Development of a physical geometric phantom for deformable image registration credentialing of radiotherapy centers for a clinical trial

Abstract

This study aimed to develop a physical geometric phantom for the deformable image registration (DIR) credentialing of radiotherapy centers for a clinical trial and tested the feasibility of the proposed phantom at multiple domestic and international institutions. Methods and materials: The phantom reproduced tumor shrinkage, rectum shape change, and body shrinkage using several physical phantoms with custom inserts. We tested the feasibility of the proposed phantom using 5 DIR patterns at 17 domestic and 2 international institutions (21 datasets). Eight institutions used the MIM software (MIM Software Inc, Cleveland, OH); seven used Velocity (Varian Medical Systems, Palo Alto, CA), and six used RayStation (RaySearch Laboratories, Stockholm, Sweden). The DIR accuracy was evaluated using the Dice similarity coefficient (DSC) and Hausdorff distance (HD).Results: The mean and one standard deviation (SD) values (range) of DSC were 0.909 AE 0.088 (0.434-0.984) and 0.909 AE 0.048 (0.726-0.972) for tumor and rectum proxies, respectively. The mean and one SD values (range) of the HD value were 5. ) (mm) for the tumor and rectum proxies, respectively. In three patterns evaluating the DIR accuracy within the entire phantom, 61.9% of the data had more than a DSC of 0.8 in both tumor and rectum proxies. In two patterns evaluating the DIR accuracy by focusing on tumor and rectum proxies, all data had more than a DSC of 0.8 in both tumor and rectum proxies. Conclusions:The wide range of DIR performance highlights the importance of optimizing the DIR process. Thus, the proposed method has considerable potential as an evaluation tool for DIR credentialing and quality assurance.

Dosimetric impact of deformable image registration using radiophotoluminescent glass dosimeters with a physical geometric phantom

“…Several studies have evaluated DIR accuracy using many DIR algorithm. 13,14,17,41 These studies showed that the DIR accuracy strongly depended on the DIR algorithm and procedure. Our result was consistent with their studies.…”

“…The physical phantom configuration with various inserts proposed in this study is an improved version of the phantom originally developed and reported by Kadoya et al. 17 The physical size of improved phantom was same as the original phantom. The physical size of large phantom had a length, width, and height of 30, 8, and 15 cm, respectively.…”

“… 12 , 13 , 14 , 15 At present, there are many commercially available DIR software programs in clinical practice, including Velocity AI (Varian Medical Systems, Palo Alto), RayStation (RaySearch Laboratories, Stockholm, Sweden) and MIM Software (MIM Software Inc, Cleveland). 13 , 16 , 17 Velocity used intensity‐based DIR, and structure‐based DIR. RayStation used hybrid intensity‐based and structure‐based DIR, and biomechanically based DIR.…”

“…This phantom can be used to evaluate both geometric and dosimetric DIR accuracy. 17 Radiophotoluminescent glass dosimeters (RPLDs) were selected to measure dose because of their many advantages such as small detector size, good reproducibility, small effective readout area, wide measurable dose range, repeatable readout, and small fading effect. 28 Although several previous studies have evaluated dose accumulation based on DIR, 18 , 29 , 30 none of these studies has used RPLDs for evaluation of measured dose accumulation.…”

“…Several studies have reported that DIR accuracy depends on the DIR software, algorithm, parameter settings, and procedures 12–15 . At present, there are many commercially available DIR software programs in clinical practice, including Velocity AI (Varian Medical Systems, Palo Alto), RayStation (RaySearch Laboratories, Stockholm, Sweden) and MIM Software (MIM Software Inc, Cleveland) 13,16,17 . Velocity used intensity‐based DIR, and structure‐based DIR.…”