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C Kolotas

Publications and source records attributed to C Kolotas.

At least 19 recordsLinked to original sources
PubMed2000

Reconstruction and navigation system for intraoperative brachytherapy using the flab technique for colorectal tumor bed irradiation.

PURPOSE: To present the development of a new navigation and reconstruction system based on an electromagnetic free-hand tracker and on CT imaging for treatment planning of intraoperative high-dose-rate brachytherapy (IORT-HDRB) in the sacral region. Our aim is to improve accuracy and to enable individualized treatment planning and dose documentation to be performed for IORT-HDRB using a flab technique. METHODS AND MATERIALS: The material consists of an electromagnetic 3D tracker system, a PC workstation with Microsoft Windows NT 4.0 operating system, and a recognition program for continuous speech. In addition, we designed an external reference system constructed of titanium and Perspex, which is positioned in the pelvis, and a special digitizer pen for reconstruction of the flab geometry. The flab design incorporates a series of silicon 10-mm-diameter spherical pellets. Measurements were made with a pelvic phantom in order to study the accuracy of the system. The reconstruction results are stored and can be exported via network or floppy to our different treatment planning systems. RESULTS: Our results for the reconstruction of a flab with six catheters and a total of 100 spherical pellets give mean errors in the range (2.5 +/- 0.6) mm to (3.5 +/- 0.8) mm depending on the positions of the pelvic phantom and transmitter relative to the operation table. These errors are calculated by comparing the reconstruction results of our system with those using a CT-based reconstruction of the flab geometry. For the accuracy of the navigation system for the pelvic phantom, we obtained mean errors in the range (2.2 +/- 0.7) mm to (3. 1 +/- 1.0) mm. CONCLUSIONS: The new system we have developed enables navigation and reconstruction within the surgical environment with a clinically acceptable level of accuracy. It offers the possibility of individualized treatment planning and effective documentation of the 3D dose distribution in IORT-HDRB using a flab technique.

Brachytherapy↗
PubMed2000

3D interstitial HDR brachytherapy combined with 3D external beam radiotherapy and androgen deprivation for prostate cancer. Preliminary results.

BACKGROUND: Evaluation of feasibility, tolerance and efficiency for a new 3D interstitial HDR brachytherapy technique combined with 3D external beam radiotherapy and androgen deprivation for prostate cancer. PATIENTS AND METHODS: Between January 1997 and August 1998 we treated 35 patients with stage cT1-3 N0 M0 prostate cancer. Thirty-two patients with a follow-up of 12 to 28 months (median: 18 months) were evaluated. After ultrasound-guided transrectal implantation of 4 non-parallel needles, CT based 3D brachytherapy treatment planning ("Offenbach system") was performed. All patients received 4 fractions brachytherapy using a fractional dose of 5 or 7 Gy. Time between each fraction was 14 days. After brachytherapy 3D external irradiation followed up to 39.6 or 45.0 Gy. All patients received androgen deprivation, starting 2 to 19 months before brachytherapy, ending 3 months after 3D external radiotherapy. RESULTS: Posttreatment PSA levels dropped to < 1.5 ng/ml in 29/32 patients (91%). In 25 patients PSA levels were < 0.5 ng/ml, in 4 patients 0.5 to 1.5 ng/ml. In 2 patients we noted biochemical relapse. Transrectal implantation was very well tolerated. Grade 3 acute urinary toxicity occurred in 1 patient. We noted no Grade 2 or higher acute gastrointestinal toxicity. One patient developed a Grade 3 late urinary toxicity. No patient showed late gastrointestinal side effects. All 140 dose-volume histograms for 3D HDR brachytherapy were analyzed. CONCLUSIONS: The new 3D HDR brachytherapy technique, combined with 3D external irradiation and androgen deprivation, is a feasible, so far well-tolerated and effective treatment in the short-time follow-up of median 18 months.

Adenocarcinoma↗
PubMed2000

Navigation system for interstitial brachytherapy.

