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Biomedical subjects

R Kröger

Publications and source records attributed to R Kröger.

At least 19 recordsLinked to original sources
PubMed2006

Plant senescence: a mechanism for nutrient release in temperate agricultural wetlands.

The beneficial uptake of nutrients by wetland plants is countered to some extent by nutrient release back into the aquatic environment due to vegetative die-back. This current study examined whether Leersia oryzoides, a common wetland plant, exhibits luxury uptake of nutrients from simulated farm runoff. The study also tested whether with subsequent decomposition, these nutrients are released back into the water column. When exposed to elevated (>2mg/L N and P) runoff, L. oryzoides assimilated significantly higher concentrations of nitrogen (p<0.001) and phosphorus (p<0.001) in above-ground biomass as compared to non-enriched treatments (<0.05 mg/L N and P). Subsequently, senescence of enriched above-ground biomass yielded significantly higher concentrations of phosphorus (2.19+/-0.84 mg P/L). Using L. oryzoides as our model, this study demonstrates nitrogen and phosphorus sequestration during the growing season and release of phosphorus in the winter.

Adsorption↗
PubMed2006

Less strain energy despite fewer misfit dislocations: the impact of ordering.

The average strain state of Ge films grown on Si(111) by surfactant mediated epitaxy has been compared to the ordering of the interfacial misfit dislocation network. Surprisingly, a smaller degree of average lattice relaxation was found in films grown at higher temperature. On the other hand, these films exhibit a better ordered dislocation network. This effect energetically compensates the higher strain at higher growth temperature, leading to the conclusion that, apart from the formation of misfit dislocations, their ordering represents an important channel for lattice-strain energy relaxation.

Journal Article↗
PubMed2005

Preoperative computed tomography and selection of patients with colorectal peritoneal carcinomatosis for cytoreductive surgery and hyperthermic intraperitoneal chemotherapy.

AIM: A survival benefit has been observed for colorectal cancer patients with peritoneal carcinomatosis treated by cytoreductive surgery with intraoperative hyperthermic intraperitoneal chemotherapy (HIPEC). However, this treatment modality is associated with a considerable morbidity and mortality and in a significant number of patients survival is not improved. We studied whether poor survivors could be identified on preoperative computed tomography (CT), in order to avoid unnecessary surgery. PATIENTS AND METHODS: Films of abdominopelvic CT scans from 25 such patients treated by cytoreductive surgery and HIPEC were retrospectively analysed by two radiologists separately. A simplified peritoneal cancer index (SPCI) was used to determine the extent of peritoneal involvement. Correlation between the on preoperative CT based SPCI-scores as well as number of involved abdominopelvic areas (N) and survival was examined with the log-rank test. The relation between each affected region and survival was evaluated with Cox regression analysis. RESULTS: The preoperative SPCI- and N-scores of one of the radiologists had no statistically significant prognostic value, while for the second radiologist SPCI > or = 7 and N > or = 4 were associated with particularly poor outcome. Additionally, the presence of ileocaecal region involvement and, depending on the radiologist, the occurrence of tumour deposits in the left subdiaphragmatic area on CT appeared to be unfavourable prognostic signs. CONCLUSIONS: The prognostic value of preoperative conventional CT appeared to be radiologist dependent and may, therefore, be of limited value in selecting colorectal cancer patients with peritoneal carcinomatosis who will not benefit from extensive cytoreductive surgery followed by HIPEC.

Antineoplastic Agents↗
PubMed2005

Minimally invasive neurosurgery within a 0.5 tesla intraoperative magnetic resonance scanner using an off-line neuro-navigation system.

BACKGROUND AND PURPOSE: We evaluated an advanced concept for patient-based navigation during minimally invasive neurosurgical procedures. METHODS: An infrared-based, off-line neuro-navigation system (LOCALITE, Bonn, Germany) was applied during operations within a 0.5 T intraoperative MRI scanner (iMRI) (Signa SF, GE Medical Systems, Milwaukee, WI, USA) in addition to the conventional real-time system. The three-dimensional (3D) data set was acquired intraoperatively and up-dated when brain-shift was suspected. Twenty-three patients with subcortical lesions were operated upon with the aim to minimise the operative trauma. RESULTS: Small craniotomies (median diameter 30 mm, mean diameter 27 mm) could be placed exactly. In all cases, the primary goal of the operation (total resection or biopsy) was achieved in a straightforward procedure without permanent morbidity. The navigation system could be easily used without technical problems. In contrast to the real-time navigation mode of the MR system, the higher quality as well as the real-time display of the MR images reconstructed from the 3D reference data provided sufficient visual-manual coordination. CONCLUSION: The system combines the advantages of conventional neuro-navigation with the ability to adapt intraoperatively to the continuously changing anatomy. Thus, small and/or deep lesions can be operated upon in straightforward minimally invasive operations.

