Differences in supratentorial white matter diffusion after radiotherapy – new biomarker of normal brain tissue damage?

Figures & data

Figure 1. Top row: patient with pituitary adenoma, example of ROI placement in parallel white matter areas. The ROI size is based on a 66 mm² circle, reduced in each case to the largest circular/oblong ROI that fit the white matter area between the relevant dose lines. Bottom row: patient with astrocytoma grade III, example of ROI placement in paired white matter areas. Left column: ADC-map placed as an unsmoothed overlay on T1 weighted images. Right column: Dose plan with absolute dose in steps of 5 Gy placed as an overlay on the T1 weighted images.

Table I. Diagnosis and treatment overview of the included patients.

Diagnose	Number of patients	Pre RT surgery/biopsy [Yes/No]	Radiation therapy [Gy/fractions]
Craniopharyngioma	1	Yes	50.4/28
Astrocytoma grade III	3	Yes	59.4/33
Pilocytic astrocytoma	1	Yes	45/25
Pituitary adenoma	6	Yes	45/25
Meningioma	8	Yes	54/30

RT, radiation therapy.

Table II. ADC and dose differences between paired white matter structures at unequal total radiation dose levels.

	High dose level	Low dose level	Mean diff	CI	P	N
Mean ADC	79.72	75.13	4.6	0.3;8.9	0.03	18
Mean dose	44.44	13.06	31.4	25.9;36.9	0.00	18

Mean diff = High dose level – Low dose level. CI, 95% confidence interval; n, number of patients; p, 2-sided p-value. ADC-units [10⁻⁵ mm²/s]. Dose-units [Gy].

Table III. Comparison of mean ADC-values in normal white matter and normal appearing white matter at different total radiation dose levels to the brain.

Number of patients	Normal white matter Mean ADC [10^−5 mm^2/s]	Irradiated white matter
		Dose [Gy]	Mean ADC [10^−5 mm^2/s]	Mean diff [10^−5 mm^2/s]	CI [10^−5 mm^2/s]	P
19	71.92	5	73.83	1.9	−1.8;5.6	0.29
19	71.92	15	77.74	5.8	1.5;10.1	0.01
19	71.92	25	77.72	5.8	2.4;9.2	0.002
18	72.14	35	78.07	5.9	2.9;9.0	0.0007
14	72.89	45	77.21	4.3	−0.2;8.9	0.06
6	73.30	55	69.26	−4.0	−15.0;6.9	0.39

Mean diff = mean ADC at dose level (×) – mean ADC normal white matter. CI, 95% confidence interval; p, 2-sided p-value.

Figure 2. Boxplot of mean ADC (× 10⁻⁵ mm²/s) for normal white matter (radiation total dose 0 Gy) and the irradiated normal appearing white matter (radiation total dose 5–55 Gy).