PURPOSE: To develop a computed tomography (CT) based electromagnetic navigation system for interstitial brachytherapy. This is especially designed for situations when needles have to be positioned adjacent to or within critical anatomical structures. In such instances interactive 3D visualisation of the needle positions is essential. METHODS AND MATERIALS: The material consisted of a Polhemus electromagnetic 3D digitizer, a Pentium 200 MHz laptop and a voice recognition for continuous speech. In addition, we developed an external reference system constructed of Perspex which could be positioned above the tumour region and attached to the patient using a non-invasive fixation method. A specially designed needle holder and patient bed were also developed. Measurements were made on a series of phantoms in order to study the efficacy and accuracy of the navigation system. RESULTS: The mean navigation accuracy of positioning the 20.0 cm length metallic needles within the phantoms was in the range 2.0-4.1 mm with a maximum of 5.4 mm. This is an improvement on the accuracy of a CT-guided technique which was in the range 6.1-11.3 mm with a maximum of 19.4 mm. The mean reconstruction accuracy of the implant geometry was 3.2 mm within a non-ferromagnetic environment. We found that although the needles were metallic this did not have a significant influence. We also found for our experimental setups that the CT table and operation table non-ferromagnetic parts had no significant influence on the navigation accuracy. CONCLUSIONS: This navigation system will be a very useful clinical tool for interstitial brachytherapy applications, particularly when critical structures have to be avoided. It also should provide a significant improvement on our existing technique.

Brachytherapy↗
PubMed2000

Catheter autoreconstruction in computed tomography based brachytherapy treatment planning.

The aim of this study is to develop an automatic reconstruction of brachytherapy catheters using CT (computed tomography) data. Previously no such automatic facility has existed in any treatment planning software. To achieve this facility we have developed tools for the automatic reconstruction (which we term autoreconstruction) of plastic and metallic catheters. These algorithms overcome a number of difficulties which arise when a large number of catheters are present. These include situations with intersecting catheters and with loop techniques. The time required for the catheter reconstruction process using our autoreconstruction method is significantly reduced. The accuracy of our autoreconstruction is at least as high as the classical manual slice-by-slice method.

Algorithms↗
PubMed1999

Comparison of calibration procedures for 192Ir high-dose-rate brachytherapy sources.

PURPOSE: To compare the efficacy of different calibration procedures for 192Ir high-dose-rate (HDR) brachytherapy sources and to determine their suitability in clinical practice. In addition the manufacturer's calibration is compared with our experimental measurements so that the accuracy of the source strength on the manufacturer certificate which is supplied with each new 192Ir source can be accessed. METHODS AND MATERIALS: We compared three types of calibration system: well-type chambers (HDR-1000 and SDS), cylindrical phantom, and plate phantom. The total number of measurements we obtained was 365. The number of sources used for the calibration procedure comparison was 20 and the number used for comparison with the manufacturer's calibration was 46. This study was made during the period 1989-1997. Also, Physikalisch-Technische Bundesanstalt (PTB) calibrated one of our sources using their PTB protocol so that the results could be compared with our own. RESULTS: The sensitivity of each system on scattering from the room walls was studied. It was found that different minimum lateral distances from the walls were required for the different systems tested: 15 cm and 25 cm for the well-type chambers, 75 cm for the cylindrical phantom, and 13 cm for the plate phantom. The minimum thickness required to reach phantom scattering saturation for the plate phantom setup is 24 cm. The influence of the applicator material used in the calibration setup was found to be 1.7% for the stainless steel dosimetry applicator compared to the plastic 5F applicator. The accuracy of source positioning within the applicator can lead to dosimetric errors of +/-1.2% for the radial distance of 8.0 cm used with both solid phantoms. The change in the response for both well-type chambers was only 0.1% for changes in the source position within +/-7.5 mm around the response peak. Good agreement was found between all dosimetry systems included in our study. Taking the HDR-1000 well-type chamber results as a reference, we observed percentage root mean square (RMS) values of 0.11% for the SDS well-type chamber, 0.44% for the cylindrical, and 0.60% for the plate phantom setup. A comparison of our results using the cylindrical phantom with those of the manufacturer showed a percentage RMS value of 3.3% with a percentage fractional error range of -13.0% to +6.0%. The comparison of our calibration results with those of PTB gave deviations less than 0.4% for all systems. CONCLUSIONS: Our results have shown that with careful use of all calibration system protocols an accurate determination of source strength can be obtained. However, the manufacturer's calibration is not accurate enough on its own, and it should be mandatory for clinics to always measure the source strength of newly delivered 192Ir brachytherapy sources. The influence of the applicator material, metal or plastic, should always be taken into account.

