MR-guided microwave ablation in hepatic malignancies: clinical experiences from 50 procedures

Figures & data

Table 1. Summary of acquisition parameters for planning, targeting, monitoring and controlling.

Sequence	TR (ms)	TE (ms)	Matrix (pixel)	Slice thickness (mm)	Flip angel (°)	Bandwidth (HZ/pixel)
Planning
T2 HASTE	1100	116	256 × 205	6	120	488
T1 VIBE	3.6	1.3	256 × 140	2	10	454
T2 TSE	7500	101	320 × 186	6	150	300
Planning optional
CE-dynamic T1 VIBE	3.6	1.3	256 × 140	2	10	454
Diffusion-weighted imaging	5020	82	128 × 100	5	90	1776
Targeting
BEAT_IRTT (SSFP)	425	1.98	192 × 192	8	15	420
Monitoring
T1 VIBE	3.6	1.3	256 × 140	2	10	454
T2 TrueFISP	4.4	2.2	256 × 256	6	75	500
Control
T2 HASTE	1100	116	256 × 205	6	120	488
T2 TSE	7500	101	320 × 186	6	150	300
CE-dynamic T1 VIBE	3.6	1.3	256 × 140	2	10	454

HASTE: half acquisition single shot turbo spin echo; VIBE: volume interpolated breath-hold examination; TSE: turbo spin echo; CE: contrast-enhanced; BEAT_IRTT: steady-state free precession; TrueFIST: true fast imaging with steady state precession.

Figure 1. 79-years-old male patient treated for a singular hepatic metastasis of a melanoma. Unenhanced T1-weighted planning imaging (a) depicts the target tumor in segment V (arrow) measuring 18 mm. Contrast-enhanced control imaging in the portal-venous phase shows the ablation zone with the contour of the treated tumor (b). Die smallest safety margin was measured with 5 mm at the lateral portion of the ablation zone (arrow).

Table 2. Baseline patient characteristics and ablation procedure related parameters.

Variables	N/mean ± SD/median (range)
Patients	47
Procedures (n = 42 1 lesion; n = 8 2 lesions)	50
Lesions	58
Gender (m)	39
Age (years)	60.5 ± 12.2
Diagnosis
HCC	17
Colorectal	18
-Rectum	9
-Colon	7
-Sigma	2
Melanoma	6
Uveal melanoma	2
Ovarian cancer	1
Kidney cancer	1
Breast cancer	1
Liver sarcoma	1
Mixed adenoneuroendocrine carcinoma	1
Myofibroblastic inflammatory cancer	1
Cancer of unknown primary	1

Figure 2. Images of a 56-year-old male patient with metastasis of a mixed adenoneuroendocrine carcinoma in segment VIII. Metastasis is clearly depictable in planning imaging without administration of intravenous contrast agent (a; arrows). During first targeting with MR fluoroscopy (b) the applicator was positioned toward the cranial part of the metastasis (arrow). After ablation for 10 min with 18 kJ there is no coagulated tissue visible on the caudal part in monitoring (c; circle). Therefore, the applicator was repositioned (d) for an additional ablation for 15 min with 27 kJ toward the caudal part of the metastasis (e; circle). On final postprocedural imaging (f) there is a well-defined, T1-weighted hyterintense, oval shaped ablation zone with a 4 mm safety margin. No local recurrence was observed during follow-up.

Table 3. Ablation procedure related parameters.

Variables	N/mean ± SD/median (range)
Tumor size all (cm)	1.6 ± 0.7
Tumor size local recurrence (cm)	2.7 ± 1.1
Contrast agent prior procedure	13 (Primovist)
Hospital admission after procedure	1 (1–19)
Short axis ablation zone (mm)	28.8 ± 8.2
Long axis ablation zone (mm)	52.6 ± 13.0
Spherical index	0.54 ± 0.12
Safety margin (mm)	4.5 ± 2.5
Ablation time (min)	26.7 ± 13.1
Procedure time (min)	211.2 ± 68.7
Applicator positions	2.6 (1–6)
Energy (kJ)	43.2 ± 23.5

Table 4. Summary of complications according to the SIR reporting system.

SIR classification for complications
Grade	n
Minor complications
A	3
B	7
Major complications
C	1
D	2
E	–
F	–

Figure 3. Images of a 77-year-old female with metastasis of a melanoma. Planning imaging (a) depicts the small metastasis (17 mm) in segment VII (arrow). Post-procedural imaging (b) depicts an ablation zone with an almost non-visible safety margin dorso-medial (arrow). After 40 months local recurrence (arrow) was diagnosed on routine contrast-enhanced follow-up imaging (c) dorsal to the shrunken ablation zone (dash arrow).

Figure 4. Kaplan–Meier survival estimates for overall survival, local recurrence–free survival and non-target recurrence-free survival.