Wide awake local anesthesia no tourniquet (WALANT) versus axillary brachial plexus block for carpal tunnel release in a French public university hospital: Care pathways and operating room costs.

INTRODUCTION: The wide awake local anesthesia no tourniquet (WALANT) is a local anesthetic technique that theoretically cuts costs and shortens surgical waiting times, but this has yet to be demonstrated in France. The main objective of this study was to assess and compare the comprehensive care pathways and costs of performing carpal tunnel release (CTR) procedures in the ambulatory surgery unit using WALANT and axillary brachial plexus block (ABPB). METHODS: A total of 72 CTRs in 66 patients were reviewed after a minimum follow-up of 6 months. The anesthesia was performed by an anesthesiologist after a preoperative consultation. The surgical waiting time, operating room occupancy time, total time taken off work (TOW) and the return to work rate were recorded. The estimated total direct cost per patient (TDCPP) was the sum of the specialist consultation fees, the French diagnosis-related group (DRG) rates and the minimum daily cost of TOW (€27.30/day). RESULTS: Only the total operating room occupancy time differed significantly: 27minutes for the WALANT versus 37minutes for the ABPB (p=0.004). There were no complications or reoperations in either group. The total cost for the cohort was estimated at €190,970. The mean estimated TDCPP was €2,870 for the entire cohort, €2,543 for the ABPB and €2,713 for the WALANT (p=0.791). Twenty-seven of the 45 patients returned to work after a mean TOW of 3.1 months. Fourteen CTRs were preceded by a mean preoperative TOW of 27 days, which resulted in a cost of €24,948 (13% of the total cost). There were no significant differences in TOW or revision rate between WALANT and ABPB. CONCLUSION: Although WALANT significantly reduced operating room occupancy times in our public hospital, the societal costs were the same regardless of the anesthesia technique. Reducing surgical waiting times in France could result in a theoretical saving of nearly €14 million annually. LEVEL OF EVIDENCE: IV.

Dosimetry and characterization of a 25-MeV proton beam line for preclinical radiobiology research.

PURPOSE: With the increase in proton therapy centers, there is a growing need to make progress in preclinical proton radiation biology to give accessible data to medical physicists and practicing radiation oncologists. METHODS: A cyclotron usually producing radioisotopes with a proton beam at an energy of about 25 MeV after acceleration, was used for radiobiology studies. Depleted silicon surface barrier detectors were used for the beam energy measurement. A complementary metal oxide semiconductor (CMOS) sensor and a plastic scintillator detector were used for fluence measurement, and compared to Geant4 and an in-house analytical dose modeling developed for this purpose. Also, from the energy measurement of each attenuated beam, the dose-averaged linear energy transfer (LETd ) was calculated with Geant4. RESULTS: The measured proton beam energy was 24.85 ± 0.14 MeV with an energy straggling of 127 ± 22 keV before scattering and extraction in air. The measured flatness was within ± 2.1% over 9 mm in diameter. A wide range of LETd is achievable: constant between the entrance and the exit of the cancer cell sample ranging from 2.2 to 8 keV/µm, beyond 20 keV/µm, and an average of 2-5 keV/µm in a scattering spread-out Bragg peak calculated for an example of a 6-mm-thick xenograft tumor. CONCLUSION: The dosimetry and the characterization of a 25-MeV proton beam line for preclinical radiobiology research was performed by measurements and modeling, demonstrating the feasibility of delivering a proton beam for preclinical in vivo and in vitro studies with LETd of clinical interest.

Analytical dose modeling for preclinical proton irradiation of millimetric targets.

PURPOSE: Due to the considerable development of proton radiotherapy, several proton platforms have emerged to irradiate small animals in order to study the biological effectiveness of proton radiation. A dedicated analytical treatment planning tool was developed in this study to accurately calculate the delivered dose given the specific constraints imposed by the small dimensions of the irradiated areas. METHODS: The treatment planning system (TPS) developed in this study is based on an analytical formulation of the Bragg peak and uses experimental range values of protons. The method was validated after comparison with experimental data from the literature and then compared to Monte Carlo simulations conducted using Geant4. Three examples of treatment planning, performed with phantoms made of water targets and bone-slab insert, were generated with the analytical formulation and Geant4. Each treatment planning was evaluated using dose-volume histograms and gamma index maps. RESULTS: We demonstrate the value of the analytical function for mouse irradiation, which requires a targeting accuracy of 0.1 mm. Using the appropriate database, the analytical modeling limits the errors caused by misestimating the stopping power. For example, 99% of a 1-mm tumor irradiated with a 24-MeV beam receives the prescribed dose. The analytical dose deviations from the prescribed dose remain within the dose tolerances stated by report 62 of the International Commission on Radiation Units and Measurements for all tested configurations. In addition, the gamma index maps show that the highly constrained targeting accuracy of 0.1 mm for mouse irradiation leads to a significant disagreement between Geant4 and the reference. This simulated treatment planning is nevertheless compatible with a targeting accuracy exceeding 0.2 mm, corresponding to rat and rabbit irradiations. CONCLUSION: Good dose accuracy for millimetric tumors is achieved with the analytical calculation used in this work. These volume sizes are typical in mouse models for radiation studies. Our results demonstrate that the choice of analytical rather than simulated treatment planning depends on the animal model under consideration.

