60 Gy dose volumes were HD < 5.2 and/or DSC > 0.83. At the same time, with HD > 7.09 and/or DSC < 0.79 for 40 Gy and HD > 7.85 and/or DSC < 0.74 for 60 Gy the impact of fMRI utilization in RT planning is excessive. The fMRI activation clusters can be used in daily RT planning routine to spare activation clusters as critical areas in the brain and avoid their high dose irradiation. Parameters HD (as distance) and DSC (as overlap) can be used to characterize the difference and similarity between the radiotherapy planning target volumes and indicate whether the fMRI delivered activation patterns and consequent fMRI corrected planning volumes are reliable or not.

The Feasibility of Integrating Resting-State fMRI Networks into Radiotherapy Treatment Planning

BACKGROUND

Functional magnetic resonance imaging (fMRI) presents the ability to selectively protect functionally significant regions of the brain when primary brain tumors are treated with radiation therapy. Previous research has focused on task-based fMRI of language and sensory networks; however, there has been limited investigation on the inclusion of resting-state fMRI into the design of radiation treatment plans.

METHODS AND MATERIALS

In this pilot study of 9 patients with primary brain tumors, functional data from the default mode network (DMN), a network supporting cognitive functioning, was obtained from resting-state fMRI and retrospectively incorporated into the design of radiation treatment plans. We compared the dosimetry of these fMRI DMN avoidance treatment plans with standard of care treatment plans to demonstrate feasibility. In addition, we used normal tissue complication probability models to estimate the relative benefit of fMRI DMN avoidance treatment plans over standard of care treatment plans in potentially reducing memory loss, a surrogate for cognitive function.

RESULTS

On average, we achieved 20% (P = 0.002) and 12% (P = 0.002) reductions in the mean and maximum doses, respectively, to the DMN without compromising the dose coverage to the planning tumor volume or the dose-volume constraints to organs at risk. Normal tissue complication probability models revealed that when the fMRI DMN was considered during radiation treatment planning, the probability of developing memory loss was lowered by more than 20%.

CONCLUSION

In this pilot study, we demonstrated the feasibility of including rs-MRI data into the design of radiation treatment plans to spare cognitively relevant brain regions during radiation therapy. These results lay the groundwork for future clinical trials that incorporate such treatment planning methods to investigate the long-term behavioral impact of this reduction in dose to the cognitive areas and their neural networks that support cognitive performance.

The Role of Navigated Transcranial Magnetic Stimulation Motor Mapping in Adjuvant Radiotherapy Planning in Patients With Supratentorial Brain Metastases

Purpose: In radiotherapy (RT) of brain tumors, the primary motor cortex is not regularly considered in target volume delineation, although decline in motor function is possible due to radiation. Non-invasive identification of motor-eloquent brain areas is currently mostly restricted to functional magnetic resonance imaging (fMRI), which has shown to lack precision for this purpose. Navigated transcranial magnetic stimulation (nTMS) is a novel tool to identify motor-eloquent brain areas. This study aims to integrate nTMS motor maps in RT planning and evaluates the influence on dosage modulations in patients harboring brain metastases.

Materials and Methods: Preoperative nTMS motor maps of 30 patients diagnosed with motor-eloquent brain metastases were fused with conventional planning imaging and transferred to the RT planning software. RT plans of eleven patients were optimized by contouring nTMS motor maps as organs at risk (OARs). Dose modulation analyses were performed using dose-volume histogram (DVH) parameters.

Results: By constraining the dose applied to the nTMS motor maps outside the planning target volume (PTV) to 15 Gy, the mean dose (Dmean) to the nTMS motor maps was significantly reduced by 18.1% from 23.0 Gy (16.9–30.4 Gy) to 18.9 Gy (13.5–28.8 Gy, p < 0.05). The Dmean of the PTV increased by 0.6 ± 0.3 Gy (1.7%).

