Reliability of the Size Evaluation Method for Meningiomas: Maximum Diameter, ABC/2 Formula, and Planimetry Method

Area of Science:

• Neurosurgery
• Radiology
• Oncology

Background:

• Accurate tumor volume measurement is crucial for meningioma management.
• Assessing tumor size using maximum diameter, ABC/2 formula, and planimetry with MRI has limitations.

Purpose of the Study:

• To evaluate the accuracy of tumor size measurements using maximum diameter, ABC/2 formula, and planimetry with thick-slice and thin-slice MRI.
• To compare these methods in various meningioma locations and assess the impact of tumor irregularity.

Main Methods:

• Eighty-three meningiomas were analyzed using maximum diameter, ABC/2 formula (V1), and planimetry with thick-slice (V2) and thin-slice (V3) MRI.
• Form factor (FF) assessed tumor irregularity. V3 was considered the true volume.
• Accuracy of V1 and V2 was compared to V3 across different tumor locations.

Main Results:

• Maximum diameter showed significant correlation with V3 (r=0.91) but had higher errors for larger tumors.
• ABC/2 formula (V1) strongly correlated with V3 (r=0.97) but overestimated volume in middle skull base meningiomas or those with low FF.
• Planimetry with thick-slice MRI (V2) was generally accurate, except for small meningiomas or when tumors were poorly fractionated on MRI.

Conclusions:

• The ABC/2 formula may overestimate meningioma volume, particularly for middle skull base tumors or those with low form factor.
• Thick-slice MRI planimetry provides relatively accurate meningioma volumes when tumors are adequately fractionated (>4 slices).