Xia Ge^{1}, John A Engelbach^{1}, James D Quirk^{1}, Larry G Bretthorst^{1}, Joel R Garbow^{1,2}, and Joseph JH Ackerman^{1,2,3}

Triple negative breast cancer patient-derived xenographs were implanted in the 4th abdominal mammary fat pads of mice enrolled in a ~60 minute, multi-contrast, same-day (morning vs. afternoon), test-retest MRI protocol. Quantitative T1, T2, and ADC maps were acquired. Parameter distributions were characterized by standard statistical measures (mean, median, standard deviation, skewness, and kurtosis) and a Bayesian implementation of the maximum-entropy method-of-moments density function. TNBC PDX T2 maps were found to be markedly more robust to test-retest assessment compared to T1 and ADC maps. These results will inform studies employing MRI assessment of TNBC PDX response to docetaxel/carboplatin therapy.

Figure 1. Same-day (morning and afternoon) ADC test-retest
example for a small (64 µL) TNBC PDX tumor (dashed yellow region of interest).
The middle panel shows a single T2W transverse slice through the tumor (top)
and overlaid binned test-retest ADC histograms (middle) for the entire tumor
volume. The distribution mean, median, and standard deviation are shown below
the histogram. The left and right panels show the results for the maximum
entropy density function analysis.

Figure 2. Same-day (morning and afternoon) T2 test-retest
example for the same TNBC PDX tumor as in Figure 1. The middle panel shows a
single T2W transverse slice through the tumor (top) and overlaid binned test-retest
T2 histograms (middle) for the entire tumor volume. The distribution mean, median,
and standard deviation are shown below the histogram. The left and right panels
show the results for the maximum entropy density function analysis.

Figure 3. Bland Altman analysis of various
parameters characterizing TNBC PDX T1 distributions obtained from same-day
(morning and afternoon) test-retest scanning.
Shown are Bland Altman plots for the following test-retest T1
distribution parameters: mean, median, standard deviation, peak value of the
maximum entropy method of moments density function, skewness, and kurtosis.

Figure 4. Bland Altman analysis of various
parameters characterizing TNBC PDX T2 distributions obtained from same-day
(morning and afternoon) test-retest scanning.
Shown are Bland Altman plots for the following test-retest T2
distribution parameters: mean, median, standard deviation, peak value of the
maximum entropy method of moments density function, skewness, and kurtosis.

Figure 5. Bland Altman analysis of various
parameters characterizing TNBC PDX ADC distributions obtained from same-day
(morning and afternoon) test-retest scanning.
Shown are Bland Altman plots for the following test-retest ADC
distribution parameters: mean, median, standard deviation, peak value of the
maximum entropy method of moments density function, skewness, and kurtosis.