Contrast-enhanced Harmonic Imaging Research Articles

Improved Detection of Liver Metastases with Contrast-enhanced Wideband Harmonic Imaging: Comparison With CT Findings

Improved Detection of Liver Metastases with Contrast-enhanced Wideband Harmonic Imaging: Comparison With CT Findings

Comparison of unrestricted targeted biopsy to targeted sextant biopsy of the prostate

Objective: Recent studies have demonstrated improved detection of prostate cancer with targeted biopsy using microbubble contrast agents. We evaluated cancer detection with two different contrast-enhanced biopsy strategies: unrestricted targeted biopsy of the most suspicious areas in the outer gland, and targeted sextant biopsy of the most suspicious area within each sextant.Methods: One hundred eighteen subjects with an elevated PSA (>4 ng/ml) or abnormal digital rectal examination were evaluated by transrectal sonography during infusion of a microbubble contrast agent (Imagent: Alliance Pharmaceuticals). Up to 4 unrestricted targeted biopsy cores were directed toward the most suspicious area(s) of the outer gland during contrast-enhanced harmonic gray scale and Doppler imaging. Six additional biopsy cores were obtained in a modified sextant distribution to target the most suspicious area within each sextant. Any sextant with no suspicious area was sampled with a laterally directed core.Results: Cancer was detected in 145 biopsy cores from 35 of 118 subjects (30%). Among 57 subjects with no previous biopsy, the cancer detection rate was 40% (23/57). Cancer was found in 15% (65/432) of unrestricted targeted cores and in 11% (80/704) of targeted sextant cores. Of 35 subjects with cancer, 28 were detected by both techniques. Six subjects were detected only by targeted sextant biopsy, whereas 1 subject was detected only by unrestricted targeted biopsy. Although 40% (32/80) of positive targeted sextant cores were obtained at the gland apex, only 17% (11/65) of positive unrestricted targeted cores were obtained from the gland apex. Among 432 unrestricted targeted biopsy cores, only 18% (80) were directed to the apex.Conclusions: Although the per-core cancer detection rate of unrestricted targeted biopsy was slightly higher when compared to the targeted sextant approach, the unrestricted technique missed cancers at the apex of the prostate. The low proportion of targeted biopsy cores in the apex suggests that contrast enhancement is less conspicuous at the apex. To maximize cancer detection, we recommend that any contrast-enhanced biopsy strategy must include targeted cores of the prostatic apex. Objective: Recent studies have demonstrated improved detection of prostate cancer with targeted biopsy using microbubble contrast agents. We evaluated cancer detection with two different contrast-enhanced biopsy strategies: unrestricted targeted biopsy of the most suspicious areas in the outer gland, and targeted sextant biopsy of the most suspicious area within each sextant. Methods: One hundred eighteen subjects with an elevated PSA (>4 ng/ml) or abnormal digital rectal examination were evaluated by transrectal sonography during infusion of a microbubble contrast agent (Imagent: Alliance Pharmaceuticals). Up to 4 unrestricted targeted biopsy cores were directed toward the most suspicious area(s) of the outer gland during contrast-enhanced harmonic gray scale and Doppler imaging. Six additional biopsy cores were obtained in a modified sextant distribution to target the most suspicious area within each sextant. Any sextant with no suspicious area was sampled with a laterally directed core. Results: Cancer was detected in 145 biopsy cores from 35 of 118 subjects (30%). Among 57 subjects with no previous biopsy, the cancer detection rate was 40% (23/57). Cancer was found in 15% (65/432) of unrestricted targeted cores and in 11% (80/704) of targeted sextant cores. Of 35 subjects with cancer, 28 were detected by both techniques. Six subjects were detected only by targeted sextant biopsy, whereas 1 subject was detected only by unrestricted targeted biopsy. Although 40% (32/80) of positive targeted sextant cores were obtained at the gland apex, only 17% (11/65) of positive unrestricted targeted cores were obtained from the gland apex. Among 432 unrestricted targeted biopsy cores, only 18% (80) were directed to the apex. Conclusions: Although the per-core cancer detection rate of unrestricted targeted biopsy was slightly higher when compared to the targeted sextant approach, the unrestricted technique missed cancers at the apex of the prostate. The low proportion of targeted biopsy cores in the apex suggests that contrast enhancement is less conspicuous at the apex. To maximize cancer detection, we recommend that any contrast-enhanced biopsy strategy must include targeted cores of the prostatic apex.

