Introduction of external magnetic fields in entropic moment modelling for radiotherapy

One of the big challenges of the emerging MRI-guided radiotherapy is the prediction of an external magnetic field effect on the deposited dose induced by a beam of charged particles. In this paper, we present the results of the implementation of the Lorentz force in the deterministic M1 model. The validation of our code is performed by comparisons with the Monte-Carlo code FLUKA. The relevant examples show a significant modification of the shape of dose deposition volume induced by the external magnetic field in presence of heterogeneities. A gamma-index analysis 3%/3mm shows a good agreement of our model with FLUKA simulations.

GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2

We describe the observation of GW170104, a gravitational-wave signal produced by the coalescence of a pair of stellar-mass black holes. The signal was measured on January 4, 2017 at 10∶11:58.6 UTC by the twin advanced detectors of the Laser Interferometer Gravitational-Wave Observatory during their second observing run, with a network signal-to-noise ratio of 13 and a false alarm rate less than 1 in 70 000 years. The inferred component black hole masses are 31.2_{-6.0}^{+8.4}M_{⊙} and 19.4_{-5.9}^{+5.3}M_{⊙} (at the 90% credible level). The black hole spins are best constrained through measurement of the effective inspiral spin parameter, a mass-weighted combination of the spin components perpendicular to the orbital plane, χ_{eff}=-0.12_{-0.30}^{+0.21}. This result implies that spin configurations with both component spins positively aligned with the orbital angular momentum are disfavored. The source luminosity distance is 880_{-390}^{+450}  Mpc corresponding to a redshift of z=0.18_{-0.07}^{+0.08}. We constrain the magnitude of modifications to the gravitational-wave dispersion relation and perform null tests of general relativity. Assuming that gravitons are dispersed in vacuum like massive particles, we bound the graviton mass to m_{g}≤7.7×10^{-23}  eV/c^{2}. In all cases, we find that GW170104 is consistent with general relativity.

Upper Limits on the Stochastic Gravitational-Wave Background from Advanced LIGO's First Observing Run

A wide variety of astrophysical and cosmological sources are expected to contribute to a stochastic gravitational-wave background. Following the observations of GW150914 and GW151226, the rate and mass of coalescing binary black holes appear to be greater than many previous expectations. As a result, the stochastic background from unresolved compact binary coalescences is expected to be particularly loud. We perform a search for the isotropic stochastic gravitational-wave background using data from Advanced Laser Interferometer Gravitational Wave Observatory's (aLIGO) first observing run. The data display no evidence of a stochastic gravitational-wave signal. We constrain the dimensionless energy density of gravitational waves to be Ω_{0}<1.7×10^{-7} with 95% confidence, assuming a flat energy density spectrum in the most sensitive part of the LIGO band (20-86 Hz). This is a factor of ∼33 times more sensitive than previous measurements. We also constrain arbitrary power-law spectra. Finally, we investigate the implications of this search for the background of binary black holes using an astrophysical model for the background.

Directional Limits on Persistent Gravitational Waves from Advanced LIGO's First Observing Run

We employ gravitational-wave radiometry to map the stochastic gravitational wave background expected from a variety of contributing mechanisms and test the assumption of isotropy using data from the Advanced Laser Interferometer Gravitational Wave Observatory's (aLIGO) first observing run. We also search for persistent gravitational waves from point sources with only minimal assumptions over the 20-1726 Hz frequency band. Finding no evidence of gravitational waves from either point sources or a stochastic background, we set limits at 90% confidence. For broadband point sources, we report upper limits on the gravitational wave energy flux per unit frequency in the range F_{α,Θ}(f)<(0.1-56)×10^{-8}    erg cm^{-2} s^{-1} Hz^{-1}(f/25  Hz)^{α-1} depending on the sky location Θ and the spectral power index α. For extended sources, we report upper limits on the fractional gravitational wave energy density required to close the Universe of Ω(f,Θ)<(0.39-7.6)×10^{-8}  sr^{-1}(f/25  Hz)^{α} depending on Θ and α. Directed searches for narrowband gravitational waves from astrophysically interesting objects (Scorpius X-1, Supernova 1987 A, and the Galactic Center) yield median frequency-dependent limits on strain amplitude of h_{0}<(6.7,5.5,  and  7.0)×10^{-25}, respectively, at the most sensitive detector frequencies between 130-175 Hz. This represents a mean improvement of a factor of 2 across the band compared to previous searches of this kind for these sky locations, considering the different quantities of strain constrained in each case.

