Absorbed dose to water determination with ionization chamber dosimetry and calorimetry in restricted neutron, photon, proton and heavy-ion radiation fields.

Absolute dose measurements with a transportable water calorimeter and ionization chambers were performed at a water depth of 20 mm in four different types of radiation fields, for a collimated (60)Co photon beam, for a collimated neutron beam with a fluence-averaged mean energy of 5.25 MeV, for collimated proton beams with mean energies of 36 MeV and 182 MeV at the measuring position, and for a (12)C ion beam in a scanned mode with an energy per atomic mass of 430 MeV u(-1). The ionization chambers actually used were calibrated in units of air kerma in the photon reference field of the PTB and in units of absorbed dose to water for a Farmer-type chamber at GSI. The absorbed dose to water inferred from calorimetry was compared with the dose derived from ionometry by applying the radiation-field-dependent parameters. For neutrons, the quantities of the ICRU Report 45, for protons the quantities of the ICRU Report 59 and for the (12)C ion beam, the recommended values of the International Atomic Energy Agency (IAEA) protocol (TRS 398) were applied. The mean values of the absolute absorbed dose to water obtained with these two independent methods agreed within the standard uncertainty (k = 1) of 1.8% for calorimetry and of 3.0% for ionometry for all types and energies of the radiation beams used in this comparison.

[Endoresection following proton beam irradiation of large uveal melanomas]. / Endoresektion von grossen uvealen Melanomen nach Protonenbestrahlung.

PURPOSE: Large uveal melanomas located close to the optic nerve and/ or to the fovea have an unfavourable prognosis with regard to visual preservation and eye retention, due to the high incidence of radiation and tumour necrosis induced complications. Endoresection of the tumour after proton beam irradiation, is an alternative approach, aiming to reduce the incidence of ocular morbidity caused by tumour necrosis after sole radiotherapy. PATIENTS AND METHODS: 32 patients with large uveal melanomas (mean tumour thickness: 9.1 mm, mean tumour volume: 0.77 cc), received a primary proton beam irradiation (60 CGE) and underwent subsequent endoresection via a 3-port pars plana vitrectomy. The median pretreatment visual acuity was 0.2. The mean follow-up was 13.9 months. RESULTS: The postoperative visual acuity after 12 months was 0.12 (median, mean visual acuity loss 0.08). The probability of developing radiation retinopathy or papillopathy within the first year after treatment was 35% and 28% respectively and the probability of enucleation was 9% within the first postoperative year. No tumour recurrences were observed and 2 patients developed liver metastases. CONCLUSIONS: Endoresection following irradiation of large uveal melanomas located close to the optic nerve and/ or the fovea seems to be a useful and safe alternative to the traditional irradiation or enucleation. The incidence of complications following our approach seems to be lower when compared to radiation alone, where tumour necrosis is a substantial problem.

Use of BANG polymer gel for dose measurements in a 68 MeV proton beam.

BANG polymer gel dosimetry using magnetic resonance imaging (MRI) was applied to an ophthalmologic 68 MeV proton beam. The object was to examine the use of BANG gel for the verification of proton fields in eye tumor therapy and to explore the applicability of polymer gel dosimetry in proton therapy under practical aspects. The gel phantoms were irradiated with monoenergetic and modulated proton beams. MRI analysis was carried out at clinical 1.5 and 3 T MR scanners. At constant LET, results show a linear relationship between spin-spin relaxation rates and dose. However, depth dose curves in BANG gel reveal a quenching of the Bragg maximum due to LET effects. The dose response of the gel for monoenergetic protons and spread-out depth dose distributions can be calculated based on ionization chamber measurements. Experiment and calculations show good agreement and indicate that BANG polymer gels might become a valuable tool in proton therapy quality assurance.

Specimen fine-needle aspiration cytology of littoral cell angioma with histologic and immunohistochemical confirmation.

We performed a specimen fine-needle aspiration biopsy (FNAB) of a littoral cell angioma (LCA) from a 33-yr-old male who underwent elective splenectomy due to thrombocytopenia secondary to Wiscott-Aldrich syndrome. Gross examination revealed a 420-g, diffusely enlarged spleen which contained two moderately well-circumscribed, soft brown lesions measuring 0.3 and 1.0 cm, respectively. Benchtop aspiration of the lesions following splenectomy yielded a cellular sample composed predominantly of dispersed single cells, which ranged from columnar to spindle to circariform in shape. Nuclei were round to oval with even chromatin, and many contained single longitudinal grooves. A majority of the cells contained abundant, granular hemosiderin pigment, a key cytologic feature. Immunohistochemical staining revealed reactivity for antibodies to CD68 and factor VIII-related antigen with no reactivity for S-100 protein and CD8. Littoral cell angioma must be differentiated from splenic hamartoma, hemangioma, angiosarcoma, littoral cell angiosarcoma, and epithelioid and spindle cell hemangioendothelioma. A combination of cytologic features and immunohistochemical results should enable an accurate diagnosis.