Conclusion: Implementing nTMS motor maps in standard RT planning is feasible in patients suffering from intracranial metastases. A significant reduction of the dose applied to the nTMS motor maps can be achieved without impairing treatment doses to the PTV. Thus, nTMS might provide a valuable tool for safer application of RT in patients harboring motor-eloquent brain metastases.

Integrating functional MRI information into conventional 3D radiotherapy planning of CNS tumors. Is it worth it?

The purpose of our study was to examine the potential benefits of integrating functional MRI (fMRI) information into the 3D-based planning process for central nervous system (CNS) malignancies. Between 01.01.2008 and 01.12.2009, ten patients with astrocytoma (both low and high-grade histological type) were enrolled in this study. Before the planning process, conventional CT planning, postoperative MR, and individual functional MRI examinations were conducted. For the functional MRI examination four types of conventional stimuli were applied: acoustic, visual, somatosensory, and numeric. To examine the potential benefits of using fMRI-based information, three different types of theoretical planning were applied and compared: 3D conformal plan without fMRI information, 3D conformal plan with fMRI information, and IMRT plan with fMRI information. DVH analysis and the NTCP model were used for plan comparison. When comparing planning methods, distance-related subgroups were generated and studied. By using the additional fMRI information, a significantly higher sparing effect can be achieved on these ORs (both with conventional 3D-based planning and IMRT). In cases when the OR-PTV distance is less than 1 cm, IMRT seems to be a significantly better choice than conventional 3D-based techniques. IMRT also has an additional sparing effect on the optic tract and brainstem, especially for locations close to the midline. Our results demonstrated that using fMRI information in conventional 3D-based treatment planning has the potential benefit of significant dose reduction for the critical organs, with no compromise in PTV coverage even when using conventional 3D planning. fMRI can be widely used in low-grade cases (long life expectancy, lower acute and late toxicity) and also in cases with high-grade astrocytomas or distant metastases (higher dose to PTV with better sparing of risk organs). In cases when the OR-PTV distance is less than 1 cm, IMRT should be the choice of treatment for a higher sparing effect on functional active areas. Longer imaging and clinical follow up are needed to confirm the real sparing effect on these functional areas.

Integrating functional MRI information into radiotherapy planning of CNS tumors-early experiences

The purpose of our study was to examine the integration of functional MRI (fMRI) information into 3D based planning process of the central nervous system (CNS) malignancies. Between 01.01.2008 and 01.12.2008 four patients with astrocytoma were enrolled to this study. Before the planning process conventional planning CT, postoperative MR and individual functional MRI examinations were delivered. For the functional MRI examination the following four types of stimulus were applied: acoustic, visual, somatosensory and numeral. Three different theoretical planning situations were applied and compared: 3D conformal plan without fMRI information, 3D conformal plan with fMRI information and IMRT plan with fMRI information. For plan comparison DVH analysis, and NTCP model were used. fMRI based OR definition resulted in 4 additional OR's in the contouring process. As these cases demonstrate, an average of 50% dose reduction was achieved in OR, OR2 and OR3 with IMRT and fMRI based 3D planning, especially in case of midline localization and big tumor extent. IMRT provides additional sparing effect in the optic tract and brainstem, especially for localizations close to the midline. Our results demonstrated that using fMRI information in conventional 3D based treatment planning potentially benefits significant dose reduction in critical organs, with no compromise in PTV coverage. fMRI can be widely used even in low grade cases (long life expectancies, lower acute and late toxicity in radiotherapy) and in cases with high grade astrocytomas or metastases (higher dose to PTV with better risk organ sparing in radiotherapy).

