PubMed Health⌕ Search

Biomedical subjects

R Prokesch

Publications and source records attributed to R Prokesch.

At least 19 recordsLinked to original sources
PubMed2006

[Pancreas. Part II: Tumors].

Adenocarcinoma is the most common malignant pancreatic tumor, affecting the head in 60-70% of cases. By the time of diagnosis, approximately 80% of tumors are unresectable. Helical CT is very effective in detection and staging of adenocarcinoma, with a sensitivity of 76-92% for detection and an accuracy of 80-90% for staging, but it has limitations in the detection of small cancers (< or =2 cm). Multidetector CT (MDCT) has brought substantial improvements with its inherent 3D imaging capability. Mangafodipir-enhanced MRI is a problem-solving tool in the depiction of small cancers following an equivocal CT imaging result. Gadolinium-enhanced 3D gradient-echo MRI is helpful in the assessment of vascular invasion of cancer and in determining the etiology of cystic lesions. Serous cystadenoma is benign, has a lobulated contour and contains innumerable small cysts of 0.1-2 cm in diameter. Mucinous cystic neoplasms are unilocular or multilocular (fewer than six cysts), and the cyst diameter exceeds 2 cm. The presence of solid nodular components should alert the radiologist to suspect cystadenocarcinoma. Neuroendocrine tumors are mostly hypervascular. Diagnosis of insulinoma is a challenge: they are <2 cm in 90% of cases and mostly hypervascular at CT or MRI. A combination of contrast-enhanced MDCT, MRI, endosonography, and/or somatostatin receptor scintigraphy is used to detect these small tumors. This review summarizes the imaging features of the most common pancreatic tumors and discusses the limitations of CT, MRI and endosonography.

Adenocarcinoma↗
PubMed2002

Predictive geometric factors in a standardized model of femoral neck fracture. Experimental study of cadaveric human femurs.

An experimental study was performed on 20 cadaveric human proximal femurs to investigate both the reproducibility of their mechanical behavior under uniaxial compression and the correlation of mechanical properties with geometric dimensions and bone density. These variables were assessed by radiography, physical measurement, and dual-energy X-ray absorptiometry (DEXA). The specimens were immobilized, loaded to the point of fracture, and analyzed with the help of a materials testing machine. The fractures invariably showed a similar pattern both in location (i.e. at the femoral neck) and in nature (i.e. "axial-shear" type according to the AO classification system). The mechanical properties of the tested proximal femurs correlated negatively with age (r = -0.39) and positively with sex (male femurs were stronger and correlated more closely than female femurs, P = 0.005). They showed a strong positive correlation with head diameter (r = 0.713, P = 0.0004), a moderate positive correlation with both neck axis length (r = 0.63) and neck diameter (r = 0.502), and a slight positive correlation with femoral neck-shaft angle (r = 0.326). All DEXA-based densitometry measures turned out to be powerful predictors of fracture force. The establishment of this solidly reproducible fracture model based on standardized loading conditions should have implications for future research on osteopenia/osteoporosis and preventive stabilization techniques.

Aged↗
PubMed2002

[Pancreatic carcinoma: state of the art imaging].

In view of the bad prognosis of pancreatic carcinoma the exact pre-surgical staging is essential for curative therapy. The rapid development of multi-detector computed tomography with the clinical implementation of 16 row scanners allow for almost isotropic pixel size and high-resolution multiplanar reconstruction. Sensitivity and specificity of magnetic resonance imaging are similar to those of computed tomography with lower values in the detection of vessel wall infiltration. Ultrasound may be a valuable modality for primary diagnosis.

Contrast Media↗
PubMed2001

Femoral neck fracture after removal of the standard gamma interlocking nail: a cadaveric study to determine factors influencing the biomechanical properties of the proximal femur.

We retrospectively analyzed 1334 patients who were implanted standard gamma interlocking nails (SGN) to stabilize trochanteric femoral fractures over the years 1992-1998. Reoperation to remove the nails was performed in 37 patients, in 9 of them purely because of pain. Three out of these 9 patients with removed SGN suffered femoral neck fractures in the early postoperative course after having been mobilized to full weight-bearing capacity. This complication was not observed with other implant systems and, considering the notoriously high complication rate of femoral neck fractures, severely reduces the value of the SGN concept per se. These findings in combination with other known shortcomings of SGNs prompted us to conduct an experimental study on the fracture force of excavated femurs addressing the hypothesis that the specific design of the SGN is responsible for the occurrence of fatigue fractures of the femoral neck. Eighteen matched pairs of fresh human cadaveric proximal femurs, which were treated by insertion and removal of (i) SGNs or (ii) dynamic hip screws (DHS) or (iii) by excavation in the absence of an implant, were subjected to incremental loading cycles and compared to the untreated contralateral femurs. Overall, the fracture force was found to be significantly lower among the treated than among the untreated bones. However, the fracture force required after removal of the DHS system was still significantly higher than for SGN or excavation alone. In this way, our findings demonstrate that removing relatively big implants such as SGN can cause serious complications such as femoral neck fractures. We therefore recommend to leave this type of device in place even after fracture healing except in cases of deep and chronic infection.

