Biomedical subjects

P Wust

Publications and source records attributed to P Wust.

At least 55 records · Page 3Linked to original sources

PubMed2000

Electric field distributions in a phased-array applicator with 12 channels: measurements and numerical simulations.

In this paper we examine the SIGMA-Eye hyperthermia applicator (BSD Medical Corp., Salt Lake City, Utah 84119) with respect to the control of electric field distributions. This applicator is equipped with 12 pairs of antennas fed by 12 amplifiers, allowing the individual adjustment of phase and power for each of them. Measurements were conducted using phantoms with well-defined electrical properties. Specific electro-optical sensors, capable of measuring both electric field amplitudes and phases, have been developed, and a system for data acquisition and analysis has been set up. In its initial state the applicator appeared not to be satisfactorily matched at 100 MHz for the phantom used, with return losses up to 20% in power. By tuner readjustments we achieved values below 5%. For various settings of the amplifiers' control parameters we measured field distributions, both in the phantom and in the surrounding water bolus. The experimental results were compared with numerical simulations based on finite difference and finite element methods. Measured and calculated electric fields exhibit deviations of 10% on average, allowing, in principle, a satisfactory prediction of fields by numerical simulations or as well by on-line measurements at selected locations of the applicator at antenna proximity. However, to obtain this satisfactory agreement a modification of the control parameters in the calculations (phases and amplitudes in the feed points of the antennas) was necessary. The origin of these problems is mainly attributed to cross-talk phenomena and other characteristics of the transforming network, which need to be scrutinized further for a full understanding.

Computer Simulation↗

PubMed2000

Pre-operative staging of cervical cancer: comparison of magnetic resonance imaging (MRI) and computed tomography (CT) with histologic results.

Thirty-two patients with histologically confirmed cervical carcinoma were preoperatively investigated using MRI; in addition, a CAT-scan was performed on 15 of these patients. The diagnostic results using both modalities were compared with the histological findings (after hysterectomy according to Wertheim-Meigs, including lymph node dissection in the pelvic and, in part, in para-aortal regions). Determination of tumour volume was possible with high accuracy using MRI. Accuracy in assessing the parametria was 86%, vagina 90%, bladder and rectum 97%. The shortcoming of MRI is still the detection of infiltrated lymph nodes. The accuracy of 69% achieved for lymph nodes is equal to results with computed tomography. The general accuracy for our patients in staging was 81% for MRI versus 47% for CT. MRI-based diagnosis enables us to determine a correct tumour staging preoperatively, and is therefore very helpful in planning an adequate therapy. If MRI were used more widely it would contribute to simplification and shortening of the preoperative diagnostic procedure in patients with cervical carcinoma.

Adult↗

PubMed2000

[Preoperative radiochemotherapy of rectal carcinoma. Current status].

BACKGROUND: In locally advanced rectal cancer RO-resectability is limited and outcome is combined with a relatively high rate of local recurrences. This paper focuses on experiences with preoperative (neo-)adjuvant therapy and the potential improvement of treatment results. PATIENTS AND METHODS: Different therapy regimen were demonstrated under consideration of therapeutic induced side effects, treatment response (downstaging) in relation to resectability, recurrence free and overall survival. RESULTS: The rate of treatment induced toxicity of preoperative radio-(chemo-)therapy in locally advanced rectal cancer is acceptable with regard to the obtained treatment results. Through the pretreatment it was possible to gain a downstaging by nearly 60%. The frequency of local recurrence is significantly reduced by preoperative radiotherapy, and combined radiochemotherapy possibly increases the disease free survival. In what extent the results of treatment could be improved through hyperthermia and/or consecutive postoperative chemotherapy, is proved at present. CONCLUSIONS: Preoperative radio-(chemo-)therapy should be increasingly introduced into the standard treatment regimen of locally advanced rectal cancer and has to be optimised within the scope of further studies.

Disease-Free Survival↗

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

Hyperthermia for treatment of rectal cancer: evaluation for induction of multidrug resistance gene (mdr1) expression.