Posterior arch C-1 screw technique: a cadaveric comparison study

OBJECTIVE

Posterior atlantoaxial stabilization and fusion using C-1 lateral mass screw fixation has become commonly used in the treatment of instability and for reconstructive indications since its introduction by Goel and Laheri in 1994 and modification by Harms in 2001. Placement of such lateral mass screws can be challenging because of the proximity to the spinal cord, vertebral artery, an extensive venous plexus, and the C-2 nerve root, which overlies the designated starting point on the posterior center of the lateral mass. An alternative posterior access point starting on the posterior arch of C-1 could provide a C-2 nerve root–sparing starting point for screw placement, with the potential benefit of greater directional control and simpler trajectory. The authors present a cadaveric study comparing an alternative strategy (i.e., a C-1 screw with a posterior arch starting point) to the conventional strategy (i.e., using the lower lateral mass entry site), specifically assessing the safety of screw placement to preserve the C-2 nerve root.

METHODS

Five US-trained spine fellows instrumented 17 fresh human cadaveric heads using the Goel/Harms C-1 lateral mass (GHLM) technique on the left and the posterior arch lateral mass (PALM) technique on the right, under fluoroscopic guidance. After screw placement, a CT scan was obtained on each specimen to assess for radiographic screw placement accuracy. Four faculty spine surgeons, blinded to the surgeon who instrumented the cadaver, independently graded the quality of screw placement using a modified Upendra classification.

RESULTS

Of the 17 specimens, the C-2 nerve root was anatomically impinged in 13 (76.5%) of the specimens. The GHLM technique was graded Type 1 or 2, which is considered “acceptable,” in 12 specimens (70.6%), and graded Type 3 or 4 (“unacceptable”) in 5 specimens (29.4%). In contrast, the PALM technique had 17 (100%) of 17 graded Type 1 or 2 (p = 0.015). There were no vertebral artery injuries found in either technique. All screw violations occurred in the medial direction.

CONCLUSIONS

The PALM technique showed statistically fewer medial penetrations than the GHLM technique in this study. The reason for this is not clear, but may stem from a more angulated ”up-and-in” screw direction necessary with a lower starting point.

Subdural Thoracolumbar Spine Hematoma after Spinal Anesthesia: A Rare Occurrence and Literature Review of Spinal Hematomas after Spinal Anesthesia

Spinal hematomas are a rare but serious complication of spinal epidural anesthesia and are typically seen in the epidural space; however, they have been documented in the subdural space. Spinal subdural hematomas likely exist within a traumatically induced space within the dural border cell layer, rather than an anatomical subdural space. Spinal subdural hematomas present a dangerous clinical situation as they have the potential to cause significant compression of neural elements and can be easily mistaken for spinal epidural hematomas. Ultrasound can be an effective modality to diagnose subdural hematoma when no epidural blood is visualized. We have reviewed the literature and present a full literature review and a case presentation of an 82-year-old male who developed a thoracolumbar spinal subdural hematoma after spinal epidural anesthesia. Anticoagulant therapy is an important predisposing risk factor for spinal epidural hematomas and likely also predispose to spinal subdural hematomas. It is important to consider spinal subdural hematomas in addition to spinal epidural hematomas in patients who develop weakness after spinal epidural anesthesia, especially in patients who have received anticoagulation.

