[Gaze-evoked amaurosis fugax]

Gaze-evoked amaurosis is a quite unique symptom. We present a 37-year-old patient with unilateral gaze-evoked amaurosis caused by an orbital tumor. Possible mechanisms include transient ischemia of the optic nerve and the retina or inhibition of the axonal impulses. While not common as a cause of amaurosis fugax, an orbital mass should be considered in the differential diagnosis of gaze-evoked atypical monocular amaurosis fugax.

Endoscopic removal of an intraorbital "tumor": a vital surprise

We present the first case report of an endoscopic removal of a living worm, species Dirofilaria repens, from the orbital cavity. As of today, over 410 cases of Dirofilaria repens infections in man are recorded in world literature, six of which were localized in the orbital cavity. In Austria we know of four cases of an infection with this parasite, but none in the orbit. Dirofilaria repens is widespread only in the Old World, particularly in Southern and Eastern Europe, in Asia Minor, and in Central and Southern Asia. The highest prevalence of the disease is recorded in Italy (181 cases). In clinical practice, the infections have mostly been misdiagnosed as a neoplasia, usually benign but sometimes malignant. Under the assumption of an intraorbital tumor, the endoscopic transnasal revision of the orbital cavity was performed, as this approach promised to be least traumatic and best suited for the lesion, resulting in complete removal of the live worm. In unclear lesions in the head and neck, and infection with Dirofilaria repens should be considered as a differential diagnosis.

Application of pharmacokinetics to electron-beam tomography of the abdomen

RATIONALE AND OBJECTIVES

The purpose of this study was to evaluate the pharmacokinetics of abdominal time-attenuation curves obtained at electron-beam tomography.

MATERIALS AND METHODS

Computed tomographic enhancement data of the aorta, portal vein, vena cava, liver, spleen, and pancreas were obtained in 25 patients after injection of 50 mL of contrast medium. These data were used to calculate pharmacokinetic parameters such as half-lives, mean residence times, and areas under the curve with a computer program.

RESULTS

Maximal enhancement was observed in the aorta 24 seconds +/- 5 (mean +/- standard deviation) after starting the injection of contrast medium (178 HU +/- 56), in the portal vein after 42 seconds +/- 14 (60 HU +/- 17), in the vena cava after 35 seconds +/- 7 (66 HU +/- 23), in the liver after 58 seconds +/- 15 (24 HU +/- 6), in the spleen after 35 seconds +/- 12 (42 HU +/- 16), and in the pancreas after 39 seconds +/- 15 (42 HU +/- 10). Half-lives of the last phase observed were 108 seconds +/- 123 in the aorta, 33 seconds +/- 30 in the portal vein, 49 seconds +/- 40 in the vena cava, 50 seconds +/- 54 in the liver, 62 seconds +/- 33 in the spleen, and 22 seconds +/- 27 in the pancreas. The computer program allowed for excellent fitting curves to the measured attenuation values and for subsequent calculation of pharmacokinetic parameters. New dosage regimens also could be simulated successfully.

CONCLUSION

The pharmacokinetic parameters evaluated might be useful in the optimization of dosing and scanning parameters of the abdomen for ultrafast and helical CT.

Echo-enhanced Doppler sonography of focal nodular hyperplasia of the liver

Lesions of focal nodular hyperplasia are hypervascular, benign focal liver lesions whose differentiation from other focal liver lesions is of significant clinical relevance. The purpose of this study was to investigate the echo-enhancing agent SHU 508A (Levovist) in the evaluation of focal nodular hyperplasia with Doppler sonography. We examined 49 patients with 71 lesions of focal nodular hyperplasia in the liver with gray scale and power Doppler sonography. In all patients Levovist was administered intravenously in a concentration of 300 to 400 mg galactose per milliliter. Visualization of the feeding vessels and the vascularity of the lesions were evaluated, and the resistive indices in the feeders and the hepatic arteries were assessed. In comparison with unenhanced power Doppler sonography, echo-enhanced power Doppler sonography yields a higher sensitivity in the detection of the feeding artery (97% versus 82%) in focal nodular hyperplasia and in the depiction of the radial vascular architecture in such lesions, especially those located in the left lobe of the liver. Lesions less than 3 cm in diameter do not consistently show a characteristic vascular architecture with echo-enhanced Doppler sonography. The resistive index of the tumor-feeding artery (mean, 0.51 +/- 0.09) is significantly (P < 0.0001) lower than that of the hepatic artery (mean, 0.65 +/- 0.06) and decreases as the size of the focal nodular hyperplasia increases. The administration of Levovist may improve the signal-to-noise ratio and thus visualization of the vascular architecture in focal nodular hyperplasia. Lesions located in the left lobe of the liver, which commonly are subject to disturbing motion artifacts in color Doppler sonography, will significantly benefit from the administration of Levovist. Echo-enhanced power Doppler sonography, however, is not capable of depicting a characteristic vascular pattern in small (< or = 3 cm) lesions of focal nodular hyperplasia that would guarantee a specific diagnosis.