Proton dosimetry intercomparison based on the ICRU report 59 protocol.

BACKGROUND AND PURPOSE: A new protocol for calibration of proton beams was established by the ICRU in report 59 on proton dosimetry. In this paper we report the results of an international proton dosimetry intercomparison, which was held at Loma Linda University Medical Center. The goals of the intercomparison were, first, to estimate the level of consistency in absorbed dose delivered to patients if proton beams at various clinics were calibrated with the new ICRU protocol, and second, to evaluate the differences in absorbed dose determination due to differences in 60Co-based ionization chamber calibration factors. MATERIALS AND METHODS: Eleven institutions participated in the intercomparison. Measurements were performed in a polystyrene phantom at a depth of 10.27 cm water equivalent thickness in a 6-cm modulated proton beam with an accelerator energy of 155 MeV and an incident energy of approximately 135 MeV. Most participants used ionization chambers calibrated in terms of exposure or air kerma. Four ionization chambers had 60Co-based calibration in terms of absorbed dose-to-water. Two chambers were calibrated in a 60Co beam at the NIST both in terms of air kerma and absorbed dose-to-water to provide a comparison of ionization chambers with different calibrations. RESULTS: The intercomparison showed that use of the ICRU report 59 protocol would result in absorbed doses being delivered to patients at their participating institutions to within +/-0.9% (one standard deviation). The maximum difference between doses determined by the participants was found to be 2.9%. Differences between proton doses derived from the measurements with ionization chambers with N(K)-, or N(W) - calibration type depended on chamber type. CONCLUSIONS: Using ionization chambers with 60Co calibration factors traceable to standard laboratories and the ICRU report 59 protocol, a distribution of stated proton absorbed dose is achieved with a difference less than 3%. The ICRU protocol should be adopted for clinical proton beam calibration. A comparison of proton doses derived from measurements with different chambers indicates that the difference in results cannot be explained only by differences in 60Co calibration factors.

Proton dosimetry intercomparison.

BACKGROUND AND PURPOSE: Methods for determining absorbed dose in clinical proton beams are based on dosimetry protocols provided by the AAPM and the ECHED. Both groups recommend the use of air-filled ionization chambers calibrated in terms of exposure or air kerma in a 60Co beam when a calorimeter or Faraday cup dosimeter is not available. The set of input data used in the AAPM and the ECHED protocols, especially proton stopping powers and w-value is different. In order to verify inter-institutional uniformity of proton beam calibration, the AAPM and the ECHED recommend periodic dosimetry intercomparisons. In this paper we report the results of an international proton dosimetry intercomparison which was held at Loma Linda University Medical Center. The goal of the intercomparison was two-fold: first, to estimate the consistency of absorbed dose delivered to patients among the participating facilities, and second, to evaluate the differences in absorbed dose determination due to differences in 60Co-based ionization chamber calibration protocols. MATERIALS AND METHODS: Thirteen institutions participated in an international proton dosimetry intercomparison. The measurements were performed in a 15-cm square field at a depth of 10 cm in both an unmodulated beam (nominal accelerator energy of 250 MeV) and a 6-cm modulated beam (nominal accelerator energy of 155 MeV), and also in a circular field of diameter 2.6 cm at a depth of 1.14 cm in a beam with 2.4 cm modulation (nominal accelerator energy of 100 MeV). RESULTS: The results of the intercomparison have shown that using ionization chambers with 60Co calibration factors traceable to standard laboratories, and institution-specific conversion factors and dose protocols, the absorbed dose specified to the patient would fall within 3% of the mean value. A single measurement using an ionization chamber with a proton chamber factor determined with a Faraday cup calibration differed from the mean by 8%. CONCLUSION: The adoption of a single ionization chamber dosimetry protocol and uniform conversion factors will establish agreement on proton absorbed dose to approximately 1.5%, consistent with that which has been observed in high-energy photon and electron dosimetry.

[Synthesis of germinal 3,3-dithienyl compounds (author's transl)]. / Synthese geminaler 3,3-dithienylverbindungen.

A new synthetic approach to the cerebroactive compound (+)-(R)-alpha-[(S)-1-[(3,3-di-3-thienylallyl)amino]ethyl]benzyl alcohol(1) (tinofedrine), its stereoisomers and related derivatives is reported. Several compounds increased blood flow in the arteriae vertebralis and femoralis of anesthesized dog.

[Spectroscopic characterisation of tinofedrine (author's transl)]. / Spektroskopische Charakterisierung von Tinofedrin.

With the aid of spectroscopical methods the structure of (+)-(R)-alpha-[(S)-1-[(3,3-di-3-thienylallyl)amino]-ethyl]-benzyl-alcohol (tinofedrine, 1), a new cerebrally active compound, was confirmed. The relative and absolute configuration is discussed in view of spectroscopic data.