Cross-cultural validity of the German version of the Pediatric Evaluation of Disability Inventory (PEDI-G)-a Rasch model application

AIM

The aim of this study was to evaluate the cross-cultural validity of the German version of the Pediatric Evaluation of Disability Inventory (PEDI-G) when used in Austria, Germany and Switzerland.

METHOD

A total of 118 girls and 144 boys participated in this study; 198 of the children (75.6%) had a developmental disability and 64 (24.4%) were without a known disability. The mean age was four years (range 11 months to 10 years and six months, SD 1.91). Item goodness of fit, differential item functioning (DIF) and differential test functioning (DTF) were evaluated by use of a Rasch model.

RESULTS

Twenty-four (11.6%) out of 206 items of the Functional Skills Scale and one (5%) out of 20 items of the Caregiver Assistance Scale demonstrated misfit according to the Rasch model. Thirty-four (16.5%) out of 206 items of the Functional Skills Scale and no item from the Caregiver Assistance Scale demonstrated DIF. Almost half (46%) of the items demonstrating misfit also demonstrated DIF, indicating an association between them. The DIF by country only demonstrated a minimal impact on the person measures of the PEDI-G.

INTERPRETATION

Even though some items did not meet the statistical and clinical criteria set, the PEDI-G can be used, on a preliminary basis as a valid tool to measure activities of daily living of children with and without a disability in these countries. Further larger studies are needed to evaluate more psychometric item properties of the PEDI-G in relation to context.

[Infant respiratory distress revealing Jeune syndrome]

Jeune syndrome (asphyxiating thoracic dystrophy) is a rare autosomal recessive osteochondrodysplasia with a variable degree of severity, clinically characterized by respiratory distress with a narrow chest and limb shortness. The reported incidence is one to five in 500,000 live births. Most patients develop severe respiratory failure during the first 2 years of life, leading to death in 60-80 % of cases. Survivors may suffer from renal, hepatic, or pancreatic complications. Expanding thoracic surgery can be used for severe cases. We describe the case of an 18-month-old boy who developed mild respiratory distress. The patient showed typical radiological features of Jeune syndrome: narrow thorax with short ribs and trident appearance of the pelvis. This case underscores the value of the right interpretation of the chest radiograph of the infant with a respiratory distress syndrome.

Herpes Simplex Encephalitis of the Parietal Lobe: A Rare Presentation

A 69-year-old female with a history of breast cancer and hypertension presented with a rare case of herpes simplex encephalitis (HSE) isolated to her left parietal lobe. The patient's first biopsy was negative for herpes simplex virus (HSV) I/II antigens, but less than two weeks later, the patient tested positive on repeat biopsy. This initial failure to detect the virus and the similarities between HSE and symptoms of intracranial hemorrhage (ICH) suggests repeat testing for HSV in the presence of ICH. Due to the frequency of patients with extra temporal HSE, a diagnosis of HSE should be more readily considered, particularly when a patient may not be improving and a concrete diagnosis has not been solidified.

Venous air embolus during prone cervical spine fusion: case report

Venous air embolism (VAE) is a known neurosurgical complication classically and most frequently occurring in patients undergoing posterior cranial fossa or cervical spine surgery in a sitting or semi-sitting position. The authors present a case of VAE that occurred during posterior cervical spine surgery in a patient in the prone position, a rare intraoperative complication. The patient was a 65-year-old man who was undergoing a C1-2 fusion for a nonunion of a Type II dens fracture and developed a VAE. While VAE in the prone position is uncommon, it is a neurosurgical complication that may have significant clinical implications both intraoperatively and postoperatively. The aim of this review is 2-fold: 1) to improve the general knowledge of this complication among surgeons and anesthesiologists who may not otherwise suspect air embolism in patients positioned prone for posterior cervical spine operations, and 2) to formulate preventive measures as well as a plan for prompt diagnosis and treatment should this complication occur.

