Biomedical subjects

J Gellermann

Publications and source records attributed to J Gellermann.

At least 19 recordsLinked to original sources

PubMed2006

Influence of neoadjuvant radiochemotherapy combined with hyperthermia on the quality of life in rectum cancer patients.

PURPOSE: The present study compares quality of life (QoL) after neoadjuvant radiochemotherapy with or without hyperthermia in patients with advanced rectal cancer. METHODS: Between April 1994 and May 1999, 137 patients were treated by neoadjuvant radiochemotherapy with (69 patients (50.4%)) or without (68 patients (49.6%)) hyperthermia. Forty-six patients (33.6%) filled-out a 'Gastrointestinal Quality of Life Index' (GIQLI) questionnaire at four time points (before and after neoadjuvant therapy, early after surgery and after long-term follow-up) and were included in the present study. RESULTS: There were no statistically significant differences in the global GIQLI index between patients treated with neoadjuvant radiochemotherapy with and without hyperthermia at any time point. The longitudinal analysis of GIQLI values in both treatment groups showed specific profiles that were identical in both treatment groups. Occurrence of severe toxicity during the neoadjuvant therapy in both arms lead to a significant temporary reduction of QoL scores at TP2 without any detrimental long-term effects. Patients with sphincter preservation and patients with sphincter resection reported similar QoL scores during long-term follow-up. CONCLUSION: Neoadjuvant radiochemotherapy with and without hyperthermia has similar effects on the QoL of patients with locally advanced rectal cancer. The addition of hyperthermia during the neoadjuvant therapy with the potentially associated inconveniences has no negative effects on QoL.

Adult↗

PubMed2006

Comparison of MR-thermography and planning calculations in phantoms.

A systematic comparison of three-dimensional MR (magnetic resonance) thermography and planning calculations in phantoms for the hyperthermia (HT) SIGMA-Eye applicator. We performed 2 x 6 experiments in a homogeneous cylindrical and a heterogeneous elliptical phantom by adjusting 82 different patterns with different phase control inside an MR tomograph (Siemens Magnetom Symphony, 1.5 Tesla). For MR thermography, we employed the proton resonance frequency shift method with a drift correction based on silicon tubes. For the planning calculations, we used the finite-difference time-domain (FDTD) method and, in addition, modeled the antennas and the transforming network. We generated regions according to a segmentation of bones and tissue, and used an interpolation technique with a subgrid of 0.5 cm size at the interfaces. A Gauss-Newton solver has been developed to adapt phases and amplitudes. A qualitative agreement between the planning program and measurements was obtained, including a correct prediction of hot spot locations. The final deviation between planning and measurement is in the range of 2-3 W/kg, i.e., below 10%. Additional HT phase and amplitude adaptation, as well as position correction of the phantom in the SIGMA-Eye, further improve the results. HT phase corrections in the range of 30-40 degrees and HT amplitude corrections of +/- 20-30% are required for the best agreement. The deviation /MR-FDTD/, and the HT phase/amplitude corrections depend on the type of phantom, certain channel groups, pattern steering, and the positioning error. Appropriate agreement between three-dimensional specific absorption rate distributions measured by MR-thermography and planning calculations is achieved, if the correct position and adapted feed point parameters are considered. As long as feed-point parameters are uncertain (i.e., cannot be directly measured during therapy), a prospective planning will remain difficult. However, we can use the information of MR thermography to better predict the patterns in the future even without the knowledge of feed-point parameters.

Algorithms↗

PubMed2005

Methods and potentials of magnetic resonance imaging for monitoring radiofrequency hyperthermia in a hybrid system.