Aged↗
PubMed2000

Inadvertent transpericardial insertion of a central venous line with cardiac tamponade failure of preventive practices.

A 56-year-old man who had undergone cardiac surgery suffered from cardiac tamponade after administration of contrast-medium through a central venous catheter. Pericardiotomy showed the catheter transversing the pericardial sac just beneath an unusual high reflection and then reentering the superior vena cava. Preventive practices including chest radiography, confirming free venous blood return and manometry may fail to detect catheter malposition in rare cases. Knowledge of potential pitfalls in using generally recommended safety practices and continuous vigilance are essential for the anesthesiologist and intensivist in avoiding potentially lethal hazards.

Cardiac Tamponade↗
PubMed2000

Ultrafast magnetic resonance imaging of the brain.

The purpose of this study was to compare the diagnostic efficacy of single shot fast spin echo sequence (SSh-FSE), and single shot GRASE-sequence (SSh-GRASE) to the conventional T(2)-weighted fast spin echo-sequence (T(2)-FSE) in the imaging of brain disorders. Thirty three patients with high signal intensity lesions on T(2)-weighted images (n = 28), or intracerebral hemorrhage (n = 5), were examined on a 1.0 T MR scanner, with 23 mT/m gradient strength. The scan time for the conventional T(2)-FSE-sequence was 2 min 57 s, the scan time for the single shot-FSE-, and single shot-GRASE-sequences was 11 sec, and 17 sec, respectively. Twenty-one patients remained still during the examination, whereas 12 could not stay still with consecutive marked motion artifacts. Images were reviewed by three radiologists. Lesion conspicuity, image quality, and artifacts were scored on a subjective scale. Signal-to-noise ratios of lesions and normal tissue and contrast-to-noise ratios (CNR) were measured by region of interest (ROI). In the patient group without motion artifacts conspicuity for lesions > or =5 mm did not show a significant difference on conventional T(2)-FSE, single shot-FSE and single shot-GRASE. Detectability of the smaller lesions was significantly inferior on single shot-FSE-, and single shot-GRASE-sequences in artifact free images. For the patient group with motion artifacts SSh-FSE and SSh-GRASE were markedly superior to the conventional T(2)-FSE. Grey-white differentiation was better on conventional T(2)-FSE. Physiologic ferritin as well as pathologic hemosiderin depositions were slightly darker and therefore better visible on SSh-GRASE than on SSh-FSE. Conventional T(2)-FSE showed significantly more artifacts. In conclusion, SSh-FSE and SSh-GRASE imaging can be used for rapid imaging of the brain in those patients who are claustrophobic or in patients with involuntary movements due to extrapyramidal disorders, as well as in children in whom anesthesia is contraindicated or sedation is not possible.

Adolescent↗
PubMed2000

Helical and conventional CT in the imaging of metallic foreign bodies in the orbit.

PURPOSE: To compare helical CT to conventional CT imaging in the assessment of orbital metallic foreign bodies with regard to image quality, scanning time, and radiation exposure. METHODS: Twenty-four standardized metallic foreign bodies, placed into the orbit (anterior, epibulbar, posterior) of cadaver heads were studied. Helical CT scanning in the axial plane with multiplanar reconstruction of coronal and sagittal images was performed as well as conventional CT imaging with direct scanning in the axial and the coronal planes (Tomoscan SR 7000, Philips, The Netherlands). Two masked observers consensually graded the studies using 5 predetermined criteria. Radiation dose delivered to the lens and scanning time were measured for the helical and the conventional CT imaging workup. RESULTS: Helical CT imaging scored statistically significantly better with regard to overall accuracy of foreign body localization and presence of beam-hardening streak artifacts from dental fillings. Conventional CT scored significantly better with regard to stair-step artifacts. The radiation dose delivered to the lens was 35.4 mGy for helical CT imaging and 73.9 mGy for conventional CT workup (axial and coronal scanning). Total scanning time was 18 seconds for helical CT axial scanning and 104 seconds for conventional CT axial and coronal scanning. CONCLUSION: Helical CT is superior to conventional CT imaging, because it can provide adequate information about orbital metallic foreign bodies with a single acquisition, thus reducing both the number of examinations and the radiation exposure for the patient.

