Low-attenuation oral GI contrast agents in abdominal-pelvic computed tomography.

BACKGROUND: We designed and evaluated a low-attenuation oral contrast agent for abdominal-pelvic computed tomography (CT). METHODS: In vitro studies, were performed initially to evaluate the imaging characteristics of multiple solutions. These studies resulted in two solutions being compared with the presently accepted oral CT agents of dilute iodinated contrast and water. Ninety-eight consecutive subjects already scheduled for routine outpatient abdominal-pelvic CT were enrolled. Subjects were randomized to water (n = 30), fiber solution (n = 32), polyethylene glycol (PEG; n = 11), or dilute iodinated solution (DI; n = 25). Examinations were then evaluated for gastric distention, small bowel distention, small bowel wall visualization, and colonic transit. A questionnaire was given to the study subjects for feedback concerning taste and potential side effects from these agents. RESULTS: PEG tended to provide better bowel distention, wall visualization, and colonic transit compared with water, fiber solution, and DI. Areas of statistical significance included: (1) average bowel diameter in the left upper quadrant for water was 17.50 mm, whereas that for PEG was 21.88 mm (p < 0.05); (2) average bowel diameter in the pelvis for water was 14.79 mm, that for fiber was 15.67 mm, and that for PEG was 18.48 mm (p < 0.05); (3) wall visualization was better with PEG than with fiber (p < 0.05); (4) successful transit of contrast to the colon occurred in every subject who received PEG compared with only 20% of those received water and 39% of those who received fiber (p < 0.05). Similar trends for the superiority of PEG over DI were noted, although many of these did not reach statistical significance. CONCLUSION: PEG solution has imaging characteristics related to bowel wall visualization, luminal distention, and colonic transit that make it an effective oral agent for abdominal pelvic CT examination.

Musculoskeletal ultrasound: an update.

In summary, musculoskeletal sonography is a rapidly growing field of interest around the world. Outside of America, it is often the first and definitive imaging modality fordisorders of the musculoskeletal system. Musculoskeletal ultrasound offers rapid, inexpensive, real-time examination of the structures of interest with easy comparison to the contralateral side. Principles of one area of musculoskeletal sonography easily generalize to other areas.

Three-dimensional CT angiography of spontaneous portosystemic shunts.

Spontaneous portosystemic shunts (varices) are a well-known complication of severe liver disease and portal hypertension. Computed tomographic (CT) angiography was used to image the hepatic vasculature of 198 patients with end-stage liver disease in anticipation of liver transplantation. Performance of a delayed acquisition during the portal phase of enhancement enables evaluation of portal and variceal anatomy without the need for an additional injection of contrast material. Three-dimensional (3D) reconstruction of portal-phase CT angiograms enhances the perception of the courses and anatomic relationships of varices. This information is valuable for surgical planning. Common varices include the left gastric vein, short gastric veins, paraumbilical veins, and splenic vein; in cases of more unusual, complex shunts, 3D rendering is indispensable. By precisely demonstrating the courses of varices, CT angiography allows the surgeon to plan the operative approach and determine the need for surgical varix ligation or preoperative interventional embolization.

Effect of vascular occlusion on radiofrequency ablation of the liver: results in a porcine model.

OBJECTIVE: This study determined the effect of vascular occlusion on radiofrequency lesion shape, volume, and temperature in a porcine liver model. SUBJECTS AND METHODS: Radiofrequency lesions (n = 33) were created in the livers of six domestic pigs in vivo using a multiprong radiofrequency electrode. Lesions were randomly assigned to one of four vascular occlusion groups: portal vein, hepatic artery, Pringle maneuver (both hepatic artery and portal vein), or no occlusion. Radiofrequency parameters were time, 7 min; power, 50 W; and target temperature, 100 degrees C. Temperatures were measured 5, 10, and 15 mm from the electrode. After the animals were sacrificed, the lesions were excised. Lesion volume, diameter, and shape; maximum temperature; and time exposed to lethal temperatures (42-60 degrees C) were determined. RESULTS: Lesion volume was greatest with the Pringle maneuver lesions (12.6 +/- 4.8 cm(3)), followed by occlusion of the portal vein (8.6 +/- 3.8 cm(3)), occlusion of the hepatic artery (7.6 +/- 2.9 cm(3)), and no occlusion (4.3 +/- 1.0 cm(3)) (p < 0.05). Maximum lesion diameter was similar with the Pringle maneuver (3.3 +/- 0.3 cm), the portal vein (3.3 +/- 0.2 cm), and the hepatic artery (3.2 +/- 0.2 cm) groups compared with no occlusion (2.6 +/- 1.0 cm) (p < 0.05). Minimum lesion diameter ranged from 2.9 cm for Pringle maneuver lesions to 1.0 cm for lesions with no occlusion (p < 0.05). Vascular occlusion increased the time tissue was exposed to lethal temperatures (> 42-60 degrees C) and created more spherical lesions than no occlusion. CONCLUSION: Vascular occlusion combined with radiofrequency ablation increases the volume of necrosis, creates a more spherical lesion, and increases the time tissue is exposed to lethal temperatures when compared with radiofrequency alone. Most of this vascular occlusion effect could be accomplished with hepatic artery occlusion alone.

