Long-term outcome after neoadjuvant radiochemotherapy in locally advanced noninflammatory breast cancer and predictive factors for a pathologic complete remission : results of a multivariate analysis.

BACKGROUND: An earlier published series of neoadjuvant radiochemotherapy (NRT-CHX) in locally advanced noninflammatory breast cancer (LABC) has now been updated with a follow-up of more than 15 years. Long-term outcome data and predictive factors for pathologic complete response (pCR) were analyzed. PATIENTS AND METHODS: During 1991-1998, 315 LABC patients (cT1-cT4/cN0-N1) were treated with NRT-CHX. Preoperative radiotherapy (RT) consisted of external beam radiation therapy (EBRT) of 50 Gy (5 × 2 Gy/week) to the breast and the supra-/infraclavicular lymph nodes combined with an electron boost in 214 cases afterwards or-in case of breast conservation-a 10-Gy interstitial boost with (192)Ir afterloading before EBRT. Chemotherapy was administered prior to RT in 192 patients, and concomitantly in 113; 10 patients received no chemotherapy. The update of all follow-up ended in November 2011. Age, tumor grade, nodal status, hormone receptor status, simultaneous vs. sequential CHX, and the time interval between end of RT and surgery were examined in multivariate terms with pCR and overall survival as end point. RESULTS: The total pCR rate after neoadjuvant RT-CHX reached 29.2%, with LABC breast conservation becoming possible in 50.8% of cases. In initially node-positive cases (cN+), a complete nodal response (pN0) after NRT-CHX was observed in 56% (89/159). The multivariate analysis revealed that a longer time interval to surgery increased the probability for a pCR (HR 1.17 [95% CI 1.05-1.31], p < 0.01). However, in large tumors (T3-T4) a significantly reduced pCR rate (HR 0.89 [95% CI 0.80-0.99], p = 0.03) was obtained. Importantly, pCR was the strongest prognostic factor for long-term survival (HR 0.28 [95% CI 0.19-0.56], p < 0.001). CONCLUSION: pCR identifies patients with a significantly better prognosis for long-term survival. However, a long time interval to surgery (> 2 months) increases the probability of pCR after NRT-CHX.

Chest wall and intrathoracic desmoid tumors: surgical experience and review of the literature.

Desmoid tumors are fibroblastic/myofibroblastic neoplasms, which originate from musculo-aponeurotic structures and are classified as deep fibromatoses. Despite their benign histologic appearance and lack of metastatic potential, desmoid tumors may cause aggres?sive local infiltrations and compression of surrounding structures. They are often associated with female gender, familial adenomatous polyposis (FAP) and sporadically may occur at sites of previous trauma, scars or irradiation. Molecular studies have demonstrated that these patients are associated with a bi-allelic APC mutation in the affected tissue. Radical tumor resection with free margins remains the first therapy of choice. In cases with anatomical or technical limitations for a wide excision, radiation therapy represents a proven and effective alternative or supplementary treatment.

Validity of S-100 B in patients after brain radiation.

BACKGROUND: S-100B is a calcium binding acute phase protein and a potential biomarker for brain injury. In prior studies elevated plasma S-100B levels were detected in stroke and severe head trauma. The aim of this study was to evaluate whether S-100 B is elevated during cerebral radiotherapy and whether that is associated with adverse outcomes. MATERIAL AND METHODS: In this prospective pilot study, 45 patients (25 males, 20 females, median age 58 (17-81)) underwent cerebral radiation therapy because of a primary or metastaic cerebral malignancy. 39 patients were included in the evaluation. 6 patients died during the study period. S-100 plasma concentrations were measured with an electrochemiluminescence immunoassay on admission and weekly during radiation therapy for the duration of 6 weeks. In 10 healthy young volunteers (5 males, 5 females, median age 32 (28-36)) S-100 B plasma levels were measured weekly for 6 weeks as a negative control. Furthermore, in an active control 10 patients (4 males, 6 females, median age 68 (64-76)) with stroke (7 = major stroke, 3 = lacunar infarct) S- 100 B plasma levels were measured for 7 consecutive days after the event. RESULTS: During radiotherapy S-100 B plasma concentrations increased from median baseline values of 0.030 microg/l to 0.044 microg/l. For the time of radiation therapy most patients showed a mild increase, but absolute plasma values were still within the normal range. In the control group of healthy volunteers S-100 B remained unchanged. In stroke patients S-100 B increased to maximum values of 1.7 microg/l three days after the event. In the 3 patients with lacunar infarcts no increase of S-100 B levels could be detected. CONCLUSION: Brain irradiation leads to a mild increase of S-100 B plasma levels. However, the absolute rise was far weaker compared to that seen in major brain injuries.

