Spine Field Research Articles

Threat to Spine Field

Threat to Spine Field

Spine surgery and clinical research in Italy

In this fourth special issue dedicated to the Societa Italiana di Chirurgia Vertebrale, GIS, the so-called Italian Supplement of the European Spine Journal, the reader can find a short selection of the current surgical trends as well as of the spine-related research activities in Italy. The concept of research in the spine field is broad and the last decade has been testimony to worldwide significant efforts [1, 2] both in basic [3–5] and in clinical research activities [6–9], aimed at ultimately improving patients’ care. Indeed, either basic or clinical research has been fostered with the aim to arrive at clinically useful conclusions. Such strategy has been adopted by all major national and international spine societies. In Italy, like in many other countries, spine surgery is continuing to undergo profound changes, with the stable number of orthopedic spine surgery and that of spine neurosurgeons rising. This is not only a “social change” but, most importantly, a “cultural” one. Neurosurgeons are traditionally trained in microsurgical techniques and soft-tissue handling surgical procedures; however, they may lack a specific knowledge of bone biology and biomechanics, two cornerstones of spine surgery, which are well known to orthopedic surgeons. Such intrinsic differences may also be one of the causes influencing the apparently different clinical and surgical attitudes, i.e., spinal neurosurgeons being prone to adopt and boost minimally invasive techniques and computer-guided surgery, while orthopedic spine surgeons favoring more biological and biomechanical topics, like the sagittal balance. Indeed, this is only an apparent distinction, as it is always more common to find spine specialists harboring the different competencies [10]. The papers accepted for publication in this Supplement deal mostly with clinical research topics and span across all spinal topics (degenerative, deformity, trauma and tumor). A quick look at this volume’s index will make the reader aware of the significant attention dedicated by Italian spine surgeons to the sagittal balance topic and, in general, to the deformity field. The benefits and risks of contemporary techniques, like computer-guided and minimally invasive surgeries, particularly in trauma patients, have been analyzed in other papers. Studies dealing with surgical and radiological techniques used in cervical spine degenerative disease, focusing also on less common conditions, or in spinal tumor cases have been included as well. The basic research section of the Supplement hosts two interesting studies, which are just an example not only of the interest in basic research pursued by some of the main national spine centers, but also of the growing attention dedicated by younger researchers to such field, in particular to those topics related to the intervertebral disc degeneration and to stem cell-based therapies. Indeed, it is recent the establishment of an Italian spine basic research award, named BioSpina (http://www.biospina.com). Lastly, the presence in this Supplement of studies presented at 2012 GIS meeting by French spine surgeons or resulting from the scientific collaboration between Italian spine surgeons and other European colleagues is an example of the continuous cultural exchange, which will continue to positively influence the spine care activities in Italy and, at the same time, to make others aware of the Italian know-how.

SU‐E‐T‐599: A Dosimetric Comparison Between Multiple Junction Shifts and Single Gradient Dose Junction for Craniospinal Irradiation (CSI)

Purpose: To evaluate the impact of patient treatment setup errors on the dose distributions between multiple junction shifts and a single gradient dose junction for craniospinal irradiation (CSI). Methods: Conventionally, two lateral brain fields and a posterior spine field are used for CSI. A weekly 1cm shift of the field junction is used to reduce the hot/cold spots due to patient positioning errors. This study retrospectively investigates the use of a single gradient dose falloff junction between two lateral brain fields and a posterior spine field. These fields were extended to allow for minimum 3cm overlap at the brain and spine junction. The dose gradient at the junction is achieved using IMRT and planned using Eclipse System (v10) . Optimization was set to create a gradient dose falloff from each contributing field throughout the overlapped area. The impact of patient positioning setup errors on the dose distributions for both techniques were simulated by applying shifts of +/− 3 and 5mm. The resulting dose profiles across the field junction for both techniques were calculated and compared. For the conventional plan, the dose profiles were calculated over the sum of the fractionation to include the effects from the weekly 1cm shift. Results: Systematic positioning errors throughout the course of treatment resulted in comparable hot/cold spots for both the gradient (112.7%/85.7% 3mm; 116.2%/80.2% 5mm) and conventional (115.2%/84.1% 3mm; 119.2%/81.9% 5mm) techniques. In most cases, the gradient technique provided slightly better uniformity in dosimetry. A single fraction positioning error provided significantly larger hot/cold spots in the conventional technique compared to the gradient technique. Conclusion: The advantages of the single gradient dose junction technique include improved single fraction dose uniformity and one plan for the entire treatment course, which reduces the possibility of human error compared to delivering the conventional four shifted plans.