Functional MRI for Radiotherapy of Gliomas

In this paper, we review the applications of functional magnetic resonance imaging (MRI) for target delineation and critical organ avoidance for brain radiotherapy. In this article we distinguish functional MRI from brain functional MRI (fMRI). Functional MRI includes magnetic resonance spectroscopic imaging (MRSI), perfusion MRI, diffusion tensor imaging (DTI) and brain fMRI. These functional MRI modalities can provide unique metabolic, pathological and physiological information that are not available in anatomic MRI and can potentially improve the treatment outcomes of brain tumors. For example, both choline (Cho) to N-acetylaspartate (NAA) and Cho to creatine (Cr) ratios from MRSI increase with increasing tumor malignancy and can be used to grade gliomas. Relative cerebral blood volume (rCBV) measurements from dynamic susceptibility contrast perfusion magnetic resonance imaging (DSC MRI) are superior to conventional contrast-enhanced MRI in predicting tumor biology and may be even superior to pathologic assessment in predicting patient clinical outcomes. Brain fMRI can help identify and avoid functionally critical areas when constructing treatment plans for brain radiotherapy. In the past, functional MRI measurements have not been routinely used in a clinical arena due to the experimental nature of these imaging modalities. As these methods become more commonly used and effective image co-registration algorithms become available, integration of functional MRI into the treatment process of brain radiotherapy now appears to be clinically feasible, at least in major medical centers.

Early results of CyberKnife radiosurgery for arteriovenous malformations

Object

The authors describe a method that utilizes an image-guided robotic radiosurgical apparatus (the CyberKnife) for treatment of cerebral arteriovenous malformations (AVMs). This procedure required the development of an original technique that allows a high degree of automation.

Methods

Angiographic images were imported into the treatment planning software by coregistering CT and 3D rotational angiography. The nidus contour was delineated using the contouring tools of the treatment planning system. Functional MR imaging was employed for contouring critical cortical regions, such as the motor cortex and language areas. Once the radiation dose to be delivered to the target volume and dose constraints to critical structures were prescribed, the inverse treatment planning function determined the optimal treatment plan.

Results

A series of 279 patients with cerebral AVMs underwent CyberKnife radiosurgery. One transitory adverse effect of the radiation procedure was observed. Eight bleeding occurrences were noted before complete AVM obliteration. Of the 102 patients with follow-up > 36 months, 80 underwent angiographic evaluation. In this group, 65 patients (81.2%) showed complete angiographic obliteration of their AVM. In 8 more patients, complete angiographic obliteration was demonstrated by MR angiography only.

Conclusions

This is the first report describing a technique developed for CyberKnife radiosurgery of cerebral AVMs. The use of different imaging modalities for automatic delineation of the target and critical structures combined with the employment of the inverse treatment planning capability is the crucial point of the procedure. The procedure proved to be safe and efficient.

Biologically conformal treatment: biomarkers and functional imaging in radiation oncology

'Conformal radiation therapy' is the standard of care in radiation oncology, referring to the process of shaping the radiation beam to precisely match a tumor's physical dimensions. We describe 'biologically conformal radiotherapy', in which the radiation oncologist matches the prescribed treatment to a tumor's biological characteristics and the host's predicted tolerance of radiation. This paradigm emphasizes that not all tumors are equally sensitive to radiation; conversely, some patients are especially susceptible to radiation's side effects. Patients bearing radioresistant tumors or those prone to toxicity may be best treated with the incorporation of targeted radiation modulators or, in extreme cases, by a different modality. The biological characteristics of tumors can be assessed by a wide range of techniques: functional imaging (positron emission tomography and advanced magnetic resonance imaging), single gene/protein molecular techniques and 'omic' technologies. This paper reviews the latest advances in the use of biomarkers and functional imaging in guiding patients to receive the most appropriate treatment.

Feasibility study of intensity-modulated radiotherapy (IMRT) treatment planning using brain functional MRI

