Optimal (57)Co flood source activity and acquisition time for lymphoscintigraphy localization images

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Radiopharmacy

Background:

• Breast lymphoscintigraphy is crucial for detecting lymphatic nodes in breast cancer staging.
• Optimal localization imaging is needed to accurately identify node locations and patient anatomy.
• Minimizing radiation exposure during diagnostic procedures is a primary patient safety concern.

Purpose of the Study:

• To determine the optimal Cobalt-57 ((57)Co) flood source activity and acquisition time for breast lymphoscintigraphy localization images.
• To achieve adequate body outline and lymph node visualization while minimizing radiation dose.
• To evaluate the impact of different (57)Co source activities on image quality and radiation exposure.

Main Methods:

• Utilized an anthropomorphic thorax breast phantom to simulate lymphoscintigraphy.
• Acquired 3-minute localization images using five different (57)Co flood sources (37-269 MBq).
• Assessed image quality, contrast-to-noise ratio, and measured total radiation exposure.

Main Results:

• All tested (57)Co sources enabled lymph node visualization within a 3-minute acquisition.
• A 126-MBq (3.41-mCi) (57)Co source provided the best balance of body outline and node detection.
• Lower activity sources (e.g., 37 MBq) yielded insufficient body definition, while higher activities reduced node contrast and increased radiation dose.

Conclusions:

• A 3-minute localization scan with a 126-MBq (3.41-mCi) (57)Co source is recommended for optimal breast lymphoscintigraphy.
• This protocol ensures clear anatomical depiction and accurate node visualization with minimal patient radiation exposure (estimated 8.7-13.1 microSv).
• Higher (57)Co activities can decrease node detectability, particularly in thinner patients.