INTRODUCTION: Non-invasive thermometry (NIT) is a valuable and probably indispensable tool for further development of radiofrequency (RF) hyperthermia. A hybridization of an MRI scanner with a hyperthermia system is necessary for a real-time NIT. The selection of the best thermographic method is difficult, because many parameters and attributes have to be considered. METHODS: In the hybrid system (Siemens Symphony/BSD-2000-3D) the standard methods for NIT were tested such as T1, diffusion (ADC: apparent diffusion coefficient) and proton-resonance-frequency shift (PFS) method. A series of three-dimensional datasets was acquired with different gradient-echo sequences, diffusion-weighted EPI spin-echo sequences and calculated MR-temperatures in the software platform AMIRA-HyperPlan. In particular for the PFS-method, corrective methods were developed and tested with respect to drift and other disturbances. Experiments were performed in phantoms and the results compared with direct temperature measurements. Then the procedures were transferred to clinical applications in patients with larger tumours of the lower extremity or the pelvis. RESULTS: Heating experiments and MR-thermography in a homogeneous cylindrical phantom give an excellent survey over the potentials of the methods. Under clinical conditions all these methods have difficulties due to motion, physiological changes, inhomogeneous composition and susceptibility variations in human tissues. The PFS-method is most stable in patients yielding reasonable MR temperature distributions and time curves for pelvic and lower extremity tumours over realistic treatment times of 60-90 min. Pooled data exist for rectal tumour recurrencies and soft tissue sarcomas. The fat tissue can be used for drift correction in these patients. T1 and diffusion-dependent methods appear less suitable for these patients. The standard methods have different sensitivities with respect to the various error sources. The advantages and pitfalls of every method are discussed with respect to the literature and illustrated by the phantom and patient measurements. CONCLUSIONS: MR-controlled RF hyperthermia in a hybrid system is well established in phantoms and already feasible for patients in the pelvic and lower extremity region. Under optimal conditions the temperature accuracy might be in the range of 0.5 degrees C. However a variety of developments, especially sequences and post-processing modules, are still required for the clinical routine.

Humans↗

PubMed2004

[Part-body hyperthermia with a radiofrequency multiantenna applicator under online control in a 1.5 T MR-tomograph].

Objective of this study is the integration of a multiantenna applicator for part-body hyperthermia (BSD 2000/3D) in a 1.5 T MR-tomograph (Siemens Magnetom Symphony) in order to perform noninvasive MR monitoring in real time to increase safety and effectiveness of heat treatments. The positioning unit is mechanically coupled to the MR gantry from the back side and the body coil is utilised for imaging. For that purpose, the hyperthermia antenna system (100 MHz, 1.500 W) and the MR receiver (63.9 MHs) have to be decoupled in terms of high frequency (filter) and electromagnetically (emc). The processing of MR data sets is performed in a hyperthermia planning system. A simultaneous operation of radiofrequency hyperthermia and MR system is possible at clinically relevant power levels. MR imaging is used for tumor-diagnostics (standard spin echo sequences), for hyperthermia planning (T1-weighted gradient echo sequences in equal- and opposed-phase techniques), and for temperature measurements according to the proton resonance frequency method (PRF method, phase evaluation registration using a gradient echo sequence with long echo time). In 33 patients with advanced pelvic and abdominal tumors we performed 150 heat sessions under MR monitoring. For 70% of these patients a visualisation of temperature sensitive data during treatment was possible. The evaluated difference images represent a superposition of real temperature -increase and a (temperature-induced) perfusion elevation. The -hybrid approach renders development of part body hyperthermia possible as an MR-controlled intervention in radiology.

Abdominal Neoplasms↗

PubMed2004

Treatment of locally recurrent rectal cancer with special focus on regional pelvic hyperthermia.

Progress in surgery and adjuvant therapy has markedly improved local control and survival rates in patients with primary, non-metastatic rectal cancer. However, the prognosis of patients with locally recurrent disease is still poor, and a realistic chance for repeated treatment with curative intent is still restricted to the minority of cases. Therefore, effective palliation of symptoms and preservation of a good quality of life are the major goals of therapy for most patients with local recurrence of rectal cancer. Here we give a short overview on the options available for the treatment of pelvic recurrence of rectal cancer, with special focus on adjunctive regional pelvic radiofrequency hyperthermia.

Combined Modality Therapy↗

PubMed2003

Survival in second trimester oligohydramnios secondary to bilateral pelviureteral junction obstruction.

