Pilot scale validation campaign of gel dosimetry for pre-treatment quality assurance in stereotactic radiotherapy.

PURPOSE: Complex stereotactic radiotherapy treatment plans require prior verification. A gel dosimetry system was developed and tested to serve as a high-resolution 3D dosimeter for Quality Assurance (QA) purposes. MATERIALS AND METHODS: A modified version of a polyacrylamide polymer gel dosimeter based on chemical response inhibition was employed. Different sample geometries (cuvettes and phantoms) were manufactured for calibration and QA acquisitions. Irradiations were performed with a Varian Trilogy linac, and analyses of irradiated gel dosimeters were performed via MRI with a 1.5 T Philips Achieva at 1 mm3 or 2 mm3 isotropic spatial resolution. To assess reliability of polymer gel data, 54 stereotactic clinical treatment plans were delivered both on dosimetric gel phantoms and on the Delta4 dosimeter. Results from the two devices were evaluated through a global gamma index over a range of acceptance criteria and compared with each other. RESULTS: A quantitative and tunable control of dosimetric gel response sensitivity was achieved through chemical inhibition. An optimized MRI analysis protocol allowed to acquire high resolution phantom dose data in timeframes of ≈ 1 h. Conversion of gel dosimeter data into absorbed dose was achieved through internal calibration. Polymer gel dosimeters (2 mm3 resolution) and Delta4 presented an agreement within 4.8 % and 2.7 % at the 3 %/1 mm and 2 %/2 mm gamma criteria, respectively. CONCLUSIONS: Gel dosimeters appear as promising tools for high resolution 3D QA. Added complexity of the gel dosimetry protocol may be justifiable in case of small target volumes and steep dose gradients.

Outcomes from patients with presumed drug resistant tuberculosis in five reference centers in Brazil.

BACKGROUND: The implementation of rapid drug susceptibility testing (DST) is a current global priority for TB control. However, data are scarce on patient-relevant outcomes for presumptive diagnosis of drug-resistant tuberculosis (pDR-TB) evaluated under field conditions in high burden countries. METHODS: Observational study of pDR-TB patients referred by primary and secondary health units. TB reference centers addressing DR-TB in five cities in Brazil. Patients age 18 years and older were eligible if pDR-TB, culture positive results for Mycobacterium tuberculosis and, if no prior DST results from another laboratory were used by a physician to start anti-TB treatment. The outcome measures were median time from triage to initiating appropriate anti-TB treatment, empirical treatment and, the treatment outcomes. RESULTS: Between February,16th, 2011 and February, 15th, 2012, among 175 pDR TB cases, 110 (63.0%) confirmed TB cases with DST results were enrolled. Among study participants, 72 (65.5%) were male and 62 (56.4%) aged 26 to 45 years. At triage, empirical treatment was given to 106 (96.0%) subjects. Among those, 85 were treated with first line drugs and 21 with second line. Median time for DST results was 69.5 [interquartile - IQR: 35.7-111.0] days and, for initiating appropriate anti-TB treatment, the median time was 1.0 (IQR: 0-41.2) days. Among 95 patients that were followed-up during the first 6 month period, 24 (25.3%; IC: 17.5%-34.9%) changed or initiated the treatment after DST results: 16/29 MDRTB, 5/21 DR-TB and 3/45 DS-TB cases. Comparing the treatment outcome to DS-TB cases, MDRTB had higher proportions changing or initiating treatment after DST results (p = 0.01) and favorable outcomes (p = 0.07). CONCLUSIONS: This study shows a high rate of empirical treatment and long delay for DST results. Strategies to speed up the detection and early treatment of drug resistant TB should be prioritized.

Breast cancer electron intraoperative radiotherapy: assessment of preoperative selection factors from a retrospective analysis of 758 patients and review of literature.

PURPOSE: To report our experience with full-dose 21 Gy IORT in early breast cancer patients after breast-conserving surgery to define most important selection factors. METHODS: Seven hundred and fifty eight patients, subjected to conserving surgery and IORT, were retrospectively analyzed evaluating most important clinical outcomes. RESULTS: Median follow up was 5.2 years. Results from Cox analyses defined 2 groups of patients, "suitable" (age > 50 years, non lobular histology, tumour size ≤ 2 cm, pN0 or pNmic, ki67 ≤ 20%, non triple negative receptor status and G1-G2) and "unsuitable" for IORT, with a higher rate of breast related events moving from "suitable" to "unsuitable" group. The 5 year rate of IBR is 1.8% in suitable group with significant differences versus unsuitable (1.8 vs. 11.6%, p < 0.005). Same differences between two groups were evidenced in true local relapse (0.6 vs. 6.9%, p < 0.005) and in new ipsilateral BC (1.1 vs. 4.7%, p < 0.015). CONCLUSIONS: In our current practice we consider the following preoperative factors to select patients suitable for IORT: age > 50 years, absence of lobular histology, tumor size ≤ 2 cm, pN0 or pNmic, according to APBI consensus statement, including also ki67 ≤ 20%, non triple negative receptor status and G1-G2.

[Study of occupational exposure to magnetic fields among operators of magnetic resonance scanning at the Papa Giovanni XXIII Hospital (Bergamo)]. / Studio dell' esposizione lavorativa ai campi magnetici degli operatori presso i siti di risonanza magnetica dell Azienda Ospedaliera Papa Giovanni XXIII di Bergamo.

BACKGROUND: In this study occupational exposure to static magnetic fields of 1T and 1.5 T MR scanners installed at Azienda Ospedaliera Papa Giovanni XXIII, Bergamo, Italy, was assessed and the results were compared with the limits for worker's exposure to static magnetic field currently applicable in Italy (Attachment 1 of D.M. 02/08/91). OBJECTIVES: The aim of the study was to assess current occupational exposure to static magnetic fields at 1T and 1.5 T MRI scanner sites and to predict exposure using the new 3 T MR equipment due to come into operation shortly. METHODS: Measurements were performed sampling the static magnetic field experienced by workers while carrying out their tasks by means of a Hall effect probe. All together, 167 measurements were obtained for 29 workers (11 healthcare assistants, 14 radiography technicians and 4 anaesthesiologists). RESULTS: The results showed wide variations of occupational exposure parameters according to the worker's job, type of procedure and patient's state. Nevertheless, it was possible to confirm that the regulatory limits were observed in all cases: the time spent by workers in the zone of the magnet room where B > 200 mT was much shorter than the limit of 1 hour a day prescribed by Italian law (D.M 02/08/91) and the maximum time variation of B (dB/dt) was at least 4 times lower than the value of 6 T/s taken as the health safety threshold in DM 3/8/93. CONCLUSIONS: The data collected suggest that compliance with exposure limits prescribed by Italian law will also be met with the new 3 T MR.