Comment on Moverley et al.: Impact factors of orthopaedic journals between 2000 and 2010: trends and comparisons with other surgical specialities

Dear Editor, I read with interest the article “Impact factors of orthopaedic journals between 2000 and 2010: trends and comparisons with other surgical specialties” by Moverley et al. [1]. I think that the article provides useful information about the trends of citations in the orthopaedic literature. However, there are some inaccuracies that are worthy of mention. First, the Journal of Orthopaedic Science is the official journal of the Japanese Orthopaedic Association, and it is published by Springer, so it should not be considered as “published in the US” as is shown in Table 1. Furthermore, the European Spine Journal cannot be considered as “published in the US” either (also shown in Table 1). In addition, the authors did not include the Journal of Spinal Disorders & Techniques among the specialist orthopaedic journals. Most orthopaedic surgeons would agree that the Journal of Spinal Disorders & Techniques is an important source of information for most orthopaedic surgeons working in the spine field, and certainly it should be considered an orthopaedic journal. Since the authors compared the impact factor of journals published in the USA to journals published in Europe, these flaws affect their results, and they could affect their conclusions. Sincerely, Dr. Julio Urrutia Chairman, Department of Orthopaedic Surgery School of Medicine, Pontificia Universidad Catolica de Chile

Commentary on Special Issue- Minimally Invasive Spine Surgery

Copyright: © 2014 Kuroki H. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Recently, Minimally Invasive Surgery (MIS) has been broadly employed in the spine field to decrease approach-related morbidity associated with conventional open surgery. This might minimize damage of paraspinal muscles, blood loss, risk of infection, postoperative pain, functional disturbance, and prolonged hospitalization. Hence, application of a MIS technique can be beneficial for the various spinal pathologies, especially in elderly or debilitated patients desired long spinal constructs.

When It Comes to Back Pain Causation, Has the Spine Field Missed the Forest for the Trees?

When It Comes to Back Pain Causation, Has the Spine Field Missed the Forest for the Trees?

Is It Time to Clean Up Spine Research? A Growing Controversy Pushes the Spine Field to a Tipping Point

The Back Letter: August 2011 - Volume 26 - Issue 8 - p 85,91-95 doi: 10.1097/01.BACK.0000403682.03737.a8

Conventional Craniospinal Irradiation with Patient Supine and Source-Skin Distance (SSD) 100 cm for Spinal Field

We describe a method of craniospinal irradiation (CSI) in the supine position and at a source-skin distance (SSD) of 100 cm for the spinal fields. The procedure is carried out with a 100-cm isocenter linear accelerator and conventional simulator, and the treatment is delivered with 2 opposed lateral cranial fields at source-axis distance (SAD) of 100 cm and 1 or 2 direct posterior spinal fields at SSD, 100 cm. The half beam–blocked cranial fields with a collimator rotation is used to match the superior border of the spinal field at the level of C2 vertebral body. The length of the spinal field is fixed, and is the same if 2 spinal fields are used. The position of the isocenter of the spine field is defined by longitudinally moving the couch a distance from the isocenter of the cranial fields and adjusting the SSD = 100 cm to the surface of the couch with the gantry rotated to the angle of 180° (posteroanterior position), and the distance can be calculated easily according to a few parameters. It only needs a simple calculation without couch rotation, extended SSD, or markers. The inferior and superior borders of the spinal field do not require visualization under fluoroscopy when it is beyond the visual field of the simulator. The entire simulation takes no more than 20 minutes. Supine craniospinal treatment using this technique may substitute the traditional prone position as a potentially beneficial alternative to CSI.

