T1ρ for Radiotherapy Treatment Response Monitoring in Rectal Cancer Patients: A Pilot Study

Kooreman, Ernst S.; Tanaka, Max D.; Beek, Leon C. ter; Peters, Femke P.; Marijnen, Corrie A.M.; Heide, Uulke A. van der; Houdt, Petra J. van

doi:10.3390/jcm11071998

“…Along with being a non-invasive alternative to CT in terms of treatment planning as well as providing image-guidance during radiotherapy, MR-Linacs also enable MRI-specific methods such as functional imaging of head and neck cancer [ 16 – 19 ], but also functional imaging of the lung. Due to fractionated dose delivery, MR-Linacs even allow longitudinal functional data acquisition within the course of the patients’ treatment, which is especially valuable since it may permit early treatment response assessments [ 20 – 23 ].…”

Section: Introductionmentioning

confidence: 99%

Ventilation and perfusion MRI at a 0.35 T MR-Linac: feasibility and reproducibility study

Klaar

¹

,

Rabe

²

,

Gaaß

³

et al. 2023

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Background Hybrid devices that combine radiation therapy and MR-imaging have been introduced in the clinical routine for the treatment of lung cancer. This opened up not only possibilities in terms of accurate tumor tracking, dose delivery and adapted treatment planning, but also functional lung imaging. The aim of this study was to show the feasibility of Non-uniform Fourier Decomposition (NuFD) MRI at a 0.35 T MR-Linac as a potential treatment response assessment tool, and propose two signal normalization strategies for enhancing the reproducibility of the results. Methods Ten healthy volunteers (median age 28 ± 8 years, five female, five male) were repeatedly scanned at a 0.35 T MR-Linac using an optimized 2D+t balanced steady-state free precession (bSSFP) sequence for two coronal slice positions. Image series were acquired in normal free breathing with breaks inside and outside the scanner as well as deep and shallow breathing. Ventilation- and perfusion-weighted maps were generated for each image series using NuFD. For intra-volunteer ventilation map reproducibility, a normalization factor was defined based on the linear correlation of the ventilation signal and diaphragm position of each scan as well as the diaphragm motion amplitude of a reference scan. This allowed for the correction of signal dependency on the diaphragm motion amplitude, which varies with breathing patterns. The second strategy, which can be used for ventilation and perfusion, eliminates the dependency on the signal amplitude by normalizing the ventilation/perfusion maps with the average ventilation/perfusion signal within a selected region-of-interest (ROI). The position and size dependency of this ROI was analyzed. To evaluate the performance of both approaches, the normalized ventilation/perfusion-weighted maps were compared and the deviation of the mean ventilation/perfusion signal from the reference was calculated for each scan. Wilcoxon signed-rank tests were performed to test whether the normalization methods can significantly improve the reproducibility of the ventilation/perfusion maps. Results The ventilation- and perfusion-weighted maps generated with the NuFD algorithm demonstrated a mostly homogenous distribution of signal intensity as expected for healthy volunteers regardless of the breathing maneuver and slice position. Evaluation of the ROI’s size and position dependency showed small differences in the performance. Applying both normalization strategies improved the reproducibility of the ventilation by reducing the median deviation of all scans to 9.1%, 5.7% and 8.6% for the diaphragm-based, the best and worst performing ROI-based normalization, respectively, compared to 29.5% for the non-normalized scans. The significance of this improvement was confirmed by the Wilcoxon signed rank test with $$p\, <\, 0.01$$ p < 0.01 at $$\alpha \, =\, 0.05$$ α = 0.05 . A comparison of the techniques against each other revealed a significant difference in the performance between best ROI-based normalization and worst ROI ($$p\, =\, 0.01$$ p = 0.01 ) and between best ROI-based normalization and scaling factor ($$p\, =\, 0.02$$ p = 0.02 ), but not between scaling factor and worst ROI ($$p\, =\, 0.71$$ p = 0.71 ). Using the ROI-based approach for the perfusion-maps, the uncorrected deviation of 10.2% was reduced to 5.3%, which was shown to be significant ($$p\, <\, 0.01$$ p < 0.01 ). Conclusions Using NuFD for non-contrast enhanced functional lung MRI at a 0.35 T MR-Linac is feasible and produces plausible ventilation- and perfusion-weighted maps for volunteers without history of chronic pulmonary diseases utilizing different breathing patterns. The reproducibility of the results in repeated scans significantly benefits from the introduction of the two normalization strategies, making NuFD a potential candidate for fast and robust early treatment response assessment of lung cancer patients during MR-guided radiotherapy.

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Treatment Planning Considerations for an MR-Linac

Cunningham,

Dolan,

Aldridge

et al. 2024

A Practical Guide to MR-Linac

0

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Predictive markers for head and neck cancer treatment response: T1rho imaging in nasopharyngeal carcinoma

Ai,

King,

Tsang

et al. 2024

Eur Radiol

0

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Objectives To investigate the potential of T1rho, a new quantitative imaging sequence for cancer, for pre and early intra-treatment prediction of treatment response in nasopharyngeal carcinoma (NPC) and compare the results with those of diffusion-weighted imaging (DWI). Materials and methods T1rho and DWI imaging of primary NPCs were performed pre- and early intra-treatment in 41 prospectively recruited patients. The mean preT1rho, preADC, intraT1rho, intraADC, and % changes in T1rho (ΔT1rho%) and ADC (ΔADC%) were compared between residual and non-residual groups based on biopsy in all patients after chemoradiotherapy (CRT) with (n = 29) or without (n = 12) induction chemotherapy (IC), and between responders and non-responders to IC in the subgroup who received IC, using Mann–Whitney U-test. A p-value of < 0.05 indicated statistical significance. Results Significant early intra-treatment changes in mean T1rho (p = 0.049) and mean ADC (p < 0.01) were detected (using paired t-test), most showing a decrease in T1rho (63.4%) and an increase in ADC (95.1%). Responders to IC (n = 17), compared to non-responders (n = 12), showed higher preT1rho (64.0 ms vs 66.5 ms) and a greater decrease in ΔT1rho% (− 7.5% vs 1.3%) (p < 0.05). The non-residual group after CRT (n = 35), compared to the residual group (n = 6), showed higher intraADC (0.96 vs 1.09 × 10−3 mm2/s) and greater increase in ΔADC% (11.7% vs 27.0%) (p = 0.02). Conclusion Early intra-treatment changes are detectable on T1rho and show potential to predict tumour shrinkage after IC. T1rho may be complementary to DWI, which, unlike T1rho, did not predict response to IC but did predict non-residual disease after CRT. Clinical relevance statement T1rho has the potential to complement DWI in the prediction of treatment response. Unlike DWI, it predicted shrinkage of the primary NPC after IC but not residual disease after CRT. Key Points Changes in T1rho were detected early during cancer treatment for NPC. Pre-treatment and early intra-treatment change in T1rho predicted response to IC, but not residual disease after CRT. T1rho can be used to complement DWI with DWI predicting residual disease after CRT.

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T1ρ for Radiotherapy Treatment Response Monitoring in Rectal Cancer Patients: A Pilot Study

Cited by 4 publications

References 19 publications

Ventilation and perfusion MRI at a 0.35 T MR-Linac: feasibility and reproducibility study

Ventilation and perfusion MRI at a 0.35 T MR-Linac: feasibility and reproducibility study

Treatment Planning Considerations for an MR-Linac

Predictive markers for head and neck cancer treatment response: T1rho imaging in nasopharyngeal carcinoma

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