Diffusion radiomics analysis of intratumoral heterogeneity in a murine prostate cancer model following radiotherapy: Pixelwise correlation with histology.
To investigate the biological meaning of apparent diffusion coefficient (ADC) values in tumors following radiotherapy.



Five mice bearing TRAMP-C1 tumor were half-irradiated with a dose of 15 Gy. Diffusion-weighted images, using multiple b-values from 0 to 3000 s/mm2, were acquired at 7T on day 6. ADC values calculated by a two-point estimate and monoexponential fitting of signal decay were compared between the irradiated and nonirradiated regions of the tumor. Pixelwise ADC maps were correlated with histological metrics including nuclear counts, nuclear sizes, nuclear spaces, cytoplasmic spaces, and extracellular spaces.



As compared with the nonirradiated region, the irradiated region exhibited significant increases in ADC, extracellular space, and nuclear size, and a significant decrease in nuclear counts (P < 0.001 for all). Optimal ADC to differentiate the irradiated from nonirradiated regions was achieved at a b-value of 800 s/mm2by the two-point method and monoexponential curve fitting. ADC positively correlated with extracellular spaces (r = 0.74) and nuclear sizes (r = 0.72), and negatively correlated with nuclear counts (r = -0.82, P < 0.001 for all).



As a radiomic biomarker, ADC maps correlating with histological metrics pixelwise could be a means of evaluating tumor heterogeneity and responses to radiotherapy.



1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:483-489.
Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital at Linkou, Taiwan.|Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taiwan.
Yu-Chun
YC
Lin
Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital at Linkou, Taiwan.|Clinical Phenome Center, Chang Gung Memorial Hospital at Linkou, Taiwan.|Radiation Biology Research Center, Institute for Radiological Research, Chang Gung University / Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan.
Gigin
G
Lin
Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taiwan.|Radiation Biology Research Center, Institute for Radiological Research, Chang Gung University / Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan.|Department of Radiation Oncology, Chang Gung Memorial Hospital at Linkou and Chang Gung University, Taoyuan, Taiwan.
Ji-Hong
JH
Hong
Department of Radiation Oncology, Chang Gung Memorial Hospital at Linkou and Chang Gung University, Taoyuan, Taiwan.
Yi-Ping
YP
Lin
Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taiwan.|Radiation Biology Research Center, Institute for Radiological Research, Chang Gung University / Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan.|Department of Radiation Oncology, Chang Gung Memorial Hospital at Linkou and Chang Gung University, Taoyuan, Taiwan.
Fang-Hsin
FH
Chen
Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital at Linkou, Taiwan.|Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taiwan.
Shu-Hang
SH
Ng
Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taiwan.|Radiation Biology Research Center, Institute for Radiological Research, Chang Gung University / Chang Gung Memorial Hospital, Linkou, Taoyuan, Taiwan.|Department of Radiation Oncology, Chang Gung Memorial Hospital at Linkou and Chang Gung University, Taoyuan, Taiwan.
Chun-Chieh
CC
Wang
D000465:Algorithms; D000818:Animals; D015415:Biomarkers; D045744:Cell Line, Tumor; D038524:Diffusion Magnetic Resonance Imaging; D007090:Image Interpretation, Computer-Assisted; D007091:Image Processing, Computer-Assisted; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009368:Neoplasm Transplantation; D011467:Prostate / Q000000981:diagnostic imaging*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011878:Radiotherapy; D015203:Reproducibility of Results; D012119:Respiration; D012815:Signal Processing, Computer-Assisted
D015415:Biomarkers
apparent diffusion coefficient; diffusion MRI; radiotherapy