Brachytherapy↗
PubMed1999

CT-Based interstitial HDR brachytherapy.

PURPOSE: Development, application and evaluation of a CT-guided implantation technique and a fully CT-based treatment planning procedure for brachytherapy. METHODS AND MATERIALS: A brachytherapy procedure based on CT-guided implantation technique and CT-based treatment planning has been developed and clinical evaluated. For this purpose a software system (PROMETHEUS) for the 3D reconstruction of brachytherapy catheters and patient anatomy using only CT scans has been developed. An interface for the Nucletron PLATO BPS treatment planning system for optimization and calculation of dose distribution has been devised. The planning target volume(s) are defined as sets of points using contouring tools and are used for optimization of the 3D dose distribution. Dose-volume histogram based analysis of the dose distribution (COIN analysis) enables a clinically realistic evaluation of the brachytherapy application to be made. The CT-guided implantation of catheters and the CT-based treatment planning procedure has been performed for interstitial brachytherapy and for different tumor sites in 197 patients between 1996 and 1997. RESULTS: The accuracy of the CT reconstruction was tested using first a quality assurance phantom and second, a simulated interstitial implant of 12 needles. These were compared with the results of reconstruction using radiographs. Both methods gave comparable results with regard to accuracy, but the CT based reconstruction was faster. Clinical feasibility was proved in pre-irradiated recurrences of brain tumors, in pretreated recurrences or metastatic disease, and in breast carcinomas. The tumor volumes treated were in the range 5.1 to 2,741 cm3. Analysis of implant quality showed a slightly significant lower COIN value for the bone implants, but no differences with respect to the planning target volume. CONCLUSIONS: The Offenbach system, incorporating the PROMETHEUS software for interstitial HDR brachytherapy has proved to be extremely valuable in routine clinical practice for many tumor sites. Our CT-guided implantation technique together with a fully CT-based planning system has enabled conformal brachytherapy treatment to become routine.

Brachytherapy↗
PubMed1999

[In Process Citation]

Intraoperative radiotherapy (IORT) is a new concept in the treatment of recurrent and primary advanced colorectal tumors. Between October 1994 and December 1997 27 patients (primary tumor: 8, first recurrent tumor: 12, second recurrent tumor: 7) received IORT (32 applications). Chemotherapy and percutaneous radiotherapy had already been given to all patients with advanced and recurrent colorectal tumors. The intraoperative irradiation was performed through HDR iridium afterloading. A flexible flab--individually adapted to the "tumor bed"--was used as applicator. The contact dose ranged from 10 to 15 Gy. The mean operation time (rectum resection: 5, rectum amputation: 14, debulking: 8) increased by 30 min on average. Eight patients had postoperative complications: perianal wound infections (3), sacrovesical fistulas (3), leakage of anastomosis (1) and neural ureter dysfunction (1). To date--on average 17.1 months (range: 3-33) after operation--13 patients are free of tumor recurrence or show stable disease. Ten patients--all of them had macroscopic residual tumor--have local tumor progression combined with good quality of life. Only 4 patients died (acute kidney failure, stroke, marasmus, systemic progression). The afterloading flab technique represents a technically simple, minimally harmful procedure in the therapy of colorectal tumor. Even when IORT with electrons is not feasible or the patients have already been irradiated, a higher radiation dose is possible. Given the demonstrated rate of local tumor recurrence, the afterloading flab technique seems to be a valuable treatment alternative to extended, high-risk resections. Long-term follow-ups will be necessary.

