Diagnostic performance of abbreviated gadoxetic acid-enhanced magnetic resonance protocols with contrast-enhanced computed tomography for detection of colorectal liver metastases

Table 1 Magnetic resonance imaging acquisition parameters

Sequence	Orientation	Respiratory compensation	Repetition/echo time (ms)	Flip angle (degrees)	Section thickness (mm)	Intersection gap (mm)	Field-of-view (mm2)	Matrix	Acquisition time (s)
T1-weighted in and opposed phases (SPGR)	Axial	Breath-hold	6.9/4.5	12	4	1	350´280	320´224	20
Dynamic study (LAVA)1	Axial	Breath-hold	6.5/3.1	15	4	1	350´280	320´192	20
Single-shot FSE T2-weighted imaging	Axial	Breath-hold	520/82	90	5	1	350´350	384´256	20
Diffusion-weighted imaging	Axial	Respiration trigger	8000-12000/68	90	5	1	350´350	128´128	210
Fat-suppressed FSE T2-weighted imaging	Axial	Respiration trigger	520/82	160	5	1	350´350	320´320	230
Hepatobiliary phase	Axial	Breath-hold	6.5/3.1	30	4	1	350´280	320´224	20

¹Dynamic study consists of pre-contrast, late arterial, portal venous, and transitional phases.

SPGR: Spoiled gradient-recalled echo; LAVA: Liver acquisition with volume acceleration; FSE: Fast spin echo.

Table 2 Patient and tumor characteristics

Characteristics
Number of cases	87
Gender (male/female)	51 (58.6%)/36 (41.4%)
Age (yr)1 overall	67.2 ± 10.8
Male	67.5 ± 9.6
Female	66.8 ± 12.4
Location of colorectal cancer colon/rectum	31/56
Total number of lesions; metastases/benign	370
Metastases	195 (51.4%)
Benign lesions	175 (49.6%) (15 hemangiomas/160 cysts)
Number of lesions per patient with liver metastases	2.2 (1-8)
Size of metastatic lesion (mm)1	28.2 ± 13.6
Number of benign lesions per patient	3.1 (0-12)
Size of benign lesions (mm)1	4.8 ± 2.8

¹Data are expressed as means ± SD. Other data represent numbers of lesions and range.

Table 3 Comparison of diagnostic performance of three reading sessions including abbreviated magnetic resonance imaging protocol 1

	Reader 1						Reader 2
	Ab-MRI	Standard MRI	Ab-MRI + CE-CT	P value (Ab-MRI vs standard)	P value (Ab-MRI vs Ab-MRI + CE-CT)	P value (standard vs Ab-MRI + CE-CT)	Ab-MRI	Standard MRI	Ab-MRI + CE-CT	P value (Ab-MRI vs standard)	P value (Ab-MRI vs Ab-MRI + CE-CT)	P value (standard vs Ab-MRI + CE-CT)
Sensitivity	93.3 (88.9-96.4)	94.4 (92.3-95.1)	93.8 (91.8-94.6)	0.5	> 0.99	> 0.99	91.3 (88.9-92.5)	93.8 (91.7-94.8)	93.3 (91.1-94.3)	0.063	0.125	> 0.99
Specificity	97.1 (93.5-99.1)	98.9 (96.6-99.7)	98.9 (96.6-99.7)	0.125	0.25	> 0.99	97.7 (95.0-99.1)	98.3 (95.8-99.4)	98.3 (95.8-99.4)	> 0.99	> 0.99	> 0.99
PPV	97.3 (93.9-99.1)	98.9 (96.8-99.7)	98.9 (96.8-99.7)	0.25	0.25	> 0.99	97.8 (95.2-99.1)	98.4 (96.1-99.4)	98.4 (96.0-99.4)	0.25	0.25	> 0.99
NPV	92.9 (88.2-96.2)	94 (91.9-94.8)	93.5 (91.4-94.3)	0.5	> 0.99	> 0.99	91 (85.9-94.6)	93.5 (91.2-94.5)	93 (90.6-94.0)	0.063	0.125	> 0.99
Accuracy	95.1 (92.4-97.1)	96.5 (94.4-97.3)	96.2 (94.1-97.0)	0.063	0.125	> 0.99	94.3 (91.8-95.6)	95.9 (93.6-97.0)	95.7 (93.3-96.7)	0.031	0.063	> 0.99
AUROC	0.952 (0.931-0.974)	0.966 (0.948-0.984)	0.964 (0.945-0.982)	0.025	0.045	0.317	0.945 (0.922-0.968)	0.961 (0.941-0.980)	0.958 (0.938-0.978)	0.014	0.025	0.317