Contrast-enhanced ultrasonography and tissue harmonic imaging in the evaluation of renal diseases

Contrast-enhanced ultrasonography and tissue harmonic imaging in the evaluation of renal diseases

Radiofrequency ablation therapy under contrast-enhanced harmonic imaging guidance for recurrence after local ablation therapy for hepatocellular carcinoma: A randomized controlled study

Radiofrequency ablation therapy under contrast-enhanced harmonic imaging guidance for recurrence after local ablation therapy for hepatocellular carcinoma: A randomized controlled study

Analysis of vascularity of breast tumors: comparison of high-frequency ultrasound and contrast-enhanced color harmonic imaging

Analysis of vascularity of breast tumors: comparison of high-frequency ultrasound and contrast-enhanced color harmonic imaging

Therapeutic Effect of Chemoembolization Therapy on Hepatocellular Carcinoma: Evaluation with Contrast-Enhanced Power Doppler Sonography and Contrast-Enhanced Harmonic Imaging

Twenty-three cases of HCC were selected for transcatheter arterial chemoembolization therapy in our institution between January 2000 and March 2001. The size of the lesions ranged between 18 and 56 mm in diameter (mean size, 32 mm). Nineteen cases were men and 4 were women (mean age, 58 years). All patients had cirrhosis of the liver, 16 patients had posthepatic cirrhosis and 7 had alcoholic cirrhosis. Hepatocellular carcinomas were diagnosed by means of sonographically guided percutaneous biopsy. The hepatic lesions were examined with contrast-enhanced PDU before and one and six months after the interventional procedure. Of the 23 tumors, twelve lesions were also studied with contrast-enhanced wideband harmonic imaging (WHI). In our study we used a Sonoline Elegra ultrasound system (Siemens Medical Systems, Issaquah, WA) with wideband harmonic imaging (EnsembleTM Contrast Imaging) installed on a 3,5 MHz convex transducer (3.5C40 transducer). The sonographic examination began with a real-time B-mode study of the liver in order to localize the lesions and select the best scan plane. Then, an unenhanced power Doppler exam of the lesion was performed with low-pulse repetition frequency for detection of tiny vascular structures. This examination was repeated after intravenous administration of 2,5 gr. of a galactose-based ultrasound contrast agent (Levovist®, Schering AG, Berlin, Germany) at a concentration of 300 mg/ml, and presence of arterial flow inside and/or at the periphery of the lesion was evaluated. Spectrum analysis of these vessels was obtained, if possible. In 12 cases we also performed a contrast-enhanced wideband harmonic exam of the lesions. Wideband harmonic imaging was performed by the same radiologist, with previous setting of the following parameters: frequency of 2–2,5 MHz, single focal zone, parallel processing on, maximum frame rate ( 10/sec), persistence off and medium line density (RES/SPEED 3 or 4). A second injection of contrast agent at the same concentration was administered and the liver was scanned intermittently during the first 60 seconds, and 3 minutes after the injection in order to study the liver specific phase of Levovist. Images were obtained 20, 40 and 60 seconds after administration of contrast agent and 3 minutes later in order to evaluate the arterial, capillary and late phase of enhancement of the tumours. The images were stored digitally on the hard disk in the US scanner. The examinations were also recorded on videotape. The outcome of therapy was established by means of unenhanced and enhanced spiral CT exam. Spiral CT was performed with a Toshiba Asteion TSX-021A equipment Acad Radiol 2002; 9(suppl 2):S382–S383