Journal Article↗
PubMed1999

New interstitial HDR brachytherapy technique for prostate cancer: CT based 3D planning after transrectal implantation.

We have developed a new interstitial HDR brachytherapy technique for the treatment of prostate cancer using CT based 3D planning after transrectal implantation of four non-parallel needles. CT based needle reconstruction, target definition, evaluation and documentation, including DVHs and 3D imaging, is a feasible, safe and well tolerated treatment concept.

Adenocarcinoma↗
PubMed1999

CT guided interstitial high dose rate brachytherapy for recurrent malignant gliomas.

This paper describes the technique and preliminary results of high dose rate (HDR) interstitial brachytherapy for recurrent grade III and grade IV gliomas. Although in the initial treatment of malignant gliomas brachytherapy has been shown to give better results than external beam therapy, this has previously always been with low dose rate (LDR) brachytherapy. Stereotactic frames are used for interstitial LDR brachytherapy but a CT image-guided technique does not require such a frame. The survival rates for our initial 53 patients do not significantly differ from LDR results. However, using HDR there are several advantages, including a much shorter treatment time with HDR than LDR and better patient comfort. HDR also allows better individualized optimization of the treatment than LDR.

Adult↗
PubMed1998

A conformal index (COIN) to evaluate implant quality and dose specification in brachytherapy.

PURPOSE: To propose a new index (COIN) that can be easily understood and computed to assess high dose rate (HDR) brachytherapy interstitial implant quality and dose specification and is an improvement on existing indexes. METHODS AND MATERIALS: The COIN index is based on an extension of dose-volume histograms and employs an analogous concept to that of cost-benefit analysis, which has already been applied to quality-of-life assessments for two alternative treatment protocols. The COIN index calculation methodology is shown for two cases: with and without critical structures. An analysis is given of dose distributions for two planning treatment volumes (PTV) of simple geometrical shape, applying both the rules of the Paris system and that of the "Offenbach" system. 40 patients who have received interstitial implants form the clinical material. With current HDR brachytherapy technology both for dose delivery, using remote afterloaders, and for three-dimensional (3D) treatment planning, it is now possible to relatively easily plan conformal brachytherapy treatments that would have been impossible with manual afterloading techniques and two-dimensional (2D) treatment planning. RESULTS: Examples of the use of the COIN index are presented for experimental and clinical data. CONCLUSIONS: The results show that COIN is a useful and practical index to improve the quality of treatment of interstitial brachytherapy implants. Further work will be undertaken with a larger population of implanted cancer patients and a subdivision of the results by treatment site.

Algorithms↗
PubMed1998

Application of the Monte Carlo integration (MCI) method for calculation of the anisotropy of 192Ir brachytherapy sources.

Source anisotropy is a very important factor in the brachytherapy quality assurance of high-dose rate (HDR) 192Ir afterloading stepping sources. If anisotropy is not taken into account then doses received by a brachytherapy patient in certain directions can be in error by a clinically significant amount. Experimental measurements of anisotropy are very labour intensive. We have shown that within acceptable limits of accuracy, Monte Carlo integration (MCI) of a modified Sievert integral (3D generalization) can provide the necessary data within a much shorter time scale than can experiments. Hence MCI can be used for routine quality assurance schedules whenever a new design of HDR or PDR 192Ir is used for brachytherapy afterloading. Our MCI calculation results are compared with published experimental data and Monte Carlo simulation data for microSelectron and VariSource 192Ir sources. We have shown not only that MCI offers advantages over alternative numerical integration methods, but also that treating filtration coefficients as radial distance-dependent functions improves Sievert integral accuracy at low energies. This paper also provides anisotropy data for three new 192Ir sources, one for the microSelectron-HDR and two for the microSelectron-PDR, for which data are currently not available. The information we have obtained in this study can be incorporated into clinical practice.