The extent and onset of obstruction in hydronephrosis determine the varying degrees of renal impairment. Bilateral hydronephrosis, especially in combination with oligohydramnios, is considered a negative predictor for pregnancy outcome. We describe a case of bilateral pelviureteral junction obstruction causing severe oligohydramnios between 25 and 29 weeks of gestation. The prenatal and postnatal findings and treatment are demonstrated. In the presence of bilateral renal impairment and oligohydramnios, our patient had an unfavorable prognosis. The respiratory and renal function, however, were better than expected. We show how urinary tract reconstruction and neonatal intensive therapy can result in an acceptable outcome.

Apgar Score↗

PubMed2002

[T4 rectal carcinoma. Surgical and multimodal therapy].

BACKGROUND: In locally advanced rectal cancer with infiltration of neighbouring organs (uT4), resectability and local control are difficult to achieve. Combined preoperative radiochemotherapy may result in increased resectability and reduced local recurrence rates. PATIENTS AND METHODS: Thirty-four patients with biopsy-proven locally advanced rectal cancer were treated by preoperative radiochemotherapy. All tumours had been staged as uT4 lesions by endorectal ultrasound or computed tomography. Radiotherapy was applied in standard blocks, 5 x 1.8 Gy up to 45 Gy. Chemotherapy consisted of two cycles of 5-fluorouracil (300-350 mg/m2/day) and leucovorin (50 mg). In 20 patients, additional thermotherapy was carried out using the Sigma 60 applicator BSD 2000 once a week prior to radiotherapy. Surgery was performed 4-6 weeks after radiochemotherapy. Postoperatively, all patients received four cycles of 5-fluorouracil and leucovorin. RESULTS: Treatment-induced toxicity occurred in 26% of the patients (WHO grade III (n = 6) and IV (n = 3)). The resectability rate was 76% (26/34 patients) (R0 resectability n = 21; 62%). The pathological complete response rate was 6% (n = 2) and the partial response rate was 47% (n = 16). A local failure was observed in six patients after median time of 16 months (range 7-36 months). Patients with R0 resection achieved a 5-year disease-free survival rate of 55% and a survival rate of 71%. The overall 5-year survival rate for all patients with advanced uT4 rectal cancer was 49%. CONCLUSIONS: Our data on preoperative combined treatment in locally advanced T4 rectal cancer revealed encouraging downstaging, local control, and survival rates.

Adult↗

PubMed2002

Hyperthermia in combined treatment of cancer.

Hyperthermia, the procedure of raising the temperature of tumour-loaded tissue to 40-43 degrees C, is applied as an adjunctive therapy with various established cancer treatments such as radiotherapy and chemotherapy. The potential to control power distributions in vivo has been significantly improved lately by the development of planning systems and other modelling tools. This increased understanding has led to the design of multiantenna applicators (including their transforming networks) and implementation of systems for monitoring of E-fields (eg, electro-optical sensors) and temperature (particularly, on-line magnetic resonance tomography). Several phase III trials comparing radiotherapy alone or with hyperthermia have shown a beneficial effect of hyperthermia (with existing standard equipment) in terms of local control (eg, recurrent breast cancer and malignant melanoma) and survival (eg, head and neck lymph-node metastases, glioblastoma, cervical carcinoma). Therefore, further development of existing technology and elucidation of molecular mechanisms are justified. In recent molecular and biological investigations there have been novel applications such as gene therapy or immunotherapy (vaccination) with temperature acting as an enhancer, to trigger or to switch mechanisms on and off. However, for every particular temperature-dependent interaction exploited for clinical purposes, sophisticated control of temperature, spatially as well as temporally, in deep body regions will further improve the potential.

Animals↗

PubMed2002

Type I IgE receptor, interleukin 4 receptor and interleukin 13 polymorphisms in children with nephrotic syndrome.