Cadaver↗
PubMed1999

Fulminant lethal tuberculous pneumonia (Sepsis tuberculosis gravissima) with ARDS in a non-immunocompromised western European middle-aged man.

We report the case of a 42 years old, non-immunocompromised native Austrian living in Vienna. He presented at home with severe dyspnea and had to be intubated immediately. Shortly after hospital admission, he developed severe adult respiratory distress syndrome (ARDS) and septic shock with massive, bilobar patchy to confluent infiltrations and a need for norepinephrine. A CT-scan revealed severe loss of functional lung tissue with areas of consolidation and multiple communicating cystic spaces. Air leaking into the mediastinum through fistulas produced pneumomediastinum, pneumoperitoneum, and a massive soft tissue emphysema. Bronchoalveolar lavage performed within the first 24 hours of admission revealed + of acid-fast bacilli. Even though appropriate tuberculostatic medication was started immediately, the patient succumbed the next day to ARDS due to massive tuberculous pneumonia and miliary disease (Sepsis tuberculosis gravissima).

Adult↗
PubMed1999

[Radiologic staging of thoracic and abdominal tumors in childhood].

Thoracoabdominal tumors in childhood can arise from all organs and affect children from the neonate to the adolescent. Better prognosis of childhood tumors, due to better biological understanding and improvement of chemotherapy, require sufficient radiological staging. Sufficiency in radiological staging needs modern cross-sectional techniques with high resolution, good availability and lower radiation dose. In general computed tomography (CT) is being used for radiological staging; increasingly MR imaging is being used because of multiplanar imaging techniques. Replacement of invasive techniques such as myelography and lymphography and modern cross-sectional techniques create painless staging conditions. Nevertheless, scintigraphy will always be a major examination technique, especially for evaluation of metastases and postoperative control examinations. The most common thoracoabdominal tumors in childhood and their staging are described.

Abdomen↗
PubMed1999

[Staging of carcinomas of the upper gastrointestinal tract. The current status of diagnostic imaging].

Esophageal carcinoma: CT and endosonography are complementary and the most important imaging modalities at present for staging. After endoscopic and histological diagnosis, CT of the thorax and the abdomen is used. With the proof of local infiltration of a neighbouring organ or in the presence of distant metastasis, palliative therapy can be started. If CT is not conclusive or no local infiltration or distant metastasis is proven, endosonography should be performed. Gastric carcinoma: At present endosonography shows the highest accuracy for diagnosis of the T stage. For differentiation between T3 and T4 tumors the accuracy of CT is not sufficient to predict resectability. The N stage can be determined at present by no modality with sufficient accuracy. Distant metastasis can be diagnosed by CT with high sensitivity and specificity. Small bowel carcinoma: These rare tumors are diagnosed with high accuracy by enteroclysis, whereby the diagnosis takes place at a late stage due to the nonspecific clinical findings.

Diagnostic Imaging↗
PubMed1999

Orbital helical computed tomography in the diagnosis and management of eye trauma.

OBJECTIVE: To prospectively determine the accuracy of helical computed tomography (CT) and multiplanar reconstruction and its value in surgical planning for the management of ocular trauma with suspected intraocular and orbital foreign bodies using surgical and clinical follow-up findings as the gold standard. DESIGN: Prospective, observational case series. PARTICIPANTS: Thirty-six patients with ocular trauma and suspected foreign bodies were studied. INTERVENTION: All patients were examined using a standardized scanning protocol with helical CT direct scanning in the axial plane and multiplanar reconstruction of coronal and sagittal planes. MAIN OUTCOME MEASURES: The images were analyzed for the presence and number of intraocular and orbital foreign bodies, anatomic location, and foreign body size. The surgical and clinical follow-up findings (contact lens examination, gonioscopy, indirect ophthalmoscopy and scleral depression, perimetry, color testing, measurement of size) were used as the gold standard to which the image results were compared. RESULTS: Helical CT showed a single intraocular foreign body in 14 patients, a single orbital foreign body in 9 patients, and multiple orbital foreign bodies in 2 patients. Intraocular or orbital foreign bodies were excluded in 11 patients. Twenty foreign bodies were correlated with surgical results. Surgical and clinical follow-up findings were in agreement with helical CT results regarding the detection and determination of the number of presumed foreign bodies. Localization to intraocular versus orbital compartment and proximity to the optic nerve was accurate in all patients. Determination of size of the foreign bodies on the helical CT images was reliable and repeatable. CONCLUSIONS: Helical CT axial scanning with multiplanar reconstruction is accurate at detecting and localizing intraocular and orbital metallic, glass, and stone foreign bodies. This imaging method aids the surgeon in choosing the surgical approach to retained intraocular and orbital foreign bodies.

