A New Technique Using 4DCT Scans to Create Custom Cardiac Blocks for Left-Sided Breast Cancer Treatments

Area of Science:

• Radiation Oncology
• Medical Imaging
• Cardiovascular Health

Background:

• Cardiac toxicity is a significant concern in left breast cancer radiation therapy, directly correlated with radiation dose to the heart.
• Minimizing heart dose is crucial for improving treatment outcomes and reducing long-term side effects in breast cancer patients.
• Current methods for cardiac dose reduction may not fully account for respiratory and cardiac motion during treatment.

Purpose of the Study:

• To develop and evaluate a novel method using 4-dimensional computed tomography (4DCT) to create improved custom cardiac blocks.
• The primary goal is to minimize radiation dose delivered to the heart during left breast cancer treatment.
• To compare the effectiveness of 4DCT-based heart blocks against standard free-breathing (FB) CT-based blocks.

Main Methods:

• Acquired 4DCT scans for 20 patients undergoing left breast cancer treatment.
• Created a maximum intensity projection (MIP) heart contour from the 4DCT data.
• Designed custom heart blocks to encompass the MIP heart volume and compared them to blocks created using standard FB CT images.

Main Results:

• 4DCT-based heart blocks were consistently larger than FB blocks, with a mean increase in area of 2.58 cm².
• The mean increase in multileaf collimator coverage was 3.9 mm, indicating improved heart coverage by the blocks.
• Analysis showed a significant reduction in radiation dose to the heart when using the 4DCT-based blocks compared to FB blocks.

Conclusions:

• 4DCT-based heart blocks effectively account for respiratory and cardiac motion, leading to larger and more protective block volumes.
• This improved blocking strategy significantly reduces radiation dose to the heart in left breast cancer patients.
• The technique is readily implementable using currently available 4DCT technology in clinical settings.