Do different types of liver lesions differ in their uptake of the microbubble contrast agent SH U 508A in the late liver phase? Early experience

US characterization of focal hepatic lesions with intermittent high-acoustic-power mode and contrast material

RATIONALE AND OBJECTIVES

This study was performed to determine whether ultrasound (US) performed with SonoVue, a contrast agent that contains microbubbles filled with sulfur hexafluoride vapor, depicts differential patterns of contrast enhancement in focal hepatic lesions.

MATERIALS AND METHODS

Forty focal hepatic lesions (15 hepatocellular carcinomas [HCCs], 10 metastases, 11 hemangiomas, and four focal nodular hyperplasias) in 39 patients were evaluated by means of US, color Doppler US, and contrast-enhanced US performed by using intermittent high-acoustic-power mode. Contrast-enhanced helical computed tomography (11 patients) and US-guided fine needle aspiration (28 patients) were used as reference procedures. Contrast enhancement patterns were defined by means of both subjective and objective analysis, and baseline and contrast-enhanced US scans were reviewed offline.

RESULTS

Thirteen of 15 HCCs, eight of 10 metastases, and all four hemangiomas with an atypical pattern at baseline US were correctly characterized after SonoVue injection. Two of 15 HCCs and two of 10 metastases remained indeterminate, with no characteristic baseline or contrast-enhanced patterns identified. Baseline US was essential in characterizing all hemangiomas with a typical pattern (n = 7), and color Doppler US with spectral analysis of tumoral vessels was essential in characterizing focal nodular hyperplasia. The percentage of diagnostic agreement with reference procedures was significantly increased (P < .001) for contrast-enhanced US compared with baseline US.

CONCLUSION

Characteristic patterns of US contrast enhancement with SonoVue help in characterizing and differentiating focal hepatic lesions.

Improved detection of hepatic metastases with pulse-inversion US during the liver-specific phase of SHU 508A: multicenter study

PURPOSE

To compare conventional B-mode ultrasonography (US) alone with the combination of conventional B-mode US and contrast material-enhanced (SHU 508A) late-phase pulse-inversion US for the detection of hepatic metastases by using dual-phase spiral computed tomography (CT) as the standard of reference.

MATERIALS AND METHODS

One hundred twenty-three patients underwent conventional US, US in the liver-specific phase of SHU 508A, and single-section spiral CT. US and CT images were assessed by blinded readers. Differences in sensitivity, specificity, and the number and smallest size of metastases at conventional and contrast-enhanced US were compared by using CT as the standard of reference. Lesion conspicuity was assessed objectively (quantitatively) and subjectively by one reader before and after contrast material administration.

RESULTS

In 45 of 80 (56%) patients with metastases, more metastases were seen at contrast-enhanced US than at conventional US. In three of these patients, conventional US images appeared normal. The addition of contrast-enhanced US improved sensitivity for the detection of individual metastases from 71% to 87% (P <.001). On a patient basis, sensitivity improved from 94% to 98% (P =.44), and specificity improved from 60% to 88% (P <.01). Contrast enhancement improved the subjective conspicuity of metastases in 66 of 75 (88%) patients and the objective contrast by a mean of 10.8 dB (P <.001). Contrast-enhanced US showed more metastases than did CT in seven patients, and CT showed more than did contrast-enhanced US in one of 22 patients in whom an independent reference (magnetic resonance imaging, intraoperative US, or pathologic findings) was available.

CONCLUSION

Contrast-enhanced US improved sensitivity and specificity in the detection of hepatic metastases.

Pulse-inversion harmonic imaging improves lesion conspicuity during US-guided biopsy

PURPOSE

To assess the feasibility of percutaneous biopsy of low-conspicuity focal liver lesions with use of pulse-inversion harmonic imaging (PIHI) guidance in the late phase after injection of microbubble contrast agent.

MATERIALS AND METHODS

Twelve patients referred for ultrasound (US)-guided biopsy had liver lesions lacking adequate conspicuity to undergo biopsy under conventional ultrasound (US) guidance. They underwent biopsy procedures performed with the use of PIHI guidance in the late phase after injection of Levovist. The conspicuity of lesions, procedure time, number of passes, and success and complication rates were documented and compared to a control group. The control group consisted of retrospective analysis of 19 patients who had undergone conventional US-guided biopsy procedures performed by the same radiologist.

RESULTS

After contrast material injection, all lesions had sufficient increases in conspicuity to be targeted under PIHI guidance. Procedure time was prolonged in the PIHI group (66 minutes; range, 30-120 min; vs control, 33 min; range, 15-77 min; P <.01, Wilcoxon signed-rank test). The number of passes was greater in the PIHI group (1.9 +/- 0.3; vs control, 1.4 +/- 0.6; P <.01, chi(2) test). No statistically significant difference was observed when comparing success and complication rates.

