Evaluation of Strain Elastography for Differentiation of Thyroid Nodules: Results of a Prospective DEGUM Multicenter Study.

PURPOSE: Many patients with thyroid nodules are presently referred to surgery for not only therapeutic but also diagnostic purposes. The aim of noninvasive diagnostic methods is to optimize the selection of patients for surgery. Strain elastography (SE) enables the ultrasound-based determination of tissue elasticity. The aim of the present study was to evaluate the value of SE for the differentiation of thyroid nodules in a prospective multicenter study. MATERIALS AND METHODS: The study was registered at clinicaltrials.gov and was approved by the local ethics committees of all participating centers. All patients received an ultrasound (US) of the thyroid gland including color Doppler US. In addition, all nodules were evaluated by SE (Hitachi Medical Systems) using qualitative image interpretation of color distribution (SE-ES), strain value and strain ratio. RESULTS: Overall, 602 patients with 657 thyroid nodules (567 benign, 90 malignant) from 7 centers were included in the final analysis. The sensitivity, specificity, NPV, PPV, +LR were 21 %, 73 %, 86 %, 11 %, 0.8, respectively, for color Doppler US; 69 %, 75 %, 94 %, 30 %, 2.9, respectively, for SE-ES; 56 %, 81 %, 92 %, 32 %, 2.9, respectively, for SE-strain value; and 58 %, 78 %, 92 %, 30 %, 2.6, respectively, for SE-strain ratio. The diagnostic accuracy was 71 % for both strain value and strain ratio of nodules. CONCLUSION: SE as an additional ultrasound tool improves the value of ultrasound for the work-up of thyroid nodules. It might reduce diagnostic surgery of thyroid nodules in the future.

Importance of Abdominal Ultrasound in 17 Patients with Histologically Confirmed Autoimmune Pancreatitis (AIP).

PURPOSE: Autoimmune pancreatitis (AIP) is an independent, underdiagnosed, rare form of chronic pancreatitis. The goal of this study is to document ultrasound findings in histologically confirmed AIP in order to determine the diagnostic value of ultrasound. MATERIALS AND METHODS: 6 of 74 DEGUM instructors for internal medicine (level 3 and 2) provided anonymized clinical and sonographic data from 17 patients with histologically confirmed AIP. RESULTS: 9/17 patients had diffuse AIP, 8/17 had focal AIP, 14/17 suffered from upper abdominal pain, 9/17 had jaundice, and 3/9 had an elevated IgG4 level. Ultrasound showed diffuse hypoechoic organ enlargement in 9/17 cases and a hypoechoic tumor with an unclear border in 8/17 cases. AIP was verified by ultrasound-guided percutaneous core biopsy in 14 cases, by biopsy of the bile duct in 1 case, and by surgical biopsy in 2 cases. Involvement of the hepatobiliary system was present in 7/17 patients and autoimmune cholangitis was verified in 5 cases. All patients experienced remission after immunosuppressive treatment. The pancreatic duct had a normal width in 11 cases, was dilated in 5 cases, and was stenosed over a long stretch in 3 cases. Contrast-enhanced ultrasound did not show uniform signal increase but also no significantly reduced or absent perfusion. CONCLUSION: Ultrasound can be diagnostically useful if the clinical manifestations of AIP are known. While the diffuse form allows an ad-hoc suspected diagnosis, the focal form can only be suspected in the case of additional extrapancreatic involvement. Contrast-enhanced ultrasound (CEUS) contributes greatly to the differentiation from ductal adenocarcinoma in the case of focal AIP.

Incidence of bleeding in 8172 percutaneous ultrasound-guided intraabdominal diagnostic and therapeutic interventions - results of the prospective multicenter DEGUM interventional ultrasound study (PIUS study).

