ESTRO 38 Abstract book

S1060 ESTRO 38

In Table 1 the number of errors ≥ 3 and 4 mm are given.

most reproducible phase (with the lowest standard deviation on all respiratory cycles, figure 2 ) confirming the treatment strategy to target the PTV on the phase 50% during the expiratory phase.

before NAL

direction AP

IS

RL

AP

IS

RL

>= 3 mm

>=3 mm

>=4 mm

>=4 mm

error

>=3 mm >=4 mm

Total (468)

29

62

43

9

31

16

% fractions 6.2% 13.2% 9.2%

1.9% 6.6% 3.4%

after NAL

direction AP

IS

RL

AP

IS

RL

≥

3

>= 3 mm

>= 4 mm

>= 4 mm

error

>= 3 mm >= 4 mm

mm

Conclusion Images from volunteers and patients were acquired using a 4D-MRI bSSFP (TrueFISP) sequence. After automated sorting with the method developed in this study, all the respiratory phases were imported into our TPS. Patient 4D-MRI could be registered with 4D-CT to capture the entire organs movements (liver cranio-caudal movements in red, Figure 1) during respiratory cycles and improve lesion delineation. References 1. Scorsetti et al. 2014 2. Nemtanu et al . 2017 3. Celicanin et al . 2015 EP-1945 Cost-effectiveness of the No Action Level Protocol for Head and Neck cancer patients P. Kukolowicz 1 , M. Mietelska 2 1 The Maria Sklodowska-Curie Memorial Cancer Center, Medical Physics, Warsaw, Poland ; 2 Warsaw University, Faculty of Physics, Warsaw, Poland Purpose or Objective Due to technological improvements of the workflow of radiotherapy more and more often the on-line set-up control is carried out. In this work we analyze the cost- effectiveness of the on-line and the NAL protocol for The applied database consists of daily set-up errors and time of portal control for 16 H&N patients measured in 468 treatment sessions. Patients were irradiated on the True Beam accelerator. CT VMAT or IMRT plans were prepared with 3 mm CTV-PTV margin. Two perpendicular kV portal images were taken in each session. The set-up errors were measured along three main axes with the commercially available Varian software. Next the NAL protocol was applied off-line for the data collected for each patient by subtracting the systematic error estimated with the first three sessions. For each direction the number of errors ≥ 3 and 4 mm were counted. Additionally, the time of set- up verification procedure was obtained from the data base (Aria Varian software). The time of set-up verification was the time from the first portal to the start of the treatment. Results Head&Neck patients. Material and Methods

Total (468)

20

14

12

8

4

1

% fractions 4.3% 3.0% 2.6%

1.7% 0.9% 0.2%

The average time of portal control for one session was 5.18 min. The NAL protocol enables to diminish the number of set-errors ≥ 3 mm for AP, IS, and RL directions to 4.3%, 3.0%, and 2.6% respectively. For AP directions number of sessions in which the set-up error was ≥4 mm was 1.7%. For the two other directions this result was even better. Taking into account the first free fractions in which portal control has to be made for 16 patients, the NAL protocol enabled to save about 2200 minutes on the treatment machine. Conclusion For H&N implementation the NAL protocol makes the set- up of the patients very reliable with very few errors ≥3 mm and incidental errors ≥4 mm. Application of the NAL protocol enables to save a lot of time on treatment machine. Instead of 16 patients the 21 patients may be treated. EP-1946 First french clinical experience using the Calypso tracking system for the prostate treatment J. Prunaretty 1 , D. Cirella 1 , P. Debuire 1 , N. Ailleres 1 , A. Morel 1 , S. Simeon 1 , S. Valdenaire 1 , P. Fenoglietto 1 1 CRLC Val d'Aurelle - Paul Lamarque, Radiotherapy, Montpellier, France Purpose or Objective To report the intrafraction prostate displacement using the Calypso system through a randomized phase II study (RCMI-GI). Material and Methods The Calypso System consists in an electromagnetic detection of implanted transponders. It is a real-time target tracking system that takes into account both inter- and intrafractional target motion. The RCMI-GI study will include 166 patients into arm 1 and arm 2 in 1:1 ratio. 83 patients will be treated with standard set-up margins (1 cm all around the prostate except 5mm in the posterior direction) and conventional IGRT protocol (daily CBCT). For the other ones, the treatment will be performed with reduced margins (3mm all around the prostate) using the Calypso® system. The prescribed dose is 80Gy in 40 fractions. To date, 21 patients were treated in arm 2 using VMAT and Calypso. At the beginning of each fraction, a CBCT was performed and “Set zero and track” function of the Calypso was applied. A 3mm-gating threshold was used during the treatment. The displacements ≥ 3mm in all directions were evaluated qualitatively and quantitatively.