A practical tool to evaluate dose distributions using radiochromic film in radiation oncology.

PURPOSE: Triple channel algorithm and specific procedures make more reliable radiochromic dosimetry for treatment planning verification and quality assurance in radiation therapy. A tool to obtain radiochromic dose distributions and compare them with the ones resulting from a treatment planning system was developed and applied. METHODS: The tool was developed as Microsoft Excel macro; it builds dose calibration curves against net optical density of Gafchromic EBT3 film, produces axial, coronal and sagittal dose maps and allows to evaluate them against dose distributions calculated by the Varian treatment planning system Eclipse using gamma index and gamma angle. RESULTS: The net optical density standard errors of estimate of calibration curves at 6 MV Varian DBX600 linac energy were 0.2%, 0.4% and 0.2% for the red, green and blue channels. Tests of these curves by means of three independent eight dose points measurement series, at 15 MV and 6 MV Varian 2100C linac and at 6 MV DBX600 linac energies, showed less than 2% of dose errors for the red channel and less than 3% for the green channel in the range 100-450 cGy. The comparisons between dose distributions from Gafchromic EBT3 triple channel algorithm and the ones from Eclipse analytic anisotropic algorithm (AAA) showed values of gamma index 95th percentile between 0.6 and 1.0. CONCLUSION: The obtained results encourage the application of this tool in radiation therapy quality assurance.

[Nail pigmentation caused by azidothymidine]. / Pigmentazione ungueale indotta da azidotimidina.

Azidothymidine is a new antiviral drug that acts by competitive inhibition of reverse transcriptase of retroviruses. Azidothymidine is now widely used in treatment of patients with AIDS or ARC; the most important side effects of this drug are anaemia and neutropenia. Recently pigmentary changes of the nails (diffuse pigmentation and longitudinal or transverse bands) provoked by azidothymidine-treatment have also been reported. We describe a such case.

Value of two-dimensional echocardiography in the identification of pulmonary hypertension in chronic obstructive lung disease.

Thirty-three patients suffering from chronic obstructive lung disease (COLD) were submitted to right heart two-dimensional echocardiographic (2D-ECHO) and hemodynamic study. By the subcostal approach, the right ventricle outflow tract including the pulmonary vessels was visualized in 85% of the patients. Most parameters measured on the right ventricle and pulmonary vessels were significantly higher than those recorded in the healthy control group. Very significant correlations were observed between the mean pulmonary artery pressure (PAP) and the following 2D-ECHO parameters: diameter of the pulmonary artery at valve level (r = 0.62; p less than 0.001); supravalvular diameter of the pulmonary artery (r = 0.44; p less than 0.03); diameter of the left branch of the pulmonary artery (r = 0.48; p less than 0.05); diameter of the right branch of the pulmonary artery (r = 0.39; p less than 0.05), and between the PAP and PaO2 (r = -0.66; p less than 0.001). Furthermore, the sensitivity, specificity, and accuracy of 2D-ECHO measurements were calculated to assess the presence of pulmonary hypertension. Overall sensitivity was 65%, specificity 75%, and accuracy 67%. However, by combining the value of PaO2 with that of the pulmonary valve by means of the multiple regression analysis, sensitivity increased to 84% in identifying pulmonary hypertension. Such data demonstrate that the 2D-ECHO study of the right heart in COLD patients has to carefully measure the dimensions of the pulmonary valve and the great pulmonary vessels, as their modification are mainly linked with the presence of pulmonary hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)

[Chernobyl accident: dosimetric evaluation and estimation of risks]. / Incidente di Chernobyl. Valutazioni dosimetriche e stime dei rischi.

The results of dosimetric evaluations carried out after Chernobyl accident in the Health Physics Department of Niguarda Ca' Granda Hospital (Milan) on air, rain and ground contamination are presented. The results obtained show that the incidence of stochastic late effects, both somatic and genetic, will be so low that practically will not be distinguishable from "natural" incidence.