Environmental stress factors, such as heat, may induce multidrug resistance gene (mdr1) expression, which could result in the disadvantageous multidrug resistance (MDR) phenotype. To evaluate this possibility in a clinical situation, we investigated mdr1 gene expression in patients with locally advanced rectal cancer who underwent preoperative radio-chemo-thermo-therapy (RCTT). Patients were classified into groups according to the treatment schedule of RCTT vs. radio-chemo-therapy (RCT) without hyperthermia (control group). Expression of the mdr1 gene was analyzed in tumors and normal rectal tissues prior to and post-treatment (RCTT or RCT, respectively) by means of semi-quantitative and quantitative reverse transcription-polymerase chain reaction (RT-PCR). The data were correlated with therapeutic response and survival parameters. Based on our evaluation criteria, in 2 of 19 tumors of the RCTT group, mdr1 gene expression was increased more than 2-fold; in 3 of 19 tumors of this group, however, mdr1 expression was decreased more than 2-fold. In the patient control group, levels of mdr1 gene expression were reduced in 2 of 8 tumors. Thus, hyperthermia combined with RCT (RCTT) in comparison with RCT alone does not lead to an increase in mdr1 gene expression in patients with locally advanced rectal cancer within the preoperative treatment schedule. The risk of inducing the classical multidrug resistance phenotype by hyperthermia was thus minimal in this clinical setting. Subsequent adjuvant chemotherapy should thus not be hindered.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

Whole body hyperthermia: a secure procedure for patients with various malignancies?

OBJECTIVE: To establish the safety of systemic Cancer Multistep Therapy (sCMT) including whole body hyperthermia, by means of hemodynamic, laboratory and clinical investigations. DESIGN: Prospective study. SETTING: University clinic. PATIENTS: 12 patients with various cancers (with sCMT), a second group of 20 patients with colorectal carcinoma treated with chemotherapy (without sCMT). INTERVENTIONS: 25 treatments with sCMT for 60 min at 41.8 degrees C (including chemotherapy) were given in addition to induced hyperoxemia and hyperglycemia under general anesthesia. MEASUREMENTS AND RESULTS: Invasive monitoring of systemic and pulmonary hemodynamics as well as pulmonary gas exchange was used at 37 degrees C, 40 degrees C, 41.8 degrees C and 39 degrees C. In addition, laboratory parameters were measured before and within 4 days of therapy. At 41.8 degrees C, invasive monitoring showed characteristic signs of hyperdynamic circulation. In addition, right-to-left shunt, oxygen consumption, oxygen delivery and lactate levels were significantly different from pretreatment values. At the end of therapy, lactate levels and the extravascular lung water index increased, whereas all other parameters showed a clear tendency to return to initial values. Within the first day after sCMT, we measured a slight but significant reversible increase in serum creatinine compared to pretreatment values, but found no significant alterations of other chemical parameters. Between the sCMT group and controls, there was only a temporary significant difference in aspartate aminotransferase levels 2 days after therapy. CONCLUSIONS: sCMT, including whole body hyperthermia, accompanied by suitable anesthesiological management and monitoring, does not lead to any serious or sustained organ dysfunction and can therefore be regarded as a safe therapy.

Adult↗

PubMed1999

Accuracy of endorectal ultrasound after preoperative radiochemotherapy in locally advanced rectal cancer.

