Impact of flattening-filter-free radiation on the clonogenic survival of astrocytic cell lines.

BACKGROUND AND PURPOSE: Flattening-filter-free (FFF) beams are increasingly used in radiotherapy as delivery times can be substantially reduced. However, the relative biologic effectiveness (RBE) of FFF may be increased relative to conventional flattened (FLAT) beams due to differences in energy spectra. Therefore, we investigated the effects of FFF and FLAT beams on the clonogenic survival of astrocytoma cells. MATERIAL AND METHODS: Three cell lines (U251, U251-MGMT, and U87) were irradiated with 6-MV and 10-MV X-rays from a linear accelerator in FFF- or FLAT-beam modes at dose rates in the range of 0.5-24 Gy/min. The surviving fraction (SF) as function of dose (2-12 Gy) was determined by the colony formation assay and fitted by the linear-quadratic model. For both beams (FFF or FLAT), the cells were pelleted in conical 15-ml centrifuge tubes and irradiated at 2-cm depth in a 1 × 1-cm(2) area on the central axis of a 30 × 30-cm(2) field. Dosimetry was performed with a 0.3-cm(3) rigid ionization chamber. RBE was determined for FFF versus FLAT irradiation. RESULTS: The RBE of FFF at 7.3-11.3 Gy was 1.027 ± 0.013 and 1.063 ± 0.018 relative to FLAT beams for 6- and 10-MV beams, respectively, and was only significantly higher than 1 for 10 MV. Significantly increased survival rates were seen for lower dose rates (0.5 Gy/min FLAT vs. 5 Gy/min FLAT) at higher doses (11.9 Gy), while no differences were seen at dose rates ≥ 1.4 Gy/min (1.4 Gy/min FFF vs. 14 Gy/min FFF and 2.4 Gy/min FFF vs. 24 Gy/min FFF). CONCLUSIONS: FFF beams showed only a slightly increased RBE relative to FLAT beams in this experimental set-up, which is unlikely to result in clinically relevant differences in outcome.

Thrombotic complications and thromboprophylaxis across all three stages of single ventricle heart palliation.

OBJECTIVES: To describe the incidence of thrombotic complications across all 3 stages of single ventricle palliation and the association between thromboprophylaxis use and thrombotic risk. STUDY DESIGN: Two separate cross-sectional studies were performed that included 195 patients born between 2003-2008 and 162 patients who underwent Fontan after 2000. RESULTS: The incidence of thrombotic complications was 40% and 28% after initial palliation and superior cavopulmonary connection (SCPC), respectively; 5-year freedom from thrombotic complications after Fontan was 79%. Thromboprophylaxis was initiated for 70%, 46%, and 94% of patients after initial palliation, SCPC, and Fontan, respectively. Thromboprophylaxis with enoxaparin (vs no thromboprophylaxis) was associated with a reduction in risk of thrombotic complications after initial palliation (hazard ratio [HR] 0.5, P = .05) and SCPC (HR 0.2, P = .04). Thromboprophylaxis with warfarin was associated with a reduction in thrombotic complications after Fontan (HR 0.27, P = .05 vs acetylsalicylic acid; HR 0.18, P = .02 vs no thromboprophylaxis). Thrombotic complications were associated with increased mortality after initial palliation (HR 5.5, P < .001) and SCPC (HR 12.5, P < .001). Three patients experienced major bleeding complications without permanent sequelae (2 enoxaparin, 1 warfarin). CONCLUSIONS: Given the negative impact of thrombotic complications on survival, the low risk of serious bleeding complications, and the association between thromboprophylaxis and lowered thrombotic complication risk across all 3 palliative stages, routine use of thromboprophylaxis from the initial palliation to the early post-Fontan period in this population may be indicated.

Focused ultrasound robotic system for very small bore magnetic resonance imaging.

BACKGROUND: A magnetic resonance imaging (MRI) compatible robotic system for focused ultrasound was developed for small animal like mice or rats that fits into a 9.4 T MRI scanner (Bruker Biospec 9420, Bruker Biospin, Ettlingen, Germany). The robotic system includes two computer-controlled linear stages. MATERIALS AND METHODS: The robotic system was evaluated in a mouse-shaped, real-size agar-based mimicking material, which has similar acoustical properties as soft tissues. The agar content was 6% weight per volume (w/v), 4% w/v silica while the rest was degassed water. The transducer used has a diameter of 4 cm, operates with 2.6 MHz and focuses energy at 5 cm. RESULTS: The MRI compatibility of the robotic system was evaluated in a 9.4 T small animal scanner. The efficacy of the ultrasonic transducer was evaluated in the mimicking material using temperature measurements. CONCLUSIONS: The proposed robotic system can be utilized in a 9.4 T small animal MRI scanner. The proposed system is functional, compact and simple thus providing a useful tool for preclinical research in mice and rats.

Head-putter coordination patterns in expert and less skilled golfers.

The authors examined the patterns of expert and less skilled golfers in putting on an indoor surface to 1 of 3 circular targets (1, 3, and 5 m away) in trials with a ball present (and putted) or not present (a practice stroke). As expected, the experts performed better than the less skilled golfers on a large number of outcome and kinematic measures. Displacement and velocity profiles of the head and putter revealed high positive correlations for the less skilled golfers, indicating a dominant allocentric coordination pattern, but high negative correlations for the expert golfers, indicating a dominant egocentric coordination pattern. The observed coordination patterns did not interact with the distance of the intended putt or the presence/absence of a ball. These findings offer preliminary evidence that, although contrary to traditional beliefs, fundamental differences exist in putting coordination modes between expert and less skilled golfers.