Allegations of Bias and Corruption Continue to Devil The Spine Field

Lippincott's Bone and Joint Newsletter 16(11):p 129, December 2010. | DOI: 10.1097/01.BONEJ.0000391520.41798.d1

Development of electric currents in a magnetic field configuration containing a magnetic null point

Context. In the past the role of magnetic null points in the generation of electric currents was investigated mainly in the close vicinity of the null, with perturbations being applied at nearby boundaries, or for a magnetic null configuration with a dome-shaped fan. In the solar atmosphere, however, electric currents are generated by perturbations originating at the photosphere, far away from coronal 3D nulls, and the occurence of magnetic nulls with a dome-shaped fan is apparently not common.Aims. We investigate the consequences of photospheric motion for the development of electric currents in a coronal magnetic field configuration containing a null, located far away from the boundaries, and the influence of topological structures on the spatial distribution of the currents.Methods. We use a 3D resistive MHD code to investigate the consequences of photospheric plasma motion for the generation of currents in a coronal magnetic field containing a null. The plasma is considered fully compressible and is initially in hydrostatic equilibrium. The initial magnetic field is potential (current free).Results. The photospheric plasma motion causes magnetic field perturbations that propagate to the corona along the field lines at the local Alfven speed. The Alfvenic wave perturbations correspond to a propagating current directed mainly parallel to the magnetic field. Perpendicular currents connect to return currents to close the current system. The magnetic perturbations eventually reach the vicinity of the null. However, the currents forming in and around the null, near the fan surface or near the spine field lines, are not always the strongest currents developing in the simulation box. In our simulation, the strongest currents develop close to the bottom boundary, where the plasma is moved, and below the null point, in a region where field line connectivity considerably changes. Conclusions. Our simulation shows that the presence of a magnetic null point does not necessarily mean that the strongest currents will form in or around the null, at the fan surface or at the spine. Our results indicate that regions of considerable change in field line connectivity are fundamental for the development of strong and thin current sheets. Regions of connectivity change are important because they combine perturbations that are generated at different locations on the Sun. Our results also suggest that it is more important how the perturbations are mapped and combined in regions of considerable connectivity change than what is the driver of the perturbations itself. The driver does not necessarily need to create strong currents where it is applied. However, when the perturbations produced by the driver combine in the regions of considerable connectivity change, they can increase the current in regions for which the length scale is much smaller than the characteristic length scale of the system. The location of regions of connectivity change, combined with the mapping of the perturbations to those regions, can be a useful tool to predict where and when solar flares will occur.

Allegations of Bias and Corruption Continue To Devil the Spine Field

The Back Letter: November 2010 - Volume 25 - Issue 11 - p 124 doi: 10.1097/01.BACK.0000390599.18146.d2

Supine Craniospinal Irradiation (SCI) in Medulloblastoma (MBL): Long-term Outcomes

Supine Craniospinal Irradiation (SCI) in Medulloblastoma (MBL): Long-term Outcomes

SU-GG-T-600: IMRT for Craniospinal Irradiation: A Comparison with Traditional Techniques

