Table 1. Summary of advantages and disadvantages of imaging modalities.

Imaging Modality	Advantages	Disadvantages
Intra-operative magnetic resonance imaging (iMRI) [19-24]	Significantly enhances the extent of tumor resection. Provide real-time visualization of dynamic changes that occur during surgery. Provides high accuracy in low-grade gliomas. Helps in performing awake craniotomy with language mapping. Can predict the presence and absence of tumor residual with high sensitivity.	Chances of false negative or false positive findings. Requires expertise and skilled trainers. Low diagnostic accuracy in meningioma and metastases. Requires more time in awake craniotomy which leads to pulmonary embolism, and venous thrombosis. Rate of complete resection of tumors is lower with iMRI alone.
Intraoperative Fluoroscopy [81-86]	Facilitates tumor delineation. Maximizes the extent of high-grade glioma resection. Causes the brain tumor to lighten, and increasing accuracy. Safe, useful and universally available. Enhances blood-brain barrier rupture.	Subjective colour discrimination may cause problems. Specificity is low. Under dark field conditions, visualization of anatomical landmarks is compromised. Some of the brain-harboring glioma may not give fluorescence. Bleeding cannot be addressed in dark field conditions.
Intra-operative computed tomography (iCT) [25-28]	Provides better bony resolution. Decrease radiation exposure. Helps in detecting brain shift with high accuracy. Helpful in biopsy of small target volume tumors.	High risk due to radiation. The modality is expensive. Movement of large machine in and out causes high risk of infections. Improper positioning of the patient may cause alteration of image quality.
Functional magnetic resonance imaging (fMRI) [50-61]	Critical for pre-surgical planning, mapping brain functions. Task-based fMRI aids in detecting motor and language areas. Resting-state fMRI allows multiple brain function assessment without patient cooperation.	Task-based fMRI requires patient cooperation, challenging for certain patients. Lower specificity in high-grade gliomas. Limitations in data processing for resting state-fMRI.
Positron emission tomography (PET) [62-70]	High sensitivity in tumor detection, especially with amino acid-based tracers. Differentiates scar tissue from active tumors. Effective in detecting gliomas and meningiomas. Useful in assessing treatment responses and tumor metabolism.	Poor image resolution. Exposure to high levels of radiation. Interference from normal brain activity in fluorodeoxyglucose (FDG) PET. High costs and limited availability.
Magnetic resonance spectroscopy (MRS) [72-80]	Non-invasive, provides insight into tumor metabolism. Effective in distinguishing tumor grades and types. Useful for assessing residual tumors intraoperatively. Enhances accuracy when combined with other modalities like diffusion-weighted imaging.	Lower sensitivity and specificity compared to some PET modalities. Limited clinical adoption of ultra-high field 7T MRS. Can be less reliable without a combination with other imaging modalities.
Endoscopy [93-100]	Minimally invasive nature. Visualization is enhanced. Reduced surgical morbidity. Shorter hospital stays. Improved patient recovery.	Difficult learning curve for operators and surgeons. Specialized equipment needed. Limited range of motion. 3-Dimensional visualization is not available. Challenging ergonomics and fatigue. Careful patient selection.
Intra-operative ultrasound (IOUS) [30-49]	Less expensive than other modalities. Does not prolong surgery time. Low-grade gliomas are better defined with IOUS than CT/MRI. Shows significant definition of brain tumors in comparison with intra-operative CT/MRI. Better diagnostic precision in diagnosing residual tumor than iMRI.	Challenging interpretation than intra-operative MRI/CT. IOUS is prone to artifacts. Steep learning curve of IOUS. Does not provide synoptic view of the brain, and the image quality is highly variable and operator-dependent. Restricted to the craniotomy, providing a limited field of view.
Single photon emission computed tomography (SPECT) [87-92]	It is less expensive than CT/MRI. SPECT is widely available. Detects early changes in metabolism that lead to early tumor detection. Helps in detecting tumor progression. It is a non-invasive modality.	Lower special resolution than PET and MRI. Longer scanning time from PET and MRI. Causes exposure to radiation. Artifact-prone. Less sensitive than MRI. Less anatomical detail as compared to CT/MRI.