Prostate vascular flow: the effect of ejaculation as revealed on transrectal power Doppler sonography.

OBJECTIVE: The objective of our study was to determine the effect of ejaculation on prostate vascular flow. SUBJECTS AND METHODS: Using power Doppler technology, we performed four transrectal sonographic examinations before and immediately, 6 hr, and 24 hr after ejaculation in 10 healthy volunteers. Images were assessed by three independent observers. RESULTS: Ninety-seven percent of the images ranked as having the least flow were from the baseline examination. There was a significant difference between the rankings when categorized into the four time sets (mean score for the baseline group was 1.1, whereas for the immediate, 6-, and 24-hr postejaculation groups it was 2.5, 2.9, and 2.4, respectively (p<0.0001). The only statistically significant difference was between the baseline and the three remaining groups. Interobserver agreement was high, with the chance-corrected measure of agreement of 0.78. CONCLUSION: Transrectal sonography revealed that prostate vascular flow increases dramatically after ejaculation and remains elevated for at least 24 hr. This observation should be considered when power Doppler sonography is used to assess for potential hyperemia in patients suspected of having prostate abnormalities.

Echogenic intracardiac focus in 2nd-trimester fetuses with trisomy 21: usefulness as a US marker.

PURPOSE: To determine whether there is a relationship between the presence of an echogenic intracardiac focus in 2nd-trimester fetuses and trisomy 21 (Down syndrome). MATERIALS AND METHODS: A complete genetic ultrasonographic (US) scan was obtained in 3,303 consecutive fetuses with an estimated gestational age of 14.0-24.0 weeks (mean +/- SD, 17.1 weeks +/- 1.75). US was performed in a prospective fashion without any knowledge of karyotype and included assessment of any potential echogenic intracardiac focus (ie, calcified papillary muscle). Karyotypes were obtained in all fetuses. Maternal ages ranged from 13.0 to 47.4 years (mean, 35.1 years +/- 5.1). The prevalence of Down syndrome in this population was 1.6% (53 of 3,303 fetuses). RESULTS: An echogenic intracardiac focus was seen in 147 of the 3,192 karyotypically normal fetuses (4.6%) and 16 of the 53 fetuses with trisomy 21 (30%). The positive predictive value (PPV) of an echogenic intracardiac focus in this high-risk population was 9.8%; sensitivity, 30%; specificity, 95%; likelihood ratio, 6.6; and relative risk (RR), 8.2 (P <.001). For a sonographically isolated echogenic intracardiac focus, the PPV was 3.7%; sensitivity, 19%; specificity, 95%; likelihood ratio, 4.2; and RR, 4.8 (P =.002). CONCLUSION: A sonographically isolated echogenic intracardiac focus (no other anomalies or markers noted on a complete genetic sonogram) was associated in our high-risk population with a 4.8-fold (95% CI: 1.8, 12.5) increase in RR for trisomy 21 (P =.002).

The "genetic sonogram": comparison of the index scoring system with the age-adjusted US risk assessment.