PURPOSE: To analyse the incidence of bleeding after percutaneous ultrasound guided diagnostic and therapeutic intraabdominal interventions in a prospective multicentre study (DEGUM percutaneous interventional ultrasound study). MATERIALS AND METHODS: Within a time period of 2 years diagnostic and therapeutic intraabdominal interventions (with the exclusion of ascites paracentesis) performed percutaneously under continuous ultrasound (US) guidance were prospectively assessed using a pseudonymized standardized web site entry form. Number and type of intervention, operator experience, patient characteristics, medication, lab data as well as technical aspects of the procedure and bleeding complications were analysed according to the interventional radiology standards. RESULTS: 8172 US-guided intraabdominal interventions (liver n = 5903; pancreas n = 501, kidney n = 434, lymph node = 272, biliary system n = 153, spleen n = 63, other abdominal organs and extra-organic targets n = 999) were analysed in 30 hospitals. The majority were diagnostic biopsies including 1780 liver parenchyma, 3400 focal liver lesions and 404 pancreatic lesions. 7525 interventions (92.1 %) were performed in hospitalized patients (mean age 62.6 years). Most operators were highly experienced in US-guided interventions (> 500 interventions prior to the study n = 5729; 70.1 %). Sedation was administered in 1131 patients (13.8 %). Needle diameter was ≥ 1 mm in 7162 punctures (87.9 %) with main focus on core needle biopsies (18 G, n = 4185). Clinically relevant bleeding complications with need of transfusion (0.4 %), surgical bleeding control (0.1 %) and radiological coiling (0.05 %) were very rare. Bleeding complications with fatal outcome occurred in four patients (0.05 %). The frequency of major bleeding complications was significantly higher in patients with an INR > 1.5 (p < 0.001) and patients taking a medication potentially interfering with platelet function or plasmatic coagulation (p < 0.0333). CONCLUSION: This prospective multicentre study confirms the broad spectrum of percutaneous US-guided intraabdominal interventions. However diagnostic liver biopsies dominate with the use of core needle biopsies (18 G). Percutaneous US-guided interventions performed by experienced sonographers are associated with a low bleeding risk. Major bleeding complications are very rare. A pre-interventional INR < 1.5 and individual medication risk assessment are recommended.

Endocavitary contrast enhanced ultrasound (CEUS)--work in progress.

PURPOSE: To demonstrate the benefit concerning localisation, measurement and visualisation of complications of drained fluid collections in the abdomen by applying ultrasound contrast agent via drainage catheters. In addition, to investigate the usefulness of CEUS in applying the agents in the biliary tract or when given orally. MATERIALS AND METHODS: A single drop of SonoVue® was added to 0.9 % saline solution and instilled via drainage catheters. Location, dimensions and complications of drained fluid collections were recorded and compared to the results of sonographic examination using saline solution alone and fluoroscopic examination using iodinated contrast agents. The biliary system was visualised by applying the solution via nasobiliary drains or via ERC catheterisation. Orally administered solutions consisted of one drop of SonoVue® in 50 ml aqua. RESULTS: Admixture of an ultrasound contrast agent to saline solution facilitates position monitoring of the drains in fluid collections and provides reliable information on the dimensions of the drained collection. Complications like fistulae to the biliary system, blood vessels, small or large intestine or to the peritoneal cavity are precisely displayed. The biliary system is shown in detailed description. Orally administered, the contrast agent is visible after intake long unto the colon. Insufficient anastomoses or spontaneous perforations become detectable. CONCLUSION: The application of ultrasound contrast agents via drainage catheters provides substantial information on location and dimensions of drained fluid collections and their communication with surrounding organ structures. The biliary system can be visualised. Oral administration is feasible and provides important additional information.

Frequency of tumor entities among liver tumors of unclear etiology initially detected by sonography in the noncirrhotic or cirrhotic livers of 1349 patients. Results of the DEGUM multicenter study.