Purpose: This work tests the possibility of using IMRT to promote organ sparing for the treatment of CSI. The traditional CSI technique uses opposed lateral fields to treat the brain and posterior fields to treat the spine. Published manuscripts focusing on the possibility of IMRT for CSI have only looked at pediatric cases. Here, we will plan IMRT for CSI on adult patients to quantify the dosimetric gains when compared to traditional techniques. Method and Materials: Four patients treated at our institution were chosen and a traditional 3D plan along with an IMRT plan was computed for each patient. The planned dose was 10 Gy and only the spine fields were optimized. The traditional plan used a cervical and thoracic spine field at 100 SSD while the IMRT plan split these two fields into five isocentric fields. OAR and target volumes receiving certain doses were calculated for each plan. Results:IMRT resulted in greater target coverage, lower overall dose, and reduced OAR although the low dose was more spread out. The best target coverage was obtained on the single patient treated supine. For almost every OAR at each point, IMRT reduced the dose. Conclusion:IMRT for CSI has a dosimetric advantage in both target coverage and OAR sparing over traditional beam arrangements. To further this study, we plan on repeating this process for six more patients and we also want to examine if there is a benefit to optimize the cranial fields in the IMRT plan along with the spine fields. Although it results in a more time consuming process, we have shown that there is evidence to pursue IMRT for adult CSI.

Should the Spine Field Simply Get Rid of Its Least Effective and Most Wasteful Procedures?

Should the Spine Field Simply Get Rid of Its Least Effective and Most Wasteful Procedures?

Hybrid Forward and Inverse Planned IMRT for Cranio-spinal Axis Irradiation

To describe a technique for cranio-spinal irradiation (CSI) of patients in the supine position that is quicker to treat and more robust than conventional matching of static fields. CSI in the supine position improves patient comfort and simplifies pediatric anesthesia. In conventional CSI, lateral brain fields are matched to a posterior spine field. The couch and collimator settings of the brain fields are rotated to match the divergence of these fields to the upper spine field. When required, an additional lower spine field is matched at depth to the upper spine field. Patients are treated prone, as daily field alignment is performed by marking field borders on patients' skin. Radiation doses near match lines are extremely sensitive to misalignments, so junctions are moved several times through the course of treatment. In the hybrid technique, patients are treated supine. The inferior edges of the lateral brain fields and the superior edge of the lower posterior spine field are manually designed with long, smooth dose gradients by forward planned IMRT field-in-field (FIF) techniques. Additional FIF segments may be added to compensate for dose heterogeneities arising from spine curvature or lateral separation. The upper posterior spine field is inverse planned by the IMRT optimization algorithm of our planning system (Varian Eclipse) to match the pre-calculated gradients of the brain and lower spine fields. The resulting 4-field plan delivers very uniform dose to the cranio-spinal axis with no abrupt field junctions. kV imaging is used to localize the patient for treatment each day. Therapists enter the couch coordinates for the brain fields into a custom spreadsheet which calculates couch shifts for each of the spine fields, based on planned isocenters. Intra-fractional patient motion has been simulated by translating isocenters in the planning system, and dosimetric implications were compared to similar errors for conventionally planned static deliveries. Treatment of the hybrid IMRT plan is significantly simpler than conventional techniques, as geometric isocenter shifts are calculated automatically each day and couch and collimator rotations for brain fields are not required. Treatment planning is also simplified, as smooth field transitions obviate the need for match line shifts. In addition, delivery of hybrid IMRT plans is less susceptible to geometric inaccuracies. 1 mm misalignments of matched static fields can lead to dose errors of up to 40%. Because of the gradual transition between fields with the hybrid technique, 3 mm errors lead to dose errors of only 15%. The technique described here allows for quick, safe, and robust supine CSI.

