In vivo dosimetry with semiconducting diodes for dose verification in total-body irradiation. A 10-year experience.

BACKGROUND AND PURPOSE: For total-body irradiation (TBI) using the translation method, dose distribution cannot be computed with computer-assisted three-dimensional planning systems. Therefore, dose distribution has to be primarily estimated based on CT scans (beam-zone method) which is followed by in vivo measurements to ascertain a homogeneous dose delivery. The aim of this study was to clinically establish semiconductor probes as a simple and fast method to obtain an online verification of the dose at relevant points. PATIENTS AND METHODS: In 110 consecutively irradiated TBI patients (12.6 Gy, 2 x 1.8 Gy/day), six semiconductor probes were attached to the body surface at dose-relevant points (eye/head, neck, lung, navel). The mid-body point of the abdomen was defined as dose reference point. The speed of translation was optimized to definitively reach the prescribed dose in this point. Based on the entrance and exit doses, the mid-body doses at the other points were computed. The dose homogeneity in the entire target volume was determined comparing all measured data with the dose at the reference point. RESULTS: After calibration of the semiconductor probes under treatment conditions the dose in selected points and the dose homogeneity in the target volume could be quantitatively specified. In the TBI patients, conformity of calculated and measured doses in the given points was achieved with small deviations of adequate accuracy. The data of 80% of the patients are within an uncertainty of +/- 5%. CONCLUSION: During TBI using the translation method, dose distribution and dose homogeneity can be easily controlled in selected points by means of semiconductor probes. Semiconductor probes are recommended for further use in the physical evaluation of TBI.

Selenium levels during the course of radiotherapy. No influence of irradiation on blood selenium concentration.

PURPOSE: To evaluate the influence of tumor characteristics and irradiation on blood selenium concentrations and their course during radiotherapy. MATERIAL AND METHODS: Selenium Levels were determined at various times during radiotherapy (I: beginning, II: mid, III: end, IV: 6 weeks after) by atomic absorption spectrometry in whole blood. The values were correlated with patient-, tumor- and irradiation-related parameters. RESULTS: A total of 690 samples were analyzed in 224 patients. The mean selenium value was 75.64 microg/l at the beginning of radiotherapy. 170 patients (77%) had reduced selenium Levels < 89 microg/l. Twelve patients (5.4%), mostly with head-and-neck cancer, had critically low values which need to be controlled and monitored. Three patients (1.3%) with breast cancer had critically increased values. Female patients showed higher seLenium concentrations than male patients (p = 0.0404). Patients diagnosed for head-and-neck cancer had significantly lower seLenium values than breast cancer patients (p = 0.016). Previous treatment by surgery and/or chemotherapy was correlated with lower selenium concentrations compared with irradiation as primary treatment (p = 0.039). According to analysis of variance, there was no significant change of the selenium concentration during the course of radiotherapy (p > 0.05). CONCLUSION: A preexisting selenium deficiency could be diagnosed in the broad majority of cancer patients undergoing radiotherapy. In contrast to the widely held opinion, it was not further aggravated by standard radiotherapy protocols.

Results of postoperative (90)Sr radiotherapy of keloids in view of patients' subjective assessment.

BACKGROUND AND PURPOSE: As treatment of keloids is mainly a cosmetic indication, the authors investigated, beyond the recurrence rate, the patients' satisfaction with the result and its correlation with objective medical findings. PATIENTS AND METHODS: 83 keloids of 66 patients had been irradiated after excision by a uniform protocol with 4 x 5 Gy (strontium- 90 [(90)Sr] surface applicator). A questionnaire was developed and sent out in which, above all, the satisfaction with the therapeutic and cosmetic outcome was obtained. These results were correlated with objective parameters and medical findings which were ascertained during an extra follow-up examination. RESULTS: Among 18 of the 41 patients (44%), who had answered the questionnaire, 19 of the 53 keloids treated (36%) had relapsed. 61% of the patients were extremely or mainly satisfied with the therapeutic outcome, 51% extremely or mainly satisfied with the cosmetic outcome. The relief from former keloid-caused symptoms (therapeutic outcome: p = 0.0005; cosmetic outcome: p = 0.0011), the ear as keloid localization (p = 0.0008 and p = 0.0197), and male gender (therapeutic outcome: p = 0.0423) were significantly associated with higher satisfaction. The recurrence rate as well as the extent of radiation side effects had no significant influence on patients' assessment. CONCLUSION: Cosmetic aspects like the dermal side effects and the patients' satisfaction should be taken into account when evaluating the results of radiotherapy in keloids.

Investigations of dose response of BANG polymer-gels to carbon ion irradiation.

In this presentation BANG polymer-gel dosimetry using magnetic resonance imaging (MRI) is applied to densely ionizing radiation such as carbon ion beams. BANG polymer-gels were irradiated with monoenergetic 12C ions at an energy of 205 MeVu(-1). The irradiation of the gels with doses up to 100 Gy were performed at the radiotherapy facility of the GSI, Darmstadt, Germany. For comparison with sparsely ionizing radiation data were obtained for 6 MV photon radiation, too. It was the object to examine the saturation effect for densely ionizing radiation that occurs at high values of linear energy transfer (LET). Up to now the dose response is unknown for mixed radiation fields of primary carbon ions. Therefore, to facilitate such conversions of measured MR signals into dose model calculations are proposed. This model relies only on heavy ion track structure and the experimentally determined photon response.

Tartrate-resistant acid phosphatase 5b as serum marker of bone metabolism in cancer patients.

BACKGROUND: The serum marker tartrate-resistant acid phosphatase isoform 5b (TRACP 5b) is considered a specific parameter of osteoclast activity and a useful marker of bone resorption. Regarding the utility of TRACP 5b in bone metastases, this review aims to draw clinically relevant conclusions. MATERIALS AND METHODS: The available literature data regarding the laboratory methods, the characteristics of TRACP 5b and the clinical data, as well as our own results about TRACP 5b in cancer patients has been reviewed. RESULTS: In contrast to enzymatic assays, two new assays based on a monoclonal antibody and on heparin-induced inhibition of TRACP 5a, respectively, demonstrated low biological and analytical variabilities in healthy subjects as well as in patients with osteoporosis. Up to now, only a few studies have evaluated the utility of TRACP 5b in cancer patients with bone metastases. In these studies, the sensitivity of TRACP 5b was higher compared to other markers. Furthermore, TRACP 5b activity correlates with the response to the treatment of bone metastases. CONCLUSION: Although the clinical data available are promising, the results are still preliminary. In addition to further evaluation of the analytical method, more studies in cancer patients are needed to establish TRACP 5b in the diagnostic procedure and in the therapy monitoring of bone metastases.