Renal ablation using magnetic resonance-guided high intensity focused ultrasound: Magnetic resonance imaging and histopathology assessment

Table 1 Multiple magnetic resonance imaging sequences used for temperature monitoring, characterization and quantification of ablated kidneys

Pulse sequence	TR (ms)	TE (ms)	ETL	rBW (kHz)	Flip angle (degree)	Slice thickness	Matrix size	NEX	Acquisition time (s)
T2-W thermometry	210	18.3	12	15.63	35	4	256 × 192	1	100
2D T2-W FSE (pre and post ablation)	7300	68	12	15.63	11	4	256 × 192	3	400
Perfusion (post ablation)	3.7	1.5	NA	62.5	9	5	96 × 96	1	120
2D T1-W FSE (pre and post ablation1)	985	7.2	6	31.25	120	5	192 × 192	1	16
3D LAVA (pre and post ablation1)	3.9	1.5	NA	62.5	15	5	192 × 192	3	240

¹Both 2-dimensional T1-weighted fast spin echo and 3-dimentional LAVA images. TR: Repetition time; TE: Echo time; ETL: Echo train length; rBW: Receiver bandwidth; NEX: Number of excitation per step; LAVA: Liver acquisitions with volume acquisition.

Table 2 Regional, core body temperatures, heart rate and oxygen tension monitored during each sonication

Energy dose (Joules)	Temp (max) (°C)	Temp (avg) (°C)	Core body temp (°C)	HR (bpm)	O2-saturation (%)
Single 3000	57 ± 3	56 ± 3	38.3 ± 0.6	89 ± 5	99 ± 1
Double 3000	61 ± 4	59 ± 4	38.1 ± 0.5	87 ± 4	99 ± 1
Single 4400	63 ± 6	61 ± 6	38.4 ± 0.4	86 ± 5	99 ± 1
Double 4400	63 ± 4	62 ± 5	38.5 ± 0.3	88 ± 4	99 ± 1

bpm: Beat/min. O₂: Oxygen; HR: Heart rate; Temp: Temperature.

Table 3 Lesions dimensions and volumes using single and double overlapping rectangular focal sonication

Energy dose (Joules)	CC (mm)	Transverse (mm)	AP (mm)	MRI volume (mm3)	Postmortem volume (mm3)
Single 3000	7.3 ± 0.07	7.8 ± 1.0	5.6 ± 0.1	317 ± 54	380 ± 111
Double 3000	7.9 ± 1.1	11.4 ± 1.6	7.5 ± 0.7	675 ± 41ac	587 ± 28a
Single 4400	7.5 ± 0.7	7.8 ± 1.6	5.6 ± 0.7	354 ± 143	517 ± 52
Double 4400	11.4 ± 1.7	12.8 ± 3.0	10 ± 1.4	1450 ± 458aeh	1280 ± 238aeh

^aP < 0.05 2 × 3000J overlapping sonication vs single 3000J sonication;

^cP < 0.05 2 × 3000J overlapping sonication vs single 4400J sonication;

^eP < 0.05 2 × 4000J sonication vs single 3000J sonication; and

^hP < 0.01 2 × 4000J overlapping sonication vs 2 × 3000J overlapping sonication. CC: Cranial-caudal; AP: Anterio-posterior; MRI: Magnetic resonance imaging.