Modern therapy of rectal carcinoma.

Throughout the past decade the treatment of rectal carcinoma has improved remarkably. Today, individualized multimodality treatment allows local and distant tumor freedom with preservation of anorectal and genitourinary function in a majority of patients. Radiotherapy is elementary in reducing the risk of local recurrence whereas chemotherapy including promising novel agents prevents or eliminates distant metastases. However, surgery revolutionized by TME (total mesorectal excision) remains the only curative treatment for rectal carcinoma. In this study the authors review the developments as well as the current status of modern treatment for rectal carcinoma.

Unilateral keloid formation after bilateral breast surgery and unilateral radiation.

BACKGROUND: Keloid is a hypertrophic scar that may arise within 6 months after injury in susceptible individuals. Different therapies like surgical excision, intralesional steroid injections, local application of pressure, or postoperative irradiation with x-rays or electrons are reported. Although an immediate starting of therapy after surgery is usually recommended, delayed radiotherapy may also be effective. CASE REPORT: We report on a 48 year old women with a history of an invasive ductal carcinoma in the upper lateral quadrant of the left breast. A breast conserving tumor resection with axillary dissection was performed. An adapting reduction mammaplasty was carried out on the right breast for cosmetic reasons at the same time. 5 weeks after surgery, adjuvant radiotherapy was applied with a total dose of 59 Gy to the left breast. 10 weeks after surgery and by the end of radiotherapy, a keloid had developed on the right breast with reduction mammaplasty, but not on the left irradiated one. 8 months after initial surgery the patient's keloid formation on the right mamma was removed by surgical resection and a keloid prevention with postoperative radiotherapy with 20 Gy was performed. CONCLUSION: Postoperative radiation of the scar prevented effectively keloid formation while simultaneously a hypertrophic scar developed in the non-irradiated scar.

Multifocal epithelioid hemangioendothelioma: case report of a clinical chamaeleon.

Epithelioid hemangioendothelioma is an extremely rare vascular bone tumor with a slow growth and poor prognosis. The term was designed to describe neoplasms that had an appearance in between hemangiomas and sarcomas. Various synonyms for epithelioid hemangioendothelioma are used clinically: low grade anaplastic angiosarcoma, cellular hemangioma, histiocytoid hemangioma and angioendothelioma. However, it represents 1% of all vascular neoplasms and is locally aggressive. We report the course of disease of a 47-year-old man who presented to our clinic with unspecific abdominal and back pain. Radiological findings revealed multiple lesions in the spine as well as liver and spleen involvement. Tumor histology of the bone and liver biopsies confirmed the diagnosis of epithelioid hemangioendothelioma. Although treatment was initiated with thalidomide, the patient developed multiple organ dysfunction syndrome (MODS) and succumbed to his disease. This case report may contribute to the data on clinical findings and natural history of this rare tumor.

Remission rates following preoperative chemotherapy and radiation therapy in patients with breast cancer.