How skeletons turn into quasi-separatrix layers in source models

Context. In situations where there are no magnetic null points located above a reference photospheric plane, and when the photospheric magnetic field is modeled by discrete flux concentrations, the magnetic connectivity is defined by the magnetic skeleton of the configuration. For a continuous distribution of non-zero photospheric flux, the connectivity is defined by quasi-separatrix layers (QSLs). Both the magnetic skeleton and QSLs can account for current sheet formation and dissipation. Observationally, though, only some portions of the skeleton are found to be related to flare ribbons, which are generally associated with QSL footpoints. Aims. In potential magnetic source models, a transition from the skeleton to QSLs has been shown to occur when the sources are displaced below the photospheric plane. The objective of this paper is to understand the topological and geometrical nature of this transition, and to derive rules to predict which parts of a given skeleton will give rise to QSLs. Methods. We consider magnetic configurations, derived from potential magnetic sources, which possess no coronal null points. We have calculated their skeletons, composed of null points, spine field lines and separatrix (fan) surfaces. Choosing a reference photospheric plane above the sources, we have calculated their QSL footprints. Results. As already known, the latter mostly match with subphotospheric spine field lines since, above these lines, field lines tend to diverge as a result of approaching a null and lying either side of the separatrix surface extending out of from this null. However, many non-spine related QSL footprints are also found, which we call branches. They correspond to the intersection with the photosphere of portions of fan field lines which “branch” away from the sources and result in QSLs due to the inclination of the coronal field lines. Conclusions. Our findings allow a better geometrical understanding of the relations between QSLs and skeletons. We show that in the absence of coronal null points, spines, as well as specific portions of fans as calculated in standard potential source models, are good predictors for the location of QSL footprints and of flare ribbons.

FAN–SPINE TOPOLOGY FORMATION THROUGH TWO-STEP RECONNECTION DRIVEN BY TWISTED FLUX EMERGENCE

We address the formation of 3D nullpoint topologies in the solar corona by combining Hinode/XRT observations of a small dynamic limb event, which occurred beside a non-erupting prominence cavity, with a 3D zero-beta MHD simulation. To this end, we model the boundary-driven kinematic emergence of a compact, intense, and uniformly twisted flux tube into a potential field arcade that overlies a weakly twisted coronal flux rope. The expansion of the emerging flux in the corona gives rise to the formation of a nullpoint at the interface of the emerging and the pre-existing fields. We unveil a two-step reconnection process at the nullpoint that eventually yields the formation of a broad 3D fan-spine configuration above the emerging bipole. The first reconnection involves emerging fields and a set of large-scale arcade field lines. It results in the launch of a torsional MHD wave that propagates along the arcades, and in the formation of a sheared loop system on one side of the emerging flux. The second reconnection occurs between these newly formed loops and remote arcade fields, and yields the formation of a second loop system on the opposite side of the emerging flux. The two loop systems collectively display an anenome pattern that is located below the fan surface. The flux that surrounds the inner spine field line of the nullpoint retains a fraction of the emerged twist, while the remaining twist is evacuated along the reconnected arcades. The nature and timing of the features which occur in the simulation do qualititatively reproduce those observed by XRT in the particular event studied in this paper. Moreover, the two-step reconnection process suggests a new consistent and generic model for the formation of anemone regions in the solar corona.

Craniospinal irradiation in the supine position: a dosimetric analysis.

Background: The prone has been considered a standard position for treatment in craniospinal irradiation (CSI). However, in some circumstances, it is unfeasible, necessitating a supine position. Objective: To analyze the distribution of radiation dose of CSI in the supine position, using a conventional technique, and to compare the radiation dose at the junction of cranial fields and upper spine field among different techniques. Materials and methods: Fifteen patients underwent computed tomography (CT) simulation in supine position for CSI. A total dose of 36 Gy was prescribed to the entire neuraxis. Treatment plan for conventional CSI (technique A; skin gap 10 mm without collimator-rotation of cranial fields) was calculated for median dose to the brain, spinal axis target volume, and normal organs. Three other techniques with collimator-rotation of whole brain fields (technique B, C, and D with skin gap of 2, 5, and 10 mm) were applied and compared for the radiation doses at the cervical junction. Results: Conventional CSI (Technique A) resulted in the median radiation dose (D50%) to the brain and spinal axis of 3,691 (2.5% overdose), and 3,812 cGy (6.0% overdose), respectively. The radiation doses to normal surrounding organs were within tolerable dose ranges. However, thyroid gland received substantial median dose, 2,725 cGy. Concerning the D50% at the cervical junction, techniques A, B, C, and D resulted in 107.7%, 112.9%, 103.1%, and 91.5% of the prescribed dose, respectively. The minimum radiation dose (D99%) were 3,285, 3,392, 3,275 and 2,994 cGy with techniques A, B, C, and D, while the maximum radiation dose (D1%) were 4,252, 4,556, 4,248, and 3,775 cGy, respectively. Conclusion: The supine position for CSI, using our conventional radiation technique, provided an acceptable median dose to the brain, spinal axis, and normal organs. Conventional CSI and technique C showed a better isodose distribution.

