S65
Brachytherapy - Gynaecology
ESTRO 2026
infusion, above the threshold for glucosuria in mice3. The large infusion volume caused bladder filling during the scan time, resulting in compression and translation of the tumours. The Δ ST% map from the z- spectra (Figure 1) and dynamic data (Figure 2) showed no detectable ST% increase in the tumours post infusion, though a significant change was observed in the bladder.
Digital Poster Highlight 2332 Chemical exchange saturation transfer for metabolic imaging of cervical tumours Madeline Rapley 1 , Warren Foltz 2 , Michael Milosevic 3,4 , Alexandra Rink 5,6 1 Medical Biophysics, University of Toronto, Toronto, Canada. 2 STTARR Innovation Centre, Department of Radiation Oncology, University Health Network, Toronto, Canada. 3 Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada. 4 Institute of Medical Science, University of Toronto, Toronto, Canada. 5 Medical Physics Department, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada. 6 Department of Radiation Oncology, University of Toronto, Toronto, Canada Purpose/Objective: Supplemental 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET) is associated with reduced interobserver variability in gross tumour volume delineation for magnetic resonance guided brachytherapy (MRgBT) of the cervix 1. 18F-FDG-PET is not practical to integrate in MRgBT, but an existing MRI technique, chemical exchange saturation transfer (CEST), may provide similar information on glucose metabolism. After a preliminary phantom study showing detectability of D-glucose (D-Glc) and D- glucosamine (D-GlcN) at biologically relevant concentrations using CEST, this study aims to characterize uptake and clearance of these agents in a cervical tumour orthotopic xenograft model. Material/Methods: ME180 tumours (human squamous cell carcinoma of the cervix) were grown orthotopically to 5-7mm diameter in female NOD/SCID mice (n=5) as previously described2. Blood glucose was measured (OneTouch Ultra2) before D-Glc infusion and after imaging. Imaging was performed using a 7T MR scanner (Bruker Biospec; 40 mm diameter quadrature RF coil). Z-spectra were acquired at a single slice using a CEST-RARE sequence (TR =10s, 128x80 matrix, RARE factor=16, NEX=1, 5s presaturation block pulse at 2µT, 29 frequency offsets between ±3.5 ppm), before and after glucose infusion. 120 µL 50% Dextrose (Pfizer), diluted to 360 µL in saline, was infused over 5 minutes (PHD 2000 programable syringe pump) through a teil vein catheter, giving a dose of ~3g/kg D-Glc. Dynamic data was acquired at 1 ppm with a temporal resolution of 30 seconds. Z-spectra were analyzed via asymmetry using open source CEST code (Moritz Zaiss, Matlab2023b) and dynamics were analyzed with custom Python code. Results: Blood glucose increased from 7.2±0.8 to >30 mmol/L (glucose monitor saturated) ~30 minutes post-
Conclusion: D-Glc was not detected within cervical tumours using CEST. Since D-Glc is quickly converted to lactate in cancers, there may have been no significant uptake to measure. We will compare a CEST-based arterial input function against external blood glucose measurements to validate the technique and investigate ex vivo quantification methods to confirm uptake in the tumours. All experiments will be repeated with D-GlcN, which is expected to uptake at a higher rate than D-Glc due to slow metabolism after phosphorylation4. Keywords: CEST-MRI, Cervical Cancer, Glucose
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