Dosimetry for quantitative analysis of the effects of low-dose ionizing radiation in radiation therapy patients

We have developed and validated a practical approach to identifying the location on the skin surface that will receive a prespecified biopsy dose (ranging down to 1 cGy) in support of in vivo biological dosimetry in humans. This represents a significant technical challenge since the sites lie on the patient's surface outside the radiation fields. The PEREGRINE Monte Carlo simulation system was used to model radiation dose delivery, and TLDs were used for validation on phantoms and for confirmation during patient treatment. In the developmental studies, the Monte Carlo simulations consistently underestimated the dose at the biopsy site by approximately 15% (of the local dose) for a realistic treatment configuration, most likely due to lack of detail in the simulation of the linear accelerator outside the main beam line. Using a single, thickness-independent correction factor for the clinical calculations, the average of 36 measurements for the predicted 1-cGy point was 0.985 cGy (standard deviation: 0.110 cGy) despite patient breathing motion and other real-world challenges. Since the 10-cGy point is situated in the region of high-dose gradient at the edge of the field, patient motion had a greater effect, and the six measured points averaged 5.90 cGy (standard deviation: 1.01 cGy), a difference that is equivalent to approximately a 6-mm shift on the patient's surface. (c) 2006 by Radiation Research Society

Effectiveness and safety of procalcitonin-guided antibiotic therapy in lower respiratory tract infections in "real life": an international, multicenter poststudy survey (ProREAL)

BACKGROUND: In controlled studies, procalcitonin (PCT) has safely and effectively reduced antibiotic drug use for lower respiratory tract infections (LRTIs). However, controlled trial data may not reflect real life. METHODS: We performed an observational quality surveillance in 14 centers in Switzerland, France, and the United States. Consecutive adults with LRTI presenting to emergency departments or outpatient offices were enrolled and registered on a website, which provided a previously published PCT algorithm for antibiotic guidance. The primary end point was duration of antibiotic therapy within 30 days. RESULTS: Of 1759 patients, 86.4% had a final diagnosis of LRTI (community-acquired pneumonia, 53.7%; acute exacerbation of chronic obstructive pulmonary disease, 17.1%; and bronchitis, 14.4%). Algorithm compliance overall was 68.2%, with differences between diagnoses (bronchitis, 81.0%; AECOPD, 70.1%; and community-acquired pneumonia, 63.7%; P > .001), outpatients (86.1%) and inpatients (65.9%) (P > .001), algorithm-experienced (82.5%) and algorithm-naive (60.1%) centers (P > .001), and countries (Switzerland, 75.8%; France, 73.5%; and the United States, 33.5%; P > .001). After multivariate adjustment, antibiotic therapy duration was significantly shorter if the PCT algorithm was followed compared with when it was overruled (5.9 vs 7.4 days; difference, -1.51 days; 95% CI, -2.04 to -0.98; P > .001). No increase was noted in the risk of the combined adverse outcome end point within 30 days of follow-up when the PCT algorithm was followed regarding withholding antibiotics on hospital admission (adjusted odds ratio, 0.83; 95% CI, 0.44 to 1.55; P = .56) and regarding early cessation of antibiotics (adjusted odds ratio, 0.61; 95% CI, 0.36 to 1.04; P = .07). CONCLUSIONS: This study validates previous results from controlled trials in real-life conditions and demonstrates that following a PCT algorithm effectively reduces antibiotic use without increasing the risk of complications. Preexisting differences in antibiotic prescribing affect compliance with antibiotic stewardship efforts. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN40854211

Influence of procalcitonin on decision to start antibiotic treatment in patients with a lower respiratory tract infection: insight from the observational multicentric ProREAL surveillance

Procalcitonin (PCT)-guided antibiotic stewardship is a successful strategy to decrease antibiotic use. We assessed if clinical judgement affected compliance with a PCT-algorithm for antibiotic prescribing in a multicenter surveillance of patients with lower respiratory tract infections (LRTI). Initiation and duration of antibiotic therapy, adherence to a PCT algorithm and outcome were monitored in consecutive adults with LRTI who were enrolled in a prospective observational quality control. We correlated initial clinical judgment of the treating physician with algorithm compliance and assessed the influence of PCT on the final decision to initiate antibiotic therapy. PCT levels correlated with physicians' estimates of the likelihood of bacterial infection (p for trend 0.25 mug/L), in European centers (e.g., in France -22 % if PCT 0.25 mug/L) and in centers, which had previous experience with the PCT-algorithm (-16 % if PCT 0.25 mug/L). Algorithm non-compliance, i.e. antibiotic prescribing despite low PCT-levels, was independently predicted by the likelihood of a bacterial infection as judged by the treating physician. Compliance was significantly associated with identification of a bacterial etiology (p = 0.01). Compliance with PCT-guided antibiotic stewardship was affected by geographically and culturally-influenced subjective clinical judgment. Initiation of antibiotic therapy was altered by PCT levels. Differential compliance with antibiotic stewardship efforts contributes to geographical differences in antibiotic prescribing habits and potentially influences antibiotic resistance rates