Evaluation of tissue shrinkage after CT-guided microwave ablation in patients with liver malignancies using Jacobian determinant

Figures & data

Figure 1. Flow-chart of patient inclusion process.

Table 1. Demographic data of patients included for further evaluation of tissue shrinkage after CT-guided MWA.

Patient characteristics	Number
Number of included patients	24
Sex (number of males/females)	14/10
Age (years)	61 (34 − 79)
BMI (kg/m^2)	26 (23 − 27)
Cirrhosis (number) yes/no	18/6
Prior chemotherapy (number) yes / no	15/9
Tumor characteristics
Subcapsular (number) yes/no	10/14
Tumor volume >/<6 ml	13/11
Primary tumor	19
Metastases	5
Localization (number)
Right lobe (S5–8)	14
Left lobe (S1–4)	10

Figure 2. Schematic description of the postprocessing steps for evaluation of tissue shrinkage. 1: Export of pre- and post-interventional CT images. 2: Semi-automatic whole liver (yellow color-coded) and tumor (blue color-coded) segmentation. 3: Image registration. 4: Application of a postprocessing algorithm to quantify voxel wise the deformation volume of the liver tissue. 5: Calculation of JD maps in three defined anatomic regions (green zone = ablated tumor; red zone = 5cm tumor perimeter; blue zone = whole liver). 6: Evaluation of tissue shrinkage considering different patient and tumor settings.

Figure 3. Exemplary registration analysis. A 43-year-old female patient with a subcapsular located metastasis of a neuroendocrine cervix carcinoma is shown (blue arrow). The bifurcation of the portal vein was defined as landmark and marked in the pre-interventional (A), in the registered (B) and in the post-interventional CT dataset (C) (red cross). The landmark distance between pre- and post-interventional CT images was 10.3 mm and, as expected, the landmark distance between pre- and registered post-interventional CT image decreased, in this patient up to 2.0 mm.

Table 2. Results of different patient´s preconditions.

Preconditions		Patients (n = 24)	Number of males/females		Liver volume (ml)		Tumor volume (ml)
Subcapsular tumor	Yes	10	4/6	p = 0.1^a	2699.3 (1999.8–3087.4)	p = 0.6^b	9.8 (6.5–31.9)	p = 0.1^b
	No	14	10/4		2366.5 (2060.7–2822.1)		4.4 (2.1–8.3)
Tumor volume >6 ml	Yes	13	6/7	p = 0.1^a	2803.27 (2215.1–3135.9)	p = 0.2 ^b	10.7 (8.3–20.3)	p < 0.001^b
	No	11	8/3		2271.4 (1895.3–2742.3)		2.2 (1.5–2.9)
Cirrhosis	Yes	18	11/7	p = 0.6^a	2363.6 (1982.3–2816.3)	p = 0.8 ^b	7.9 (2.6–11.5)	p = 1.0^b
	No	6	3/3		2919.8 (2181.7–3582.2)		5.6 (2.1–12.0)
Tumor entity	Primary	19	11/8	p = 0.9^a	2455.9 (2006.2–2854.1)	p = 0.4 ^b	7.9 (2.7–11.2)	p = 0.8^b
	Secondary	5	3/2		2848.6 (2086.2–3058.5)		2.9 (1.9–11.4)
Prior chemotherapy	Yes	15	9/6	p = 0.5^a	2704.9 (2066.8–2990.9)	p = 0.2 ^b	7.7 (2.1–11.1)	p = 1.0^b
	No	9	6/3		2271.4 (1654.7–2798.2)		2.9 (1.7–11.2)

Figure 4. Exemplary results of two patients are demonstrated. (A) Pre- and post-interventional CT images of a 34-year-old female patient with a non-subcapsular located liver metastasis in segment 8 (green arrow) with 6.5 ml tumor volume with regional tissue alterations in zone 1 (green line) of −2.5 %, tissue shrinkage in zone 2 (red line) of +4.7% and similar tissue formation in the whole liver (blue line). (B) Pre- and post-interventional CT images of a 64-year-old female patient with a subcapsular liver metastases in segment 4 (green arrow) with 6.9 ml tumor volume with regional tissue alterations in zone 1 (green line) of +0.9%, +1.6 % in zone 2 (red line) and −0.1 % in the whole liver (blue line).

Figure 5. Results of volume changes for all subgroups (A–E) in the ablated tumor, 5-cm perimeter and the whole liver, respectively, are demonstrated. Hepatic tissue volume changes were compared depending on different clinically preconditions including tumor location (subcapsular vs. non-subcapsular, (A), tumor volume (6/<6 ml, B), presence of cirrhosis (yes vs. no, C), tumor entity (primary vs. secondary, D), history of chemotherapy (yes vs. no, E).

Table 3. Percental tissue volume changes post-MWA of each subgroup are shown.

Preconditions		Volume change (%)
		Ablated tumor		5 cm Perimeter		Whole liver
Subcapsular tumor	Yes	1.1. (−0.1 to 2.1)	p = 0.0195^a	4.8 (1.4 to 27.1)	p = 0.9^a	0.3 (−1.1 to 1.9)	p = 0.9 ^a
	No	−3.5 (−6,9 to 2.4)		−7.5 (−23.5 to 12.1)		0.1 (−3.2 to 3.8)
Tumor volume >6 ml	Yes	−1.7 (−3.6 to 0.96)	p = 0.1^a	1.3 (12 to 13.7)	p = 0.9^a	−1.0 (−1.5 to 1.1)	p = 0.002^a
	No	−1.9 (−3.6 to 3.2)		1.9 (−0.3 to 5.6)		2.5 (−0.2 to 5)
Cirrhosis	Yes	0.35 (−4.2 to 2.1)	p = 1.0^a	−2.3 (−19.8 to 8.3)	p = 0.2^a	−0.03 (−1.4 to 1.9)	p = 0.3^a
	No	−1.1 (−3.5 to 1.3)		10.6 (4.3 to 33.5)		2.1 (−2.5 to 6.9)
Tumor entity	Primary	0.5 (−3.9 to 2.1)	p = 0.8^a	1.3 (−17.3 to 10.2)	p = 0.1^a	−0.4 (−1.3 to 1.9)	p = 0.8^a
	Secondary	−4.1 (−3.8 to 1.5)		−34.4 (4.1 to 16.7)		−3.6 (−0.15 to 7.3)
Prior chemotherapy	Yes	0.9 (−3.2 to 2.6)	p = 0.5^a	4.2 (−2.3 to 13.1)	p = 1.0^a	−0.2 (−1.4 to 2.6)	p = 0.6^a
	No	−0.2 (−4.6 to 2.1)		−11.1 (−22.3 to 11.1)		1.9 (−0.9 to 2.3)

Table 4. Results of the post hoc power calculation [26].

Preconditions		Patients (all n = 24)	Statistically smallest detectable difference (%)
			Ablated tumor	5-cm Perimeter	Whole liver
Subcapsular tumor	Yes	10	1.7	13	2.1
	No	14	1.4	11	1.7
Tumor volume >6 ml	Yes	14	1.9	6.3	0.65
	No	10	2.3	7.7	0.8
Cirrhosis	Yes	18	2.2	11	1.3
	No	6	4.5	23	2.7
Tumor entity	Primary	19	1.8	9.3	2.1
	Secondary	5	4.4	22	5
Prior chemotherapy	Yes	15	2.2	11	1.4
	No	9	2.7	13	1.7

Statistically smallest detectable difference (%) for each subgroup was calculated.

Rosner B. Fundamentals of biostatistics. 7th ed. Boston: Brooks/Cole, Cengage Learning; 2011.

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