AIM: Investigation of the frequency of various solid focal liver lesions (SFLL) in noncirrhotic and cirrhotic livers with focus on the frequency of metastasis in cirrhotic livers. MATERIAL AND METHODS: The patient collective in the DEGUM multicenter study (n = 1349) was reevaluated and divided in subcollective A without (n = 1067) and B with cirrhosis (n = 282). 74.6 % of the various tumor entities were confirmed histologically (n = 1006). RESULTS: In subcollective A there were 385 patients with metastases (36.4 %) and 65 with HCC (6.1 %), whereas the most common benign lesions were hemangioma, with 237 cases (22.4 %) and FNH, with 170 cases (16.1 %). In subcollective B there were 216 cases of HCC (76.6 %) and 12 metastases (4.3 %), as well as 42 benign lesions (14.9 %). CCC was rare in both subcollective A (3.3 %) and subcollective B (2.5 %). A positive oncological history increased the probability of a malignant SFLL in subcollective A by 1.8 times, but did not do so in subcollective B. CONCLUSION: The frequency of various tumor entities is different in patients with and without cirrhosis of the liver. In noncirrhotic livers, malignant and benign SFLL are equally common. The most common forms are metastases, hemangiomas and FNH, CCC is rare. A positive history of extrahepatic malignancy increases the probability of a malignant SFLL. In cirrhosis, HCC dominates, HCC is 18 times as common as metastases. Benign SFLL and CCC are rare.

Diagnostic accuracy of CEUS in the differential diagnosis of small (≤ 20  mm) and subcentimetric (≤ 10  mm) focal liver lesions in comparison with histology. Results of the DEGUM multicenter trial.

PURPOSE: To evaluate the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) in the differential diagnosis of small and subcentimetric liver tumors in clinical practice. MATERIALS AND METHODS: 1349 patients with a hepatic tumor lacking a definite diagnosis based on B-mode ultrasound and power Doppler ultrasound were examined at 14 hospitals by CEUS using a standardized protocol (pulse/phase inversion imaging, mechanical index < 0.4). Differential diagnosis was based on the vascularity pattern and contrast enhancement pattern during the arterial, portal, and late phase according to the EFSUMB guidelines. 335 patients with focal liver lesions (FLL) ≤ 20  mm were analyzed. The tumor status established after CEUS was compared to histology (73.2 %) or in some cases to CT or MRI. RESULTS: A definitive diagnosis based on the gold standard was possible in 329 FLLs, while 6 FLLs remained unclear even in the combined gold standard (histology and/or CT and/or MRI). The final diagnoses of ≤ 20  mm FLL with histological confirmation (n = 241) included 87 benign and 154 malignant entities. The overall diagnostic accuracy of CEUS in FLL ≤ 20  mm with histological confirmation was 83.8 %. CEUS correctly identified 144 /154 malignant FLLs (sensitivity 93.5 %) and 58 /87 benign FLLs (specificity 66.7 %). 24 /241 FLLs remained unclear after CEUS (9.9 %). CEUS misclassified 15 /241 FLLs (6.2 %; 12 benign and 3 malignant FLLs). The positive predictive value of CEUS for a malignant FLL was 92.3 % and the negative predictive value was 95.1 %. Out of 241 small FLLs with histological confirmation, 62  FLLs were ≤ 10  mm (diagnostic accuracy of CEUS 80.6 %) and 179 FLLs were > 10  mm and ≤ 20  mm (diagnostic accuracy of CEUS 84.9 %). CONCLUSION: CEUS has a high diagnostic accuracy for the differential diagnosis of small and subcentimetric FLLs in clinical practice.

Unclear focal liver lesions in contrast-enhanced ultrasonography--lessons to be learned from the DEGUM multicenter study for the characterization of liver tumors.

