Quantitative Relationship of CT Hounsfield Units to Iodine Concentration for Radioactive Iodine Treatment
X Kong1*, M Georgiou2, S Gulec3, A Mcgoron3, X Wu1, S Shukla4, (1) JFK Medical Center, Miami, FL, (2) University of Miami School of Medicine, Miami, FL, (3) Florida International University, Miami, FL.
Presentations
PO-GePV-T-16 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: To establish a quantitative relationship between CT Hounsfield Units(HU) and Iodine concentration for I-131 radioactive iodine ablation.
Methods: Both experimental methods and Monte Carlo simulation have been performed in our study. Sodium Iodide(NaI) solutions with different concentrations (Iodine content ranges from 500mg/cc to 0.49mg/cc) were prepared in lab with high purity NaI powder (99.9+%). The solution was then filled into water chamber insert of Gammex CT Electron Density Phantom. GE Discovery IQ PET/CT scanner was utilized for scanning. 120kVp and 5mm slice thickness scanning protocol was adapted. Fluka Code was used for Monte Carlo simulation. 80cm air bore was modeled, 1 cm^3 of NaI solution was created inside of the 33cm diameter solid water phantom. A regional dose detector was positioned on the opposite side of the air bore. 3-4millons particles were simulated to keep the standard deviation less than 2%. Linear attenuation coefficient and corresponding HU were calculated for water and different Iodine concentrations. 120kV and 58.1kV mono-energetic photon beams were simulated.
Results: Extended HU option was not enabled for CT reconstruction. The HU saturated at 3070 for any iodine content greater than 250mg/cc. A bilinear relationship exists between HU and iodine content. Since low iodine concentrations are of interest to our research, a linear regression model was fitted with R^2 = 0.9989.For Monte Carlo simulation, the photons have a single nominal energy verse continuous energy spectrum from CT. The HU depends on the photon energy and is different as HU from our CT study, but still a linear relationship can be quantified.
Conclusion: I-131 is utilized as a theranostics agent for thyroid cancer, it is very possible to predict the iodine concentration based on the HU from CT. Based on our CT study, the iodine concentration can be predicted from equation iodine(mg/cc) = 0.0575*HU - 0.6349.
Keywords
Not Applicable / None Entered.
Taxonomy
IM/TH- Radiopharmaceutical Therapy: General (most aspects)
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