Diagnostic performance of dual-energy CT in nonspecific terminal ileitis

To investigate the value of dual-energy CT (DECT) imaging in the diagnosis of nonspecific terminal ileitis (NTI).

This is a retrospective study, enrolling patients with symptomatic terminal ileitis that underwent conventional multidetector CT (MDCT) enterography or DECT enterography. The sensitivity of the diagnosis of NTI between MDCT images and different kinds of DECT images (40-70 kev virtual monoenergetic images (VMIs) and iodine density images) was compared. The iodine concentrations of lesion bowel wall among NTI, Crohn's disease (CD) and intestinal tuberculosis (ITB) in DECT group and the value of lesion-to-non-lesion contrast ratios of all patients were measured. Receiver operator characteristic (ROC) curves for normalized iodine concentration (NIC) for differentiating among the three kinds of disease were drawn.

The sensitivity for the diagnosis of NTI in DECT group (including 40 kev, 50 keV VMIs, and iodine density images) were all 89.7%, significantly higher than that in MDCT group (65.1%) (P = 0.026). Statistical analysis did not reveal marked differences between 60 kev, 70 kev VMIs (86.2%) and MDCT images (65.1%) (P = 0.059). The NIC of NTI was (0.15 ± 0.04)100 µg/cm³ and (0.45 ± 0.08)100 µg/cm³, significantly lower than that of CD (0.34 ± 0.09) 100 µg/cm³, (0.85 ± 0.06) 100 µg/cm³ and that of ITB (0.29 ± 0.07) 100 µg/cm³, (0.88 ± 0.07) 100 µg/cm³ at the enteric phase (EP) and portal venous phase (PVP) (P < 0.001, wholly). The area under the ROC curves (AUROCs) of NICEP and NICPVP were 0.910 and 0.980, respectively, for differentiating between NTI and CD. The value of lesion-to-non-lesion contrast ratios is maximum on the 40 keV VMI both EP and PVP. The value of lesion-to-non-lesion contrast ratios of NTI was lower than that of CD and ITB on each image. The AUROCs of NICEP and NICPVP were 0.875 and 0.940, respectively, for differentiating between NTI and ITB.

DECT has higher sensitivity in the diagnosis of NTI than MDCT. Low-keV VMI and iodine density images of DECT can clearly show the NTI. DECT imaging can help to differentiate NTI from CD or ITB by comparing the NIC.