Treatment Planning Optimization for Radiofrequency Ablation of Hepatic Tumors

Hernán Abeledo, Ph.D.Associate Professor

Engineering Management and Systems Engineering

School of Engineering and Applied Science

abeledo@gwu.edu

(202) 994-7521

Joint with: Enrique Campos-Nañez & Stella S. Munuo (GWU-SEAS)

Kevin Cleary & Filip Banovac (GUMC-ISIS)

Partially funded by the GW Institute for Biomedical Engineering

Radiofrequency Ablation of Liver Tumors

♦Minimally invasive cancer treatment modality (percutaneous,

laparoscopic)

♦Cells killed by heat generated by radiofrequency energy

♦Treatment alternative for 80% of un-resectable hepatic malignancies

♦Performed by Interventional Radiologists guided by Ultrasound, CT or MRI

♦Region treated by a single ablation is approximately a spherical ellipsoid

♦Probes come in several sizes (up to 5 cm diameter)

♦Large tumors may require multiple overlapping ablations

Figures from [Dodd, Soulen et al. 2000]

Towards Real-time RFA Planning

Goal: create a treatment planning tool that computes

optimized probe trajectories and ablation placements

Tumor Data Opti

mization

Module

OptimizedTreatment

Plan

No MDOK?

YesModifymodel

Tracking System relays probe location

MD

ablates

Updated Tumor & Ablation Data

Research Activities

♦Objectives and constraints of optimization module:

♦ Ensure entire tumor plus 1 cm margin are treated

♦ Avoid burns or punctures of other organs, bones, or major vessels

♦ Minimize number of required ablations

♦ Limit number of punctures to liver capsule (e.g., at most 3)

♦ Minimize number of needle insertions

♦ Allow reinsertion of probes through same puncture of liver capsule

♦ Minimize damage to healthy tissue (beyond 1 cm margin)

♦Develop mathematical models and optimization algorithms

as part of an image-guided treatment planning system

Optimization Methodology

♦Image data is discretized into a 3-D grid (~3mm resolution)

♦Grid points classified as tumor, margin, healthy, organ type, etc.

♦Integer programming methods used to model and solve problem

♦ Integer programming optimization techniques also used in

radiotherapy planning (brachytherapy, Gamma Knife)

♦RFA provides challenging problems for mathematical optimization