Adolescent↗
PubMed1998

[Spiral CT and conventional CT in the preoperative imaging of intraocular metal foreign bodies].

PURPOSE: To compare the effectiveness of spiral CT versus conventional CT in the preoperative assessment of metallic intraocular foreign bodies. METHODS: Eighteen patients with penetrating eye injuries and suspected metallic intraocular foreign bodies were assigned to undergo either spiral CT or conventional CT in the axial plane. The spiral and the conventional CT data were transferred to a workstation, and reconstructions in the coronal and sagittal planes were performed. Additional direct coronal scanning was performed only when necessary for preoperative assessment. The quality of the axial as well as the reconstructed coronal and sagittal images was assessed for each imaging modality. The size of the foreign bodies was measured and compared to the actual diameter. Total examination time and radiation dose delivered to the lens were measured for each imaging modality. RESULTS: All foreign bodies were detected by each scanning modality on the axial and on the reconstructed planes. The quality of the axial images was similar for spiral and conventional CT. The spiral technique provided high-quality reconstructed images which allowed accurate localization of the foreign bodies in all cases. Reconstructions by conventional technique were inadequate for preoperative assessment. The examination time for the total orbital volume was 18 s for spiral CT and 52 s for conventional CT. Radiation dose delivered to the lens was 35 mGy for spiral CT and 56 mGy for conventional CT axial scanning. CONCLUSION: Spiral CT multiplanar imaging offers several significant advantages for the preoperative assessment of metallic intraocular foreign bodies compared to the conventional CT technique in clinical practice, including short examination time, minimized motion artifacts, reduced radiation exposure, and accurate localization.

Adolescent↗
PubMed1998

Imaging of the brain using the fast-spin-echo and gradient-spin-echo techniques.

The aim of our study was to compare gradient-spin-echo (GRASE) to fast-spin-echo (FSE) sequences for fast T2-weighted MR imaging of the brain. Thirty-one patients with high-signal-intensity lesions on T2-weighted images were examined on a 1.5-T MR system. The FSE and GRASE sequences with identical sequence parameters were obtained and compared side by side. Image assessment criteria included lesion conspicuity, contrast between different types of normal tissue, and image artifacts. In addition, signal-to-noise, contrast-to-noise, and contrast ratios and were determined. The FSE technique demonstrated more lesions than GRASE and with generally better conspicuity. Smaller lesions in particular were better demonstrated on FSE because of lower image noise and slightly weaker image artifacts. Gray-white differentiation was better on FSE. Ferritin and hemosiderin depositions appeared darker on GRASE, which resulted in better contrast. Fatty tissue was less bright on GRASE. With current standard hardware equipment, the FSE technique seems preferable to GRASE for fast T2-weighted routine MR imaging of the brain. For the assessment of hemosiderin or ferritin depositions, GRASE might be considered.

Adipose Tissue↗
PubMed1998

Multiplanar imaging in the preoperative assessment of metallic intraocular foreign bodies. Helical computed tomography versus conventional computed tomography.

OBJECTIVE: This study aimed to compare the effectiveness of helical computed tomography (CT) versus conventional CT in the preoperative assessment of metallic intraocular foreign bodies on axial, coronal, and multiplanar reconstruction images in clinical routine. DESIGN: Prospective comparative trial, alternate assignment of consecutive patients. PARTICIPANTS: Eighteen patients with penetrating eye injuries and suspected metallic intraocular foreign bodies were studied. INTERVENTION: Alternate patients were assigned to undergo either helical CT or conventional CT in the axial plane. Both the helical and the conventional data were transferred to a workstation, and reconstructions in the coronal and sagittal planes were performed. Additional direct coronal scanning was performed only when necessary for preoperative assessment. MAIN OUTCOME MEASURES: The quality of the directly obtained axial and coronal, as well as the reconstructed coronal and sagittal images, was assessed for each, imaging method based on the ability to detect and accurately localize foreign bodies. The size of the foreign bodies was measured and compared to the actual diameter. Total examination time and radiation dose delivered to the lens were measured for each imaging method. RESULTS: All foreign bodies were detected by each scanning method on the axial, the coronal, and on the reconstructed planes. The quality of the axial images was similar for helical and conventional CT. The helical technique provided high-quality reconstructed images comparable in quality to the directly obtained coronal planes in conventional CT. Reconstructions by conventional technique were not useful for preoperative assessment. The examination time for the total orbital volume was 18 seconds for helical CT examinations and 52 seconds for conventional CT examinations. Radiation dose delivered to the lens for the complete examination was 35 mGy for helical CT axial scanning, 56 mGy for conventional CT axial scanning, and 63 mGy for conventional CT coronal scanning. CONCLUSIONS: Helical CT multiplanar imaging offers several significant advantages for the preoperative assessment of metallic intraocular foreign bodies compared to the conventional CT technique in clinical practice, including short examination time, reduced motion artifacts, reduced radiation exposure, and the ability to obtain diagnostically useful coronal and sagittal reconstruction images without the need for additional scanning.

