Feasibility of volumetric MRI-guided high intensity focused ultrasound (MR-HIFU) for painful bone metastases

Table 2 Treatment parameters (chronological order)

Treatment	Duration (min)	N treatment cells (n sonications)	Treatment cell diameter (mm)	Acoustic power (W) median, range	Sonication energy (kJ) median, range	Total delivered energy (kJ)	Temperature (°C) median, range	Ablation approach^b
1a^a	40	2 (10)	4	100 (40–140)	2.0 (0.8–2.8)	17.5	-	Soft tissue
1b^a	20	3 (6)	2	50 (40–60)	1.0 (0.8–1.2)	6.0	-	Soft tissue
2	41	5 (6)	2, 4	80 (50–100)	1.5 (0.9–1.9)	8.8	43.9 (39.3–49.0)	Soft tissue
3	37	6 (10)	4	110 (90–120)	1.8 (1.1–1.9)	16.6	63.1 (56.3–74.6)	Near field
4	45	7 (15)	4, 8	120 (60–160)	2.2 (1.0–3.0)	31.3	47.3 (43.1–50.2)	Soft tissue
5a	37	10 (11)	4	50 (50–70)	0.8 (0.8–1.1)	10.2	56.2 (48.1–60.7)	Near field
6	73	18 (28)	4	100 (50–130)	1.6 (0.6–2.1)	42.4	55.2 (45.3–60.4)	Near field
7	49	16 (19)	4	130 (70–150)	2.1 (1.1–3.0)	39.1	64.8 (51.3–75.5)	In front of cortex^c
5b	69	20 (22)	4,8	40 (30–50)	0.6 (0.4–1.0)	14.9	60.9 (48.4–70.9)	Direct
8	68	22 (25)	4	120 (90–150)	1.9 (1.4–2.4)	48.4	56.1 (40.5–65.6)	Near field
9	71	21 (22)	8, 12	150 (70–150)	3.0 (2.0–3.0)	62.6	51.4 (41.9–67.8)	Soft tissue
10	39	9 (15)	4	20 (20–20)	0.3 (0.3–0.3)	4.2	63.0 (52.3–67.5)	Direct
11	45	12 (12)	4	40 (40–60)	0.6 (0.6–1.0)	7.4	64.4 (58.4–74.8)	Direct

Abbreviations: °C degrees Celsius, mm millimeter, min minutes, kJ kilojoule, W watt, CR complete response, PR partial response, NR no response.
^aIn treatment 1a and 1b, no representative temperature data were available due to susceptibility artifacts caused by internal fixation material. Treatment 1b was terminated early due to severe susceptibility artifacts (targeted volume too close to fixation material).
^bDirect approach: the treatment cell was positioned on the cortical surface. Near-field approach: the treatment cells were positioned 10 mm distal to the cortical bone. Soft-tissue approach: in lesions with complete cortical destruction, the treatment cells were positioned in the tumor mass itself.
^cBecause of lungs in the far field, for safety reasons, treatment cells were positioned in the tumor mass in front of the cortical bone.

ISSN: 2050-5736