Adolescent↗
PubMed2003

Reduction in the number of sentinel lymph node procedures by preoperative ultrasonography of the axilla in breast cancer.

Currently, breast cancer patients without clinically suspicious lymph nodes are candidates for sentinel lymph node procedures (SLNPs). The aims of this study were to investigate whether preoperative axillary ultrasonography and fine-needle aspiration cytology (FNA) can reduce the number of the more time-consuming SLNPs, and to identify a subset of quantitative nodal features to predict metastatic involvement. 268 axillae were ultrasonographically examined. FNA was performed on suspicious nodes (smallest diameter > or =5 mm or atypical cortex appearance). SLNP was omitted if a tumour-positive node was found on FNA. Length, width, maximum cortex thickness and appearance of cortex and hilus were ultrasonographically established. In 93 axillae (35%), at least one node was detected with ultrasound. FNA was performed once per axilla on 66 nodes; 37 (56%) contained tumour cells. 31% of all tumour-positive axillae (macro-+micrometastases) was found by ultrasound and FNA (37/121). 41% of all axillae containing macrometastases was found by ultrasound and FNA (36/87). SLNPs were reduced by 14% (37/268). Maximum cortex thickness is the main feature to predict metastatic involvement (area under Receiver Operating Characteristic (ROC) curve (A(Z))=0.87).

Adult↗
PubMed2001

Percutaneous radiological gastrostomy in patients with head and neck cancer.

AIM: To evaluate the results of percutaneous radiological gastrostomy in patients with head and neck cancer. PATIENTS AND METHODS: This was a retrospective study design. One hundred and eighteen patients with head and neck cancer were referred 130 times for gastrostomy tube placement between 1 April 1993 and 17 August 1998. Mean age was 60 years. All data were analysed by using the following parameters: success rate, complications and mortality. Complications were divided into major, minor (complication that needed only conservative treatment) and tube-related. RESULTS: The success rate of percutaneous radiological gastrostomy was 97%. Major complications occurred in 6% of patients after gastrostomy tube placement. Minor complications occurred in 15% of patients. There was one tube-related complication. Procedure-related mortality occurred in one patient. The results of this study show no difference from those known from the literature for the percutaneous method and confirm that radiological gastrostomy has significantly lower rates of major complications than other methods of gastrostomy placement. CONCLUSION: Percutaneous radiological gastrostomy tube placement is, in our opinion, an effective and reliable method for placing a feeding tube in patients with head and neck cancer.

Adult↗
PubMed2000

Use of balloon catheters for ureteral occlusion in urinary leakage.

PURPOSE: Urinary fistula after treatment for cancer constitutes a therapeutic dilemma, especially in patients who have had various other treatments. We report on 7 patients with urinary leakage, treated conservatively with ureteric occlusion by way of percutaneous transrenal balloon catheters. MATERIALS AND METHODS: The indication for ureteral occlusion was persisting urinary leakage despite diversion by nephrostomy and drainage with atransurethral catheter. All patients had had previous treatment because of pelvic malignancy. Small Foley balloon catheters and angioplasty catheters were used. These devices were inserted percutaneously in an antegrade fashion. RESULTS: In all but 2 of the patients the leakage ceased with the aid of these devices. Insufficient ureteral occlusion necessitated unilateral uretero-cutaneostomy in 1 patient. In another patient a vesico vaginal fistula was closed surgically. The maximum duration of occlusion was 169 (mean 94, range 45-169) days, without any evidence of ureteric pressure necrosis. Despite good overall results many adjustments and replacements of catheters were necessary because of recurrent urinary leakage caused by inadequate obstruction and/or leakage of the occluding catheters. CONCLUSIONS: We conclude that long-term ureteral occlusion with percutaneous transrenal balloon catheters appears to be safe and does not result in pressure necrosis. Using this approach, urinary fistula can heal in some patients without the need for open surgery.