Application of contrast-enhanced ultrasonography to the local treatment of hepatocellular carcinoma

Areas of residual tumors after RFA or PEI therapy are not distinguishable from necrotic tissues on US. The sonographic findings of gray-scale, color Doppler and power Doppler scanning after RFA or PEI therapy do not correlate well with the overall necrotic shape, or with the volume or extent of coagulation necrosis induced. Therefore, contrast-enhanced CT or MRI is generally necessary to assess the efficacy of the treatment. The absence of intensified areas on contrast-enhanced CT indicates the disappearance of the blood supply and, by inference, a successful treatment. Conversely, focal areas of persistent contrast enhancement usually indicate viable tumor cells, and, therefore, warrant further treatment to achieve a complete tumor necrosis.Harmonic gray-scale images can extract only the blood flow echoes created by destruction of microbubbles, whilst echoes from tissue are effectively cancelled. This mode makes it possible to clearly depict residual blood flow in tumors after therapy. Because contrast-enhanced harmonic sonography is easy to perform and provides real-time needle insertion guidance, it may be favored in monitoring response to localized therapies, obviating unnecessary CT and treatment sessions.Although contrast-enhanced CT can clearly depict residual areas of tumors after RFA or PEI therapy, it does not make possible real-time guidance in percutaneous therapies. Furthermore, the retention of lipiodol in HCC lesions sometimes makes it difficult to distinguish the hyperattenuating area of contrast enhancement from that of lipiodol when the retention of iodized oil in tumors is incomplete.Contrast-enhanced harmonic gray-scale images can reveal the tumor vascularity in patients with HCC, after transcatheter arterial embolization and percutaneous therapies, with high sensitivity and accuracy in comparison with dynamic CT. This capability of harmonic imaging for depicting residual cancer cells in HCCs after treatment facilitates a correct guidance for the insertion of a needle on US monitoring, which cannot be achieved by any other imaging modalities including CT and MRI.The noninvasive vascular technique of contrast-enhanced harmonic imaging is an extremely sensitive tool for detecting the intranodular blood flow in hepatic tumors. This method is drastically changing the diagnostic and therapeutic strategy of hepatic tumors, especially HCC, resulting in an eventual improvement in the prognosis of patients with HCC.

Contrast-enhanced quantitation of left ventricular ejection fraction: What is the best method?

The need to enhance the echocardiographic determination of left ventricular ejection fraction (LVEF) is greatest in patients with suboptimal images. We have previously demonstrated that in difficult-to-image patients, contrast-enhanced power harmonic imaging resulted in accurate calculation of LVEF by using Simpson's method. However, the incremental accuracy of contrast enhancement with other methods of determining LVEF has not been examined. This study prospectively assessed the comparative accuracy of LVEF determination by using the Quinones' method with fundamental imaging (FU), tissue harmonic imaging (TH), contrast-enhanced harmonic imaging [TH(CON)], as well as Quinones' method with contrast-enhanced power harmonic imaging [POW(QUIN)] in 62 patients with suboptimal images. LVEF was also calculated by using contrast-enhanced power harmonic imaging and Simpson's method [POW(SIMP)] in these patients. We demonstrated that LVEF calculated from the POW(QUIN) mode had the best agreement with radionuclide angiography (standard of comparison) compared with FU, TH, and TH(CON). However, POW(SIMP) was even more accurate. In conclusion, when the Quinones' method was used to calculate LVEF in difficult-to-image patients, POW(QUIN) mode was the most accurate. However, POW(SIMP) was even more accurate and should be the method of choice when a high degree of quantitative accuracy is required. (J Am Soc Echocardiogr 2001;14:1183-90.)

