ESTRO 2024 - Abstract Book

S5483

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

ESTRO 2024

4. John HH, Carnell JH, Myra R, et al. Use of surface ‐ guided radiation therapy in combination with IGRT for setup and intrafraction motion monitoring during stereotactic body radiation therapy treatments of the lung and abdomen[J].J Appl Clin Med Phys, 2020,21(5): 48-55. 5. Katie Jasper, Baochang liu, Robert Olson, et al. Evidence-Based Planning Target Volume Margin Reduction for Modern Lung Stereotactic Ablative Radiation Therapy Using Deformable Registration [J]. Adv Radiat Oncol.2021, 6: 10075.

6. Lee S, Zheng Y, Podder T, et al. Tumor localization accuracy for high-precision radiotherapy during active breath hold [J]. Radiother Oncol , 2019,137:145–52.

7. Prado A, Zucca D, De la Casa M´A, et al. Intrafraction target shift comparison using two breath-hold systems in lung stereotactic body radiotherapy [J]. Phys Imaging Radiat Oncol, 2022,29:57–62.

8. Sebastian Sarudis, Anna Karlsson, Anna Bäck. Surface guided frameless positioning for lung stereotactic body radiation therapy [J].J Appl Clin Med Phys, 2021,22:215–226.

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Digital Poster

Can 1 mm PTV margin be used for radiosurgery patients laying on wedges?

Tessa Harderwijk, Lean Krikke, Enrica Seravalli, Marlies de Vries

University Medical Center Utrecht, Radiotherapy, Utrecht, Netherlands

Purpose/Objective:

At the UMC Utrecht, patients with single or multiple brain metastases are treated with stereotactic radiation therapy. Prior to the radiation treatment delivery, a conebeam computer tomography (CBCT) is performed in order to verify the patient position, followed by an online 6-D table position correction using the HexaPOD system (Elekta, Sweden). After this correction, a position verification (PV) CBCT is acquired to ensure that the patient has not moved as a consequence of the table correction. Subsequently, the patient is irradiated. After the treatment, a post-CBCT is acquired to verify if the patient intrafraction motion remained within ≤1mm and ≤1 degree according to the institutional protocol. All CBCT-CT registrations are performed using in the XVI software (Elekta, Sweden) using a clipbox encompassing the bony structures of the head with a Bone bone (T+R) registration algorithm. The patient is positioned on a baseplate with an individual headrest (Civco Medical Solutions, USA) and a 3-point mask (Macromedics, The Netherlands) (standard setup). Based on this immobilization, a 1mm gross target volume (GTV) to planning target volume (PTV) margin is used. When the patient cannot lie completely flat, one or multiple wedges and a standard headrest (Civco Medical Solutions, USA) are placed under the patient's head. The mask is fixated on a second baseplate laying under the wedges (Fig. 1 left).