Author: Hannah Grover, Andrew J. Sampson 👨🔬
Affiliation: Oregon Health & Science University, UT Health San Antonio 🌍
Purpose: The goal of this work was to quantify the dosimetric impact of iodinated contrast on fibroglandular breast tissue to better inform clinical risk and benefit assessments when determining the most appropriate mammography exam for patients, including in a screening capacity.
Methods: The Virtual Imaging Clinical Trial for Regulatory Evaluation (VICTRE) toolkit was chosen to generate a fully digital representative breast phantom for each of the four BI-RADS® tissue density categories. Time-enhancement curves (TECs) were calculated to estimate the concentration of iodine at clinically relevant time points in five tissues: artery, vein, fibroglandular, malignant tumor, and benign tumor. An in-house-developed Monte Carlo radiation transport code, PHENX, was used to simulate the low- and high-energy (LE and HE) exposures typical of contrast-enhanced digital mammography (CEDM) exams. The output from each simulation provided an estimate of the total radiation dose absorbed in every voxel. Fibroglandular voxels were processed to calculate the average glandular dose (AGD), a common dose comparison metric.
Results: The time-dependent iodine concentration mask combined with the detailed breast phantoms resulted in a 4D perfusion model, with methodology for adaptation to specific research needs. For the total CEDM exam simulations (LE and HE exposure combined), the incorporation of iodine resulted in an increase in estimated AGD of 2.67% and 9.87% for heterogeneously and extremely dense breast phantoms, respectively. Conversely, it decreased the AGD estimate for scattered fibroglandular and almost entirely fatty phantoms by -1.79% and -2.68%, respectively. The presence of iodine directly altered the dose distribution within the tissue voxels, resulting in increased absorbed dose in the superior breast and decreased absorbed dose in the inferior breast.
Conclusion: This investigation supports the inclusion of iodinated contrast in breast phantom models because it demonstrated that iodine presence directly impacts the estimated absorbed dose values, as well as the overall dose distribution.