Biomedical subjects

Thomas Herrmann

Publications and source records attributed to Thomas Herrmann.

39 records · Page 3Linked to original sources

PubMed2002

Second primary tumors after radiotherapy for malignancies. Treatment-related parameters.

PURPOSE: The aim of the present analysis was to identify radiotherapy-related parameters that influence the development of second malignancies. PATIENTS AND METHODS: Between 1969 and 1989, about 31,000 patients were treated in Dresden with low voltage (< or = 180 kV X-rays) or telecobalt radiotherapy or a combination of both. Of these 203 were readmitted after earlier radiotherapy, for radiotherapy of a newly developed malignancy. Based on definitive diagnosis of a secondary tumor and completeness of documentation 53 patients were selected for further analysis. This included the spatial relation between the new tumor and the primary treatment fields, and the incidence in relation to the dose at the site of origin. The material does not allow for risk estimation. RESULTS: Primary malignancies comprised breast and gynecological tumors in female, and tumors of prostate, head and neck and lymphomas in male patients. Second tumors developed mainly in corpus uteri, respiratory, gastrointestinal and urinary tract. The high incidence of 9.9% second primary corpus/cervix uteri tumors in patients with primary breast cancers suggests a common etiology. The majority of second tumors was observed within the margin of the planning target volume (PTV), which was defined as the volume 2.5 cm inside to 5 cm outside the field margin proper. Inside the PTV developed < 10%, outside 11% of the second tumors. With regard to dose the majority of second tumors was observed in the region receiving < 6 Gy. CONCLUSIONS: A significant number of second primary tumors is found in the volume receiving < or = 6 Gy, i.e. at the margins of the PTV. This should be considered for multiple field radiotherapy and IMRT, where the relevant volumes may be substantially increased.

Adolescent↗

PubMed2002

Evaluation of a device for attenuation of electron release from dental restorations in a therapeutic radiation field.

STATEMENT OF PROBLEM: For some patients, radiation treatment is a part of tumor therapy in the head and neck area before and/or after surgery. The oral cavity and teeth are thereby frequently exposed to high doses of radiation. In this situation, electronic backscatter from dental materials may damage the surrounding soft tissue. PURPOSE: This study determined the degree of absorption and the backscatter effect of therapeutic radiation used in the presence of 4 different dental materials. The efficacy of a protective stent also was investigated. MATERIAL AND METHODS: The influence of 4 dental materials (a high-gold alloy, pure titanium, amalgam, and a synthetic material) on radiation dose distribution was tested on 2 test models that simulated the presence of teeth. An alanine dosimeter was used to make measurements with and without the presence of a protective stent. To verify the results, one of the test models was compared to a computer simulation. RESULTS: Backscatter effects on the surface of dental materials caused an increase of up to 170% of the radiation dose measured without the materials. The rate of overdose increased with the atomic number of the dental material. The extent of the backscatter effect was a maximum of 4 mm. CONCLUSION: The considerable overdose of 170% found in this study suggests that soft tissue surrounding dental restorations should be protected from radiation. The backscatter results indicate that soft tissue could be effectively shielded with a 3-mm synthetic stent.

Absorption↗

PubMed2002

Cancer induction by radiotherapy: dose dependence and spatial relationship to irradiated volume.

The present study was initiated to identify radiotherapy-related parameters influencing the development of second malignancies. Between 1969 and 1989, about 31000 patients were treated with radiotherapy in Dresden. Of these, 203 were re-admitted for radiotherapy of a newly developed malignancy. Based on completeness of documentation, definition of site of origin and exclusion of recurrent or metastatic tumours, 85 patients were selected for analysis of spatial relation between new tumour and primary treatment fields, and of dose at the site of origin. The majority of second tumours were seen within the margin region of the treatment volume, defined as the volume from 2.5 cm inside to 5 cm outside the margin of the planning target volume (PTV). Fewer than 10% of the second tumours occurred inside the PTV and 11% developed outside the margin region. The majority of second tumours were observed in the volume receiving <6 Gy. Similar results were obtained in a group of 31 patients initially irradiated for benign diseases. This should be considered in radiotherapy, particularly with multiple-field techniques or intensity-modulated radiotherapy, where the volume receiving <6 Gy is substantially increased.

Humans↗