ESTRO 2024 - Abstract Book

S3827

Physics - Image acquisition and processing

ESTRO 2024

Tumour hypoxia is a recognised cause of radiotherapy treatment resistance in head and neck squamous cell carcinoma (HNSCC) 1-3 . Although hypoxia modification strategies such as boost doses of radiation to hypoxic tumour regions exist, they have yet to garner routine clinical use in part due to the lack of readily accessible methods of determining and mapping tumour hypoxia 4,5 . We investigated if a hypoxia imaging technique called oxygen-enhanced MRI (OE-MRI) 6 could be performed in patients with HNSCC on a clinical MRI scanner using routinely available equipment and if this technique could discriminate tumours more and less likely to respond to curative intent radiotherapy.

Material/Methods:

A volumetric MRI protocol for dynamic T 1 relaxation time mapping was implemented on 1.5T clinical scanners using only routinely available clinical equipment (table 1). The study protocol was added to a routine clinical MRI scan performed as part of the routine diagnostic workup for patients with suspected HNSCC. Participants were scanned breathing room air and during high flow oxygen administration. Oxygen induced changes in T 1 times (ΔT 1 ) were measured in the parotid, submandibular and thyroid glands as well as in malignant tissue. Estimates of primary tumour hypoxic fractions were determined as the percent of voxels failing to show statistically significant shortening of T 1 times with oxygen. Response to curative intent radiotherapy was assessed on post-treatment 19 FDG-PET scanning and associations with tumour averaged ΔT 1 times and tumour hypoxic fraction estimates were determined. The study was registered on ClinicalTrials.gov, NCT04724096. All participants provided written informed consent. Patients’ treatment was unaffected by the study.

Parameter

OE-MRI

3D spoiled gradient echo

Sequence type

Orientation

Axial

TR / TE (ms)

10 / 1.27

FA (°)

2 / 18

Bandwidth (Hz/pixel)

399

FOV (mm) / Matrix

200 / 128

Slices

72 x 2.5mm

Number dynamics

40

Oxygen on

3min34s

Acquisition time / single dynamic 8min28s / 12s