OBJECTIVES: Factors limiting the accuracy of endorectal ultrasound in staging, locally advanced primary rectal cancer after preoperative neoadjuvant radiochemotherapy (RCT) were evaluated. METHODS: Patients (n = 84) with initial locally advanced rectal cancer (uT3/uT4) undergoing R0 resection were investigated after preoperative treatment that combined radiotherapy up to 45 Gy with two cycles of chemotherapy (5-FU and leucovorin on d 1-5 and 22-28). At 4 to 6 weeks after completion of RCT and before tumor resection, preoperative endoluminal ultrasound was performed. RESULTS: The accuracy to predict the depth of tumor infiltration (T-category) was found to correlate with downstaging. The T-category was correctly staged before surgery in 15 of the 51 responders (29%) and in 27 of 33 nonresponders (82%), whereas misinterpretation occurred in 36 of the responders (71%) and in 6 of the nonresponders (18%) (p < 0.001). Neither tumor distance from anal verge nor tumor location correlated with the staging accuracy. Lymph node involvement was correctly assessed in 48 patients (57%). Wall invasion was correctly ascertained in 42 patients (50%), with under estimation in 11 patients (13%) and overestimation in 31 patients (37%). CONCLUSIONS: After radiochemotherapy, endosonography does not provide a satisfactory accuracy for preoperative staging of rectal cancer. New interpretation and diagnostic criteria are needed for the prediction of treatment response.

Adenocarcinoma↗

PubMed1999

Fast spectroscopic imaging for non-invasive thermometry using the Pr[MOE-DO3A] complex.

The praseodymium complex of 10-(2-methoxyethyl)-1,4,7,10-tetraaza-cyclododecane-1,4,7-tr iacetate) was evaluated as a temperature-sensitive contrast agent using the temperature dependence (approximately 0.12 ppm degrees C(-1)) of the chemical shift of its methoxy side group signal. Pr[MOE-DO3A] was employed in combination with spectroscopic imaging (SI) methods for the determination of spatially resolved 2D and 3D temperature distributions in phantoms. Conventional SI and fast echo planar SI sequences (EPSI) were implemented on a 4.7 T MR imaging system fulfilling the demands for non-invasive thermometry (NIT) with respect to thermal and temporal resolution, being <1 degree C and <20 s total measuring time, respectively. The sequences are based on a fast spin echo SI method taking into account the very short relaxation times of the Pr complex methoxy group (T1 = 28 ms, T2 = 13 ms) and its chemical shift difference (-24 ppm) from water. Calibration curves were measured in a uniformly heated water phantom and 2D SI methods were applied to dynamic heating experiments. The average differences between the temperatures measured via fibreoptic thermometer and those derived from the spectroscopic methods were < or =0.2 degrees C. Furthermore, 3D EPSI experiments with a 16 x 16 x 16 matrix size yielded temperature measurements within 17 s from voxels of size 3 x 3 x 3 mm3.

Calibration↗

PubMed1999

Comparison of four magnetic resonance methods for mapping small temperature changes.

Non-invasive detection of small temperature changes (< 1 degree C) is pivotal to the further advance of regional hyperthermia as a treatment modality for deep-seated tumours. Magnetic resonance (MR) thermography methods are considered to be a promising approach. Four methods exploiting temperature-dependent parameters were evaluated in phantom experiments. The investigated temperature indicators were spin-lattice relaxation time T1, diffusion coefficient D, shift of water proton resonance frequency (water PRF) and resonance frequency shift of the methoxy group of the praseodymium complex (Pr probe). The respective pulse sequences employed to detect temperature-dependent signal changes were the multiple readout single inversion recovery (T One by Multiple Read Out Pulses; TOMROP), the pulsed gradient spin echo (PGSE), the fast low-angle shot (FLASH) with phase difference reconstruction, and the classical chemical shift imaging (CSI). Applying these sequences, experiments were performed in two separate and consecutive steps. In the first step, calibration curves were recorded for all four methods. In the second step, applying these calibration data, maps of temperature changes were generated and verified. With the equal total acquisition time of approximately 4 min for all four methods, the uncertainties of temperature changes derived from the calibration curves were less than 1 degree C (Pr probe 0.11 degrees C, water PRF 0.22 degrees C, D 0.48 degrees C and T1 0.93 degrees C). The corresponding maps of temperature changes exhibited slightly higher errors but still in the range or less than 1 degree C (0.97 degrees C, 0.41 degrees C, 0.70 degrees C, 1.06 degrees C respectively). The calibration results indicate the Pr probe method to be most sensitive and accurate. However, this advantage could only be partially transferred to the thermographic maps because of the coarse 16 x 16 matrix of the classical CSI sequence. Therefore, at present the water PRF method appears to be most suitable for MR monitoring of small temperature changes during hyperthermia treatment.