Comparison of the Dosimetry of Spinal Fields in Craniospinal Irradiation using Two Dimensional, Three Dimensional and Intensity Modulated Radiation Therapy Planning Techniques

Materials/Methods: The CT-based treatment planning was performed for the CSI volume using lateral cranial fields with a matched posterior single spine field. The prescription dose was 36 Gy to the CS axis delivered with 4 junction shifts. Target delineations were as follows: 2D plan field edge was placed 1 cm lateral to vertebral bodies; 3D plan had 1 cm expansion from the spinal canal for clinical target volume (CTV) for adults (0.5 cm for children) and an additional 0.7 cm to field edge for planning target volume (PTV). For IMRT plan, CTV was equal to PTV without additional expansion. To improve target coverage, a field in field technique was used for both 2D and 3D plans to act as compensators. The OAR evaluated included heart, thyroid, liver, lung, kidney, and small bowel. Dose volume histograms were used to assess the plans and time spent per plan was recorded. Results: The CT scans of 10 consecutive patients (4 pediatric and 6 adult) treated at our institution with CSI from 2004-2007 were selected. There was no statistical difference in PTV coverage when looking at the mean, minimum, maximum, and median doses andthepercentvolumecoveredby95%and107%ofthedose.MeandosetoOARwerealldecreasedwhencomparingIMRTto3D as follows: heart 11.3%, liver 12%, thyroid 2%, kidneys 22%, bowel 8% (p\0.05). Mean dose to OAR were all decreased when comparing 3D to 2D as follows: heart 5%, liver 13.5%, kidneys 31%, lungs 16.3% , bowel 28% (p\0.05). Total time spent planning (not including contouring) for each plan was approximately 4 hours per IMRT plan and 6-7 hours per 3D and 2D plans. Conclusions: Optimal treatment planning using either 2D or 3D plans with field in field technique results in similar PTV coverage when compared to IMRT plans. However, IMRT plans were superior to either 2D or 3D when looking at mean dose to most OAR. The IMRT planning took significantly less amount of time for treatment planning. These results make IMRT treatment planning more desirable in clinical practice. Author Disclosure: P.K. Parhar, None; C. Hitchen, None; T. Duckworth, None; K. DeWyngaert, None; A. Narayana, None.

SU‐GG‐J‐80: Effect of CT Truncation Artifacts to Proton Dose Calculation

Purpose: When a patient body part is out side of the CT scan field of view, truncation artifacts generally occur in the images leading to inaccuracy in the CT number (HU) in these affected images. In proton therapy treatment planning, CT numbers are converted to stopping powers to calculate dose, beam range and range compensators for the treatment fields to cover the target volumes. We have evaluated the effects of these artifacts on proton dose calculation accuracy and on range uncertainty for spinal fields used for cranial spinal irradiation. Method and Materials: A thoracic phantom was imaged on a GE 16 slice CT scanner using a standard body protocol. Two RMI bone tissue blocks simulating patient arm/or shoulder was placed outside of the scan field of view. Two sets of scans were obtained with and without the bone tissue blocks. Proton treatment plans were generated using Eclipse treatment planning system. Then, treatment plans were compared to each other to determine the dose and range differences. Results: There is an overall of 20–30 HU difference in the target area due to the image truncation artifacts. This creates a 2–3mm difference in the range of the proton beam at 50% dose line between the plans with and without truncation artifacts. Conclusion: The image artifacts cause uncertainty in dose estimations in the distal edge of the treatment target. The difference between the corrected plan and the truncated plan is on the order of 2–3mm, which is comparable to the distal margin normally used to account for the range uncertainty for the spine field proton therapy treatment planning.