Lateral Thoracic Osteoplastic Rib-Sparing Technique Used for Lateral Spine Surgery: Technical Note

Of patients who have undergone lateral approaches to the thoracic spine, surgical site postoperative pain appears to be greater among those who have undergone transection and removal of a rib segment than those who have not. Therefore, techniques that conserve anatomical position and minimize tissue disruption would theoretically result in less pain and a quicker recovery. Herein, we describe a rib-sparing osteoplastic technique used when rib segments need to be displaced in order to create an unobscured corridor to the operative target. Our approach minimizes soft tissue disruption and restores the anatomical function of the rib. Based on our experience, these patients report less pain, mobilize earlier, and are discharged sooner than those who have had rib segments sacrificed as part of a lateral approach to the spine.

Alterations in chromosomal synapses and DNA repair in apoptotic spermatocytes of Mus m. domesticus

We investigated whether apoptotic spermatocytes from the mouse Mus m. domesticus presented alterations in chromosomal synapses and DNA repair. To enrich for apoptotic spermatocytes, the scrotum's temperature was raised by partially exposing animals for 15 min to a 42ºC water bath. Spermatocytes in initial apoptosis were identified in situ by detecting activated Caspase-9.  SYCP1 and SYCP3 were markers for evaluating synapses or the structure of synaptonemal complexes and Rad51 and γH2AX for detecting DNA repair and chromatin remodeling. Apoptotic spermatocytes were concentrated in spermatogenic cycle stages III-IV (50.3%), XI-XII (44.1%) and IX-X (4.2%). Among apoptotic spermatocytes, 48% were in middle pachytene, 44% in metaphase and 6% in diplotene. Moreover, apoptotic spermatocytes showed several structural anomalies in autosomal bivalents, including splitting of chromosomal axes and partial asynapses between homologous chromosomes. gH2AX and Rad51 were atypically distributed during pachytene and as late as diplotene and associated with asynaptic chromatin, single chromosome axes or discontinuous chromosome axes. Among apoptotic spermatocytes at pachytene, 70% showed changes in the structure of synapses, 67% showed changes in gH2AX and Rad51 distribution and 50% shared alterations in both synapses and DNA repair. Our results showed that apoptotic spermatocytes from Mus m. domesticus contain a high frequency of alterations in chromosomal synapses and in the recruitment and distribution of DNA repair proteins. Together, these observations suggest that these alterations may have been detected by meiotic checkpoints triggering apoptosis.

Unilateral Laminotomy with Bilateral Spinal Canal Decompression for Lumbar Stenosis: A Technical Note

Lumbar stenosis has become one of the most common spinal pathologies and one that results in neurogenic claudication, back and leg pain, and disability. The standard procedure is still an open laminectomy, which involves wide muscle retraction and extensive removal of the posterior spinal structures. This can lead to instability and the need for additional spinal fusion. We present a systemized and detailed approach to unilateral laminotomy for bilateral decompression, which we believe is superior to the standard open laminectomy in terms of intraoperative visualization, postoperative stability, and degree of invasiveness.

Dural-Based Cavernoma of the Posterior Cranial Fossa Mimicking a Meningioma: A Case Report

Cavernous angiomas usually occur in the parenchyma of both the supra and infratentorial compartments. At times, they can both clinically and radiologically mimic other dural-based lesions. We present a case of a patient with chronic occipital headaches, initially thought to have a meningioma, but proven to be a cavernoma with histological analysis.

