Detection of liver metastases by pulse inversion harmonic imaging during Levovist late phase: comparison with conventional ultrasound and helical CT in 160 patients

Abstract

The aim of this study was to evaluate capabilities of pulse inversion harmonic imaging (PIHI) with Levovist in detection of liver metastases compared with conventional ultrasound (US) and helical CT (HCT). One hundred sixty consecutive patients with known malignancies were evaluated by conventional US, PIHI 2 min (40 patients) or 4 min (120 patients) after Levovist injection and HCT. Conspicuity and number of the identified metastatic lesions were evaluated and assessed by statistical analysis (significance p<0.05). Mean diameter of the smallest identified metastases was computed for conventional US, PIHI and HCT. In cases where PIHI revealed more lesions suspicious for metastases than HCT, intraopertive US with surgical biopsy or 3-6month US follow-up were performed to confirm diagnosis. Images were stored on magneto-optical disk and evaluated off-line by a dedicated software. Metastases conspicuity was significantly improved on PIHI if compared with conventional US (p<0.05). In 49 patients all the employed imaging techniques did not reveal any lesion, whereas in the re-maining 111 patients, 28 patients revealed more than five metastatic lesions and 83 patients presented from one to five metastatic lesions. In comparison with conventional US, PIHI revealed more metastases in 39/83 (47%), the same number in 44/83 (53%) and a lower number in 0/83 (0%) patients. In comparison with HCT, PIHI revealed more metastases in 10/83 (12%), the same number in 61/83 (74%) and a lower number in 12/83 (14%) patients. Average number ± SD (standard deviation) of confirmed metastases for patients was 2.21±1.6 for conventional US, 3.1±2.44 for PIHI and 3.05±2.41 for HCT. The difference between PIHI and conventional US was statistically significant (p<0.0001), whereas the difference between PIHI and HCT was not significant (p=0.9). The smallest identified metastases presented 3-mm mean diameter on PIHI, 5-mm on HCT and 7-mm on conventional US. PIHI with Levovist is a reliable technique in metastases detection.

The Role of Late-Phase Pulse Inversion Harmonic Imaging in the Detection of Occult Hepatic Metastases

“…Findings in previous studies documented that both subjective and objective conspicuities of liver malignancies are increased in late-phase PIHI compared with fundamental sonography. 3,6,7,13 Similarly, in our study we reported new lesions on late-phase PIHI in 4 patients (12.5%). In 3 of them, new lesions detected with PIHI were barely seen on a retrospective evaluation of fundamental sonography.…”

“…This finding is notable given the importance of accurate staging of patients with malignant disorders for selection of appropriate treatment strategies. Previous studies have also revealed improved conspicuity of lesions with contrast-enhanced PIHI compared with conventional sonography in patients with malignancies [3][4][5][6][7][8] ; however, those examinations were performed in patients with known or suspected liver metastasis. Unique to our study was the detection of lesions that were undetectable on routine conventional abdominal sonography.…”

“…In the patient with equivocal CT findings, the lesion was located at the most superior part of segment 2, and liver-specific contrast-enhanced (Mn-DPDP) MRI with multiplanar sections confirmed the presence of the lesion revealed by late-phase PIHI. Although we could not confirm, in previous reports it has been noted that in some cases, latephase PIHI detected more lesions than spiral CT. 3,6,7,13 Esteban et al 6 reported a higher sensitivity of postcontrast PIHI over a CT examination for the detection of liver metastases. If this finding is confirmed in larger trials, PIHI may influence or perhaps change imaging protocols for tumor staging.…”

“…When the size of the lesions was analyzed, late-phase PIHI was able to detect smaller lesions in comparison with both fundamental sonography and spiral CT, as reported previously. 3,[5][6][7]13 Yücel et al 13 documented that lesions as small as 3 mm could be detected with late-phase PIHI. In our study, with the exclusion of the patient with multiple metastases, the mean size of the lesions revealed on late-phase PIHI was 12 mm, not different from that of spiral CT (Table 1).…”

“…In the past few years, the use of microbubble contrast agents and the development of contrastspecific techniques have greatly improved the ability of sonography to detect liver metastases. [3][4][5][6][7][8] These techniques generate images based on the nonlinear and transient acoustic effects of microbubble contrast agents. They offer high sensitivity to microbubble movement or destruction.…”