Multi-centre calibration of an adaptive thresholding method for PET-based delineation of tumour volumes in radiotherapy planning of lung cancer.

PURPOSE: To evaluate the calibration of an adaptive thresholding algorithm (contrast-oriented algorithm) for FDG PET-based delineation of tumour volumes in eleven centres with respect to scanner types and image data processing by phantom measurements. METHODS: A cylindrical phantom with spheres of different diameters was filled with FDG realizing different signal-to-background ratios and scanned using 5 Siemens Biograph PET/CT scanners, 5 Philips Gemini PET/CT scanners, and one Siemens ECAT-ART PET scanner. All scans were analysed by the contrast-oriented algorithm implemented in two different software packages. For each site, the threshold SUVs of all spheres best matching the known sphere volumes were determined. Calibration parameters a and b were calculated for each combination of scanner and image-analysis software package. In addition, "scanner-type-specific" calibration curves were determined from all values obtained for each combination of scanner type and software package. Both kinds of calibration curves were used for volume delineation of the spheres. RESULTS: Only minor differences in calibration parameters were observed for scanners of the same type (Δa ≤4%, Δb ≤14%) provided that identical imaging protocols were used whereas significant differences were found comparing calibration parameters of the ART scanner with those of scanners of different type (Δa ≤60%, Δb ≤54%). After calibration, for all scanners investigated the calculated SUV thresholds for auto-contouring did not differ significantly (all p>0.58). The resulting sphere volumes deviated by less than -7% to +8% from the true values. CONCLUSION: After multi-centre calibration the use of the contrast-oriented algorithm for FDG PET-based delineation of tumour volumes in the different centres using different scanner types and specific imaging protocols is feasible.

Determination of the dose characteristics in the near area of a new type of 192Ir-HDR afterloading source with a pinpoint ionization chamber.

Since the company MDS Nordion Haan GmbH introduced the new afterloading radiation unit GammaMed plus in 1998, new HDR Ir-192 sources with a diameter of 0.9 mm (formerly 1.1 mm) and a length of 4.5 mm (formerly 5.5 mm) have been used. With this equipment it is possible to treat peripheral vessels for prophylaxis of restenosis after percutaneous transluminal angioplasty (PTA). In this case a good knowledge of the dose characteristics in the near area is the prerequisite for safe application. In this study, the dose characteristics for this source type is investigated at close range by means of an ionization chamber. For the description of the dose characteristics, the radial dose distribution and the anisotropy function are used. The measurements were carried out using an ionization chamber, the so-called PinPoint chamber (Type PTW 31006, PTW Freiburg, Germany). The radial dose distribution was examined in the area of 0.26 to 12 cm. The anisotropy function was examined in the range from 0.5 to 5 cm (distance from the effective site of measurement to the source axis). The radial dose function was compared with the correction function k(as,w) (r), published in the German standard DIN 6809 part 2 (1991 Beuth Verlag, Berlin, Germany). In the area up to 4 cm (distance source-axis to measuring point) the deviation maximized up to 2%. The deviation climbs with greater distance from the source with results around 3%. The anisotropy function was compared with that used in the treatment planning system Abacus 3.0 of the same manufacturer. In the close range between 0.5 and 1 cm, there were some major variations (up to 10%) from the anisotropy function used in the planning system. The fault reduces itself with greater distance to under 2%. In view of the results presented in this paper further measurements of the anisotropy function in the close range from 0 to 1.5 cm from the source axis should be made. It can be seen that the function used in the planning system supplies results that are too high in comparison with the results of other authors. This concerns primarily the area of very small and very big angles.

An on-line phase measurement system for quality assurance of the BSD 2000. Part I: technical description of the measurement system.

The hyperthermia system BSD 2000 with the ring applicator Sigma 60 utilizes the principle of a phase controlled group radiation source. The accuracy of the phase relationship between the four receiving HF signals is crucial for the position of the electric field inside the applicator. Therefore, essential significance falls to the phase control of the system. An automatic phase measuring technique has been developed to register immediately the phase position of the four channels of the BSD 2000 with respect to a reference signal. The system improves the insurance of the technical safeguarding. In the first part of this work, the technical realization of the measurement system is described and first measurements with the system are given. In the second part, results with respect to the quality assurance of the BSD 2000 system are presented.

An on-line phase measurement system for quality assurance of the BSD 2000. Part II: results of the phase measurement system.

Phase constancy and accuracy are significant for regional hyperthermia with phased array radiofrequency hyperthermia systems. They are both necessary for a precise target steering in therapy. For the BSD 2000 system (BSD Medical Corp. Salt Lake City, Utah, USA), the phase values of all channels are checked with a self-developed automatic on-line phase measurement system. On different days the phases are measured under identical conditions, where the output paths are cut off with 50 ohm dummy loads to suppress the influence of the radiation conditions of the antennae on the measurement values. The results show how the phase values of the four channels change in the first 30 min and from day to day. During this time interval after the start the phases drop down by up to 15 degrees. For the time later changes are very slight and the differences from day to day are negligible. The phase shift that occurs in the first 30 min is as high as a change of the target point by 1 cm. Earlier switching on of the amplifiers prevents this shift occurring during the treatment. The measurement system provides a good tool for determination of phase accuracy and is easy to realize.

