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Contrast agents in the liver: new opportunities
S4
Ultrasound in Medicine and Biology
range, whereas in only 17/114 patients, CEUS has shown lower sensitivity than helical CT.
Contrast agents: Current status Goldberg BB, Radiology, Thomas Jefferson University Hospital, Philadelphia, PA Although ultrasound contrast agents have been researched for almost two decades, it has only been in the last several years that they have become available for limited clinical use. The FDA is evaluating several contrast agents in the United States, as are similar agencies around the world. Current research is evaluating such agents’ ability to detect cardiac infarction and ischemia. Research on contrast in detecting abnormalities in such organs as the liver, breast, thyroid, kidneys, pancreas, spleen, ovaries, and prostate has shown promise for improving ultrasound diagnostic capabilities. Research of these contrast agents’ vascular flow patterns as an aid to the detection and characterization of tumors and the evaluation of transplants is ongoing. Newer research is examining some contrast agents’ ability to be taken up by the lymphatic channels and to detect the sentinel lymph nodes, improving tumor staging. The usefulness of ultrasound contrast in treatment planning and monitoring treatment effectiveness is also being investigated. Ongoing research in the development of targeted ultrasound contrast agents is beginning to show promise. The success of CT and MR would not have been possible without the use of contrast agents. Up until the present, ultrasound has not had such contrast agents. However, current research suggests that ultrasound contrast agents should lead to the same dramatic improvement in the diagnostic capabilities of ultrasound, as has been the case with CT and MR contrast agents.
Volume 29, Number 5S, 2003
Contrast agents in the liver: New opportunities Cosgrove D, Imaging, Hammersmith Hospital, London, United Kingdom The development of contrast agents for ultrasound has opened up new opportunities, especially in the liver. The ideal vascular approach uses non-destructive pulses that allow the phased transit of the microbubbles in a lesion to be observed in real time in a color overlay over a gray-scale image used to ensure that the correct slice is being studied. Near-perfect solutions to the engineering problems this raises have been developed, and they reveal the characteristic timing and anatomical patterns of vascular and hypovascular malignancies as well as the typical features of flow to benign lesions that parallel those of three-phase, contrast-enhanced CT. In addition, many microbubbles show a more-or-less specific late phase in which the distribution of normal liver is depicted. Lesions with a low vascular volume, e.g., malignancies and devascularised liver, appear as defects with high contrast. This approach is useful in staging malignancies and in detecting trauma and is complementary to the vascular approach. Using a bolus of contrast as a tracer allows the transit time through the liver to be measured by noting the arrival time in the hepatic veins. It is shorter in metastatic involvement even when they are occult, and this promises to be useful for selecting patients with colorectal cancer who need chemotherapy. Similarly, the early arrival in cirrhosis could reduce the need for repeated biopsies to determine the timing of treatment in patients with chronic hepatitis.
NUCHAL TRANSLUCENCY Assessment of vesico-ureteric reflex in children with contrastenhanced ultrasound Albrecht T, Radiology and Nuclear Medicine, Universitaetsklinikum Benjamin Franklin, Berlin, Germany
Nuchal translucency—State-of-the-art Hyett JA, Obstetrics and Gynaecology, University College London, London, United Kingdom
Vesico-ureteric reflux is a common problem among children. To avoid nephropathy and ultimately hemodialysis, both feared complications, timely diagnosis is of high importance, so that adaquate therapy can be started while the damage to the kidney is still limited. Micturating cystography (MCU) is probably still the most commonly used diagnostic test for reflux. The main disadvantage of MCU is the relatively high radiation exposure (which includes the gonades in girls). Reflux sonography using an intravesical microbubble contrast agent such as Levovist (Schering AG, Berlin, Germany) has been introduced as a radiation-free alternative to MCU, which is highly sensitive in detecting reflux. The technique relies on sonographic detection of microbubbles in the ureters or pelvicaleceal system before, during, or after micturition. Several large studies have shown that reflux sonography is at least as sensitive as MCU in diagnosing reflux. It is best performed using contrast-specific ultrasound techniques such as pulse/phase inversion; however conventional B-mode technology can also be used. The latter approach requires a higher dose of contrast agent. The main disadvantage of reflux sonography is that the urethra—a common site of underlying pathology such as valves in boys—is not well depicted by US. First investigations for reflux in boys should therefore be performed by MCU. All other cases (first investigations in girls, follow-up examinations in boys, screening of asymptomatic siblings) should now be investigated by reflux sonography because it is radiation free and at least as reliable as MCU. Reflux sonography is increasingly replacing MCU for these indications in Europe.