Training Medical Novices in Spinal Microsurgery: Does the Modality Matter? A Pilot Study Comparing Traditional Microscopic Surgery and a Novel Robotic Optoelectronic Visualization Tool

The operative microscope has been a staple instrument in the neurosurgical operating room over the last 50 years. With advances in optoelectronics, options such as robotically controlled high magnification have become available. Such robotically controlled optoelectronic systems may offer new opportunities in surgical technique and teaching. However, traditionally trained surgeons may find it hard to accept newer technologies due to an inherent bias emerging from their previous background. We, therefore, studied how a medically naïve population in a pilot study would meet set microsurgical goals in a cadaver experiment using either a conventional operative microscope or BrightMatter™ Servo system, ​a robotically controlled optoelectronic system (Synaptive Medical, Toronto, Ontario, Canada). We found that the relative ease in teaching medical novices with a robotically controlled optoelectronic system was more valuable when compared to using a modern-day surgical microscope.

Bullet Fragment of the Lumbar Spine: The Decision Is More Important Than the Incision

Study Design Case report. Objective Treatment of gunshot wounds to the spine is a topic of continued discussion and controversy. The following case study provides a description of a patient with a gunshot wound to the lumbar spine with a retained bullet in the intrathecal space. Methods Immediately after gunshot injury, a patient developed lumbar and radicular pain, as well as neurologic deficits. He was taken for surgery to remove the retained bullet. Results Following surgery, pain and neurologic function improved. The operative techniques and the postoperative clinical management are discussed in this report. Conclusion In our opinion, it was necessary to remove the bullet to avoid migration and possible worsening of neurologic function. However, surgical intervention is not appropriate in every case, and ultimately decisions should be based on patient presentation, symptomology, and imaging.

Technical Note - Lateral Approach to the Lumbar Spine for the Removal of Interbody Cages

Revision surgery to address the migration or fracture of a lumbar interbody cage can be technically challenging. Scar tissue and fibrosis, among other anatomic barriers, can make removal of the cage a complicated procedure, potentially increasing postoperative pain as well as the probability of neurologic deficits. Use of the lateral surgical technique for removal of the cage can avoid these potential complications. In this case report, we describe the removal of interbody cages through a lateral approach in three patients without the necessity of additional posterior hardware revision.

Differences in activities of daily living (ADL) abilities of children across world regions: a validity study of the assessment of motor and process skills

BACKGROUND

One important goal of paediatric occupational therapy services is to improve activities of daily living (ADL) abilities of children. In order to plan and evaluate the effectiveness of targeted interventions, valid assessments are critically needed. The Assessment of Motor and Process Skills (AMPS) is an internationally standardized assessment of ADL performance that has not been validated for use with children in Middle Europe.

AIM

To evaluate for (i) significant differences in mean ADL motor and mean ADL process ability measures among children from Middle Europe compared with children from North America, UK/Republic of Ireland, Nordic countries, Western Europe, Australia/New Zealand and Asia; and (ii) meaningful differences between the international age-normative means of the AMPS and those for children from Middle Europe.

METHOD

We analysed data of children across world regions extracted from the international AMPS database using many-facet Rasch and two-way anova analyses and by estimating contrasts to evaluate for significant group differences.

RESULTS

anova analyses of data for 11 189 children ages 2-15 revealed significant effects for mean ADL motor and ADL process ability by region [F ≥ 15.32, d.f. = (6, 11 091), MSE ≥ 0.20, P < 0.001, ή(2) ≥ 0.008], and age [F ≥ 253.47, d.f. = (13, 11 091), MSE ≥ 0.20, P < 0.001, ή(2) ≥ 0.229], and a significant interaction effect for mean ADL process ability [F = 1.48, d.f. = (78, 11 091), P = 0.004, ή(2) = 0.010]. Out of 168 estimated contrasts between Middle Europe and the other world regions for mean ADL motor and ADL process ability, seven were statistically significant (4.17%), but none exceeded ±1SE from the international means.

CONCLUSION

The AMPS remains free of relevant differences in mean ADL ability measures between Middle Europe and other world regions, indicating that the international age-normative mean values are likely to be applicable to children from Middle Europe. The AMPS can be used internationally to evaluate ADL performance in children and to determine if the child is eligible for occupational therapy services.