Table 4.

Results of Spearman’s correlation tests between parotid shrinkage and diffusion parameters during treatment

Variable at the 10th fraction	∆Vol10fr(%)		∆Volpost(%)
	Spearman’s Rho	p-value	Spearman’s Rho	p-value
ADC	0.121	0.285	0.103	0.383
Dt	0.286	0.011	0.289	0.013
F	−0.057	0.614	−0.232	0.047
D*	−0.114	0.314	0.122	0.299
D* × f	−0.153	0.176	−0.013	0.910
∆ADC	0.228	0.042	0.173	0.141
∆Dt	0.319	0.004	0.372	0.001
∆f	0.022	0.844	−0.242	0.038
∆D*	−0.117	0.301	0.192	0.101
∆D* × f	−0.119	0.293	0.096	0.416

Statistically significant p-values are bold. Abbreviations: ∆Vol_10fr Parotid shrinkage(%) at the 10th fraction, ∆Vol_post Parotid shrinkage(%) 8 weeks after RT, ADC Apparent diffusion coefficient, D_t Tissue diffusion coefficient, D* Perfusion-related diffusion coefficient, f(%) Perfusion fraction, D* × f Product of D* by f, ∆ADC ADC variation (%) relative to the pretreatment value (analogously for the other imaging variables)