The purpose of this work was to study the feasibility of incorporating functional magnetic resonance imaging (fMRI) information for intensity modulated radiotherapy (IMRT) treatment planning of brain tumors. Three glioma patients were retrospectively replanned for radiotherapy (RT) with additional fMRI information. The fMRI of each patient was acquired using a bilateral finger-tapping paradigm with a gradient echo EPI (Echo Planer Imaging) sequence. The fMRI data were processed using the Analysis of Functional Neuroimaging (AFNI) software package for determining activation volumes, and the volumes were fused with the simulation computed tomography (CT) scan. The actived pixels in left and right primary motor cortexes (PMCs) were contoured as critical structures for IMRT planning. The goal of replanning was to minimize the RT dose to the activation volumes in the PMC regions, while maintaining a similar coverage to the planning target volume (PTV) and keeping critical structures within accepted dose tolerance. Dose-volume histograms of the treatment plans with and without considering the fMRI information were compared. Beam angles adjustment or additional beams were needed for 2 cases to meet the planning criteria. Mean dose to the contralateral and ipsilateral PMC was significantly reduced by 66% and 55%, respectively, for 1 patient. For the other 2 patients, mean dose to contralateral PMC region was lowered by 73% and 69%. In general, IMRT optimization can reduce the RT dose to the PMC regions without compromising the PTV coverage or sparing of other critical organs. In conclusion, it is feasible to incorporate the fMRI information into the RT treatment planning. IMRT planning allows a significant reduction in RT dose to the PMC regions, especially if the region does not lie within the PTV.

New developments in MRI for target volume delineation in radiotherapy

MRI is being increasingly used in oncology for staging, assessing tumour response and also for treatment planning in radiotherapy. Both conformal and intensity-modulated radiotherapy requires improved means of defining target volumes for treatment planning in order to achieve its intended benefits. MRI can add to the radiotherapy treatment planning (RTP) process by providing excellent and improved characterization of soft tissues compared with CT. Together with its multiplanar capability and increased imaging functionality, these advantages for target volume delineation outweigh its drawbacks of lacking electron density information and potential image distortion. Efficient MR distortion assessment and correction algorithms together with image co-registration and fusion programs can overcome these limitations and permit its use for RTP. MRI developments using new contrast media, such as ultrasmall superparamagnetic iron oxide particles for abnormal lymph node identification, techniques such as dynamic contrast enhanced MRI and diffusion MRI to better characterize tissue and tumour regions as well as ultrafast volumetric or cine MR sequences to define temporal patterns of target and organ at risk deformity and variations in spatial location have all increased the scope and utility of MRI for RTP. Information from these MR developments may permit treatment individualization, strategies of dose escalation and image-guided radiotherapy. These developments will be reviewed to assess their current and potential use for RTP and precision high dose radiotherapy.

[Image registration for radiation therapy: Practical aspects and quality control]

The development of conformal radiotherapy techniques (CRT) and intensity modulated CRT requires an accurate delineation of target structures and organs at risk. Thus, additional information provided by anatomical and/or functional imaging modalities can be used for volume of interest determination combined with traditionally used Computed Tomography imaging (CT): for instance, functional or morphological Magnetic Resonance Imaging (f MRI or m MRI) or Positron Emission Tomography (PET). A prerequisite to the simultaneous use of this information is image registration. Due to the differences between the images and the information they provide, a quality control of image registration process for radiotherapy is mandatory. The purpose of this article is to present the difficulties in implementing such controls and to show the necessity for a clinical validation on patient's images. The last part of this work presents the possible interest in using f MRI to help radio-oncologists in the treatment planning for gliomas associated to image coregistration and quality control considerations.

Functional magnetic resonance imaging for defining the biological target volume

Morphology as demonstrated by CT is the basis for radiotherapy planning. Intensity-modulated and adaptive radiotherapy techniques would greatly benefit from additional functional information allowing for definition of the biological target volume. MRI techniques include several which can characterize and quantify different tissue properties and their tumour-related changes. Results of perfusion MRI represent microvascular density and permeability; MR spectroscopy depicts particular metabolites; diffusion weighted imaging shows tissue at risk and tumour cellularity; while dynamic 3D acquisition (4D MRI) shows organ motion and the mobility of tumours within them.