Body Temperature↗

PubMed1999

Visualization and registration of three-dimensional E-field distributions in annual-phased-array applicators.

A testing system is presented allowing registration, digitization, and evaluation of three-dimensional power distributions rendered by annular-phased-array applicators in homogeneous liquid media. The system is based on a lamp phantom originally developed to visualize power distributions. Now the brightness distribution is registered via a charge-coupled device camera and transferred to a PC-based evaluation system outside the shielding room. An appropriate mechanical coupling of camera and sensor matrix probing the phantom was built in order to keep optical image conditions constant under movement. For visualization and evaluation commercially customized software was employed. The evaluation of the system shows the linearity between sensor signal and power density magnitude to be sufficient for evaluation and graphical representation of three-dimensional data sets. In a first practical application the testing system was employed to evaluate dependencies of power distributions as a function of frequency and phase settings on temperatures and, subsequently, the relevance of those results for clinical hyperthermia in a SIGMA-60 applicator (BSD-2000 system). Now, the system is ready to evaluate more complex multiantenna array applicators like the SIGMA-Eye applicator. The measuring system is particularly suitable for a fast comparison of APA applicators applied for a homogeneous medium. Implications for heterogeneous structures (like in patients) are then possible via modeling calculations.

Calibration↗

PubMed1999

Preoperative treatment of rectal cancer with radiation, chemotherapy and hyperthermia: analysis of treatment efficacy and heat-shock response.

Preoperative treatment of locally advanced rectal cancer with radiation, chemotherapy and hyperthermia is analyzed with regard to heat-shock response. In 23 patients with locally advanced rectal cancer (uT3/uT4), hyperthermia was administered in combination with radiotherapy and chemotherapy. In parallel, the effect of the treatment on levels of the heat-shock proteins HSP27 and inducible HSP70 in tumors and surrounding tissues was investigated by Western blotting. The patients' sera were also examined for autoantibodies against HSPs. HSP27 and inducible HSP70 were detected in most rectal tumors and surrounding tissues before and after treatment. HSP27 and inducible HSP70 levels had changed in 10 tumors after treatment. However, prior to treatment, there existed an unexpected diversity in HSP levels in the tumors and surrounding tissue. Hyperthermia doses in cumulative minutes for which 90% of the tumor is above the reference temperature (cum min T90 > or = 15 min) led to increased survival and response compared to that of a control group of patients treated without or with low-dose hyperthermia (cum min T90 < 15 min). However, there was no correlation to different expression of the HSPs. Hyperthermia as used in this setting does not lead to any sustained expression of HSPs in either the tumor or the surrounding tissue.

Antibodies↗

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↗

PubMed1998

Radiochemotherapy and hyperthermia in the treatment of rectal cancer.

We evaluated the use of regional hyperthermia with radio-chemotherapy in a phase I/II study on locally advanced rectal carcinomas. Thirty-four patients with primary advanced (stage T3/T4) rectal carcinomas (24 patients) or recurring rectal carcinomas (6 patients) were treated using preoperative radiochemo-thermotherapy. Initial tumour staging was carried out clinically (degree of fixation) and using endorectal ultrasonography and CT. Radiotherapy was carried out with the patient prone (on a belly board) at 5 x 1.8 Gy per week up to 45 Gy at the reference point. 5-Fluorouracil (300-500 mg/m2) was administered with low-dose leucovorin (50 mg) on days 1-5 and 22-26. Patients were treated with regional hyperthermia each week prior to radiotherapy, using the Sigma-60 ring of the BSD-2000 system. Temperature/position curves and temperature/time curves were recorded via endocavitary catheters (tumour contact, bladder, vagina). Following endosonographic and clinical restaging, the operation was carried out 4-6 weeks after the end of preoperative therapy. In cases where tumours were unresectable, a boost of up to 60 Gy was given. Twenty-three of the 34 patients (68%) proved to be curatively resectable. Of these patients, 70% were downstaged endosonographically during preoperative therapy. The actuarial survival rates among these patients were 85% (primary rectal cancer) and 60% (recurrences) at 30 months. All in all, the preoperative multimodal therapy was well tolerated, and premature termination was necessary in only two cases. The quality of temperature distribution (T90, cum min T90 > 40.5 degrees C) depends on the power level and relative power density. The response (particularly downstaging) correlates significantly with the quality parameters of the temperature distributions. This regimen proved practical and effective, with encouraging downstaging rates and local control rates.

