ESTRO 2022 - Abstract Book

S1659

Abstract book

ESTRO 2022

Fig. 1 Sagittal T2-weighted MRI comparing various gel volumes showing an excessive amount of gel (A) , note deformation of natural

anatomy, and optimal amount of gel (B) delineating full vaginal vault without distension. We observed with 10-15cc of gel the superior aspect of the vaginal vault and cervix is well visualised on T2 imaging, whilst tending not to unfold the natural fornices of the collapsed vagina (fig.2).

Fig. 2 A 38 year old female with cervical squamous cell carcinoma. ( A) Sagittal CT reconstruction with tampon in-situ. ( B) Sagittal T2-weighted image with vaginal gel in-situ. ( C) Axial CT with tampon in-situ. ( D ) Axial T2-weighted image with vaginal gel in-situ.

Conclusion The adaption of this diagnostic technique has facilitated more accurate contouring of the natural vaginal anatomy in gynaecological cancers. It is also useful in visualising disease extension into vaginal canal, which may have otherwise been obscured by the tampon. We have ceased the second ionising CT planning scan for gynaecological patients and removed the need for tampon insertion at the RT simulation session. We feel this is an example of the direct clinical benefits of increased integration of MRI simulation into routine RT clinical practice.

PO-1872 Tomotherapy replanning for Head and Neck patients : When? How? Why?

J. Rodrigues 1

1 CHUV Lausanne, radio-oncology, Lausanne, Switzerland

Purpose or Objective In our department, H&N patients are mainly treated with tomotherapy. Patients have up to 33 treatment sessions to complete for a total dose of 69.96 Gy. For each session, an image merge between the initial planning CT and the MVCT is