PURPOSE: To discuss the difficulties of contrast-enhanced ultrasound (CEUS) in a large multi-center trial. MATERIALS AND METHODS: CEUS was performed on 1349 liver lesions with an unclear diagnosis after native ultrasound using a standardized protocol (phase inversion; low MI < 0.4; Sonovue Bolus 1.2 - 4.8 ml). The early arterial, arterial, portal venous and late phase > 2 min. were documented. The diagnosis based on CEUS results was compared to the final diagnosis (histology: n = 1006; MRI: n = 269; CT: n = 269 - multiple examinations possible). RESULTS: Of the 1349 enclosed liver lesions, 20 could not be definitively diagnosed even using all diagnostic steps including histology (the others were proven to be benign n = 573 or malignant n = 756). Of the 1349 unclear liver lesions, 1257 could be differentiated with an accuracy of 90.3% using CEUS. The sensitivity, specificity, and positive and negative predictive value for malignant liver lesions was 95.8%, 83.1%, 88.2% and 93.7% respectively. 92 liver lesions (6.8%) could not be definitively diagnosed using CEUS. Most of them were benign (n = 67) on final diagnosis. The CEUS diagnosis was wrong for 39 lesions. However, only 8 lesions classified as benign by CEUS turned out to be malignant. In 3 cases HCC proven by histology was incorrectly diagnosed by CEUS as adenoma and 2 lesions incorrectly diagnosed by CEUS as FNH turned out to be an HCC and a metastasis. Two lesions diagnosed by CEUS as hemangiomas turned out to be an HCC and a metastasis. One lesion classified as benign by CEUS was ultimately diagnosed as a lymphoma. CONCLUSION: Even in this multi-center trial, CEUS proved to be an excellent method for clarifying liver lesions remaining unclear after native ultrasound. The CEUS diagnosis of benign was only incorrect in a few cases.

Contrast-enhanced ultrasound (CEUS) for the characterization of focal liver lesions in clinical practice (DEGUM Multicenter Trial): CEUS vs. MRI--a prospective comparison in 269 patients.

PURPOSE: The aim of this prospective multicenter study was to assess the diagnostic role of CEUS in the diagnosis of newly discovered focal liver lesions in clinical practice. One important aspect is the comparison of CEUS with magnetic resonance imaging (MRI). MATERIALS AND METHODS: From 05 / 2004 to 12 / 2006, standardized CEUS was performed prospectively on 1349 patients with focal liver lesions that had been newly detected by fundamental ultrasound in order to determine tumor differentiation and tumor entity. 269 patients had a standardized MRI after CEUS. In typical liver hemangioma and focal nodular hyperplasia (FNH), the definitive diagnosis was based on the MRI as the "diagnostic gold standard" and on clinical evidence and additional follow-up (subgroup A) or on histology (subgroup B). 262 patients met the diagnostic standard that had been set. RESULTS: In the subcollective (n = 262), the tumor differentiation (malignant or benign) of CEUS and MRI was concordant in 225 cases (85.9%), and the assessment of tumor entity in 204 cases (77.9%). In subgroup A (n = 180), concordant results for tumor differentiation were obtained in 169 (93.2%) and for tumor entity in 160 (88.9%) cases. Liver hemangiomas (n = 122) and FNH (n = 43) were most frequent. Subgroup B (n = 82) comprised mainly malignant liver lesions (n = 55), with only a few of hemangiomas (n = 8) or FNH (n = 5). Tumor differentiation was concordant in 56 (68.3%) and tumor entity in 44 cases (53.7%). There were no statistically proven differences between CEUS and MRI. CONCLUSION: CEUS and MRI are of equal value for the differentiation and specification of newly discovered liver tumors in clinical practice. CEUS and MRI are extremely reliable for the differentiation of benign and malignant lesions, the diagnosis of liver hemangiomas and FNH. The characterization of metastases and HCC is also very reliable.

Tumor-specific vascularization pattern of liver metastasis, hepatocellular carcinoma, hemangioma and focal nodular hyperplasia in the differential diagnosis of 1,349 liver lesions in contrast-enhanced ultrasound (CEUS).

