Hainy, Matthew E

AbstractBackgroundHigh dose rate brachytherapy is commonly used in the treatment of prostate cancer. Treatment planning is often performed under transrectal ultrasound (US) guidance, but brachytherapy needles can be challenging to digitize due to the presence of poor US conspicuity and imaging artifacts. The plan accuracy and quality, however, are dependent on the proper visualization of the needles with millimeter accuracy.PurposeThis work describes a technique for generating a color overlay of needle locations atop the grayscale US image. Prototype devices were developed to produce vibrations in the brachytherapy needles that generate a high contrast color Doppler (CD) signal that highlights the needle locations with superior contrast and reduced artifacts. Denoted by the acronym color VISION (Vibrationally Induced Shimmering for Identifying an Object's Nature), the technology has the potential to improve applicator conspicuity and facilitate automated applicator digitization.MethodsThree prototype vibrational devices with frequencies between 200–450 Hz were designed in‐house and evaluated with needle implants in a phantom and cadaveric male pelvis using: (1) an actuator attached to the front of a prostate needle template; (2) an actuator attached to the top of the needle template; and (3) a hand‐held actuator with a stylet, inserted directly into a needle's inner lumen. Acquired images were postprocessed in MATLAB to evaluate the potential for automated digitization.ResultsAll prototype devices produced localized shimmering in implanted brachytherapy needles in both the axial and sagittal planes. The template mounted actuators provided better vibrational coupling and ease of operation than the stylet prototype. The Michelson contrast, or visibility, of the shimmering CD signal was 100% compared with ≤40% for B‐mode imaging of a single needle. Proof‐of‐principle for automated applicator digitization using only the CD signal was demonstrated.ConclusionsThe color VISION prototype devices successfully coupled mechanical vibrations into brachytherapy needles to generate US CD shimmering and accurately highlight brachytherapy needle locations. The high contrast and natively registered signal are promising for future work to automate the needle digitization and provide a real‐time visual overlay of the applicator on the B‐mode US image.

BACKGROUND: Methacholine bronchoprovocation or challenge testing (MCT) is commonly performed to assess airway hyper-responsiveness in the setting of suspected asthma. Nebulization is an aerosol-generating procedure, but little is known about the risks of MCT in the context of the ongoing coronavirus disease 2019 (COVID-19) pandemic. We aimed to quantify and characterize aerosol generation during MCT by using different delivery methods and to assess the impact of adding a viral filter. METHODS: Seven healthy subjects performed simulated MCT in a near particle-free laboratory space with 4 different nebulizers and with a dosimeter. Two devices continuously sampled the ambient air during the procedure, which detected ultrafine particles, from 0.02–1 μm, and particles of sizes 0.3, 0.5, 1.0, 2.0, 5.0, and 10 µm, respectively. Particle generation was compared among all the devices, with and without viral filter placement. RESULTS: Ultrafine-particle generation during simulated MCT was significant across all the devices. Ultrafine-particle (0.02–1 μm) concentrations decreased 77%–91% with the addition of a viral filter and varied significantly between unfiltered (P < .001) and filtered devices (P < .001). Ultrafine-particle generation was lowest when using the dosimeter with filtered Hudson nebulizer (1,258 ± 1,644 particle/mL). Ultrafine-particle concentrations with the filtered nebulizer devices using a compressor were higher than particle concentrations detected when using the dosimeter: Monaghan (3,472 ± 1,794 particles/mL), PARI (4,403 ± 2,948), Hudson (6,320 ± 1,787) and AirLife (9,523 ± 5,098). CONCLUSIONS: The high particle concentrations generated during MCT pose significant infection control concerns during the COVID-19 pandemic. Particle generation during MCT was significantly reduced by using breath-actuated delivery and a viral filter, which offers an effective mitigation strategy.

BACKGROUND: Peak flow testing is a common procedure performed in ambulatory care. There are currently no data regarding aerosol generation during this procedure. Given the ongoing debate regarding the potential for aerosol transmission of SARS-CoV-2, we aimed to quantify and characterize aerosol generation during peak flow testing. METHODS: Five healthy volunteers performed peak flow maneuvers in a particle-free laboratory space. Two devices continuously sampled the ambient air during the procedure. One device can detect ultrafine particles 0.02–1 μ m in diameter, while the second device can detect particles 0.3, 0.5, 1.0, 2.0, 5.0, and 10 μ m in diameter. Five different peak flow meters were compared to ambient baseline during masked and unmasked tidal breathing. RESULTS: Ultrafine particles (0.02–1 μ m) were generated during peak flow measurement. There was no significant difference in ultrafine particle mean concentration between peak flow meters ( P = .23): Respironics (1.25 ± 0.47 particles/mL), Philips (3.06 ± 1.22), Clement Clarke (3.55 ± 1.22 particles/mL), Respironics Low Range (3.50 ± 1.52 particles/mL), and Monaghan (3.78 ± 1.31 particles/mL). Ultrafine particle mean concentration with peak flow testing was significantly higher than masked (0.22 ± 0.29 particles/mL) and unmasked tidal breathing (0.15 ± 0.18 particles/mL, P = .01), but the ultrafine particle concentrations were small compared to ambient particle concentrations in a pulmonary function testing room (89.9 ± 8.95 particles/mL). CONCLUSIONS: In this study, aerosol generation was present during peak flow testing, but concentrations were small compared to the background particle concentration in the ambient clinical environment. Surgical masks and eye protection are likely sufficient infection control measures during peak expiratory flow testing in asymptomatic patients with well controlled respiratory symptoms, but COVID-19 testing remains prudent in patients with acute respiratory symptoms prior to evaluation and peak expiratory flow assessment while the community prevalence of SARS-CoV-2 cases remains high.