Commissioning Siemens Virtual Wedges in the Oncentra MasterPlan treatment planning system using Gafchromic EBT film.

PURPOSE: Virtual Wedges were introduced in Siemens LINACs to improve the treatment workflow. The aim of the present work is the validation of dose calculation by MasterPlan-Oncentra treatment planning system for virtual wedged beams. METHODS: The Oncor Siemens accelerator installed in the authors' department produces 6 and 15 MV photon beams. At first, the consistency of VW LINAC production was tested and the EBT film measuring method was verified. This method is based on the scanner uniformity correction and absolute dose calibration as reported in literature. Then, the measured and calculated wedge factors and beam profiles are compared. For 15 degrees, 30 degrees, 45 degrees, and 60 degrees wedge angles, the wedge factors for different field sizes were measured by an ionization chamber and the dose profiles were acquired by Gafchromic EBT film. Both types of measurements were collected in isocentric condition. RESULTS: The comparison between measured and calculated VW factors shows discrepancies that increase with field size and angle. The OTP Enhanced algorithm produces better agreement with measurements than the Classic one, with improvement overall visible for large angles. The agreement between measured and planned beam profiles is within limits reported by the ESTRO Booklet No. 7 in terms of confidence limits. CONCLUSIONS: The MasterPlan-Oncentra treatment planning system determines wedge factors and VW profiles within the requested accuracy in the majority of treatment conditions. For big field dimensions and wedge angle, wedge factor accordance was worse, but it may be increased with an improvement of the LINAC dosimetric board calibration.

[Cyclophosphamide and total lymph node irradiation as conditioning for bone marrow transplant in severe aplastic anemia]. / Ciclofosfamide (CTX) ed irradiazione linfonodale totale (TNI) come condizionamento al trapianto di midollo osseo (BMT) nelle anemie aplastiche gravi (AAG).

Personal experience is outlined with a preparative regimen consisting of total nodal irradiation (TNI) and cyclophosphamide in patients with severe aplastic anemia undergoing bone marrow transplantation (BMT). Nine patients (median age 23) previously having blood transfusions received BMT at the BMT Center in Pesaro. All patients were prepared for transplantation with cyclophosphamide 50 mg/kg/day (day -6, -5, -4, -3), and 7.5 Gy total nodal irradiation day -1, with a dose rate of 26 cGy/m. Six out of eight evaluable transplanted patients are still surviving 3 to 23 months with a median follow-up of 16.5 months. This preoperative regimen is extremely effective in decreasing rejection following transplantation for severe aplastic anemia. Future investigation must be aimed at the elimination of graft-versus-host-disease and control of fatal infections.

Temporary inhibition of Moloney-murine sarcoma virus (M-MSV) induced-tumours by adoptive transfer of ricin-treated T-lymphocytes.

The potential use of tumour-specific T-lymphocytes loaded with ricin in cell targeting experiments was investigated. Moloney-murine sarcoma virus (M-MSV)-specific T-lymphocytes, obtained in mass mixed leucocyte-tumour cell culture (MLTC) and a M-MSV-specific cytotoxic T-lymphocyte (CTL) clone, were incubated with 125I-labelled ricin in order to evaluate toxin uptake and release. The internalized ricin (4.5 X 10(-17) mol and 6.5 X 10(-17) mol per 10(2) MLTC and CTL clone cells, respectively) was released rapidly during the first 30 min following treatment, and at a constant but slower rate over the next few hours. The cytotoxic activity of ricin-treated cells evaluated against antigen-related target cells, in a short term incubation 51Cr release assay, was unaffected during the first 30 min after treatment but decreased with time over the next few hours. However, the growth of antigen related as well as of unrelated tumour cells was strongly inhibited by the addition of ricin-treated cells to the culture system, thus indicating that released ricin is toxic for untreated target cells. The in vivo localization pattern of ricin-treated radiolabelled MLTC cells was found to be comparable with that of untreated cells 1 h after i.v. injection into syngeneic sublethally irradiated mice. After 6 h, however, more radiolabel was recovered from the liver of mice receiving ricin-treated MLTC cells. Ricin-treated M-MSV-specific T-lymphocytes were injected i.v. into tumour bearing sublethally irradiated mice. A temporary tumour growth inhibition (up to 6 days) was achieved following transfer of low doses of ricin-treated MLTC or CTL clone cells (1 X 10(6) and 0.5 X 10(6), respectively). In contrast, in M-MSV injected control mice, receiving only free toxin (from 5 to 20 ng) or untreated tumour-specific effector cell tumours grew progressively. The therapeutic effect was apparently specific since the injection of ricin-treated alloreactive T-lymphocytes did not influence tumour growth. These results suggest that M-MSV-specific T-lymphocytes loaded with ricin can deliver toxin to the target tumour mass and have a transient therapeutic effect.

[Dosimetry of the bladder and the rectum: comparison between the measured and calculated dose (author's transl)]. / Dosimetria della vescica e del retto: confronto fra le dosi misurate e le dosi calcolate.

The authors examine 62 cases of curietherapy in the deep vagina on 21 cases of utero-vaginal applications and make a comparison between two dosimetric methods used to measure the dose to the rectum and to the bladder: the direct measure by the Siemens Gammameter dosimeter and the Chassagne-Horiot method. Very large differences were found between the doses evaluated by the two methods. The values with the direct measure were often found to be higher than the calculated ones. When the measurements were done by different doctors, the result was almost the same.

[Evidence of an intrinsic defect of lymphocyte reactivity in AKR mice (author's transl)]. / Evidenza di un difetto intrinseco della reattività linfocitaria in topi AKR

Like their AKR/J parent, (CBAT6T6 X AKR/J)F1 mice are carriers of endogenous G-MuLV and present a high incidence of spontaneous lymphoma. However, the F1 hybrids do not present the immunological deficits seen in pre-leukemic AKR/J mice since they respond normally to in vitro PHA stimulation and to in vivo LPS immunization. These observations suggest that there is probably no direct relationship between the presence of MuLV and immunological impairment. Studies have been carried out to ascertain whether the altered immunological reactivity seen in AKR/J mice is related to factors intrinsic to the immunocompetent cells or to environmental inadequacy. Thus, (CBAT6T6 X AKR/J)F1 mice were thymectomized, irradiated, reconstituted with syngeneic bone marrow and simultaneous transplant of CBAT6T6 and AKR/J thymus, and their lymphocyte response to PHA was assayed. In addition, antibody production following LPS immunization was studied by transferring AKR/J splenic cells to irradiated CBA6T6 or (CBAT6T6 X AKR/J)F1 mice, and vice-versa. The results of these investigations indicate that an intrinsic lymphocyte hyporeactivity is present in AKR/J mice and environmental factors do not modify the reactivity of the transferred immunocompetent cells.