AIM: To evaluate the incidence and diagnostic accuracy of tumor-specific vascularization pattern in contrast-enhanced ultrasound (CEUS) in the differential diagnosis of liver tumors in clinical practice. MATERIALS AND METHODS: From May 2004 to December 2006 1349 patients (male 677, female 672) with a hepatic tumor lacking a definite diagnosis based on B-mode ultrasound and power Doppler ultrasound were examined at 14 hospitals by CEUS using a standardized protocol (pulse/phase inversion imaging, mechanical index < 0.4). Vascularity pattern and contrast enhancement pattern were analyzed in focal lesions during the arterial, portal, and late phase. The tumor-specific diagnosis established after CEUS was compared to histology (> 75 % cases) or in some cases to CT or MRI. RESULTS: The final diagnosis of 573 benign hepatic tumors included hemangiomas (n = 242) and focal nodular hyperplasia (n = 170), other benign lesions (n = 161). Tumor-specific vascularization pattern such as a wheel-spoke pattern and arterial hyperenhancement followed by isoenhancement in the late phase in FNH or a nodular peripheral enhancement and partial or complete fill-in pattern in hemangiomas could be assessed in the majority, but not all lesions. The diagnostic accuracy of CEUS was 83.1 % for all benign lesions and 82.2 % for hemangioma and 87.1 % for FNH. The final diagnosis of 755 malignant hepatic tumors included metastases n = 383, hepatocellular carcinoma n = 279 and other malignant lesions n = 93. Late phase hypoenhancement was seen in almost all liver metastases (94.7 %) The diagnostic accuracy of CEUS was 95.8 % for all malignant lesions and 91.4 % for liver metastases and 84.9 % for hepatocellular carcinomas. CONCLUSION: Tumor-specific vascularization pattern in CEUS have a high diagnostic impact on the overall high diagnostic accuracy of CEUS for the differential diagnosis of hepatic tumors in clinical practice.

Contrast-Enhanced Ultrasound (CEUS) for the characterization of focal liver lesions - prospective comparison in clinical practice: CEUS vs. CT (DEGUM multicenter trial). Parts of this manuscript were presented at the Ultrasound Dreiländertreffen 2008, Davos.

AIM: The aim of our study was to evaluate the diagnostic value of Contrast-Enhanced Ultrasound (CEUS) for the characterization of focal liver lesions in a prospective multi-center study in clinical practice. For this purpose CEUS was compared with the spiral-CT (SCT), the standard radiological method. MATERIAL AND METHODS: 1349 patients with unclear liver lesions after fundamental ultrasound diagnostics including color doppler analysis were examined with standardized CEUS (pulse inversion method, mechanical index < 0.4) from May 2004 to December 2006 in 14 hospitals in a prospective study. The enhancement of contrast medium in the liver tumors was analyzed according to known tumor-specific vascular patterns, using standardized documentation and analysis methods for the differentiation of tumor differentiation (malign or benign) and tumor specification (entity). A subcollective of 267 patients was additionally examined by standardized SCT method. Final diagnosis was based on histology, SCT or MRI in typical findings of liver hemangioma and FNH and on proved clinical data and additional follow up. RESULTS: The subcollective of 267 patients was divided in two subgroups. In 109 of these patients (subgroup A) there was no histological verification, diagnoses based on clear SCT-findings in 79 cases of hemangioma or FNH, as well as in 20 cases with a clear clinical diagnosis. 6 cases (5.5 %) remained unclear. In this subgroup the assessment of tumor differentiation was concordant with CEUS in 90 cases, discordant in 19 cases and the assessment of tumor specification was concordant in 82 and and discordant in 27 cases. In 158 patients (subgroup B) a histological finding was also present, only in 4 cases no definitive tumor diagnosis was achieved. In this subgroup assessment of tumor differentiation with CEUS and SCT was concordant in 124 cases and discordant in 30 cases (CEUS/SCT: sensitivity 94.0 / 90.7 %, specificity 83.0 / 81.5 %, PPV 91.6 / 91.5 %, NPV 87.5 / 80.0 %, accuracy 90.3 / 87.8 %). Tumor specification matched in 103cases and were different in 51 cases (CEUS/SCT: sensitivity 95.3 / 90.6 %, specificity 83.7 / 81.6 %, PPV 92.7 / 91.4 %, NPV 89.1 / 80.0 %, accuracy 91.6 / 87.7 %). A statistically significant difference could not be established. The analysis of particular tumor specification showed a statistically non significant slight advantage in tumor differentiation for CEUS in the case of hemangioma, FNH, HCC and metastases. CONCLUSION: In a multi-center approach under routine clinical conditions, this prospective study demonstrates CEUS to be of equal rank to the CT-scan in regard to the assessment of tumor differentiation and specification. No statistically significant differences could be established. CEUS should be employed before computed tomography is performed for the differentiation of liver tumors, because radiation exposure and invasive biopsies can be avoided in veritable numbers of cases, when precise clinical evaluation of the findings is implemented.

