Efficacy and safety assessment of an ultrasound-based thermal treatment of varicose veins in a sheep model

Figures & data

Figure 1. Echopulse ® HIFU device.

Figure 2. Longitudinal (a) and transverse (b) views of the positioning of the thermocouple TC1 in the vein. Spots are referred by their numbers.

Figure 3. Illustration of the change of frame of reference with one thermocouple for sake of clarity. Delivering five pulses (①, ②, ③, ④, ⑤) at given positions (symbolized by crosses) and measuring the temperature with one thermocouple into the vein at fixed locations is considered equivalent to the virtual situation where one pulse would be delivered and five thermocouples would acquire temperatures at the same positions. On the right, TCY with Y ∈ [1–5] represents a virtual thermocouple that measures the temperature rise during pulse Y.

Table 1. Clinical signs assessed after HIFU treatments.

Clinical signs evaluated	Normal	Abnormal
Appetite	9/9	0/9
Attitude	9/9	0/9
Fecal soiling	9/9	0/9
Tooth grinding	9/9	0/9
Attitude/Mentation	9/9	0/9
Activity	9/9	0/9
Head/neck position	9/9	0/9
Musculoskeletal	9/9	0/9
Alertness	9/9	0/9
Coughing	9/9	0/9
Ear position	9/9	0/9
Paws/legs	9/9	0/9
Gait/Posture	9/9	0/9
Sneezing	9/9	0/9
Breathing	9/9	0/9
Social behavior	9/9	0/9
Drinking	9/9	0/9
Coat condition	9/9	0/9
Face/Muzzle	9/9	0/9

Table 2. Maximum temperatures recorded by each thermocouple during each treatment performed in both left and right hind limb.

Laterality	Treatment ID	Thermocouple ID	Maximum temperature (°C)
Left	1	TC1	88
		TC2	78
	2	TC1	92
		TC2	84
	3	TC1	88
		TC2	90
	4	TC1	88
		TC2	82
	5	TC1	91
		TC2	92
Right	1	TC1	95
		TC2	83
	2	TC1	100
		TC2	92
	3	TC1	96
		TC2	89
	4	TC1	103
		TC2	86
	5	TC1	101
		TC2	87

Figure 4. Illustration of temperature profiles measured by the thermocouple TC1 during the treatment #3 in the right vein for each of the y-locations before spatial registration (a) and example of spatial registration of the data acquired by the thermocouple TC1 during the treatment #3 (b).

Figure 5. Estimated spatiotemporal temperature distribution for one pulse.

Figure 6. Spatial profile of $\Omega (y,t_f)$ along the vein after one pulse. $\mathrm{ }\Omega (y,t_f)$ is capped to 5 since it formally corresponds to 99 % of collagen denaturation.

Figure 7. Ultrasound images of the lateral saphenous vein (pointed by a white arrow) of a sheep before exposure (a) and immediately after exposure (b).The exposed vein has a reduced lumen and a hyper-echoic mark (pointed by a yellow arrowhead) is visible.

Figure 8. B-mode image after HIFU procedure showing a vein diameter constriction and blurred vascular contours.

Figure 9. Ultrasound images showing a non-compressible treated vein at 30 days post-treatment (left column) and a compressible untreated vein (right column). Veins are pointed by white arrows. (a) and (b) represent respectively the sheep veins before and after external ultrasound compression.

Figure 10. Color Doppler ultrasound image showing the absence of flow in a sheep vein (white arrow) 60 days after treatments.

Figure 11. B-mode image of a sheep vein (white arrow) taken 90 days after sonications and showing complete fibrosis of the treated segment.

Table 3. Imaging findings synthesis.

Animal group	D30	D60	D90
Number of veins showing lack of Doppler signal	6/6	5/6	4/6
Number of veins showing echogeneicity	4/6	5/6	2/6

Figure 12. Representative illustrations of HIFU lesions in vascular tissue. (a) H&E-section of a vein extracted 30 days after treatment. HIFU lesion shows vein wall hyalinization (arrows), thrombus (T) and necrotic perivascular adipose tissue (arrowheads). (b) H&E-section of a vein extracted at 60 days. Thrombus (T), fibroblast infiltration (double arrows) and residual media hyalinization (arrows) are observed. (c) GET-section of a vein extracted at 90 days and presenting fibrocellular thrombus (T), media fibrosis (arrows) and perivascular fibrosis (F).

Figure 13. Typical HIFU lesions in perivenous collateral tissues. (a) GET-section of a superficial perivenous muscle extracted at 30 days; the area under the dotted line presents focal muscle necrosis with fibrosis (arrowhead) and residual necrotic muscle tissue (asterisk). (b) GET-section of a superficial perivenous muscle harvested 60 days post-treatment (GET); the area above the dotted line shows necrosis and regeneration with fibrosis in the muscle.

Table 4. Histopathological findings synthesis.

	Histopathological findings
	Vascular changes							Perivenous changes			Inflammatory signals
Animals group	Vein wall hyalinization	Adventitial collagen hyalinization	Vein wall fibrosis	Vein thrombosis	Vein occlusion	Vein wall perforation	Vein charring	Perivascular fibrosis	Perivascular fat necrosis	Superficial or deep Muscle necrosis	Histiocytes	Foreign body giant cells
D30	3/6	3/6	6/6	6/6	6/6	0/6	0/6	6/6	6/6	7/12	6/6	6/6
D60	1/6	0/6	4/6	4/6	4/6	0/6	0/6	5/6	0/6	5/12	1/6	1/6
D90	0/6	0/6	5/6	1/6	1/6	0/6	0/6	4/6	0/6	1/12	0/6	0/6

Table 5. Vascular thermal damage computed for different exposure parameters reported in the studies conducted by Martinot el al. [25] and Fujiwara et al. [27].

Study	[27]	[27]	[27]	[25]	[25]
Duration (s)	5	5	10	[3–4]	[3–4]
Peak temperature (°C)	46	97	48	54	77
Accumulated thermal damage $\mathrm{\Omega }$	1.2 × 10^−6	5.8 × 103	6.4 × 10^−6	[3.7 × 10^−5 − 4.9 × 10^−5]	[1.2–1.6]

Values in bold are above the threshold of first noticeable irreversible damage.

Figure 14. Illustration of the spatial registration process.

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