Adult↗
PubMed1999

Recurrent spinal epidural metastases: a prospective study with a complete follow up.

OBJECTIVES: Prospective studies with a complete follow up in patients with spinal epidural metastases (SEM) are rare, so little is known of the incidence and relevance of recurrent spinal epidural metastases (RSEM). This prospective study was undertaken as a part of a previously started and extended prospective study to determine the occurrence and details of RSEM. METHODS: Patients with SEM of various primary malignancies were followed up until death. The diagnosis was confirmed after neurological examination by imaging studies visualising not only the clinically suspected level, but also as much of the spinal canal as possible. RESULTS: Recurrent spinal epidural metastases (RSEM) occurred in 21 of the 103 patients (20%) after a median interval of 7 months and, after treatment, a second recurrence occurred in 11 patients (11%), a third recurrence in two patients (2%), and a sixth recurrence in one patient (1%). RSEM developed about as often at the initial level (55%) as at a different level (45%), did not occur more often in patients with initially multiple SEM, but, not surprisingly, occurred much more often in patients with longer survival. About one half of the patients surviving 2 years, and nearly all patients surviving 3 years or longer developed RSEM. Ambulatory state could be preserved in most patients, even after their second recurrence. CONCLUSION: RSEM are common and even several episodes of RSEM in the same patient are not rare. Patients with SEM who survive long enough have a high risk of RSEM and prompt treatment of RSEM to maintain the ambulatory state of the patient is valuable.

Epidural Space↗
PubMed1995

Treatment of patients with IVCS and gross oedema and ascites with diuretic combination and ACE-inhibitors: relation to baseline PRA and PAC.

OBJECTIVE: (1) To assess plasma renin activity (PRA) and plasma aldosterone concentration (PAC) in patients with inferior vena cava syndrome (IVCS). (2) To study in an open fashion the efficacy of loop diuretic treatment, single, or in combination with an ACE-inhibitor or with spironolactone. METHODS: In 13 patients PRA and PAC were measured and related to urinary sodium excretion (UNa). RESULTS: Highly elevated PRA and PAC were found in recently developed IVCS. The correlation coefficient between PAC and UNa was -0.61, p < 0.05. In 10 patients the influence of captopril (C)] at maximum tolerable doses with or without furosemide (F) was evaluated. Mean tolerated dose of C amounted to 8.8 mg t.i.d. (range 2-25), achieving a PAC reduction of 26%. Efficacy of F was severely blunted when PAC exceeded the low-normal range. Spironolactone addition at 100 mg/day in non-responders to F or to F and C, induced immediate natriuretic responses except in a patient with 7-70 fold increase in PAC. CONCLUSIONS: (1) In IVCS loop diuretic efficacy is attenuated by aldosterone activation; (2) complete aldosterone suppression with captopril is difficult to achieve due to dose restriction; (3) spironolactone is favoured for a synergistic response.

Adult↗
PubMed1994

Ultrasound in squamous cell carcinoma of the penis; a useful addition to clinical staging? A comparison of ultrasound with histopathology.

OBJECTIVE: As part of the staging procedure in squamous cell carcinoma of the penis, we assessed the role of ultrasound examination, in particular its role in assessing the extent and the invasion into the corpora. METHODS: From 1988 until 1992, all patients referred for primary treatment underwent ultrasound assessment with a 7.5 MHz linear array small parts transducer as part of the clinical workup. All ultrasound images were reviewed by one radiologist, without knowledge of the clinical outcome and were compared with the results obtained at histopathologic examination. RESULTS: In 16 patients the primary tumor and in 1 patient a recurrent cancer after primary therapy were examined. All tumors were identified as hypoechoic lesions. Ultrasound examination in the region of the glans was not able to differentiate between invasion of the subepithelial tissue and invasion into the corpus spongiosum, but absence or presence of invasion into the tunica albuginea of the corpus cavernosum was clearly demonstrated. Accurate measurement by ultrasound of maximum tumor thickness was seen in seven of sixteen examinations. CONCLUSIONS: While ultrasound examination is inexpensive and easily done, it is not accurate enough for staging small penile cancers located at the glans penis. However, for larger tumors ultrasound can be a useful addition to physical examination by delineating reliably the anatomic relations of the tumor to structures such as the tunica albuginea, corpus cavernosum, and urethra.

