Hepatic Metastases: Catching What’s Hard To Catch
A new approach on inversion recovery imaging may improve the staging of patients with suspected liver metastasis. Patients with previous liver disease particularly benefit from the method.
“T1 weighted VIBE fat-sat twenty minutes after administering gadoxetate disodium is the standard sequence for liver imaging,“ said Ute Fahlenkamp, Charité Berlin, Germany. However, the differentiation between tumor and liver parenchyma may still be difficult in some cases. Especially small tumors may be hard to detect.
Inversion recovery (IR) serves as a well-known alternative in these cases: the usually used magnitude reconstruction IR relies on increasing the signal ratio between tissue with and without signal enhancement. “However, you would have to create an inversion time for every single tumor,” noted Fahlenkamp.
To overcome this problem, she transferred phase sensitive reconstruction (PSIR), a technique known from cardiac imaging, to liver MRI. She and her team prospectively compared a contrast-optimized PSIR technique for the detection of hepatic metastases to the standard T1 gradient-echo (GE) VIBE sequence. The team enrolled 31 patients, 28 with known liver metastases or a primary tumor known for hepatic spread, three which unequivocal hepatic findings in previous examinations. All scans were performed with 10mL of gadoxetate-disodium (Primovist®) at standard dose. The scans were done on a 1.5T scanner.
Fahlenkamp then qualitatively evaluated lesion delineation. A quantitative evaluation of the lesion-to-liver contrast ratio on VIBE and magnitude-reconstructed IR was also performed. In addition, the images were analyzed for the number of lesions.
Qualitative analysis showed a better delineation of lesions with PSIR for all lesions sizes.
It was especially pronounced for lesions of less than 0.5cm. PSIR was also able to detect more of these very small lesions than the standard VIBE sequence. Numbers were similar for all lesions larger than 0.5cm.
“PSIR has potential merit for an improved staging of patients with suspected liver metastases,” concluded Fahlenkamp. It improves the imaging characteristics of hepatic metastases and may increase the detection of small lesions.
“The very small lesions we did not see initially were all confirmed on T2,” noted Fahlenkamp during the discussion. DWI was not performed in the study.
“Will these sequences also work better on patients after chemotherapy with their usually heterogeneous liver tissue?” asked on audience member. Fahlenkamp answered that PSIR was especially helpful in patients with prior chemotherapy or cholestatic disease. “PSIR is not as helpful in otherwise healthy liver parenchyma,” she added.
Pathological correlations were not performed in the study, as liver resection was no option in any of the patients.