Polymorphisms in the genes encoding the high-affinity IgE receptor, the interleukin 4 (IL4) receptor and IL13 can be associated with the development of asthma and allergy. Although several studies have described an association between atopy and idiopathic childhood nephrotic syndrome (NS), it is not clear whether this association is of a causal nature. Furthermore, it is not known whether these polymorphisms are associated with the clinical course of NS. A total of 84 children (52 male and 32 female; mean age 12.1 years) with NS were included in the present study. Of these, 78 could be classified as either atopic or non-atopic. Atopy was defined by elevated IgE levels (>100 k-units/l) and/or a positive history of atopy (33 of 78 patients). DNA was extracted from blood collected in EDTA tubes, and polymorphisms at positions 50 and 551 of the IL4 receptor, position 110 of IL13 and position 181 of the high-affinity IgE receptor were investigated by sequence-specific PCR or direct sequencing. Although we noted a strong tendency towards a higher allele frequency of polymorphisms in children with atopy and NS compared with children with NS but without atopy (IL4 50, 30% compared with 18%; IL4 551, 39% compared with 31%; IL13 110, 45% compared with 33%; IgE 181, 12% compared with 13%), these differences did not reach statistical significance. There were no differences in the frequency of polymorphisms between the different clinical courses of NS (frequent relapsers, steroid-dependent or steroid-resistant NS). We conclude that polymorphisms in the IL4 receptor, the high-affinity IgE receptor and IL13 do not seem to predict the clinical course of NS, despite the fact that serum IgE elevations are more frequent in patients with NS than in normal control subjects. The investigated polymorphisms may contribute to the IgE switch in patients with NS.

Adolescent↗

PubMed2001

Antenna arrays in the SIGMA-eye applicator: interactions and transforming networks.

OBJECTIVES: In multiantenna applicators such as the SIGMA-60 or SIGMA-Eye, which consist of 4 or 12 pairs of antennas shunt to 4 or 12 amplifiers ("antenna couplets"), phases and amplitudes in the feed points of these antennas under certain conditions can significantly differ from the values selected at the multichannel amplifier (forward parameters), mainly due to coupling. In the SIGMA-Eye, this interaction is particularly affected by the transforming networks between the generators and the feed points, thus hampering the control of the feed point parameters. In this work, we perform measurements at existing applicators, present a formalism to describe the facts numerically, and investigate modifications of the transforming networks to improve the performance. METHODS AND MATERIALS: We prepared an experimental setup for the SIGMA-Eye applicator that is fed by forward waves of a 12-channel amplifier system. In this setup, we made the water bolus, the interior of the tissue-equivalent phantom, and the entire transforming network accessible for measuring probes. Then, we constructed various alternative transforming networks such as Pawsey loops, LC matching networks, and power dividers and compared them with the original matching network of the SIGMA-Eye applicator. In particular, we utilized a high-resistive probe to determine the disturbances and influences caused by some channels with respect to some selected feed points of the SIGMA-Eye dipoles. RESULTS: In the original SIGMA-Eye applicator, the influences of coupling channels on the phases and voltages in the feed point of a particular antenna are largest for adjacent longitudinal channels. Here, the +/- 10 degrees phase shift and +/- 30% voltage change were observed if the reference channel (i.e., the disturbed channel) and disturbing channel are equally powered. The changes eminently increased to -30 degrees to + 100 degrees phase shift and -80% to +50% voltage change if the reference channel is fed with much lower power (four to eight-fold) than the disturbing channel. The disturbance from distant channels is less but still significant, reaching shifts of -10 degrees to +50 degrees and -50% to +20%, respectively. Using Pawsey loops instead of the original ferrite rings in the SIGMA-Eye network, the efficacy of the baluns was improved by a more than a factor of 4. Using an LC matching network, dependencies on frequency and external arrangements can be reduced significantly. Applying a power divider circuit, the coupling between antennas combined to one channel is considerably diminished (down to <-25 dB). CONCLUSION: Coupling between resonators (pairs of antennas including the matching network) reduces the control of the SIGMA-Eye applicator, i.e., it causes deviations between the selection of forward parameters at the amplifier and the total actual parameters in the feed points of the antennas. Modified transformation networks can improve the control, in particular by reducing sheath currents and asymmetries. There is a linear but variable relationship between selected (amplifiers) and actually given (feed points) parameters. This linear mapping (described by a matrix) and its characteristics need further investigation.

Hyperthermia, Induced↗

PubMed2000

Preoperative radiochemotherapy in locally advanced or recurrent rectal cancer: regional radiofrequency hyperthermia correlates with clinical parameters.

