Combined use of DWI, DCE-MRI & PET/CT in Treatment Response For Preoperative Chemoradiation in Primary Rectal Adenocarcinoma

Jing Gu¹, Tao Chan¹, Wailun LAW², JingBo Zhang³, Pek-Lan Khong¹

As functional imaging modalities, DWI, DCE-MRI, and PET/CT have been applied in monitoring treatment response. However, the underlying biophysical basis for changes of imaging parameters during a course of chemoradiation therapy (CRT) is far from fully understood. An increase of apparent diffusion coefficient (ADC), a quantitative parameter from DWI, suggests treatment-induced cell lysis and necrosis. However, increase in ADC can also result from change in vessel permeability due to radiation therapy. For this, DCE-MRI may provide useful information. On the other hand, late decrease in ADC can be considered result of tissue compaction and fibrosis or presence of residual active disease, which may be distinguished by PET/CT. So the aim of this study was to investigate DWI, DCE-MRI and PET/CT for response assessment over a course of pre-operative combined CRT for primary rectal adenocarcinoma, to see if the combination of different techniques can best predict biological behavior and clinical outcome.