Carcinoma, Squamous Cell↗
PubMed1993

Central venous catheter associated thrombosis of major veins: thrombolytic treatment with recombinant tissue plasminogen activator.

OBJECTIVE: Major thromboses can occur in the venous system in association with central venous catheters. This usually necessitates removal of the catheter. METHODS: The effectiveness of low dose recombinant tissue type plasminogen activator (rt-PA) in combination with heparin was assessed in patients with central venous catheter associated thrombosis. RESULTS: In five patients, all suffering from cancer, a 5-7 day continuous infusion resulted in complete lysis of the thrombus without complications in three. In the other two patients moderately severe haemorrhage was observed with only partial lysis, of the thrombus. CONCLUSIONS: The infusion of heparin and rt-PA is potentially effective in thrombosis related to use of central venous catheters, but the risk of haemorrhage is not inconsiderable.

Adult↗
PubMed1992

Early diagnosis and treatment of spinal epidural metastasis in breast cancer: a prospective study.

This prospective study evaluated the usefulness of myelography in breast cancer patients who present with radiculopathy or myelopathy. A total of 124 consecutive myelograms were performed in 100 patients. Epidural metastasis (EM) was diagnosed in 67 myelograms (54%). Multiple epidural metastases were diagnosed in 15 (22%) of those, resulting in a total of 87 epidural lesions. A complete block was found in 13 EM (15%) and an incomplete block in 14 EM (16%). Clinical data could not predict the site of EM in 29 cases (33%). Fifteen asymptomatic EM were detected in myelograms with multiple EM. Plain radiographs were of no value in determining the site of EM in 29 cases (33%), including 13 cases (15%) without vertebral metastasis at the site of EM. Treatment consisted of radiotherapy (RT) with or without systemic treatment in 52 cases (80%), systemic treatment alone in 11 cases (17%) and surgery in two patients (3%). Clinical improvement was noticed in 72%, no change in 13%, and deterioration in 15%. No difference in response was noticed between RT and systemic therapy. Before treatment 21% and after treatment 15% of the patients could not walk. The one year survival was 42%. The ambulatory status at presentation was the most important prognostic factor. Examination of the spinal fluid, obtained at myelography, disclosed meningeal carcinomatosis in 9% of the patients. Imaging of the whole spinal canal with cytological examination of the spinal fluid is recommended in breast cancer patients suspected of epidural tumour with features of radiculopathy or myelopathy, irrespective of further clinical data and plain spinal radiographs.

Adult↗
PubMed1991

The need for immediate monitoring of treatment parameters and uniform assessment of patient data in clinical trials. A quality control study of the EORTC Radiotherapy and Lung Cancer Cooperative Groups.

A quality control study was performed during the EORTC phase III study 08844: radiotherapy combined with low dose cisplatin (cDDP) in inoperable non-metastatic non-small cell lung cancer. Radiation alone (55 Gy, split course) was compared to radiotherapy with 30 mg/m2 cisplatin once a week and to radiotherapy with 6 mg/m2 cisplatin daily. The purpose of the control study was to check to which degree protocol guidelines were followed and to measure the extent of differences in assessment of tumour response, recurrence and toxicities between the individual institutes. A review team, consisting of a data manager, a diagnostic radiologist, a chest physician and two radiotherapists reviewed entry criteria, treatment data, tumour responses, recurrences and late toxicity of 177 patients (a total of 300 patients was required for the trial). Only departments which had entered more than 5% of this number of patients were visited. There was a 15% difference in T staging of the patients and a 17% discrepancy in N stage scoring between the review team and the local investigators. Radiotherapy field sizes were insufficient in 15% of the eligible patients during a period of the radiotherapy; in another 17% patients the tumour free margin was less than 1 cm. Radiation doses were incorrectly given to 7% of the patients. The given doses of cisplatin deviated in 10% of the patients treated with combined modalities. The interpretation of chest X-rays and computed tomography (CT) showed important differences in tumour response, tumour recurrence and late toxicity. From these data it is concluded that immediate checks can detect errors in treatments as planned at the local level and will make corrections possible at an early stage in multicentre studies. The quality of trial results will thus be improved. Uniform assessment of treatment outcome, tumour progression and forms of toxicity will lead to more sound trial conclusions.