Changes in cortical subarachnoid fluid potassium concentrations during hypoxia.

Seventeen rhesus monkeys underwent 20-minute episodes of hypoxia (mean Po2, 18 to 28 mm Hg). In 14 animals that maintained mean blood pressures greater than 60 mm Hg, increases in potassium concentration averaging greater than 1 mEq/liter were observed in the cortical subarachnoid fluid. These changes were reversible with oxygen administration and were usually not associated with morphologic evidence of brain injury. Cisterna magna fluid, sampled in five animals, showed smaller increases in potassium concentration (mean, 0.3 +/- 0.4 mEq/liter). The arteriovenous difference in potassium concentration was consistently positive, suggesting movement of potassium from blood to brain during hypoxia. The amount of potassium accumulation in the cortical subarachnoid fluid was closely related to the severity of the hypoxia. Threshold Po2 levels, below which potassium changes occurred, were estimated at 29 mm Hg for the arterial blood and 20 mm Hg for the jugular venous blood. Massive potassium accumulations in the cortical subarachnoid fluid (greater than 10 mEq/liter) developed in three animals that sustained severe arterial hypotension during hypoxia.

Brain extracellular potassium activity during hypoxia in the cat.

Brain extracellular potassium activity, recorded by a potassium-selective microelectrode technique, was studied in 27 anesthetized, paralyzed cats during hypoxia. Potassium activity remained essentially constant until the arterial pO2 decreased to 20 to 23 mm Hg. If the blood pressure was allowed to decrease during hypoxia, even to the 70 to 100 mm Hg range, the associated increases in potassium activity were accentuated, often to levels greater than 20 mEq per liter. The electrocorticogram regularly became isoelectric by the time the potassium activity reached 6 to 10 mEq per liter. Elevations of the blood pressure with epinephrine injections reversed both the increases in potassium activity and the electrocorticogram flattening. Extracellular potassium homeostasis during hypoxia appears to depend on the maintenance of a normal arterial perfusion pressure.

Changed composition of high-density lipoprotein subclasses HDL2 and HDL3 after renal transplantation.

The concentrations of cholesterol in the high density lipoprotein (HDL) fraction and the HDL2 and HDL3 subclasses were compared in 333 male renal transplant recipients, 36 male patients on maintenance hemodialysis, and 43 healthy men. The subclasses were separated by a precipitation method using polyethylene glycol 6000 and dextran sulphate. In hemodialyzed patients, total HDL cholesterol and both subclasses were reduced. In renal transplant recipients, both total HDL cholesterol and HDL2 were normal, whereas HDL3 remained reduced, analogous to hemodialyzed patients. It can be concluded that a successful renal transplantation has a beneficial effect on HDL metabolism and thus on the development of atherosclerosis.

The kinetics of extracellular potassium changes during hypoxia and anoxia in the cat cerebral cortex.

Extracellular potassium activity, [K+]0, was continuously measured using potassium specific microelectrodes in the cerebral cortex of cats before and after hypoxic or anoxic insults. Two patterns of [K+]0 increase were seen. A slow, linear rise occurred during hypoxia and hypothermia and was correlated with changes in mean blood pressure (B/P). A fast, complex, exponential rise resembling spreading depression occurred during anoxia and was unassociated with B/P changes. The fall of [K+]0 after reversal of the insult was described by a single exponential function with rate constants from 0.009 to 0.0194 sec-1. It is suggested that the linear rise is primarily a result of sodium pump inhibition and that the exponential rise is due to a superimposed sudden increase in cell membrane permeability perhaps secondary to transmitter release. The kinetics of the fall of [K+[0 is consistent with the normalization of the sodium and potassium gradients across the cell membranes secondary to Na+-K+ATPase activity.

Studies with antisera against peripheral nervous system myelin and myelin basic proteins. I. Effects of antiserum upon living cultures of nervous tissue.