PURPOSE: Preoperative radiochemotherapy (RCT) is a widely used means of treatment for patients suffering from primary, locally advanced, or recurrent rectal cancer. We evaluated the efficacy of treatment due to additional application of regional hyperthermia (HRCT) to this conventional therapy regime in a Phase II study, employing the annular phased-array system BSD-2000 (SIGMA-60 applicator). The clinical results of the trial were encouraging. We investigated the relationship between a variety of thermal and clinical parameters in order to assess the adequacy of thermometry, the effectiveness of hyperthermia therapy, and its potential contribution to clinical endpoints. METHODS AND MATERIALS: A preoperative combination of radiotherapy (1.8 Gy for 5 days a week, total dose 45 Gy applied over 5 weeks) and chemotherapy (low-dose 5-fluorouracil [5-FU] plus leucovorin in the first and fourth week) was administered to 37 patients with primary rectal cancer (PRC) and 18 patients with recurrent rectal cancer (RRC). Regional hyperthermia (RHT) was applied once a week prior to the daily irradiation fraction of 1.8 Gy. Temperatures were registered along rectal catheters using Bowman thermistors. Measurement points related to the tumor were specified after estimating the section of the catheter in near contact with the tumor. Three patients with local recurrence after abdominoperineal resection, had their catheters positioned transgluteally under CT guidance, where the section of the catheter related to the tumor was estimated from the CT scans. Index temperatures (especially T(max), T(90)) averaged over time, cumulative minutes (cum min) (here for T(90) > reference temperature 40.5 degrees C), and equivalent minutes (equ min) (with respect to 43 degrees C) were derived from repetitive temperature-position scans (5- to 10-min intervals) utilizing software specially developed for this purpose on a PC platform. Using the statistical software package SPSS a careful analysis was performed, not only of the variance of thermal parameters with respect to clinical criteria such as toxicity, response, and survival but also its dependency on tumor characteristics. RESULTS: The rate of resectability (89%) and response (59%) were high for the PRC group, and a clear positive correlation existed between index temperatures (T(90)) and thermal doses (cum min T(90) >/= 40.5 degrees C). Even though the overall 5-year survival was encouraging (60%) and significantly associated with response, there was no statistically significant relationship between temperature parameters and long-term survival for this limited number of patients. However, nonresectable tumors with higher thermal parameters (especially cum min T(90) >/= 40.5 degrees C) had a tendency for better overall survival. We found even higher temperatures in patients with recurrences (T(90) = 40.7 degrees C versus T(90) = 40.2 degrees C). However, these conditions for easier heating did not involve a favorable clinical outcome, since surgical resectability (22%) and response rate (28%) for the RRC group were low. We did not notice any other dependency of thermal parameters to a specific tumor or patient characteristics. Finally, neither acute toxicity (hot spots) induced by hyperthermia or RCT nor perioperative morbidity were correlated with temperature-derived parameters. Only a higher probability for the occurrence of hot spots was found during treatment with elevated power levels. CONCLUSION: In this study with two subgroups, i.e., patients with PRC (n = 37) and RRC (n = 18), there exists a positive interrelationship between thermal parameters (such as T(90), cum min T(90) >/= 40,5 degrees C) and clinical parameters concerning effectiveness. Additional hyperthermia treatment does not seem to enhance toxicity or subacute morbidity. Procedures to measure temperatures and to derive thermal parameters, as well as the hyperthermia technique itself appear adequate enough to classify heat treatments in

Age Factors↗

PubMed2000

Clinical evaluation and verification of the hyperthermia treatment planning system hyperplan.

PURPOSE: A prototype of the hyperthermia treatment planning system (HTPS) HyperPlan for the SIGMA-60 applicator (BSD Medical Corp., Salt Lake City, Utah, USA) has been evaluated with respect to clinical practicability and correctness. MATERIALS AND METHODS: HyperPlan modules extract tissue boundaries from computed tomography (CT) images to generate regular and tetrahedral grids as patient models, to calculate electric field (E-field) distributions, and to visualize three-dimensional data sets. The finite difference time-domain (FDTD) method is applied to calculate the specific absorption rate (SAR) inside the patient. Temperature distributions are calculated by a finite-element code and can be optimized. HyperPlan was tested on 6 patients with pelvic tumors. For verification, measured SAR values were compared with calculated SAR values. Furthermore, intracorporeal E-field scans were performed and compared with calculated profiles. RESULTS: The HTPS can be applied under clinical conditions. Measured absolute SAR (in W/kg), as well as relative E-field scans, correlated well with calculated values (+/-20%) using the contour-based FDTD method. Values calculated by applying the FDTD method directly on the voxel (CT) grid, were less well correlated with measured data. CONCLUSION: The HyperPlan system proved to be clinically feasible, and the results were quantitatively and qualitatively verified for the contour-based FDTD method.

