Each year, approximately 4,500 patients receive radiation treatment at the University of Kansas Cancer Center, one of 56 National Cancer Institute-designated comprehensive cancer centers in the United States. In June 2023, the center became one of the first radiation therapy providers to clinically utilize the Eclipse v18.0 treatment planning system across its fleet of ten Varian treatment delivery systems. Calling the upgrade from Eclipse v15.6 to v18.0 “seamless,” Director of Treatment Planning Dr. Kenny Guida, DMP, DABR, shares his perspective and enthusiasm for the improved efficiency and accuracy that v18.0 brings to the center’s busy, high-volume environment.
What feature or improvement in Eclipse v18.0 has had the biggest positive impact on your practice?
As a physicist with a passion for treatment planning, I would say that the improvements to the Photon Optimizer (PO) have been groundbreaking. The advancement in Fourier Transform Dose Calculation (FTDC) is one of the best things that has ever happened in terms of efficiency and accuracy in the optimization process. It was amazing to see how much closer FTDC is to Monte Carlo and Acuros XB than MRDC (Multi-Resolution Dose Calculation) ever was. Additionally, the GPU improvements dramatically speed up optimization. PO in v18.0 also provides the ability to use SBRT NTO (Normal Tissue Objective) for the first time, which is another tool that our team has come to utilize in many stereotactic cases.
What impacts has Enhanced Leaf Modeling (ELM) had on your practice and what might it mean for other practices?
The ELM is a breakthrough in more accurate modeling of the MLC leaf tip and beam divergence. We are seeing closer agreement between predicted and measured dose distributions, presumably due to improved MLC modeling. Before we began using Eclipse v18.0 clinically, our physics team performed ELM measurements for our 10 linear accelerators using DICOM files and guidance provided by the Varian team. [Note: Sites can upgrade to Eclipse v18.0 and use their previous DLG measurements to configure the ELM, or continue with previous beam models until they are ready to use the ELM.] We recreated many of the tests reported in the research paper by Ann Van Esch et al. Our tests demonstrated, among other positive observations, how the ELM improved in modeling the leaf tip and off-axis dose distributions, which are critical in radiotherapy today with the increased use of small fields in SRS and SBRT. We recently commissioned a Varian Edge system equipped with HyperArc, so understanding the impact of ELM on single-isocenter, multi-target treatments was important to our physics team. Recent measurements using EBT4 indicated a difference of up to 2% between measured and v18.0 dose predictions for Zebra fields, even at a 12cm off-axis position. When applied to HyperArc plans, which involve delivering precise high-dose beams across the entire field, these measurements align much more closely with the predictions in Eclipse, and thus should have a significant impact on the accuracy of patient treatments.
What has been your experience with the GPU improvements on KU?
Our dosimetrists tell us that the GPU is their favorite feature of Eclipse v18.0. With the demand for high-quality plans in a high-volume environment, GPU assistance in VMAT planning has been a vital asset to our dosimetry team. VMAT. We reanalyzed 40 VMAT patients, including a variety of disease sites as well as HyperArc, with PO versions v15.6 and v18.0. Using PO v18.0 with FTDC without a GPU, we saved an average of 2.5 minutes (30%) compared to PO v15.6. Enabling the GPU saved an average of six minutes, a 75% reduction in plan optimization time. Using the GPU in PO v18.0, we saved over 60% in plan optimization time compared to PO v18.0 without a GPU. SBRT. In a similar study, I ran 50 lung SBRT cases with PO v15.6 and PO v18.0, with and without GPU. With convergence mode enabled, PO v18.0 with GPU takes an average of four minutes to optimize a plan from MR level 1 to 4. Without GPU, the average optimization time is ten minutes. In contrast, with PO v15.6, these same optimizations took an average of 16 minutes.
How was your experience with the new MCO isodose line drag function?
With MCO’s isodose line dragging, planners can interactively see in real time the effect of offsets on a plan. For example, if one of our physicians doesn’t want to see 54 Gy in the brainstem, the planner can show the physician possible alternatives by dragging the 54 Gy isodose line away from the brainstem with a simple tap on the screen. Isodose line dragging gives us another tool to tailor each patient’s plan specifically to the physician’s intent.
Has SBRT NTO been a useful tool for minimizing manual work such as creating optimization rings in your plans?
SBRT NTO has reduced my reliance on rings for SBRT planning. I was accustomed to using 2-3 rings, depending on the plan, to contain high and intermediate doses and improve compliance. Now, I turn on my SBRT NTO and increase the priority to match my target structures, and I see improved compliance. SBRT NTO has a place in the clinic for many body sites, especially as clinics treat more oligometastatic disease. For cases where a planner is treating multiple targets in the lungs or liver, SBRT NTO aims to improve compliance and reduce binding dose without the need to add additional avoidance structures.
What was your overall experience with the upgrade process to v18.0?
While any upgrade can be stressful, we had the full support of our team at the University of Kansas Cancer Center, including our Department Chair, Dr. Ronald Chen, and the Head of Physics, Dr. Harold Li. We jumped from v15.6 to v18.0, so we were provided with new tools and improvements from v16.1, such as clinical targets, along with the new features in v18.0. Participating in the release program gave us time to explore the new features—MCO isodose line drag, FTDC, and especially Enhanced Leaf Modeling—so we were ready to implement these updates shortly after the upgrade. There was no machine downtime or issues that impacted patient care. Our experience with Eclipse v18.0 has been extremely positive. For more information, visit Varian. This is an adaptation of original content published by Varian.