At 11⫹0 to 13⫹6 weeks’ gestation, a collection of fluid in the posterior aspect of the neck becomes visible on ultrasound examination and is described as nuchal translucency. This is increased in the majority of fetuses affected by chromosomal abnormality as well as in many fetuses with congenital heart disease and a variety of genetic syndromes. NT thickness can be quantified and used as a screening test for chromosomal abnormality. Increased measurements are associated with an increased risk of chromosomal abnormality whilst measurements in the normal range allow a reduction in risk. A large series of 96,127 pregnancies demonstrated that 77% of Down’s pregnancies were detected for a 5% screen positive rate, comparable with the maternal serum quadruple test at 16 weeks’ gestation. NT screening is as effective for other major chromosomal abnormalities, and the sensitivity of the test has been confirmed in another 16 large studies, involving low-risk populations, which have examined a further 107,533 women with a detection rate of 83.3% for a 5.7% screen positive rate. Current issues involve the wide scale implementation of the test with adequate training for sonographers and the establishment of methods for quality control. The detection rate for Down’s syndrome can be further improved by combination with the biochemical markers PAPP-A and BhCG, which are also effective screening tools in the first trimester. Together, these markers can detect 90% of fetuses affected by Down’s syndrome at 11⫹0 to 13⫹6 weeks’ gestation, giving women an opportunity to have effective early prenatal screening and diagnosis.
Ultrasound in Medicine and Biology
range, whereas in only 17/114 patients, CEUS has shown lower sensitivity than helical CT.
Contrast agents: Current status Goldberg BB, Radiology, Thomas Jefferson University Hospital, Philadelphia, PA Although ultrasound contrast agents have been researched for almost two decades, it has only been in the last several years that they have become available for limited clinical use. The FDA is evaluating several contrast agents in the United States, as are similar agencies around the world. Current research is evaluating such agents’ ability to detect cardiac infarction and ischemia. Research on contrast in detecting abnormalities in such organs as the liver, breast, thyroid, kidneys, pancreas, spleen, ovaries, and prostate has shown promise for improving ultrasound diagnostic capabilities. Research of these contrast agents’ vascular flow patterns as an aid to the detection and characterization of tumors and the evaluation of transplants is ongoing. Newer research is examining some contrast agents’ ability to be taken up by the lymphatic channels and to detect the sentinel lymph nodes, improving tumor staging. The usefulness of ultrasound contrast in treatment planning and monitoring treatment effectiveness is also being investigated. Ongoing research in the development of targeted ultrasound contrast agents is beginning to show promise. The success of CT and MR would not have been possible without the use of contrast agents. Up until the present, ultrasound has not had such contrast agents. However, current research suggests that ultrasound contrast agents should lead to the same dramatic improvement in the diagnostic capabilities of ultrasound, as has been the case with CT and MR contrast agents.