Algorithms↗

PubMed2000

Effect of adding Mycophenolate mofetil in paediatric renal transplant recipients with chronical cyclosporine nephrotoxicity.

Cyclosporine (CyA) has made a great impact on 1-year allograft survival, however, after years, renal function deteriorates, possibly due to chronic toxicity. Recently, Mycophenolate mofetil (MMF) was introduced as a non-nephrotoxic immunosuppressant that might be effective in chronical transplant arteriolopathy. We therefore started MMF at a dose of 600 mg/m2 b. i. d. in 18 pediatric renal transplant recipients (10.8 +/- 3.9 (SD) years of age at transplantation, 11/18 with a history of rejections) with biopsy-proven chronic arteriolopathy and other signs of CyA toxicity at a mean follow up time of 6.2 +/- 2.7 (range 2.3-11.8) years after transplantation. One month prior to conversion, mean serum creatinine was 171 +/- 96 micromol/l, lower than at the time of conversion (188 +/- 100 micromol/l, P = 0.003, paired t-test). At last follow-up (median 13.7 months, range 5.0 to 25.0 months) after conversion, mean serum creatinine decreased significantly to 127 +/- 69 micromol/l (P = 0,0003, paired t-test). The CyA dosage was reduced from a mean of 150 +/- 39 mg/ m2 per day to 59 +/- 13 mg/m2 per day in 7 patients, and CyA was discontinued in 11 patients after a median period of nine months (range 1-18 months). After a median period of 21 days, a pharmacokinetic profile was performed in all patients. The mean MMF dose was 1117 +/- 319 mg/m2 per day (range 675-1774 mg/m2 per day). The mean Mycophenolic acid (MPA) trough concentration was 4.0 +/- 2.0 microg/ml, range 1.4-7.9 microg/ml. Mean 12 h MPA AUC was 70.6 +/- 28.1 (range 31.9-127) microg x h/ml. Except for one patient with diarrhea associated with a high AUC, and for one patient with a steroid-sensitive rejection episode after 566 days, no other patient experienced side effects or a rejection episode. Prednisolone was left unaltered at 2-4 mg/m2 per day. We conclude that MMF allows safe reduction of CyA with markedly better graft function, suggesting that chronical CyA-toxicity partially accounts for deteriorating allograft function.

Adolescent↗

PubMed2000

Effect of ramipril on ambulatory blood pressure and albuminuria in renal hypertension.

Inhibition of the angiotensin-converting enzyme (ACE) exerts a renoprotective effect in adult patients with chronic kidney disease. We evaluated prospectively changes in blood pressure (BP), protein excretion and renal function after administration of the long-acting ACE inhibitor ramipril as monotherapy during 6 months in 14 moderately hypertensive children aged 5-18 years with various nephropathies. Four patients initially had a decreased glomerular filtration rate (GFR below 60 ml/min/1.73 m2). BP was evaluated by ambulatory 24-h monitoring. After 2 weeks of treatment by oral ramipril (1.5 mg/m2 once daily), mean values of systolic and diastolic 24-h ambulatory BP fell by more than 5 mmHg in nine patients. In eight patients the dose was doubled. At the end of the study systolic BP was below the 95th percentile in 9 and diastolic BP in 13 patients. The initially reduced nocturnal dip increased significantly. Of 11 patients with an increased albumin excretion (median 1.3 g/g creatinine), 6 responded to ramipril by a median reduction of 78% (range 24-83%), whilst in 5 albuminuria increased (median +19%). GFR was well preserved and no other adverse effects from the drug were noted. The study demonstrates that ramipril is an efficacious antihypertensive agent in children with renal hypertension. It is well tolerated, even in mild renal insufficiency. In addition, the drug has a persistent antiproteinuric action in about half of the patients contributing to conserve renal function.

