Super-resolution ultrasound and MRI imaging for monitoring breast tumour response to radiotherapy
Megan Morris,
United Kingdom
PD-0826
Abstract
Super-resolution ultrasound and MRI imaging for monitoring breast tumour response to radiotherapy
Authors: Megan Morris1,2, Matthieu Toulemonde1, Victoria Sinnett3, Steven Allen4, Kate Downey4, Nina Tunariu2,4, Claire Lucy2,5, Lone Gothard2,5, Georgina Hopkinson4, Erica Scurr4, Emma Harris2,6, Mengxing Tang1, Matthew Blackledge2, Navita Somaiah2, Navita Somaiah5
1Imperial College London, Bioengineering, London, United Kingdom; 2The Institute of Cancer Research, Radiotherapy and Imaging, London, United Kingdom; 3The Royal Marsden NHS Foundation Trust, Radiology , London, United Kingdom; 4The Royal Marsden NHS Foundation Trust, Radiology, London, United Kingdom; 5The Royal Marsden NHS Foundation Trust, Breast Unit, London, United Kingdom; 6The Royal Marsden NHS Foundation Trust, Physics, London, United Kingdom
Show Affiliations
Hide Affiliations
Purpose or Objective
There are currently no specific protocols to stratify breast cancer patients based on tumour sensitivity to radiotherapy (RT). Tumours are associated with high cellularity, vascular permeability and chaotic microvasculature. Our hypothesis is that a novel imaging technique, Super-Resolution UltraSound (SRUS) [1] combined with biomarkers from dynamic-contrast enhanced and diffusion-weighted MRI (DCE/DW-MRI) will enable unprecedented quantification of tumour microvessel structure and dynamics. This will allow identification of radioresistance and detection of early relapse, enabling personalised treatment.
Material and Methods
In this study, patients are part of a trial led by the Institute of Cancer Research testing effectiveness of intra-tumoural H2O2 as a radiosensitiser. 2D SRUS and 3D DCE/DW-MRI of the breast tumours are acquired pre-RT and 2w, 6m and 12m post-RT (36Gy in twice weekly fractions of 6Gy). Super-resolution maps of tumour microvasculature were generated from high frame-rate contrast enhanced US acquisition by detecting intravenously injected, spatially isolated Sonovue contrast agents. 3D ADC (apparent diffusion coefficient) maps were generated from DW-MRI for measurement of cellularity and 3D AUC90 (area under 1/T1 curve for first 90 sec of contrast uptake) maps were generated from DCE-MRI for measurement of vascular permeability.
Results
Preliminary analysis comparing pre- and 2w post-RT images in 4 patients confirmed that breast tumour microvasculature can be imaged using SRUS (Fig 1) with remarkable clarity. A reduction in microvascular density was visually detected 2w post-RT in 3 out of 4 patients. There was an increase in mean ADC after RT for all patients apart from one (p-value=0.03, Fig 2). Lower ADC values reflect higher cellularity; therefore, our results suggest reduced tumour cellularity is detectable 2w post-RT. Overall no significant difference was detected in mean AUC90 values 2w post-RT (p-value=0.31, Fig 2), suggesting it may be too early to detect changes in vascular permeability using this measurement. The patients showing a reduction in microvasculature correspond to those with large increases in ADC (Fig 2, green & cyan plots).
Fig 1. B-mode images of tumour tissue (left) and corresponding SRUS images of tumour microvasculature (right) pre- (top) and 2w post-RT (bottom).
Fig 2. ADC (left) and AUC90 (right) values pre- and 2w post-RT. Colours correspond to the same patient. Fig 1 corresponds to the same patient as the green plots.
Conclusion
We have successfully demonstrated application of SRUS to study breast tumour microvasculature with high resolution. Initial pilot data shows that radiation induced changes can be detected as early as 2w post-RT, suggesting that this method, along with mean ADC, can be used to detect early response/resistance to RT and possibly early relapse. Further work will include correlating quantitative measurements from SRUS with MRI parameters.
1. Christensen-Jeffries et al. (2020) Ultrasound Med Biol 46(4):865-891