PURPOSE: To evaluate remission and breast-conservation rates after preoperative chemotherapy or chemo-radiotherapy (CT-RT). PATIENTS AND METHODS: Seventy-three patients with 74 biopsy-proven invasive breast cancers prospectively entered the protocol. Eighteen patients were treated by neoadjuvant chemotherapy followed by surgery and adjuvant irradiation (chemotherapy group). Fifty-five patients with 56 tumors were treated with combined neoadjuvant chemo-radiotherapy, followed by surgery (chemo-radiotherapy group). Most patients of both treatment groups received 4 cycles of EC chemotherapy. In some patients with large tumors 3 cycles of CMF were added. Chemotherapy was followed by hormonal treatment with tamoxifen or LHRH agonists in case of positive hormone-receptor status. Preoperative radiotherapy was administered using 2 Gy fractions up to a total dose of 50 Gy, followed by a tumor boost of 6 to 11 Gy. The median overall treatment time was 41 days (range: 35 to 55 days). The median time interval between end of neoadjuvant therapy and surgery was 11 weeks (range: 10 to 22 weeks) and 27 weeks (range: 11 to 41 weeks) for the chemotherapy- and chemo-radiotherapy group. The median time interval between end of chemotherapy and the beginning of irradiation ranged between 2 and 8 weeks (median 4 weeks) in the chemo-radiotherapy group. RESULTS: Side-effects due to chemo- or radiotherapy were moderate and reversible. In the chemotherapy group 17/18 patients (94%) achieved a partial (pPR) and 1/18 patients (6%) a complete histopathological response (pCR). In the chemo-radiotherapy group 32/56 (57%) showed a pPR and 24/56 (43%) a pCR. The difference in complete remission is significant (Fisher's Exact Test: p = 0.004). In 45/74 cases (61%) the breast was preserved, immediate breast reconstructions with rectus myocutaneous flaps (TRAM) after mastectomy were performed in 8/74 cases (11%) and modified radical mastectomies without reconstruction were required in 21/74 cases (28%). The breast conservation rates were similar in both treatment groups. CONCLUSIONS: Even though the small number of patients in the present protocol does not permit definite conclusions, the results of combined modality treatment seem promising with regard to tumor remission within the treated breast and as a tool for breast conservation in advanced stage disease. On the basis of these encouraging data a prospective Phase-III study has been initiated.

Prostate-specific antigen: effect of pelvic irradiation.

PURPOSE: To study the effect of pelvic irradiation on the level of serum prostate-specific antigen (PSA). MATERIALS AND METHODS: Of 33 patients treated with pelvic irradiation to the prostate and seminal vesicles for anal and rectal cancer, 26 received 50.4 Gy or more (1. 8 Gy per fraction), and seven received 25.0 Gy (5.0 Gy per fraction). PSA levels were measured before (n = 33), during (n = 26), and after radiation therapy (n = 33). In 24 patients, follow-up (mean, 15.7 months) PSA data were obtained. Actual and pretreatment PSA levels were compared (Wilcoxon rank test). RESULTS: During the first 3 weeks in all patients, PSA levels rose steeply, culminating in a 3. 7-fold increase (P =.02). At the end of radiation therapy (7 weeks), the PSA level was no longer significantly different from the pretreatment value. In the long term, the PSA level decreased to 77% of the pretreatment value (P =.04). CONCLUSION: Irradiation of the prostate initially elevates serum PSA levels. Apparently PSA release is determined by the duration of radiation therapy, while the accumulated dose has a minor effect. In the long term, PSA production is impaired after radical radiation therapy. PSA reference concentrations should be adjusted to these reduced levels.

Prognostic significance of DNA cytometry in thymoma.

PURPOSE: The aim of this work was to evaluate the prognostic significance of DNA image cytometry in thymoma. PATIENTS AND METHODS: Image cytometric studies with an automatic video-based analysis system (LEYTAS) were carried out on 47 archival specimens from 36 patients with thymomas who underwent operation at a single institution from 1954 to 1992. The significance of aneuploidy DNA-content (5c-exceeding events), and nuclear size on stage and survival were evaluated. The median follow-up was 52.7 (6-164) months. RESULTS: Masaoka's stage was predictive of aneuploidy (P < 0.01) and disease-free survival (P < 0.015). In stage I 18% of the tumors were aneuploid, in stage II 78%, in stage III 85% and in stage IV 100%. The occurrence of 5c-exceeding events was associated with both decreased disease-free survival (P < 0.01) and overall survival (P = 0.013). Nuclear size was not significantly correlated to stage. Under multivariate analysis, aneuploidy and DNA content failed to attain independent significance for stage, performance status, and histology. CONCLUSION: DNA image cytometry may provide additional information about the prognosis of resected thymoma.

[Conventional and virtual simulation in retrobulbar irradiation]. / Konventionelle und virtuelle Simulation bei der Retrobulbärbestrahlung.

