Evaluating out-of-field doses during radiotherapy of paediatric brain tumours using lead shielding and flattening-filter free beams.

Paediatric radiotherapy comes at the expense of increased risk of late effects due to out-of-field dose caused not only by the treatment itself but also by image guidance. This study examined how the out-of-field dose to selected radiosensitive organs was affected by applying a 1 mm lead shielding during delivery of volumetric-modulated arc therapy (VMAT) for paediatric brain cancer. The study also investigated how the out-of-field dose to the same organs was affected by the use of flattening-filter free (FFF) beams.

Irregular breathing during 4DCT scanning of lung cancer patients: is the midventilation approach robust?

Background: With 4DCT the risk of introducing positional systematic errors in lung cancer radiotherapy can be minimised. A common approach is to plan on the phase bin of the 4DCT best representing the tumour's time-weighted mean position also called the midventilation scan. However breathing irregularities can introduce uncertainties and potentially misrepresent both the tumour trajectory and the determination of the midventilation phase.

Evaluation of methods for selecting the midventilation bin in 4DCT scans of lung cancer patients.

Background: In lung cancer radiotherapy, planning on the midventilation (MidV) bin of a four-dimensional (4D) CT scan can reduce the systematic errors introduced by respiratory tumour motion compared to conventional CT. In this study four different methods for MidV bin selection are evaluated.

Material And Methods: The study is based on 4DCT scans of 19 patients with a total of 23 peripheral lung tumours having peak-to-peak displacement ≥ 5 mm in at least one of the left-right (LR), anterior-posterior (AP) or cranio-caudal (CC) directions.

Artifacts in conventional computed tomography (CT) and free breathing four-dimensional CT induce uncertainty in gross tumor volume determination.

Purpose: Artifacts impacting the imaged tumor volume can be seen in conventional three-dimensional CT (3DCT) scans for planning of lung cancer radiotherapy but can be reduced with the use of respiration-correlated imaging, i.e., 4DCT or breathhold CT (BHCT) scans.

A treatment planning study of the potential of geometrical tracking for intensity modulated proton therapy of lung cancer.

Background: Proton therapy of lung cancer holds the potential for a reduction of the volume of irradiated normal lung tissue. In this work we investigate the robustness of intensity modulated proton therapy (IMPT) plans to motion, and evaluate a geometrical tumour tracking method to compensate for tumour motion.

Material And Methods: Seven patients with a nine targets with 4DCT scans were selected.

Deviations in delineated GTV caused by artefacts in 4DCT.

Background And Purpose: Four-dimensional computed tomography (4DCT) is used for breathing-adapted radiotherapy planning. Irregular breathing, large tumour motion or interpolation of images can cause artefacts in the 4DCT. This study evaluates the impact of artefacts on gross tumour volume (GTV) size.

Can audio coached 4D CT emulate free breathing during the treatment course?

Background: The image quality of 4DCT depends on breathing regularity. Respiratory audio coaching may improve regularity and reduce motion artefacts. We question the safety of coached planning 4DCT without coaching during treatment.