Anderson, Sarah E

Background: Balance assessment is used by clinicians as part of athlete concussion screening. The King-Devick (K-D) Balance app is designed to provide an objective balance assessment value. The purpose of this study was to investigate the responsiveness of a balance assessment using the K-D Balance app. Hypothesis: The K-D Balance app will demonstrate acceptable responsiveness for balance assessment. Study Design: Repeated-measures study. Level of Evidence: Level 5. Methods: A convenience sample of 25 participants between the ages of 20 and 25 years completed testing procedures. A battery of balance tests using the K-D Balance app on an iPhone were conducted 1 week apart. After a 5-minute warm-up, 3 stances were assessed: double leg, tandem right, and tandem left. The K-D Balance app guided the test positions and test times. A value representing movement was generated by the app algorithm. Analysis included descriptive statistics along with intraclass correlation coefficient and minimal detectable change (MDC). Results: The median score of the K-D test was 0.5 for session 1 and 0.4 for session 2. The ICC was 0.42 (95% CI, 0.04-0.70), and the MDC was 1.58. Conclusion: The MDC value of 1.58 represents the threshold of meaningful change in balance, as measured with the K-D Balance app. Clinical Relevance: Clinicians can use the results of this study to objectively assess changes in balance over time using the K-D Balance app.

PurposeMicrodosimetry is a vital tool for assessing the microscopic patterns of energy deposition by radiation, which ultimately govern biological effect. Solid‐state, silicon‐on‐insulator microdosimeters offer an approach for making microdosimetric measurements with high spatial resolution (on the order of tens of micrometers). These high‐resolution, solid‐state microdosimeters may therefore play a useful role in characterizing proton radiotherapy fields, particularly for making highly resolved measurements within the Bragg peak region. In this work, we obtain microdosimetric measurements with a solid‐state microdosimeter (MicroPlus probe) in a clinical, spot‐scanning proton beam of small spot size.MethodsThe MicroPlus probe had a 3D single sensitive volume on top of silicon oxide. The sensitive volume had an active cross‐sectional area of 250 μm × 10 μm and thickness of 10 μm. The proton facility was a synchrotron‐based, spot‐scanning system with small spot size (σ ≈ 2 mm). We performed measurements with the clinical beam current (≈1 nA) and had no detected pulse pile‐up. Measurements were made in a water‐equivalent phantom in water‐equivalent depth (WED) increments of 0.25 mm or 1.0 mm along pristine Bragg peaks of energies 71.3 MeV and 159.9 MeV, respectively. For each depth, we measured lineal energy distributions and then calculated the dose‐weighted mean lineal energy, . The measurements were repeated for two field sizes: 4 × 4 cm2 and 20 × 20 cm2.ResultsFor both 71.3 MeV and 159.9 MeV and for both field sizes, increased with depth toward the distal edge of the Bragg peak, a result consistent with Monte Carlo calculations and measurements performed elsewhere. For the 71.3 MeV, 4 × 4 cm2 beam (range at 80% distal falloff, R80 = 3.99 cm), we measured keV/μm at WED = 2 cm, and keV/μm at WED = 3.95 cm. For the 71.3 MeV, 20 × 20 cm2 beam, we measured keV/μm at WED = 2.6 cm, and keV/μm at WED = 3 cm. For the 159.9 MeV, 4 × 4 cm2 beam (R80 = 17.7 cm), keV/μm at WED = 5 cm, and keV/μm at WED = 17.6 cm. For the 159.9 MeV, 20 × 20 cm2 beam, keV/μm at WED = 5 cm, and keV/μm at WED = 17.6 cm.ConclusionsWe performed microdosimetric measurements with a novel solid‐state, silicon‐on‐insulator microdosimeter in a clinical spot‐scanning proton beam of small spot size and unmodified beam current. For all of the proton field sizes and energies considered, the measurements of were in agreement with expected trends. Furthermore, we obtained measurements with a spatial resolution of 10 μm in the beam direction. This spatial resolution greatly exceeded that possible with a conventional gaseous tissue‐equivalent proportional counter and allowed us to perform a high‐resolution investigation within the Bragg peak region. The MicroPlus probe is therefore suitable for applications in proton radiotherapy.

Background— This study sought to investigate external photon beam radiation for catheter-free ablation of the atrioventricular junction in intact pigs. Methods and Results— Ten pigs were randomized to either sham irradiation or irradiation of the atrioventricular junction (55, 50, 40, and 25 Gy). Animals underwent baseline electrophysiological evaluation, cardiac gated multi-row computed tomographic imaging for beam delivery planning, and intensity-modulated radiation therapy. Doses to the coronary arteries were optimized. Invasive follow-up was conducted ≤4 months after the irradiation. A mean volume of 2.5±0.5 mL was irradiated with target dose. The mean follow-up length after irradiation was 124.8±30.8 days. Out of 7 irradiated animals, complete atrioventricular block was achieved in 6 animals of all 4 dose groups (86%). Using the same targeting margins, ablation lesion size notably increased with the delivered dose because of volumetric effects of isodose lines around the target volume. The mean macroscopically calculated atrial lesion volume for all 4 dose groups was 3.8±1.1 mL, lesions extended anteriorly into the interventricular septum. No short-term side effects were observed. No damage was observed in the tissues of the esophagus, phrenic nerves, or trachea. However, histology revealed in-field beam effects outside of the target volume. Conclusions— Single-fraction doses as low as 25 Gy caused a lesion with interruption of cardiac impulse propagation using this respective target volume. With doses of ≤55 Gy, maximal point-doses to coronary arteries could be kept <7Gy, but target conformity of lesions was not fully achieved using this approach.