ESTRO 2024 - Abstract Book

S5542

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

A total of 540 images from 60 patients were acquired. Transitioning from single MV to single kV imaging did not significantly affect average random and systematic error values. However, the introduction of paired kV images and enhanced image quality resulted in increased pre-correction error values. The application of corrective shifts significantly improved these errors, bringing them well within tolerance levels and surpassing single MV and single kV image accuracy.(Table 1) The corrective kV imaging protocol considerably improved the final treatment position for breast cancer patients while reducing concomitant radiation doses. This also minimised the need for multiple reset up for patients. However, the time for imaging and treatment delivery increased by an average of 5 minutes.

Cohort 1

Cohort 2

Cohort

3

(pre

Cohort

3

(post

correction)

correction)

Vertica l

Lon g (cm)

Latera l (cm)

Vertica l

Lon g

Latera l (cm)

Vertica l (cm)

Lon g

Latera l (cm)

Vertica l (cm)

Lon g

Latera l (cm)

(cm)

(cm)

(cm

(cm)

(cm

)

)

Populatio n mean (µ) Systemati c error (∑)

-0.15

0.03

-0.10

-0.09

- 0.07

-0.04

-0.12

- 0.17

-0.09

-0.03

0.02

0.05

0.16

0.17

0.12

0.17

0.23

0.17

0.38

0.23

0.23

0.09

0.10

0.07

Random error (σ)

0.50

0.54

0.37

0.53

0.70

0.50

1.07

0.75

0.72

0.29

0.32

0.22

Table 1. Comparison of population means, systematic and random errors.

Conclusion:

The implementation of a corrective kV imaging protocol yielded substantial benefits, including superior image quality, enhanced treatment precision and reduced patient radiation exposure for breast cancer radiotherapy. While treatment times experienced a slight increase, the improved accuracy and safety profile support its potential as a standard practice in breast cancer treatment.

Keywords: Breast Radiotherapy Verification

1460

Digital Poster

Evaluation of respiratory motion in lung cancer SBRT using 4D CBCT with no external surrogates.

Valerio Pisoni 1,2 , Antonella Fogliata 3 , Federica Ferrario 1,2 , Sara Trivellato 4 , Stefano Arcangeli 1,2

1 Foundation IRCCS San Gerardo dei Tintori, Radiation Oncology, Monza, Italy. 2 University of Milan Bicocca, School of Medicine and Surgery, Milan, Italy. 3 Humanitas Research Hospital IRCCS, Medical Physics, Rozzano, Italy. 4 Foundation IRCCS San Gerardo dei Tintori, Medical Physics, Monza, Italy