Implementing Radiation Dose-Volume Liver Response in Biomechanical Deformable Image Registration

Abstract

Purpose Understanding anatomical and functional changes in the liver resulting from radiotherapy is fundamental to the improvement of normal tissue complication models needed to advance personalized medicine. The ability to link pre-treatment and post-treatment imaging is often compromised by significant dose-dependent volumetric changes within the liver that are currently not accounted for in deformable image registration (DIR) techniques. This study investigates using delivered dose, in combination with other patient factors, to biomechanically model longitudinal changes in liver anatomy for follow-up care and retreatment planning. Methods Population models describing the relationship between dose and hepatic volume response were produced using retrospective data from 33 patients treated with focal radiation therapy. A DIR technique was improved by implementing additional boundary conditions associated with the dose-volume response in series with a previously developed biomechanical DIR algorithm. Evaluation of this DIR technique was performed on computed tomography imaging from seven patients by comparing the model-predicted volumetric change within the liver to the observed change, tracking vessel bifurcations within the liver through the deformation process, then determining target registration error (TRE) between the predicted and identified post-treatment bifurcation points. Results Evaluation of the proposed DIR technique showed that all lobes were volumetric deformed to within the respective contour variability of each lobe. The average TRE achieved was 7.3 mm (2.8 mm LR and AP, 5.1 mm SI), with the SI component within the average limiting slice thickness (6.0 mm). This represented a significant improvement (Wilcoxon, p < 0.01) over the application of the previously published biomechanical DIR algorithm (10.9 mm). Conclusion This study demonstrates the feasibility of implementing dose-driven volumetric response in deformable registration, enabling improved accuracy of modeling liver anatomy changes, which could allow for improved dose accumulation, particularly for patients who require additional liver radiotherapy.

Accuracy of deformable image registration techniques for alignment of longitudinal cholangiocarcinoma CT images

“…Three of the four TPSs (other than RayStation) have limited scope in altering registration parameters, but even different parameterizations of an algorithm (ANACONDA) failed to improve the performance significantly. While more recent state‐of‐the‐art DIR algorithms such as GIFTed Demons, and DIS‐CO, and advanced boundary conditions in biomechanical models may be able to provide some improvements, the full integration of new algorithms into existing TPSs is a lengthy process.…”

“…Simple rigid registration does not achieve a sufficient level of accuracy when volumetric changes and large patient motion occurs. 8 Studies have demonstrated the large volumetric response of the liver six weeks postradiation therapy, including hypertrophy and fibrosis. 9,10 One of the first studies to compare deformable image registration (DIR) techniques for pre-and post-RT liver cancer was conducted by Fukumitsu et al 11 The study compared commercially available DIR techniques in two treatment planning systems (TPS), MIM Maestro (MIM Software Inc., Cleveland, OH, USA) and Velocity (Velocity Medical Solutions, Atlanta, GA, USA).…”

“…Unfortunately, dose accumulation in a deformable organ such as the liver can be quite challenging. Simple rigid registration does not achieve a sufficient level of accuracy when volumetric changes and large patient motion occurs . Studies have demonstrated the large volumetric response of the liver six weeks postradiation therapy, including hypertrophy and fibrosis …”

Deformable image registration for radiation therapy: principle, methods, applications and evaluation

“…For this purpose, specific tools, developed in academic institutions, are imported to commercial RT TPS [12,139,141]. Therefore, DIR algorithms require further development to better meet clinical needs, such as accounting for the different imaging modalities between planning and treatment delivery [133,142], near-real-time algorithms with graphic processing unit-based frameworks [139,[143][144][145], and anatomical properties simulated by finite element models [146][147][148][149][150].…”

Vasculature-Driven Biomechanical Deformable Image Registration of Longitudinal Liver Cholangiocarcinoma Computed Tomographic Scans

“…Recently, an expansion of Morfeus to model the volumetric response to the dose of the liver tissues was proposed. 9 The accuracy of the method to register CT scans pre-and post-RT of liver cancer was quantified for 7 patients by measuring the TRE of vessel bifurcation points. Modeling the dose response by adding dose boundary conditions in the biomechanic model allowed to significantly improve the DIR accuracy in comparison to using the standard model based on boundary conditions only on the liver surface.…”