EXPERT ROUNDTABLE

Exploring the Benefits of Advanced Dosimetric Methods

Join an energizing discussion about the definition of personalized dosimetry and its impact, led by three well-known RPT pioneers and two Voximetry innovators who are committed to making personalized dosimetry the standard of care.

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Join us online Feb. 23rd at 4 p.m. EST to unlock the future of RPT.
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Roundtable Participants

Richard L Wahl, MD

Elizabeth E. Mallinckrodt Professor and Chair, Department of Radiology
Professor of Radiation Oncology
Director, Mallinckrodt Institute of Radiology

Homer A. Macapinlac, MD

James E. Anderson Distinguished Professor of Nuclear Medicine
Chair, Department of Nuclear Medicine
The University of Texas MD Anderson Cancer Center

Stephen A. Graves, PhD, DABR

Assistant Professor of Radiology
University of Iowa

Joe Grudzinski, PhD

Chief Innovation Officer & Co-Founder
Voximetry

Sue Wallace, PhD

Chief Executive Officer
Voximetry

You Deserve an Easy Solution for Personalization,
Because RPT Patients Deserve Personalized Treatment.

Physicists at Voximetry have combined the power of personalized pharmacokinetics with unmatched radiation transport calculation accuracy to provide the tools RPT has needed to manage wide-ranging patient-drug variability. Torch™* Plan Assessment and Treatment Planning software combines automated patient-specific pharmacokinetic (PK) modeling and GPU-accelerated dose computation to help manage tumor toxicity and estimate risk to critical structures in just a few minutes.

As a result of RPT dosimetry evolution, several unique approaches co-exist in research labs and clinics today:

THE ESTABLISHED: Homogenous Whole Organ Population Averaging

Since 2004, OLINDA EXM has been the most utilized dosimetry solution for RPT. This approach assumes uniform distributions of activity and average absorbed doses within whole organs of a “standard” phantom – disregarding nonuniform distributions or dose gradients near tissue interfaces. Additionally, OLINDA EXM approximates tumors as isolated spheres which diminishes the accuracy of tumor dosimetry. Lastly, OLINDA reports dosimetry as a single number which is most useful for population analysis and not personalized dosimetry.

THE PROGRESSIVES: Semi-Heterogenous Truncated Kernels

Early attempts at voxel-level dosimetry use kernel-based methods to improve visualization of heterogenous dose distribution. However, these methods can be inaccurate because they often arbitrarily truncate and disregard tissue density heterogeneity. Truncation has significant implications for radionuclides like I-131 with large gamma contributions. Disregarding differences in tissue density can result in inaccurate radiation transport that is particularly important for lung and bone tumor dosimetry.

THE VOXERS: Personal PK Models With Heterogenous Monte Carlo Dose Distributions

The challenges of OLINDA and kernel-based methods have been overcome by coupling patient-specific geometry (e.g., anatomy with tissue density) and kinetic modeling (e.g., RPT concentration over time) with accelerated advanced radiation transport on the voxel-level. The powerful combination of personalized pharmacokinetics (PK) with unmatched radiation transport calculation accuracy provides the tools that RPT has needed to manage wide-ranging patient-drug variability in the clinic.

VOXERS CHOICE

Torch Plan Assessment and Treatment Planning are designed to provide a best-fit PK curve for each Region of Interest (ROI), absorbed radiation dose estimates at the voxel level displayed as a dose map and multi-region DVH curves. To provide this information, Torch capabilities include deformable image registration followed by automatic ROI propagation over multiple timepoints, kinetic modeling, time activity integration and accelerated Monte Carlo dose calculations in minutes. Accelerated-GPU calculation speed is key to assuring Torch can easily integrate into busy lab or clinic demands without compromising confidence in the results.

Why Pharmacokinetics for RPT?

The role of pharmacokinetics (PK) in dosimetry is to support the optimization of the administered activity based upon patient-specific absorption, distribution, metabolism and excretion (ADME). Recent RPT studies report the biological distribution of a specific drug can vary 3- to 5-fold between patients. [1,2] Quantifying this process for each patient is crucial to accurately estimate absorbed dose per voxel, Region of Interest (ROI) or whole organ. Torch’s automatic PK fitting takes the guesswork out of modeling the RPT uptake and clearance from the body.”

Torch Time-Activity Curve Fitting

Torch automatically selects the optimal curve type to describe the observed drug activity and identifies best-fit parameters for that curve to match the PK timepoint data. Not satisfied? With Torch you can always tweak parameters until you’re satisfied or choose an entirely different curve type.


Personalized dosimetry systems should include deformable image registration followed by automatic Region of Interest (ROI) propagation over multiple timepoints, kinetic modeling, time activity integration and accelerated Monte Carlo dose calculations in a few minutes. The calculation speed is key to assuring personalized dosimetry fits easily into busy clinic demands without compromising confidence in the results.