Algorithms↗
PubMed1997

[Preoperative irradiation and interstitial radiotherapy-hyperthermia boost in breast tumors > or = 3 cm. The Düsseldorf experience].

AIM: The aim of this protocol was to investigate breast conservation rates with and without flap-supported surgery after preoperative chemotherapy, radiotherapy and hyperthermia. PATIENTS AND METHODS: One hundred and fifty-eight patients with stage IIA-IV breast cancers were initially treated with chemotherapy, radiotherapy and hyperthermia. Radiation treatment consisted of an interstitial boost of 10 Gy 192Ir-afterloading therapy and a course of external beam radiotherapy of 50 Gy, using 5 x 2 Gy/week. Local hyperthermia with 43.5-44.5 degrees C over 60 minutes was delivered immediately before interstitial radiotherapy. RESULTS: One hundred and forty-two patients underwent salvage surgery. A breast-conserving approach was possible in 74 patients (52%). Fifty-three patients (37%) underwent flap-supported surgery. After a median follow-up of 20 months, one patient developed isolated local recurrence. In 14 cases, locoregional recurrences occurred in combination with distant metastases. CONCLUSION: In about 50%, breast conservation was achieved by chemotherapy, radiotherapy and hyperthermia. The low isolated local recurrence rate of 0.6% (1/158) has to be substantiated by further follow-up.

Adult↗
PubMed1997

CT-based software for 3-D localization and reconstruction in stepping source brachytherapy.

This paper describes innovative software for catheter localization and three-dimensional (3-D) reconstruction in stepping source brachytherapy applications. Patient information is a set of computed tomography (CT) slices scanned during the implantation of brachytherapy catheters. Catheter geometry and patient anatomy are exported for use with dose calculation software modules. The errors produced by the system are also encouragingly low. Time saving was achieved, in terms of other traditional reconstruction techniques. Various automated procedures, 3-D graphics and a user-friendly GUI, have contributed to providing a powerful, comprehensive software tool, directly useable in the clinical practice.

Brachytherapy↗
PubMed1997

Simultaneous paclitaxel and radiotherapy: initial clinical experience in lung cancer and other malignancies.

This report summarizes results from a series of pilot trials using combined-modality chemoradiotherapy with paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) as a radiosensitizing agent in patients with cancers of the lung, cervix, and bladder. In a phase I study of paclitaxel/radiotherapy in patients with locally advanced non-small cell lung cancer, five paclitaxel dose levels were evaluated in conjunction with simultaneous radiation (total dose, 59.4 Gy). A minimum of five patients were treated at each dose level; paclitaxel doses ranged from 45 mg/m2 over 3 weeks (level 1) to 65 mg/m2 for 7 weeks. Of 34 enrolled patients, 25 are evaluable for toxicity and response. Side effects were generally moderate for this combined-modality therapy, although two patients at level 5 developed dose-limiting toxicities (grade 4 esophagitis and grade 3 pneumonitis). Among 25 evaluable patients, complete and partial response rates were 4% (one patient) and 64% (16 patients), respectively; eight patients had a minor response. Median survival was 6 months (range, 1 to 20 months). Therapy was well tolerated, suggesting that the combined modalities offer a practical, effective therapy for patients with non-small cell disease. A paclitaxel dose of 55 mg/m2 is recommended for further study of combined-modality chemoradiotherapy in this clinical setting. In another trial, 33 women with inoperable, locally advanced cervical cancer received carboplatin 50 mg/m2 via intravenous infusion simultaneously with external-beam radiation therapy and vaginal brachytherapy, to define the regimen's toxicity and safety. Among the 33 women, 78% achieved a complete response to therapy. The investigators next conducted a trial of paclitaxel 50 mg/m2 given weekly over 3 hours with the previous carboplatin/radiotherapy regimen in four women and documented two partial responses, one near-complete response, and one minor response, with moderate, manageable toxicity. In a final case report on a patient with recurrent bladder cancer, simultaneous radiotherapy and weekly paclitaxel 50 mg/m2 intravenously over 3 hours yielded a partial remission, prompting the investigators to plan a phase I study to confirm the regimen's efficacy and safety. Additional planned studies include a phase I trial of simultaneous chemoradiotherapy in patients with cancer of the head and neck.

