Multi-transversal mode pumping of narrow-bandwidth backward wave optical parametric oscillator.

A stable, narrow-bandwidth (274 MHz) backward wave optical parametric oscillator (BWOPO) generating mJ-level backward signal at 1885nm and forward idler at 2495 nm is presented. The BWOPO was pumped by a single-longitudinal mode, Q-switched Nd:YAG high-energy laser at 1064 nm. We show that multi-transversal mode pumping leads to the spectral broadening of the BWOPO backward signal and the generation of nanosecond pulses 2.7 times above the Fourier transform limit. We demonstrate over 100 GHz continuous tuning of the parametric output by adjusting the temperature of the BWOPO crystal, showcasing the significant role of thermal expansion in tuning performance. The BWOPO signal was used as a seed for a single-stage PPRKTP optical parametric amplifier (OPA) to boost the narrowband signal and idler energies to 20 mJ. This combination of mJ-level BWOPO seed with a single-stage PPRKTP OPA comprises a simple concept that would benefit long-range differential absorption lidar (DIAL) in the near and mid-infrared regions.

COVID-19 outbreak impact on health professionals: A survey on the Italian radiographer experience.

AIM: To evaluate the impact of the Phase 1 COVID-19 (C19) outbreak on Italian Radiographers. MATERIAL AND METHODS: COVID-19 has spread rapidly worldwide. Many patients underwent radiological examinations, leading to a high risk of infection within the radiology department's staff. Italy was the first-hit European country to face the COVID-19 outbreak and the impact on radiographers was huge. An online survey was disseminated to investigate the involvement and working environment of Italian radiographers during the first outbreak of COVID-19. RESULTS: Of the 840 responders, 65% were men. The majority of the responding Health-care Workers (HCW) was represented by radiographers (96%), from high-prevalence regions (82%; p<.05). Forty-five percent were involved in the activation of the protocol for the management of COVID-19 positive patients, without exhaustive indication for Plain Radiography and Computed Tomography (CT). Only 17% of hospitals counted on available guidelines for serious infections (p<0.05). Diagnostic examinations were mainly performed by a single radiographer (62%). Many professionals (69%) confirmed wearing all indispensable PPE in case of COVID-19 positive patients. CONCLUSION: The primary objective of management strategies should be to redact standardized policies for the safeguarding of patient's health and operator's safety. All front-line workers, including radiographers working in diagnostic services, should be involved in the decision-making process to generate wellness and awareness.

Patient Perceptions and Knowledge of Ionizing Radiation From Medical Imaging.

Importance: Although imaging has become a standard tool of modern medicine, its widespread use has been paralleled by an increasing cumulative radiation dose to patients despite technological advancements and campaigns calling for better awareness and minimization of unnecessary exposures. Objective: To assess patients' knowledge about medical radiation and related risks. Design, Setting, and Participants: A survey study of hospitals in Italy was conducted; all patients in waiting rooms for medical imaging procedures before undergoing imaging examinations at 16 teaching and nonteaching hospitals were approached to take the survey. The survey was performed from June 1, 2019, to May 31, 2020. Main Outcomes and Measures: Survey respondents' basic knowledge of ionizing radiation levels and health risks, earlier imaging tests performed, and information and communication about radiation protection issues. Results: Among 3039 patients invited to participate, the response rate was 94.3% (n = 2866). Participants included 1531 women (53.4%); mean (SD) age was 44.9 (17.3) years. Of the 2866 participants, 1529 (53.3%) were aware of the existence of natural sources of ionizing radiation. Mammography (1101 [38.4%]) and magnetic resonance imaging (1231 [43.0%]) were categorized as radiation-based imaging modalities. More than half of the 2866 patients (1579 [55.1%]; P = .03) did not know that chest computed tomography delivers a larger dose of radiation than chest radiography, and only 1499 (52.3%) knew that radiation can be emitted after nuclear medicine examinations (P = .004). A total of 667 patients (23.3%) believed that radiation risks were unrelated to age, 1273 (44.4%) deemed their knowledge about radiation risks inadequate, and 2305 (80.4%) preferred to be informed about radiation risks by medical staff. A better knowledge of radiation issues was associated with receiving information from health care professionals (odds ratio [OR], 1.71; 95% CI, 1.43-2.03; P < .001) and having a higher educational level (intermediate vs low: OR, 1.48; 95% CI, 1.17-1.88; P < .001; high vs low: OR, 2.68; 95% CI, 2.09-3.43; P < .001). Conclusions and Relevance: The results of this survey suggest that patients undergoing medical imaging procedures have overall limited knowledge about medical radiation. Intervention to achieve better patient awareness of radiation risks related to medical exposures may be beneficial.

Effect of CT Localizer Radiographs on Radiation Dose Associated With Automatic Tube Current Modulation: A Multivendor Study.

OBJECTIVES: To assess the influence of the CT localizer radiograph on the automatic tube current modulation system of 7 CT scanners produced by 4 different CT manufacturers. METHODS: The influence of the localizer orientation, table height, tube current and tube potential values on the radiation dose of the related CT scan were evaluated. Images were acquired by using an anthropomorphic phantom positioned in the CT gantry isocenter as well as from -6 cm to +6 cm vertically to the isocenter. RESULTS: Vertical movement of the CT table height affected the radiation dose in all scanners using anterior-posterior or a posterior-anterior localizer orientation albeit differently, depending on the manufacturer; only in 1/7 scanner no influence was observed. The latero-lateral localizer orientation proved to be more effective in limiting the influence of the vertical miscentering in all scanners. Changing localizer's tube voltage influenced the scan radiation dose in scanners produced by two manufacturers, while no significant effect was observed in scanners produced by the other two manufacturers. No significant dose variation was observed in 6/7 scanners when changing the localizer's tube current. CONCLUSION: Localizer radiograph shows a significant influence on the radiation exposure but with different outcomes depending on the manufacturer of the CT scanner. Radiologists and radiographers should have a thorough understanding of these differences to assure patients the best examination in terms of radiation dose and image quality.

Jitter investigation of narrow-bandwidth passively Q-switched Nd:YAG unidirectional ring laser.

A passively Q-switched Nd:YAG undirectional ring laser with external feedback is reported. The laser generates 50 ns single-axial-mode pulses up to 6 kHz, with energy 34 µJ, M2<1.05, and pulse jitter <50 ns rms, which is quite remarkable for this class of devices. Jitter was effectively minimized by using relatively high-peak-power pump pulses of 10 W, in agreement with a model considering both pump fluctuations and spontaneous emission noise. This represents an improvement by a factor of 8 with respect to a similar laser device we recently reported.

Passively Q-switched single-frequency Nd:YVO4 ring laser with external feedback.

A compact diode-pumped Nd:YVO4 ring laser was developed for generation of relatively long (few tens nanoseconds) single-frequency pulses for high-spectral-resolution LIDAR applications. Exploiting the feedback from an external mirror and Cr:YAG passive Q-switching with pulsed pump, unidirectional single-frequency operation with high quality ∼50-ns, 80-µJ TEM00 pulses was achieved from 100 Hz to 10 kHz. Amplitude, duration and repetition rate stability of the pulses was better than 1%.