In the TMLI phase I clinical trial, we evaluated the dose uniformity to the targets and the OAR dose constraints. Although the HI for PTV_ALL worsened with increasing prescription dose, compliance with OAR dose constraints was achieved in all patients.

The target motion should be considered when irradiating to the moving target with patient breathing. Dynamic tracking technique (DTT) which can make the irradiation field move dynamically by synchronizing the target motion have developed to resolve this problem. The purpose of this study is to propose the strategy to evaluate total geometric uncertainty (TGU) of DTT radiotherapy for lung cancers. Seventeen lung cancer patients that treated by DTT using gimbaled linac were included in this study to evaluate the TGU in each patient. In this study, TGU was evaluated based on the concept of ICRU Report 62, and "Guide to the Expression of Uncertainty in Measurement (GUM)". TGU calculation of DTT was considered by dividing into two components. One is patient specific uncertainty, and another is institution specific uncertainty. In patient specific uncertainty, residual target displacement (RTD) against centroid of fiducial markers that were estimated from 4DCT analysis in each respiratory phase, and other possible internal errors were included. On the other hand, in institution specific uncertainty, actual tracking error that was directly measured by gimbal tracking log and detected fiducial marker positions in kV X-ray images during treatment, and other possible set-up errors were included. According to the concept of ICRU Report 62 and GUM, our uncertainty calculation protocol were constructed. Finally, TGU in each direction was calculated as follows; TGU = Σμi+2×√Σσi2, here, i is a content of uncertainty of DTT, μi is systematic uncertainty of i, σi is random uncertainty of i. Root mean square error (RMSE) of [μ, σ] of RTD for all patients in LR, AP and SI directions were [0.8, 0.6] mm, [0.9, 0.7] mm and [1.4, 1.4] mm, respectively. Also, RMSE of [μ, σ] of actual tracking error for all patients in LR, AP and SI directions were [1.0, 0.4] mm, [1.0, 0.8] mm and [1.8, 1.3] mm, respectively. Average TGUL-R, TGUA-P and TGUS-I were 6.5 ± 0.7 mm, 7.2 ± 1.4 mm, 12.3 ± 2.4 mm, respectively. Table summarizes the calculated results of TGU in each patient. In this study, the calculation protocol of TGU for DTT based on ICRU Report 62 and GUM has proposed by separating patient specific uncertainty and institution specific uncertainty in each patient. Our proposed method is very helpful to estimate the margin of DTT therapy for lung cancer.Abstract TU_41_3299; Table 1The calculated results of TGU by proposed protocol in each patient.Patient numberL - R (mm)A - P (mm)S - I (mm)14.2 - 1.83.4 - 3.16.5 - 5.523.0 - 2.72.9 - 3.35.5 - 7.435.9 - 0.89.3 - 2.25.4 - 5.545.3 - 0.33.6 - 2.48.5 - 3.053.1 - 3.62.3 - 5.412.5 - 3.264.9 - 3.03.9 - 2.87.4 - 4.672.7 - 3.23.1 - 3.07.3 - 4.183.3 - 2.42.8 - 3.13.5 - 6.593.1 - 3.24.3 - 3.66.6 - 4.3104.4 - 2.63.5 - 4.810.8 - 8.7114.4 - 2.15.9 - 1.13.0 - 7.2123.5 - 2.32.6 - 3.86.2 - 4.2132.6 - 4.13.7 - 2.510.3 - 4.9142.8 - 3.25.6 - 3.58.5 - 4.0152.8 - 4.56.3 - 0.56.1 - 5.4163.0 - 4.96.0 - 1.78.6 - 2.8173.6 - 2.25.5 - 1.16.7 - 4.7average of TGU range6.57.212.3standard deviation of TGU range0.71.42.4 Open table in a new tab

We have developed the new dynamic moving phantom (DMP) with three axis drives to reproduce three-dimensional(3D) target motion plus one axis drive for body surface motion. The motion data for operating this phantom is able to be acquired by rehearsing dynamic tracking therapy (DTT) of a patient. In this study, the novel approach which reconstructs the 3D long time information from respiratory motion (RPM) data on the body surface during planning CT and the target motion measured by 4DCT is developed. First, the RPM data on body surface during planning CT in each patient was obtained by laser ranger (u(t)). Then, the average wave of u(t) when 4DCT are scanned was calculated and 3D target motion was obtained by analyzing 4DCT. Next, correlation functions between average wave and 3D target motion in LR, AP and SI directions were created. Finally, long time 3D target motion was generated by the correlation function with u(t) in each patient. Two different correlation models were tested. One is dual polynomial model which is composed of polynomial functions separated by inspiratory and expiratory phases (P(u(t))). Another one is simple linear fitting function (L(u(t))). RPM data of 8 lung cancer patients who participated in clinical trial with DTT using gimbaled linac were used in this study. The average absolute difference between actual target position that was already known from tracking log data and reconstructed position were calculated to evaluate two correlation models. The significance between the average absolute difference of L (u (t)) and that of P (u (t)) were evaluated by Wilcoxon's signed rank one-sided test. Table summarizes the result of the average of absolute difference in each patient. The difference between actual target position and reconstructed position by L(u(t)) in LR, AP and SI were 0.12±0.08 mm, 0.53±0.29 mm, 0.31±0.18 mm, respectively. On the other hand, those by P(u(t)) in LR, AP and SI were 0.23±0.14 mm, 0.87±0.54 mm, 0.69±0.40 mm, respectively (p = 0.018, 0.005, 0.027). The novel approach which reconstructs the 3D target motion from RPM data during planning CT and 3D target motion measured by 4DCT were shown. Dual polynomial model that we investigated in this study was better to reconstruct 3D target motion.Abstract 3619Pt.No.Dual polynomial modelLinear modelLR (mm)SI (mm)AP (mm)LR (mm)SI (mm)AP (mm)AVSDAVSDAVSDAVSDAVSDAVSD10.070.040.300.150.140.100.090.070.300.240.400.2720.220.130.490.300.390.250.220.130.520.351.070.5930.020.010.440.200.100.080.050.020.680.360.420.2740.130.060.480.270.060.060.220.090.630.360.160.1250.060.050.690.430.480.290.340.191.860.941.440.7460.200.170.530.250.210.140.540.320.500.290.430.2470.100.060.420.350.270.140.130.091.040.780.300.1680.120.130.870.420.840.410.270.171.400.981.290.81AV0.120.080.530.290.310.180.230.140.870.540.690.40 Open table in a new tab