Do Weekly Alerts From a Mobile Application Influence Reading During Residency?

BACKGROUND: The benefits of "spaced education" have been documented for residents in highly focused specialties. We found no published studies of spaced education in family medicine. In this study, we report on the feasibility of delivering weekly alerts from a mobile application (app) developed for exam preparation, to increase the reading of clinical information in the family medicine residency. DESIGN: This is a 2-phase mixed methods study. Phase one is a quasi-experimental study of resident reading of information related to priority topics in family medicine. Reading was documented by page views in a noncommercial mobile app. PARTICIPANTS: All incoming first-year residents at two university training programs in Canada. The intervention group received one alert per week to priority topics on the app, beginning in their second month of residency. The control group was given access to the same app, but received no alerts. RESULTS: In this paper, we report the phase one preliminary findings. In the intervention group, 81 of 96 first year residents consented. At the control site, 79 of 85 residents consented. After 100 days, intervention group residents had viewed more pages of clinical information across all 99 priority topics (1,546 versus 900) and per topic (15.7 versus 9.1 pages, P < 0.0003). On average, each increase of one visit to the app following a weekly alert was associated with an increase of 3.2 visits to pages of clinical information in the app. CONCLUSION: A weekly alert delivered via mobile app shows promise with respect to reading in the family medicine residency.

19F Oximetry with semifluorinated alkanes.

This work examines the variation of longitudinal relaxation rate R1(= 1/T1) of the 19F-CF3-resonance of semifluorinated alkanes (SFAs) with oxygen tension (pO2), temperature (T) and pH in vitro. Contrary to their related perfluorocarbons (PFCs), SFA are amphiphilic and facilitate stable emulsions, a prerequisite for clinical use. A linear relationship between R1 and pO2 was confirmed for the observed SFAs at different temperatures. Using a standard saturation recovery sequence, T1 has been successfully measured using fluorine 19F-MRI with a self-constructed birdcage resonator at 9.4 T. A calibration curve to calculate pO2 depending on T and R1 was found for each SFA used. In contrast to the commonly used PFC, SFAs are less sensitive to changes in pO2, but more sensitive to changes in temperature. The influence of pH to R1 was found to be negligible.

Stereotactic ultrasound for target volume definition in a patient with prostate cancer and bilateral total hip replacement.

PURPOSE: Target-volume definition for prostate cancer in patients with bilateral metal total hip replacements (THRs) is a challenge because of metal artifacts in the planning computed tomography (CT) scans. Magnetic resonance imaging (MRI) can be used for matching and prostate delineation; however, at a spatial and temporal distance from the planning CT, identical rectal and vesical filling is difficult to achieve. In addition, MRI may also be impaired by metal artifacts, even resulting in spatial image distortion. Here, we present a method to define prostate target volumes based on ultrasound images acquired during CT simulation and online-matched to the CT data set directly at the planning CT. METHODS AND MATERIALS: A 78-year-old patient with cT2cNxM0 prostate cancer with bilateral metal THRs was referred to external beam radiation therapy. T2-weighted MRI was performed on the day of the planning CT with preparation according to a protocol for reproducible bladder and rectal filling. The planning CT was obtained with the immediate acquisition of a 3-dimensional ultrasound data set with a dedicated stereotactic ultrasound system for online intermodality image matching referenced to the isocenter by ceiling-mounted infrared cameras. MRI (offline) and ultrasound images (online) were thus both matched to the CT images for planning. Daily image guided radiation therapy (IGRT) was performed with transabdominal ultrasound and compared with cone beam CT. RESULTS: Because of variations in bladder and rectal filling and metal-induced image distortion in MRI, soft-tissue-based matching of the MRI to CT was not sufficient for unequivocal prostate target definition. Ultrasound-based images could be matched, and prostate, seminal vesicles, and target volumes were reliably defined. Daily IGRT could be successfully completed with transabdominal ultrasound with good accordance between cone beam CT and ultrasound. CONCLUSIONS: For prostate cancer patients with bilateral THRs causing artifacts in planning CTs, ultrasound referenced to the isocenter of the CT simulator and acquired with intermodal online coregistration directly at the planning CT is a fast and easy method to reliably delineate the prostate and target volumes and for daily IGRT.

Effects of vision on head-putter coordination in golf.

Low-skill golfers coordinate the movements of their head and putter with an allocentric, isodirectional coupling, which is opposite to the allocentric, antidirectional coordination pattern used by experts (Lee, Ishikura, Kegel, Gonzalez, & Passmore, 2008). The present study investigated the effects of four vision conditions (full vision, no vision, target focus, and ball focus) on head-putter coupling in low-skill golfers. Performance in the absence of vision resulted in a level of high isodirectional coupling that was similar to the full vision condition. However, when instructed to focus on the target during the putt, or focus on the ball through a restricted viewing angle, low-skill golfers significantly decoupled the head--putter coordination pattern. However, outcome measures demonstrated that target focus resulted in poorer performance compared with the other visual conditions, thereby providing overall support for use of a ball focus strategy to enhance coordination and outcome performance. Focus of attention and reduced visual tracking were hypothesized as potential reasons for the decoupling.