BACKGROUND: Radiotherapy is commonly used in Grave's ophthalmopathy. The target volume encompasses the ocular muscles and the orbital tissue. The result of conventional simulation can be examined by means of CT simulation. PATIENTS AND METHODS: Twenty-five planning CTs with Grave's ophthalmopathy were studied. The conventional simulation of 4 x 4 cm2 lateral portals confined anteriorly by the fleshy canthus was performed on a CT-simulator using the observer's eye view (OEV) and digitally reconstructed radiographs (DRR). The coverage of the target volume and sparing of the eye lenses were studied on axial CT slices and multiplanar reconstructions (MPR). The distances between the apex of the orbita and cornea, fleshy canthus, and bony canthus were measured as well as the distance between cornea and posterior face of the lens. RESULTS: The pituitary gland and the ocular lenses were spared in each case (25/25). The orbita was entirely covered in 24 cases (96%). However, anterior parts of the external eye muscles were not completely encompassed in 7 cases (28%). The distance from the apex of the orbita to the cornea was 54.6 mm (53.3 to 55.8 mm, 95% confidence interval), to the fleshy canthus 40.3 mm (39.4 to 41.2 mm), and to the bony canthus 31.4 mm (30.2 to 32.5 mm). The distance between cornea and posterior face of the lens was 8.3 mm (7.9 to 8.7 mm). The distance between cornea and canthus differed significantly from normal eyes while the distance between cornea and posterior face of the lens was very similar to normal eyes. CONCLUSIONS: Conventional simulation of orbital irradiation with lateral fields confined anteriorly by the fleshy canthus ensures protection of the ocular lenses and the pituitary gland. However, anterior parts of the eye muscles may occasionally not completely be covered. The fleshy canthus and the cornea are more reliable landmarks as compared to the bony canthus.

The role of CT simulation in whole-brain irradiation.

PURPOSE: Evidence is growing that incorrect field-shaping is a major cause of treatment failure in whole-brain irradiation (WBI). To evaluate the potential benefits of CT simulation in WBI we compared field-shaping based on 3D CT simulation to conventional 2D simulation. METHODS: CT head scans were obtained from 20 patients. Conventional 2D planning was imitated by drawing the block contours on digitally reconstructed radiographs (DRR) by four radiotherapists. Critical parts of the target and the eye lenses were subsequently marked and planning was repeated using 3D information ("3D planning"). The results of both methods were compared by evaluation of the minimal distance from the field edge according to each site. RESULTS: In conventional planning using DRR, major geographic mismatches (< -3 mm) occurred in the subfrontal region and both eye lenses with 1% each location. Minor mismatches (-3 to 0 mm) predominantly occurred in the contralateral lens (21%), ipsilateral lens (10%), and subfrontal region (9%). Close margins (0-5 mm) were most frequently noted at the contralateral lens (49%), ipsilateral lens (35 %), and the subfrontal region (28%). When 3D planning was used, mismatches were not found. However, close margins were inevitable at the ipsilateral lens (5%), subfrontal region (30%), and contralateral lens (70%). CONCLUSIONS: CT simulation in WBI is significantly superior to conventional simulation with respect to complete coverage of the target volume and protection of the eye lenses. The narrow passage between the ocular lenses and lamina cribrosa represents a serious limitation. These patients are safely identified with CT simulation and can be referred for modified irradiation techniques.

Radiotherapy and high-dose chemotherapy in advanced Ewing's tumors.

BACKGROUND: Ewing's tumors are sensitive to radio- and chemotherapy. Patients with multifocal disease suffer a poor prognosis. Patients presenting primary bone marrow involvement or bone metastases at diagnosis herald a 3-year disease-free survival below 15%. The European Intergroup Cooperative Ewing's Sarcoma Study (EICESS) has established the following indications for high-dose therapy in advanced Ewing's tumors: Patients with primary multifocal bone disease, patients with early (< 2 years after diagnosis) or multifocal relapse. PATIENTS AND METHOD: As of 1987, 83 patients have been treated in the EICESS group, 39 of them at the transplant center in Düsseldorf, who have been analyzed here. All individuals received 4 courses of induction chemotherapy with EVAJA and stem cell collection after course 3 and 4. Consolidation radiotherapy of the involved bone compartments was administered in a hyperfractionated regimen 2 times 1.6 Gy per day, up to 22.4 Gy simultaneously to course 5 and 22.4 Gy to course 6 of chemotherapy. The myeloablative chemotherapy consisted of melphalan and etoposide (ME) in combination with 12 Gy TBI (Hyper-ME) or Double-ME with whole lung irradiation up to 18 Gy (without TBI). RESULTS: The survival probability at 40 months was 31% (44% DOD; 15% DOC). Pelvic infiltration did not reach prognostic relevance in this cohort. Radiotherapy encompassed 75% of the bone marrow at maximum (average 20%). Engraftment was not affected by radiotherapy. CONCLUSION: High-dose chemotherapy can improve outcome in poor prognostic advanced Ewing's tumors. The disease itself remains the main problem. The expected engraftment problems after intensive radiotherapy in large volumes of bone marrow can be overcome by stem cell reinfusion.