Adolescent↗

PubMed1999

Scanning E-field sensor device for online measurements in annular phased-array systems.

PURPOSE: A measurement device for noninvasive and simultaneous control of antennas during regional radiofrequency (rf) hyperthermia and, subsequently, the estimation of the power distribution in the interior of patients are essential preconditions for further technological progress. Aiming at this, the feasibility of an electro-optical electric field sensor was investigated during clinical rf hyperthermia. MATERIAL AND METHODS: The electro-optical electric field (E-field) sensor is based on lithiumniobate crystals and the Mach-Zehnder interferometer structure, and was tested in an earlier phantom study. For this study, a mechanical scanning device was developed allowing the registration of the E-field during clinical application. Data were recorded along a curve in the water bolus of the SIGMA 60 applicator of the annular phased-array system BSD-2000 (BSD Medical Corp., Salt Lake City, UT) close to the base points of the flat biconical dipole antennas. The results were compared with modeling calculations using the finite-difference time-domain (FDTD) method. For the latter, different antenna models were assumed. For systematic registration of the E-field curves in amplitude and phase, we employed an elliptical lamp phantom with fat-equivalent ring (filled with saline solution) and an elliptical polyacrylamide phantom with acrylic glass wall. Further measurements were carried out during the treatment of 5 patients with 20 hyperthermia treatments. RESULTS: Data of both phantom and patient measurements can be satisfactorily described by the FDTD method, if the antenna model is refined by taking into account the conical form of the dipoles and the special dielectric environment of the feeding point. Phase deviations can be entered ex posteriori for correction in the calculation algorithm. A comparison of amplifier power measurement (forward and backward power) and bolus E-field scans near the antenna base points demonstrates that E-field measurements between antennas and patient are a necessity for the appropriate characterization of antenna radiation properties. These measurements are sensitive to variations of the lossy medium in position and shape, and can be correctly predicted with current models. However, the differences between different patients are moderate and unspecific in both calculations and measurements, with fluctuations at maximum of 30 degrees in phases and 40% in amplitudes. CONCLUSIONS: The measurement method presented here turned out to be a practical tool for online registration of E-fields in phases and amplitudes along arbitrary curves in a water bolus or phantom. It can be utilized to evaluate antenna design and modeling calculations and leads, thus, to a better understanding of complicated multiantenna systems. In clinical routine, it can be employed as input for patient-specific hyperthermia planning and, finally, for the realization of online control with subsequent optimization of the power distribution in the patient.

Algorithms↗

PubMed1999

Diagnostic sensitivity of serum cystatin for impaired glomerular filtration rate.

Recently, the reciprocal of cystatin C (Cys-C), a non-glycosylated 13-kilodalton protein that is produced by all investigated nucleated cells, was found to correlate closely with glomerular filtration rate (GFR). In order to determine the diagnostic validity in children for the detection of impaired GFR, venous blood samples from 381 children (aged 1.7-18 years) with various renal pathology referred for 51Cr-EDTA clearance investigations were obtained for measurement of Cys-C as well as beta2-microglobulin (beta2-MG) and serum creatinine. Two hundred and sixteen children with clearance values >90 ml/min per 1.73 m2 constituted a control group, with a normal GFR. In the control group, Cys-C values were normally distributed with a mean of 0.94+/-0.27 mg/l and an upper reference limit (97.5th percentile) of 1.47 mg/l. In all children, there was a positive correlation between 51Cr-EDTA clearance and the reciprocal of Cys-C (r=0.64, P<0.0001), beta2-MG (r=0.59, P<0.0001), creatinine (r=0.55, P<0.0001), and the height/creatinine ratio (r=0.73, P<0.0001). Receiver-operating characteristics analysis showed that there were no significant differences between these three parameters for discriminating between patients with normal and reduced GFR, although there was a tendency towards the best diagnostic sensitivity of the GFR estimate according to the Schwartz formula. We conclude that for the detection of mildly impaired GFR, a full clearance study cannot be replaced by measurement of serum Cys-C or beta2-MG concentrations.

