2.1 Patients
According to pre-operative MRI scans, a total of 8 suspected glioma patients (five male patients and three female patients aged from 21 to 58), who are scheduled for tumor resection and provide their informed consent, were recruited from December 2019 to June 2020. The glioma tissues in our study included four low-grade gliomas (WHO Grade II) and four high-grade gliomas (WHO Grade IV). The patients’ characteristics are shown in Table 1.
Table 1
The Characteristics of the Patients
Patient
|
Gender
|
Age of diagnosis (y)
|
Lesion location a
|
Tumor type
|
Grade
|
1
|
Male
|
29
|
F-T
|
Glioma
|
High
|
2
|
Female
|
24
|
F
|
Glioma
|
Low
|
3
|
Male
|
58
|
T
|
Glioma
|
Low
|
4
|
Female
|
26
|
P
|
Glioma
|
Low
|
5
|
Female
|
18
|
F-P
|
Glioma
|
High
|
6
|
Female
|
54
|
P
|
Glioma
|
Low
|
7
|
Female
|
63
|
F
|
Glioma
|
High
|
8
|
Female
|
34
|
F-P
|
Glioma
|
High
|
a Note: F, frontal; T, temporal; P, parietal; O, occipital
All patients underwent pre-radiotherapy Functional MRI as well as DTI and conventional MRI. Functional structures and white-matter pathways were placed in the natural regions without any overlap with the target volume of the lesions. All patients were able to perform the specific tasks to generate functional maps of brain activation. The Varian linear accelerator with a Millennium dynamic multileaf collimator (DMLC) system delivered external radiation therapy.
2.2 Patient preparation and MRI test considerations
The MR scanning sequence was begun by screening the patient for any clothing, jewelry, or devices such as pacemakers that may degrade the MR images and MRI safety and patient's condition evaluation. The technologist explained the scanning procedure and answered questions. Patients were advised not to move at all during the examination. Also, those heads were kept in a fixed position with special pads as much as possible. To order the paradigms, we tried to prioritize the difficulty and simplicity of implementation. Achieving the desired outcomes requires focusing on a paradigm needing more patient's attention at first, then simpler paradigms such as finger movement implementation.
2.3 Data acquisition
Three imaging studies were performed on the patients using a Siemens MAGNETOM Avanto 1.5 T scanner with an eight-channel head coil.
2.3.1 Anatomical and Functional MRI characteristics
T1-weighted structural brain MR Images were initially obtained using the MP-RAGE sequence. BOLD fMRI data were acquired to provide brain activation maps, using single-shot gradient echo-planar imaging (EPI), which is more sensitive to T2* changes. The structural and functional MRIs were performed using the parameters summarized in Table 2.
Table 2.
The characteristics of the structural images and functional MRI
Sequence
|
TR (ms)
|
TE (ms)
|
TI (ms)
|
Slice Thickness(mm)
|
Number of Slices
|
FA
|
Matrix
|
MP-RAGE
|
1820
|
3.49
|
1100
|
1
|
176
|
7°
|
256*256
|
GRE-EPI
|
3000
|
30
|
-
|
3
|
176
|
90o
|
65*64
|
2.3.2.Diffusion Tensor Imaging (DTI)
DTI images acquired with the spin echo-echo planar imaging (SE-EPI) sequence (TR = 9500 ms, TE = 90 ms, acquisition matrix = 128 × 128 pixels; FOV = 256 mm × 256 mm2; slice thickness = 2.0 mm; b value of 1,000 s/mm2 along 12 non-collinear directions).
2.3.3Experimental Paradigms
This study simulated the primary motor cortex, Broca's area, and Wernicke's area. The motor cortex, located in the precentral gyrus, is mainly responsible for the actual performance of movements (20). Broca's area, which is placed in the frontal lobe (often left), produces speech. In contrast, Wernicke's area in the temporal lobe (usually the left side) is related to language comprehension and speech planning (21).
The hand, foot, lip, and tongue motor paradigms activated the primary motor cortex. The measurement sequence of these paradigms consisted of a 24-second activation period (8 scans) followed by a 24-second rest period (8 scans), with eight times of repeat. All the measurements started with an initial rest period.