Adult↗

PubMed1998

[Phase II study on preoperative radio-chemo-thermotherapy in locally advanced rectal carcinoma].

BACKGROUND: Recent studies show that preoperative radio-chemotherapy can increase resectability and local control of locally advanced rectal carcinomas. Additional regional hyperthermia might increase remission rates and tumor response. We therefore tested regional hyperthermia together with radio-chemotherapy in a phase-II study on locally advanced rectal carcinomas. PATIENTS AND METHODS: Thirty-seven patients with primary advanced stage uT3/T4 rectal carcinomas were treated with preoperative radio-chemo-thermo-therapy. The initial tumor depth was determined using endosonography, CT, and MRI. Radiotherapy was carried out in prone position (on a belly board) using standard techniques, with 5 x 1.8 Gy per week up to 45 Gy at the reference point. 5-Fluorouracil (300 to 500 mg/m2) was administered with low doses of leucovorin (50 mg) on days 1 to 5 and 22 to 28. The patients were treated with regional hyperthermia each week prior to radiotherapy and simultaneously with chemotherapy, using the Sigma 60 ring from the BSD-2000 system. Temperature/position curves and temperature/time curves were recorded in endocavitary (endorectal) catheters in tumor contact and as well in bladder and vagina. Following endosonographic restaging, the operation was carried out 4 to 6 weeks after the end of preoperative therapy and adjuvant chemotherapy continued in four cycles. In cases where tumors were non-resectable, a boost up to 64 Gy was aimed. RESULTS: Thirty-one of the 37 patients (84%) with primary carcinoma proved locally R0-resectable. In addition we had 1 R1-resection (3%) and 5 non-resectable tumors (13%). Among the resected tumors, 53% experienced a reduction of depth infiltration from the initial endosonographic stage during preoperative therapy. The actuarial survival rate after 4 years is 65% (free of progression 57%). The actuarial 4-year survival rate was particularly favorable for the group of responders. Overall, the preoperative multimodal therapy was well tolerated, and premature termination was only necessary in 1 case (3%). Grade III/IV toxicities in the intestine and skin were reduced as far as possible by field blockings and cooling of the perineal region. They occurred only in 5/37 patients (13%) at the intestine and in 6/37 patients (16%) at the skin. The thermal data were subjected to a statistical analysis. The quality of temperature distribution (T90, cum min T90 > or = 40.5 degrees C) depends on the power level and relative power density. The response (reduction of tumor size or depth infiltration) correlated significantly with quality parameters of the temperature distributions. This dependency is found as a trend for progression-free survival, too. CONCLUSIONS: Preoperative radio-chemo-thermo-therapy proved to be practical and effective, with encouraging remission rates and excellent local control rates. For this reason, a phase-III study to test regional hyperthermia has been initiated. At the same time, certain technical improvements are still under development for regional hyperthermia.

Adult↗

PubMed1998

Combined treatment of inoperable carcinomas of the uterine cervix with radiotherapy and regional hyperthermia. Results of a phase II trial.