Volume 29, Number 5S, 2003
Contrast agents in the liver: New opportunities Cosgrove D, Imaging, Hammersmith Hospital, London, United Kingdom The development of contrast agents for ultrasound has opened up new opportunities, especially in the liver. The ideal vascular approach uses non-destructive pulses that allow the phased transit of the microbubbles in a lesion to be observed in real time in a color overlay over a gray-scale image used to ensure that the correct slice is being studied. Near-perfect solutions to the engineering problems this raises have been developed, and they reveal the characteristic timing and anatomical patterns of vascular and hypovascular malignancies as well as the typical features of flow to benign lesions that parallel those of three-phase, contrast-enhanced CT. In addition, many microbubbles show a more-or-less specific late phase in which the distribution of normal liver is depicted. Lesions with a low vascular volume, e.g., malignancies and devascularised liver, appear as defects with high contrast. This approach is useful in staging malignancies and in detecting trauma and is complementary to the vascular approach. Using a bolus of contrast as a tracer allows the transit time through the liver to be measured by noting the arrival time in the hepatic veins. It is shorter in metastatic involvement even when they are occult, and this promises to be useful for selecting patients with colorectal cancer who need chemotherapy. Similarly, the early arrival in cirrhosis could reduce the need for repeated biopsies to determine the timing of treatment in patients with chronic hepatitis.
NUCHAL TRANSLUCENCY Assessment of vesico-ureteric reflex in children with contrastenhanced ultrasound Albrecht T, Radiology and Nuclear Medicine, Universitaetsklinikum Benjamin Franklin, Berlin, Germany
Nuchal translucency—State-of-the-art Hyett JA, Obstetrics and Gynaecology, University College London, London, United Kingdom
Vesico-ureteric reflux is a common problem among children. To avoid nephropathy and ultimately hemodialysis, both feared complications, timely diagnosis is of high importance, so that adaquate therapy can be started while the damage to the kidney is still limited. Micturating cystography (MCU) is probably still the most commonly used diagnostic test for reflux. The main disadvantage of MCU is the relatively high radiation exposure (which includes the gonades in girls). Reflux sonography using an intravesical microbubble contrast agent such as Levovist (Schering AG, Berlin, Germany) has been introduced as a radiation-free alternative to MCU, which is highly sensitive in detecting reflux. The technique relies on sonographic detection of microbubbles in the ureters or pelvicaleceal system before, during, or after micturition. Several large studies have shown that reflux sonography is at least as sensitive as MCU in diagnosing reflux. It is best performed using contrast-specific ultrasound techniques such as pulse/phase inversion; however conventional B-mode technology can also be used. The latter approach requires a higher dose of contrast agent. The main disadvantage of reflux sonography is that the urethra—a common site of underlying pathology such as valves in boys—is not well depicted by US. First investigations for reflux in boys should therefore be performed by MCU. All other cases (first investigations in girls, follow-up examinations in boys, screening of asymptomatic siblings) should now be investigated by reflux sonography because it is radiation free and at least as reliable as MCU. Reflux sonography is increasingly replacing MCU for these indications in Europe.
At 11⫹0 to 13⫹6 weeks’ gestation, a collection of fluid in the posterior aspect of the neck becomes visible on ultrasound examination and is described as nuchal translucency. This is increased in the majority of fetuses affected by chromosomal abnormality as well as in many fetuses with congenital heart disease and a variety of genetic syndromes. NT thickness can be quantified and used as a screening test for chromosomal abnormality. Increased measurements are associated with an increased risk of chromosomal abnormality whilst measurements in the normal range allow a reduction in risk. A large series of 96,127 pregnancies demonstrated that 77% of Down’s pregnancies were detected for a 5% screen positive rate, comparable with the maternal serum quadruple test at 16 weeks’ gestation. NT screening is as effective for other major chromosomal abnormalities, and the sensitivity of the test has been confirmed in another 16 large studies, involving low-risk populations, which have examined a further 107,533 women with a detection rate of 83.3% for a 5.7% screen positive rate. Current issues involve the wide scale implementation of the test with adequate training for sonographers and the establishment of methods for quality control. The detection rate for Down’s syndrome can be further improved by combination with the biochemical markers PAPP-A and BhCG, which are also effective screening tools in the first trimester. Together, these markers can detect 90% of fetuses affected by Down’s syndrome at 11⫹0 to 13⫹6 weeks’ gestation, giving women an opportunity to have effective early prenatal screening and diagnosis.