A Method for Calculating Small Sizes of Volumes in Postsurgical Thyroid SPECT/CT Imaging.

Area of Science:

• Nuclear Medicine
• Radiology
• Oncology

Background:

• Differentiated thyroid cancer treatment involves surgery and often radioiodine therapy.
• Accurate assessment of disease status and treatment response is crucial for patient management.
• SPECT/CT imaging is valuable for detecting small metastatic lesions and assessing their characteristics.

Purpose of the Study:

• To develop and validate a method for accurately calculating small volumes in SPECT/CT imaging.
• To assess the method's performance using Iodine-131 (I-131) and Iodine-123 (I-123) SPECT/CT images from a phantom.
• To evaluate the method's ability to handle radiation spillover and its accuracy for small volumes.

Main Methods:

• A novel volume calculation method was developed using the gray-level histogram technique applied to SPECT and CT 3D matrices.
• SPECT matrices were resized and aligned to corresponding CT matrices prior to volume calculation.
• The method was validated using a neck-thyroid phantom with varying volume sizes (0.5-10 mL) and I-123/I-131 SPECT/CT imaging.

Main Results:

• The developed method accurately calculated lesion volumes, with minimal differences between actual and calculated volumes (e.g., 1.2% for 10 mL, 15.2% for 0.5 mL).
• The method was robust against radiation spillover from high-uptake voxels, a common issue in SPECT imaging.
• Accuracy was maintained even with higher administered activities and for smaller volumes, demonstrating its clinical utility.

Conclusions:

• The validated method enables accurate calculation of small volumes in SPECT/CT imaging for differentiated thyroid cancer.
• This technique can be effectively used with postsurgical I-123 and I-131 SPECT/CT images without additional imaging modalities.
• The findings support the use of this method for improved disease staging, treatment monitoring, and dosimetry in thyroid cancer management.