Adult↗
PubMed1996

Effect of recombinant human granulocyte colony stimulating factor (R-metHuG-CSF) as an adjunct to large-field radiotherapy: a phase I study.

PURPOSE: To test the feasibility of recombinant human granulocyte colony stimulating factor application during large-field radiotherapy. METHODS AND MATERIALS: Fifteen patients with clinically and histologically proven malignancy who received large-field radiotherapy entered this study. Administration of recombinant granulocyte colony stimulating factor (G-CSF) at a dose of 300 microgram subcutaneously was started on Friday and was continued on Saturday and Sunday after the first radiotherapy treatment, which began on the Monday before. In this way four courses of G-CSF were applied every Friday, Saturday, and Sunday during the radiotherapy period. Absolute neutrophil cell (ANC) and blood counts were monitored twice a week and compared to a second group of 15 patients who received large-field radiotherapy without G-CSF. Before and at the end of every cycle of G-CSF, ANC, blood counts, and biochemistry were measured. We compared the myelotoxicity of the patients treated with G-CSF with 15 patients without G-CSF treated at the same period with large-field radiotherapy, in match pair technique. RESULTS: G-CSF increased the ANC throughout the period of irradiation, and the treatment time needed for competing radiotherapy was shorter in the group who received G-CSF. Fourteen of 15 patients who received G-CSF treatment completed large-field radiotherapy without pause. Only 1 of 15 patients not receiving G-CSF was able to receive radiation treatment on schedule. Patients receiving G-CSF completed treatment with the mantle-field technique in 24 days and those with the abdominal bath technique in 26.5 days. Conversely, patients treated without G-CSF completed treatment with the mantle-field technique in 30.5 days and those with the abdominal bath technique in 36 days. The most frequent side effect was musculoskeletal pain. CONCLUSION: The prophylactic application of G-CSF during large-field radiotherapy before the onset of neutropenia was feasible in this schedule. Whether or not this shortening of treatment duration will translate into an improvement in efficacy is not clear.

Adult↗
PubMed1996

Simultaneous radiochemotherapy with paclitaxel in non-small cell lung cancer: a clinical phase I study.

Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) is one of the most active single agents available for the treatment of non-small cell lung cancer (NSCLC), with reported response rates of 21% to 24%. Its observed radiosensitizing effect is attributed to its interruption of cell development at the G2/M phase of the cell cycle, when cells are most sensitive to the killing effects of ionizing radiation. This phase I study of paclitaxel and simultaneous radiation therapy in patients with previously untreated, locally advanced inoperable stage IIIA/B NSCLC was designed to determine the maximum tolerated paclitaxel dose, to define the safety and toxicity of this combined modality, and to obtain preliminary data on its activity. Patients received a fixed dose of radiotherapy (1.8 Gy/d, 5 days a week, in shrinking-field technique, for a total dose of 59.4 Gy) and concomitant chemotherapy with a 3-hour infusion of paclitaxel once weekly on day 1, initially at a dose of 45 mg/m2, for 3 weeks. This dose remained constant during study levels 1 to 3, with the number of weeks of treatment increasing to 5 and 7 at levels 2 and 3, respectively. At dose level 4, the paclitaxel dose was increased to 55 mg/m2 over 7 weeks. Of 22 NSCLC patients who entered the study, 18 are evaluable for toxicity and response. Responses included one complete and 10 partial remissions; the other seven patients had minimal improvement. The therapy was well tolerated; no severe adverse events were associated with paclitaxel or radiotherapy. This combined modality appears to be a practicable and effective treatment for NSCLC. The maximum tolerated paclitaxel dose has not yet been reached, and dose escalation is planned.

Adult↗