AIM: The disappointing results for inoperable, advanced tumors of the uterine cervix after conventional radiotherapy alone necessitates improving of radiation therapy. Simultaneous chemotherapy or altered radiation fractionation, such as accelerated regimen, increase acute toxicity and treatment is often difficult to deliver in the planned manner. The purpose of this phase II study was to investigate the toxicity and effectiveness of a combined approach with radiotherapy and regional hyperthermia. PATIENTS AND METHODS: From January 1994 to October 1995 18 patients with advanced carcinomas of the uterine cervix were treated in combination with radiotherapy and hyperthermia. The patients were treated with 6 to 20 MV photons delivered by a linear accelerator in a 4-field-box technique to a total dose of 50.4 Gy in 28 fractions. In the first and fourth week 2 regional hyperthermia treatments were each applied with the Sigma-60 applicator from a BSD-2000 unit. After this a boost to the primary tumor was given with high-dose-rate iridium-192 brachytherapy by an afterloading technique with 4 x 5 Gy at point A to a total of 20 Gy and for the involved parametrium anterioposterior-posterioanterior to 9 Gy in 5 fractions. RESULTS: The acute toxicity was low and similar to an external radiotherapy alone treatment. No Grade III/IV acute toxicity was found. The median age was 47 years (range 34 to 67 years). In 16 of 18 patients a rapid tumor regression was observed during combined thermo-radiotherapy, which allowed the use of intracavitary high-dose-rate brachytherapy in these cases. Complete and partial remission were observed in 13 and 4 cases, respectively. One patient did not respond to the treatment. The median follow-up was 24 months (range 17 to 36 months). The local tumor control rate was 48% at 2 years. Median T20, T50 and T90 values were 41.7 degrees C (range 40.3 to 43.2 degrees C), 41.1 degrees C (range 39.2 to 42.5 degrees C) and 39.9 degrees C (range 37.7 to 41.9 degrees C), respectively. Cumulative minutes of T90 > 40 degrees C (Cum40T90) and cumulative minutes, which were isoeffective to 43 degrees C, were calculated (CEM43T90, CEM43T50, CEM43T20). CEM43T90 was found to be a significant parameter in terms of local tumor control for the 4 hyperthermia treatments (p = 0.019). CONCLUSIONS: This treatment modality has proved to be feasible and well tolerable. The rapid tumor shrinkage in the combined approach of radiotherapy with hyperthermia before beginning brachytherapy seems to be a good prerequisite for improving of the disappointing results in cure of advanced cancer of the uterine cervix.

Adult↗

PubMed1998

[Radiotherapy of exudative senile macular degeneration. A prospective controlled study].

UNLABELLED: Despite the successful therapy of subretinal neovascular membranes by laserphotocoagulation there are many problems to be overcome. In the case of subfoveolar neovascularization, photocoagulation leads to a sudden decrease in visual acuity. Recently radiotherapy is considered as an alternative. Complications and effectivity were evaluated in this prospective and randomized trial. The initial results are presented. PATIENTS AND METHODS: There are 76 patients (51 women, 25 men, average age 77.7 +/- 8.6 years) included in the prospective randomized study. All of them show subfoveolar neovascular membranes in FLA and a decrease in visual acuity between 0.05 and 0.5. They were randomly assigned to either the radiotherapy or the control group. Radiotherapy was done within 6 days by 6 x 2 Gy (6 MV photons). The follow-up was at 4 weeks, after 3 months, after 6 months and then every 6 months after the end of radiotherapy. On average the follow-up is at 15.1 months. RESULTS: Concerning age and visual acuity before therapy, the control group and the radiotherapy group were not significantly different. At 4 weeks after radiotherapy, visual acuity was 0.13 +/- 0.46 (LogMAR). After 12 months, visual acuity at a distance was 0.11 +/- 0.30 in the therapy group and 0.09 +/- 0.13 (P = 0.838) in the control group. Patients with a preoperative visual acuity better than 0.2 improved more after radiotherapy. Metamorphopsy improved in 75% of the therapy group. The following complications could be observed: In the control group 3 patients suffered subretinal bleeding, in the radiotherapy group 3 patients, respectively. CONCLUSIONS: At present, the follow-up is too short to recommend radiotherapy as a standard procedure in the case of subfoveolar neovascularization. The results in patients with a better preoperative visual acuity encourage us to continue this study.

