Date Published: March 6, 2019
Publisher: Public Library of Science
Author(s): Ute Lina Fahlenkamp, Günther Engel, Lisa Christine Adams, Sarah Maria Böker, Minh Huynh Anh, Moritz Wagner, Bernd Hamm, Marcus Richard Makowski, Pascal A. T. Baltzer.
Detection of metastases can have a significant impact on therapy. Nevertheless, even in gadoxetate disodium-enhanced MR scans, very small hepatic metastases may be difficult to see.
To investigate the potential of a contrast-optimised (phase-sensitive) inversion recovery MR sequence in gadoxetate disodium-enhanced scans for detection of hepatic metastases.
With institutional review board approval and after written informed consent, 40 patients (18 male, 22 female) with suspected or known hepatic metastases were examined on a 1.5 T MR system. A T1-weighted gradient-echo volumetric-interpolated-breath-hold (VIBE) sequence was acquired as part of the standard imaging protocol 20 minutes after administration of gadoxetate disodium. Additionally, an IR sequence was acquired with an inversion time to suppress native signal from metastases. Overall image quality and delineation of lesions were assessed on VIBE as well as on magnitude-reconstructed (MAG) and phase-sensitive IR (PSIR) sequences. Lesion-to-liver contrast (LLC) was compared between VIBE and MAG images.
Overall image quality was high in both VIBE and MAG IR sequences (VIBE 4.275; MAG 4.313), yet significantly lower in PSIR (4.038). Subjective delineation of lesions was higher on MAG and PSIR images compared to VIBE in all size groups with an overall statistically significant difference for VIBE vs. MAG vs. PSIR (p < .001) in the variance analysis. Mean LLC was 0.35±0.01 for VIBE sequences, and 0.73±0.01 for MAG. Contrast-optimised PSIR seems to improve imaging characteristics of hepatic metastases in gadoxetate disodium-enhanced scans compared to T1 gradient-echo VIBE sequences.
Due to its rich blood supply, the liver is one of the organs most frequently affected by metastatic disease. Reliable detection of metastatic disease is of high importance, as tumour treatment may be significantly different depending on absence or presence of metastases. Since its approval in Europe and Asia in 2005 and in the United States in 2008, gadoxetate disodium (Gd-EOB-DTPA) has become well established in hepatobiliary imaging due to its property to be taken up by hepatocytes as they express an organic anion transporting peptide. Lesions without the organic anion transporting peptide do not accumulate gadoxetate disodium and therefore appear hypointense in the hepatobiliary phase compared to the enhancing normal liver parenchyma, improving detection rates of liver metastases [1–3].
The contrast-optimised PSIR sequence enabled imaging with a significantly increased contrast between liver metastases and liver parenchyma. Thereby, a higher diagnostic confidence and a higher detection rate of small metastases could be achieved compared to standard VIBE sequences. This is of high clinical importance as most cancer treatment regimens depend on whether the primary tumor is associated with distant metastases [13–15]. Additionally, patients with known hepatic metastases might benefit from a more accurate assessment of tumor burden within the liver, as preoperative imaging is the key in determining the surgical candidacy and approach . Additionally, as metastases in liver parenchyma altered by chemotherapeutic agents can be more difficult to detect, PSIR may offer an improved follow up.
In conclusion, contrast-optimised PSIR improves imaging characteristics of hepatic metastases and may increase detection of small lesions in gadoxetate disodium-enhanced scans compared to T1 gradient-echo VIBE sequences.