Current Research

My lab uses quantitative 90Y bremsstrahlung SPECT/CT and 90Y PET/CT imaging techniques to perform advanced patient-specific dosimetry to compute voxel-level absorbed dose estimates to tumors and normal liver [Fig. 1]. We have characterized the tumor dose-response curves for primary and metastatic liver tumors following 90Y-microsphere therapy [Fig. 2]. We have several funded research grants in this area. 

The long-term goal of the group is to improve the clinical outcomes  and response rates for patients by using advanced dosimetry calculations and developing patient-specific treatment planning for 90Y-microsphere therapy.  

We have a funded prospective Phase II clinical trial RAPY90D: Radioembolization for HCC Patients with Personalized Yttrium-90 Dosimetry for Curative Intent (NCT03896646, PIs: AM and SCK).  We are also participating in additional clinical trials NCT03295006 and NCT03028311.  We work as part of a multi-disciplinary team that includes Interventional Radiologists (AM), Medical Oncologists (AK), and Nuclear Medicine Physicians (ML and AB). 

Key Collaborators: Armeen Mahvash, M.D.; Ahmed Kaseb, M.D.; Marnix Lam, M.D., Ph.D.; Arthur Braat M.D., Ph.D.

Select References:

1. Siman et al. Systematic and random errors of PET-based 90Y 3D dose quantification.  Med Phys 2020. https://doi.org/10.1002/mp.14117

2. Salem et al. Clinical and dosimetric considerations for Y90: recommendations from an international multidisciplinary working group.  Eur J Nucl Med Mol Imaging 2019. https://doi.org/10.1007/s00259-019-04340-5

3. Kappadath et al. Hepatocellular carcinoma tumor dose response following 90Y-radioembolization with glass microspheres using 90Y-SPECT/CT based voxel dosimetry. Int J Radiation Oncol Biol Phys 2018.  https://doi.org/10.1016/j.ijrobp.2018.05.062

4. Bastiaannet et al. The physics of radioembolization.
EJNMMI Phys 2018. https://doi.org/10.1186/s40658-018-0221-z

5. Balagopal and Kappadath. Characterization of 90Y-SPECT/CT self-calibration approaches on the quantification of voxel-level absorbed doses following 90Y-microsphere selective internal radiation therapy.
Med Phys 2018. https://doi.org/10.1002/mp.12695

6. Siman et al. Practical reconstruction protocol for quantitative 90Y bremsstrahlung SPECT/CT. Med Phys 2016.
https://pubmed.ncbi.nlm.nih.gov/27587040  

We are evaluating deterministic (Grid-Based Boltzmann Solver) methods of radiation transport for fast and accurate patient-specific dosimetry calculations in targeted radionuclide therapies for nuclear medicine.  We have performed the fundamental work of implementing and validating GBBS for photons and beta emission used in nuclear medicine. We are currently adapting this approach for patient-specific imaging and dosimetry.

We have also investigated various voxel-dosimetry calculation techniques (Monte Carlo DOSXYZnrc, kernel-based, local deposition, etc.). We are investigating their dosimetric implications in 90Y microsphere therapy in the liver, lung, and in the liver/lung interface.

Collaborators: Firas Mourtada, Ph.D. (Christiana Care, Newark, DE), Todd Wareing Ph.D. (Varian, Seattle, WA)

Molecular Breast Imaging (MBI) is a new emerging breast-specific nuclear medicine imaging technique that uses a small field-of-view dual-headed semiconductor-based gamma camera in a mammographic configuration specifically designed to obtain high resolution images of 99mTc-sestamibi uptake in the breast.

We are developing novel image acquisition and post-acquisition data processing techniques on GE Discovery NM750b to generate quantitative 99mTc-sestamibi MBI images. We are also assessing the clinical role of MBI images as an early predictor of response for patients with breast cancer undergoing neoadjuvant chemotherapy.

Collaborators: Maia Rauch, M.D.; Aaron Jessop, M.D.

We have performed a comprehensive evaluation of material decomposition with rapid kVp-switching dual-energy CT scanners and investigated its use for assessing bone mineral density.

Both PET and SPECT Emission imaging suffer (relative to CT) from poor spatial resolution which impacts the quantitative accuracy of the image. We have developed novel image processing algorithms to establish voxel-based bounds on activity concentration – this new information will benefit clinical interpretation of PET/CT and SPECT/CT.

We are studying the effects of finite spatial resolution and system calibration on the quantitative accuracy of PET/CT and SPECT/CT using GATE Monte Carlo simulation.

We are investigating the effects of respiratory motion during clinical PET/CT and SPECT/CT data acquisition on the accuracy of patient-specific dosimetry calculations.