K Sheikh^1,2*, J Lee¹, R Seethamraju³, T Benkert⁴, H Bhat³, B Daniel⁵, D Song¹, A Viswanathan¹, E Schmidt¹, (1) Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, (2) The Johns Hopkins Proton Center, Washington, DC (3) Siemens Medical Solutions, Boston MA, (4) MR Applications Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany, (5) Department of Radiology, Stanford University, Stanford, CA

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  K Sheikh

TH-D-BRC-4 (Thursday, 7/14/2022) 11:00 AM - 12:00 PM [Eastern Time (GMT-4)]

Ballroom C

Purpose: To evaluate the percentage of gynecological fibrosis using novel UTE methods pre-, during (33Gy)-, and post (45Gy)-radiotherapy.

Methods: Patients underwent whole pelvis irradiation using VMAT. MR images were acquired pre/during/post -EBRT on 1.5T scanner (Siemens Aera/Sola) using a prototype stack-of-spirals dual-echo, inversion-recovery IR-UTE sequence (TE1,2=50, 2690µs, resolution=1.0×1.0×2.5mm³). To evaluate acute (diffuse) fibrosis (Fᴬ), which has a short TE and T1, TI=60ms or 80ms, TE₂ images were subtracted from TE₁ images . Chronic fibrosis (Fᶜ), with the longest contrast uptake time, was evaluated using TE₁ of (late-gadolinium-enhancement) LGE-UTE, TI=200ms, acquired 10-13 min after contrast-injection. Images were registered to the simulation CT, and targets were propagated onto the MR images. UTE images were segmented using region-growing (RayStation 10A, Stockholm). Acute fibrosis (Fᴬ) and chronic fibrosis (Fᶜ) regions were segmented on the non-contrast STIR-UTE and on the LGE-UTE, respectively, and propagated onto T2w images. The contours were cropped to remain within the CTV contour. Percentages of the Fᴬ and Fᶜ within the CTV were determined and compared pre-, on- and post-EBRT using an ANOVA with repeated measures with a Greenhouse-Geisser correction.

Results: In seven gynecological patients treated with whole pelvis irradiation, pre-treatment, on-treatment, and post-treatment Fᴬ/Fᶜ were: 11±11%/5±2%, 19±8%/12±10%, and 34±15%/18±10%, respectively. The mean Fᴬ were statistically significantly different (F(1.97, 11.83) = 8.11, p < .01) across time points. Similarly, the mean Fᶜ were statistically significantly different (F(1.36, 8.17) = 7.64, p = .02) across all time points. Pairwise comparisons demonstrated that pre- and post-treatment Fᴬ and Fᶜ were significantly different (p=.03). Fᴬ and Fᶜ grew during radiotherapy, with Fᴬ converting to Fᶜ at later time-points.

Conclusion: In patients treated with pelvic VMAT, Fᴬ and Fᶜ increased over the course of radiation therapy. Identifying fibrosis progression offers a means to achieve response-driven adaptive radiotherapy, potentially leading to improved outcome with reduced toxicity.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by the National Institutes of Health under Grant No. R01CA237005.

Keywords

Not Applicable / None Entered.

Taxonomy

IM/TH- MRI in Radiation Therapy: MRI for treatment planning

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