PURPOSE: To compare two ultrasonographic (US) methods for prenatal detection of fetal Down syndrome. MATERIALS AND METHODS: Genetic amniocentesis was successfully performed in 3,303 consecutive women with high-risk pregnancies (mean gestational age, 17.1 weeks). All patients underwent a complete "genetic US" examination prospectively. Risk was assessed by using (a) various modifications of the index scoring system (ISS) and (b) the age-adjusted US risk assessment (AAURA). RESULTS: The prevalence of Down syndrome in this population was 1.6% (53 of 3,303). By using a threshold of at least 2 points to detect trisomy 21, the best ISS had a sensitivity of 45.3%, false-positive rate of 4.9%, likelihood ratio of 9.3, and positive predictive value in the high-risk population in this study of 13.3%. Lowering the threshold to 1 point increased the sensitivity to 60.4% but increased the false-positive rate to 15.8%. Adding points for age increased the sensitivity to 67.9% but increased the false-positive rate to 24.3%. Results of using AAURA to detect trisomy 21 were nearly identical, with a sensitivity of 43.4% and false-positive rate of 4.9% at a 1 in 36 risk threshold and a sensitivity of 69.8% and false-positive rate of 26.1% at a 1 in 200 threshold. Trisomies 18 and 13 were detected with sensitivities of 80.0% and 100.0%, respectively, with either system. CONCLUSION: The modified ISS and AAURA are equivalent in screening for Down syndrome, with detection of approximately half of all trisomy 21 fetuses at a 5% false-positive rate.

Cerebellar and frontal lobe hypoplasia in fetuses with trisomy 21: usefulness as combined US markers.

PURPOSE: To confirm that cerebellar hypoplasia is ultrasonographically recognizable in second-trimester fetuses with Down syndrome and determine whether the combination of frontal lobe shortening and cerebellar hypoplasia is superior to either measurement alone as a marker of this abnormality. MATERIALS AND METHODS: The frontothalamic distance (FTD) and transcerebellar diameter (TCD) were measured in 52 middle-trimester fetuses with euploid karyotypes and in 52 fetuses with Down syndrome. Receiver operating characteristic (ROC) curves were constructed with various thresholds for observed-to-expected ratios (O/Es) of the FTD, TCD, and average of these two parameters. RESULTS: The area under the average ROC curve, 0.80, was greater than that for either the FTD alone (0.75) or the TCD alone (0.76). At a 6% false-positive rate, the sensitivity for the detection of Down syndrome obtained with the average parameter was 34% better than that obtained with only the FTD and 12% better than that obtained with only the TCD. With an O/E threshold of 0.92 for the average parameter, an odds ratio of 16.3 and positive predictive value of 12.7% in the high-risk population were achieved. CONCLUSION: Although both measurements are individually statistically significant, the combination of TCD and FTD measurements may be superior to the use of either parameter alone as a marker of trisomy 21.

Impact of double helical CT and three-dimensional CT arteriography on surgical planning for hepatic transplantation.

BACKGROUND: To assess the impact of preliver transplant double helical computed tomography (DHCT) and three-dimensional computed tomography arteriography (3D-CTA) on surgical planning for hepatic transplantation. METHODS: Vascular findings detected on DHCT/3D-CTAs of 80 patients were shown to the transplant surgeon in a blinded fashion. These findings included hepatic arterial anatomy, diameters of the major vessels that supplied the liver, celiac axis stenosis, splenic artery (SA) aneurysms, and portal vein thrombosis (PVT). The surgeon was asked to state the "planned" surgical approach for each case based on scan findings. These results were subsequently compared with what "actually" occurred at transplantation by review of surgical records. RESULTS: Fifty-five patients had conventional and 25 patients had nonconventional hepatic arterial anatomy. Three patients had PVT, three patients had celiac axis stenosis, and three patients had SA aneurysms. Correlation between the "actual surgical technique" and the "planned surgical approach" was seen in 50/55 (91%) patients with conventional and in 23/25 (92%) patients with nonconventional anatomy. Five patients requiring aortohepatic interposition grafts for arterial anastomoses had either severe celiac axis stenoses or arterial inflow vessels that were 3 mm or smaller. Three patients with PVT underwent successful surgical resection of the thrombosed segment and standard PV anastomoses as planned. Patients with complete replacement of hepatic arterial supply to the superior mesenteric artery required alteration of the sequence of the vascular anastomoses. Patients with SA aneurysms had surgical ligation of the splenic artery. CONCLUSIONS: DHCT/3D-CTA provides noninvasive means to identify findings that have significant impact on surgical planning for hepatic transplantation including celiac axis stenosis, diameter of inflow arterial vessel

Iliac angle as a marker for Down syndrome in second-trimester fetuses: CT measurement.

