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Abstract #0445

Comparing APT-weighted MTRasym and LD-mapping for personalized radiotherapy target delineation of glioblastoma: A prospective pilot study.

Patrick L.Y. Tang1,2,3, Marion Smits1,2,4, Remi A. Nout3, Caroline van Rij1,3, Cleo Slagter1,3, Annemarie T. Swaak-Kragten1,3, Alejandra Méndez Romero1,3, and Esther A.H. Warnert1,2
1Brain Tumor Center, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, Netherlands, 2Department of Radiology & Nuclear medicine, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands, 3Department of Radiotherapy, Erasmus MC Cancer Institute, University Medical Center Rotterdam, Rotterdam, Netherlands, 4Medical Delta, Delft, Netherlands

Synopsis

Keywords: CEST / APT / NOE, Brain, Glioblastoma

Motivation: Microscopic tumor infiltration in glioblastoma cannot be depicted on conventional MRI. Therefore, the clinical target volume (CTV) for radiotherapy consists of the gross tumor volume (GTV) plus a 15-mm safety margin. This large expansion increases the risk of radiation-induced side-effects.

Goal(s): To explore the potential of APTw-CEST MRI for improved GTV delineation, ultimately enabling a CTV-margin reduction.

Approach: Radiotherapy planning MRI-acquisition included an APTw-CEST MRI-sequence. GTVs based on APTw MTRasym or LD-maps were defined and compared to the conventional GTVs and CTVs.

Results: Both APTw-CEST MRI-based GTVs were similar in size, significantly larger than the GTV, and significantly smaller than the CTV.

Impact: This prospective pilot study integrates APTw-CEST MRI into glioblastoma radiotherapy planning, enabling a reduction of the 15-mm CTV-margin, and construction of a personalized target area that only targets tumor infiltration. This minimizes radiation-induced side-effects and thus improves quality of life.

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