Ingle Manasi, Blackledge Matthew, White Ingrid, Wetscherek Andreas, Lalondrelle Susan, Hafeez Shaista, Bhide Shreerang
The Royal Marsden Hospital NHS Trust, 203 Fulham Road, London SW3 6JJ, UK.
The Institute of Cancer Research, 123 Old Brompton Road, London SW7 3RP, UK.
Phys Imaging Radiat Oncol. 2022 Jun 10;23:32-37. doi: 10.1016/j.phro.2022.06.003. eCollection 2022 Jul.
Magnetic resonance imaging integrated linear accelerator (MR-Linac) platforms enable acquisition of diffusion weighted imaging (DWI) during treatment providing potential information about treatment response. Obtaining DWI on these platforms is technically different from diagnostic magnetic resonance imaging (MRI) scanners. The aim of this project was to determine feasibility of obtaining DWI and calculating apparent diffusion coefficient (ADC) parameters longitudinally in rectal cancer patients on the MR-Linac.
Nine patients undergoing treatment on MR-Linac had DWI acquired using b-values 0, 30, 150, 500 s/mm. Gross tumour volume (GTV) and normal tissue was delineated on DWI throughout treatment and median ADC was calculated using an in-house tool (pyOsirix ®).
Seven out of nine patients were included in the analysis; all demonstrated downstaging at follow-up. A total of 63 out of 70 DWI were analysed (7 excluded due to poor image quality). An increasing trend of ADC median for GTV (1.15 × 10 mm/s interquartile range (IQ): 1.05-1.17 vs 1.59 × 10 mm/s IQ: 1.37 - 1.64; ), correlating to treatment response. In comparison ADC median for normal tissue remained the same between first and last fraction (1.61 × 10 mm/s IQ: 1.56-1.71 vs 1.67 × 10 mm/s IQ: 1.37-2.00; p = 0.9375).
DWI assessment in rectal cancer patients on MR-Linac is feasible. Initial results provide foundations for further studies to determine DWI use for treatment adaptation in rectal cancer.
磁共振成像集成直线加速器（MR-Linac）平台能够在治疗期间采集扩散加权成像（DWI），提供有关治疗反应的潜在信息。在这些平台上获取DWI在技术上与诊断性磁共振成像（MRI）扫描仪不同。本项目的目的是确定在MR-Linac上对直肠癌患者纵向获取DWI并计算表观扩散系数（ADC）参数的可行性。
9名在MR-Linac上接受治疗的患者使用b值为0、30、150、500 s/mm²的序列进行DWI采集。在整个治疗过程中，在DWI上勾画出大体肿瘤体积（GTV）和正常组织，并使用内部工具（pyOsirix®）计算ADC中位数。
9名患者中有7名纳入分析；所有患者在随访时均显示分期降低。共分析了70次DWI中的63次（7次因图像质量差而排除）。GTV的ADC中位数呈上升趋势（1.15×10⁻³mm²/s，四分位间距（IQ）：1.05 - 1.17 vs 1.59×10⁻³mm²/s，IQ：1.37 - 1.64；），与治疗反应相关。相比之下，正常组织的ADC中位数在首次和最后一次分割之间保持不变（1.61×10⁻³mm²/s，IQ：1.56 - 1.71 vs 1.67×10⁻³mm²/s，IQ：1.37 - 2.00；p = 0.9375）。
在MR-Linac上对直肠癌患者进行DWI评估是可行的。初步结果为进一步研究确定DWI在直肠癌治疗适应性中的应用奠定了基础。