The reverse word reading (RWR) paradigm was used to stimulate Broca's area. The stimuli of the RWR task in each activation block consisted of 10-word trials in 24 seconds, followed by a 24-seconds rest period. The subject is presented with a five-letter Persian word in each activation period while the letters were displayed in reverse order. They were then asked to read each word silently once. The measurements always began with an initial rest period (22). The story paradigm was used to stimulate Wernicke's area. Like other designs, this paradigm started with a rest period. In the story paradigm, a short and manageable story was first considered, which was broadcast through the device's audio system during a 33 second activation period (11 scans) followed by a 33 second rest period (11 scans), and these periods were repeated five times. The story was chosen so that the story would end with the end of the paradigm.
2.4 Data Analysis
2.4.1 fMRI Data Analysis
After imaging, data were transferred to the MATLAB workstation for analysis using SPM12 software (Statistical Parametrical Mapping, Wellcome Department of Cognitive Neurology, London, England). Data series were motion-corrected and smoothed with a 6 mm FWHM (full width at half maximum) Gaussian kernel. The model function was applied to each voxel in the brain (general linear model), and finally, a statistical map was estimated. Significantly activated voxels were identified using an initial p-value threshold of 0.001. fMRI scan data (mean image) was combined with the T1 structural MRI image obtained at the same scanning position, allowing the functional MR activation color map visibility on the patient’s brain anatomy. The merged image sets (JPEG format) were then converted into DICOM format using MATLAB software. In this conversion, the color images were replaced with the grayscale images using the intensity of the green color as the grayscale intensity. fMRI DICOM series were also sent to the planning system.
2.4.2 DTI Analysis
Data pre-processing consists of raw data conversion, skull-stripping, and motion/eddy correction was performed using DSI studio software (developed by Fang-Cheng Yeh from the Advanced Biomedical MRI Lab, National Taiwan University Hospital, Taiwan, Supported by Fiber Tractography Lab, University of Pittsburgh, and made available at http://dsistudio. labsolver.org/Download/). After data pre-processing, we used a reconstruction model base (DTI) to process the diffusion images. Average DTI values were extracted from voxels within the ROIs and tracts. The tractography process used a deterministic fiber tracking algorithm. Desired neural pathways were extracted in two directions in two hemispheres of the brain. Finally, by using 3D Slicer software, the location of fiber tracts saved as the region of interest (ROI) was determined on the T1 structural images.
2.5. Image Fusion
As shown in figure 1. each patient's axial CT images were registered with the corresponding anatomical MRI images, using the automatic registration algorithm of the TPS to precisely describe the targets and standard organs at risk (OARs). The anatomical MRI volumes were fused with the corresponding white matter tracts and fMRI activation maps and then imported into the Isogray treatment planning system (TPS) software version 3.1 as separate grayscale DICOM images.
2.6. Treatment Planning
The prescribed dose was 54 Gy to 60 Gy. Anatomical OARs including the brainstem, spinal cord, eyes, bilateral lens, bilateral retina, lacrimal glands, bilateral cochlea, bilateral optic nerves, and the optic chiasm were delineated. The fiber tracts and the functional structures nearby the targets were also contoured as extra OARs using the fused fMRI and DTI images. Two three-dimensional conformal radiotherapy (3DCRT) treatment plans were developed for each patient. In the first plan, only the PTV and anatomical OARs were considered. On the other plan, the physicist took the functional structures and fiber tracts situated near the target as Neurocognitive functions OARs. The second plan was generated to reduce the dose of the functional structures and fiber tracts while keeping prescription dose coverage for the planning target volume (PTV) and similar OAR dose-volume levels as the standard care treatment plan.
Dose-volume histograms (DVH) data were extracted from TPS. The mean (Dmean) and maximum doses (Dmax) of radiation to the functional regions and fiber tracts were determined for both RT plans. Anatomical OARs and Neurocognitive functions OARs were compared based on the values of Dmax and Dmean.
2.7.Statistical analyses
Wilcoxon's test was used to compare two plans parameters. The differences were considered statistically significant at p < 0.05. Statistical analyses were performed using SPSS software ver. 25.0.