Pediatric Magnetoencephalography and Magnetic Source Imaging

Magnetoencephalography (MEG) and magnetic source imaging (MSI) together represent a uniquely powerful functional imaging modality because of their capabilities of directly observing the electrophysiologic activity of neurons with exquisite temporal detail and accurately localizing corresponding neuromagnetic field sources onto high-resolution MR images. These features have and should continue to advance our understanding of the complex spatiotemporal basis of normal and abnormal brain function and development in children. By more clearly delineating and characterizing epileptogenic foci and their relation to eloquent cortex, MSI enables earlier and more effective neurosurgery to be performed, thus resulting in improved seizure outcomes. Although MEG and MSI cannot replace scalp electroencephalography, neuropsychologic testing, and the need for meticulous intraoperative cortical mapping in patients undergoing excision of epileptogenic lesions, their increasing availability should ultimately persuade many clinicians of their key, if not essential, role in the evaluation and treatment of children with epilepsy.

[Analysis of target volumes for gliomas]

Gliomas are the most frequent tumors of the central nervous system of the adult. These intraparenchymal tumors are infiltrative and the most important criterion for definition of GTV and CTV is the extent of infiltration. Delineation of GTV and CTV for untreated and resected glioma remains a controversial and difficult issue because of the discrepancy between real tumor invasion and that estimated by CT or MRI. Is particularly helpful a joint analysis of the four different methods as histopathological correlations with CT and MRI, use of new modality imaging, pattern of relapses after treatment and interobserver studies. The presence of isolated tumor cells in intact brain, oedema or adjacent structures requires the definition of two different options for CTV: i) a geometrical option with GTV defined as the tumor mass revealed by the contrast-enhanced zone on CT or MRI and a CTV with an expanded margin of 2 or 3 cm; ii) an anatomic option including the entire zone of oedema or isolated tumor cell infiltration extending at least as far as the limits of the hyperintense zone on T2-weighted MRI. Inclusion of adjacent structures (such as white matter, corpus callosum, subarachnoid spaces) in the CTV mainly depends on the site of the tumor and size of the volume is generally enlarged.

Target Definition in the Thorax and Central Nervous System

It is the aim of conformal radiotherapy to restrict the high-dose region to the target volume as much as possible, thereby sparing the neighboring healthy tissues. However, to increase the therapeutic range, smaller margins tend to be used. This reduction of safety margins enhances the risk of unsuitable dosage because of mistaken target definition. Central nervous system (CNS) and lung cancers constitute sites that are particularly difficult to irradiate combining a large number of conceptual difficulties, allowing them to be considered as 2 particularly interesting study models. Imaging occupies an increasingly important place in these 2 types of tumors, especially with the development of new radiotherapy techniques. CNS and lung cancers represent an example of clinicopathological correlations. More specifically, CNS cancers represent an excellent model for estimation of new 3-dimensional navigational systems. For lung cancer, there is a combination of ballistic difficulties because of respiratory motion, the number and low tolerance of neighboring organs, and dosimetric difficulties because of the presence of inhomogeneities. This article reviews the main currently accepted criteria of choice justifying the size of gross tumor volume and clinical target volume margins for lung and CNS cancers.

Update of stereotactic radiosurgery for brain tumors

PURPOSE OF REVIEW

This paper will review the recent publications of stereotactic radiosurgery for brain tumors.

RECENT ADVANCES

Despite its controversial beginning, stereotactic radiosurgery has rapidly gained acceptance among neurosurgeons, radiation oncologists, and neuro-oncologists as a valuable treatment option for patients with certain benign and malignant brain tumors. Over the past year, a number of publications have confirmed the efficacy and safety of this treatment modality as the sole treatment modality or as part of the multimodality management of brain tumor patients. These publications ranged from the first multi-institutional phase III trial of radiosurgery for patients with brain metastases to numerous retrospective papers about treatment outcomes. Also, a number of these publications have explored the use of newer imaging modalities to improve treatment outcomes while others reported on the rare complication of radiation-associated second tumors.

SUMMARY

Recent publications of stereotactic radiosurgery have increased our understanding of the use of this technology. Future studies are needed to further improve outcomes, minimize toxicities and increase our understanding of this treatment modality.