CONCLUSION

PIHI in the late phase after injection of Levovist generated clear delineation of focal liver lesions in all cases, allowing an accurate and safe sampling. This technique broadens the scope of US-guided biopsy to lesions lacking adequate conspicuity on conventional US.

Functional ultrasound methods in oncological imaging

The real time nature of ultrasound and functional methods such as Doppler ultrasound mean that ultrasound can claim to have always been a functional imaging method, but recent developments in quantitation, dramatic improvement in Doppler performance and now microbubbles have created many exciting new applications. These include methods for assessing the neovascularity of tumours, for following the effects of therapy and for predicting the likelihood of development of metastatic disease at the staging of primary tumours.

Hepatocellular adenoma: diagnostic difficulties and novel imaging techniques

We report the case of a 30-year-old eastern European female who presented with right upper quadrant pain. Clinical examination was unremarkable and liver function tests were normal. CT identified a 5 cm lesion in segment V of the liver, which was of homogeneous low density with no calcification or significant enhancement. MRI showed the lesion to be hypointense to liver on T(1) weighted sequences and isointense on T(2) weighted sequences. Rapid arterial enhancement with gadolinium-DTPA faded without leaving a definite central scar. Ultrasound showed the lesion to be echogenic with minimal vascularity. Administration of a liver-specific microbubble contrast agent showed low uptake relative to the surrounding liver. Phosphorus-31 MR spectroscopy, localized to the lesion itself, revealed a markedly increased phosphomonoester resonance with a decreased phosphodiester resonance, compatible with increased cell turnover. Biopsy confirmed the lesion to be a hepatocellular adenoma. The diagnosis of a hepatic adenoma is difficult with tissue diagnosis the gold standard, but it may be suggested by a combination of imaging modalities. We have described two new imaging techniques not previously described in characterization of hepatic adenomata, namely ultrasound with contrast agent and MR spectroscopy.

Advances in ultrasound

Ultrasound (US) has undergone dramatic changes since its inception three decades ago; the original cumbersome B-mode gantry system has evolved into a high resolution real-time imaging system. This review describes both recent advances in ultrasound and contrast media and likely future developments. Technological advances in electronics and computing have revolutionized ultrasound practice with ever expanding applications. Developments in transducer materials and array designs have resulted in greater bandwidths with improvements in spatial and contrast resolution. Developments in digital signal processing have produced innovations in beam forming, image display and archiving. Technological advances have resulted in novel imaging modes which exploit the non-linear behaviour of tissue and microbubble contrast agents. Microbubble contrast agents have dramatically extended the clinical and research applications of ultrasound. Not only can Doppler studies be enhanced but also novel non-linear modes allow vessels down to the level of the microcirculation to be imaged. Functional and quantitative studies allow interrogation of a wide spectrum of tissue beds. The advent of tissue-specific agents promises to improve the sensitivity and specificity of ultrasound in the detection and characterization of focal liver lesions to rival that of computed tomography (CT) and magnetic resonance imaging (MRI). Ultrasound has recently moved into therapeutic applications with high intensity focused ultrasound (HIFU) and microbubble assisted delivery of drugs and genes showing great promise.

Phase-inversion sonography during the liver-specific late phase of contrast enhancement: improved detection of liver metastases

OBJECTIVE

The purpose of our study was to assess whether phase-inversion sonography during the late, liver-specific phase of contrast enhancement using Levovist improves the detection of hepatic metastases relative to unenhanced conventional B-mode sonography.

SUBJECTS AND METHODS

Sixty-two patients were studied with unenhanced B-mode sonography and phase-inversion sonography 2.5 min after the injection of Levovist. All patients underwent one reference examination (CT, MR imaging, or intraoperative sonography). The conspicuity, number, size, and distribution of metastases before and after contrast administration as judged by a sonographer (who was unaware of other imaging findings) were compared with each other and with reference imaging.

RESULTS

The conspicuity of metastases was improved by contrast-enhanced phase inversion in 94% of patients. Thirty-nine patients showed metastases on reference imaging; 36 of these were positive on baseline sonography and 38 on phase-inversion sonography. Phase-inversion sonography showed more reference imaging-confirmed metastases than baseline sonography in 28 patients (45%). The average number of confirmed metastases per patient was 3.06 for baseline sonography and 5.42 for contrast-enhanced phase-inversion sonography (p < 0.01). The average sensitivity for detecting individual metastases improved from 63% to 91%. Metastases of less than 1 cm were shown in 14 patients on baseline sonography, in 24 patients on phase-inversion sonography, and in 26 on reference imaging. Both sonographic techniques showed false-positive lesions in six patients.

CONCLUSION

Contrast-enhanced phase-inversion sonography in the liver-specific phase of contrast enhancement using Levovist provides a marked improvement in the detection of hepatic metastases relative to unenhanced conventional sonography, without loss of specificity. Phase-inversion sonography was particularly advantageous in detecting small metastases and may be a competitive alternative to CT and MR imaging.