Diagnosis of advanced hepatocellular carcinoma using contrast-enhanced harmonic gray-scale imaging with enhancement agents (Levovist): Correlation with helical CT and US angiography

We compared contrast-enhanced harmonic gray-scale imaging with helical CT and US angiography to evaluate vascularity in advanced hepatocellular carcinoma (HCC). Contrast-enhanced harmonic gray-scale imaging using Levovist (Nihon Schering, Tanabe) as the contrast agent and enhanced helical CT were performed on 38 patients with 45 lesions (29 men and 9 women aged 41 to 83 years; mean age, 66 years; mean maximum tumor diameter, 30.5±23.0 mm), and angiography was performed to evaluate 37 lesions from 32 of these 38 patients (24 men and 8 women, aged 41 to 79 years; mean age, 65 years; mean maximum tumor diameter, 27.9±17.9 mm). Contrast-enhanced harmonic gray-scale imaging showed hypervascular enhancement in 41 of the 45 lesions; the other 4 lesions were not visualized as hypervascular because 3 of the them could not be detected with non-enhanced US and the remaining lesion was situated deep in the liver and more than 11 cm from the surface of the body. Helical CT showed areas of high attenuation in 40 of the 45 lesions, leaving the other 5 lesions equivocal, while US angiography achieved positive enhancement in 36 of 37 lesions. Intratumoral vessels were visualized with contrast-enhanced harmonic gray-scale imaging in 25 of the 45 lesions; however; intratumoral vessels were seen in only 4 of the 45 lesions examined with helical CT. In evaluating vascularity in advanced HCC, contrast-enhanced harmonic gray-scale imaging with Levovist was as effective as US angiography and more effective than helical CT. Motion artifacts produced by the heart make it difficult to evaluate vascularity in advanced HCC located in the left lobe of the liver with Doppler sonography. Contrast-enhanced harmonic gray-scale imaging can show intratumoral vessels and hypervascular enhancement of the tumor without motion artifacts, however, even when the tumor is located near the heart or large vessels. Contrast-enhanced harmonic gray-scale imaging is useful for evaluating vascularity in advanced HCC when the tumor can be visualized with non-enhanced US.

Contrast harmonic ultrasound is a breakthrough technology in the diagnosis and treatment of hepatocellular carcinoma

The noninvasive vascular technique of contrast-enhanced harmonic imaging is an extremely sensitive tool for detecting the intranodular blood flow in hepatic tumors. This method is drastically changing the diagnostic and therapeutic strategy of hepatic tumors, especially HCC, resulting in an eventual improvement in the prognosis of patients with HCC.

Contrast-enhanced subtraction harmonic sonography for evaluating treatment response in patients with hepatocellular carcinoma.

Our objective was to assess the usefulness of contrast-enhanced subtraction harmonic sonography in evaluating the treatment response of patients with hepatocellular carcinoma. Thirty-two hepatocellular carcinoma lesions in 26 patients (age range, 44-85 years; mean age, 66 years) were examined with Levovist-enhanced intermittent harmonic imaging before and after therapy. A Toshiba Powervision 8000 was used. A subtraction image was obtained by digitally subtracting the last-frame harmonic image from the first-frame image when multishot mode was preset. Results of contrast-enhanced CT were compared with the results of subtraction harmonic imaging. Before therapy, an enhancement pattern of tumor vascularity was seen for 93.8% (30/32) of hepatocellular carcinoma nodules on subtraction harmonic imaging. After therapy, subtraction harmonic imaging showed 46.7% (14/30) enhancement (incomplete tumor necrosis) and 53.3% (16/30) no enhancement (complete tumor necrosis). When dynamic CT was the gold standard, the sensitivity, specificity, and accuracy of subtraction harmonic imaging were 93.3%, 100%, and 96.7%, respectively. Intratumoral flow signals in hepatocellular carcinoma after therapy on harmonic imaging were used as a guide to target additional percutaneous therapy. Digital subtraction contrast-enhanced harmonic imaging can depict tumor vascularity in hepatocellular carcinoma after therapy sensitively and accurately. Because it is easy to perform and provides real-time needle insertion guidance, it may be preferable to perform after localized therapy to monitor treatment response, which will reduce unnecessary CT scanning.