Aged↗

PubMed1998

Evaluation of segmentation algorithms for generation of patient models in radiofrequency hyperthermia.

Time-efficient and easy-to-use segmentation algorithms (contour generation) are a precondition for various applications in radiation oncology, especially for planning purposes in hyperthermia. We have developed the three following algorithms for contour generation and implemented them in an editor of the HyperPlan hyperthermia planning system. Firstly, a manual contour input with numerous correction and editing options. Secondly, a volume growing algorithm with adjustable threshold range and minimal region size. Thirdly, a watershed transformation in two and three dimensions. In addition, the region input function of the Helax commercial radiation therapy planning system was available for comparison. All four approaches were applied under routine conditions to two-dimensional computed tomographic slices of the superior thoracic aperture, mid-chest, upper abdomen, mid-abdomen, pelvis and thigh; they were also applied to a 3D CT sequence of 72 slices using the three-dimensional extension of the algorithms. Time to generate the contours and their quality with respect to a reference model were determined. Manual input for a complete patient model required approximately 5 to 6 h for 72 CT slices (4.5 min/slice). If slight irregularities at object boundaries are accepted, this time can be reduced to 3.5 min/slice using the volume growing algorithm. However, generating a tetrahedron mesh from such a contour sequence for hyperthermia planning (the basis for finite-element algorithms) requires a significant amount of postediting. With the watershed algorithm extended to three dimensions, processing time can be further reduced to 3 min/slice while achieving satisfactory contour quality. Therefore, this method is currently regarded as offering some potential for efficient automated model generation in hyperthermia. In summary, the 3D volume growing algorithm and watershed transformation are both suitable for segmentation of even low-contrast objects. However, they are not always superior to user-friendly manual programs for contour generation. When the volume growing algorithm is used, the contours have to be postprocessed with suitable filters. The watershed transformation has a large potential if appropriately developed to 3D sequences and 3D interaction features. After all, the practicality and feasibility of every segmentation method critically depend on various details of the user software as pointed out in this article.

Algorithms↗

PubMed1998

Preoperative hyperthermia combined with radiochemotherapy in locally advanced rectal cancer: a phase II clinical trial.

OBJECTIVE: A prospective phase II study was performed to determine the feasibility and efficacy in terms of response rate, resectability, and morbidity in patients with locally advanced rectal cancer who received preoperative regional hyperthermia combined with radiochemotherapy (HRCT). SUMMARY BACKGROUND DATA: Recent studies suggest that preoperative radiochemotherapy in locally advanced rectal cancer can induce downstaging, but after resection the incidence of local recurrences remains high. Hyperthermia (HT) may add tumoricidal effects and improve the efficacy of radiochemotherapy in a trimodal approach. PATIENTS AND METHODS: Thirty-seven patients with histologically proven rectal cancer and T3 or T4 lesions, as determined by endorectal ultrasound and computed tomography, entered the trial. 5-Fluorouracil (300-350 mg/m2) and leucovorin (50 mg) were administered on days 1 to 5 and 22 to 26. Regional HT using the SIGMA 60 applicator (BSD-2000) was given once a week before radiotherapy (45 Gy with 1.8-Gy fractions for 5 weeks). Surgery followed 4 to 6 weeks after completion of HRCT. RESULTS: Preoperative treatment was generally well tolerated, with 16% of patients developing grade III toxicity. No grade IV complications were observed. The overall resectability rate was 32 of 36 patients (89%), and 31 resection specimens had negative margins (R0). One patient refused surgery. In 5 patients (14%), the histopathologic report confirmed no evidence of residual tumor (pCR). A partial remission (PR) was observed in 17 patients (46%). The survival rate after 38 months was 86%. In none of the patients was local recurrence detected after R0(L), but five patients developed distant metastases. CONCLUSION: Preoperative HRCT is feasible and effective and may contribute to locoregional tumor control of advanced rectal cancer, which is to be proven in an ongoing phase III trial.

Adenocarcinoma↗