Adolescent↗
PubMed1997

Malposition of central venous catheters. Incidence, management and preventive practices.

INTRODUCTION: Proper placement is an essential prerequisite for the use of central venous catheters. Our study was undertaken to determine the incidence of aberrant locations dependent on different anatomic approaches for various types of central venous catheters and to elucidate failures and pitfalls of preventive practices. METHODS: 2580 percutaneously inserted lines (including 538 tunneled devices and 112 implantable Port-A-Caths) introduced by Seldinger's technique were reviewed for inadvertent malpositioning. RESULTS: Primary misplacement was evident on 47 occasions (1.82%), 38 times into large venous tributaries of the superior vena cava. 3 aberrant locations involved a persistent left superior vena cava, two catheters were placed into minor intrathoracic veins and in 3 patients inadvertent arterial cannulation occurred. The frequency of malpositioning was related to the anatomic approach and the catheter type used, but not to the physician's experience. Respective incidences were 4.12% for the left internal jugular access, but were lower for the right internal jugular (1.1%) and the right (1.01%) and left (0.89%) supraclavicular approach. Misplacement was more frequent with soft silicone catheters (2.53%) than with semi-rigid catheters (0.79%). All malpositions but one were detected on chest X-ray. DISCUSSION: Our data suggest that the incidence of catheter malposition depends on the site of insertion, the type of material used, but not on the experience of the physician who inserted the catheter. Scrupulous use of preventive practices reduces the frequency of malpositioned catheters, but physicians must keep in mind potential pitfalls. Injection of radioopaque contrast medium into the catheter during control chest X-ray should be done even with opaque catheters.

Adult↗
PubMed1997

Biliary Wallstent endoprosthesis in malignant hilar obstruction: long-term results with regard to the type of obstruction.

AIM: To evaluate the clinical efficacy of percutaneously placed biliary Wallstents in the management of malignant hilar obstruction with regard to the obstruction type. PATIENTS AND METHODS: Sixty-six Wallstents were inserted in 41 patients with inoperable hilar obstruction: 13 patients had a type I obstruction according to Bismuth-classification, 18 a type II, eight a type III, and two a type IV obstruction, respectively. Clinical follow-up data were obtained from all the patients and the referring physicians. RESULTS: Stent placement was technically successfully in all patients. The procedure-related death rate was 2% (one patient), but the overall 30-day mortality rate was 39%, mostly due to advanced malignant disease, cardiac failure or pneumonia. Stent occlusion was found in 11 patients (27%) after 87 days (mean; range, 8-190 days). After stent placement, the mean stent patency was 96 days and the mean survival was 131 days with no significant difference between patients with obstruction type I, II and III. Multivariate analysis revealed that patients with obstruction due to gallbladder carcinoma had a significantly shorter survival than patients with cholangio-carcinoma or hilar obstruction due to metastases. CONCLUSION: Overall, the insertion of Wallstent endoprostheses offers moderate results for palliation of hilar biliary obstruction regardless of the type of obstruction. In patients with cholangiocarcinoma, long-term results are good even for complicated strictures (type III). In patients with hilar obstruction due to gallbladder carcinoma the outcome is generally poor, regardless of the type of obstruction.

Adult↗
PubMed1997

Vasoactive intestinal peptide and somatostatin receptor scintigraphy for differential diagnosis of hepatic carcinoid metastasis.

We report a case of a hepatic carcinoid metastasis mimicking a hemangioma on ultrasound and on CT. Indium-111-DTPA-D-Phe-1-octreotide (111In-OCT) and 123I-vasoactive intestinal peptide (123I-VIP) receptor images suggested a carcinoid metastasis of the liver. The final diagnosis was established histopathologically. The differential diagnosis of liver lesions is discussed.

Carcinoid Tumor↗