Abbreviated magnetic resonance imaging protocol 2 consisting of fat-suppressed fast spin echo T2-weighted, diffusion-weighted, and hepatobiliary phase images. Numbers in square brackets represent 95%CIs. PPV: Positive predictive value; NPV: Negative predictive value; AUROC: Area under the receiver operating characteristic curve; Ab-MRI: Abbreviated magnetic resonance imaging; CE-CT: Contrast-enhanced computed tomography.

Table 4 Comparison of diagnostic performance of three reading sessions including abbreviated magnetic resonance imaging protocol 2

	Reader 3						Reader 4
	Ab-MRI	Standard MRI	Ab-MRI + CE-CT	P value (Ab-MRI vs standard)	P value (Ab-MRI vs Ab-MRI + CE-CT)	P value (standard vs Ab-MRI + CE-CT)	Ab-MRI	Standard MRI	Ab-MRI + CE-CT	P value (Ab-MRI vs standard)	P value (Ab-MRI vs Ab-MRI + CE-CT)	P value (standard vs Ab-MRI + CE-CT)
Sensitivity	93.3 (90.7-95.0)	94.9 (92.7-95.9)	95.9 (93.8-96.9)	0.25	0.063	0.5	94.4 (90.1- 97.2)	95.9 (93.8-96.9)	96.9 (95.1-97.6)	0.25	0.063	0.5
Specificity	96 (93.1-97.8)	98.3 (95.9-99.4)	98.3 (96.0-99.4)	0.125	0.125	> 0.99	97.7 (94.3-99.4)	98.3 (96.0-99.4)	98.9 (96.8-99.7)	> 0.99	0.5	> 0.99
PPV	96.3 (93.6-98.0)	98.4 (96.2-99.4)	98.4 (96.3-99.4)	0.125	0.125	> 0.99	97.9 (94.6-99.4)	98.4 (96.3-99.4)	99 (97.1-99.7)	> 0.99	0.5	> 0.99
NPV	92.8 (90.0-94.6)	94.5 (92.2-95.6)	95.6 (93.3-96.6)	0.5	0.125	0.5	94 (89.4-96.9)	95.6 (93.3-96.6)	96.7 (94.7-97.5)	0.25	0.063	0.5
Accuracy	94.6 (91.9-96.3)	96.5 (94.2-97.5)	97 (94.9-98.0)	0.016	0.004	0.5	95.9 (93.4-97.7)	97 (94.9-98.0)	97.8 (95.9-98.6)	0.125	0.063	0.5
AUROC	0.947 (0.924-0.969)	0.943 (0.919-0.967)	0.948 (0.925-0.971)	0.603	0.862	0.156	0.960 (0.941-0.980)	0.971 (0.954-0.988)	0.979 (0.964-0.993)	0.045	0.007	0.083

Abbreviated magnetic resonance imaging protocol 2 consisting of fat-suppressed fast spin echo T2-weighted, diffusion-weighted, and hepatobiliary phase images. Numbers in square brackets represent 95%CIs. PPV: Positive predictive value; NPV: Negative predictive value; AUROC: Area under the receiver operating characteristic curve; Ab-MRI: Abbreviated magnetic resonance imaging; CE-CT: Contrast-enhanced computed tomography.