A pencil beam approach to proton computed tomography.

PURPOSE: A new approach to proton computed tomography (pCT) is presented. In this approach, protons are not tracked one-by-one but a beam of particles is considered instead. The elements of the pCT reconstruction problem (residual energy and path) are redefined on the basis of this new approach. An analytical image reconstruction algorithm applicable to this scenario is also proposed. METHODS: The pencil beam (PB) and its propagation in matter were modeled by making use of the generalization of the Fermi-Eyges theory to account for multiple Coulomb scattering (MCS). This model was integrated into the pCT reconstruction problem, allowing the definition of the mean beam path concept similar to the most likely path (MLP) used in the single-particle approach. A numerical validation of the model was performed. The algorithm of filtered backprojection along MLPs was adapted to the beam-by-beam approach. The acquisition of a perfect proton scan was simulated and the data were used to reconstruct images of the relative stopping power of the phantom with the single-proton and beam-by-beam approaches. The resulting images were compared in a qualitative way. RESULTS: The parameters of the modeled PB (mean and spread) were compared to Monte Carlo results in order to validate the model. For a water target, good agreement was found for the mean value of the distributions. As far as the spread is concerned, depth-dependent discrepancies as large as 2%-3% were found. For a heterogeneous phantom, discrepancies in the distribution spread ranged from 6% to 8%. The image reconstructed with the beam-by-beam approach showed a high level of noise compared to the one reconstructed with the classical approach. CONCLUSIONS: The PB approach to proton imaging may allow technical challenges imposed by the current proton-by-proton method to be overcome. In this framework, an analytical algorithm is proposed. Further work will involve a detailed study of the performances and limitations of this approach in terms of image quality. The paper shows how to account for the MCS in the reconstruction step with this new approach when an analytical reconstruction algorithm is used.

Assessment of the axial rotation of the pelvis with the EOS® imaging system: intra- and inter-observer reproducibility and accuracy study.

PURPOSE: A source of radiological bias occurs when the axial rotation of the pelvis is disregarded in hip and spine biomechanics analyses. The EOS imaging system (EOS Imaging, France) offers the possibility of detecting and measuring the axial rotation of bones. Reproducibility and accuracy have not been documented in the case of the pelvis. METHODS: A dry pelvis has been X-rayed with the EOS system every 5° from 30° left to 30° right according to a laser line reference goniometer. Three observers have measured the rotation. One observer did it 3 times. The intra- and inter-observer reproducibility and the accuracy have been calculated using the root mean square standard deviation calculation. The relationship between the axial rotation and the offset between the left and right acetabulae on the lateral view was investigated. RESULTS: The 95 % CI was ±0.23° for the intra-observer and ±0.33° for the inter-observer reliability. The mean of signed differences between the software calculation and the actual axial rotation of the pelvis was -0.39° (SD 0.77°). The lateral acetabular offset was proportional to the sin of the rotation. Approximately, 30 mm offset corresponded to about 10° rotation. CONCLUSIONS: The 3D slot scanning imaging system demonstrated significant reproducibility and accuracy for the assessment of the axial rotation of the pelvis.

Three-dimensional assessment of the intervertebral kinematics after Mobi-C total disc replacement at the cervical spine in vivo using the EOS stereoradiography system.

BACKGROUND: Because 3-dimensional computed tomography and magnetic resonance imaging analysis of the spinal architecture is done with the patient in the supine position, stereoradiography may be more clinically relevant for the measurement of the relative displacements of the cervical vertebrae in vivo in the upright position. The innovative EOS stereoradiography system was used for measuring the relative angular displacements of the cervical vertebrae in a limited population to determine its feasibility. The precision and accuracy of the method were investigated. METHODS: In 9 patients with 16 Mobi-C prostheses (LDR Medical, Troyes, France) and 12 healthy subjects, EOS stereoradiography of the lower cervical spine (C3-7) was performed in the neutral upright position of the neck, flexion, extension, left and right lateral bending, and left and right axial rotation. The angular displacements were measured from the neutral position to every other posture. The random error was studied in terms of reproducibility. In addition, an in vitro protocol was performed in 6 specimens to investigate accuracy. RESULTS: The reproducibility and the accuracy variables varied similarly between 1.2° and 3.2° depending on the axis and direction of rotation under consideration. The Mobi-C group showed less mobility than the control group, whereas the pattern of coupling was similar. CONCLUSIONS: Overall, the feasibility of dynamic EOS stereoradiography was shown. The prosthesis replicates the pattern of motion of the normal cervical spine.

Clinical and biological assessment of cemented titanium femoral stems: an 11-year experience.

This study prospectively assessed the outcome of 134 cemented titanium stems and serum ion levels. The stems were polished (0.1 microm Ra) with circular cross section. At the end point, only one stem revision was performed for aseptic loosening, and two were planned due to subsidence greater than 5 mm. Non-progressive radiolucencies in zones 1 and 7 were observed in 16 hips at the cement-bone interface without osteolysis. Median serum titanium concentrations were below the detection limit (30 nmol/l) except in patients with failed stems. The overall stem survival rate was 97.7% at nine years, which is comparable to other series of cemented stems. The protective layer of titanium oxide coating the stem and a thick cement mantle may help resist aseptic loosening. In addition, satisfactory monitoring of the stem was reached using titanium serum level determination.