Table 4.

Key qualitative observations from histology, in vivo post‐therapy 3T MR imaging, and ex vivo 9.4 T MR imaging for each treatment

	Histological observation
	Untreated tissue	Non‐heat‐fixed lesions	Heat‐fixed lesions
Appearance on H&E stain	Nucleated cells, intact epithelium	Contiguous region of near‐complete epithelial sloughing and cell death	Heat‐fixed area resembling untreated tissue, surrounded by boundary of near‐complete epithelial sloughing and cell death
Appearance on 3T post‐therapy imaging (compared with pre‐therapy imaging)
T1W imaging	No change	Hyperintense or no change	Hyperintense
T2W imaging	Slightly hyperintense or no change	Hyperintense or no change	Hypointense (or hypo‐ and hyperintense) or no change
ADC	No change	Decreased or no change	Decreased; central area of unchanged ADC in some cases
Appearance on 9.4 T imaging, (compared with untreated tissue)
T1	N/A	Decreased; spatially varying changes in some cases	Decreased; spatially varying changes in some cases
T2	N/A	Increased or no change; spatially varying changes in some cases	Increased or no change; spatially varying changes in some cases
ADC	N/A	Decreased or no change	Decreased or no change; ring‐shaped area of reduced ADC in most casesa

All 3T post‐therapy imaging was acquired 5 min after MR thermometry indicated that the treatment zone had returned to 37–39°C. MR scan parameters for 3T and 9.4 T imaging are given in Tables 1 and 2, respectively.

^aFeature is significantly more frequent in heat‐fixed lesions.