We studied the effects of antiserum against rat peripheral nervous system (PNS) myelin, rat or chicken central nervous system myelin basic protein (BP), or rabbit P2 protein from PNS myelin on myelinated cultures containing only rat dorsal root ganglion neurons and Schwann cells. While anti-PNS myelin serum consistently produced segmental PNS demyelination, anti-BP serum and anti-P2 serum did not. The culture results suggest that the myelin PNS proteins P1 (identical to basic protein from central nervous system myelin) and P2 are not exposed on the extracellular surfaces of myelin-related Schwann cells in tissue culture.

Enhanced penetration of zona-free hamster ova by sperm prepared by Nycodenz and Percoll gradient centrifugation.

The effect of sperm penetration capacity after selection procedures using Percoll (Pharmacia AB, Uppsala, Sweden) and Nycodenz (Nycomed Diagnostics, Oslo, Norway) gradient centrifugation was compared with double-washed and swim-up in 47 subfertile men. The results of sperm motility, velocity, and amplitude lateral head displacement showed no significant improvement with the centrifugation procedures. The sperm penetration assay results obtained with double-washed and swim-up technique were poor (2.7% +/- 1.7%), however, a significant enhancement was obtained by Percoll (16.3% +/- 3.7%) and Nycodenz (15.8% +/- 3.3%) processing. Nycodenz centrifugation allowed sperm penetration of zona-free hamster ova at comparable rates to Percoll separation.

Measuring and developing suturing technique with a virtual reality surgical simulator.

BACKGROUND: We have developed an interactive virtual reality (VR) surgical simulator for the training and assessment of suturing technique. The surgical simulator is comprised of surgical tools with force feedback, a 3-dimensional graphics visual display of the simulated surgical field, physics-based computer simulations of the tissues and tools, and software to measure and evaluate the trainee's performance. STUDY DESIGN: This study uses the simulator to measure and compare the skills of 8 experienced vascular surgeons versus 12 medical students when performing a virtual reality suturing task. Eight parameters of the suturing task were measured: total tissue damage, accuracy of needle puncture, peak tissue tearing force, time to complete the task, damage to the surface of the tissue, angular error in needle technique, total distance traveled by the tool tip, and a measure of overall error. Three test conditions (dominant hand, nondominant hand, and 3-dimensional needle guide) were tested. Statistical significance was defined as a univariate two-sided p value < or = 0.05. RESULTS: The surgeons' average performance was significantly better than the students' average performance for three of the measured parameters (total tissue damage, time to complete the task, and total distance traveled by the tool tip) for each of the test conditions. For the test condition most similar to surgery (using the dominant hand to suture) one additional parameter was also significantly different (the measure of overall error). The medical students showed improvements for 6 of the 7 parameters for which the users received feedback during the training process. The surgeons also had significant improvement for 4 of the 7 parameters. The students had a larger improvement than the surgeons for 6 of the parameters, but these differences were not statistically significant. CONCLUSIONS: Data indicate differences between surgeon and nonsurgeon performance and in improvement in performance with training. One possible explanation for the superior performance of the surgeons is that their suturing skills applied well to the simulated suturing task. Additional research is required to confirm or deny the similarity between actual and simulated surgical tasks and the relevance of virtual reality surgical simulation to surgical skill assessment and training.

[Myelolipoma of the adrenals--a chance sonographic finding]. / Das Myelolipom der Nebenniere--ein sonographischer Zufallsbefund.

A markedly echogenic and sharply marginated suprarenal mass was found incidentally during an abdominal sonography in the case of three patients. One female patient died due to a mesenterial infarct, in the other cases the tumors were removed surgically. In two cases the histological diagnosis indicated a myelolipoma of the adrenal gland, in one case an angiolipoma attached directly to the adrenal. Myelolipoma is a benign and hormone-inactive tumorous lesion, which most commonly occurs in the adrenal gland. Knowledge of the clinical and sonomorphologic characteristics along with computed tomography helps to distinguish other tumors of the retroperitoneum. Thus, unnecessary surgical intervention can be avoided.