Sonographic evaluation of focal nodular hyperplasias (FNH) of the liver with a transpulmonary galactose-based contrast agent (Levovist)

Focal nodular hyperplasias (FNH) are hypervascular, benign focal liver lesions. Differentiation of FNH from other focal liver lesions is of clinical importance. The purpose of this study was to examine the impact of a new, transpulmonary echo-enhancing agent SHU 508A (Levovist) and recent Doppler techniques in the sonographic evaluation of FNH. 43 patients with 61 focal nodular hyperplasias of the liver were examined with grey scale ultrasound and power Doppler ultrasound. Levovist, a galactose-air-microbubble suspension was administered intravenously in all patients, either by bolus injection (400 mg ml-1) or continuous pump-infusion (300 mg ml-1). Visualization of the feeding vessels and vascularity of the lesions were evaluated. The resistance indexes (RI) in the feeding vessel and the hepatic artery were assessed and compared with the diameters of the FNH. The mean diameter of FNH was 4.3 cm (+/- 1.0). Echo enhanced power Doppler ultrasound was superior to unenhanced power Doppler ultrasound in the detection of the feeding artery (85% vs. 98%) in FNH and depicted the internal vascular architecture more clearly, especially in lesions located in the left lobe of the liver. Lesions smaller than 3 cm did not show a characteristic vascular architecture with echo enhanced Doppler ultrasound. The resistance index of the feeding artery (mean: 0.51 +/- 0.08) is significantly (p < 0.0001) lower than that of the hepatic artery (mean 0.65 +/- 0.06) with a mean difference of -0.14 +/- 0.01 in the same patient. The RI of the feeding artery significantly decreased as the size of the FNH increased, whereas RI differences between the hepatic artery and the feeding artery increased with lesion size. Intravenous (i.v.) bolus injection of the contrast agent will depict the hypervascular nature of FNH more clearly than i.v. infusion, although the latter will significantly prolong the diagnostic window. In conclusion, i.v. infusion of Levovist improves the visualization of the feeding artery and the radiating vascular architecture in FNH located in the left lobe of the liver due to improved signal-to-noise ratio and results in more effective suppression of motion artefacts. Although echo enhanced Doppler ultrasound improves the detection of the low resistance arterial feeding vessel in small FNH, it will not, however, reveal a specific vascular pattern in these lesions.

Topographic evaluation of lateral hypopharyngeal pouches using electron beam tomography

BACKGROUND

To evaluate the exact topography of lateral hypopharyngeal pouches using electron beam tomography.

METHODS

Seventeen patients, nine female, eight male, aged 28-72 years, who showed lateral hypopharyngeal pouches in the videofluorographic swallowing examination were studied using electron beam tomography. Upon swallowing a 20-ml bolus of water, the region of the thyrohyoid membrane was scanned 20 times per level. Scan parameters: single slice cine mode (exposure time 100 ms, slice thickness 3 mm, 620 mA, 130 KV).

RESULTS

The lateral hypopharyngeal pouches appeared air-filled in the posterior aspect of the thyrohyoid membrane closely attached to the upper horn of the thyroid cartilage, just below the hyoid bone.

CONCLUSIONS

With electron beam tomography it was possible to define the topographic location of the pouches more accurately, compared with the prior assumption of position.

Power Doppler imaging and evaluation of the resistive index in focal nodular hyperplasia of the liver

Focal lesions of the liver represent a significant diagnostic problem for various imaging modalities. The aim of this study was to assess the value of power Doppler sonography versus conventional color Doppler imaging in the depiction of hypervascular focal nodular hyperplasia (FNH) of the liver and to investigate the resistive index (RI) in the lesions' feeding arteries. Eighteen histologically proved FNHs in 14 patients were evaluated by gray-scale ultrasound, conventional color Doppler, and power Doppler sonography. With conventional color Doppler, a feeding arterial vessel could be depicted in only 4/18 lesions and hypervascularization was detected in 6/18 lesions. Power Doppler was more sensitive in detecting feeding arteries (16/18) within hypervascular lesions (15/18). RI values in the feeding arteries (mean = 0.51) significantly differed from those in the main hepatic artery or its intraparenchymal branches (mean = 0.68) in the same patient. The mean RI-difference was 0.19, suggesting hemodynamically significant arteriovenous shunting. Power Doppler sonography significantly increases sensitivity in the diagnosis of focal nodular hyperplasia of the liver and reliably permits the distinction of these lesions from hepatocellular carcinomas.