Renal blood flow in pigs: changes depicted with contrast-enhanced harmonic US imaging during acute urinary obstruction.

To evaluate contrast agent-enhanced harmonic ultrasonographic (US) imaging and Doppler hemodynamics during acute urinary obstruction. In 12 piglets, the distal ureter was obstructed for 60 minutes, followed by intravenous injection of furosemide. In six piglets, ureteral pressure was further elevated to mean arterial pressure, and in six other piglets ureteral obstruction was released. Contrast-enhanced harmonic imaging was performed, and interlobar resistive index (RI) and renal blood flow were determined at baseline and during each experimental condition. A bolus injection curve was constructed by plotting mean pixel intensity versus time, and the area under this normalized curve was compared with renal blood flow values. Ureteral obstruction and high ureteral pressure reduced cortical renal blood flow to 88% and 66%, respectively, of baseline values. Administration of contrast agent resulted in marked homogeneous enhancement of the renal cortex. The area under the curve diminished during ureteral obstruction and correlated well with mean cortical blood flow. RI correlated well with renal perfusion pressure but poorly with changes in renal blood flow. Contrast-enhanced harmonic US imaging depicts changes in renal blood flow during acute obstruction. Interlobar RI is a good predictor of renal perfusion pressure but not of changes in renal blood flow.

Harmonic imaging with gas-filled microspheres: Initial experiences

The introduction of safe and efficacious ultrasound contrast agents, which significantly enhance the backscattered signals, has allowed previously inaccessible areas of slow flow to be imaged. However, imaging organ perfusion or small deep-lying vessels remains difficult. The ability of harmonic imaging to resolve these problems has been investigated. Harmonic imaging uses the nonlinear properties of microbubble-based agents by transmitting at the fundamental frequency but receiving at the second harmonic. In vitro measurements revealed a harmonic response 15 dB below the fundamental for a driving frequency of 2.5 MHz at an acoustic pressure of 50 kPa for one particular contrast medium. In vivo, two different gas-filled microbubble agents were administrated to 10 dogs and three rabbits. Three different scanners were used to obtain images of kidneys, liver, heart, and vessels in harmonic and conventional gray-scale, pulsed Doppler, and color Doppler modes. Enhancement lasted significantly longer in harmonic than in conventional modes (94 s; P = 0.00003). Harmonic images were less susceptible to artifacts, such as acoustic shadowing, and a wider range of dosages could therefore be used. A clear increase in the (flow) signal-to-clutter ratio was observed. Harmonic images were, however, very dependent on focal zone settings. These preliminary results demonstrate the potential of contrast-enhanced harmonic imaging, but further studies are required to establish clinical efficacy. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 69–81, 1997

On the feasibility of real-time, in vivo harmonic imaging with proteinaceous microspheres.

Harmonic imaging is a new contrast-specific imaging modality, which utilizes the nonlinear properties of microbubble-based sonographic contrast agents by transmitting at the fundamental frequency but receiving at the second harmonic frequency. The feasibility of improving the detection of slow, small-volume blood flow using real-time harmonic imaging has been investigated in vivo. Proteinaceous microspheres (FS069) were administrated to four dogs, two woodchucks (with multiple hepatomas), and one rabbit. Three different scanners were used to obtain real-time images of kidneys and liver (including vessels) in harmonic and conventional gray scale and color flow modes. The duration of contrast enhancement lasted significantly longer in harmonic than in conventional modes (on average 87 s; P = 0.008). Harmonic images were less susceptible to artifacts, such as acoustic shadowing, and a clear increase in the (flow) signal-to-noise ratio was observed. These preliminary in vivo results demonstrate the feasibility of performing real-time, contrast-enhanced harmonic imaging, but further studies are required to establish clinical efficacy.