Adolescent↗

PubMed1999

Long-term prognosis of hemolytic uremic syndrome and effective renal plasma flow.

The long-term prognosis of diarrhea-associated hemolytic uremic syndrome (D+ HUS) was evaluated in a cohort of 127 of 149 children who had survived the acute phase. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were estimated by serial (51)Cr-EDTA and (123)iodine-hippurate clearances. All children had acute renal failure during the initial phase and 74% of patients were dialyzed. During the 1st year, mean GFR and ERPF increased continuously until a plateau was reached. In the 2nd year after the diagnosis of HUS, GFR was below 80 and ERPF below 515 ml/min per 1. 73 m(2) in 16% and 47% of patients, respectively. At the end of a median follow-up of 5.0 (range 2.0-13.2) years, the proportion of children with renal sequelae such as proteinuria >/=300 mg/l, hypertension, or a GFR <80 ml/min per 1.73 m(2) was 23%. Anuria of more than 7 days' duration and hypertension during the acute phase were statistically significant risk factors for an unfavorable outcome. A reduced ERPF in the 2nd year was found in 93% of patients with sequelae. Mean filtration fraction (SD) in these patients was 0. 26 (+/-0.07) versus 0.19 (+/-0.05) in patients without sequelae (P<0. 0001). These data suggest that loss of nephrons during the acute phase may implicate hyperfiltration in the residual functioning kidney mass leading to progressive renal disease. ERPF in the 2nd year after D+ HUS may serve as an excellent parameter to detect patients with a high risk of an unfavorable long-term outcome.

Child↗

PubMed1998

Rationale for using invasive thermometry for regional hyperthermia of pelvic tumors.

PURPOSE: Invasive thermometry for regional hyperthermia is time-consuming, uncomfortable, and risky for the patient. We tried to estimate the benefit/cost ratio of invasive thermometry in regional hyperthermia using the radiofrequency system BSD-2000. METHODS AND MATERIALS: We evaluated 182 patients with locally advanced pelvic tumors that underwent regional hyperthermia. In every patient a tumor-related temperature measurement point was obtained either by invasive or minimally invasive catheter measurement tracks. In the earlier period for every patient an intratumoral measurement point was decided as obligatory and intratumoral catheters were implanted intraoperatively, CT guided, or under fluoroscopy. In the later period, invasive thermometry often was avoided, if a measurement point in or near the tumor was reached by an endoluminally inserted catheter (rectal, vaginal, cervical, urethral, or vesical). For every patient side effects and complications referred to thermometry were evaluated and compared with the potential benefit of the invasively achieved temperature data. The suitability of endolumimally registered temperatures is analyzed to estimate local feasibility (specific absorption rate achieved) and local effectiveness (thermal parameters correlated with response). RESULTS: In 74 of 182 patients invasive thermometry was performed, at most CT-guided for soft tissue sarcomas and rectal recurrences. In 14 of 74 (19%) side effects such as local inflammation, pain, or abscess formation occurred that enforced removal of the catheter. However, local problems were strongly correlated with the dwell time of the catheter and nearly never occurred for dwell times less than 5 days. Fortunately, no fatal complications (e.g., bleeding or perforation) occurred during or after implantation which could be attributed to the invasive thermometry procedure. Endoluminal tumor-related temperature rises per time unit (to estimate power density) were correlated with intratumoral rises at the same patients (where both measurements were available). For a subgroup of patients pooled in two Phase II studies with rectal (n = 37) and cervical (n = 18) carcinomas thermal parameters derived from endoluminal measurements were correlated with response or local control, resp. CONCLUSIONS: If a tumor-related endoluminal temperature measurement point is available, additional invasive thermometry gives no further information to improve the power deposition pattern. For primary rectal and cervical cancer, and probably as well for prostate, bladder and anal cancer, endoluminal measurements are suitable to estimate local feasibility and effectiveness. Therefore, invasive thermometry is dispensable in the majority of patients. In some selected cases, temperature measurement in the tumor center is required to estimate the maximum temperature. In those cases, dwell time of catheters should be minimized--and it should be considered to perform invasive thermometry at the beginning (one or two heat treatments).

Catheterization↗