Sonography of acute cholecystitis: comparison of color and power Doppler sonography in detecting a hypervascularized gallbladder wall

OBJECTIVE

We evaluated the sensitivity and specificity of power Doppler sonography compared with conventional color Doppler sonography and gray-scale sonography in diagnosing patients with acute cholecystitis.

SUBJECTS AND METHODS

Seventy-six patients with right upper quadrant pain and 72 healthy volunteers underwent gray-scale sonography, conventional color Doppler sonography, and power Doppler sonography of the gallbladder. The vascularity of the gallbladder wall was scored on a scale of 0 to +3. Histology revealed acute cholecystitis in 55 patients. Histologic specimens and clinical workups showed that the remaining 21 patients suffered from other diseases.

RESULTS

Sensitive sonographic features such as the positive Murphy's sign (in 96% of patients with acute cholecystitis), calculi (95%), and a thickened gallbladder wall (73%) lacked specificity (71%, 38%, 67%, respectively) for diagnosing acute cholecystitis. In our study, the sensitivity of power Doppler sonography was 95% compared with 33% for color Doppler sonography in revealing a hypervascularized gallbladder wall. Power Doppler sonography revealed hyperemia within a nonthickened gallbladder wall in four patients with surgically proven acute cholecystitis. Specificity of power Doppler sonography was 86% compared with 95% for conventional color Doppler sonography. False-positive results with power Doppler sonography were caused by pancreatitis, duodenal ulcer, and gallbladder carcinoma. Interobserver variability seemed to play no significant role. No intramural hypervascularity was detected in the volunteer group. In four (4%) of 89 symptomatic patients we could not use power Doppler sonography because of the patients noncompliance. Mean values of the resistive index assessed within intramural vessels of the gallbladder showed no significant differences (p < .001) between patients with acute cholecystitis (0.73) and patients with other diseases (0.71).

CONCLUSIONS

Although the sensitivity of power Doppler sonography in diagnosing acute cholecystitis was similar to that of gray-scale sonography, the specificity of power Doppler sonography was significantly higher, which may substantially improve diagnostic confidence. However, the high susceptibility of power Doppler sonography to motion artifacts makes appropriate adjustment of technical parameters much more relevant than with other sonographic imaging. The resistive index within intramural vessels has no clinical use in the diagnosis of acute cholecystitis.

[Functional studies of swallowing with electron beam computerized tomography]

Functional evaluation of swallowing disorders requires rapid imaging modalities. Videofluorography and cinematography are the gold standard, but they have their limitations: no transverse plane imaging is achieved and structural resolution for exact topographic analysis is limited. Three cases preselected by videofluorography were studied to evaluate whether electron beam tomography (EBT) permits more detailed dynamic imaging of swallowing disorders focusing on the mesonasopharyngeal segment, the hypopharynx and the upper esophageal sphincter (UES). Immediately after videofluorographic examination of the oropharyngeal deglutition, EBT is performed. The patient is in a supine position and while the patient swallows a 20 ml bolus of water or diluted iodine containing contrast agent, a sequence of 20 images per level is scanned. The levels, which are determined by using the scout view, are oriented parallel to the hard palate either at the level of the hard palate to image the mesonasopharyngeal segment or just above the hyoid bone to focus on the hypopharynx or at the location of the UES. The scan technique is a single-slice cinemode with a slice thickness of 3 mm (exposure time 100 ms, interscan delay 16 ms, 130 kV, 620 mA). The following structural interactions that we have so far been unable to image can be clearly demonstrated with EBT: (1) during normal swallowing, the mesonasopharyngeal segment is completely and symmetrically closed by the soft palate and Passavant's cushion; (2) lateral hypopharyngeal pouches can be located more precisely; and (3) disorders of the UES can be differentiated into functional or morphologically caused disorders (e.g., goiter or cervical osetophytes). Videofluorography and cinematography are still the gold standard in functional evaluation of swallowing disorders. However, EBT permits dynamic imaging of pharyngeal deglutition in a preselected transverse plane and can give useful additional information concerning functional anatomical changes in the pharynx during swallowing. Further clinical evaluation is needed.