Carcinoma, Bronchogenic↗
PubMed1991

Squamous cell carcinoma of the penis: accuracy of tumor, nodes and metastasis classification system, and role of lymphangiography, computerized tomography scan and fine needle aspiration cytology.

Among 118 patients with squamous cell carcinoma of the penis treated at our cancer institute between 1956 and 1989, we analyzed the accuracy of classification, using the tumor, nodes and metastasis system. We analyzed the role of lymphography, computerized tomography and fine needle aspiration cytology as additional staging procedures. The primary tumor (T category) was classified incorrectly in 26% of the cases. Overstaging was noted in 10% of the cases because of unsuspected infiltration and overstaging was noted in 16%. Overstaging occurred because of edema and infection masking the actual size and giving a misconception of infiltration, and also because of primary presentation as large exophytic tumors with no or minimal histopathological infiltration. When the regional lymph nodes were categorized simply as positive or negative 80% of the tumors were classified correctly and 20% incorrectly (13% were false positive and 7% were false negative). Regional lymph node invasion that escaped clinical examination was not detected by any imaging examination or fine needle aspiration cytology study. Positive findings were found only in patients with clinically suspected nodes. The classification of regional nodes by clinical examination only is hardly improved by additional imaging studies. Clinical decisions with respect to the management of regional lymph nodes should not be based on negative findings of lymphangiography, computerized tomography or fine needle aspiration cytology. In patients with proved metastasis additional imaging may be of some help in the detection of pelvic node invasion and the determination of the extent of involvement. We recommend lymphangiography as the examination of choice.

Adult↗
PubMed1991

Intravenous contrast in spinal computed tomography to identify epidural metastases.

In 16 patients with spinal epidural metastases from various neoplasms the usefulness of intravenous (IV) contrast injection in spinal computed tomography (CT) scanning was analyzed for determining the presence and extent of the epidural lesion. In all cases enhancement of the epidural tumor mass occurred, which effectively showed the outline of the lesion. The extent of the epidural metastases in the spinal canal was equally well visualized as by myelography. Compared to spinal CT scanning without contrast administration, all IV contrast enhanced CT scans were clearly superior in demonstrating epidural metastases. Intravenous contrast in spinal CT-scanning appears to add relevant information and seems a useful and simple method to define the extent of the epidural tumor. It should be considered in patients where myelography is contraindicated and it may be a valuable method when the response of the epidural tumor to treatment must be determined.

Contrast Media↗
PubMed1990

Multiple spinal epidural metastases; an unexpectedly frequent finding.

In a prospective study, patients with known malignant disease who were suspected of having a spinal epidural metastasis, had myelography which was not confined to the clinically suspected site, but included at least the whole lumbar and thoracic spinal canal. Fifty four of the 106 myelograms revealed at least one epidural metastasis. Twelve of these 54 myelograms showed two separate lesions, and four myelograms showed three separate lesions. In all 16 cases with multiple lesions at least one of the lesions was asymptomatic at the time of the diagnosis. It is concluded that multiple spinal epidural metastases are of common occurrence and occur in about one third of the cases. This finding may have important clinical implications. Examination of the spinal canal for epidural metastases should not be confined to the clinically suspected site, but should include as extensive an area as possible of the spinal canal, whatever technique is to be used.

Adult↗
PubMed1989

Effective systemic therapy for spinal epidural metastases from breast carcinoma.

A complete resolution of spinal epidural metastases following systemic therapy, consisting of chemotherapy and/or hormonal therapy, is reported in four patients with breast carcinoma. Remissions were of substantially longer duration than previous remissions induced by radiotherapy. Single systemic therapy is an underestimated way of treatment for spinal epidural metastases. This way of treatment should be considered when radiotherapy has failed. Under certain circumstances it might even be considered as primary treatment. The protracted remissions following systemic therapy, even in the case of a complete myelographic block, warrant further clinical studies concerning this mode of treatment.

Adult↗