PURPOSE: To determine if the iliac angle is greater in second-trimester fetuses with trisomy 21 than in euploid fetuses and to establish the best level and plane for measuring this angle by using three-dimensional computed tomography (CT). MATERIALS AND METHODS: CT was performed in 18 formalin-preserved fetuses (eight trisomy 21, 10 euploid control fetuses), and the pelvic bone anatomy was reconstructed three-dimensionally. Iliac angles were measured in axial views at three levels in two planes. Data were analyzed nonparametrically with the Mann-Whitney test. RESULTS: The mean gestational ages for trisomy 21 and control fetuses were 17.0 and 16.7 weeks, respectively. The external plane was the easiest to measure and the most reproducible. The mean iliac angles were significantly greater (P < .05) in the trisomy 21 fetuses than in the control fetuses and were as follows: superior level, 95.6 degrees vs 76.4 degrees; middle level, 84.5 degrees vs 62.5 degrees; and lower level, 78.1 degrees vs 57.5 degrees. With a 90 degrees threshold, the superior iliac angle measurement had a sensitivity of 75%, a specificity of 89%, and an odds ratio of 24 for Down syndrome. CONCLUSION: Second-trimester fetuses with trisomy 21 have a significantly greater iliac angle than euploid fetuses have. The iliac angle varies with the axial level, with the widest angle at the most superior level. Measurement of the iliac angle at the most superior level is supported as a potential marker for Down syndrome at prenatal ultrasonography.

Treatment of inferior vena cava anastomotic stenoses with the Wallstent endoprosthesis after orthotopic liver transplantation.

PURPOSE: To evaluate the efficacy of the Wallstent endoprosthesis for treatment of stenotic or occlusive inferior vena cava (IVC) lesions refractory to balloon angioplasty in patients after orthotopic liver transplantation. MATERIALS AND METHODS: Wallstent endoprostheses were implanted in six patients with IVC anastomotic stenoses or occlusions that were refractory to balloon angioplasty. Follow-up included both duplex ultrasound (US) and clinical evaluations. RESULTS: Ten stents were successfully implanted in six patients. Five of six patients (83%) demonstrated primary patency on duplex US for a mean period of 11 months (range, 4-17 months). One patient's symptoms recurred within 3 weeks after intervention. This patient underwent repeated stent placement. Follow-up duplex US in this patient demonstrated primary assisted patency at 7 months. Mean clinical follow-up was 12 months (range, 7-18 months). Other than the previously described case, no patient developed recurrent symptoms of IVC stenosis or occlusion. Two patients who experienced hemorrhagic complications secondary to anticoagulation were treated successfully. CONCLUSIONS: The Wallstent endoprosthesis is a useful adjunct for treatment of IVC stenosis or occlusions in patients who have undergone orthotopic liver transplantation when these lesions are refractory to simple balloon angioplasty.

Imaging of oncologic patients: benefit of combined CT and FDG PET in the diagnosis of malignancy.

OBJECTIVE: The purpose of this study was to assess the benefit of combined CT and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in diagnosing malignancy. MATERIALS AND METHODS: The records of 26 patients with intraabdominal and intrathoracic neoplasms who underwent CT and FDG PET between January 1995 and September 1996 were retrospectively reviewed. Most of these patients had inconclusive findings on prior CT for the diagnosis of malignancy. Only sites of potential malignant disease were included in the data analysis. Presence or absence of malignancy was confirmed by histopathology or follow-up CT. Three observers experienced in abdominal imaging used CT findings alone to estimate level of suspicion (1 = definitely not malignant to 5 = definitely malignant) for primary or recurrent neoplasms (n = 21), distant metastases (n = 25), and neoplastic nodal involvement (n = 18). Six weeks later the three observers reviewed the same CT examinations supplemented with FDG PET and reestimated suspicion of malignancy. Receiver operating characteristic methodology was used to analyze the results. Sensitivity, specificity, positive and negative predictive values, and accuracy in diagnosis of malignant disease were calculated using level 4 (probable malignancy) as the cutoff for the presence of disease. RESULTS: The mean area under the receiver operating characteristic curve, indicating successful diagnosis of malignancy, was .82 for CT alone and .92 for CT with FDG PET (p < .05). The accuracies for diagnosis of primary or recurrent neoplasms, distant metastases, and neoplastic nodal involvement were 62%, 68%, and 83%, respectively, for CT alone and 81% (p = .06), 88% (p = .03), and 89% (p > .25), respectively, for CT with FDG PET. Also, supplemental FDG PET imaging improved observer confidence and accuracy in diagnosing recurrent neoplasm in four (36%) of 11 patients who had undergone surgery or chemoradiation and in diagnosing four (29%) of 14 extrahepatic sites that had potential metastases. CONCLUSION: Diagnosis of malignancy in oncologic patients is significantly improved when CT is supplemented with FDG PET. Combined imaging is particularly helpful in the evaluation of potential recurrence in previously treated patients and for diagnosing extrahepatic lesions that may be distant metastases.