[Bone marrow recovery after irradiation of the spine]. / Knochenmarkregeneration nach Bestrahlung der Wirbelsäule.

BACKGROUND: Imaging of bone marrow by radio labeled antibodies against NCA-95 antigen of human granulocytes offers the possibility to visualize granulopoietic activity. After radiotherapy, a reduced uptake delineates the radiation field. Aim of our investigation was the study of strength and duration of this effect. PATIENTS AND METHODS: We analyzed 80 cases of patients irradiated for different primary or metastatic malignancies including parts of the spine who received a bone marrow scan for re-staging or during follow-up. Activity uptake of vertebrae inside and outside the irradiation portal was evaluated by ROI and the ratio was taken as measure of bone marrow suppression. RESULTS: A depression of granulopoietic bone marrow activity was seen even after a few fractions of 1.8 or 2 Gy (Figure 1). Depending on time since irradiation (Figure 2), we found a bone marrow recovery. In patients without bone metastasis, regeneration could be complete, whereas in patients treated for metastases, it was incomplete in all cases (Figure 3). CONCLUSIONS: For a certain time after irradiation, radioimmunoimaging delineates the irradiation portal by showing depression of granulopoiesis. Later on, it also shows bone marrow regeneration after radiotherapy. This may be helpful in reconstruction of radiation portals or in toxicity estimation during multimodal cancer therapy.

Thymoma: prognostic factors and treatment outcomes.

BACKGROUND: The objective of this study was to establish prognostic factors for thymoma and determine the impact of surgery with or without postoperative radiotherapy. METHODS: Seventy patients treated at the University Hospital Düsseldorf during the period 1954-1991 were retrospectively studied. All thymoma patients underwent surgery, 22 received postoperative radiotherapy, and 3 also received chemotherapy. According to thymoma staging as described previously by Masaoka et al., 21% were Stage I, 26% Stage II, 43% Stage III, 7% Stage IVA, and 3% Stage IVB. Lymphocytic type disease was found in 36% of patients, lymphoepithelial type in 33%, epithelial type in 23%, and spindle cell type in 9%. The relevance of Karnofsky performance status (KPS), gender, age, myasthenia gravis, histology, tumor size, and stage to survival was determined by univariate analysis, and their independent significance was tested by multivariate analysis. Survival rates were calculated using the Kaplan-Meier method and the log rank test. RESULTS: In univariate analysis, KPS (P < 0.001), histologic type (P=0.0093), and stage (P=0.0001) proved to be significant predictors of overall survival. Spindle cell type was associated with the best and epithelial type the worst prognosis; patients with the latter type had a 5-year survival rate of 30%. Multivariate analysis revealed that stage, histology, and KPS were predictive of overall survival. In Stages III and IV, relapses were reduced by postoperative radiotherapy from 50% to 20%. The site of relapse was outside the irradiated area in 80% of patients. Disease free survival (P=0.36) and median survival (P=0.72) of patients with completely resected advanced thymomas did not differ from that for patients with incompletely resected tumors who received radiotherapy. CONCLUSIONS: Postoperative radiotherapy can improve local control in patients with advanced thymoma. Survival after incomplete resection is not compromised when postoperative radiotherapy is employed. KPS should be considered an important prognostic factor in future studies.

Clinical in vivo dosimetry using optical fibers.

Discoloring of glass due to ionizing radiation depends on the absorbed dose. The radiation-induced light attenuation in optical fibers may be used as a measure of the dose. In high-energy photon beams (6 MV X rays), a lead-doped silica fiber can be calibrated. A dosimeter based on an optical fiber was developed for applications in radiation therapy. The diameter of the mounted fiber is 0.25 mm, whereas the length depends on the sensitivity required. To demonstrate the applicability, a customized fiber device was used to determine scattered radiation close to the lens of the eye. Measurements were compared with TLDs (LiF) in an anthropomorphic phantom. The comparison with TLD measurements shows good agreement. In contrast to TLD, optical fibers provide immediate dose values, and the readout procedure is much easier. Owing to its small size and diameter, interesting invasive dose measurements are feasible.