Cystosarcoma phyllodes malignum: a case report of a successive triple modality treatment.

This paper reports on a woman with a rapidly growing recurrent cystosarcoma phyllodes malignum after two major attempts of surgery. In this situation, neoadjuvant hyperfractionated radiotherapy, superficial hyperthermia and ifosfamide were administered. Toxicity was mild. Resection of the tumour bed revealed a pathologically complete response with an actual disease free follow-up of 48 months.

Appendicitis during locoregional thermoradiotherapy of advanced or recurrent rectal and cervical cancer, a report of two cases.

INTRODUCTION: Local tumour control after irradiation alone for advanced, inoperable carcinomas of the bladder and rectum or inoperable recurrent cervical carcinoma is usually disappointing. Both preclinical and clinical studies reported improvements by adding hyperthermia to radiotherapy. Reports for phase II/III trials do not indicate any enhanced side effects. However, two cases of acute suppurating appendicitis were observed in a series of patients treated with deep regional hyperthermia. MATERIALS, METHODS AND RESULTS: Eighty patients with advanced, inoperable, or recurrent rectal or recurrent cervical tumours were treated with deep regional hyperthermia (313 sessions) in addition to radiotherapy between September 1995 and October 1998. The treatment for two of these patients (2.5%) had to be discontinued after the fourth/second hyperthermia treatments at 19.8/10.8 Gy total dose, respectively, for symptoms of pain in the right pelvis and elevated rectal temperature. Both patients underwent laparotomy and were found to have suppurative appendicitis. In addition to the retrocoecal location in both patients, evidence of preexisting chronic appendicitis, and appendiceal faecalith were observed in each patient. CONCLUSION: The development of acute appendicitis in 2.5% of patients during a course of deep regional thermoradiotherapy for pelvic tumour is much higher than the expected incidence of appendicitis in the general population (< 1/1000) (Korner et al. 1997). An enhanced risk of suppurative appendicitis in patients undergoing pelvic thermoradiotherapy cannot be excluded, especially in retrocoecal located appendices with obstructed appendix lumen from preexisting chronic appendicitis or faecalith.

Evaluation of predictive factors for local tumour control after electron-beam-rotation irradiation of the chest wall in locally advanced breast cancer.

BACKGROUND AND PURPOSE: Different radiotherapy techniques are being used for chest wall irradiation after mastectomy. We review our results with the electron-beam-rotation technique in a series of 130 high risk breast cancer patients. The main end point of the study was local tumour control; secondary end points were disease free survival, and overall survival, as well as acute and late side effects. MATERIAL AND METHODS: From January 1990 to June 1995, 89 patients underwent electron-beam-rotation irradiation of the chest wall after primary mastectomy and axillary lymph node dissection (group I) and 41 patients after excision of local recurrent breast cancer (group II) with 4 x 2.5 Gy/week to 50 Gy total dose (4-12 MeV electrons depending on the thickness of the chest wall). In addition, irradiation of local-regional lymph nodes and/or a local boost of 10 Gy were applied dependent on the resection and node status. RESULTS: After a median follow up of 29 months (65% stadium III/IV) the 3 year local tumour control, disease free survival, and overall survival were 73%, 47%, and 75%, respectively. Local control in group I was 78% versus 60% in group II. Significant predictors for local tumour control, disease free survival, and overall survival were resection status (R0 versus R1/2) and estrogen receptor status (positive versus negative). In group I, tumour grading (GI-IIa versus GIIb-III) and estrogen receptor status were found to be additional significant prognostic factors for complete resected tumours. Five patients developed symptomatic pneumonitis (< 4%) and one patient developed a chronic fistula at the resection. A significant correlation between the degree of acute skin reaction and persistent pigmentation was observed. CONCLUSION: In high risk breast cancer patients postoperative irradiation with the electron-beam-rotation technique of the chest wall is an effective therapy resulting in 78% local tumour control at 3 years for locally advanced breast cancer and 60% for recurrent disease. The rate of acute and late toxicity is low. The degree of acute skin reaction correlates with the degree of persistent pigmentation.

ESHO quality assurance guidelines for regional hyperthermia.

The Technical Committee and the Clinical Committee of the ESHO evaluated the experience of the institutes which are active in clinical regional hyperthermia using radiative equipment. Based on this evaluation, QA guidelines have been formulated. The focus of these guidelines lies on what must be done not on how it should be done. Subjects covered are: treatment planning, treatment, treatment documentation, requirements and characterization of equipment, safety aspects, hyperthermia staff requirements and instrumentation for quality assurance.