Determinants of shuttle run performance in the prediction of peak VO2 in wheelchair users

Purpose. The purpose of this study was to determine the impact of ergonomic and environmental variations on indoor shuttle run (SR) performance in wheelchair sportsmen.

Methods. Eleven experienced male wheelchair sportsmen performed three 25-m SRs in random order with varying turning capacity (TC) and mechanical resistance (MR): condition NN where participants used their sports wheelchair on a tartan surface, condition RN with increased MR, and condition RD with limited TC. Metabolic data were continuously recorded using a portable K4b² system.

Results. Friedman ANOVA with Wilcoxon a posteriori testing indicated similar VO_2peak values in all three tests. SR performance, however, was significantly different across the three test conditions (NN: 536.18 ± 119.09 s; RN: 488.82 ± 119.84 s; RD: 404.91 ± 88.41 s). SR performance contributed for 28% of the explained variance of the measured VO_2peak. The addition of TC or MR or both increased the explained variance to 32, 38 and 41%, respectively.

Conclusions. These findings demonstrate a significant impact of variations in floor surface and wheelchair-user interface on SR performance. The findings also suggest that strong reservations have to be made regarding the validity of a SR test, as predictor of VO_2peak in a wheelchair user population.     

Targeted non-covalent self-assembled nanoparticles based on human serum albumin

Human serum albumin (HSA) is a biological nanocarrier that forms non-covalent complexes with a number of synthetic and biomolecules. Previously we demonstrated radiolabeled HSA-based nanoparticles can form non-covalent complexes with fluorescent cyanine dyes yielding imaging agents for surgical guidance towards tumor draining lymph nodes. Here the self-assembly approach enabled rapid clinical translation. Based on this experience we reasoned it would be interesting to expand this non-covalent technology to a targeted approach. Therefore, the ability of HSA to form non-covalent self-assembled complexes with peptides via near-infrared (NIR) cyanine dyes was explored. Föster resonance energy transfer (FRET) quenching interactions between HSA-Cy5 and the non-covalently bound fluorescent molecules indocyanine green (ICG), IR783-CO₂H and three IR783-labeled targeting peptides were used to monitor complex assembly and disassembly. The host-guest interactions between HSA and IR783-labeled peptides enabled the formation of (bio)nanoparticles that are coated with peptides, which may target α_vβ₃-integrins, the chemokine receptor 4 (CXCR4), or somatostatin receptors. The potential of CXCR4-targeted (bio)nanoparticles in sentinel lymph node procedures is demonstrated in vivo. By non-covalently binding NIR-dye labeled peptides to an already clinically approved HSA-scaffold, we have readily formed targeted bionanoparticles.     

Does on-site urine toxicology screening have an added diagnostic value in psychiatric referrals in an emergency setting?

Objective

The objective was to examine the added diagnostic value of on-site urine toxicology screening (UTS) in the routine assessment of psychiatric patients in an urban emergency setting.

Method

A naturalistic two-step prospective cohort study design was used enrolling all emergency room (ER) patients referred for psychiatric consultation. In two consecutive cohorts, diagnosis of drug use was assessed based on routine psychiatric interview without (n=64) and with on-site UTS (ACON) (n=56). In both cohorts, drug use was also assessed by post hoc laboratory-based urine immunoassay (Triage) as the gold standard.

Results

Sensitivity and specificity of diagnosis of drug use based on psychiatric interview only varied (0.75 and 1 in the interview-based cohort; 0.5 and 0.75 in the interview+on-site UTS cohort). The sensitivity and specificity of on-site UTS were 0.93 and 0.97.

Conclusions

In an ER setting, the validity of the diagnosis of drug abuse exclusively based on psychiatric interview is low. The use of on-site UTS provides accurate data on drug use and is more practical as compared to post hoc laboratory assessment. On-site UTS has an added diagnostic value of drug use with high sensitivity and specificity.     

Evaluation of the clinical usefulness for using verification images during frameless radiosurgery

Our previous studies showed that intrafraction motion needs to be corrected for in frameless radiosurgery. This study was designed to evaluate if verification images can correct for mechanical inaccuracy and intrafraction motion. With proper immobilization and verification images on a regular basis during treatment, mechanical (table-) inaccuracies and intrafraction motion can be corrected for and the absence of PTV-margins warranted.     

Improving the intra-fraction update efficiency of a correlation model used for internal motion estimation during real-time tumor tracking for SBRT patients: Fast update or no update?

Background and purpose

For tumor tracking, a correlation model is used to estimate internal tumor position based on external surrogate motion. When patients experience an internal/external surrogate drift, an update of the correlation model is required to continue tumor tracking. In this study, the accuracy of the internal tumor position estimation for both the clinical available update at discrete points in time (rebuild) and an in-house developed non-clinical online update approach was investigated.

Methods

A dynamic phantom with superimposed baseline drifts and 14 SBRT patients, treated with real-time tumor tracking (RTTT) on the Vero system, were retrospectively simulated for three update scenarios, respectively no update, clinical rebuild and 0.5 Hz automated online update of the correlation model. By comparing the target positions based on 0.5 Hz verification X-ray images with the estimated internal tumor positions regarding all three update scenarios, 95th percentile modeling errors (ME₉₅), incidences of full geometrical coverage of the CTV by a 5 mm extended PTV (P_5mm) and population-based PTV margins were calculated. Further, the treatment time reduction was estimated when switching from the clinical rebuild approach to the online correlation model update.

Results

For dynamic phantom motion with baseline drifts up to 0.4 mm/min, a 0.5 Hz intra-fraction update showed a similar accuracy in terms of ME₉₅ and P_5mm compared to clinical rebuild. For SBRT patients treated on Vero with RTTT, accuracy was improved by 0.5 Hz online update compared to the clinical rebuild protocol, yielding smaller PTV margins (from 3.2 mm to 2.7 mm), reduced ME_95,3D (from 4.1 mm to 3.4 mm) and an increased 5th percentile P_5mm (from 90.7% to 96.1%) for the entire patient group. Further, 80% of treatment sessions were reduced in time with on average 5.5 ± 4.1 (1 SD) min.

Conclusion

With a fast (0.5 Hz) automated online update of the correlation model, an efficient RTTT workflow with improved geometrical accuracy was obtained.