Frontal lobe shortening in second-trimester fetuses with trisomy 21: usefulness as a US marker.

PURPOSE: To determine whether the frontal lobe is disproportionately smaller than normal in second-trimester fetuses with Down syndrome by using prenatal ultrasonographic (US) measurements of the frontothalamic distance (FTD). MATERIALS AND METHODS: The FTD, measured from the inner table of the frontal bone to the posterior margin of the thalamus, was measured in 43 fetuses (mean gestational age, 17.2 weeks +/- 1.3 [standard deviation]; range, 15.0-20.4 weeks) with chromosomally proved trisomy 21 and in 160 chromosomally normal fetuses (mean gestational age, 17.1 weeks +/- 1.5; range, 14.5-22.5 weeks). Other cranial biometric ratios also were calculated. RESULTS: The FTD was best predicted from the estimated gestational age (EGA) in the euploid population with the quadratic equation FTD = -0.0120 x EGA2 + 0.6917 x EGA - 5.2349 (R2 = .731) or from the biparietal diameter (BPD) with the linear equation FTD = 0.6837 x BPD + 0.5525 (R2 = .731). If an observed-to-expected ratio of 0.84 is used as a cutoff sign to screen for trisomy 21, a sensitivity of 16%, specificity of 97%, odds ratio of 6.03 (95% confidence interval, 1.81, 20.1), and relative risk of 5.98 are achieved. CONCLUSION: The frontal lobe is statistically significantly smaller in fetuses with trisomy 21. US measurement of the FTD may prove to be a useful adjunctive screening tool if used with other markers for Down syndrome.

Assessment of fetal and placental blood flow in primates using contrast enhanced ultrasonography.

Ultrasonographic contrast agents that stay within the vascular space and do not cross the placenta may permit differentiation between the maternal and fetal portions of the placenta and may be clinically useful for diagnosis of placental abnormalities. This study was performed to assess the effects of Levovist (Schering AG, Berlin) on the placental circulation and to determine whether hemodynamic effects on the fetus occur. Ten studies were performed in five pregnant macaques (median weight, 9.15 kg; range, 6.15 to 11 kg; median gestational age, 121 days; range, 34 days to term) under anesthesia. Gray scale, color, and duplex Doppler sonographic scans of the fetus and placenta were acquired using a 5 MHz curved array transducer. Fetal heart rate, resistive index, and systolic-diastolic ratios were measured in the fetal middle cerebral artery, aorta, umbilical artery, and uterine artery before and after administration of contrast agent. The following dose regimen was tested: 5 ml of physiologic saline solution followed by 0.1 ml/kg of 300 mg/ml Levovist (diagnostic dose), 0.5 ml/kg of 400 mg/ml Levovist (maximum dose), and 5 ml physiologic saline solution. The order of diagnostic dose and maximal dose was randomized among animals. Color enhancement of the basal portions of the placenta was documented after administration of contrast agent. Heart rate and middle cerebral artery systolic-diastolic ratio did not change between baseline and injections. A 7% decrease of the resistive index from baseline to maximum dose was measured in the uterine artery (not significant). A 7.7% decrease in the systolic-diastolic ratio from baseline to maximum dose was recorded in the umbilical artery. However, an identical change was measured after saline solution was injected. The resistive index in the aorta increased by 2.6% from baseline to maximum dose, a change that was not significant (P > 0.5). Ultrasonographic contrast enhancement of the maternal circulation in placenta is demonstrated to be without significant effects on the fetal circulation as measured in this limited population.