Chondrosarcoma of the larynx: the role of radiotherapy revisited--a case report and review of the literature.

BACKGROUND: Experience in the treatment of laryngeal chondrosarcoma is based on about 250 cases reported to date. The standard therapy is conservative surgery. Radiotherapy has universally been regarded as ineffective in the treatment of this disease. METHODS: A patient with a laryngeal chondrosarcoma was observed for 11 years after radical radiotherapy. The literature on laryngeal chondrosarcoma was critically reviewed, with emphasis placed on radiotherapy. RESULTS: The review of the literature revealed that experience with radiotherapy of laryngeal chondrosarcoma has been lacking, with fewer than 10 cases with short follow-up documented up to now. Meanwhile, increasing evidence of the efficacy of radiotherapy in the treatment of skeletal chondrosarcoma has emerged. The authors report the first case of chondrosarcoma of the larynx in which radical radiotherapy resulted in a long term remission of more than 10 years. CONCLUSIONS: Radiotherapy should be considered when radical surgery is not feasible without severe mutilation. It should also be considered for the treatment of residual disease. Laryngectomy should be restricted to salvage treatment when radiotherapy fails. In this study, radiotherapy appeared to be an effective modality in the treatment of low grade laryngeal chondrosarcoma, and these results contrast with the current widespread disapproval of this treatment.

[Preoperative irradiation and interstitial radiotherapy-hyperthermia boost in breast tumors > or = 3 cm. The Düsseldorf experience]. / Präoperative Bestrahlung mit interstitiellem Radio-hyperthermie-Boost bei Mammatumoren > or = 3 cm. Düsseldorfer Ergebnisse.

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.

[Dosimetric studies using glass fibers]. / Dosimetrische Untersuchungen mit Glasfasern.

PURPOSE: Ionizing radiation may cause discolouring of glasses by creation of colour centers. So radiation induced optical loss is a measure of absorbed dose. With a doped glass fiber a small volume optical dosimeter is developed for clinical purposes providing real time dosimetry with high spatial resolution. MATERIALS AND METHODS: Discolouring of glass by ionizing radiation is dose dependent and can be measured as light attenuation at a fixed wavelength. Light power of usual light emitting diodes (LED) is sufficient for this purpose. The readout light is conducted through a transmission fiber of arbitrary length. Concurrent measurements were performed at several wavelengths (660 to 850 nm) using a time multiplexing technique. We investigated the radiation induced light attenuation of a lead doped silica fiber with 60 Wt-% PbO2, diameter < 0.5 mm, and length < 0.1 m. The fiber was exposed to high energy photons of cesium-137, cobalt-60, 12-MV-photons, and 18-MV-photons generated by a linear accelerator, respectively. The influence of various temperatures, doses, and dose rates was tested. When sensor fiber is termed by a mirror reflected light can be detected with one transmission fiber and optical pathway is doubled. RESULTS: In a wide dose range (0 to 112 Gy) radiation induced loss represents absorbed dose in a linear manner without saturation effects. Optical loss is diminished by partial recovery of radiation damage depending on time and temperature. In order to compensate fading a phenomenological model was fitted to experimental data. Temperature dependence may be corrected by measurements with several readout wavelengths. Above 1 MeV there is merely a slight dependence on photon energy. At a size of the glass fiber reflection sensor of L = 2 cm doses of 0.04 Gy may be detected. The reproducibility at 1 Gy is about 4%. CONCLUSION: Lead doped silica fiber is suitable for radiation dosimetry in a dose range interesting for clinical practice. Fading may be compensated during irradiation using a phenomenological model. The size of a reflection sensor is comparable to thermoluminescence dosimeters. In contrast to TLD glass fiber provides real time dose measurements. By this means optical glass fiber dosimeter may be appropriate for in-vivo dosimetry in radiation therapy.

[Comparison between 2 methods of determining photon-induced air activity around medical accelerators]. / Der Vergleich zweier Methoden zur Bestimmung der photoneninduzierten Luftaktivität an medizinischen Beschleunigern.

The authors compare two different methods to determine the activity of the air induced by the bremsstrahlung of medical accelerators. The activities of the air resulting from maximum photon energies of 16 to 42 MeV are measured with a proportional counter tube ("direct measurement") and by means of activation analyses of imidazole, triazole, malonic acid, and urea specimens ("indirect measurement"). The results are compared.